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334 Cards in this Set
- Front
- Back
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Bioenergetics vs. Metabolism?
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bioenergetics = how we use energy
metabolism = rxns involved |
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Catabolism vs. anabolism?
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catabolism = breakdown
anabolism = build-up |
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3 examples of energy containing nutrients that may be broken down by catabolism?
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1. carbohydrates
2. fats 3. proteins |
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What are metabolites?
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metabolic intermediates
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4 examples of cell macromolecules produced by anabolism?
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1. proteins
2. polysacch.s 3. lipids 4. nucleic acids |
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3 examples of energy depleted end products of catabolism?
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1. CO2
2. H2O 3. NH3 |
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4 examples of precursor molecules that may be "built up" thru anabolism?
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1. AAs
2. sugars 3. fatty acids 4. nitrogenous bases |
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4 examples of how chemical energy may be stored?
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1. ATP
2. NADH 3. NADPH 4. FADH2 |
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Catabolism and Anabolism are often related to one another in what way?
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they are often just the reverse of eachother
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Catabolism and anabolism are often just the reverse of one another except for what distinction?
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At least one step is catalyzed by different enzymes for different directions...this helps control the flow of molecules
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In catabolism and anabolism one step is often what?
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thermodynamically greatly favored in one direction
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The two processes of anabolism and catabolism often take place where?
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in two different parts of the cell
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Name 3 general types of metabolic pathways?
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1. converging catabolism
2. diverging anabolism 3. cyclic pathway |
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Describe the common distinguishing feature of converging catabolism.
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often converge on one common intermediate
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Describe the common distinguishing feature of diverging anabolism?
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they often begin with a common intermediate
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Give two examples of cyclic pathways?
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1. kreb's cycle
2. citric acid cycle |
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The distinguishing factor of cyclic pathways?
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you end up back where you began...sometimes can derive more energy this way
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5 biochmical rxn classes?
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1. oxidation-reduction
2. make/break C bonds 3. internal rearrangements, isomerizations and eliminations 4. group transfer rxns 5. free radical rxns |
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What occurs in redox rxns?
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electrons move around (oxidation = loss of e)
(reduction = gain of e) |
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3 methods of regulation of chm rxns?
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1. substrate concentration
2. allosteric regulation (eg feedback) 3. external factors (eg hormones) |
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The first law of thermodynamics?
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total amt of energy in the universe is constant, but forms change
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The second law of thermodynamics?
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in natural processes, entropy tends to increase (everything moves toward randomness)
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Define G.
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Gibbs free energy = energy capable of doing work at constant temp and pressure
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Define H.
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enthalpy = heat content
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Define S.
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entropy = randomness
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gibb's free energy eqn?
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^G = ^H - T^S
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A negative ^G indicates what?
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a favorable rxn that goes towards products
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A positive delta G indicates what?
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unfavorable rxns that goes towards reactants
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Equilibrium does not mean what?
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it does not indicate a state where there are equal concentrations of all reactants and products
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What is equilibrium? How is it related to ^G'"
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the state where concentrations remain constant...the concentrations HAVE to be determined experimentally...then an equilbrium constant can be calculated, and from this ^G'" can be calculated
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How much energy is transferred in a pair of rxns?
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ordinarily, less than 100% of the released energy is transferred (so some is released as heat)
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What do enzymes change?
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they change rates, not ^G
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Standard ^G's are what?
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Additive
ex) A--->B (^G1) B--->C (^G2) sum = A--->C (^G1+^G2) |
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What is ATP a key link between?
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catabolism and anabolism
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Is hydrolysis favorable? How do we know?
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it is very favorable...it has a large, negative ^G
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How fast is hydrolysis?
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it is very slow...thus it requires enzymatic catalysis
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What is the ^G'" for ATP hydrolysis?
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-30.5 kj/mol
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Is the ^G'" for the hydolysis of ATP considered large?
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yes (-30.5 kj/mol)
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What is larger for the ATP hydrolysis, ^G'" or ^G?
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when you take into consideration the actual conc.s of reactants and products in the cells, the ^G is larger (about double, about -60 kj/mol)
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What does the ^G (not the ^G'") of ATP hydrolysis do from cell to cell?
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varies depending upon concentrations
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Besides ATP name 3 other key phos. intermediates? (give ^G'" values)
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1. phosphoenolpyruvate (PEP)(-61.9 kj/mol)
2. 1,3 biphosphoglycerate (-49.3 kj/mol) 3. phosphocreatine (-43.0 kj/mol) ALL ARE MORE NEGATIVE THAN THE HYDROLYSIS OF ATP ALL ARE CAPABLE OF RELEASING A LOT OF ENERGY |
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What are thioesters?
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another class of intermediates
ex. "Acetyl-coenzyme A" (an important molecule...about -30kj/mol ^G'") |
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What is a key link between catabolism and anabolism?
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ATP
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OFTEN it is not just hydrolysis involved with ATP (or GTP) hydrolysis...but what else?
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a group transfer (so a two step process...however in some cases the ATP or GTP may be directly hydrolyzed (such as in muscle mvmt)
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Acetyl CoA's ^G'" is close what?
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the ^G'" for ATP
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Name three phosphate compounds with a ^G'" greater than ATP and Acetyl CoA?
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1. phosphoenolpyruvate
2. 1,3 Biphosphoglycerate 3. phosphocreatine (however all of these...incl. ATP and acetyl CoA are considered high energy compounds...over -25 kj/mol) |
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Is ATP considered stable?
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yes...very stable
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List the three most common ways to split (hydrolyze) ATP? Which is the most common? Which are the most important?
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1. to yield ADP + phosphoryl group
2. to yield AMP + pyrophosphoryl group 3. to yield pyrophosphate(PPi) + adenylyl group 2 and 3 look alike but 3 is most common 1 and 3 are most important |
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What can occur following the hydrolysis of ATP that yields pyrophosphate (PPi) + adenylyl group?
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this can be followed by the pyrophosphate (PPi) being hydrolyzed to yield 2 Pi (which almost DOUBLES the energy yield)
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The ATP hydrolysis that yields ADP + phosphoryl group is aka ? attack.
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gamma (attacks + chg center)
this is the most common way to hydrolyze ATP breaks beta-gamma bond |
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The ATP hydrolysis that yields AMP + pyrophosphoryl group
is aka ? attack. |
beta (breaks alpha-beta bond)
...does not occur frequently ...pyrophosphoro group attached to some other group |
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The ATP hydrolysis rxn that yields pyrophosphate(PPi) + adenylyl group is aka ? attack.
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alpha attack
...breaks alpha-beta bond |
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Discuss fatty acid activation?
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ex. palmitate (an FA)
...adenylyl is transferred to the FA and PPi is released (-46kj/mol)...can become 2 Pi, even more exergonic, 2 high energy bonds broken in the process ...adenylyl is subsequently replaced by coenzyme a |
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Name 2 other ATP driven rxns?
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1. active transport (Na+ and K+)
2. muscle movement |
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Name 3 phosphoryl group transfers?
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1. from atp to various NDPs
2. to reduce [ADP] when it becomes too high 3. from creatine phosphate (phosphocreatine) |
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What is an NDP?
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any other phosphate...whether oxy or deoxy
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When a phosphoro gr. transfer is from ATP to NDP what is the ^G'".
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about 0
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illustrate the phospho group transfer from ATP to NDP.
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ATP + NDP (or dNDP) <---> ADP + NTP (or dNTP)
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illustrate the phospho group transfer to reduce [ADP] when it becomes too high? what is the ^G'"
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2ADP <---> ATP + AMP
1 ADP transfer phospho group to other one (^G'" is again about 0) |
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Describe phospho group transfer from creatine phosphate (phosphocreatine)?
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-a ready source of phosphoryl groups for QUICK synthesis of ATP (phosphocreatine is later replenished by phosphoryl transfer from ATP)
ADP + PCr <---> ATP + Cr (PCr has very high energy) ^G'" is about -12.5 kj/mol (so exergonic) |
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Describe a biological oxidation-reduction?
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one compound is oxidized, losing/releasing electrons; another compound is reduced, gaining electrons
[LEO GER or OIL RIG] |
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Name 2 sources of electrons?
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1. non-photosynthetic organisms : reduced compounds
2. photosynthetic organisms : species excited by light |
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How do oxidation reduction rxns typically occur?
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together, as a pair
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What are electrons essentially?
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a source of energy that allows work to be done
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What is the principle of oxidation-reduction rxns?
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the flow of electrons can do work (electromotive force, emf)
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Where is the flow of electrons from?
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from a relatively reduced compound to a relatively oxidized compound...usually involves redox pairs
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Give example of redox pairs?
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Fe2+ <---> Fe3+ + e- (oxidation, lose)
Cu2+ + e- <---> Cu+ (reduction, gain) overall rxn: Fe2+ + Cu2+ <---> Fe3+ + Cu+ |
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list the biological redox carbon groups from most highly reduced to most highly oxidized? Include the number of electrons?
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1. methane 8
2. ethane (alkane) 7 3. ethene (alkene) 6 4. ethanol (alcohol) 5 5. acetylene (alkyne) 5 6. formaldehyde 4 7. acetalaldehyde (aldehyde) 3 8. acetone (ketone) 2 9. formic acid (carboxylic acid) 2 10. carbon monoxide 2 11. acetic acid (carboxylic acid) 1 12. carbon dioxide (moving down is oxidation, losing) (moving up is reduction, gaining) |
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Name 4 types of electron transfers? (not always obvious in eqns)
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1. directly, as electrons (ex. metals)
2. as hydrogen atoms (H+ + e-) 3. As a hydride ion (H-) (has two electrons that can be transferred) 4. in combination with oxygen (from O2) |
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What is standard reduction potential?
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a measure of molecule's affinity (or lack thereof) for electrons, relative to the hydrogen half-cell rxn
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The hydrogen half-cell rxn?
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H+ + e- ---> 1/2H2 E'=0.000 volts (@stp)
...this is the reference for all other rxn's standard reduction potentials |
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A standard reduction pot. where E' > O has what?
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a greater tendency to acquire e- than H+
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A standard reduction pot. where E' < O has what?
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a greater tendency to donate e- than H+
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For a pair of rxns how do we figure out the reduction pot.
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the net reduction pot. (^E') is the sum of the reduction potentials of the two half-cell rxns
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What is ^E'.
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the reduction pot. for combined rxns
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if ^E' > 0, the rxn will do what?
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proceed spontaneously as written (oppo of ^G)
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if ^E' < 0, the rxn will do what?
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proceed in reverse direction (oppo of ^G)
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What does E'" indicate?
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pH 7 (indicated by apostrophe)
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^G'"s relationship to ^E'"
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^G'"=-nf^E'"
(n is the # of transferred e-s) (f is a constant) (delta G will always have the oppo sign of ^E) |
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What eqn is used if the conc. is not 1.0 M.
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the nernst eqn
^E = E (RT/nF)*ln([e- acceptor]/[e- donor]) |
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Give an example of oxidation reduction energetics?
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C6H12O6(glucose) + 6O2 ---> 6CO2 + 6H2O
^G' = -2840 kj/mol (just know it's a lg number...a lot of energy in glucose...applied differently in body than shown here...more gradual removal of e-s) |
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Glucose's oxid.-reduc. rxns in the body takes place how?
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in many steps....with e-s being removed at various steps...the e-s are transferred to coenzymes specialized for carrying e-s (NAD and FAD)...the coenzymes are sol...but NAD is usually "free" while FAD is usually bound
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FAD vs. NAD.
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NAD = free = floats in cell from one part to another = "truck"
FAD = bound = fixed place in cell = "warehouse" |
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Would NAD+ accept or donate?
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accept e-s
[NAD+] > [NADH] typically NAD+ conc. is greater |
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Would NADPH accept or donate?
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donates e-s
[NADPH] > [NADP+] typically NADPH has higher conc. |
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Nomenclature.
NAD vs. NAD+ vs. NADH |
NAD = generic
NAD+ = oxidized NADH = reduced (2 or more e-s) |
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What is FMN?
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an FAD without adenine
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Two flavin nucleotides?
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FMN/FAD
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Which is more frequent FAD or FMN?
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FAD....the warehouse...accepts 1 e- at a time...bound flavoprotein
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nomenclature.
FAD vs. FADH2 |
FAD = generic and specific oxidized form...he would clarify on a test
FADH2 = reduced |
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Name 3 monosaccharides?
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1. glucose (glc)
2. fructose (fru) sweetest sugar 3. galactose (gal) |
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Name 3 disaccharides and their components?
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1. maltose (glc-glc) - minor food constituent
2. sucrose (glc-fru) found in fruits 3. lactose (glc-gal) |
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maltose saccharides?
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glc-glc
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sucrose saccharides?
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glc-fru
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lactose saccharides?
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glc-gal
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Name the two carbohydrate groups?
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1. monosaccharides
2. disaccharides |
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Name three polysaccharide groups?
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1. glycogen
2. starch in food 3. fiber |
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Describe glycogen briefly?
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-poly-glucose
-highly-branched -not a sig. food source (stored in liver and muscles) |
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starch vs. glycogen?
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starch found in food
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4 points about starch?
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1. poly-glucose
2. amylose : linear 3. amylopectin : branched 4. found in grains: rice, wheat, corn, etc. |
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Fiber is what parts of plants?
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structural part
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Name some non-starch polysaccharide fibers.
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non-starch
ex. cellulose, pectins, gums, etc. |
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Name some non-polysaccharide fibers?
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lignins, cutins, tannins
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Fibers cannot be what?
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broken down by the human digestive system (we lack the enzymes)...so it goes to lg intestine and is typically excreted...we get little energy from it....doesn't contribute calories....aids in digestive process
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Fibers are not a source of what?
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monosaccharides
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Fibers may be digested by what?
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some bacteria in the GI tract
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Where is cellulose found? describe.
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plant cell walls (vegetable, fruits, legumes)...linear and non-digestible, because of beta1->4 linkage
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Where is hemicellulose found? describe?
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cereal fibers...branched...some soluble, some not
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Where are pectins found? describe?
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veggies and fruits...thickeners : form gels
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Where are gums and mucilages found? describe?
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secreted by plants
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Name 4 non-starch polysacch.s?
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1. cellulose
2. hemicellulose 3. pectins 4. gums and mucilages |
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What is the major fuel for most organisms?
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glucose
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if totally oxidized what is the ^G for glucose?
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about -2840kj/mol
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Why is glucose considered a versatile precursor?
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because from it you can synthesize C-skeletons of most major molecules
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3 things that can happen to glucose in higher plants and animals?
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1. stored (polysacch.s, sucrose)
2. oxidized to 3-C cmpd (pyruvate):glycolysis 3. oxidized to pentoses (2 or 3 done if you need energy right now...otherwise stored and you gain weight) |
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Glycolysis is the almost what?
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the almost-universal pathway for carbohydrate catabolism (step by step breakdown and storage)
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What does glycolysis result in?
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the storage of energy in ATP and NADH
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Glycolysis is the first part of what?
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the first part of the catabolism of glucose, either anaerobic (fermentation) or aerobic (when O2 is available)
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Glycolysis is a ? phase process with ? steps.
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2...10
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The 1st 5 steps of glycolysis are what?
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the prepratory phase where we are putting energy in from ATP molecules...then we get energy out as NADH and ATP
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The first part of glycolysis has how many Cs involved? The second part?
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6...3
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What do we put in and what do we get out of glycolysis?
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put in 2 ATP get out 4 ATP and 2 NADH
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In the prep. phase of glycolysis you begin w/ a 6 C molecule and end up with what?
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two 3 C molecules
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In what steps does ATP go into glycolysis thus producing ADP?
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the 1st and 3rd steps of phase 1 (see fig. 14-2)
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What is the molecule you start with in the 2nd phase of glycolysis?
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glyceraldehyde 3-phosphate(2 molecules of this) (these are the two 3 Carbon molecule products from the first phase of glycolysis)
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Phase 2 can be referred to as the ? phase of glycolysis?
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payoff
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How many NADH molecules are created in the 2nd phase of glycolysis?
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2 (1 for each molecule of glyceraldehyde 3-phosphate)
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In what step of glycolysis are the two molecules of NADH produced?
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in the 6th step (which is the first step of the 2nd phase)
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How many ATPs do you end up with from the 2nd phase?
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2 ATPs per molecule...so 4 all together
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What is the net energy received from glycolysis?
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2 ATP and 2 NADH (because you put 2 ATP into process and get 4 out, net 2)
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Give the eqn for glycolysis?
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Glc + 2 NAD+ + 2 ADP + 2Pi -----> 2 pyruvate + 2 NADH + 2H+ + 2 ATP + 2H2O
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The eqn for glycolysis can be thought of as what? So what is the net result?
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2 parts:
1) Glc + 2 NAD+ ---> 2 pyruvate + 2 NADH + 2 H+ (^G'"=-146kj/mol) 2) 2 ADP + 2Pi ----> 2 ATP + 2 H2O (^G'" = +61kj/mol) ...^G'" = -85kj/mol (very exergonic) |
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What is the net ^G'" for glycolysis? what does this tell us about glycolysis?
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-85kJ/mol...so very exergonic...driven forward
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So how much of the energy in glucose is removed thru glycolysis? Where is the left over energy?
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only about 5.2% (just -146kj/mol out of a possible 2840) this is due to the fact that this is only a redox rxn...so much of the energy remains in pyruvate
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How are the 10 steps of glycolysis divided?
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1-5 = "preparatory phase"
6-10 = "payoff phase" |
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What is occuring in step 1 of glycolysis?
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We are adding a phosphoro group from ATP...forms glucose 6-phosphate which is an important 'crossroads' intermediate...exergonic at -16.7
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4 notes about the 1st step of glycolyis?
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1. induced fit (enzyme changes conformation and then rxn can proceed forward)
2. stored energy (addn of phosphoro bond from ATP stores energy) 3. exergonic (some of stored energy used to drive rxn) 4. regulated (often exergonic and regulated are seen together) |
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What goes into step 2 of glycolysis and what comes out?
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nothing goes in and nothing comes out
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2 notes about the 2nd step of glycolysis?
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1. isomerization (simply change of conformation...nothing added or removed)
2. small ^G (not really noteworthy) |
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What is added in during step 3 of glycolysis?
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ATP energy (similar to step 1 with but with no induced fit)
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2 notes about the 3rd step of glycolysis?
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1. energy stored and released (exergonic, ^G'"=-14.2kj/mol)
2. regulated step |
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Things to note about step 4 of glycolysis?
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1. one 6 C mol. becomes two 3 C mol.s
2. endergonic (^G'"=23.8kJ/mol)...unfavorable by itself but it is coupled to previous and later rxns) |
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List the exergonic steps of glycolysis?
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1, 3, 7, 10
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List the endergonic steps of glycolysis?
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2, 4, 5, 6, 8, 9
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Things to note about step 5 of glycolysis?
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1. isomerization (nothing in/out)
2. endergonic but small ^G'" (=7.5kJ/mol) 3. results in 2 molecules of glyceraldehyde 3-phos 4. end of preparatory phase |
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Things to note about step 6 of glycolysis?
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1. begin to get energy out of it (payoff phase)
2. involves a phosphoro group not from ATP (inorganic phosphate) 3. redox resulting in a high-energy compound (1,3-biphosphoglycerate) 4. oxidation with energy stored in P-group and NADH (small ^G'"=6.3kJ/mol) |
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Things to note about step 7 of glycolysis?
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1. energy is now released from the high energy compound from step 6 (1,3-biphosphoglycerate)...energy stored into ATP
2. used to pull previous rxns...^G'"=-18.5kJ/mol, exergonic |
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What does arsenic have to do with glycolysis?
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it's a side step that can go bad...arsenate is structurally similar to inorganic phosphate, it interferes and results in a molecule that can spontaneously decompose...it allows a bypassing of step 6 and 7 and reduces the amt of ATP a cell can make...results in no ATP
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Things to note about step 8 of glycolysis?
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1. isomerization
2. small ^G'"=4.4kJ/mol |
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Things to note about step 9 of glycolysis?
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1. dehydration (some H2O removed)
2. small ^G'"=7.5kJ/mol) 3. results in the high-energy compound phosphoenolpyruvate |
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Things to note about step 10 of glycolysis?
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1. very exergonic, ^G'"=-31.4kJ/mol
2. hydrolysis of PEP coupled to ATP formation: stores energy and drives whole process 3. allosterically regulated 4. ADP converted to ATP and captures a lot of energy 5. remember there are really 2 molecules of ATP here |
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What steps is ATP put into glycolysis?
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1, 3
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In what steps do we get ATP out of glycolysis?
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7, 10
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In what step do we get NADH out of glycolysis?
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6
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Arsenate effects what step of glycolysis?
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causes you to skip 6 and 7...resulting in the absence of 2 ATP...so you would have put 2 ATP in and only got 2 out resulting in a net of 0 ATP (see slides 33 and 34 for summary of rxns)
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6 general notes about glycolysis?
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1. channeling is important (one rxn is immediately followed by another...A--->B,B---->C, etc
2. tightly regulated to maintain a constant [ATP] 3. greatly accelerated in cancer cells (to compensate for limited O2 availability) 4. no need for O2 5. tumors will depend upon glycolysis while other cells will use glycolysis and other pathways |
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Name 3 pathways that feed into glycolysis?
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1. Disaccharides
2. polysacch.s 3. monosacchs (two different possible paths) |
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How do we attain starch?
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diet
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What is glycogen essentially used for?
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storage
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Describe the Feed-in of (storage) polysacch.s into the glycolytic pathway?
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1. involves glycogen, starch
2. two paths (see slide 37) one utilizes the enzyme phosphorylase and one utilizes the enzyme amylase (a key enzyme found in our mouth and intestine) 3. the enzyme amylase breaks starch into maltose and dextrins 4. the phosphorylase enzyme results in glucose-1-phosphate (which is a primary product of glycogen and starch) 5. Ultimately results in Glucose 6-phosphate which is the 2nd intermediate from glycolysis, so this is where it feeds into glycolysis |
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Glycogen breakdown with phosphorylase results in what?
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Glucose 1-phosphate...which is an intermediate that goes on to become Glucose 6-phosphate (this is where it feeds into glycolysis)
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Name 4 disaccharides that feed into glycolysis? How are they involved?
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1. maltose
2. lactose 3. sucrose 4. trehalose (broken down into monomers) |
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How does maltose feed-in to the glycolytic pathway?
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broken down into 2 glucose monomers by hydrolysis
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How does lactose feed-into the glycolytic pathway?
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Broken down into the monomers glucose + galactose by the enzyme lactase
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What do people with lactose intolerance lack?
|
lactase (so lactose reaches the lg. intestine and is converted into toxic products by bacteria [-->cramps, diarrhea]
|
|
|
How does sucrose feed into the glycolytic pathway?
|
broken down into glucose + fructose monomers
|
|
|
How does trehalose feed into the glycolytic pathway?
|
broken down into 2 glucose monomers (trehalose is seen in insects)
|
|
|
Name 3 monosaccharides (other than glucose) that feed into the glycolytic pathway.
|
1. Galactose
2. Fructose 3. Mannose |
|
|
How does galactose feed into the glycolytic pathway?
|
galactose-->glucose 1-phosphate-->Glucose 6-phosphate
|
|
|
What is galactosemia?
|
disordered galactose metabolisis (so can't process galactose)
|
|
|
How does fructose feed into the glycolytic pathway?
|
2 possible ways
1. fructose--> fructose 6-phosphate 2. fructose--> glyceraldehyde 3-phosphate |
|
|
How does mannose feed into the glycolytic pathway?
|
mannose-->fructose 6-phosphate
|
|
|
What happens to the pyruvate from glycolysis?
|
It can either go down one of two anaerobic pathways OR it goes down an aerobic pathway (w/ O2 present) and leads to citric acid cycle
|
|
|
Name one thing that can occur to pyruvate during anaerobic metabolism? (think exercise)
|
pyruvate --> lactate (produces NAD+ in the process which is important for anaerobic metab. b/c you need a steady supply of it to make NADH to allow glycolysis to continue)
|
|
|
How is anaerobic metabolism related to exercise?
|
during vigorous exercise, lactate accumulates in muscle tissue, eventually causing pain, and possibly limiting exercise capability
|
|
|
Other than the formation of lactate what else can occur to pyruvate in the case of anaerobic metab?
|
pyruvate-->ethanol....(in yeast and some other organisms)....Thiamine pyrophosphate (TPP), a coenzyme derived from thiamine, is often reqd for decarboxylation rxns when the caboxyl group is adjacent to a carbonyl group...this is the fermentation that leads to alcoholic bvgs...also produces NAD+ which helps glycolysis
|
|
|
What is TPP?
|
Thiamine pyrophosphate - a coenzyme produced, important when CO2 is involved in a process, derived from thiamine...leads to resynthesis of NAD etc, etc.
|
|
|
Show how we go from catabolism (brkdown) to anabolism (synthesis) with ATP, NAD(P)H, precursors?
|
Convergent Catabolic Pathways (yield energy in ATP and NADH)--->ATP, NAD(P)H, precursor--->divergent anabolic pathways (need energy, ATP and NADH used)
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|
|
What is the opposite of glycolysis?
|
Carbohydrate Biosynthesis (synthesis of glucose instead of breakdown)...the focus is from pyruvate to glucose
|
|
|
The 3 organizing principles of biosynthesis?
|
1. Antiparallel pathways
2. Regulation 3. Coupled Rxns |
|
|
Describe how the principle of Antiparallel pathways relates to biosynthesis?
|
may share some reversible rxns with catabolic pathways, but there is usually 1 irreversible rxn unique to each way
|
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|
Describe how the principle of Regulation relates to biosynthesis?
|
at least 1
-coordinate, reciprocal -usually early in chain |
|
|
Describe how the principle of coupled rxns is involved in biosynthesis?
|
Rxns usually couple to ATP hydrolysis (exergonic) to make process irreversible
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|
What is the central pathway from precursors to carbohydrates?
|
gluconeogenesis (the synthesis of glucose)
|
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|
Where does gluconeogenesis occur?
|
in almost all organisms
|
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|
What is glucose to animals?
|
in animals, for the cells of many organs (esp. the BRAIN), glucose is the major or sole energy source (but some organs cannot synthesize glucose so need it from other sources)
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|
|
Name two organs that rely on glucose from other sources?
|
heart, brain
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|
In higher animals where does gluconeogenesis primarily occur?
|
in the liver
|
|
|
What are the main precursors of gluconeogenesis?
|
1. pyruvate
2. lactate |
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|
Glycolysis and gluconeogenesis have ? common ? to both pathways.
|
7 common enzymes to both pathways (direction depends on concentration of substrate vs. product)
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|
3 rxns of glycolysis are so exergonic that they are essentially irreversible. Which steps?
|
1, 3, 10
step #1 = hexokinase step #3 = phosphofructokinase-1(PFK-1) step #10 = pyruvate kinase |
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|
What does gluconeogenesis do relative to the irreversible steps of glycolysis (1,3,10).
|
it 'detours' around them
|
|
|
What is the std ^G and the ^G in RBCs for the irreversible steps of glycolysis?
|
#1, ^G'"=-16.7, ^G = -33.4
#3, ^G'"=-14.2, ^G = -22.2 #10, ^G'"=-31.4, ^G = -16.7 |
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|
Glycolysis and gluconeogenesis share ? of ? rxns. Explain.
|
share 7 of 10 rxns (gluconeogenesis has bypasses for the 3 very exergonic (~irreversible) rxns, becomes favorable)
|
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|
Which rxn of glycolysis is the 1st bypass for gluconeogenesis?
|
step 10
|
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|
What is the distinguishing intermediate for the first bypass of gluconeogenesis?
|
oxaloacetate
|
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|
How many mol.s of pyruvate does it take to get one mol. of glucose?
|
2
|
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|
What is the cost of the first bypass of gluconeogenesis?
|
1 ATP and 1 GTP per pyruvate mol. (and since there are 2 pyruvate mol.s reqd for 1 mol. of glucose there is really 2 ATPs and 2 GTPs)
|
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|
In relation to a cell where does glycolysis take place?
|
in the cytosol
|
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|
Describe the 6 step rxn for the 1st bypass of gluconeogenesis?
|
1. pyr. moves into the mitochondrion from the cytosol
2. pyruvate ---> oxaloacetate 3. oxaloacetate---> malate (uses NADH to go thru membrane) 4. the malate then goes thru the mitochondrion back into the cytosol 5. Once in the cytosol the malate once again turns back into oxalacetate producing NADH in process 6. oxaloacetate--> PEP (phosphoenolpyruvate) |
|
|
2 essential things to remember about the 'movement' of bypass #1 in gluconeogenesis?
|
1. cytosol--> mito --> cytosol
2. NADH consumed in mitochondria and then produced in the cytosol (NADH cannot cross membrane)...so end result is just a mvmt not a production of NADH, not an actual mvmt, just an equivalent amount |
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|
Gluconeogenesis bypass #1's std ^G vs. actual ^G?
|
^G'"=+0.9kJ/mol
^G = -25kJ/mol ...so favorable ...so moves forward |
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|
The 1st bypass of gluconeogenesis is ? and ?. It is overall an ? process.
|
complex and costly...exergonic
|
|
|
The cost of gluconeogenesis's 1st bypass?
|
break 2 high-energy phosphate bonds (ATP and GTP) to form 1 (PEP)
|
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|
What is the benefit of the 1st bypass of gluconeogenesis?
|
NADH is used up in the mitochondria (where it is relatively plentiful, rxn #2) and reformed in the cytosol (where it is needed later in gluconeogenesis, rxn #3) - it is like an NADH shuttle
|
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|
There are really 2 of the 1st bypasses, where does the second one take place?
|
anaerobic muscle, where lactate is abundant (ex. after a lot of exercise you need to reduce [lactate])
|
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|
What does the first reaction of 2nd bypass #1 produce?
|
NADH in the cytosol, so need to transport NADH equivalent
|
|
|
3 things to remember about the 2nd bypass #1.
|
1. anaerobic muscle
2. decreases [lactate] 3. doesn't need to use up NADH in mito, it's more direct |
|
|
Where does the 2nd bypass of gluconeogenesis occur?
|
it is the reverse step of step 3# in glycolysis
|
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|
What is different about the 2nd bypass of gluconeogenesis and the step in glycolysis which it bypasses?
|
it is a reversal of step 3# in glycolysis without the involvement of ATP/ADP
|
|
|
What is the ^G'" of the 2nd bypass of gluconeogenesis?
|
-16.3kJ/mol
|
|
|
Where does bypass #3 of gluconeogenesis occur?
|
the reverse of step #1 of glycolysis
|
|
|
Why is bypass #3 exergonic?
|
no atp
|
|
|
What is different about Bypass #3 from the 1st step of glycolysis?
|
it is the reverse step without the use of ADP/ATP
|
|
|
What is the enzyme that catalyzes bypass #3? What is important about this enzyme?
|
glucose 6-phosphatose...The enzyme that catalyzes this rxn is found in hepatocytes and renal cells, but not in muscle or brain, so in muscle or the brain glucose cannot be synthesized by this pathway. Glucose for these organs must come from other sources.
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|
Gluconeogenesis is ? and not just ? ?.
|
expensive...not just glycolysis reversed
|
|
|
What (energy) is reqd to synthesize 1 molecule of glucose (gluconeogenesis)? What does this mean?
|
4 ATP, 2 GTP, 2 NADH...we put more energy in then we get out from glycolysis
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|
|
What makes gluconeogenesis ~irreversible?
|
the input of energy
|
|
|
The energy yield of glycolysis vs. the energy reqts of gluconeogenesis?
|
Glycolysis = yields a net of 2 ATP and 2 NADH
Gluconeogenesis = reqs 4 ATP, 2GTP, and 2 NADH |
|
|
What is the beginning of the synthetic process for glucose?
|
pyruvate
|
|
|
What can be converted to pyruvate?
|
many AAs (the glucogenic AAs)
|
|
|
The glucogenic AAs can be converted to what?
|
pyruvate (or intermediates of the citric acid cycle such as OA)...which can then enter into gluconeogenesis
|
|
|
In animals what can not be net converted to glucose?
|
fatty acids, which are converted to Acetyl-CoA cannot be broken down and synthesized into glucose
|
|
|
Although FAs cannot be converted to glucose, what can glucose do?
|
it can be converted into FAs
|
|
|
How must glycolysis and gluconeogenesis be regulated?
|
they must be reciprocally regulated, in a given place at a given time...when one is "on" the other is "off"
|
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|
Does arsenate inhibit glycolysis?
|
no, it does not inhibit it...it is incorporate in it and the "spun off"...just results in a reduction of ATP
|
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|
Does arsenate effect gluconeogenesis? explain.
|
No...because phosphate is a product not a reactant (in glycolysis arsenate replaces phosphate)
|
|
|
What is an ATP equivalent?
|
amt of energy that is released in the breakdown of ATP (to ADP + P) or used in the synthesis of ADP + P (to ATP)
|
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|
What amount of energy is also equivalent to ATP?
|
the breakdown/synthesis of GTP
|
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|
If glycolysis and gluconeogenesis were not regulated so one was "on" while the other was "off" what would occur?
|
you would be using ATP for nothing at all (maybe just a little heat)
|
|
|
What does the Pentose Phosphate Pathway produce?
|
1. NADPH
2. Ribose 5-P |
|
|
The Pentose Phosphate Pathway is relatively ? ? ? when compared to glycolysis?
|
relatively minor but important when compared to glycolysis ("minor" as in it doesn't occur very often)
|
|
|
The Pentose Phosphate Pathway converts ? to ? and ?.
|
converts GLUCOSE 6-PHOSPHATE to NADPH and RIBOSE 5-PHOSPHATE
|
|
|
What is NADPH?
|
an almost universal reducing agent (energy source) for anabolic pathways (FAs, steroids)
|
|
|
What is Ribose 5-P?
|
it is needed for the biosynthesis of nucleotides, which are needed for DNA and RNA synthesis
|
|
|
Who is Ribose 5-P more important for?
|
children...because most adults have enough so that we don't need to synthesize more
|
|
|
If tissue doesn't need Ribose 5-P what can it do?
|
it can be "recycled" into glucose 6-phosphate
|
|
|
In the process of carbohydrate digestion what occurs in the mouth and salivary glands?
|
Starch from our diet is broken down by the salivary enzyme AMYLASE into small polysaccharides and maltose
|
|
|
In the process of carb. digestion what occurs in the stomach?
|
the enzyme AMYLASE IS DEACTIVATED halting starch digestion
|
|
|
In the process of carb digestion what occurs in the small intestine and pancreas?
|
starch is broken down by pancreatic amylase in small polysaccharides and disaccharides
|
|
|
After pancreatic amylase breaks down starch into small polysaccharides and disaccharides what occurs?
|
disaccharidase enzymes hydrolyze the disaccharides into monosaccharides :
1. Maltose --> Glu + Glu 2. Sucrose --> Fru + Glu 3. Lactose --> Gal + Glu |
|
|
After disaccharidase breaks down the disaccharides into monosaccharides what occurs?
|
the intestinal cells absorb the monosacch.s
|
|
|
Concerning carb. breakdown what happens to fiber in the mouth?
|
chewing crushes it and saliva moistens it (not effected by enzymes)
|
|
|
Concerning carb. breakdown what happens to fiber in the stomach?
|
it is not digested and it delays gastric emptying
|
|
|
What occurs to fiber in the small intestine?
|
it is not digested and it delays absorption of other nutrients
|
|
|
What occurs to fiber after it enters into the large intestine?
|
most fiber passes intact through the digestive tract to the large intestine. Here BACTERIAL ENZYMES DIGEST FIBER into fatty acids and gas
|
|
|
How does fiber regulate bowel activity?
|
it holds water, and binds substances such as bile, cholesterol, and some minerals, carrying them out of the body.
|
|
|
In catabolism what kind of chains are digested more rapidly?
|
branched chain compounds
|
|
|
In catabolism what kind of chains are digested more slowly?
|
linear chain compounds
|
|
|
In absorption what moves quickly into the blood?
|
glucose and galactose
|
|
|
In absorption what is transported more slowly into the blood?
|
fructose
|
|
|
Why are branched chains digested more rapidly then linear chains?
|
because enzymes can attack both ends
|
|
|
What is the advantage of linear chains being digested more slowly?
|
helps prevent spikes in [glucose]...so does not contribute to dev. of dietary diabetes (diabetes II)
|
|
|
Which carbs are healthier, linear or branched?
|
linear
|
|
|
Give an example of a linear carbohydrate molecule that is more healthy for you?
|
fructose (found in fruits)
|
|
|
Lactose intolerance is the result of what?
|
having little to no lactase enzyme...which results in lactose in the large intestine because it is not broken down and can make its way there
|
|
|
What is the solution to a lack of lactase?
|
reduce lactose and add lactase
|
|
|
If you try to reduce lactose in the diet what do you have to be cautious about?
|
milk products contain many important nutrients (ex. riboflavin, vitamin D, calcium)...so don't want to totally eliminate them
|
|
|
What could you say about the usefulness of the glycemic effect? Why?
|
it is somewhat controversial...the studies are somewhat questionable
|
|
|
What is the glycemic effect?
|
food containing carbs leads to an increase in blood [glucose], which elicits an insulin response (secretion)
|
|
|
How are foods glycemic effect classified?
|
according to how rapidly they lead to this increase
|
|
|
Give examples of some foods with a high glycemic effect?
|
baked pot., cornflakes, sports dr., donuts
|
|
|
Give examples of some foods with a low glycemic effect?
|
peanuts, cashews, soybeans, milk, beans
|
|
|
What is a low glycemic index characterized by?
|
slow absorption of glc, modest rise, smooth return
|
|
|
What is a high glycemic index characterized by?
|
rapid absorp. of glc, surge in [glc], dramatic drop
|
|
|
What does DRI stand for?
|
Dietary Reference Intakes (Amer. and Canadian standards...continually updated)
|
|
|
What does RDA stand for?
|
Recommended daily allowances...according to age, sex, and life stage
|
|
|
What does DV refer to?
|
Daily Values (seen on food labels)...avg recommended daily intake for a person on a 2000 calorie diet (the avg. is not based on age or sex)...so a rough approximation
|
|
|
Fiber is a ? sugar?
|
non-caloric
|
|
|
What is a Kcal = to.
|
a calorie
|
|
|
In the U.S. 1/2 of our sugar intake comes from where? The other 1/2 is from where?
|
milk, fruits, veggies, and grains (no reason to worry about this sugar intake)...the other 1/2 is refined and added : sucrose, corn syrup, honey, etc (this is what we want to reduce by about %50)
|
|
|
Typically Americans get about 1/6 of daily energy we need from where? What is the recommendation?
|
simple sugars (like mono- and disaccharides)...the reco. was < 10%, so we get about %50 more than we should
|
|
|
Is honey a healthier sugar?
|
some suggest is is but it is a subtle difference
|
|
|
The sugar in sucrose?
|
sucrose = glc-fru
|
|
|
Besides sucrose what else is in honey?
|
TRACE amts of protein, Ca, Fe, Vit. C
|
|
|
What does refined mean in reference to sugar?
|
processed/purified; nothing added
|
|
|
What is the problem with refined sugar?
|
too many calories...too few nutrients (low nutrient density)...ie, it is pure sugar (at least other sources, like cereal or something, has other stuff besides sugar in it)
|
|
|
What is a dental carie?
|
cavities...an effect of sugar...related to bacteria and acid...the worst case is sugar alone between meals (candy, etc)
|
|
|
Is sugar a major factor in HD?
|
no, but it is a minor one (when compared to smoking, genetics, and lipids)
|
|
|
Is hyperactivity connected to sugar?
|
no connection supported by research
|
|
|
What is the recommended intake of sugar?
|
less than or equal to %10 of total calories
|
|
|
If someone is on a 2000 cal diet how many cal.s should come from sugar?
|
~200 cal
|
|
|
1tsp of sugar = how many calories?
|
20
|
|
|
2 General types of fiber?
|
1. soluble
2. insoluble |
|
|
Which type of fiber do we need in our diet, sol. or insol.?
|
both
|
|
|
Soluble fibers are soluble where?
|
in an aqueous environ. like our digestive tract
|
|
|
4 good sources of soluble fiber?
|
1. fruits
2. oats 3. barley 4. legumes (beans, peas) |
|
|
What does soluble fiber do to GI transit?
|
delays it
|
|
|
What do both soluble and insoluble fiber do to [glc]?
|
delay glc abs (prevents spikes in [glc])
|
|
|
What is a good effect of soluble fiber?
|
lowers bl. cholesterol
|
|
|
3 sources of insoluble fiber?
|
1. veggies
2. wheat and corn bran 3. whole grains |
|
|
What does insoluble fiber do to GI transit?
|
accelerates it
|
|
|
What does insol. fiber do to starch hydrolysis?
|
it slows it
|
|
|
What does insol. fiber do to fecal weight?
|
it increases it (this is an issue for older adults)
|
|
|
Concerning wt. control, starch has ? energy per volume when compared to ?.
|
starch has less energy per volume when compared to fats
|
|
|
Fiber gives a feeling of what?
|
fullness
|
|
|
Starch and fibers have a ? glycemic effect when compared to sugars?
|
low
|
|
|
What may fiber decrease the risk of?
|
heart disease
|
|
|
Why does fiber decrease the risk for heart disease?
|
The reasons (mxms)are not well understood...soluble fiber binds and removes bile acids, lowers blood cholesterol level...byproducts of bacterial digestion may inh. cholesterol synthesis in the liver (so decreases levels and prevents synthesis of new ones)...fiber may displace fat in the diet
|
|
|
A high-fiber diet is correlated with a decrease risk of what?
|
some cancer, esp. colon cancer
|
|
|
Name some sources of fiber that are correlated with decreased risk of cancer?
|
green and yellow veggies, and citrus fruits
|
|
|
Is high fiber absolutely related to a decreased risk of cancer? Explain.
|
not necessarily...a high fiber DIET is correlated, so the reduction could be due to fiber OR other chemicals in these foods such as antioxidants and phytochemicals
|
|
|
Some populations eating a high-carb. diet of starch/fiber have a ? incidence of diabetes.
|
decreased incidence of diabetes (for starch and fiber, not refined sugar)
|
|
|
The fact that some pop.s with a high carb. (starch/fiber) intake have a decreased incidence of diabetes may be related to what? (2)
|
1. may be b/c diets are low in fat
2. soluble fibers may slow glucose absorption, moderating glucose surge/rebound (which appears to lead to type 2 diabetes) |
|
|
What is associated with increased GI health?
|
intake of dietary fiber
|
|
|
What kind of fiber helps to alleviate constipation as we age?
|
insoluble
|
|
|
4 UNHEALTHY effects of EXCESS fiber.
|
1. for a person who does not eat much (elderly, young, malnourished) consuming a lg amount of fiber may be related to consuming an inadequate amt of foods rich in nutrients (like vit.s, minerals and proteins)
2. Fiber may decrease nutrient absorption 3. Sudden change to high fiber can lead to GI problems (discomfort, obstruction) 4. W/out adequate water : stool problems (none of the above should be taken to mean that fiber in the diet is unhealthy) |
|
|
The recommended dietary intake of calories from carbs?
|
45 -65%
|
|
|
Approx. how many cal. of a 2000-cal diet should come from carbs?
|
1100-1200cal
|
|
|
What is the recommended DV of dietary fiber?
|
25 grams (sol and insol)...avg intake in U.S. is about half of this
|
|
|
2 general types of sugar alternatives?
|
1. Artificial sweeteners
2. Sugar replacers |
|
|
Do "artificial sweeteners" provide energy?
|
no (except for aspartame)
|
|
|
Do "sugar replacers" provide energy?
|
yes
|
|
|
Are artificial sweeteners toxic?
|
they are approved by the FDA but "dose is everything"...at reasonable levels approved sweeteners are not toxic
|
|
|
3 levels of approval by the FDA for artificial sweeteners?
|
unapproved, approved, and pending approval
|
|
|
Name 6 approved sweeteners?
|
1. saccharin
2. aspartame 3. acesulfame-K 4. sucralose 5. neotame 6. tagatose |
|
|
Which approved sweetener has calories unlike most of the approved sweeteners?
|
aspartame (has 4kcal/g)
|
|
|
The approved sweetener Neotame contains phe but PKUs do not need to worry about it. why?
|
because the phe is inaccesible
|
|
|
Name 2 artificial sweeteners that are awaiting approval by the FDA?
|
1. alitame
2. cyclamate |
|
|
Do artificial sweeteners help to reduce weight?
|
not clear...because people may just replace the calories elsewhere in their diet
|
|
|
Name an artificial sweetener that is not approved?
|
Stevia
|
|
|
Stevia is an herb from where?
|
from a south american shrub
|
|
|
Why is stevia not approved?
|
lack of research
|
|
|
Is stevia not approved because it is dangerous?
|
no...it's probably ok, but there are concerns about reproduction, cancer, and metabolism
|
|
|
Although stevia is not approved for use as an artificial sweetener, what is it used for?
|
as a dietary supplement...less rigorous approval process...so just can't be pre-added to food
|
|
|
Sugar replacers may also be referred to as what?
|
sugar alcohols
|
|
|
Name 6 sugar replacers?
|
1. mannitol
2. sorbitol 3. xylitol 4. maltitol 5. isomalt 6. lactitol (aka sugar alcohols...recognizable by -ol) |
|
|
Name 3 products where you may find sugar replacers (sugar alcohols)?
|
1. gum
2. candy 3. pharmaceutical and oral health products |
|
|
Do sugar replacers have calories?
|
yes, but fewer than sugars
|
|
|
What is the glycemic effect of sugar replacers?
|
low glycemic effect, (but most do not have a glycemic effect of 0)...so most do raise blood glucose a little
|
|
|
What negative side effect may be caused by the sugar alcohols (sugar replacers)?
|
may cause abdominal discomfort, diarrhea...food labels must carry an advisory notice
|
|
|
Sugar replacers (sug. alcohols) do not contribute to what?
|
dental caries
|
|
|
What are "net carbs"
|
term invented by "atkins, inc."...not an approved designation...represents less than total carbs...'no count carbs'
|
|
|
What do 'no-count' carbs include?
|
-fiber...atkins includes all "non-caloric and/or non blood sugar impacting carbs" but there is no universally accepted def.
|
