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52 Cards in this Set

  • Front
  • Back
Energy and Cellular Metabolism
- Anabolism
- Catabolism

Dynamic equilibrium
- anabolic/catabolic rates are equal
3 Metabolic Pathways...
are used by cells to transfer the energy released by catabolism:

* Glycolysis
* Krebs Cycle
* Oxidative Phosphorylation
* first major pathway in energy metabolism of glucose
* occurs with/without O2 (arobic/anarobic)
* occurs in cytosol
* it is a series of 10 enzymatic reactions beginning with glucose and ending with pyruvic acid or lactic acid (depending on the availibility of oxygen)
* glycolysis yields 2 ATP for each glucose
equation for GLYCOLYSIS
Glucose + 2 ADP + 2 Pi + 2 NAD+ --> 2 Pyruvate + 2 ATP + 2 NADH + 2 H2O + 2H+
What are the ways Pyruvate can proceed?
Pyruvate can proceed 2 ways depending on the availibility of o2
... if o2 is availible pyruvate enters the Krebs Cycle
... if o2 is NOT available pyruvate is convertd to LACTATE
How is more energy gained?
more energy is gained under aerobic (o2) conditions because 2 more H atoms are available to use for energy transfer (rather than transferring then to lactate)
Kreb's Cycle
* pyruvate must be decarboxylated (releases CO2) and form NADH to enter Kreb's cycle
* the 2 carbon acetyl group remaining is accepted by Coenzyme A
* the Cycle is a circular sequence of 8 reactions thaqt occur in the matrix of mitochondria during which:
**1. 2 CO2 are formed
**2. 4 electrons are transfered to electron-carrier coenzymes (3 to NAD+)(1 to FAD)
**3. 1 ATP is formed
** for each acetyl group
Oxidative Phosphorylation
* most energy derived
* the energy transferred to ATP is derived from the energy released when hydrogen atoms are oxidized and ultimately form water
* OP mediated by proteins called cytochromes
* at 5 steps electons are transferred to NAD+ or FAD+
* as electrons are transferred from cytochrome to cytochrome the energy released is used to move hydrogen ions (protons) into mitochondria producing a hydrogen ion gradient and thus potential energy
* when these electrons eventually pass to oxygen (oxidative phosphorylation)
*** MOST of the ATP is produced
o2 + 4e- + 4H+ ----> 2H2O
* most energy derived from electron transport is used to phosphorylate ADP to ATP (oxidative phosphorylation)
Oxidative Phosphorylation
1/2 o2 + NADH + H+ -----> H2O + NAD+ + 53 kcal
Oxydative Phosphorylation
1. the energy released as electrons are transferred is used to pump H ions into the mitochondria
2. this creates a high concentration of H ions inside mitochondria
3. which cause H ions to flow thru ATPase molecules
4. energy from this flow is used to convert ADP ---> ATP
5. newly formed ATP moves out of mitochondria by facilitated diffusion
How much energy is released during catabolism of one mole of glucose?
686 kcal
formula for catabolism of one mole of glucose
C6H12O6 + 6O2 ----> 6H2O + 6CO2 + 686 kcal
Chemical reactions:
1. FORMING chemical bonds (endergonic)
2. BREAKING chemical bonds (exergonic)
Energy is measured in ...
1 calorie =
amount of heat energy required to raise the temperature of 1 g of water 1 C
Rate of Chemical Reactions
1. Concentration of reactants
2. Temperature
3. Activation energy
4. Catalyst
Rate of Chemical Reactions

H2CO3 <======> CO2 + H2O + 4Kcal/mol
reactants products energy
Reaction rate changes
* as concentration of reactants becomes less
* as concentration of products becomes more
What determines rate/direction of net reaction?
Concentration of reactants and products determines rate/direction of net reaction.
Chemical Equalibrium
* when rates of forward and reverse reactions becomes EQUAL and concentrations do not change

carbonic anhydrase
H2CO3 <===================> H2O + CO2
Where do the 38ish ATP come from?
2 ATP from Glycolysis
2 ATP from Kreb's Cycle
34 ATP from Oxidative Phosphorylation
7 kcal energy to form
ATP per glucose
7 X 38
266 kcal energy transferred
420 kcal lost as heat
for each 2 electrons that go thru the electron transport chain up to how many ATPs ae synthesized?
up to 3 ATP
Diagram H atom to ATP
Glycolysis 2 ATP
Kreb's Cycle 2 ATP
20 H atoms
(in ox/red up to 3 ATP/ pair e-) 10 prs x 3 = 30 ATP

4 H atoms
(2 ATP/pair e-) 2 prs x 2= 4 ATP
Total: 38 ATP
* proteins
* biological catalysts
* react with substrates form products
* specific
* binds to substrate at ACTIVE SITE on enzyme (complementary shape)
* enzymes lower the required activation energy
* 90% of proteins in a cell are enzymes
* 1,000 - 4,000 enzymes/ animal cell

S + E <=====> ES <=====> E + P
1. metal ions
ie: Fe++ on catalase
Fe++, Cu++ on cytochrome oxidase
2. Coenzymes
ie: NAD+ nicotinamide adenine dinucleotide
FAD flavin adenine dinucleotide

Metal Ions
* Ca++, Mg++, Mn++, Cu++, Zn++
* inorganic
* attach to enzyme as part of active site/causing conformational changes in enzyme that allow it to combine with the substrate
* allows for better "fit"
* sometimes form part of temporary ES complex
* activators or inhibitors

* organic molecules derived from water-soluble B vitamins (niacin/riboflavin)
* molecule that directly participates as a substrate in the reaction being catalyzed
* catalyze reactions in which atoms (H, CH3, CH3CO) are removed or added to the substrate

R-2H + coenzyme <===> R + coenzyme - 2H
many types of enzymatic reactions in a cell do not occur independently but, rather are LINKED together in an interrelated pattern called CELLULAR METABOLISM
a SEQUENCE of enzyme-mediated reactions which lead to the formation of products is called METABOLIC PATHWAY
The flow of ENERGY in living systems is called BIOENERGETICS
energy in biological systems obeys the LAWS OF THERMODYNAMICS
First Law of Thermodynamics
* energy can be transformed from one form to another, but can be neither created nor destroyed
Second Law of Thermodynamics
* the universe and its parts become increasingly disorganized (entropy)
* energy transformations increase entropy in a system
* only energy in an organized state (free energy) can be used to do work.
Atoms ORGANIZED IN COMPLEX molecules like glucose have more ..
free energy than small molecules like CO2/H2O
The ENERGY released by exergonic reactions (catabolism) in a cell are used to form
ADP / ATP formula
ADP + Pi + 7 Kcal <===> ATP + H2O
when ATP is hydrolyzed, the removal of the terminal phosphate group yields ...
7 kcal of energy
Cells use this energy (ATP hydrolysis) by coupling ATP hydrolysis to endergonic reactions for
muscle contractions
membrane transport
synthesis of cell structures
40% of the energy derived from catabolism ...
is transferred to ATP
60% of the energy from catabolism ...
goes off as heat
most of the potential energy carried by glucose is captured by
Oxidation - Reduction reactions
One molecule GIVES UP electrons (oxidation)
One molecule ACCEPTS electrons (reduction)
The electrons are carried by COENZYMES
1. Nicotinamide adenine dinucleotide (NAD)
2. Flavin adenine dinucleotide (FAD)
Oxidative Phosphorylation occurs where?
* occurs on mitochondrial membrane