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106 Cards in this Set
- Front
- Back
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Plasma Membrane
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encloses cell
receives information import and export of cellular molecules capacity for movement and expansion |
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internal membrane
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encloses intracellular compartments (organelles)
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Other notable properties of membranes
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fluid
selective permeability highly structured |
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Fluid Mosaic Model
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movement of vesicles points to fluidity of membranes
combination of lipids and proteins moves in 2 dimensions (unless enzyme flippase involved) |
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micelles
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artificial spheres of membrane that can be used to study membrane behavior
-can study assymetry -can addd proteins to examine protein function |
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Why does the lipid bilayer form spheres?
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sealed compartment leaves no open ends so it is more energetically favorable
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Neutral phospholipids
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phosphatidylcholine
sphingomyelin phosphatidylethanolamine |
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negatively charged
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phosphatidylserine
phosphatidyinositol |
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cholesterol
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restricts fluidity in membranes
amount can vary depending on conditions packs between phospholipids to make membrane more rigid found primarily in animal cells environmental conditions can influence levels of cholesterol in membranes |
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lateral diffusion
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movement of the entire phospholipid molecule in the membrane (2D)
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flexion
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movement of the tail of the phospholipid, while the head remains in place
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flip flop
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flipping sides of the membrane (only occurs with flippase)
requires catalysis |
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platelets
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cell fragments that float in the bloodstream
when activated, they degranulate (clump). caused by flippase turning membrane inside out this exposes receptors that allow for clumping |
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Membrane asymmetry
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charges across the membrane are different
(ie more negative phospholipids on the interior of the membrane) |
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membrane synthesis
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generated in the smooth ER and added to cytosolic face
flippase equilibrates the membrane across bilayer new membrane is redistributed to a number of areas via vesicles. Nuclear membrane is contiguous with ER, so membrane moves there by diffusion |
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types of membrane proteins
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transporters
anchors receptors enzymes |
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transporters
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(Na+ pump)
actively pumps Na+ out of cells and K+ in |
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anchors
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(integrins)
link intracellular actin filaments to extracellular matrix proteins |
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receptors
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(platelet-derived growth factor receptor)
binds extracellular PDGF and, as a consequence, generates intracellular signals that cause the cell to grow and divide |
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Enzymes
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(adenylyl cyclase)
catalyzes the production of intracellular signalling molecule cyclic AMP in response to extracellular signals |
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Prenylation
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post translational modification that allows the proteins to be embedded in the membrane
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Erythrocytes
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red blood cells with concave shape
transmembrane proteins anchoring the cytoskeleton cause this shape |
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glycolipids
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short chain sugars bound to lipid membrane by lipids
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glycoproteins
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long chain sugars bound to membrane by proteins
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GAGs- glycoaminoglycans
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they are protective
form lubricant involved in cell to cell recognition |
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Blood type
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determined by sugar types on RBCs
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Lectins
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carbohydrate binding proteins
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Membrane is semipermeable. explain
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Allows in:
-small hydrophobic (nonpolar) molecules -small uncharged polar molecules Keeps out: Larger uncharged polar molecules ions |
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Aquaporins
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allow trafficking of water molecules easily
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transporter
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has a solute binding site
requires conformational change to move solute |
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Channel protein
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allows free flow of solute (mainly ions) down their respective concentration gradients
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Passive transport
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ex. channel-mediated and transporter-mediated
molecules flow down their gradients (H to L concentration) |
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Active transport |
Pushes molecules against their gradient
requires energy input |
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facilitated diffusion
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passive process
requires a transporter limit to the speed the transporter can allow the molecule to diffuse conformational changes requires a certain amount of time. |
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factors affecting net diffusion
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size of the concentration gradient
electrical potential pressure differences -increases energy available to cause net movement from high to low pressure |
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Other transporters not in the plasma membrane
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pyruvate transporters in mitochondria
Proton transporters in lysosome |
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two components to an electrochemical gradient
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voltage (from ion charges)
concentration gradients (from ion presence) |
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Three ways active transport is driven in cells
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coupled transports
ATP driven pumps light driven pumps |
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Secondary active transport
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antiporters and symporters
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What is an antiporter?
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moves molecules in opposite directions. Sodium is usually the "driver"
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What is a symporter?
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moves molecules together in same direction
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What causes the resting membrane potential?
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Potassium "leaks" out of the cell constantly, so pumps are required. 3 sodiums pumped out for every 2 potassiums in.
Na+/K+ pump accounts for 10% of resting membrane potenial |
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electrogenic
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the production of electrical charge in living cells
(Na+/K+ Pump) |
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osmotic pressure
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Pressure of water diffusing from an area of higher water concentration to lower concentration.
Driven by solute concentration of either side of the membrane |
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How do you measure osmotic pressure?
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the amount of pressure required to move a shifted osmotic system back to its original position
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Donnan effect
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even if "equilibrium" is reached, proteins would still cause movement of water
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What is the relationship between primary and secondary active transport?
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One (primary) provides the gradient to "drive" the other.
ex. sodium pumped against in order to build gradient, the follows gradient in a symport or antiport to move other molecules |
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Some uses of calcium:
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binding to CBP (calcium binding proteins) like calmodulin and troponin
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Na+/K+ ATPase
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enzyme for the Na/K pump
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H+ ATPase
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enzyme for proton pumps
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Types of Ion Channels (3)
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Voltage gated
Ligand Gated Mechanically gated |
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Describe voltage gated ion channels
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open in response to membrane polarity
Na+ and Ca2+ are depolarizing K+ and Cl- are hyperpolarizing |
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Describe Ligand gated ion channels
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binding protein causes change in polarity within a small region of the channel
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Describe mechanically gated ion channels
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physically caused to open (very rare) such as in the inner ear
cells are linked to each other, channels open when cells are physically stimulated --this mechanism initiates hearing by sound waves opening stress channels in the ear |
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Nernst equation
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-62log(Ki/Ko)
Ki=concentration inside Ko=concentration outside |
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What is the main cause of resting membrane?
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leakage of K+ ions out thru leakage channels
(90-95%) |
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Lipid Rafts and Caveolae
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flask shaped invaginations in the membrane
shape is maintained by a cytoplasmic coat of proteins of which "caveolin" is the most important. provide scaffolding system for organizing signaling components |
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Caveolin
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many seen in endothelial cells and muscle cells
In many cancer cells, caveolin disappear, activating signaling pathways and loss of regulation |
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NO (nitric oxide)
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transducer present around lipid rafts note: caveolin disruption lead to cardiac size increase in mice |
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MAP (mitogen activated protein) kinase
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transducer present around lipid rafts
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Sodium/Glucose symport
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Sodium moving along its gradient pulls glucose into cells with it.
Plays a role in "transcytosis without vesicles" |
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Membrane depolarization
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opening of ion channels allowing ions to flow down their electrochemical gradients.
Changes charge across the membrane Depolarization can travel the length of an axon via voltage-gated channels |
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Propagation
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Movement of an electrical signal along the cell membrane causing ion channels to open, inactivate, then close.
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Sarcoplasmic reticulum
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calcium storage and basically the ER of muscle cells
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myofibril
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filament in the contractile apparatus of cardiac muscle
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Mitochondrial matrix
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space containing highly concentrated mixture of hundreds of enzymes
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Mitochondrial inner membrane
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folded into numerous cristae
contains proteins that carry out oxidation to make ATP |
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Mitochondrial outer membrane
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permeable to all molecules 5000 daltons or less
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porin
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large, channel-forming protein found in mitochondrial outer membrane allowing for permeability
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Mitochondrial intermembrane space
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space containing several enzymes that use the ATP passing out of the matrix to phosphorylate other nucleotides
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Chemiosmotic coupling
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process that occurs in sealed, closed membrane.
Generates the proton-motive force, which in turn, drives many other processes |
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NADH
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generated thru glycolysis and the citric acid cycle
carry a proton and 2 electrons which are used in ATP production donation regenerates NAD+ |
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ubiquinone
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cytochrome Q
between NADH dehydrogenase complex and cytochrome b-c complex carries electrons through from one portion of the ETC to the next |
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NADH degydrogenase complex
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First enzyme in the ETC
electrons donated from NADH, forming NAD+ 2 electrons enter, one proton is pumped out into intermembrane space electrons then move to ubiquinone |
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cytochrome b-c1 complex
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accepts electrons from ubiquinone.
pumps out 1 proton for every 2 electrons electrons then move to cytochrome c |
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cytochrome c
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has higher electron affinity than cytochrome b-c1 complex
pushes electrons on to cyctochrome oxidase complex |
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cytochrome oxidase complex
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accept electron from cytochrome c
pumps out 1 proton for every 2 electrons bonds 2 protons to 1 oxygen forming water |
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Proton motive force
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due to either:
membrane potential difference (negative charge on side opposite proton) or H+ gradient (less protons on one side than other) |
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ATP synthase
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coupled usually with ETC
As protons are pumped out by ETC, they move back in via this enzyme, which phosphorylates ADP to for ATP -primary ATP production process -Oxygen is final electron receptor |
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F1ATPase
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specific enzyme that causes phosphorylation of ADP in ATP Synthase
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Glycerol-phosphate transport
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transport method of electrons from NADH into mitochondrial membrane for ETC
uses 2 ATP per NADH active in muscle tissue |
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Malate-aspartate transport
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transport method of electrons from NADH into mitochondrial membrane for ETC
uses 3 ATP per NADH active in heart and liver |
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carrier:
ATP |
carries:
phosphate |
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carrier:
NADH, NADPH, FADH2 |
carries:
electrons and hydrogens |
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carrier:
Acetyl CoA |
carries:
acetyl group |
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Carrier:
Carboxylated biotin |
carries:
carboxyl group |
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carrier:
S-adenosylmethionine |
carries:
methyl group |
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carrier:
Uridine diphosphate glucose |
carries:
glucose |
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Condensation
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+(delta)G
bonds molecules, releases H2O energetically unfavorable |
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Hydrolysis
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-(delta)G
breaks molecules, uses H2O energetically favorable |
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Stepwise oxidation of sugar
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small activation energies overcome by body temperature
many small steps allows for energy storage in activated carrier molecules highly useful in the body |
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Direct burning of sugar
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large activation energy, can only be overcome by extreme heat
all free energy is released, none is able to be stored. not useful in the body |
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Glycolysis step 3
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use of ATP occurs here
location where the entry of sugars in controlled |
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phosphofructokinase
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enzyme from step 3 of glycolysis
used to form fructose 1,6-bisphosphate |
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glucose-6-phosphate
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formed early in glycolysis
most cells can transport glucose, but not this. causes the molecule to be trapped within the cell so that glycolysis can proceed to conclusion |
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substrate level phosphorylation
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transfers phosphate from sugar to ADP
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oxidative phosphorylation
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transfer of phosphate from ADP to form ATP that occurs in the mitochondria
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Fermentation
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occurs only when oxygen is not available for the citric acid cycle to proceed past step 6
beneficial for its regeneration of NAD+, which allows glycolysis to continue mammalian cells-form lactate yeast cells- form ethanol and CO2 |
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Kreb's cycle (one turn)
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produces 3 NADH, one GTP, and one FADH2
releases two molecules of CO2 |
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gluconeogenesis
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exhaustion of glycogen reserves stimulates glucose production from amino acids and sugars
basically the opposite of glycolysis mainly in vertebrates with livers |
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glycogenesis
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process by which excess glucose after feeding is broken down to glycogen
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glycogenolysis
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decreased glucose between feedings stimulated depolymerization of glycogen
Glucose 1 Phosphate is converted to glucose 6 phosphate, which enters into glycolysis |
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controls for Kreb's cycle (3)
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availability of substrate
high intermediate product accumulation feedback inhibition |
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pyruvate dehydrogenase
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converts pyruvate to Acetyl CoA
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Citrate synthase
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Combines oxaloacetate and acetyl CoA
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Reactants that can be used in gluconeogenesis
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lactate.
pyruvate citric acid cycle intermediates glycerol alamine and glutamine (types of amino acids) lysine and leucine are not used |
