Flashcards in Lecture 17: Energy Balance and Metabolism I Deck (68)
Define free energy and relate to exergonic and endergonic reactions.
> deltaG = standard free energy difference.
= difference in free energy when 1 mole of each reactant is converted to 1 mole of each product at 1 atm pressure at 25 C.
> negative deltaG = exergonic reaction
> positive delta G = endergonic reaction
> ATP -> ADP + Pi delta G = -7300 cal/mole (at 25 C)
> ATP -> ADP + Pi delta G = -12,000 cal/mole (at 37 C)
What does galactose, glucose, and fructose get converted to to enter the glycolytic pathway?
List the multiple transport of glucose into tissue cells.
> Active sodium-glucose co-transport (active transport of sodium provides energy for absorbing glucose against a concentration gradient)
> Facilitated Transport (higher to lower concentration)
In the uptake of glucose, what does the presence of insulin do?
increases glucose transport x10
In the uptake of glucose, what does the phosphorylation of glucose do?
prevents diffusion out of cell
**phosphorylation can be reversed in liver, renal, and intestinal cells**
What factors can activate phosphorylase?
> epinephrine (from adrenal gland)
> glucagon (from alpha cells of pancreas)
In glycogenesis and glycogenolysis, what are the effects of phosphorylase?
> promotes conversion of glycogen to glucose
> glucose can then be released into blood
What enzyme does glycogen -> glucose-1-phosphate?
What enzyme does glucose-6-phosphate -> blood glucose?
What enzyme does blood glucose -> glucose-6-phosphate?
What are the end products of glycolysis?
> Pyruvic acid (2 molecules)
> Hydrogens (4)
> ATP (2 molecules)
In the end of glycolysis, what enzyme catalyses the release of the 4 hydrogens produced?
Which steps in glycolysis is ATP used?
> glucose -> glucose-6-phosphate
> fructose-6-phosphate -> fructose-1,6-diphosphate
Which steps in glycolysis produces ATP?
1,3-diphosphoglyceric acid -> 3-phosphoglyceric acid
phosphoenolpyruvic acid -> pyruvic acid
What are the end products of pyruvic acid -> acetyl-CoA?
> acetyl-coa (2 molecules)
> hydrogens (4)
> carbon dioxide (2 molecules)
What enzyme catalyzes lactic acid formation from pyruvic acid?
pyruvic acid + NADH + H -> lactic acid + NAD
**fate of pyruvic acid when oxygen is not present**
Where does the citric acid cycle occur?
What are the end products of the citric acid cycle?
> hydrogens (16)
> ATP (2 molecules)
> carbon dioxide (4 molecules)
What is the net reaction of the citric acid cycle?
2 acetyl-coa + 6 H20 + 2 ADP --->
4 CO2 + 16 H + 2 CoA + 2 ATP
Where does oxidative phosphorylation occur?
on mitrochondrial cristae
What is the fate of hydrogen atoms from glycolysis and citric acid cycle?
> Note that hydrogens are removed in pairs.
> One member of each pair becomes a hydrogen ion.
> The other member of a pair combines with NAD -> NADH
What is the fate of electrons removed from hydrogen ions?
enter electron transport chain
What are the major components of the electron transport chain?
> several iron sulfide proteins
> ubiquinone (Q)
> cytochrome A3 (cytochrome oxidase)
- located on inner membrane
- can give up electrons to oxygen
List the steps of the chemiosmotic mechanism.
> electrons pass through chain, releasing large amounts of energy
> energy is used to pump hydrogen ions from inner matrix into outer chamber between inner and outer membranes
> high concentration of hydrogen ions created in chamber
> strong negative potential created in inner matrix
> hydrogen ions flow from high to low concentration through ATP synthetase
> energy derived from hydrogen ion flow is used by ATPase to convert ADP to ATP
> fore each 2 electrons that pass through electron transport chain, up to 3 ATP molecules are synthesized
> note that the 2 pairs of hydrogens derived from the citric acid cycle enter the electron transport chain at a later point and provide energy for 2 ATP molecules per pair
After oxidative phosphorylation, what is the number of ATPs formed per glucose molecule in each pathway?
Glycolysis - 2 ATPs
CAC - 2 ATPs
Oxidative Phosphorylation - 34 ATPs
What is the maximum number of ATPs that can be produced per glucose molecule?
How many calories are produced from 38 ATP molecules?
38 x 12,000 cal/mole = 456,000 calories/mole glucose
**456,000/686,000 = 66% efficiency**
What is the pentose phosphate pathway?
> The PPP is a cyclical pathway in which one molecule of glucose is metabolized for each revolution of the cycle.
-for every 6 glucose that enter pathway, 5 glucose are resynthesized.
> This pathway is mostly used for the synthesis of fats and other substances.
> Hydrogens generated from this pathway are bound to NADP instead of NAD.
What molecule from the PPP can be used in the synthesis of fats from carbohydrates?
NADP+ (as NADPH)
**NOT NAD+ can be used in the synthesis of fats from carbohydrates**