Lecture 17: Energy Balance and Metabolism I Flashcards Preview

Human Physiology 2 - Unit 2 - Zach H. > Lecture 17: Energy Balance and Metabolism I > Flashcards

Flashcards in Lecture 17: Energy Balance and Metabolism I Deck (68)
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1

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)

2

What does galactose, glucose, and fructose get converted to to enter the glycolytic pathway?

Fructose-6-Phosphate

3

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)

4

In the uptake of glucose, what does the presence of insulin do?

increases glucose transport x10

5

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**

6

What factors can activate phosphorylase?

> epinephrine (from adrenal gland)
> glucagon (from alpha cells of pancreas)

7

In glycogenesis and glycogenolysis, what are the effects of phosphorylase?

> promotes conversion of glycogen to glucose
> glucose can then be released into blood

8

What enzyme does glycogen -> glucose-1-phosphate?

phosphorylase

9

What enzyme does glucose-6-phosphate -> blood glucose?

phosphatase

10

What enzyme does blood glucose -> glucose-6-phosphate?

glucokinase

11

What are the end products of glycolysis?

> Pyruvic acid (2 molecules)
> Hydrogens (4)
> ATP (2 molecules)

12

In the end of glycolysis, what enzyme catalyses the release of the 4 hydrogens produced?

dehydrogenase

13

Which steps in glycolysis is ATP used?

> glucose -> glucose-6-phosphate
> fructose-6-phosphate -> fructose-1,6-diphosphate

14

Which steps in glycolysis produces ATP?

1,3-diphosphoglyceric acid -> 3-phosphoglyceric acid

phosphoenolpyruvic acid -> pyruvic acid

15

What are the end products of pyruvic acid -> acetyl-CoA?

> acetyl-coa (2 molecules)
> hydrogens (4)
> carbon dioxide (2 molecules)

16

What enzyme catalyzes lactic acid formation from pyruvic acid?

lactic dehydrogenase

pyruvic acid + NADH + H -> lactic acid + NAD

**fate of pyruvic acid when oxygen is not present**

17

Where does the citric acid cycle occur?

mitochondrial matrix

18

What are the end products of the citric acid cycle?

> hydrogens (16)
> ATP (2 molecules)
> carbon dioxide (4 molecules)

19

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

20

Where does oxidative phosphorylation occur?

on mitrochondrial cristae

21

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

22

What is the fate of electrons removed from hydrogen ions?

enter electron transport chain

23

What are the major components of the electron transport chain?

> flavoprotein
> several iron sulfide proteins
> ubiquinone (Q)
> cytochrome A3 (cytochrome oxidase)
- located on inner membrane
- can give up electrons to oxygen

24

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

25

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

26

What is the maximum number of ATPs that can be produced per glucose molecule?

38

27

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**

28

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.

29

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**

30

Where is excess glucose broken down by PPP?

liver

**producing excess NADPH**