Glycolysis

Question 1

What is gain of electrons called?

Answer 1

Reduction

Question 2

What is loss of electrons called?

Answer 2

Oxidation

Question 3

What bonds in ATP provide cellular energy?

Answer 3

High-energy phosphate bonds between 2nd and 3rd phosphates only (not bond between phosphate and sugar!)

Question 4

Where does glycolysis take place?

Answer 4

Cytoplasm

Question 5

What is standard free energy?

Answer 5

ΔGo - the free energy that is released when reactants are at a standard state concentration (1M) and are allowed to come to equilibrium

Question 6

What will happen in a reaction if ΔG < 0?

Answer 6

Reaction will proceed forward

Question 7

What will happen in a reaction if ΔG > 0?

Answer 7

Reaction will go backwards

Question 8

What will happen in a reaction if ΔG = 0?

Answer 8

Reaction will stay at equilibrium - no change

Question 9

D-Glucose –> Glucose 6-phosphate
(Step 1)

What enzyme? What is significant? Significant products?

Answer 9

Glucokinase - in liver and pancreas
Hexokinase - in muscle

Exergonic reaction - highly favorable, regulated step

Lose ONE ATP

Question 10

Glucose 6-phosphate –> Fructose 6-phosphate
(Step 2)

What enzyme? What is significant? Significant products?

Answer 10

Phosphoglucose Isomerase

Isomerization - very little change

Question 11

Fructose 6-phosphate –> Fructose 1,6-biphosphate (Step 3)

What enzyme? What is significant? Significant products?

Answer 11

PFK - phosphofructose kinase

Highly regulated by metabolites/hormones

Lose ONE ATP

Question 12

What kinds of signals inhibit PFK?

Answer 12

ATP-like signals (like citrate)

Question 13

What kinds of signals stimulate PFK?

Answer 13

AMP-like signals (like fructose 2,6-bisphosphate or F2,6-BP)

Question 14

Fructose 1,6-biphosphate –> Dihydroxyacetone phosphate –> Glyceraldehyde 3-phosphate
(Step 4)

What enzyme? What is significant? Significant products?

Answer 14

Fructose bisphosphate aldolase and Triosephosphate isomerase

Isomerization step - little change

Question 15

Glyceraldehyde 3-phosphate –> 1,3-bisphosphoglycerate
(Step 5)

What enzyme? What is significant? Significant products?

Answer 15

(GAPDH) Glyceraldehyde phosphate dehydrogenase

Creates high-energy phosphate bond by replacing high-energy thioester bond and using Mg2+ cofactor

Creates TWO NADH

Question 16

1,3-bisphosphoglycerate –> 3-phosphoglycerate
(Step 6)

What enzyme? What is significant? Significant products?

Answer 16

PGK (3-phosphoglycerate kinase)

Uses Mg2+ cofactor

Creates TWO ATP

Question 17

Phosphoenol pyruvate (PEP) --> Pyruvate
(last step)

What enzyme? What is significant? Significant products?

Answer 17

Pyruvate Kinase

Last, irreversible step of glycolysis

Creates TWO ATP

Question 18

What are the functions of skeletal muscle?

Answer 18

Provide normal mvt, respond to stress w/ continued work output, adapt to short periods of anaerobic work

Question 19

What is skeletal muscle’s metabolic role?

Answer 19

Generate ATP to drive muscle contraction, store food locally for immediate need, take metabolic precursors from other organs, serve as storage site for proteins

Question 20

What is function of liver?

Answer 20

Regulates blood glucose, (absorbs excess glucose in fed state, makes glucose during fasted state), Responds metabolically to higher level hormonal control

Question 21

What is liver’s metabolic role?

Answer 21

Store glucose as glycogen, convert excess energy to fat, convert and break down metabolites

Question 22

What are the stimulatory and inhibitory signals in energy generation?

Answer 22

Stimulatory - low-energy AMP- like signals

Inhibitory - high-energy, ATP-like signals

Question 23

What are the stimulatory and inhibitory signals in food storage?

Answer 23

Activators - ATP-like

Inhibitors - AMP-like

Question 24

High levels of what molecule indicate that glycolysis is backed up? Why?

Answer 24

Glucose 6-phosphate - this molecule normally serves as feedback inhibition for hexokinase or glucokinase

Question 25

What does hexokinase's low Km say about its function?

Answer 25

It will be saturated at normal glucose levels in blood so muscles can get glucose regularly

Question 26

What does glucokinase's high Km say about its function?

Answer 26

Since it is in the liver, its job is to ensure blood glucose levels are regulated properly, thus it will only be saturated when blood glucose levels are very high

Question 27

Describe hormonal regulation of PFK in liver.

Answer 27

1) High insulin/glucagon ratio causes decreased cAMP and reduced levels of protein kinase A. 2) Decreased protein kinase A favors dephosphorylation of PFK-2/FBP-2. 3) Dephosphorylated PFK-2 is active, whereas FBP-2 is inactive so fructose 2,6-bisphosphate forms. 4) Elevated fructose 2,6-bisphosphate activates PFK-1 which increases rate of glycolysis.

Question 28

Describe hormonal regulation of PFK in skeletal muscle.

Answer 28

1) Epinephrine binds Beta-adrenergic receptor which causes decreased cAMP and protein kinase A levels. 2) Decreased protein kinase A favors dephosphorylation of PFK-2/FBP-2 at a different site, forming a distinct isoform of PFK-2 that does not lead to its deactivation. 3) Fructose 2,6-bisphosphate forms. 4) Elevated fructose 2,6-bisphosphate activates PFK-1 which increases rate of glycolysis.

Question 29

What is the Cori Cycle?

Answer 29

Exercising muscles convert glucose to lactate. This lactate is taken up by the liver and reconverted to glucose using ATP (via gluconeogenesis). Glucose is released back into circulation

Question 30

What are the four potential fates of pyruvate?

Answer 30

1. Ethanol fermentation (anaerobic) 2. TCA cycle (anaplerotic rxn, gluconeogenesis) - becomes oxaloacetate 3. Anaerobic metabolism - becomes lactate 4. TCA cycle (energy) - becomes Acetyl CoA

Question 31

Which reaction of glycolysis is highly exergonic and favorable?

Answer 31

Glucose --> Glucose 6-phosphate (using hexokinase or glucokinase)

Question 32

How is PFK regulated by F26BP?

Answer 32

F26BP is an AMP-like signal that activates PFK and inhibits F1,6-BPase, upregulating glycolysis.

Question 33

What reaction can happen if someone lives at a high altitude? What enzymes are involved?

Answer 33

Mutase can convert 1-3 BPG to 2,3-BPG which binds to Hg and increases O2 off-loading to tissues. Phosphatase will get it back to 3-phosphoglycerate.

Question 34

What are the net products of aerobic glycolysis?

Answer 34

2 NADH, 2 ATP, 2 pyruvate

Question 35

How is pyruvate kinase regulated metabolically? Hormonally?

Answer 35

1) Metabolically: F 1,6-BP feed-forwards/activates PK 2) Hormonally: In liver, glucagon signaling increases CAMP levels, which increase PKA levels, which deactivates pyruvate kinase

Question 36

What are the net products of anaerobic glycolysis?

Answer 36

2 ATP, 2 lactate

Question 37

What enzyme is involved in anaerobic glycolysis?

Answer 37

Lactate dehydrogenase

Question 38

What molecule is recycled in anaerobic glycolysis?

Answer 38

NADH