Ch 14

Question 1

How many iozymes of Hexokinase are there?

Answer 1

4

Question 2

Provide the following info on the iozymes of Hexokinase:

a. Where it is active
b. Affinity to glucose
c. Specificity

Answer 2

**Type I, II and III **
a. Muscle
b. High affinity
c. Wide range of hexoses

Type IV
a. Liver
b. Low affinity
c. Very specific for glucose

Question 3

What is the role of glucokinase for the metabolism?

Answer 3

Glucose phosphorylation in the liver

Question 4

How does the concentration of glucose affect the storage of glycogen?

Answer 4

**High [Glu] **= activates glucokinase in the liver -> glucose phosphorylation (uptake) -> glycogen stored

**Low [Glu] **= glucose is needed for muscle function = NO STORAGE

Question 5

Under which circumstances does glucose
need to be stored?
A. After exercise in muscle
B. During exercise in muscle
C. During exercise in liver
D. After a high-glucose meal in the liver and muscle

Answer 5

D

Question 6

Which isozyme is glucokinase classified as?

Answer 6

Hexokinase IV

Question 7

Glucokinase is / is not inhibited by (b).

Answer 7

a. is not
b. Glucose-6P

Question 8

How is the activity of glucokinase affected if blood sugar levels continue to increase?

Answer 8

Activity increases as long as blood sugar levels increase

Question 9

In low blood sugar, glucose levels are (a) relative to (b)

Answer 9

a. low
b. Km

Question 10

(a) in the liver generates glucose.

Answer 10

Gluconeogenesis

Question 11

What happens to glucose that has been generated in the liver?

Answer 11

Glucokinase will not phosphorylate the glucose that is made - allowing it to leave to liver to be used in tissues (muscle)

Question 12

Predict when glucose is taken up into different cells
A. Liver cells take up glucose only at high concentrations
B. Muscle cells take up glucose only at higher concentrations
C. Both cell types take up glucose at high concentrations
D. Both cell types can take up glucose at low concentration

Answer 12

C

Question 13

Is the isomerization of glucose 6-phosphate to fructose 6-phosphate reversable or irriversable?

Answer 13

Reversable

Question 14

Is the aldolase reaction favourable or non-favourable?

Answer 14

non-favourable

Question 15

What is the final step of the preparatory phase in glycolysis?

Answer 15

Interconversion of the triose phosphates with triose phosphate isomerase

Question 16

Which carbons of the original glucose are
phosphorylated in the two molecules of GAP?
A. C-1 and C-2
B. C-3 and C-4
C. C-5 and C-6
D. C-1 and C-6
E. C-1 and C-4

Answer 16

D

Question 17

What is the function of phosphoglycerate mutase in glycolysis?

Answer 17

Catalyzes a reversable shift of the phosphoryl group between C-2 and C-3 of glycerate

Question 18

Which reaction of glycolysis includes substrate-level phosphorylation?
A. Hexokinase
B. Phosphoglycerate kinase
C. Phosphofructokinase-1
D. Glyceraldehyde dehydrogenase (GAPDH)
E. Glucokinase

Answer 18

B

Question 19

Which enzyme catalyzes dehydration during glycolysis?

Answer 19

Enolase

Question 20

Which carbohydrate CANNOT be fed into the
glycolytic pathway?
A. Sucrose
B. Mannose
C. Glycogen
D. Cellulose
E. Galactose

Answer 20

D

Question 21

Why is glycolyis tightly regulated?

Answer 21

• Keep constant ATP levels
• Adequate supply of intermediates
• Generate NAD+

Question 22

How do cells achieve the regulation of glycolysis?

Answer 22

1. Regulation of enzyme activity
2. Allosteric interactions
3. Hormonal control

Question 23

Which step in glycolysis is considered the “commitment step” and which enzyme is associated with this?

Answer 23

Step 3
Phosphofructokinase (PFK)

Question 24

Predict the effect of glucose concentration on
Pyruvate kinase activity
A. Glucose inhibits pyruvate kinase
B. Glucose activates pyruvate kinase
C. Glucose does not affect pyruvate
kinase activity
D. Glucose can act as a competitive
inhibitor for pyruvate kinase.

Answer 24

B - glucose activatesbpyruvate kinase

Question 25

In the liver, ____ is inhibited by glucagon. Glucagon activates ____ which phosphorylates ____

Answer 25

Pyruvate Phosphokinase A pyruvate kinase

Question 26

GAP + Pi + NAD+ → 1,3 PGA + NADH+ H+ Which reaction is this necissary for?

Answer 26

Glycolysis

Question 27

What happens to the GAPDH reaction if 2,3BPG and NADH+ H+ accumulate?

Answer 27

Thw GAPDH reaction will be inhibited or slowed down

Question 28

# Catabolic fates of pyruvate What happens to pyruvate under Aerobic Conditions?

Answer 28

**Oxidized **to acetyl-CoA via TCA cycle

Question 29

# Catabolic fates of pyruvate What happens to pyruvate under Anaerobic conditions (hypoxia)

Answer 29

**Reduced** to lactate or ethanol

Question 30

# Fill in the blanks Under ____ conditions, glycolysis stops until ____ can be replenished by ____

Answer 30

Anaerobic NAD+ Fermentation

Question 31

# Fill in the blanks Under ____ conditions, NAD+ is registered by ____

Answer 31

Aerobic Mitochondrial electron transfer

Question 32

____ must be recycled to regenerate NAD+

Answer 32

NADH

Question 33

What is fermentation

Answer 33

Process that extracts energy (as ATP) but does NOT consume O2 or change [NAD+] or [NADH]

Question 34

What happens during Ethanol fermentation. What is it performed by?

Answer 34

- Performed by yeast - Pyruvate is further catobolized to ethanol - Regenerated the NAD+ necissary for glycolysis - Produces CO2

Question 35

What are the products of ethanol fermentation

Answer 35

CO2 and NAD+

Question 36

What happens during lactic acid fermentation?

Answer 36

Pyruvate accepts electrons from NADH and is reduced to lactate

Question 37

What are the products of Lactic Acid fermentation

Answer 37

Regenerates NAD+ necessary for glycolysis

Question 38

____ and other microorganisms regenerate ____ by ____ pyruvate to ____ and ____

Answer 38

Yeast NAD+ Reducing Ethanol and CO2

Question 39

Explain what happens when you are fasting / exercising.

Answer 39

- Need for glucose increases - Glc can be synthesized from Lactate, Pyruvate Ala, Glycerol - Can be synthesized in Liver

Question 40

Besides the liver, where else can the synthesis of glucose take place?

Answer 40

Renal Cortex and Epithelium of small intestine

Question 41

**How are glycolysis, ethanol fermentation, and lactate fermentation related?** A. All are regulated by the ATP/ADP mass-action ratio. B. All three produce carbon dioxide. C. All can proceed in the absence of oxygen. D. All require pyruvate. E. All three produce NADH.

Answer 41

C - glycolysis is anaerobic - Both ethanol and lactate fermentation are anaerobic pathways that allow the regeneration of NAD+

Question 42

**The rate of glucose consumed under anaerobic conditionsis much greater than that under aerobic conditions ** A. True B. False C. True, but only in plants and bacteria D. True, but only in animals E. Not sure, insufficient information

Answer 42

A

Question 43

Amino acids can serve as precursors for ____

Answer 43

Glucose synthesis

Question 44

**Gluconeogenesis (synthesis of glucose) is glycolysis backwards.** A. True B. False

Answer 44

False - Glucolysis has three irreversible steps catalyzed by Hexokinase, PFK-1 and Pyruvate kinase - Gluconeogenesis uses different enzymesypass these steps * Glucose-6-phosphatase instead of hexokinase * Fructose 1,6-biphisphatase instead of PFK-1 * Pyruvate carboxylase instead of pyruvate kinase

Question 45

# When you exercise: 1: Within seconds, use up your ____ 2: Within minutes, ____ reserves used up 3: Next, you dip into your ____ stores 4: Produce ____ in muscle 5: Accumulation of ____ which is a ____ intermediate

Answer 45

1: ATP stores 2: Creatine-P 3: Glycogen 4: Lactate 5: Lactate, dead end

Question 46

What happens when **lactate** is produced in the muscle?

Answer 46

1 - Transported to liver 2 - converted to glucose via Gluconeogenesis 3 - Glucose shipped to muscle 4 - Degraded to lactate 5 - Transported to liver

Question 47

**Is the lactate dehydrogenase reaction reversible?** A. Yes B. No C. Depends on the enzyme

Answer 47

Yes

Question 48

Via which process is lactate converted to glucose?

Answer 48

Gluconeogenesis

Question 49

Which cycle is used to cycle lactate from the muscles?

Answer 49

Cori cycle

Question 50

How does glucose enter a cell?

Answer 50

* Active transport * Passive transport * Simple Diffusion * Ion channel

Question 51

Glycolysis happens in ____, whereas remainder of pyruvate oxidation happens in the ____

Answer 51

Cytosol Mitochondrial matrix

Question 52

Glycolysis does not require ____, but ____ does

Answer 52

Oxygen Complete oxidation of glucose

Question 53

Glycolysis happens in virtually all cell types, but gluconeogenesis is performed mustly by ____ and to some extent ____

Answer 53

Liver cells Kidney cells

Question 54

How is hexokinase regulated?

Answer 54

Allosterically