Final: Chapter 9 Glycolysis

Question 1

What does flux refer to?

Answer 1

The rate that substrates and products (metabolites) are interconverted

Question 2

What two primary factors determine flux?

Answer 2

Level of enzyme activity and bioavailability of substrates

Question 3

When might reactions be coupled?

Answer 3

When the overall Gibbs free energy is unfavorable/nonspontaneous (positive)

Question 4

What is the structure of a monosaccharide?

Answer 4

One sugar containing an aldehyde (aldoses) or a ketone (ketoses)

Question 5

What are epimers?

Answer 5

Two monosaccharides that differ in the -OH position around one chiral carbon

Question 6

Simple sugars go through an intramolecular reaction to form what two types of rings?

Answer 6

Pyranose or furanose rings which increase structural stability

Question 7

What determines whether a simple sugar is oxidized or reduced?

Answer 7

Their functional groups

Question 8

What are reducing sugars?

Answer 8

Carbohydrates that react with oxidizing agents to promote oxidation

Question 9

What are disaccharides?

Answer 9

Two monosaccharides linked together through an O-glycosidic bond

Question 10

What type of reaction forms disaccharides?

Answer 10

Condensation reaction

Question 11

What are the three most common disaccharides?

Answer 11

Lactose, sucrose, and trehalose

Question 12

What’s one reason why shared intermediates are used effectively in coupled reactions?

Answer 12

Some metabolic enzymes are components of large multiprotein complexes. This is a type of close physical interaction that limits product diffusion and functions to “channel” shared intermediates from one enzyme to the next

Question 13

What are nonreducing sugars?

Answer 13

Sugars that cannot reduce Cu2+. Examples include sucrose and trehalose

Question 14

What is lactase?

Answer 14

A hydrolytic enzyme that is expressed in high levels in infants to aid in the digestion of lactose. Levels of lactase decline in adults

Question 15

Under what conditions does glycolysis generate ATP?

Answer 15

Anaerobic conditions

Question 16

In general, what is glycolysis?

Answer 16

The “splitting” of 1 molecule of glucose into 2 molecules of pyruvate

Question 17

How many enzymatic reaction comprise glycolysis?

Answer 17

10 reactions
(1-5) ATP investment
(6-10) ATP production

Question 18

What is the first step of glycolysis and what enzyme is involved?

Answer 18

• Glucose is phosphorylated by hexokinase or glucokinase to form glucose-6-P
• Mg2+ required
• ATP converted to ADP (ATP hydrolysis)
• Hexokinase is for all cells (broad range of substrate specificities), glucokinase (specific for glucose in the liver and pancreas)

Question 19

What enzyme is used for glucose monitoring?

Answer 19

Glucokinase

Question 20

What is the second step of glycolysis and what enzyme is involved?

Answer 20

Glucose-6-P undergoes isomerization using phosphoglucoisomerase to form fructose-6-P

Question 21

What is the third step of glycolysis and what enzyme is involved?

Answer 21

• Fructose-6-P is phosphorylated by phosphofructokinase-1 to form fructose-1,6-BP
• ATP hydrolysis
• This is the rate-limiting step!

Question 22

What is the fourth step of glycolysis and what enzyme is involved?

Answer 22

• Fructose-1,6-BP is cleaved with aldolase to form dihydroxyacetone-P
• Uses Schiff base as an intermediate

Question 23

What is the fifth step of glycolysis and what enzyme is involved?

Answer 23

DHAP (dihydroxyacetone-P) undergoes isomerization using triose phosphate isomerase to form glyceraldehyde-3-P . This is the end of the ATP investment stage.

Question 24

What is the sixth step of glycolysis and what enzyme is involved?

Answer 24

• Glyceraldehyde-3-P uses glyceraldehyde-3-P dehydrogenase (GAPDH) to transfer a phosphoryl group to it and form 1,3-biphosphoglycerate
• Produces 2 NADH

Question 25

What is the seventh step of glycolysis and what enzyme is involved?

Answer 25

- Phosphoglycerate kinase phosphorylates (substrate-level phosphorylation) 1,3-biphosphoglycerate to form 3-phosphoglycerate - 2 ATP produced

Question 26

What is the eight step of glycolysis and what enzyme is involved?

Answer 26

Phosphoglyceromutase is used which causes a phosphoryl shift in 3-phosphoglycerate to form 2-phosphoglycerate

Question 27

What is the ninth step of glycolysis and what enzyme is involved?

Answer 27

Enolase dehydrates 2-phosphoglycerate to form phosphoenolpyruvate

Question 28

What is the tenth step of glycolysis and what enzyme is involved?

Answer 28

- Pyruvate kinase phosphorylates (substrate-level phosphorylation) phosphoenolpyruvate to form pyruvate - Produces 2 ATP

Question 29

How is phosphofructosekinase-1 regulated?

Answer 29

- AMP and ADP indicate low energy charge in the cell, ATP indicates high energy charge of the cell (if there is high ATP levels, then glycolysis is not needed) - Citrate inhibits this enzyme when there is high levels of citrate (indicates that glycolysis is not needed right now to produce pyruvate)

Question 30

What is the relationship between glucose levels and production of insulin?

Answer 30

When glucose levels are high, insulin is released

Question 31

What are the three ways pyruvate is metabolized depending on availability of oxygen?

Answer 31

Aerobic conditions: ATP production (Citrate Cycle and ETC) Anaerobic conditions: Production of lactate and ethanol production

Question 32

Why is NAD+ regenerated and where is it regenerated?

Answer 32

- NAD+ is required to maintain flux through GAPDH (enzyme in the step of glycolysis that produces 2 NADH) - Regenerated in the cytoplasm

Question 33

Why are NAD+ levels inadequate in someone who has lactate dehydrogenase deficiency?

Answer 33

Lactate dehydrogenase is an enzyme that converts pyruvate to lactate and also converts NADH to NAD+. If this enzyme is deficient, the enzyme is not functional and therefore, lower levels of NAD+

Question 34

An example of an anabolic pathway is _____________. A) smaller amino acids being linked together to make a protein B) the tendency to gain or lose weight C) the burning of fat by exercise D) a protein being broken down into smaller amino acids E) none of the above

Answer 34

A) smaller amino acids being linked together to make a protein *anabolic is building :)))

Question 35

Tarui’s disease is a disorder in which phosphofructosekinase-1 deficiency occurs. Which of the following would most likely be observed in patients with this disorder? A) Fructose-6-P levels increase. B) Fructose-1,6-P levels decrease. C) ATP levels increase. D) A and B E) A and C

Answer 35

A and B