Chapter 9 Glycolysis

Question 1

What is metabolism?

Answer 1

The collection of biochemical reactions in a free-living organism that convert chemical energy into work

Question 2

What is glycolysis?

Answer 2

The catabolic pathway of glucose oxidation to pyruvate. One glucose molecule enters the pathway to yield two molecules of pyruvate, two ATP, and two NADH

Question 3

True or false: catabolic and anabolic pathways are active in the body at the same time

Answer 3

true

Question 4

Catabolism

Answer 4

leads to the degradation of macromolecules and nutrients for the purpose of energy capture (NADH and FADH2 formation)

Question 5

Anabolism

Answer 5

use energy available from ATP hydrolysis and the oxidation of reducing equivalents (NADH, FADH2) to synthesize biomolecules

Question 6

What two factors determine metabolic flux?

Answer 6

1. level of enzyme activity
2. level of substrates

Question 7

What is flux?

Answer 7

The rate at which substrates and products (metabolites) are interconverted

Question 8

mass action ratio

Answer 8

the ratio of the concentration of the product over the concentration of substrate, under actual conditions in a cell; used to calculate delta G for a rxn

Question 9

True or false: monosaccharides exist in equilibrium between linear and cyclic forms

Answer 9

true

Question 10

Do most sugars exist in the D or L conformation?

Answer 10

D-conformation

Question 11

What is cyclical glucose known as?

Answer 11

glucopyranose

Question 12

What is Benedict’s Test?

Answer 12

a method for detecting the presence of reducing sugars in solution on the basis of reduction of cupric ion ( Cu 2+) to generate red couprous (Cu+)

Question 13

reducing sugar vs. nonreducing sugar

Answer 13

reducing sugar: carb that reduces an oxidizing agent; generally aldoses (ex. glucose)

nonreducing sugar: a carb that is unable to reduce an oxidizing agent (ex. sucrose)

Question 14

What is an O-glycosidic bond?

Answer 14

the covalent bond that links two monosaccharides together through oxygen; can be alpha (down) or beta (up) configuration

Question 15

What is the net equation of glycolysis?

Answer 15

glucose + 2 NAD+ + 2 ADP + 2 P <—-> 2 pyruvate + 2 NADH + 2 H+ + 2ATP + 2 H2O

Question 16

What are the two stages of glycolysis?

Answer 16

Stage 1: ATP investment (reactions 1-5)
Stage 2: ATP production (reactions 6-10)

Question 17

What conditions does glycolysis occur under?

Answer 17

anaerobic conditions; it is the primary pathway for ATP generation for cells that lack mitochondria, like erythrocytes

Question 18

How does glycolysis use free energy?

Answer 18

the process involves multiple coupled reactions in order to be overall energetically favorable

Question 19

What are the three main favorable steps of glycolysis?

Answer 19

Steps 1,3, and 10

Question 20

What are the three key enzymes of glycolysis?

Answer 20

hexokinase (step 1)
phosphofructokinase-1 (step 3)
pyruvate kinase (step 10)

Question 21

What is the rate-limiting step of glycolysis and how is it regulated?

Answer 21

Step 3, the conversion of fructose-6-P to fructose-1,6-BP via phosphofructokinase-1, is the rate-limiting step. This enzyme is inhibited by high concentrations of ATP and citrate in a negative feedback loop.

Question 22

What inhibits hexokinase?

Answer 22

glucose-6-P

Question 23

What inhibits PFK-1?

Answer 23

ATP and citrate

Question 24

What inhibits pyruvate kinase?

Answer 24

ATP and acetyl-CoA

Question 25

Where does glycolysis occur?

Answer 25

the cytoplasm

Question 26

What steps of glycolysis produce ATP?

Answer 26

Step 7 produces 2 ATP
Step 10 produces 2 ATP

ATP is produced in the steps that involve substrate-level phosphorylation. Step 7, the conversion of 1,3-bisposphoglycerate to 3-phosphoglycerate via phosphoglycerate kinase, produces 2 ATP. Step 10, the conversion of phosphoenolpyruvate to pyruvate via pyruvate kinase, produces 2 ATP.

Question 27

What steps of glycolysis uses ATP?

Answer 27

Step 1 and Step 3 each use one ATP
Step 1 requires ATP to phosphorylate glucose to glucose-6-P.
Step 3 requires ATP to phosphorylate fructose-6-P to fructose-1,6-BP

Question 28

What molecules are indicators of low energy in the cell?

Answer 28

AMP and ADP

Question 29

Describe the basics of insulin signaling

Answer 29

• entry of glucose into pancreatic beta cells stimulates glucokinase
• ATP synthesis is increased
• increased [ATP] inhibits potassium channels, depolarizing the cell membrane
• Ca 2+ enters the cell after its voltage-gated ion channel is activated
• Ca 2+ stimulates insulin vesicles to fuse with the plasma membrane
• insulin is released

Question 30

What are the consequences of a deficiency in fructose-1-P?

Answer 30

Fructose intolerance; accumulation of F1P leads to liver damage and ATP depletion.

A serious genetic malady caused by the inability to make aldolase B, an enzyme that catalyzes the reversible reaction fructose-1-phosphate to glyceraldehyde and dihydroxyacetone phosphate.

Question 31

What can the end product of glycolysis be used for besides entering the Citrate Cycle?

Answer 31

Pyruvate can be converted into glucose via gluconeogenesis, used to synthesize fatty acids via Acetyl-CoA, converted into amino acids, or fermented into lactate or ethanol.

Question 32

What step of glycolysis produces reducing agents?

Answer 32

Step 6, the conversion of G3P to 1,3-bisphosphoglycerate via GAPDH, produces reducing power in the form of NADH.

Question 33

What is the cleavage step in glycolysis?

Answer 33

Step 4 uses an aldolase to cleave fructose-1,6-BP into glyceraldehyde-3-P and dihydroxyacetone-P, which is then isomerized into glyceraldehyde-3-P in Step 5. Each molecule undergoes Steps 6-10, resulting in 1 pyruvate and 2 ATP per G3P.