Glycolysis

Question 1

What is the function of glycolysis?

Answer 1

To break down glucose

Question 2

What are the products of glycolysis?

Answer 2

ATP, NADH, pyruvate, lactate, and alanine

Question 3

In aerobic organisms, glycolysis yields precursors to what?

Answer 3

The aerobic system

Question 4

What is the first half of glycolysis characterized by?

Answer 4

• Bringing glucose into the cell (Facilitated diffusion and adding a phosphate to prevent it from leaving)
• Change glucose into an energy rich sugar (fructose 1, 6 bisphosphate)

Question 5

What is the second half of glycolysis characterized by?

Answer 5

• Getting ATP

- Creating an end product that can be further oxidized (pyruvate)

Question 6

Where does glycolysis take place?

Answer 6

Cytosol

Question 7

The first half of glycolysis begins with phosphorylation of glucose by hexokinase. What is the product of this reaction?

Answer 7

Hexokinase adds a phosphate group to glucose, which prevents it from leaving the cell. (glucose to glucose 6-phosphate)

Question 8

Isomerization of glucose 6-phosphate by phosphoglucose isomerase is the second step in the first half of glycolysis. What is the product of this reaction?

Answer 8

It converts glucose 6-phosphate to fructose 6-phosphate (aldehyde to a ketone)

Question 9

In the first half of glycolysis, there is a second round of phosphorylation by phosphofructokinase (PFK) after isomerization. What is the product of this reaction?

Answer 9

It converts fructose 6-phosphate to fructose 1, 6-bisphosphate

Question 10

This term is used to describe the influencing of an enzyme activity by a change in the conformation of the enzyme, brought about by the noncompetitive binding of a nonsubstrate at a site (allosteric site) other than the active site of the enzyme.

Answer 10

Allosterism

Question 11

This is an allosteric enzyme, very influential, and acts during the rate limiting step in glycolysis.

Answer 11

Phosphofructokinase (PFK)

Question 12

In general, what reactions occur in the first half of glycolysis?

Answer 12

• Phosphorylation (glucose to glucose 6-phosphate)
• Isomerization (glucose 6-phosphate to fructose 6-phosphate)
• Phosphorylation (fructose 6-phosphate to fructose 1,6-bisphosphate

Question 13

In the second half of glycolysis there is a split that occurs. How does this happen and what molecules are involved?

Answer 13

Fructose 1,6-bisphosphate is split by aldolase into dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3 phosphate (G3P)

Question 14

After the split in the second half of glycolysis, DHAP and G3P undergo isomerization via what enzyme? What is produced?

Answer 14

Triose phosphate isomerase. Two pyruvate molecules are made for every glucose broken down

Question 15

After isomerization in the second half of glycolysis, G3P is converted to 1, 3-Bisphosphoglycerate via what reaction? What enzyme does this?

Answer 15

Oxidative phosphorylation via G3P dehydrogenase

Question 16

After oxidative phosphorylation, ATP is created by converting 1,3-Bisphophoglycerate into ____ via ____.

Answer 16

3-Phosphoglycerate via phosphoglycerate kinase

Question 17

This is the process by which a phosphate group is being provided by the initial substrate to help make ATP.

Answer 17

Substrate level phosphorylation

Question 18

After ATP is created during the second half of glycolysis, 3-Phosphoglycerate is converted into ____ via ____. This process is known as what?

Answer 18

2-Phosphoglycerate via phosphoglycerate mutase. This process is known as mutation

Question 19

After mutation occurs in the second half of glycolysis, 2-Phosphoglycerate is converted into ___ via ___. This process is known as what?

Answer 19

Phosphoenolpyruvate via enolase. This process is known as dehydration

Question 20

After dehydration occurs in the second half of glycolysis, phosphoenolpyruvate is converted into ____ via ____. Is this reaction reversible or irreversible?

Answer 20

Pyruvate via pyruvate kinase. This is an irreversible reaction. ATP is produced at this step

Question 21

What are some other substances can enter into the glycolytic pathway?

Answer 21

Sucrose (glucose and fructose) and Lactose (glucose and galactose)

Question 22

Fructose can be phosphorylated into ____ by ____.

Answer 22

Fructose 6P by hexokinase

Question 23

After fructose is phosphorylated, it could enter glycolysis, but it doesn’t happen much. Why?

Answer 23

Hexokinase’s affinity for glucose is 20 times higher than its affinity for fructose

Question 24

What are the steps of the fructose 1-phosphate pathway?

Answer 24

• Fructose is converted to fructose 1P by fructokinase
• Fructose 1P is broken down into glyceraldehyde and dihydroxyacetone phosphate by fructose 1P aldolase
• Glyceraldehyde is then converted to glyceraldehyde 3P by triose kinase

Question 25

How is galactose converted into glucose 6P?

Answer 25

1. Galactose + ATP-->galactose 1P and ADP (galactokinase) 2. Galactose 1P + UDP (uridine diphosphate) Glucose --> UDP-Galactose + Glucose 1P (transferase 3. UDP Galactose --> UDP Glucose (epimerase) 4. Glucose 1P --> Glucose 6P (mutase)

Question 26

How is phosphofructokinase inhibited?

Answer 26

- Binding of ATP decreases its activity - Decreased pH - Citrate

Question 27

How does fructose 2,6-bisphosphate influence phosphofructokinase (PFK)?

Answer 27

It is made from fructose 6P and activates PFK and subsequent glycolysis. In addition to this it inhibits gluconeogenesis

Question 28

What is the main role of hexokinase in glycolysis?

Answer 28

It is the enzyme that catalyzes the first step in glycolysis

Question 29

What enzyme inhibits hexokinase?

Answer 29

Phosphofructokinase

Question 30

This is an alternative form of hexokinase that is found in liver and Beta cells of the pancreas. It also makes G6P only if glucose is abundant.

Answer 30

Glucokinase

Question 31

What are the differences between glucokinase and hexokinase?

Answer 31

Glucokinase: found in the liver, high Km, not inhibited by glucose 6P, stimulated by insulin and fructose Hexokinase: found in the muscle, low Km, inhibited by glucose 6P

Question 32

What are the four important things to know about glucokinase?

Answer 32

- Stimulated by insulin - Stimulated by fructose - High Km (takes more reactant to make it go faster) - It is not inhibited by its product (glucose 6P)

Question 33

This enzyme catalyzes the third "irreversible" step in glycolysis, its stimulated by fructose 1, 6 BP, and it is feedforward to allow it to keep up with the oncoming intermediates.

Answer 33

Pyruvate kinase

Question 34

This amino acid is one reaction away from becoming pyruvate.

Answer 34

Alanine

Question 35

Pyruvate kinase is stimulated by ____ and inhibited by ____.

Answer 35

Stimulated by fructose 1,6-bisphosphate | Inhibited by ATP or alanine

Question 36

This hormone is secreted when blood glucose is low and is used to elevate blood glucose.

Answer 36

Glucagon

Question 37

How is lactic acid produced?

Answer 37

Pyruvate is converted into lactate by lactate dehydrogenase and the conversion of NADH + H+ to NAD+

Question 38

What is the important reaction that lactate dehydrogenase is utilized in?

Answer 38

Pyruvate + NADH ---> Lactate + NAD+

Question 39

This substance is produced when glycolysis runs fast.

Answer 39

Lactic acid

Question 40

A moderate production of lactate does what to glycolysis? A large production?

Answer 40

Moderate: speeds up glycolysis Large: inhibits glycolysis

Question 41

This process is characterized by the conversion of glucose to lactic acid in the presence of oxygen (Warburg effect) and is uniquely observed in cancers.

Answer 41

Aerobic glycolysis

Question 42

By running glycolysis fast, what type of intracellular and pericellular conditions are created?

Answer 42

Acidic conditions

Question 43

This is an ATP-generating process in which organic compounds act as both donors and acceptors of electrons. This process can occur in the absence of oxygen.

Answer 43

Fermentation