Lecture 20: Glycolysis

Question 1

What is the only fuel RBCs can use, and that the brain uses under conditions of non starvation

Answer 1

Glucose

Question 2

GLUT1 expressed/affinity

Answer 2

It is ubiquitous, but mostly expressed in brain and RBCs- high affinity

Question 3

GlUT2 expressed/affinity

Answer 3

Liver - low affinity

Question 4

GLUT3 expressed/affinity

Answer 4

Neurons- high affinity

Question 5

GLUT4 expressed/dependence

Answer 5

Skeletal muscle, heart, adipose tissue

-Insulin dependent

Question 6

Glycolysis occurs where

Answer 6

Cytoplasm

Question 7

ATP use in stage one glycolysis

Answer 7

No ATP generated

2 ATP consumed

Question 8

Step one of stage one glycolysis

Answer 8

Glucose phosphorylated to G6P by hexokinase (all tissues) and glucokinase (liver)
ATP consumed

Question 9

Step two stage one glycolysis

Answer 9

G6P isomerized to F6P by phosphoglucoisomerase

Question 10

Step three stage one glycolysis

Answer 10

F6P phosphorylated to F1,6BP by phosphofructokinase
ATP consumed
Rate limiting step

Question 11

Step four stage one

Answer 11

F16BP –> GAP and DHAP by Aldolase

Question 12

Step five stage one

Answer 12

DHAP –> GAP by triose phosphate isomerase

Question 13

Step one stage two

Answer 13

GAP –> 1,3BPG by GAP dehydrogenase

NADH made

Question 14

Step two/three stage two

Answer 14

1,3BPG – 3PG by phosphoglycerate kinase

3PG–> 2PG by phosphoglycerate isomerase

Question 15

Step four stage two

Answer 15

2PG –> PEP by enolase

ATP made x2

Question 16

Step five stage two

Answer 16

PEP —> pyruvate

ATP made x2

Question 17

Where does galactose enter glycolysis

Answer 17

It is converted to Glucose-6-phosphate

Question 18

Where does fructose enter

Answer 18

It is converted to Fructose 1 phosphate and then to Glyceraldehyde and DHAP and then to G3P

Question 19

Steps in fructose to G3P

Answer 19

Fructose–> F1P by fructokinase
F1P–> Glyceraldehyde + DHAP by F1P aldolase
Glyceraldehyde+DHAP–> G3P by triose kinase

Question 20

Galactose 1 phosphate requires what other substrate and enzyme to convert it into ____

Answer 20

Requires UDP glucose and galactose 1 phosphate uridyl transferase to convert it into UDP Galactose and Glucose 1 phosphate

Question 21

Glucose 1 phosphate is converted into what by what enzyme

Answer 21

Glucose 6 phosphate by phosphoglucomutase

Question 22

Major regulatory enzymes of glycolysis include

Answer 22

Hexokinase
Phosphofructokinase
Pyruvate kinase

Question 23

Goal of glycolysis regulation in liver vs muscle

Answer 23

Liver- maintain blood glucose levels/provide building blocks for other pathways
Skeletal muscle- Generate ATP for energy

Question 24

Phosphofructokinase is activated/inhibited by what

Answer 24

Activated by Fructose 2,6 biphosphate F26BP

Inhibited by citrate

Question 25

Pyruvate kinase is regulated by

Answer 25

Allosteric effectors and covalent modification

Question 26

Why can uptake of excess fructose lead to obesity

Answer 26

Because Fructose is converted to G3P and DHAP which are processed into acetyl CoA and eventually fatty acids, without being regulated by phosphofructokinase because that step is skipped

Question 27

What causes Galactosemia

Answer 27

Deficiency in Galactose-1-phosphate uridyl transferase

Question 28

What enzyme converts galactose to galactitol which causes cataracts

Answer 28

Aldose reductase

Question 29

What is Warburg effect

Answer 29

When rapidly growing tumor cells metabolize glucose to lactate, even in the presence of oxygen
This is called aerobic glycolysis