Chapter 9 - Carbs Metabolism I

Question 1

What is an average blood glucose concentration?

Answer 1

100mg/dL

5.6mM

Question 2

GLUT 2 transporter

Answer 2

In hepatocytes and pancreatic cells

*captures excess glucose (mainly for storage)

Question 3

GLUT 4

Answer 3

Adipose tissue and muscle

**responds to glucose [ ] in peripheral blood

**increased by insulin

Question 4

Hexokinase vs glucokinase

Answer 4

Gluc:

• liver and some pancreatic b-cells
• induced by insulin in hepatocytes
• high km

Hexo:

• present in most tissues
• low km
• inhibited by g6p

Question 5

What is the main control point of glycolysis ?

Answer 5

PFK1

*inibited by citrate/atp

Question 6

How do insulin and glucagon affect PFK1?

Answer 6

Insulin stimulates
Glucagon inhibits

**through PFK2

Question 7

Tell me about glyceraldehyde-3-phosphate dehydrogenase

Answer 7

Catalyses oxidation and addition of Pi to its substrate: glyceraldehyde 3phosphate

Reduces NAD+ to NADH

Question 8

3-phosphoglycerate kinase…whatup

Answer 8

Transfers phosphate from 1,3bisphosphoglycerate to ADP

**forms ATP and 3-phosphoglycerate

**substrate level phosphorylation

Question 9

Pyruvate kinase

Answer 9

Feed- forward activation by PFK1 reaction

Question 10

Main enzyme in fermentation for mammals

Answer 10

Lactate dehydrogenase

Question 11

Purpose of fermentation in mammals

Answer 11

Regenerate NAD+

Reduces pyruvate to lactate

Question 12

What are the irreversible enzymes of glycolysis ?

Answer 12

• hexo/glucokinase
• phosphofructokinase
• pyruvate kinase

Question 13

What is the effect of 2,3-BPG?

Answer 13

Shifts Bohr model to right

**causes higher km, increased unloading

Question 14

What disaccharide is fructose part of?

Answer 14

Sucrose

Fructose and glucose

Question 15

What are the products of fructose metabolism?

Answer 15

DHAP and GAP

** quick source of energy because it is downstream of PFK1

Question 16

Is PDH reversible?

Answer 16

No, can’t go from acetyl coa to pyruvate / glucose

Question 17

What is the effect of insulin on PDH?

Answer 17

PDH in liver is activated by insulin

• high insulin levels signal to liver that individual is in well fed state
• > so store as fat (and burn glucose)

Question 18

What are the two main fates of Acetyl-CoA?

Answer 18

TCA -> H20 and CO2

Fatty Acids (through fatty acid synthesis)

Question 19

What do you called the synthesis of glycogen granules?

Answer 19

Glycogenesis

Question 20

What is the rate limiting step of glycogen synthesis?

Answer 20

Glycogen synthase:

• forms a-1,4 glycosidic bond

Stimulated by glucose6phosphate and insulin

Inhibited by epi and glucagon

Question 21

Important enzymes for gluconeogenesis

Answer 21

Pyruvate carboxylase

PEPCK

Fructose 1,6 - bisphosphate

Question 22

What are the two major functions of the pentose phosphate pathway?

And where does it occur?

Answer 22

1) production of NADPH
2) serves as sources of ribose 5-phosphate for nucleotide synthesis

**happens in the cytoplasm

Question 23

What is the rate limiting enzyme of the pentose phosphate pathway?

Answer 23

Glucose-6-phosphate dehydrogenase (G6PD)

*induced by insulin

Question 24

What is the difference between NADH and NADPH?

Answer 24

NAD+ is a high energy electron acceptor

NADPH is strong reducing agent

• use for biosynthesis of fatty acids and cholesterol
• acts as an antioxidant (through glutathione)

NAD+/NADH = 1000

NADP+/NADPH = 0.1

Question 25

What are the two phases of Pentose phosphate pathway?

Answer 25

Oxidative : starting with G6P , NADPH is produced! Non-oxidative phase: - ribose 5 phosphate is produced - inter conversion of various sugars

Question 26

Where does the pentose phosphate pathway begin? (Assuming starting from glycolysis)

Answer 26

Glucose 6 phosphate gets shunted to the PPP