Lecture 8: Glucose Metabolism Flashcards Preview

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Flashcards in Lecture 8: Glucose Metabolism Deck (42):
1

What GLUT receptor is found in skeletal muscle, heart and adipose and is insulin dependent?

GLUT4

2

What GLUT receptor is the main ransporter in the liver and has low affinity with no regulation?

GLUT2

3

What GLUT transporter is the main transporter in the brain?

GLUT3

4

What GLUT transporter is high in RBCs and brain and has high affinity?

GLUT1

5

Where are glucokinase and hexokinase located?

Glucokinase is in the liver only, hexokinase is everywhere else

6

When is glucokinase inhibited?

When blood glucose is low -> it is no preferred to trap glucose in the liver so glucokinase will only be turned on in times of high glucose

7

When is DHAP made in glycolysis?

High energy state and excess glucose

- DHAP is converted to glycerol-3-phosphate then to fat

8

What is non-alcoholic fatty liver disease?

YOu have a buildup of energy and DHAP gets turned into fat

9

What stimulates pyruvate kinase?

Insulin and Fru-1,6-BP

10

What inhibits pyruvate kinase?

Alanine
ATP
Glucagon

11

What inhibits hexokinase?

Glucose-6-P

12

What stimulates glucokinase?

Glucose
Fructose-1-P
Insulin

13

What inhibits glucokinase?

Glucagon
Fructose-6-P

14

What stimulates PFK-1?

AMP
Fructose-2,6-BP

15

What inhibits PFK-1?

ATP
Citrate

16

___________ is a disaccharide of glucose and fructose

Sucrose

17

_________ is a disaccharide of glucose and galactose

Lactose

18

Where does galactose enter glycolysis?

Glucose-6-P

- Then could go onto gycogenesis if no energy is needed

19

Where does fructose from adipose tissue enter glycolysis?

Fructose-6-P

20

Where does fructose from the liver enter glycolysis?

DHAP or GAP

21

When is fructose quickly turned into fat?

In times of high energy

22

What does glucose-6-P feedback inhibit and when?

Hexokinase at times of rest

23

What is the role of glucose-6-phosphatase?

The convert GLucose-6-P to glucose in gluconeogenesis

24

Gluconeogenesis is the synthesis of glucose from noncarb precursors. What are the 3 major precursors?

Lactate, amino acids, glycerol

25

What is the rate limiting step of gluconeogenesis?

Fructose-1,6-bisphosphatase

26

What are the 4 "bypass" enzymes in gluconeogenesis?

Pyruvate carboxylase
PEPCK
Fructose-1,6-bisphosphatase
Glucose-6-phosphatase

27

What 3 enzymes in glycolysis are involved in irreversible steps?

Glucokinase/hexokinase
PFK-1
Pyruvate kinase

28

Where does gluconeogenesis occur and what is needed to get the starting materials?

Occurs in cytosol. Need to shuttle OAA out of mito by converting pyruvate -> OAA with pyruvate carboxylase then converting OAA -> Malate and malate leaves mito then is converted back to OAA in the cytosol

29

What stimulates Glucose-6-phosphatase?

Cortisol

30

What stimulates Fructose-1,6-bisphosphatase?

Citrate and cortisol

31

What inhibits fructose-1,6-bisphosphatase

AMP and fructose-2,6-BP

32

What stimulates PEPCK?

Cortisol, Glucagon, thyroxine

33

What stimulates pyruvate carboxylase?

Acetyl CoA and cortisol

34

What inhibits Pyruvate carboxylase?

ADP

35

What is Von Gierke disease?

A glycogen storage disease

- Glucose-6-phosphatase is defective so that the liver can release glucose into the blood stream resulting in fasting hypoglycemia, hyperlipidemia and damage to liver

36

In what 3 organs does gluconeogenesis occur?

Liver (mostly)
Kidneys
Small intestine

37

How much ATP is used in one round of gluconeogenesis?

6 ATP

38

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

Glucose-6-phosphate dehydrogenase (G6PD) (first step and the first time NADPH is made)

39

What inhibits G6PD in PPP?

NADPH

40

What does a deficiency in G6PD of PPP cause?

Hemolytic anemia because of deficient levels of NADPH in RBCs. Altered G6PD produces low levels of NADPH, leading to low levels of reduced glutathione in RBCs, which is needed to maintain healthy RBCs

- X-linked!
- This disorder is also called favism

41

What is the role of glutathione reductase?

Converts reversible reaction of oxidized glutathione -> reduced glutathione.

- The reduced glutathione cleans up ROS using its sulfhydril bond -> the oxidized form is formed after ROS has been picked up

42

What 4 pathways occur exclusively in the mitochondria?

TCA
Ox-phos
Beta Ox
Ketone body formation