Carbohydrates Flashcards Preview

Biochemistry > Carbohydrates > Flashcards

Flashcards in Carbohydrates Deck (49):
1

What type of cells only use glucose for energy

RBC's and brain cells

2

De novo synthesis

gluconeogenesis in the liver

3

GLUT1

ubiquitous but high in RBC's and brain, high affinity

4

GLUT2

Main transporter in liver, low affinnity

5

GLUT3

Main transporter in neurons, High affinity

6

GLUT4

present in skeletal muscle, adipose tissue. Insulin Dependent

7

GLUT5

Fructose transporter

8

How many ATP and NADH are produced by glycolosis

2 ATP, 2 NADH, 2 Pyruvate

9

Difference between Hexokinase and Glucokinase

Hexokinase is in all cells, high affinity and inhibited by G6P,
Glucokinase: in liver and pancreatic B cells, low affinity, weakly inhibited by G6P

10

How is PFK-1 activated and deactivated?

by AMP, F2,6BP (formed by PFK-2/FBPase-2)
Inhibited by: ATP, Citrate
Dephosphorylated (active): kinase
Phosphorylated (inactive); phosphatase

11

How does high insulin/ low glucagon affect PFK-1

High insulin activates protein phosphatases which dephosphorylate PFK-2/FBPase-2, (turning it on) which in turn, producing F2,6BP which activates PFK-1

12

How does High glucagon/low insulin affect PFK-1

It induces high {cAMP}, activate protein kinase A which phosphorylates PFK2/FBPase-2 (triggers phosphorylation activity) which reduces PFK-1 activity

13

What activates Pyruvate Kinase?

F1,6BP and Insulin.
Insulin stimulates protein phosphatase, dephosphorylation of PK, active

14

What inhibits Pyruvate Kinase?

ATP, glucagon, Alanine
Glucagon: cAMP activates PKA which phosphorylates and inhibits PK

15

4 fates of G6P

Glucose, Glycogen, Pyruvate, Ribose/NADPH

16

Defects in glycolysis often result in what ?

Hemolytic anemia

17

Why result in hemolytic anemia?

RBC's do not have mitochondria so if glycolysis is defective, become RBC deficient, ion gradients disrupted -> hemolytic anemia

18

Causes of Diabetes

There are many but some possible ones are mutations in GK and mitochondrial tRNA

19

Type 1 Diabetes

insulin deficiency due to loss of Pancreatic B cells

20

Type 2 diabetes

Insulin resistance -> loss of B cell function

21

Tarui Disease

PFK-1 deficient

22

Where does gluconeogenesis occur?

Liver, kidney, small intestine

23

What are the 3 bypasing steps of gluconeogenesis?

PEP carboxykinase, pyruvate carboxylase,F1,6Bphosphatase, G6phosphatase

24

What are the positive regulators for glycolysis?

Glucose, insulin, AMP, Fru 2,6-BP, Fru 1,6-BP

25

What are the positive regulators for gluconeogenesis

Glucagon, citrate, cortisol, thyroxine, acetyl CoA

26

What are negative regulators for glycolysis?

Glucagon, ATP, citrate, Glc 6-P, Fru 6-P, alanine

27

What are negative regulators for gluconeogenesis

AMP, insulin, Fru2,6-BP, ADP

28

Pyruvate Carboxylase

Appears in Mitochondria, turns pyruvate into oxaloacetate with coenzyme Biotin, CO2 and ATP, activated by acetyl coA and cortisol.

29

Fru1,6BPhosphatase

Rate limiting step,

30

Cori Cyle

Lactate travels from muscle cell to liver and converts to pyruvate via lactate dehydrogenase then goes through gluconeogenesis.

31

Von Gierke Disease

Deficiency in G6 phosphatase

32

Galactose uptake is via which transporter

SGLT1

33

Fanconi-Bickel syndrome

mutation in GLUT2 transporter, unable to take up glucose , fructose and galactose

34

Conversion of Glucose into Fructose

Glucose reduced to Sorbitol by aldose reductase, sorbitol oxidzed to fructose by sorbitol dehydrogenase

35

Sorbitol Accumulation

lack of sorbitol dehydrogenase results in build up of sorbitol -> cataracts

36

Galactosemia

Deficiency in glucose 1P uridyltransferase (GALT)
or Deficiency in Galactokinase

37

What is the rate limiting step in PPP?

G6P dehydrogenase

38

Which cells have very high demand for PPP activity?

Phagocytic cells

39

Structure of glycogen

linked at a1,4 glycosidic bonds and branch at a1,6 glycosidic bonds, degraded on non reducing end, reducing end has glycogenin.

40

Difference between liver and muscle glycogen.

liver: regulates blood sugar levels
muscle: used for fuel.

41

Rate limiting step in glycogenesis

Glycogen synthase

42

Rate limiting step in glycogenolysis

Glycogen phosphorylase

43

Glycogenolysis is favored when?

Fasting and exercise (Ca2+ levels are high and AMP levels high)

44

Blood sugar values

Normal: Fasted: 70-100, fed 140>0
Pre-diabetic: 100-125, >140
Diabetic: 125

45

GSD

Defective enzyme: Glycogen Synthase
Affected pathway: glycogenesis: chain elongation

46

Pompe disease

Acid maltase,
lysosomal glycogenolysis, release of Glc

47

Andersen disease

Glucosyl transferase (branching enzyme), , Glycogenesis

48

McArdle disease

muscle glycogen phosphorylase, Glycogenolysis

49

Hers Disease

Liver glycogen phosphorylase,
Glycogenolysis