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Medical Biochemistry > Glycolysis > Flashcards

Flashcards in Glycolysis Deck (53):
1

Fate of absorbed glucose - how does glucose in the bloodstream enter cells?

via specific transporters (GLUT) by facilitated diffusion!

2

Where is glucokinase found? what it its Km for glucose?

in liver and beta cells of pancrease
km is high (needs way more glucose to get saturated) = which is why its more active when BGL are elevated

3

what is hexokinases Km for glucose?

low Km = high affinity!

4

after glucose is phosphorylated and becomes glucose-6-phophate, what are the intracellular fates of glucose-6-phosphate in the liver?

glycogen
pyruvate
HMP shunt

5

where are glycolytic enzymes present>

in the cytosol

6

what are the 3 general stages of glycolysis

Stage 1: energy investment stage
stage 2: cleavage of 6C sugar to 3C intermediates
stage 3: energy generation phase

7

How many reactions are involved in stage 1?

2 phosphorylation reactions
requires 2 ATP

8

what is the second irreversible reaction of glycolysis?

PFK1 - phosphofructokinase-1
also the most important regulated step (allosteric regulated enzyme)

9

Where are aldolase A and B found?

muscle and liver

10

how many molecules of pyruvate are formed in glycolysis?

2 pyruvate

11

what does glyceraldehyde-3-phosphate dehydrogenase result in the formation of?

NADH

12

what does phosphoglycerate kinase result in the formation of?

the first ATP (substrate level phosphorylation)

13

why are 1,3 BPG and phosphpenolpyruvate special?

they are both high energy intermediates and compounds, respectively. they can form ATP within the involvement of the ETC in mitochondira

14

what does pyruvate kinase result in?

formation of the 2nd ATP

15

what are the fates of pyruvate?

aerobic --acetyl coA(pyruvate dehydrogenase)--enters TCA cycle
anaerobic --lactate(lactate dehydrogenase)--goes to liver via Cori cycle

also in liver--gluconeogenesis(pyruvate carboxylase) --oxaloacetate

16

what are the 3 irreversible reactions in glycolysis?

glucokinase/hexokinase
phosphofructokinase 1
pyruvate kinase

17

what were the two substrate level phosphorylation reactions in glycolysis?

phosphoglycerate kinase
pyruvate kinase

18

what is the overall reaction of aerobic glycolysis?

aerobic

19

how many ATP are formed in aerobic glycolysis?

8 ATP

20

how many ATP are formed in anaerobic glycolysis?

2 ATP

21

what are inhibitors of glycolysis?

arsenate and fluoride

22

why does fluoride have to be added to blood collection tube in clinical labs?

if fluoride wasn't added - there would be a reduction in the glucose due to its utilization by RBC and WBC, resulting in an erroneously low value for blood glucose

23

what is the significance of glycolysis in tissues which complete oxidation takes place

brain, skeletal muscles - glucose is converted to pyruvate, that is later converted to acetyl coA that enters the TCA cycle for complete oxidation of glucose

24

why is glycolysis significant in adipose tissue?

glyceraldehyde-3-phosphate (provides glycerol component) that is used for TAG formation

25

why is glycolysis significant for RBC?

anaerobic glycolysis is the major source of energy - forms 2,3 BPG

glycolysis also important in retina, lens and
tumor cells

26

when does 2,3 BPG increase?

when a person moves to a high altitude - facilitates unloading - right shift

27

what is hemolytic anemia?

RBC PK deficiency
second most common form of hemolytic anemia

28

what is the most common form of hemolytic anemia?

G6PD definicieny

29

what is lactic acid an example of?

metabolic acidosis - commonly seen

30

when is lactic acid observed?

increase conversion of pyruvate to lactate (increase NADH/NAD+ ratio)
strenuous muscle activity
inherited deficiency of pyruvate dehydrogenase (leigh disease)
thiamine deficiency = lowered activity of pyruvate dehydrogenase
defect in gluconeogensis (decrease conversion of lactate to glucose)
decreased blood supply results in anaerobic metabolism in the peripheral tissues

31

what do cancer cells used as the main source of ATP?

glycolysis - 'Warburg effect'

32

what do tumor cells utilize in PET scans?

fluorodeoxyglucose (FDG)

pharmacological inhibitor of glycolysis are explored for use as therapeutic agents in variety of cancers

33

what is galactose deficiency

galactosemia/galactosuria, cataracts in childhood (excess galactose is converted to galatitol via aldose reductase)
Treatment: no galactose in diet

34

what is Gal-1-P uridyl transferase deficiency?

same as galactokinase deficiency but more severe with vomiting/diarrhea after milk ingestion, liver disease, lethargy mental retardation,
Tx=no galactose in diet

35

what is fructoinase deficiency?

fructosuria - benign

36

what is aldolase B deficiency?

fructosuria - liver and prominal renal tubule disorder
tx = no fructose in diet

37

pyruvate kinase deficiency?

chronic hemolysis, you increase 2,3 BPG and other intermediates in the RBX - autosomal recessive

38

what inhibits HK?

g-6-p = product inhibition

39

what stimulates GK?

insulin in the liver

40

what activates PFK-1?

AMP
F-2,6-bisP

41

what inhibits PFK-1?

ATP
Citrate

42

what activates PFK-2?

insulin

43

what inhibits PFK-2?

glucogon

44

what activates PK?

F-1,6-bisP
insulin

45

what inhibits PK?

ATP
Acetyl Co A
Alanine
Glucagon

46

what does GLUT 1 + 3 transporters do?

basal uptake - neurons and brain

47

What does GLUT 2 transporters do?

liver

48

what does Glut 4 transporters do?

adipose and muscle

49

why is glucokinase needed in the liver?

to reduce high BGL after a large meal

50

what does glucokinase do in the pancreas?

recognition of high BGL and --> insulin release

51

genetic deficieicny of GK can lead to what?

DM in the young type 2 (MODY 2)

52

where is GK stored at high fructose 6-P levels?

nucleus

53

what is important to remember about exercising muscle and AMP levels

high levels of AMP overcome inhibition by ATP