Glycolysis

Question 1

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

Answer 1

via specific transporters (GLUT) by facilitated diffusion!

Question 2

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

Answer 2

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

Question 3

what is hexokinases Km for glucose?

Answer 3

low Km = high affinity!

Question 4

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

Answer 4

glycogen
pyruvate
HMP shunt

Question 5

where are glycolytic enzymes present>

Answer 5

in the cytosol

Question 6

what are the 3 general stages of glycolysis

Answer 6

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

Question 7

How many reactions are involved in stage 1?

Answer 7

2 phosphorylation reactions

requires 2 ATP

Question 8

what is the second irreversible reaction of glycolysis?

Answer 8

PFK1 - phosphofructokinase-1

also the most important regulated step (allosteric regulated enzyme)

Question 9

Where are aldolase A and B found?

Answer 9

muscle and liver

Question 10

how many molecules of pyruvate are formed in glycolysis?

Answer 10

2 pyruvate

Question 11

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

Answer 11

NADH

Question 12

what does phosphoglycerate kinase result in the formation of?

Answer 12

the first ATP (substrate level phosphorylation)

Question 13

why are 1,3 BPG and phosphpenolpyruvate special?

Answer 13

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

Question 14

what does pyruvate kinase result in?

Answer 14

formation of the 2nd ATP

Question 15

what are the fates of pyruvate?

Answer 15

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

Question 16

what are the 3 irreversible reactions in glycolysis?

Answer 16

glucokinase/hexokinase
phosphofructokinase 1
pyruvate kinase

Question 17

what were the two substrate level phosphorylation reactions in glycolysis?

Answer 17

phosphoglycerate kinase

pyruvate kinase

Question 18

what is the overall reaction of aerobic glycolysis?

Answer 18

aerobic

Question 19

how many ATP are formed in aerobic glycolysis?

Answer 19

8 ATP

Question 20

how many ATP are formed in anaerobic glycolysis?

Answer 20

2 ATP

Question 21

what are inhibitors of glycolysis?

Answer 21

arsenate and fluoride

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Question 24

why is glycolysis significant in adipose tissue?

Answer 24

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

Question 25

why is glycolysis significant for RBC?

Answer 25

anaerobic glycolysis is the major source of energy - forms 2,3 BPG glycolysis also important in retina, lens and tumor cells

Question 26

when does 2,3 BPG increase?

Answer 26

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

Question 27

what is hemolytic anemia?

Answer 27

RBC PK deficiency | second most common form of hemolytic anemia

Question 28

what is the most common form of hemolytic anemia?

Answer 28

G6PD definicieny

Question 29

what is lactic acid an example of?

Answer 29

metabolic acidosis - commonly seen

Question 30

when is lactic acid observed?

Answer 30

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

Question 31

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

Answer 31

glycolysis - 'Warburg effect'

Question 32

what do tumor cells utilize in PET scans?

Answer 32

fluorodeoxyglucose (FDG) pharmacological inhibitor of glycolysis are explored for use as therapeutic agents in variety of cancers

Question 33

what is galactose deficiency

Answer 33

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

Question 34

what is Gal-1-P uridyl transferase deficiency?

Answer 34

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

Question 35

what is fructoinase deficiency?

Answer 35

fructosuria - benign

Question 36

what is aldolase B deficiency?

Answer 36

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

Question 37

pyruvate kinase deficiency?

Answer 37

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

Question 38

what inhibits HK?

Answer 38

g-6-p = product inhibition

Question 39

what stimulates GK?

Answer 39

insulin in the liver

Question 40

what activates PFK-1?

Answer 40

AMP | F-2,6-bisP

Question 41

what inhibits PFK-1?

Answer 41

ATP | Citrate

Question 42

what activates PFK-2?

Answer 42

insulin

Question 43

what inhibits PFK-2?

Answer 43

glucogon

Question 44

what activates PK?

Answer 44

F-1,6-bisP | insulin

Question 45

what inhibits PK?

Answer 45

ATP Acetyl Co A Alanine Glucagon

Question 46

what does GLUT 1 + 3 transporters do?

Answer 46

basal uptake - neurons and brain

Question 47

What does GLUT 2 transporters do?

Answer 47

liver

Question 48

what does Glut 4 transporters do?

Answer 48

adipose and muscle

Question 49

why is glucokinase needed in the liver?

Answer 49

to reduce high BGL after a large meal

Question 50

what does glucokinase do in the pancreas?

Answer 50

recognition of high BGL and --> insulin release

Question 51

genetic deficieicny of GK can lead to what?

Answer 51

DM in the young type 2 (MODY 2)

Question 52

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

Answer 52

nucleus

Question 53

what is important to remember about exercising muscle and AMP levels

Answer 53

high levels of AMP overcome inhibition by ATP