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ZZZBiochemistry > Carbohydrate Metabolism > Flashcards

Carbohydrate Metabolism Flashcards

1
Q

What is the overall process of glycolysis?

A

1 mol Glucose -> 2 mols Pyruvate

Pyruvate -> Lactate (when there is low amounts of oxygen like when sprinting)

Pyruvate -> CO2 + H2O (when there is lots of oxygen like during a slow run)

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2
Q

How many ATPs does Glycolysis produce overall

A

2 ATP

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3
Q

_____ is the only fuel that rbcs can use

_____ is the only fule that the brain uses under non-starvation conditions

A

Glucose

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4
Q

Where are each of the following GLUTs found? Describe the affinity/Km for each

GLUT1
GLUT2
GLUT3
GLUT4

A

GLUT1- rbcs and brain (High affinity, Km is low)
GLUT2- liver (Low affinity, Km is high)
GLUT3- neurons (High affinity, Km is low)
GLUT4- skeletal muscle, heart, adipose tissue (medium affinity, Km is medium)

remember that Km is inversely proportional to the affinity

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5
Q

Which GLUT is regulated by insulin?

A

GLUT4- skeletal muscle, adipose tissue, and heart

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6
Q

Where does glycolysis occur?

A

Within the cytoplasm

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7
Q

What is the overall yield of glycolysis?

A

2 ATP
2 NADH
2 Pyruvate

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8
Q

What are the 3 regulatory steps of glycolysis and what is the rate limiting step?

A

Hexokinase(in all cells)/Glucokinase (in liver and pancreatic cells) trap glucose within the cell by using ATP

Phosphofructokinase is used as the rate limiting enzyme. ATP is also used here too

Pyruvate Kinase is the last enzyme for the regulatory step in glycolysis

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9
Q

What are the 3-4 factors that govern whether glycolysis occurs or not?

A

ATP/AMP
Glucose
Insulin/Glucagon

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10
Q

Glucokinase and Hexokinase both trap glucose within cells. For each, describe where they are found, the Km, and the Vmax

A

Hexokinase:
Location: All cells
Km: Low (High affinity)
Vmax- Low

Glucokinase:
Location- Liver and pancreas
Km- High (Low affinity)
Vmax- High

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11
Q

What do glucokinase/hexokinase change glucose to?

A

G6P

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12
Q

Phosphofructokinase-1 is the rate limiting step in glycolysis. Describe when it is in its active form and when it is in its inactive form in terms of insulin and glucagon levels.

A

Fed State: High Insulin/Low Glucagon -> Want more glycolysis -> Dephosphorylation of PFK-2 -> Increases F-2,6 BP -> Increases PFK-1 activity

Fasting State: Low Insulin/High Glucagon -> Decreases Glycolysis -> Phosphorylates PFK-2 -> Decreases F-2,6-BP -> Decreases PFK-1 activity

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13
Q

What is deficient in Tarui’s disease?

A

Phosphofructokinase is deficient

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14
Q

Does a high G6P activate or inhibit Hexokinase?

A

Inhibits because that is the product

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15
Q

G6P that is produced in glycolysis is also a precursor for what pathway?

A

The pentose phosphate pathway

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16
Q

If glycolytic enzymes are defective, what clinical diagnosis occurs? What kind of cells does this mostly impact?

A

Hemolytic anemia, which mostly impacts rbcs

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17
Q

rbcs lack mitochondria, therefore _____ is the only mechanism that produces ATP

A

Glycolysis

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18
Q

What is mutated that causes Fanconi-Bickel Syndrome

A

Mutation in the GLUT2 transporter, which causes an inability to take up glucose, fructose, and galactose

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19
Q

How many grams of glucose does your body need on the daily to survive? How much from the brain, how much from the bodily fluids?

A

160 grams

120 grams from brain
20 form bodily fluids

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20
Q

How many grams of glucose do we have in reserve?

A

190 grams glucose in reserve, which means we can only store enough glucose to survive for one day

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21
Q

Describe the overall process of gluconeogenesis. In what 3 tissues does this occur?

A

Converts pyruvate into glucose (almost an exact opposite to glycolysis, but not exactly)

Occurs in the liver, kidneys, and small intestines

*Note that energy is being used, not made during gluconeogenesis. This is because the point of gluconeogenesis is to make glucose when we are fasting.

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22
Q

What are the 4 main enzymes of gluconeogenesis? Which one is the rate limiting step?

A

Glucose 6 Phosphatase
Fructose 1,6 bisphsphate (rate limiting step)
PEP carboxykinase
Pyruvate carboxylase

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23
Q

How does Glucagon and ADP/AMP affect gluconeogenesis?

A

Glucagon increases it

ADP/AMP decreases it

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24
Q

How does Glucose, insulin, and AMP affect glycolysis?

A

They all increase it

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25
Q

How does Glucagon and ATP affect Glycolysis?

A

They both decrease it

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26
Q

Compare the net yield/use of ATP for glycolysis and gluconeogensis?

A

Glycolysis: Net yield it 2 ATP
Gluconeogenesis: Net use is 6 ATP, 0 Net yield

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27
Q

Describe the Cori Cycle.

A

This links the lactate produced from anaerobic glycolysis in RBC and exercising muscle to gluconeogenesis in the liver

28
Q

What are the 3 precursors of gluconeogenesis?

A

Carbohydrates, lipids, and proteins

29
Q

If a patient had a disorder of the molecule Fructose 1,6 bisphosphatase, what pathway would be affected? What is this similar to?

A

F 1,6 Bisphosphatase deficiency is a disorder of gluconeogenesis

This is similar to Tarui’s disease in glycolysis- deficiency in PFK-1

30
Q

What is Von Gierke’s disease?

A

Deficiency in Glucose-6-phosphatase

31
Q

What are the monosaccharides that make up sucrose?

A

fructose and glucose

32
Q

What are the monosaccharides that make up lactose?

A

galactose and glucose

33
Q

What is the issue with high amounts of fructose intake within your diet?

A

This bypasses the rate limiting step of glycolysis due to the absence of PFK-1 and therefore causes an increase in triacylglycerides

34
Q

What is the rate limiting step of galactose metabolism?

A

Glalactose-1-phosphate uridyltransferase (GALT)

35
Q

What is caused by galactosemia? What does this cause?

A

Deficiency in glucose- 1 phosphate uridyltransferase (GALT)

Causes liver failure

36
Q

What does a deficiency in Galactokinase cause?

A

an accumulation of galactitol in the eye, which leads to cataracts

37
Q

What is the purpose of the pentose phosphate pathway?

A

Produce NADPH that is needed for reductive biosynthesis

It also is used to produce ribose

38
Q

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

A

G6P Dehydrogenase

39
Q

What is the purpose of NADPH?

A

It regenerates glutathione, which is an important antioxidant

40
Q

What are the 2 phases of the pentose phosphate pathway? Which one has a high demand for Ribose and which has a high demand for NADPH

A

Oxidative Pathway- High demand for Ribose 5 Phosphate

Non-oxidative pathway- High demand for NADPH

41
Q

Describe the structure of glycogen?

A

Glycogenin is the beginning part

chains of glucose are connected

42
Q

What 2 tissues store glycogen?

A

Liver and Muscle

43
Q

What is the function of liver glycogen?

A

Regulates blood glucose levels

44
Q

What is the function of muscle glycogen?

A

Provides reservoir of fuel for physical activity

45
Q

What attaches glycogen in a linear fashion?

A

Glycogen synthase

46
Q

What attaches glycogen in an branched pattern?

A

Glucosyl (4,6) transferase

47
Q

When glycogen is debranched what is the yield of glucose1phosphate and glucose

A

10 G1P

1 Glucose

48
Q

What are the 2 reasons why we regulate glycogen metabolism?

A

Maintain blood sugar

Provide energy to muscle

49
Q

What are the 2 key enzymes of glycogen metabolism?

A

Glycogen Synthase- the rate limiting step of synthesis

Glycogen Phosphorylase- the rate limiting step of degradation

50
Q

What is the active form of glycogen synthase and glycogen phosphorylase?

A

Glycogen Synthase:
Dephosphorylated is active form
Phosphorylated is the inactive form

Glycogen Phosphorylase:
Dephosphorylated is the inactive form
Phosphprylated is the active form

51
Q

What are the 3 factors that favor the fed state of glycogenesis?

A

High blood glucose
High insulin
High ATP

52
Q

What are the 2 factors that favor glycogenolysis in the fasting state?

A

Low blood glucose

High glucagon

53
Q

What 2 factors favor glycogenolysis during exercise?

A

High calcium

High AMP

54
Q

Does Glucagon act on muscles?

A

NO

55
Q

What are the 4 key proteins involved in regulation by insulin?

A

GLUT4
Protein Kinase B
Protein Phosphatase 1
Glycogen Synthase Kinase 3

56
Q

What are the blood glucose criteria for the following:
Normal
Prediabetic
Diabetes Mellitus

A

Normal: 70-100 (fasting), ≤140 (fed)
Prediabetic: 100-125 (fasting), >140 (fed)
Diabetes Mellitus: ≥125 (fasting), ≥199 (fed)

57
Q

What is the overall result of insulin being used?

A

Glycogen Synthesis via activation of glycogen synthase and inactivation of glycogen phosphorylase

58
Q

What is the overall result of glucagon being used?

A

Glycogen breakdown via inactivation of glycogen synthase and activation of glycogen phosphorylase

59
Q

What molecule is deficient in GSD 0?

A

Glycogen Synthase

60
Q

What molecule is deficient in GSD 1 Von Gierke Disease?

A

Glucose 6 Phosphatase

61
Q

What molecule is deficient in GSD 2 Pompe Disease? What does this result in?

A

Acid Glucosidase, which results in the impairment of lysosomal glycogenolysis. This causes the accumulation of glycogen in lysosomes

62
Q

What molecule is deficient in GSD 3? Cori Disease

A

Deficiency in alpha-1,6- glucosidase (the debranching enzyme)

This causes patients to have glycogen with a large number of short branches

63
Q

What molecule is deficient in GSD 4? Andersens Disease

A

Deficiency in glucosyl (4:6) transferase (the branching enzyme)

This causes patients to have longer chain glycogens with fewer branches

64
Q

What molecule is deficient in GSD 5? McArdle disease

A

Deficiency in MUSCLE glycogen phosphorylase, which is the rate limiting step of glycogen breakdown

65
Q

What molecule is deficient in GSD 6? Hers Disease

A

Deficiency in LIVER glycogen phosphorylase, which is the rate limiting step of glycogen breakdown

66
Q

What are the 5 key enzymes regulated by Glucagon?

A 
GPCR
Adenylyl Cyclase
Protein Kinase A
Protein Phosphatase 1
Phosphorylase Kinase

ZZZBiochemistry (12 decks)

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