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Biochemistry > Biochem Exam 2: Glycolysis And Gluconeogenesis > Flashcards

Biochem Exam 2: Glycolysis And Gluconeogenesis Flashcards

1
Q

What two organs use glucose only

A

RBC and brain

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2
Q

Sources of glucose in diet?

A

Starch
Glycogen
Disaccharides (sucrose and lactose)

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3
Q

GLUT1

A

Ubiquitous but high in RBC and brain

High affinity for glucose

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4
Q

GLUT 2

A

Transporter in liver

Low affinity

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5
Q

GLUT 3 neurons

A

High affinity

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6
Q

GLUT 4 skeletal muscles, heart, adipose tissue

A

Insulin dependent

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7
Q

Low KM means what for glucose?

A

High affinity

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8
Q

High KM means what for glucose?

A

Low affinity

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9
Q

In stage one, the first enzyme to break glucose down to glucose 6-phosphate is what?

A

Hexokinase

In liver it is glucokinase

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10
Q

Glucose 6-phosphate is broken down to fructose 6-phosphate by what enzyme?

A

Phosphoglucose isomerase

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11
Q

Fructose 6-phosphate is broken down to Fructose 1,6 bisphosphate by what enzyme?

A

Phosphofructokinase

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12
Q

What is the strategy of phase one in glycolysis?

A

To trap glucose and for a compound that can be readily cleaved into 2 phosphorylated 3 carbon units

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13
Q

What is the committed step for stage one of glycolysis?

A

Glucose 6-phosphate to fructose 6-phosphate (phosphoglucose isomerase)

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14
Q

Enzyme that breaks down F1,6 BP to glyceraldehyde 3 phosphate is what?

A

Aldolase

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15
Q

What enzyme isomerizes DHAP?

A

Triode phosphate isomerase

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16
Q

G3P is oxidized to 1,3 BPG by what enzyme and what carrier molecule?

A

Enzyme glyceraldehyde 3-phosphate dehydrogenase

Carrier molecule NAD+ reduced to NADH

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17
Q

1,3 BPG is converted to 3-PG by what enzyme

And what does it make?

A

Phospholycerate kinase

Makes ATP

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18
Q

3-phosphoglycerate is converted to 2-phosphoglycerate via what enzyme?

A

Phosphoglycerate Mutase

Changes the phosphate to the 2 orientation instead of the 3

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19
Q

2-PG is converted to PEP (phosphoenolpyruvate) by what enzyme?

A

Enolase (produces water- dehydration)

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20
Q

PEP is converted to pyruvate by what enzyme?

A

Pyruvate kinase transfer

This step is irreversible

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21
Q

Pyruvate can be converted into 3 things considering the oxygen level what are these three things? And how does it occur?

A

Further oxidation with oxygen present after getting ride of CO2 and becoming Acetyl CoA

It can become lactate by taking back the hydrogen on NADH

It can create ethanol by getting rid of CO2 AND taking back the hydrogen on NADH

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22
Q

By pyruvate becoming lactate, what is regenerated?

A

NAD+

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23
Q

Glucose + fructose creates what

A

Sucrose

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24
Q

Glucose + galactose create what?

A

Lactose

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25
Q

The important rate limiting step in glycolysis is what enzyme?

A

Phophofructose

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26
Q

Why is fructose bad for us?

A

It skips the rate limiting step when found in the liver (enters in the DHAP or GAP entry of stage 1)

Fructose is quickly turned to fat in times of high energy

Can give us a fatty liver, type diabetes, obesity, and insulin insensitivity

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27
Q

Where does galactose enter?

A

G-6p

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28
Q

Where does fructose from adipose tissue enter?

A

F-6P

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29
Q

Major regulators of glycolysis include these 3 enzymes

A

Hexokinase
Phosphofructokinase
Pyruvate kinase

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30
Q

What negative feedbacks on hexokinase?

A

G-6P

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31
Q

What is g-6p converted to when the muscle is at rest?

A

Glycogen

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32
Q

What negatively feedbacks on PFK?

A

Pyruvate kinase

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33
Q

When the muscle is active and glycolysis is stimulated, what are two positive feedback loops?

A
  1. Decreased ATP causes PFK to reactive teens

2. Increase in F 1,6-B causes pyruvate kinase to activate

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34
Q

In the liver what two enzymes are regulated and by what?

A

Phosphofructokinase is activated by F 2,6 BP
Inhibited by citrate

And glucokinase (no hexokinase)
Not regulated! Glucose is trapped

Pyruvate kinase is regulated by allosteric effectors and covalent modification (phosphorylated -less active and dephosphoralated -more active)

35
Q

Low glucokinase means what for the liver and glucose?

A

Glucokinase is inhibited (glucose doesnt want to be trapped)

36
Q

Gluconegogenesis definition

A

Synthesis of glucose from non-carbohydrate precursors

37
Q

What are three major precursors in creating glucose?

A

Lactate, amino acids (alanine), and glycerol

38
Q

Is gluconeogenesis the reversal of glycolysis?

A

No

39
Q

Where does gluconeogenesis occur in the body?

A

Liver and kidney

40
Q

What does gluconeogenesis do with pyruvate?

A

Coverts it to glucose

41
Q

What four enzymes help to reverse the irreversible step in glycolysis?

A
  1. Pyruvate carboxylase
  2. Phosphoenolpyruvate (PEP) carboxykinase
  3. Fructose 1,6-BPase
  4. Glucose 6-phosphatase
42
Q

What enzyme that helps to bypass the irreversible steps of glycolysis is found in the mitochondria?

A

PC (pyruvate carboxylase)

43
Q

How is oxaloacetate transferred to the cytoplasm?

A

Malate shuttle

44
Q

Where is glucose 6-phosphatase located

A

In the lumen of the endoplasmic reticulum

And it removes the phosphate so glucose can leave the liver

45
Q

How are gluconeogenesis and glycolysis regulated together?

A

As reciprocals

46
Q

Positive regulators for gluconeogenesis are….

A 
Glucagon
Citrate
Cortisol
Thyroxine
Acetyl CoA
47
Q

Can lactate become pyruvate?

A

Yes, in the liver

48
Q

What is the cori cycle?

A

Where we take lactate to pyruvate to glucose and glucose to pyruvate and to lactate

49
Q

Characteristics of glycogen

A

12 layers of glucose
Branches
Linked together via alpha-1,4 glycosidic bonds
A branch forms ever 12 residues via alpha-1,6 glycosidic bonds
Non-reducing end contain a terminal glucose with a free hydroxal at C4
Reducing wend has glucose Capp protein called glycogenin

50
Q

Where is glycogen stored?

A

Liver, muscles, and other tissues

51
Q

How is glycogen present in cells?

A

As granules

52
Q

How is glycogen metabolism regulated

A

Allosteric control
Covalent modification through reversible phosphorylation of key enzymes
Hormonal control

53
Q

How is glycogen storage build? Glucogenesis?

A
  1. Take glucose to glucose 6-P. Then enzyme mutase changes it to G1-P. G1-P is phosphorylated to UDP-G.
  2. UDP-G is added to a primer using glycogen synthase. ( Rate limiting step) and forms alpha 1,4 glycosidic bond between molecules of glucose.
  3. When glycogen reaches the 11 residue, a fragment of changing is broken off at an alpha 1,4 link and reattached via a alpha 1,6 linkage by glucosyl tranferase
54
Q

The more branches the faster glycogen can be degraded, true or false?

A

True

55
Q

Glycogen synthase is active in what form?

A

Non-phosphorylated “a” form

56
Q

Glycogen synthase is inactive in what form?

A

Phosphorylated “b” form

57
Q

How is glycogen synthase phosphorylated?

A

By glycogen synthase kinase (GSK)

Protein kinase A (PKA)

Hormonal control

58
Q

How is glycogen synthase de phosphorylated?

A

Protein phosphatase I (PPI)

59
Q

How is glycogen synthase allostericly regulated?

A

Gluc-6-phosphate

60
Q

Glycogenolysis, how many steps?

A

2

61
Q

What is step one in glycogenolysis?

A

Chain shortening (release of Glu-1-P)

62
Q

What is the rate limiting step of glycogenolysis?

A

Glycogen phosphorylated (GP)

63
Q

What is the cofactors of glycogen phosphorylated? (GP)

A

B6 (pyridoxal phosphate)

64
Q

How far will glycogenolysis go on for?

A

Within 4 residues of a alpha 1,6 linkage

65
Q

What is step 2 of glycogenolysis?

A

Branch transfer and release of glucose

66
Q

What enzyme is used to debranch glycogen?

A

Debranching enzyme (transferase 4:4)

67
Q

GP exist in 2 forms an active and inactive. What is its active form?

A

Relaxed state in liver “a”

Phospho form

68
Q

GP has an inactive state, what is it?

A

“B” form (tense state) in muslce

Dephospho

69
Q

Phosphorylation of single serine residue converts b to a how is this conversion initiated and what enzyme carries this action out?

A 
Hormones
Phosphorylase kinase (PK)
70
Q

Does glucagon act on mucscles?

A

NO

71
Q

What acts on muscles to release glycogenolysis?

A

Epinephrine

72
Q

What cells of pancreas release glucagon?

A

Alpha cells

73
Q

What cells of pancreas release insulin?

A

Beta

74
Q

Free glucose inhibits glycogen phophorylaase in liver but not muscles true or false

A

True

75
Q

In liver cells what is the glucose sensor?

A

Glycogen phosphorylase

76
Q

Glycogen storage disease

Disorder to affect synthesis:

A

Autosomal recessive

Patients need to be dependent on glucose rather than glycogen

77
Q

Glycogen storage disease disorders that effect breakdown:

A

Lead to hepatomegaly

Lead to hypoglycemia

78
Q

I von Gierke

A

Defective: glucose 6-phosphatase or transport system

Causes disorder in breakdown

Liver and kidneys

79
Q

II pompe

A

Defective alpha 1,4 glucosidase (lysosomal)

All organs

Increase in amount of glycogen

Death by cardiorespiratory failure by 2

80
Q

III corti

A

Alpha 1,6 glucosidase (debranching)

Muscle and liver

Increased amount of glycogen

Like type 1

81
Q

IV Andersen

A

Branching enzyme

Liver and spleen

Normal amount glycogen (very long)

Progressive cirrhosis of liver

Liver failure by age 2

82
Q

V McArdle

A

Phosphorylase

Muscle

Moderately increased amount of glycogen

Limited ability to perform strenuous exercise

83
Q

VI hers

A

Phosphorylase

Liver

Increased amount of glycogen

Like type I

Biochemistry (9 decks)

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