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Biochemistry I/II > Exam II-L7 (Glycolysis/Gluconeogenesis) > Flashcards

Exam II-L7 (Glycolysis/Gluconeogenesis) Flashcards

1
Q

What cell types does glycolysis primarily occur in? What organ does gluconeogenesis primarily occur in?

A

Glycolysis occurs in ALL cells

Gluconeogensis primarily occurs in LIVER cells

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2
Q

____: the process by which glucose is broken down to release usable energy (energy is released)

____: the process by which glucose is SYNTHESIZED, requires energy input (energy is consumed)

A

Glycolysis: the process by which glucose is broken down to release usable energy (energy is released)

Gluconeogenesis: the process by which glucose is SYNTHESIZED, requires energy input (energy is consumed)

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3
Q

True or False: A minimum level of glucose in the blood is required for survival

A

True

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4
Q

What is the central pathway for breakdown of sugar?

A

Glycolysis

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5
Q

Where does glycolysis occur within a cell?

A

Cytosol

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6
Q

One molecule of glucose is split into two molecules of ____

A

pyruvate

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7
Q

How many NADH molecules are produced during glycolysis?

A

2 NADH

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8
Q

How many ATP are invested in the early phase of glycolysis?

How many ATP are gained in the energy generation phase?

A

2 ATP are invested in early phase
4 ATP are generated in later phase

Glycolysis = net gain of 2 ATP

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9
Q

What are the two main purposes of glycolysis?

A

1) Energy production (NADH and ATP)
2) Cellular growth (biosynthesis)

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10
Q

Intermediates of glycolysis are used as building blocks of biosynthesis, which is important for processes such as ______

A

cell division and growth

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11
Q

True or False: Deficiencies in one or more glycolysis enzymes reduces energy output from glycolysis

A

True

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12
Q

When glycolytic activity is reduced, most cells can utilize other fuels (fatty acids, amino acids) to make ATP, but this requires ____

A

mitochondria

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13
Q

What cell types lack mitochondria and, therefore, are highly sensitive to decreases in glycolysis activity?

A

RBC’s!

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14
Q

Glycolysis is the only source of energy for what cell type?

A

RBC’s

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15
Q

When there is RBC’s loss, normal cellular functions are not maintained due to lack of ___

A

ATP

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16
Q

True or False: Disorders of glycolysis can reduce RBC lifespan from 120 days to a few days to weeks

A

True

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17
Q

Disorders of glycolysis can result in anemia. What are the clinical features of anemia?

A

1) Decreased RBC’s
2) SOB
3) Fatigue

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18
Q

Under anaerobic (!!!) conditions, glucose will be converted to ____, which will be converted to ___

A

pyruvate; lactate

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19
Q

Under aerobic (!!!) conditions, pyruvate is converted to ____ in the _____

A

acetyl-CoA in the mitochondria

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20
Q

Conversion of ___ to ___ reoxidizes NADH to ____, allowing the next round of glycolysis to occur

A

pyruvate to lactate; NAD+

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21
Q

What enzyme converts pyruvate to lactate?

A

Lactate dehydrogenase (LDH)

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22
Q

What molecule is required during lactate dehydrogenase reaction?

A

NADH

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23
Q

What cell types lack mitochondria?

A

RBC’s

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24
Q

____ muscle favors anaerobic metabolism, as well as the ____of the eye

A

skeletal muscle; lens/cornea

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25
Q

What two mechanisms are used by the liver to maintain blood glucose?

A

1) Glycogen
2) Gluconeogenesis

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26
Q

Glycogen ___ glucose
Gluconeogenesis ____ glucose

A

Glycogen stores glucose
Gluconeogenesis creates glucose

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27
Q

In gluconeogenesis, an equivalent of _ ATP are needed for each glucose made

A

6 ATP

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28
Q

True or False: The liver has the ability to manufacture glucose from other molecules (e.g pyruvate)

A

True

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29
Q

What process helps maintain and stabilize proper blood glucose levels in the absence of nutrients from the diet?

A

Gluconeogenesis

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30
Q

When blood glucose levels are low (glucose stores are depleted) which organ makes glucose from other intermediates and then secretes it into the body for use?

A

The liver

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31
Q

True or False: The brain does not requires a minimum level of glucose for proper function

A

False - The brain DOES requires a minimum level of glucose for proper function

32
Q

The brain uses ~25% of glucose pool daily. It does not readily use other sources of fuel, such as ___

A

fatty acids

33
Q

True or False: RBC’s lack mitochondria and cannot release energy from amino acids/fatty acids

A

True

34
Q

What other molecules (besides pyruvate) can the liver use to make glucose via: gluconeogenesis?

A

1) Adipocytes = Glycerol
2) Skeletal muscle = Amino acids
3) Anaerobic Metabolism = Lactate

35
Q

How does long-term activity of gluconeogenesis in the liver, due to starvation and malnutrition, affect muscle tissue?

A

Leads to muscle tissue breakdown

36
Q

What does a baseline activity level of gluconeogenesis in the liver help prevent?

A

Lactate accumulation in the blood

37
Q

Describe the Cori Cycle

A
38
Q

In the Cori Cycle, the liver uses gluconeogenesis to convert lactate to ___

A

glucose

39
Q

In the Cori Cycle, lactate travels in the blood to the ___

A

liver

40
Q

True or False: Mutations in gluconeogenesis enzymes reduce body’s ability to maintain blood glucose levels

A

True

41
Q

What are four clinical features of gluconeogenesis disorders?

A

1) Hypoglycemia
2) Fatigue
3) Lightheadedness
4) Fainiting

42
Q

Patients with disorders of ____ can have difficulty maintaining minimum glucose levels, especially in between meals or overnight

A

gluconeogenesis

43
Q

Defects in gluconeogenesis can lead to _______, a condition in which there is a build-up of acid

A

Lactic acidosis

44
Q

True or False: Defects in gluconeogenesis can lead to reduced ability of liver to convert lactate to glucose, leading to lactate accumulation in the blood

A

True

45
Q

True or False: Glycolysis and Gluconeogenesis are tightly controlled by a combination of mechanisms within the liver

A

True

46
Q

Insulin is released from ___ cells in response to ___ blood glucose, which acts on many cells

Glucagon is release from ___cells in response to ___ blood glucose, which acts primarily in the ____

A

beta cells; high

alpha cells; low; liver

47
Q

In a well fed state, the pancreas secretes ____, which promotes ____

A

insulin; glycolysis

48
Q

In fasting/starvation conditions, pancreas secretes ___, which promotes ____

A

glucagon, gluconeogenesis

49
Q

How many reversible and irreversible reactions does glycolysis contains?

A

7 reversible reactions
3 irreversible reactions

50
Q

Gluconeogenesis must “bypass” irreversible reactions of glycolysis using different ___

A

enzymes

51
Q

True or False: Both glycolysis and gluconeogenesis in a liver cell will be active at the same time

A

False - only glycolysis and gluconeogenesis in a liver cell will be active at the same time, to prevent futility

52
Q

What enzyme mediates the first irreversible reaction of glycolysis

A

Hexokinase
- When blood glucose levels rise and glucose enters the cell, it is phosphorylated by hexokinase
-Higher glucose outside the cell causes an inward flow of glucose

53
Q

In the first irreversible reaction of glycolysis, glucose is phosphorylated. What is the effect?

A

Glucose is trapped inside of the cell

54
Q

What is the last step of gluconeogenesis?

A

G6P is converted to glucose via: G6P

  • Blood glucose is low
  • Higher glucose inside cell causes outward flow of glucose
55
Q

True or False: G6Phosphatase is a gluconeogenesis bypass enzyme that is highly expressed in the liver

A

True

56
Q

Low cellular levels (low ATP, high ADP and high AMP) activate ____ and inhibit _____

A

Activate glycolysis
Inhibit gluconeogenesis

57
Q

What two glycolytic enzymes are activated under low cellular level energy conditions? (low ATP, high ADP, and high AMP)

A

PFK1 and Pyruvate kinase

58
Q

High ATP inhibits ___ and activates ___

A

glycolysis; gluconeogenesis

59
Q

Which glycolytic enzymes are inhibited when there is high cellular energy levels (high ATP)?

A

PFK1 and Pyruvate Kinase

60
Q

True or False: Bypass enzymes are no longer inhibited under high cellular energy conditions, since gluconeogenesis requires sufficient ATP

A

True

61
Q

Under high glucose conditions, the pancreas will secrete insulin, promoting ___ in the liver and activation of _____ (enzyme)

Covalent regulation !!!

A

Under high glucose conditions, the pancreas will secrete insulin, promoting glycolysis in the liver and activation of Protein Phosphatase-1 (enzyme)

62
Q

Under low glucose conditions, the pancreas will secrete glucagon, promoting ___ in the liver and activation of _____ (enzyme)

A

Under low glucose conditions, the pancreas will secrete glucagon, promoting gluconeogenesis in the liver and activation of Protein Kinase A (enzyme)

63
Q

What enzyme mediates the final step of glycolysis?

A

Pyruvate kinase

64
Q

Insulin activates Protein Phosphatase 1, which removes phosphate from pyruvate kinase, activating it and promoting ___

A

glycolysis

65
Q

Glucagon activates PKA, which adds a phosphate to pyruvate kinase, thereby inhibiting ____

A

glycolysis

66
Q

How does F2,6BP exert its effects?

A

Allosteric Regulation

67
Q

P2,6BP is a potent activator of ____ and inhibitor of ____

A

P2,6BP is a potent activator of glycolysis and inhibitor of gluconeogenesis

68
Q

How does insulin activation of PP1 affect F2, 6BP?

A

Insulin activation of PP1 leads to an increase in F2,6BP

69
Q

Does glucagon activation of PKA lead to an increase or decrease in F2,6BP levels?

A

Glucagon activation of PKA lead to a DECREASE in F2,6BP levels

70
Q

Insulin increases G2,6BP, thereby activating which irreversible glycolysis enzyme?

A

PFK1

note: bypass enzyme is inactivated

71
Q

High F2,6BP activates ___ and inhibits ____

Low F2,6B6 reduces activation of which enzyme? And removes inhibition of which enzymes?

A

High F2,6BP activates glycolysis and inhibits gluconeogenesis

Low F2,6BP reduces activation of PFK1 and removes inhibition of bypass enzymes

72
Q

A person who has been in a well-fed state for a long time will have elevated ___ enzymes and decrease in ___ enzymes

A

increase glycolysis enzymes
decreases gluconeogenesis enzymes

73
Q

How will epinephrine increase blood glucose?

A

Promoting gluconeogeneis in liver by activating PKA

74
Q

Low blood glucose stimuli activates glucagon, which activates PKA and increases gluconeogenesis and blood glucose.

What stimuli activates this pathway, but with epinephrine?

A

Stress and fear

75
Q

Insulin will increase glycolysis in liver and skeletal muscles.

However, glucagon will only increase gluconeogenesis in the liver and will have no effect in ____

A

skeletal muscles

76
Q

How does epinephrine affect skeletal muscle and liver?

A

Epinephrine will INCREASE glycolysis in the skeletal muscle

Epinephrine will INCREASE gluconeogenesis in the liver

Biochemistry I/II (23 decks)

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