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Foundations of Medicine > FOM 3.5.1 > Flashcards

FOM 3.5.1 Flashcards

1
Q

True or false: The activity of some enzymes simply relies on how much substrate is available.

A

True

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2
Q

True or false: If NADH is not regenerated to NAD+, then the TCA cycle quits working.

A

True

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3
Q

Under anaerobic conditions, NADH generated in the cytosol is regenerated to NAD+ via ___(enzyme)_________

A

Lactate Dehydrogenase

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4
Q

True or false: Aldolase cleaves fructose-2,6-bisphosphate into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. These two molecules are further metabolized in glycolysis.

A

False. Dat’s not tru

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5
Q

True or false: In the liver, fructose-2,6-bisphosphate acts as a feedforward allosteric activator of pyruvate kinase.

A

False

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6
Q

Pyruvate dehydrogenase kinase is __(activated/inhibited)__ by the metabolite ___________.

A

Inhibited, pyruvate

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7
Q

Dichloroacetate is an analogue of _______ and has the potential of reducing lactate concentrations by targeting __(enzyme)___.

A

pyruvate, pyruvate dehydrogenase kinase

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8
Q

True or false: Glycolysis and gluconeogenesis are activated by the same small molecules and inhibited by the same small molecules.

A

False

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9
Q

High levels of __(TCA cycle intermediate)___, indicate sufficient energy sources. Therefore, this small molecule is an allosteric activator of ___(enzyme)____ that controls the rate of fatty acid synthesis. This exemplifies regulatory crosstalk between different pathways.

A

Citrate, acetyl CoA carboxylase

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10
Q

True or false: Membranes do not play a role in metabolism.

A

False

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11
Q

One example of whole body metabolism is: ________

A

1) Ketone generation by the liver to feed brain and muscle 2) The Cori cycle 3) The glucose-alanine cycle

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12
Q

Provide a reason why our bodies can have multiple isozymes of the same enzyme, given that all isozymes catalyze the same reaction. _____________________________

A

Different isosymes often have unique regulatory responses that function within the needs of the tissue where that isozyme is expressed

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13
Q

True or false: Compared to glucokinase, hexokinase has a lower affinity for glucose. This lower affinity allows hexokinase to function in muscle even when glucose concentration is relatively low.

A

False

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14
Q

True or false: Compared to glucokinase, hexokinase has a lower affinity for glucose. This lower affinity allows hexokinase to function in muscle even when glucose concentration is relatively low.

A

False

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15
Q

True or false: When proteins are regulated by “covalent modification,” Covalent modification normally refers to phosphorylation.

A

False

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16
Q

One benefit of a regulatory _______ is that a very limited number of signaling molecule can influence the activities of a large number of enzyme molecules. In other words, the regulatory signaling gets amplified.

A

Cascade

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17
Q

When blood glucose is low, glucagon secretion goes __(up/down)__. This change in glucagon causes a/an __(increase/decrease)___ in cellular cAMP concentration. In the liver, phosphofructokinase activity ___(increases/decreases)_, consistent with the need to __(increase/decrease)__ hepatic glucose secretion.

A

up, increase, decreases, increases

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18
Q

True or false: Control of one enzymatic step in a metabolic pathway can control the flux through that pathway.

A

True, if the rate limiting step

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19
Q

True or false: Excessive alcohol consumption can cause hypoglycemia because the alcohol metabolism converts all available NAD+ to NADH. The cell’s attempt to regenerate NAD+ by transferring electrons to pyruvate can compete with the need to use pyruvate as a substrate for gluconeogenesis, thus causing hypoglycemia.

A

True

20
Q

True or false: One of the arguments used to criticize the use of high fructose corn syrup is that fructose metabolism bypasses the regulatory steps in glycolysis at hexokinase/glucokinase and phosphofructokinase.

A

True

21
Q

What is dichloroactetate structurally analagous to? How does that explain its function?

A

Pyruvate. That explains its inhibition of pyruvate dehydrogenase kinase

22
Q

What are some mechanisms of regulation?

A

1) Substrate availability 2) Product buildup/Product inhibition 3) Regulation by specialty metabolite (allosteric) 4) Allosteric regulation by intermediate metabolites - Feed forward (not common) - Feed back inhibition - Coordination b/t pathways 5) Tissue specialization 6) Tissue specific isozyme expression 7) Covalent modifications 8) Change Enzyme [] 9) Regulatory cascade 10) Hormone regulation

23
Q

As more substrate is available, what happens to Vo?

A

The Vo increases until enzyme has reached saturation

24
Q

Why is there reduced activity of TCA cycle enzymes in hypoxic tissue?

A

NADH builds up inside the mito due to the loss of function of the ETC (lack of O2 as final e- acceptor)

25
Q

What is an example of a specialty metabolite that allosterically regulates glycolysis?

A

Fru-2,6-BP, AMP

26
Q

What catalyzes the formation of Fru-2,6-BP? And, degradation?

A

PFK-2, FBPase-2

27
Q

What is another molecule that can be made when the pathway of glycolysis is diverted? (hint: it affects the affinity of oxygen binding in erythrocytes)

A

2,3-BPG (2,3-bisphosphoglycerate)

28
Q

What is the only straightforward example of feed forward activation in glycolysis?

A

Fru-1,6-BP allosterically activates liver pyruvate kinase

29
Q

Another example of feed forward activation comes when an inhibitor is inhibited. What is this example?

A

Pyruvate inhibits PDK, resulting in increased activity of pyruvate dehydrogenase

30
Q

What molecule within the glycolysis pathway inhibits PFK? (Feedback inhibition)

A

PEP

31
Q

Name some of the molecules involved in the coordination of pathways w/ Acetyl CoA carboxylase that forms Malonyl-CoA. Indicate if they activate or inhibit.

A

Insulin (+) Glucagon (-) Citrate from TCA (+) AcylCoA (-) Glutamate AA (+)

32
Q

What does malonyl-CoA inhibit?

A

Caritine-Palmitoyltransferase-I

33
Q

What are some examples of compartmentalization?

A

1) FA cata (beta oxi) v. anabolism (biosynthesis) 2) e- shuttling into mito

34
Q

What are the two e- shuttling systems?

A

Malate-aspartate shuttle, Glycerophosphate shuttle

35
Q

An example of tissue specialization is ketogenesis and ketogenolysis. Where do these occur?

A

genesis: Liver, lysis: Brain, Muscle can do both

36
Q

The Cori cycle is used to recycle what? Explain how it works.

A

Lactate. Muscle turns glucose into lactate, then the liver turns the lactate back into glucose.

37
Q

What is a product of the glucose-alanine cycle during gluconeogenesis in the liver?

A

Urea

38
Q

What is a perfect example of isozymes used in glycolysis?

A

Hexokinase and glucokinase

39
Q

What are some examples of covalent modifications? (2)

A

Phosphorylation and Acetylation

40
Q

What are the purposes of an enzyme cascade?

A

Amplification of the original signal, faster response to stimuli

41
Q

What is the second messenger used in the hormonal activation of glycogen phosphorylase?

A

cAMP

42
Q

Give an example of when regulation is bypassed.

A

Alcohol metabolism

43
Q

Alcohol metabolism results in the generation of what cofactor?

A

NADH

44
Q

How does the body try to recycle some of the NADH produced during alcohol metabolism?

A

Lactate prod or Increased ETC usage

45
Q

Describe the cascade that goes from low blood sugar to gluconeogenesis.

A

Foundations of Medicine (79 decks)

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