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Biochemistry > Metabolism > Flashcards

Metabolism Flashcards

1
Q

What is a glucose with two phosphate groups attached to it called?

A

Fructose-1,6 bis-phosphate

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2
Q

Is Fructose-1,6 bis-phosphate stable?

A

No

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3
Q

What does Fructose-1,6 bis-phosphate split into?

A

DHAP and glycealdehyde-3-phosphate

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4
Q

What happens to DHAP?

A

It is converted into glycealdehyde-3-phosphate

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5
Q

How many carbons does pyruvate have?

A

3

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6
Q

What does phosphofructokinase catalyse?

A

The formation of fructose-1,6-bisphosphate

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7
Q

Can Phosphofructokinase regulate glycolysis?

A

Yes, it speeds up or slows down the process depending on what is needed by the cell

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8
Q

What is the enzyme called that converts glucose to glucose-6-phosphate?

A

Hexokinase

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9
Q

What is the enzyme called that converts glucose-6-phosphate to fructose-6-phosphate?

A

Phosphoglucose-isomerase

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10
Q

What is the enzyme called that converts fructose-6-phosphate to fructose-1,6-bisphosphate?

A

Phosphofructokinase

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11
Q

What does DHAP stand for?

A

Dihydroxyacetonephosphate

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12
Q

What is the enzyme called that converts DHAP to glycealdehyde-3-phosphate?

A

Triose phosphate isomerase

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13
Q

What is the enzyme called that converts fructose-1,6-bisphosphate to DHAP and glycealdehyde-3-phosphate?

A

Fructose bisphosphate aldolase

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14
Q

Can glucose with a phosphate attached readily cross the membrane?

A

No

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15
Q

Is phosphoenolpyruvate (PEP) an unstable molecule?

A

Yes, it donates its phosphate group to ADP making it ATP

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16
Q

What acts as the source of phosphoryl groups that can be transferred to ADP to
regenerate ATP in mammal’s muscle cells?

A

1,3-bisphosphoglycerate, phosphoenolpyruvate, creatine phosphate

17
Q

Metabolic pathways that require energy and are often biosynthetic are called

A

anabolism

18
Q

The catalytic mechanism in which an isomerization takes place by a ketose to form an aldos is
via an _____intermediary.

A

enediol

19
Q

What common structure is found in ATP, NAD, FAD and CoA-SH?

A

Adenosine diphosphate (except for the extra phosphate at 3 ́-C)

20
Q

Why is there a common structure is found in ATP, NAD, FAD and CoA-SH?

A

These molecules may have evolved from the RNA catalysts in early life

21
Q

Creatine is available for purchase in health food stores? What could it be good for?

A

Store chemical energy in the form of creatine-phosphate, ready to make ATP.

22
Q

In intravenous injection of fructose in the blood of a subject, lactate content in the blood increased significantly more than when the corresponding amount of glucose was injected. How
can this be explained?

A

The fructose-1-phosphate pathway (see Figure 16.13 in Stryer) forms glyceraldehyde 3-
phosphate in fewer steps. Phosphofructokinase, a key control enzyme, is bypassed. Collectively,
fructose is metabolized more quickly into pyruvate, without being controlled at the PFK step (occurs in glucose catabolism). With oxygen supply limited, the final product pyruvate is reduced to lactate to regenerate NAD+.

23
Q

Xylose has the same structure as glucose with the exception that C-5 in xylose has a hydrogen
as a substituent where glucose has a hydroxymethyl group. In the presence of xylose, the ATP
hydrolysis in the active site increases in hexokinase. How can this be explained?

A

Xylose is not a “perfect” substrate and does not induce the same conformational change of
hexokinase. As a result the enzyme active site does not exclude water completely, thereby ATP
hydrolysis increases. Also, xylose does not have the C-6 linked OH group (as in glucose) to
accept phosphate from ATP.

24
Q

The level of ATP (or rather the cell’s energy status) has an important regulatory function on
metabolism. How does an increased concentration of ATP in the cell affect the activity of the pyruvate kinase?

A

Inhibits

25
Q

The level of ATP (or rather the cell’s energy status) has an important regulatory function on
metabolism. How does an increased concentration of ATP in the cell affect the activity of the Phosphofructokinase?

A

Inhibits

26
Q

The level of ATP (or rather the cell’s energy status) has an important regulatory function on
metabolism. How does an increased concentration of ATP in the cell affect the activity of the aldolase?

A

No effect

27
Q
  1. The reduced form of flavin adenine dinucleotide is:
    A) FAD B) FADH C) FAD+ D) FADH2
A

D) FADH2

28
Q

Which of the following is electron donor in reductive biosynthesis?
A) NADH B) NADP C) NADPH D) FAD E) FADH2 F) ATP

A

C) NADPH

29
Q
  1. Which of the following statements best describes NADH and NADPH?
    A) NADH is used mainly for ATP production, while NADPH is used for biosynthesis.
    B) NADPH is used mainly for ATP production, while NADH is used for biosynthesis.
    C) For both ATP production and biosynthesis, preferably NADH is used instead of NADPH.
    D) For both ATP production and biosynthesis, NADPH is preferably used instead of NADH.
A

A) NADH is used mainly for ATP production, while NADPH is used for biosynthesis.

30
Q

What is meant by substrate level-phosphorylation?
A) phosphorylation of AMP with ATP
B) ATP synthesis where the phosphate donor is a substrate capable of phosphoryl transfer
C) Phosphorylation of glycolytic intermediates
D) Phosphorylation of ATP coupled to a gradient of protons
E) ATP and AMP synthesized from two molecules of ADP

A

B) ATP synthesis where the phosphate donor is a substrate capable of phosphoryl transfer

31
Q

Metabolic processes are regulated by
A) Control of the amount of enzyme at the transcription level
B) Allosteric control of enzyme activity
C) Access to substrates through Compartmentalization
D) Everyone is correct

A

D) Everyone is correct

32
Q
  1. Which of the following reactions implies a significant thermodynamic driving force (G
    negative) for glycolysis in vivo?
    a. Glucose 6-phosphate → fructose 6-phosphate
    b. Dihydroxyacetone phosphate → Glyceraldehyde 3-phosphate
    c. Glyceraldehyde 3-phosphate + phosphate + NAD+ → 1,3-bisphosphoglycerate + NADH + H+
    d. 2-Phosphoglycerate → Phosphoenolpyruvate + Water
    e. Phosphoenolpyruvate + ADP → Pyruvate + ATP
A

e. Phosphoenolpyruvate + ADP → Pyruvate + ATP

33
Q

Where are the major sites of glycogen storage?

A

Liver and skeletal muscles

34
Q

Where is glycogen syntesis and degradation regulated to maintain blood glucose levels?

A

Liver

35
Q

T/F in muscles glycogen synthesis and degradation is regulated to meet the needs of the muscle itself

A

T

Biochemistry (15 decks)

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