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Introduction to Genetics & Biochemistry > Metabolic Control > Flashcards

Metabolic Control Flashcards

1
Q

Why do we need metabolic control?

A

In order to regulate the large number of biochemical pathways in the cell to maintain homeostasis.

To provide products at the rate they are needed.

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2
Q

What are the three levels of metabolic control?

A
  1. Modulation.
  2. Interconversion.
  3. Changes in ezyme biosynthesis.
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3
Q

Which is the slowest form of metabolic control?

A

Changes in enzyme biosynthesis.

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4
Q

What is the fastest form of metabolic control?

A

Modulation.

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5
Q

How does modulation give metabolic control?

A

Rapid yet modest changes in enzyme activity in response to modest changes in metabolites.

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6
Q

Which form of metabolic control sees a rapid yet modest change in enzyme activity in response to modest changes in metabolites?

A

Modulation.

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7
Q

How does interconversion control metabolism?

A

Slower, larger scale activation or suppression of pre-formed pools of enzymes.

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8
Q

Which type of metabolic control sees slower yet larger scale activation or suppression of pre-formed pools of enzymes?

A

Interconversion.

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9
Q

Which type of metabolic control sees slow but major changes in gene expression via transcription and translation?

A

Changes in enzyme biosynthesis.

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10
Q

How do changes in enzyme biosynthesis regulate metabolism?

A

By making slow but major changes in gene expression via transcription and translation.

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11
Q

Which of these is the quickest? Which is the slowest?

a. Enzyme synthesis / degradation

b. Enzyme modification.

c. Enzyme activity.

A

Quickest - enzyme activity (milliseconds).

Slowest - enzyme synthesis / degradation (minutes to hours).

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12
Q

In modulation, what controls enzyme activity?

A

Inhibitors and activators.

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13
Q

What are the two types of inhibitors that can control enzyme activity?

A

Competitive inhibitors and non-competitive inhibitors.

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14
Q

How do competitive inhibitors work?

A

Competitive inhibitors mimic the structure of the substrate and bind to the active site of the enzyme, preventing the substrate from binding.

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15
Q

How do non-competitive inhibitors work?

A

Non-competitive inhibitors bind elsewhere (not on the active site) of the enzyme. This changes the binding site, making it more difficult or impossible for the substrate to bind.

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16
Q

In modulation, what can act as a control point of a pathway or cycle?

A

Some enzymes.

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17
Q

What is feedback / product inhibition?

A

Where the end product of the pathway inhibits the first step.

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18
Q

What type of metabolic control is phosphorylation (e.g. ATP to ADP, GTP to GDP etc.) an example of?

A

Interconversion.

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19
Q

Interconversion is the ……………. of an enzyme, which then …………….. or ……………….. an enzyme’s activity.

A

Modification, inhibition, activation.

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20
Q

Does the action of glycogen synthetase in turning glucose to glycogen require energy input, or is energy released?

A

Energy input is required.

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21
Q

Does the action of glycogen phosphorylase to break down glycogen into glucose release or require energy?

A

It releases energy.

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22
Q

Which hormone controls phosphorylation in glycogen synthesis? Why?

A

Adrenaline. The levels of adrenaline increase under stress which switches glycogen b synthetase off and switches glycogen a synthetase on.

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23
Q

Which form of glycogen synthetase is switched off and which is switched on in when adrenaline is released, triggering the use of glucose for energy and diverting it away from being stored as glycogen?

A

Glycogen a synthetase is switched on and glycogen b synthetase is switched off.

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24
Q

Does phosphorylation require energy input? Does it require anything else?

A

Yes, it requires ATP and phosphorylase kinase.

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25
Q

What two things does phosphorylation require?

A

Energy (in the form of ATP) and phosphorylase kinase.

26
Q

What do protein kinases do to other proteins?

A

They phosphorylate other proteins.

27
Q

Are protein kinases:

a. simple proteins.
b. complex signalling cascades.
c. both.

A

c. they can be both!

28
Q

What proportion of the human genome is protein kinases?

a. 0.17%.
b. 1.7%.
c. 17%.

A

b. 1.7%.

29
Q

Do specific protein kinases / protein phosphorylases have specific functions?

A

Yes.

30
Q

What component of cell membranes can sense hormone or external factors which activate protein kinases and protein phosphatases?

A

Sensors.

31
Q

What is the following a basis for?:

‘Phosphorylase kinase A is interconverted by another protein kinase, now known as protein kinase A’

A

A signal transduction cascade.

32
Q

In a signal transduction cascade, a hormone detected by sensors in the cell membrane activates a protein kinase. What happens next?

A

The protein kinase phosphorylates a second protein kinase, which is activated to phosphorylate another protein kinase, which phosphorylates the next protein kinase and so on!

33
Q

In muscle, interacting ……………… form a ………………… …………………… to activate glycogen breakdown. The cascade eventually activate the enzyme …………………. ……………….. to release glucose.

A

Kinases, signalling pathway, glycogen phosphorylase.

34
Q

Adrenaline cannot enter cells to begin a cascade, which secondary hormone is used?

A

cAMP?

35
Q

What is the hormone cAMP?

A

A secondary hormone used to begin signalling cascades (e.g. in the breakdown of glycogen) because adrenaline cannot enter the cell.

36
Q

How can protein kinase A affect gene expression?

A

By phosphorylating a transcription factor.

37
Q

What does protein kinase A phosphorylate to affect gene expression?

A

A transcription factor.

38
Q

Other than adrenaline, what can affect gene expression via Ca++ and/or protein kinase C?

A

Other hormones and growth factors.

39
Q

When was the human genome first sequenced in the human genome project?

A

2000.

40
Q

Each cell in the body contains …………. set of genes, but each cell only …………………. some genes.

A

Every, expresses.

41
Q

What factors can influence which genes a specific cell expresses at a given time?

A

Time of day, activity levels, environment, dietary intake etc.

42
Q

What does totipotent mean, in terms of the DNA contained in a cell.

A

It means that a cell contains the full complement of DNA.

43
Q

How is gene expression mainly controlled?

A

Through control of the initiation of transcription, the structure of the gene and its interaction with RNA polymerase.

44
Q

What is the function of RNA polymerase in transcription?

A

It binds to the promoter of the gene, initiating gene transcription.

45
Q

Name the three RNA polymerases found in eukaryotes.

A
  1. Poly I (rRNA).
  2. Poly II (mRNA).
  3. Poly III (tRNA and SSrRNA).
46
Q

Which type of RNA does Poly I work on?

A

rRNA.

47
Q

Poly II works on which type of RNA?

A

mRNA.

48
Q

Poly III works on which types of RNA?

A

tRNA and SSrRNA.

49
Q

Every gene has a …………….. sequence of bases in the poly II promoter, specifically to start transcription.

A

Consensus.

50
Q

Name the consensus sequences.

A
  1. TATA box.
  2. CAAT box.
  3. GC box.
51
Q

What are the proteins called that can bind to specific DNA sequences to activate or repress transcription?

A

Specific transcription factors.

51
Q
A
52
Q

True or false? Specific transcription factors are always close to the promoter in the DNA sequence.

A

False - they can be close to the promoter or they can be 1,000s of base pairs away (enhancers).

53
Q

What are specific transcription factors called that are 1,000s of base pairs away from the promoter?

A

Enhancers.

54
Q

Do specific transcription factors inhibit or repress transcription?

A

They can do either!

55
Q

Enzymes that catalyse ……………. reactions tend to act as …………….. points.

A

Irreversible, control.

56
Q

Why do enzymes which catalyse irreversible reactions tend to act as control points?

A

Irreversible reactions tend to require a lot of energy input, so control points can prevent this energy from being wasted.

57
Q

Why are checkpoint enzymes often at the start of an enzymatic pathway?

A

To halt the pathway early, so that ‘useless’ products do not accumulate.

58
Q

How can having multiple transcription factors for one gene increase regulation, for example in the control of the albumin gene in the liver?

A

Expression of the albumin gene in the liver requires three separate transcription factors, all of which are produced under different conditions which increases regulation.

59
Q

Transcription factors for gene expression are often homodimers or heterodimers. What do these terms mean?

A

Dimers are molecules with two part. In homodimers both parts are the same. In heterodimers the parts are different.

60
Q

If a transcription factor is a heterodimer, why does this lead to tighter regulation of gene transcription?

A

Heterodimers are harder to make because they need two different components.

61
Q
A

Introduction to Genetics & Biochemistry (21 decks)

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