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Cell Biology and Genetics > Regulating enzyme function > Flashcards

Regulating enzyme function Flashcards

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1
Q

What are the different types of regulation of enzyme activity?

A

Short term

Long term

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2
Q

What are the different types of short term regulation of enzyme activity?

A

Changing substrate and product concentration

Changing enzyme conformation

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3
Q

How can enzyme conformation be changed?

A

Allosteric regulation

Proteolytic cleavage

Chemical modification

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4
Q

What are the different types of long term regulation?

A

Change in rate of protein synthesis

Change in rate of protein degradation

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5
Q

What are isoenzymes?

A

Catalyse same reaction

but have different structure and hence different kinetic properties

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6
Q

What is an example of changing product concentration regulating enzyme activity?

A

Product inhibition

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7
Q

What is product inhibition?

A

Product of a reaction inhibits the forward reaction

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8
Q

What are the two different states of allosteric enzymes?

A

Tense state, T state

Relaxes state, R state

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9
Q

What is the affinity of allosteric enzymes in the T state for their substrate?

A

Low affinity

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10
Q

What is the affinity of allosteric enzymes in the R state for their substrate?

A

High affinity

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11
Q

What shape does a graph of x axis-substrate concentration against y axis-reaction velocity for allosteric enzymes take?

A

Sigmoid curve

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12
Q

Why does a graph of x axis-substrate concentration against y axis-reaction velocity for allosteric enzymes take a sigmoid curve shape?

A

Enzyme initially in T state
binding of substrate is hard

After first substrate has bound, enzyme converted to R state
binding of substrates is easy

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13
Q

What do allosteric activators do?

A

Bind to enzyme

increase proportion of enzymes in R state

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14
Q

What do allosteric inhibitors do?

A

Bind to enzyme

increase proportion of enzymes in T state

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15
Q

What is an example of a chemical group commonly added to/removed from enzymes?

A

Phosphate group

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16
Q

What type of enzyme is responsible for adding phosphate groups to enzymes?

A

Protein kinases

17
Q

Where do protein kinases get the phosphate group from?

A

Terminal phosphate of ATP

18
Q

What type of enzyme is responsible for removing phsophate groups from enzymes?

A

Protein phosphatase

19
Q

What type of reaction is involved in removing phosphate groups from enzymes?

A

Hydrolysis

20
Q

Why is phosphorylation effective at regulating enzyme function?

A

Adds negative charges

A phosphate group can make hydrogen bonds

Rate of phosphorylation/dephosphorylation can be adjusted

Allows for amplification

21
Q

What is an enzyme cascade?

A

Series of reactions

each catalysed by an enzyme

22
Q

How do enzyme cascades give amplification?

A

Each enzyme can catalyse many reactions

producing many product molecules

23
Q

What is reciprocal regulation?

A

Same signal activates one enzyme

inhibits another enzyme

24
Q

What is the purpose of reciprocal regulation?

A

Activate one pathway, inhibit another pathway

these pathways are usually opposites of one another

25
Q

What is a zymogen?

A

Inactive form of enzyme

26
Q

How are zymogens converted into active enzymes?

A

Through the action of another active enzyme

27
Q

What is the initial form of digestive enzymes?

A

Zymogens

28
Q

How are digestive enzyme zymogens activated?

A

Proteolytic cleavage by other active enzymes

29
Q

What is the enzyme largely responsible for activating digestive enzyme zymogens?

A

Trypsin

30
Q

What inhibits trypsin?

A

Pancreatic trypsin inhibitor

31
Q

What is a1-antitrypsin?

A

Plasma proteins

inhibits range of proteases

32
Q

What is the molecular cause of emphysema?

A

Defect in a1-antitrypsin

33
Q

What does a defect in a1-antitrypsin cause in emphysema?

A

Elastase in lungs is not inhibited

digests elastin in lungs

34
Q

What is the target of short term regulation of enzyme activity?

A

Enzymes already present in cell

35
Q

What is the target of long term regulation of enzyme activity?

A

Change enzyme amount in cell

36
Q

How does short term regulation differ from long term regulation in terms of time?

A

Long term takes longer to have effect

and lasts longer

Cell Biology and Genetics (32 decks)

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