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Biology > Chapter 4- Enzymes > Flashcards

Chapter 4- Enzymes Flashcards

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1
Q

Why is enzyme described as extracellular?

A

-works outside cells

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2
Q

What should you keep constant when changing conc. of substrate?

A
  • pH
  • temp
  • enzyme conc.
  • vol of solution
  • conc. of cofactors
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3
Q

explain the graph that is linear and then plateaus

Increasing substrate conc. against rate of product formation

A
  • linear part means more successful collisions with active site at inc. starch conc. thus, more ESC at increasing starch conc. so more product formation in given time.
  • plateau means all active sites occupied as enzyme working at Vmax. So further inc. in starch conc has no affect on rate. Enzyme conc. now limiting factor.
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4
Q

Why is it important to keep pH constant?

A
  • so H and ionic bonds unaffected
  • so tertiary structure unaltered
  • so enzyme doesn’t denature
  • so substrate complementary to active site

-so results are valid as rate of reaction will vary if pH changes and to ensure only 1 independent variable changed

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5
Q

Explain why enzyme x is bale to break down both a and b (diagram)

A
  • have similar 3D shape
  • e.g. of similarity
  • both are complementary to active site
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6
Q

Suggest why DEG contaminated (harmful) wines with higher ethanol conc (not harmful) may result in less DEG poisoning than contaminated wines with lower ethanol conc.

A
  • ethanol competes with DEG

- when at higher conc. ethanol more likely to bind to active site and thus less toxic product formed

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7
Q

why the lock-and-key and induced-fit explanations are termed models?

A

Simple representations of the process

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8
Q

why most scientists now accept the induced-fit model rather than the lock-and-key model?

A

-it has now been found that the enzyme changes shape during the reaction

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9
Q

Rate of product formation was slower at 1c when catalysed with enzyme from non Antarctic fish than Antarctic fish. Why?

A

Not at optimism temperature so fewer collisions between active site and substrate

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10
Q

how a more flexible structure might help enzyme work faster at lower temperatures?

A
  • easier for substrate to bind to active site
  • more bonds can form
  • easier for active site to change shape
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11
Q

how the structure of the enzymes may differ in Antarctic and non-Antarctic fish?

A
  • diff amino acid sequence in primary structure

- diff quaternary structure as polypeptide will fold differently

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12
Q

how the DNA of the Antarctic and non-Antarctic fish might differ?

A
  • diff base sequence

- diff ratio of bases

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13
Q

why the loss of enzymes might be undesirable

A

Enzyme could have future application

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14
Q

Explain the term biological catalysts

A

-speed up metabolic reactions

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15
Q

One problem with using celery as source of catalase in investigation and how to minimise problem?

A
  • diff samples have diff conc of catalase

- extract source for whole experiment from same plant

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16
Q

How to check reliability of data?

A
  • repeat experiment
  • identify anomalous results
  • calculate mean
  • calculate SD
  • compare results with book values
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17
Q

How Cl- ions increase the rate of reaction?

A
  • acts as a cofactor
  • Cl- binds to enzyme
  • ESC forms more quickly
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18
Q

Explain the effect of increasing the conc. of substrate on the rate of reaction

A
  • more substrate molecules enter the active site
  • more ESC formed
  • at high conc all active sites occupied
  • reaches Vmax
  • at high substrate conc. the enzyme conc. is the limiting factor
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19
Q

Explain why x acts as a competitive inhibitor to y

A
  • both have similar shape
  • both are complementary to active site of enzyme
  • give E.g. of similarity
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20
Q

Explain the effect of increasing the substrate concentration in the presence of an inhibitor

A
  • inhibitor competes for active site
  • occupies active site reversibly
  • thus, fewer active sites available for substrate
  • at higher conc of substrate the substrate can outcompete the inhibitor and reduce the chance of inhibitor binding to active site
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21
Q

-describe how an enzyme breaks down a substrate

A
  • substrate complementary to active site
  • substrate binds to active site
  • in an induced fit
  • forms ESC
  • straining of bonds in substrate
  • forms EPC
  • products leave active site
22
Q

How would you draw a line on a graph to show the action of a competitive inhibitor?

A
  • below substrate line

- doesn’t peak or plateau

23
Q
  • x acts as a competitive inhibitor of y

What can you conclude about the structure of x

A
  • similar shape to substrate

- complementary to active site

24
Q

This enzyme action can break down elastin.

Use the example of elastin breakdown to explain the induced-fit hypothesis of enzyme action

A
  • elastin is substrate
  • substrate binds to active site
  • enzyme changes shape to get tighter fit between active site and substrate
  • more bonds form between active site and enzyme
  • forms ESC
  • straining of bonds in substrate
  • activation energy reduced
25
Q

why different enzymes are involved in each stage?

A
  • enzymes are specific
  • substrates are different shapes
  • active site and substrate are complementary
  • substrate binds to active site
  • forms ESC
26
Q

Explain why the activity of the enzyme falls to 0 at pH 7

A
  • pH much higher than optimum
  • hydrogen and ionic bonds break
  • active site shape altered
  • enzyme denatured
  • substrate no longer fits active site
27
Q

What is meant by ‘catalyst’

A

-a substrate that speeds up a reaction without being used up in the reaction

28
Q

What is meant by activation energy and how does the presence of an enzyme affect it?

A
  • Ea is the minimum amount of energy needed to start a reaction
  • enzymes lower the Ea
29
Q

Enzymes are globular proteins. What does this mean in terms of quaternary structure?

A

Multiple polypeptide chains coiled together to make a compact structure

30
Q

Why is the tertiary structure of an enzyme essential to its function?

A
  • tertiary structure determines specific shape of active site
  • active site is only complementary to specific substrate
  • any change in shape will mean the enzyme cannot catalyse that reaction
31
Q

How does the maltase enzyme interact with maltose?

A
  • maltose is a complementary shape to the active site of maltase
  • ESC formed
  • reaction occurs, breaking the glycosidic bond between disaccharide
  • 2 glucose monosaccharides are released
32
Q

What is the ‘lock and key’ model of enzyme action?

A
  • substrate fits into the active site of enzyme in same way that key fits into lock
  • they are exactly complementary shapes
33
Q

Why ‘induced fit’ model considered to be better theory than ‘lock and key’ model?

A
  • enzymes are not rigid structures
  • ESC changes shape slightly
  • ensures tighter binding in active site
34
Q

Which enzyme inhibitor would be more likely to have temporary affects and why?

A
  • competitive inhibitor
  • has similar shape to substrate
  • occupies active site and prevents substrate from binding
  • no reaction can take place until inhibitor becomes dislodged
35
Q

Name the 2 types of competitive inhibitors?

A
  • competitive

- non - competitive

36
Q

How does increasing the enzyme concentration increase the rate of reaction?

A
  • the more enzymes present the more active sites available and thus more likely a successful collision will occur
  • forming an ESC
  • thus, increasing the rate of reaction
37
Q

What is meant by denature?

A
  • change in conditions will cause bonds to break in the structure of the enzyme, changing its shape
  • thus, can no longer function
38
Q

Explain the graph for how temperature affects the rate of reaction

A
  • as the temp increases, the rate of reaction increases

- at certain point, the temp causes the enzyme to denature

39
Q

Explain the graph for how pH affects the rate of reaction

A
  • each enzyme works at an optimum pH

- any pH either side of this will reduce the rate of reaction before denaturing the enzyme completely

40
Q

Cyanide is a non-competitive inhibitor that interferes with Cytochrome C Oxidase in mitochondria of cells I’m final stages of cellular respiration.
Explain how exposure to cyanide is lethal

A
  • cyanide binds to separate allosteric site on cytochrome C oxidase enzyme
  • causes permanent changes to shape of active site
  • enzyme can no longer function
  • cells cannot respire, no energy synthesised
41
Q

What are Inactive precursor enzymes?

A

Some enzymes are synthesised in an inactive precursor form and need to be activated E.G.another enzyme removes part of enzyme

42
Q

What is temperature coefficient (Q 10)?

A

Effect of 10°C rise in temperature on the rate of reaction

43
Q

How would calculated reaction differ from inial reaction?

A
  • initial likely to be greater
  • bc higher conc. of substrate molecules at start
  • more chance of entering AS
44
Q

Explain competitive inhibition?

A
  • similar shape to substate
  • complemenatry to active site
  • prevents substrate binding to site temporarily
45
Q

How could you tell from a graph that it is competitive inhibiton?

A

-at high substrate conc. rate approaches Vmax in absence of inhibitor

46
Q

Why enzyme activity low at pH 4?

A
  • H bonds disrupted
  • ionic bonds disrupted
  • tertairy structure altered
  • substrate no longer complementary to active site
  • enzyme denatured
47
Q

Biological catalyst?

A

Speed up metabolic reactions

48
Q

Problems with samples of liquidised celery as a source of catalase and how to minimise problem?

A
  • diff samples have diff conc. of catalase

- source the extract for whole experiment from a single source

49
Q

What type of enzymes will be the ones that digest food in the small intestine?

A

Extracellular

50
Q

Why proteins required in large amounts but vitamins and minerals are not?

A

-proteins are not stored in body but vitamins are minerals are

Biology (26 decks)

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