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A Level Biology - 3.1 Biological Molecules > enzymes > Flashcards

enzymes Flashcards

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1
Q

what is an enzyme?

A

a protein molecule that acts as a biological catalyst and speeds up reactions

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2
Q

what type of protein is an enzyme

A

globular protein

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3
Q

how does an enzyme speed up reactions?

A

when a substrate fits into active site of an enzyme, it forms an enzyme-substrate complex (which is what lowers activation energy)

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4
Q

why does an enzyme speeding up reactions happen?

A
  • if 2 substrate molecules need to join, being attached to the enzyme holds them closer together, reducing any repulsion between molecules so they join easier
  • if enzyme is catalysing a breakdown, fitting into the active site puts a strain on the bonds so the substrate molecules break up more easily
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5
Q

why does an enzyme catalyse one specific reaction?

A
  • the active site of any enzyme has a specific tertiary structure and is only complementary to the substrate
  • only the substrate can bind to the active site
  • to form an enzyme-substrate complex
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6
Q

what is the lock and key model?

A

substrate fits perfectly into the active site

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7
Q

what is the induced fit model?

A

active site conforms to its substrates shape

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8
Q

how does the induced fit model work?

A
  • the substrate binds to the active site of the enzyme
  • the active site of the enzyme then changes shape slightly to be completely complementary to the substrate as it binds
  • this distorts/breaks/forms bonds as it causes bond strain in the substrate
  • this decreases activation energy
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9
Q

What is a key property of enzymes regarding their specificity?

A

Enzymes are very specific and usually catalyze only one reaction.

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10
Q

Why do enzymes only catalyze one reaction?

A

Because only one substrate will fit into the active site, which is determined by the enzyme’s tertiary structure.

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11
Q

What determines the active site of an enzyme?


A

The active site is determined by the enzyme’s tertiary structure.

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12
Q

What happens if the tertiary structure of an enzyme is altered?


A

The shape of the active site will change, affecting enzyme function.

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13
Q

What factors can alter the tertiary structure of an enzyme?


A

Factors such as pH and temperature can alter the tertiary structure.

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14
Q

How is the primary structure of an enzyme determined?

A

The primary structure is determined by the gene encoding the enzyme.

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15
Q

What could be the consequence of a mutation in the gene encoding an enzyme?


A

A mutation could change the tertiary structure of the enzyme produced.

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16
Q

What are the main properties of enzymes?


A
  • Very specific: usually catalyze only one reaction
  • Active site shape determined by tertiary structure
  • Alteration of tertiary structure affects function
  • Primary structure determined by genes
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17
Q

What is the optimal temperature range for human enzymes?

A

0-37 degrees Celsius

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18
Q

How does an increase in temperature affect enzyme activity up to 37 degrees Celsius?

A

The rate of reaction increases due to higher kinetic energy of molecules

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19
Q

Why do substrate molecules collide more frequently with enzyme active sites as temperature increases?

A

Because higher temperature increases the kinetic energy of the molecules

20
Q

What happens to the energy of collisions between enzyme and substrate as temperature increases?


A

The energy of the collisions increases, leading to more successful collisions

21
Q

What occurs to the rate of reaction when the temperature exceeds 37 degrees Celsius?

A

The rate of reaction decreases

22
Q

What happens to the kinetic energy of atoms in the enzyme as temperature increases beyond 37 degrees Celsius?


A

The kinetic energy continues to increase, causing more vigorous vibrations

23
Q

How does increased kinetic energy affect the hydrogen bonds in an enzyme’s tertiary structure?

A

It breaks the hydrogen bonds, altering the enzyme’s shape

24
Q

What is the consequence of the active site changing shape due to increased temperature?


A

The active site is no longer complementary to the substrate

25
Q

What is the term used to describe an enzyme that has lost its functional shape?


A

Denatured

26
Q

What are the factors affecting enzyme activity?


A

Temperature
pH levels
Substrate concentration
Enzyme concentration

27
Q

What is the optimal pH for most humans?


A

pH 7 (neutral)

28
Q

What is an exception to the optimal pH of 7 for humans?


A

Pepsin works best at pH 2 (acidic)

29
Q

How does the rate of reaction change as pH increases from 6 to 8?


A

The rate of reaction increases from 0 to 100

30
Q

What happens to the rate of reaction as pH increases from 8 to 10?


A

The rate of reaction decreases from 100 to 0

31
Q

What occurs when pH deviates from the optimum level?


A
  • Difference in concentration of H+ ions
  • Breaks ionic/hydrogen bonds
  • Changes tertiary structure of the enzyme
  • Active site changes shape
  • Substrate no longer complementary to active site
  • Decrease in enzyme-substrate complexes
  • Decrease in rate of reaction
32
Q

What happens to the rate of reaction as substrate concentration increases to ‘x’ e.g. 2 mol dm^-3?


A

The rate of reaction increases

33
Q

What occurs to the rate of reaction when substrate concentration increases beyond a certain point?


A

The rate of reaction remains constant

34
Q

Why does the rate of reaction increase with substrate concentration initially?


A

More substrate molecules lead to more chances of successful collisions with the active site

35
Q

What happens to the enzyme-substrate complexes as substrate concentration continues to increase?


A

All active sites become occupied

36
Q

What becomes limiting when substrate concentration continues to increase and all active sites are occupied?


A

Enzyme concentration becomes limiting

37
Q

What is the relationship between substrate concentration and the formation of enzyme-substrate complexes?


A
  • As substrate concentration increases, more substrate molecules are available.
  • This leads to a higher chance of successful collisions with the active site.
  • More enzyme-substrate complexes are formed until all active sites are occupied.
38
Q

Describe the phases of reaction rate in relation to substrate concentration.


A
  1. Rate increases as substrate concentration rises to a certain point (e.g., 2 mol dm^-3).
  2. Rate remains constant when all active sites are occupied.
  3. Enzyme concentration becomes limiting, leading to a plateau in the reaction rate.
39
Q

What happens to the rate of reaction as enzyme concentration increases?


A

The rate of reaction increases

40
Q

Why does the rate of reaction increase with enzyme concentration?

A

More available active sites lead to more successful collisions and enzyme-substrate complexes

41
Q

What happens when substrate amount is limited and enzyme concentration increases?

A

An increase in enzyme concentration eventually has no further effect

42
Q

what is an inhibitor

A

a molecule that binds somewhere on the enzyme and therefore prevents enzyme from functioning

43
Q

competitive inhibitor

A

same shape as substrate and can bind to the active site (complementary) which creates an enzyme-inhibitor complex which prevents substrate from being able to bind and therefore no enzyme-substrate complexes are formed so reaction won’t occur and is much slower

44
Q

what would a high conc. of substrate do to a competitive inhibitor?

A

flood out inhibitor out of active site therefore substrate can collide successfully producing an enzyme-substrate complex and rate of reaction goes back to normal

45
Q

non competitive inhibitor

A

binds to enzyme away from active site (any location that isn’t the active site - the allosteric site)which changes the shape of the tertiary structure and the substrate is no longer complementary to the active site therefore - no enzyme-substrate complexes so decreases rate of reaction

46
Q

what would a high conc. of substrate do to a non-competitive inhibitor?

A

non-competitive inhibitors don’t compete with the substrate molecules because they completely change shape of the active site so increasing substrate concentration won’t make a difference

A Level Biology - 3.1 Biological Molecules (9 decks)

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