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Biology AS > Enzymes, 2.4 > Flashcards

Enzymes, 2.4 Flashcards

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1
Q

What are enzymes and what is their role?

A

Biological catalysts. Speed up metabolic reactions

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2
Q

What is the turnover number?

A

The number of reactions an enzyme can catalyse per second

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3
Q

What type of proteins are enzymes?

A

Globular

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4
Q

Why is the structure of an enzyme important?

A

Determines its function

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5
Q

What is substrate?

A

A molecule on which an enzyme acts

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6
Q

What is the active site?

A

Area on an enzyme which is complementary to the substrate molecule.

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7
Q

How can the shape of an active site be altered?

A

Increase in temperature. Change in pH.

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8
Q

What are enzymes inside the cell called?

A

Intracellular

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9
Q

What are enzymes outside the cell called?

A

Extracellular

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10
Q

Describe the function of lactase

A

Breakdown of milk, sugar and lactose intolerance glucose and galactose. Lactose intolerant = don’t produce lactase.

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11
Q

What is the function of catalase?

A

Breakdown of hydrogen peroxide to water and oxygen. Hydrogen peroxide is toxic but is a by product of some reactions

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12
Q

What is a cofactor for?

A

Addition of a non-protein to an enzyme before they can catalyse

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13
Q

What is a prosthetic group?

A

A cofactor for which is permanently bound - covalent bonds. Part of its 3D shape

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14
Q

What is an example of a prosthetic group?

A

Enzyme carbonic anhydrase - catalysed CO2 and H2O to carbonic acid

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15
Q

What are coenzymes?

A

Organic molecules that bind temporarily transferring a chemical group when required. They are chemically changed after and need to be recycled.

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16
Q

Give an example of a coenzyme

A

B3 - needed for respiration and energy to grow

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17
Q

Describe the Lock and Key Hypothesis.

A
  1. Substrate identifies active site of enzyme
  2. Substrate fits into the enzymes active site
  3. Temporary hydrogen bonds hold them together
  4. Substrate is broken into smaller product molecules that leave the active site
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18
Q

Describe the Induced Fit Hypothesis..

A
  1. Shape of the active site is complementary to the shape of the substrate
  2. Enzyme modules itself around the substrate
  3. Intermolecular forces bind
  4. Product will be a different shape and will detach
19
Q

What is an advantage of enzymes?

A

Lower activation energy. When molecules collide they need to collide with sufficient energy to cause a reaction

20
Q

What is the effect of increasing the temperature on enzymes?

A

Molecules gain energy and move faster, increases the chance of collisions and the energy with which molecules collide. Rate of reaction increases.

21
Q

What is the optimum temperature?

A

When the rate of reaction is at its maximum. After this the enzyme denatures.

22
Q

Why does an increase in temperature denature an enzyme?

A

Breaks the weak bonds in the enzyme which hold the tertiary structure together. Active site changes shape. Change is irreversible.

23
Q

What is meant by the temperature coefficient Q10?

A

Increase in the rate of a process when the temperature rises by 10degrees

24
Q

What is Q10?

A

Rate of reaction at (T+10) / rate of reaction (T)

25
Q

What does the pH show?

A

Whether a substance is acid, alkali or neutral.

26
Q

What is a buffer?

A

Resists changes in pH

27
Q

Why will a change in the pH affect n enzyme?

A
  1. Hydrogen ions causes changes in pH
  2. Excess hydrogen ions will interfere with hydrogen bonds and change the shape
  3. Less substrate will be able to bind - rate of reaction slowed.
28
Q

What is the optimum pH?

A

pH at which the rate is at its maximum - after this the enzyme is disrupted

29
Q

Describe the effect of substrate concentration?

A
  1. As substrate concentration increases so does the rate of reaction
  2. Can binds to active sites, more complexes formed, more product formed
30
Q

What has happened when the rate of reaction has reached its maximum rate concerning substrate concentration?

A

All the active sites will be occupied so more substrate will not be able to successfully collide.

31
Q

What is the effect of enzyme concentration?

A
  1. As enzyme concentration increases so does the rate
  2. More active sites available, more successful collisions, more product formed
  3. At a point there will be no further increase as there will be no more substrate.
32
Q

Why is the initial rate of reaction the fastest?

A

At the start there is the most substrate - higher chance of collisions

33
Q

Define inhibitor

A

Substance that slows down the rate of a reaction by affecting the enzyme

34
Q

What are the two types of inhibitor?

A

Competitive and non-competitive.

35
Q

Describe how competitive inhibitors work?

A
  1. Have a similar shape to enzyme substrate

2. They compete directly with substrate to form an enzyme-inhibitor complex

36
Q

What does the amount of inhibition depends on in competitive inhibitors?

A

The concentrations of inhibitor and substrate.

37
Q

How do non-competitive inhibitors work?

A
  1. Binds to the allosteric site and disrupts the tertiary structure
  2. Active site is no longer complementary to the substrate
  3. Substrate can no longer bind
38
Q

How does the amount on inhibitor effect the rate of reaction in non-competitive inhibition?

A

More inhibitor the greater the degree of inhibition

39
Q

Why does enzyme activity need to be controlled?

A

Can be dangerous eg multiple sclerosis.

40
Q

How do we regulate metabolic pathways?

A

With enzyme inhibition

41
Q

How does enzyme inhibition regulate metabolic pathways?

A
  1. End product acts as a regulator - end product inhibition
  2. High amount of product
  3. Will bind non-competitively to an enzyme in the pathway
  4. When amount of product decreases inhibition ends
42
Q

What is an example of an inhibitor?

A

Toxins/Venoms - block enzymes. Cyanide - inhibits aerobic respiration. Snake venom - inhibits AChE, causes paralysis.

43
Q

What can we use to stop anti freeze? And why?

A

Alcohol. Reduces the rate of reaction which breaks down anti freeze. Competitive inhibitor.

Biology AS (12 decks)

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