BM: Enzyme Action Flashcards

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1
Q

What are enzymes?

A

Globular proteins that speed up chemical reactions by acting as biological catalysts.

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2
Q

What are catalysts?

A

Molecules that alter the rate of reaction without undergoing permanent changes themselves.

Can be reused repeatedly and are useful in small amounts.

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3
Q

What do enzymes catalyse?

At what levels do they do this?

A

Catalyse metabolic reactions - both at a cellular level (eg. respiration) and for the organism as a whole (eg. digestion in mammals).

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4
Q

What can enzymes affect?

A

Structures in an organism (eg. production of collagen) and functions (like respiration).

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5
Q

Enzyme action can be what?

A

Intracellular - within cells.

Extracellular - outside cells.

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6
Q

What type of molecule is an enzyme?

A

A globular protein.

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7
Q

What is the active site of an enzyme?

A

The part of the enzyme where the substrate molecules bind to.

It has a specific shape.

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8
Q

What is activation energy?

A

The initial amount of energy required to start a chemical reaction.

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9
Q

For a reaction to take place, what conditions must be satisfied?

A
  • Molecules must collide with sufficient energy to alter the arrangement of their atoms.
  • Free energy of products must be less than that of substrates.
  • Activation energy must be overcame.
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10
Q

What is free energy?

A

The energy of a system that is available to perform work.

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11
Q

What is activation energy often provided as?

A

Heat

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12
Q

How do enzymes speed up the rate of reaction?

A

By lowering the activation energy of the reaction it catalyses.

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13
Q

What forms when a substrate fits into the active site of an enzyme?

A

An enzyme-substrate complex

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14
Q

What actually lowers the activation energy of the reaction?

What are the reasons why?

A

The formation of the enzyme-substrate complex.

  • If the two substrate molecules are joining, attaching to an enzyme holds them closer together, reducing repulsion making them bond more easily - less energy is required to do this.
  • If catalysing a breakdown reaction, fitting into an active site puts more strain on bonds in substrate, so they break up more easily - less energy is required to do this.
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15
Q

What was the early model of enzyme activity?

A

The lock and key model.

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16
Q

What is the active site made up of?

What does it form?

A

Made of a relatively small number of amino acids, forming a small depression within the much larger enzyme molecule.

17
Q

How is the substrate molecule held within the active site?

A

By bonds that temporarily form between certain amino acids of the active site and groups on the substrate molecule.

18
Q

What does the induced fit model propose?

A

The active site forms as the substrate and enzyme interact.

19
Q

Explain the induced fit model:

A
  • Proximity of the substrate (change in the environment) leads to a change in the enzyme that forms the functional active site - enzyme is flexible and can mould around substrate.
  • As it changes shape, the enzyme puts strain on substrate molecule, distorting bonds within it and consequently lowering the activation energy of the reaction.
20
Q

Draw a diagram illustrating the induced fit model:

A
21
Q

What are the properties of an enzyme determined by?

A

The tertiary structure - which is determined by the primary structure.

22
Q

What does pH equal?

A

Log10 [H+]

23
Q

If the tertiary structure of an enzyme is altered, what will happen?

A

The shape of the active site will change, and the substrate won’t fit, an enzyme-substrate complex won’t be formed and the enzyme will no loger be able to carry out its function.

24
Q

Why are enzymes highly specific?

A

Only one substrate will fit the active site, because:

  • Each enzyme has a different tertiary structure and so a different shaped active site.
  • If the substrate doesn’t match the active site, an enzyme-substrate complex won’t be formed and the reaction won’t be catalysed.
25
Q

What is the primary structure of proteins determined by?

What would the consequence of a mutation in this be on the tertiary structure?

A

Determined by a gene.

If a mutation occurs in that gene, it could change the tertiary structure of the enzyme produced.