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Applied Science > Unit 3 - Practicals > Flashcards

Unit 3 - Practicals Flashcards

1
Q

What is an enzyme?

A

It is a protein molecule that acts as a catalyst in a biochemical reaction.

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2
Q

What are proteins made of?

A

Proteins are made of amino acids.

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3
Q

What is the structure of an amino acid molecule?

A

In an amino acid, there is a central alpha carbon with four chemical groups attached to it:

  • a hydrogen atom
  • an amino group
  • a carboxyl group
  • a variable R group (side chain).
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4
Q

How many R groups and amino acids are there?

A

There are 20 different R groups and so there are 20 different amino acids.

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5
Q

Draw the structure of an amino acid molecule.

A

See revision guide pg 59 for diagram.

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6
Q

How do amino acids join together?

A
  • A condensation reaction (water is produced) occurs between two amino acids.
  • H2O molecule removed via condensation.
  • A branch forms between the two amino acids linked by a peptide bond.
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7
Q

Draw the condensation reaction between two amino acids.

A

See revision guide pg 59 for diagram.

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8
Q

What is a dipeptide?

A

It is formed by two amino acids linked by a peptide bond.

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9
Q

What do amino acids form when joined together?

A
  • Lots of amino acids joined together form long-chain molecules i.e. polymers.
  • 3 amino acids form a tripeptide.
  • Many amino acids join to form a polypeptide.
  • A polypeptide with more than 50 amino acids is called a protein.
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10
Q

What is the active site?

A

It is the part of the enzyme where the biochemical reaction takes place. The active site has a specific shape that only the substrate will fit.

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11
Q

What are the lock and key mechanisms of enzyme action?

A
  • The substrate enters the active site of the enzyme.
  • The substrate binds to the active site of the enzyme.
  • Only specific substrates will bind to a particular enzyme’s active site.
  • After the reaction, the substrate is broken down into products and is released.
  • The active site is then available to catalyse further reactions.
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12
Q

What happens when an enzyme catalyses a reaction?

A

When an enzyme catalyses a reaction, the reaction takes place on the active site of the enzyme.

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13
Q

What is the active site made of?

A

The active site consists of a small number of amino acids which form a specific shape because of the protein’s secondary and tertiary structure.

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14
Q

What is the role of the enzyme?

A

Enzymes work specifically to catalyse one type of biochemical reaction e.g. the enzyme, amylase only breaks down starch.

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15
Q

What can cause an enzyme to denature?

A
  • If the temperature is too high, e.g. above 40°C, the hydrogen bonds will break.
  • This means the enzyme changes its shape.
  • So the active site loses its shape.
  • The enzyme is denatured and can no longer act as a catalyst.
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16
Q

What is the secondary structure of enzymes?

A
  • Secondary structure:
  • The secondary structure is made of polypeptide chains which are arranged into alpha-helix or beta-pleated sheets.
  • Secondary structures are held together by hydrogen bonds (weak bonds) between the -NH of one peptide link and -C=O of another amino acid.
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17
Q

What is the tertiary structure of enzymes?

A
  • Tertiary structure:
  • The secondary structure folds into three-dimensional shapes to make the tertiary structure.
  • The tertiary structure is held together by other types of bonds e.g. ionic bonds.
  • It is the tertiary structure that gives the enzyme the shape of the active site.
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18
Q

Enzymes:

A

Biological catalysts

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19
Q

What is a catalyst?

A

It is a substance that speeds up a reaction and is left unchanged at the end of the reaction.

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20
Q

What is the collision theory?

A
  • The collision theory states that for a reaction to occur:
  • particles must collide.
  • particles must have enough energy to react.
  • The energy of the collision depends on the speed of the particle and the angle they collide.
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21
Q

What is activation energy?

A

It is the minimum energy needed for particles to react.

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22
Q

What happens when the enzyme lowers the activation energy needed?

A
  • This causes:
  • more particles to have the required energy to react.
  • there are more successful collisions.
  • there is a faster reaction.
23
Q

What is the catalytic activity?

A

It is the increase in the rate of a reaction caused by the inclusion of an enzyme.

24
Q

What is a substrate?

A

It is the molecule that is affected by the action of the enzyme.

25
Q

What is the active site?

A

The active site is the area of an enzyme where a substrate binds.

26
Q

What is denatured?

A

It is when the tertiary structure of the enzyme is changed.

27
Q

How to measure the rate of reaction?

A
  • Enzyme reactions can be measured by:
  • measuring decrease in substrate.
  • measuring increase in product.
  • It is easier to measure the increase in product as the starting measurement for the product is 0.
28
Q

Why is it important to record the initial rate of an enzyme-catalysed reaction?

A

It is important to record the initial rate of reaction because the rate will decrease as the substrate is used up and its concentration decreases.

29
Q

Enzymes:

A

Factors affecting activity

30
Q

What are the factors affecting the activity of enzymes?

A
  • Temperature
  • pH
  • Substrate concentration
  • Enzyme concentration
31
Q

What happens if certain factors are not present during an enzyme-catalysed reaction?

A

If these factors are not present then the reaction may slow down or not work at all.

32
Q

How does temperature affect the rate of reaction of enzymes?

A

As the temperature increases up to the optimum temperature, the rate of reaction also increases.

33
Q

What is the optimum temperature?

A

It is the temperature at which an enzyme works the fastest.

34
Q

What happens when the enzyme is below the optimum temperature?

A
  • Particles have less energy.
  • There are fewer collisions.
  • There is a slower reaction.
35
Q

What happens when the enzyme is above the optimum temperature?

A
  • Hydrogen bonds in enzyme break.
  • Enzyme and active site lose their shape so the enzyme can no longer do its job.
  • It has been denatured.
36
Q

Draw a graph showing the effect of temperature on enzyme-catalysed reaction.

A

See revision guide pg 62 for graph.

37
Q

What is the optimum temperature for enzymes in humans?

A

For enzymes in humans, the optimum temperature is 40°C.

38
Q

What is the optimum pH for enzymes?

A
  • It is between 7 and 8 as this is the pH of most body cells and blood.
  • However, some enzymes have a more extreme optimum pH e.g. pepsin, a stomach enzyme that has an optimum pH of 1.
39
Q

How does pH affect the rate of reaction of enzymes?

A
  • pH affects the charge on the active site.
  • If pH changes then the charges on the active site change and the substrate may no longer bind to it.
  • The shape of the active site is very sensitive to pH.
40
Q

Draw a graph showing the effect of pH on enzyme-catalysed reactions.

A

See revision guide pg 62 for graph.

41
Q

How does substrate concentration affect the rate of reaction of enzymes?

A

If there is an increase in substrate concentration, then there is an increase in the rate of collisions which increases the rate of reaction.

42
Q

How does enzyme concentration affect the rate of reaction of enzymes?

A

If there is an increase in enzyme concentration, then there is an increase in the rate of collisions which increases the rate of reaction.

43
Q

What happens if the substrate concentration is too high?

A
  • If the substrate concentration is too high then there will be no more active sites for them to bind to.
  • At this point, increasing the substrate concentration will no longer affect the rate of reaction.
44
Q

What happens if the enzyme concentration is too high?

A

If the enzyme concentration is too high, there are too many free available active sites compared to substrate molecules so the rate of reaction will no longer increase.

45
Q

Draw a graph showing the effect of substrate concentration on enzyme-catalysed reaction.

A

See unit 3 enzymes 3 video on youtube for graph.

46
Q

Draw a graph showing the effect of enzyme concentration on enzyme-catalysed reaction.

A

See unit 3 enzymes 3 video on youtube for graph.

47
Q

Practical 2:

A

Diffusion of molecules

48
Q

What is diffusion?

A

Diffusion is the movement of a substance from an area of high concentration to an area of low concentration.

49
Q

Where can diffusion occur?

A
  • Diffusion can happen in liquids and gases because their particles are moving randomly from place to place.
  • It can also occur across a membrane as long as the molecules are small enough to pass through the membrane then the diffusion will occur.
50
Q

What is dynamic equilibrium?

A

There will be the same number of molecules in areas of low concentration and high concentration so they are evenly spread. This is described as dynamic equilibrium.

51
Q

What are the factors affecting rate of diffusion?

A
  • Size of molecules = Larger molecules move slowly than smaller ones so the rate of diffusion decreases.
  • Temperature = At higher temperature, the energy of molecules increases, so they move faster, increasing the rate of diffusion.
  • Distance through a substance = The greater the distance that the molecules have to travel through a substance, the slower the rate of diffusion.
  • Surface area = As surface area increases, the area of which molecules can spread is increased so the rate of diffusion increases.
  • Shape of the surface of the molecule = The shape of the surface of the molecule that is diffusing can affect the rate of diffusion e.g. shape of a cell can affect its surface area which affects the rate of diffusion of molecules in or out of cell.
52
Q

What is the kinetic theory?

A

It explains the properties of different states of matter.

53
Q

What are the properties of solids?

A
  • Fixed shape.
  • Particles are arranged close together with a regular pattern so they cannot flow.
  • The particles vibrate in a fixed position.
  • It cannot be compressed or squashed.
54
Q

What are the properties of liquids?

A
  • It takes the shape of a container.
  • Particles are arranged close together in a random motion so they can flow and move randomly.
  • Particles can move around each other.
  • Cannot be compressed or squashed.

Applied Science (2 decks)

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