C1.1 Enzymes

Question 1

Define catalyst

Answer 1

A catalyst is a substance that speeds up a reaction without being used up or altered

Question 2

state the role of enzymes in the chemical reactions on which life is based

Answer 2

Enzymes speed up chemical reactions that would normally be too slow to happen without them

Question 3

State that enzymes speed up chemical reactions _____, so can be _____

Answer 3

enzymes speed up chemical reactions without being altered, so can be reused

Question 4

define metabolism

Answer 4

• Metabolism is the complex network of interdependent and interacting chemical reactions occurring in living organisms
• Most of these reactions are enzyme controlled
• These reactions can often have multiple steps and be quite complex

Question 5

define specificity (in relation to enzyme structure and function)

Answer 5

Each enzyme will only catalyze one specific reaction or one type of reaction due to the structure and properties of its active site

Question 6

Outline how control of metabolism is regulated by enzymes

Answer 6

By making more or less of an enzyme, cells are able to control the rate of reaction

There are also mechanisms that temporarily stop enzymes when they aren’t needed

Question 7

Contrast anabolic and catabolic reactions

Answer 7

Anabolic reactions build up molecules and require energy

Catabolic reactions break down molecules and release energy

(cats break stuff! ants build stuff!)

Question 8

List three examples of anabolic processes

Answer 8

• Synthesis of complex carbohydrates
• DNA synthesis
• Protein synthesis

Question 9

List three examples of catabolic processes

Answer 9

• Digestion of complex carbon compounds
• Digestion of food
• Cell respiration

Question 10

Outline properties of globular proteins

Answer 10

Globular proteins have very specific confirmations and structures

globular proteins will have tertiary and quaternary structure

• enzymes are globular proteins
  (ex. enzymes have a specifically shaped active site – allowing them to bind with only certain substrates)

Question 11

Explain the relationship between enzyme structure and enzyme specificity, including the structure and function of the active site

Answer 11

• Enzymes = large molecules, but only the active site is involved in catalysis
• Substrates = the reacting molecules
• Substrates and enzymes move and randomly collide
• Many molecules can enter the active site, but if they are not the right shape or alignment, no reaction will happen.
• If the shape and alignment are correct: the substrate will BIND to the active site, forming an enzyme-substrate complex
• Enzymes have specificity (they can catalyse only one type of reaction because an enzyme can only react with a specific substrate molecule)

Question 12

Outline the stages of enzyme catalysis of a chemical reaction

Answer 12

-The substrate gets closer to the enzyme by random collisions

-The chemical properties of the active site attracts the subsrate

-The substrate binds to the active site

-The active site and substrate change shape to fit perfectly

-If a second substrate is present, it binds to another part of the active site

-The enzyme makes it easier for the substrate to make or break bonds, forming products

-The products detach

Question 13

Describe the induced fit model of enzyme binding

Answer 13

The enzyme and substrates alter their bond lengths and angles to fit together perfectly

Question 14

Explain the role of random collisions in the binding of the substrate with the enzyme active site

Answer 14

The substrate will get closer to an enzyme by random molecular motion and collisions before it is attracted by the active site

Question 15

Compare enzyme substrate movement involved in reactions that occur in the cytoplasm, with large substrates and with immobilized enzymes

Answer 15

The substrate moves to the enzyme since it tends to be smaller, or if the enzyme is immobilized. If the substrate is large, the enzyme moves to the substrate.

Question 16

Discuss variation in the specificity of different enzymes

Answer 16

The specificity of an enzyme depends on the shape of the enzyme formed by the relatively weak bonds between amino acids.

Some enzymes are very specific, only accepting one substrate, while some accept a group of substrate, like hexoses.

Question 17

Define denaturation

Answer 17

Denaturation is when a protein loses its structure when its intermolecular bonds are broken due to extreme heat or pH

Question 18

Outline the causes and effects of denaturation on enzyme structure and function

Answer 18

CAUSES:

Temperature: Extremely high temperature causes the particles to vibrate, increasing the chance of the intermolecular bonds breaking.

pH: Extreme pH alters ionic bonds between molecules

EFFECT:
The enzyme loses its shape and specificity.

Question 19

Explain the effects of:
- temperature
- pH
- substrate concentration

on enzyme structure and function with reference to collision theory, temporary, and permanent denaturation

Answer 19

Temperature: Increasing temperature increases rate of reaction (by increasing chances of collision) until the point of denaturation

pH: Optimum pH gives the highest rate of reaction

Substrate Concentration: Increases the rate of reaction until a maximum point where the rate will become constant

Question 20

Draw + interpret graph of pH on enzyme activity

Answer 20

A change to pH from the optimum affects enzymes and their activity.

Extreme pH values can denature an enzyme by altering the three-dimensional structure of its active site.

The shape of the enzyme, along with its active site, will change.

If pH is lower or higher than the optimal, the rate of reaction gradually decreases.

Question 21

Draw + interpret graph of temperature on enzyme activity

Answer 21

As the temperature increases, so does the rate of reaction, since there is more kinetic energy

There are more successful collisions and more ESC forms, so rate of reaction increases, up to the optimum temperature

As the temperature continues to rise, the rate of reaction falls rapidly

Increasing temperature causes the enzyme molecule to vibrate. At high temperatures there is too much vibration and the hydrogen bonds within the enzyme break. + The active site changes shape. ESC can no longer form and the enzyme is denatured

Question 22

Draw + interpret graph of substrate concentration on enzyme activity

Answer 22

Question 23

Identify the manipulated, responding and controlled variables in experiments of enzyme catalyzed reactions

Answer 23

Independent: Temp, pH, Sb. Concentration
Dependent: Enzyme activity
Control: Light intensity, volume, etc.

Question 24

State the unit for enzyme reaction rate

Answer 24

Amount of chemical divided by time

Question 25

State two methods for determining the rate of enzyme reaction rates

Answer 25

1. Add a certain amount of chemical and measure the time it takes for all of the reactants to turn into products

2.Let the reaction happen for a fixed amount of time and measure the amount of product formed or remaining substrate

Question 26

measuring the activity of catalase and hydrogen peroxide

one investigative technique for measuring the activity of an enzyme

Answer 26

Catalase and hydrogen peroxide:

MEASURE the volume of oxygen generated in a set time

Question 27

measuring the activity of a amylase and starch

one investigative technique for measuring the activity of an enzyme

Answer 27

Amylase and starch:

Starch forms a blue-black colour with this solution, SO measure the time taken for starch to be broken down

Question 28

How do you conduct enzyme-controlled experiments?

Answer 28

• Choose an enzyme
• Determine the substrate
• Decide what you are measuring (rate of product production or rate at which reactant is used up)
• Choose your independent variable (what you will change)
• Identify your control variables

Question 29

How do you calculate the rate of reaction?

Answer 29

Question 30

Define activation energy

Answer 30

Activation energy is the minimum amount of energy required to start a chemical reaction

Question 31

activation energy is used to?

Answer 31

Activation energy is used to break or weaken bonds in the substrate so the reaction can occur

Question 32

how do enzymes lower the activation energy of a reaction?

Answer 32

Enzymes lower activation energy by

• forming an enzyme-substrate complex
• providing an alternative reaction pathway with a lower energy requirement

Question 33

interpret graphs showing the effect of lowering the activation energy by enzymes

Answer 33

Question 34

In anabolic reactions, the enzyme ___?

Answer 34

holds the substrates close to one another, reducing repulsion and allowing them to bond more easily

Question 35

In catabolic reactions, fitting the substrate into the active site puts ____?

Answer 35

strain on the bonds, making them easier to break

Question 36

Compare the location of synthesis of enzymes used within and outside of a cell

Answer 36

Enzymes are synthesized in different locations depending on whether they are used inside or outside of a cell

Inside the cell:

• Enzymes are generally synthesized in the cell cytoplasm on ribosomes

(Some enzymes are also located within organelles like lysosomes and mitochondria)

Outside the cell:

• enzymes are synthesized in the rough endoplasmic reticulum (RER) of the exocrine pancreas

Question 37

State an example of an intracellular metabolic reaction and an extracellular
metabolic reaction

Answer 37

intracellular:

• glycolysis
• Krebs cycle

extracellular:

• chemical digestion

Question 38

intracellular?

Answer 38

within cells
(ex. catalase)

Question 39

extracellular?

Answer 39

outside cells
(ex. trypsin and amalyse)