Paper 1: Topic 2 Organisation - Digestive system & enzymes (LV) Flashcards Preview

Mrs P's GCSE Biology > Paper 1: Topic 2 Organisation - Digestive system & enzymes (LV) > Flashcards

Flashcards in Paper 1: Topic 2 Organisation - Digestive system & enzymes (LV) Deck (63)
Loading flashcards...
1

Define the terms

a) enzyme

 

b) active site

Enzyme: A biological catalyst that speeds up the rate of a chemical reaction without being altered or used up itself in the reaction

 

 

Active site: a small dent on the surface of the enzyme where the substrate binds to form and ESC and where the chemical reaction takes place.

2

State what type of molecule enzymes are

Proteins

A large molecule made from many amino acids joined together

 

Hint: remember all proteins are made by ribosomes

3

State 4 factors that affect the activity of enzymes

pH

temperature

concentration of enzyme

concentration of substrate

4

Define the term substrate

A chemical that is used in the reaction and is converted to the product

5

Define the term product

The chemical that is made at the end of a chemical reaction

6

State the two different types of chemical reaction

Catabolic

Anabolic

7

Define the terms 

a) catabolic reaction

b) anabolic reaction

a) catabolic:

A chemical reaction that breaks down the substrate(s) into smaller product(s)

 

b) anabolic:

A chemical reaction that builds up smaller substrates into a larger molecule (the product)

8

Define the term metabolism

The sum total of all the chemical reactions that take place inside a cell which includes all the catacbolic and anabolic reactions

9

Describe the structure of an enzyme

An enzyme has a dip on its surface (called the active site)

The active site has a complementary shape to its specific substrate

10

Explain why enzymes are specific

Each enzyme has an active site that is uniq​ue to specific substrates for one chemical reaction

The active site is only complementary to one substrate

Hence each enzyme can only catalyse one specific reaction

11

Describe the relationship between the active site and the substrate

They are complementary to each other

 

Hint: do NOT say they are the same as each other

12

Name the model that describes how enzymes work

Lock and key theory

 

IMPORTANT:

When annotating a diagram remember to add descriptions onto your diagram e.g.

  • the active site is complementary to the substrate
  • the substrate is specific to the enzyme's active site

13

Explain the lock and key theory model

The active site on an enzyme acts as a lock

The complementary substrate acts as a key that fits into the active site (lock)

This forms the enzyme-substrate complex

The chemical reaction then takes place

The substrate is converted to the product

The product is released

The enzyme remains unaltered and can carry out further identical reactions

14

Define the term enzyme-substrate complex

An enzyme that has it specific substrate bound to its active site

15

Explain the effect of low temperatures on enzyme activity

  • At low temperatures both the substrate and enzyme have very little kinetic energy
  • There are very few collisions between the substrate and the active site
  • Very few enzyme-substrate complexes form
  • Hence very little product is made in any given period of time
  • The enzyme is described as inactive
  • The rate of reaction is very low

16

Explain the effect of high temperatures on enzyme activity

  • At high temperatures both the substrate and enzyme have a high amount of kinetic energy
  • There are many collisions between the substrate and the active site
  • However the high temperature changes the shape of the enzyme
  • This alters the shape of the active site
  • The substrate is no longer complementary to the active site
  • NO enzyme-substrate complexes form
  • NO product is made in any given period of time
  • The enzyme is described as denatured
  • The rate of reaction is zero

17

Why is it incorrect to say an enzyme is dead?

All enzymes are just proteins

They are not living and so can’t be killed

They are just specialised chemical molecules

18

Describe the effect the optimum temperatures on  enzyme activity

  • At the optimum temperatures both the substrate and enzyme have very high kinetic energy
  • There are many collisions between the substrate and the active site
  • High numbers of enzyme-substrate complexes form
  • Hence a lot of product is made in any given period of time
  • The enzyme is described as working at its maximum rate
  • The rate of reaction is at its maximum

19

What is the typical optimum temperature for human enzymes?

37oC

20

Describe how an enzyme is denatured and the effect this has

How an enzyme is denatured:

  • At high temperatures the bonds holding the enzyme in its specific shape break
  • This changes the shape of the enzyme including the shape of the active site

The effect of denatureing an enzyme:

  • The active site is no longer complementary to its substrate
  • So no reaction can take place and no product is made

21

Name an human enzyme that works at an optimal pH of 1-2 (acidic)

Pepsin

 

Remember this enzyme is found in the stomach and must be able to work efficiently in acidic conditions due to the hydrochloric acid in the stomach

22

State 2 human enzymes that work at an optimal pH of 7 (neutral)

Amylase

Catalase

Lipase

Carbohydrases

Proteases (except trypsin)

23

How do you calculate the rate of reaction?

Amount of product formed divided by the time

24

In an experiment how can you control the temperature to ensure you are carrying out a fair test?

Use a thermostatically controlled water bath

Hint: don’t just say water bath

25

In an experiment how can you control the pH to ensure you are carrying out a fair test?

Use buffer solutions to keep the pH of the experiment constant

 

Buffers work by keeping the pH constant

26

State the 3 main groups of enzymes that are involved in digestion

Lipases

Carbohydrases

Proteases

27

Describe the action of a protease enzyme

Proteases break proteins down into amino acids

28

Describe the action of a lipase enzyme

Lipases break lipids down into 3 fatty acids and 1 glycerol

 

Hint: remember to state the number of each type of product made

29

Describe the action of a carbohydrase enzyme

Carbohydrases break complex carbohydrase down into simpler sugars e.g. glucose

30

Give an example of a carbohydrase.

State its substrate and product

Carbohydrase = amylase

Substrate = starch

Product = maltose

Decks in Mrs P's GCSE Biology Class (26):