Proteins And Enzymes

Question 1

What is the function of haemoglobin

Answer 1

Allows oxygen to bind and be transported around the organism

Question 2

What is the function of an antibody

Answer 2

Binds to specific antigen, used in all immune responses against pathogen

Question 3

Function of enzyme

Answer 3

Reduces activation energy within a metabolic reaction

Question 4

Function of actin and myosin

Answer 4

Structural proteins involved in muscle contraction

Question 5

Function of keratin

Answer 5

Structural proteins found in nails, talons etc

Question 6

Function of collagen

Answer 6

Structural proteins found in tendons

Question 7

What are proteins made of

Answer 7

Monomers of amino acids

Question 8

Draw the structure of an amino acid

Answer 8

H. H O
I. I. II
H-N-C-C-OH
I
R

Question 9

Describe the function of an enzyme and how it becomes denatured with temperature and pH

Answer 9

Specific shape of the protein is essential to its function
Proteins only denature at high temperatures and changes to Ph
Increasing temperature increases the kinetic energy of the molecules making them vibrate , this breaks the weak hydrogen bonds in the secondary and tertiary structure
Changing PH breaks ionic bonds
Desaturation is permanent

Question 10

Examples of globular proteins

Answer 10

Transport proteins such as haemoglobin
Enzymes such as amylase
Hormones such as insulin

Question 11

Structural proteins example

Answer 11

Keratin- hair
Collagen- connective tissue
Elastin- connective tissue

Question 12

Define globular protein

Answer 12

Spherical shape and are soluble in water, they are highly unstable and undergo denaturation catalysed by slight changes in

Question 13

Describe the structure of proteins

Answer 13

Polymer of amino acids
Joined by peptide bonds
Formed by condensation reaction
Primary structure is order and sequence of amino acids
Secondary structure is the folding of polypeptide chain due to weak hydrogen bonds forming alpha helixes and beta pleated sheets
Tertiary structure is 3D folding of polypeptide chain held by ionic and hydrogen bonds and disulphide bridges.
Quaternary structure is two or more polypeptide chains joined together

Question 14

When a pathogen causes an infection, plasma cells secrete antibodies that destroy pathogen

Answer 14

Antigens are specific shape/tertiary structure
Antibody is complementary to antigen so binds to form antibody-antigen complex
Variable regions on antibodies are specific shape
Antigens bind

Question 15

Biuret test

Answer 15

Changes to from blue to purple if protein is present

Question 16

Define activation energy and describe how enzymes lower this

Answer 16

The minimum energy required for a successful chemical reaction
They lower activation energy by stressing and distorting the bonds in the substrate during the formation of an enzyme substrate complex

Question 17

Stages of the lock and key model

Answer 17

The active site is rigid and doesn’t change shape
The substrate binds to the enzymes active site
The substrate fits exactly as they are complementary
Products are formed and no longer fit the active site so are released
The enzyme is free to partake in another reaction

Question 18

Describe the induced fit model

Answer 18

Active site not complementary
Active site changes shape to form ESC
Stressing and distorting bonds

Question 19

Suggest why a protein can be the substrate for 2 different enzymes

Answer 19

Different parts of the protein have different amino acid sequences so are a different shape
Each enzyme active site is a specific shape and complementary to a different part of the protein

Question 20

Define the term rate

Answer 20

Change in Y per unit time

Question 21

Define optimum temperature

Answer 21

The maximum energy that can be supplied to the molecules before hydrogen and ionic bonds start to break

Question 22

Effects of temperature on enzymes

Answer 22

Increase in kinetic energy, more likely to successfully collide and react- rate of reaction increases as more substrate complexes are being formed.
Beyond optimum, kinetic energy is too great which causes the hydrogen bonds and ionic bonds between R groups to break, causing a change in the specific tertiary structure
No longer complementary so can’t bind to form ESC- enzyme becomes denatured

Question 23

What exactly is pH and what happens to bonds when it changes

Answer 23

A measure of hydrogen ion concentration
If changed the charge on the R groups of amino acids are altered and ionic and hydrogen bonds are broken, altering tertiary structure

Question 24

What scale is pH recorded in and why

Answer 24

Log- the concentration of H+ ions is too large

Question 25

Explain a substrate concentration graph

Answer 25

As the substrate concentration increases, the rate of reaction increases and then plateaus
When substrate concentration is low there is a low rate of reaction due to fewer collisions and therefore fewer enzyme-substrate complexes formed per second. The substrate becomes the limiting factor. Plateaus as all binding sites are saturated so the enzyme concentration is now the limiting factor

Question 26

What is the effect of increasing substrate conc on the rate of an enzyme controlled reaction

Answer 26

Increases then plateaus as all active sites are saturated

Question 27

Competitive inhibitors

Answer 27

Have similar shape to substrate
Bind to the active site and prevent the substrate from binding temporarily
Fewer ESC form per second
Reduce the rate of reaction so fewer products are formed per second
Can be overcome by increasing substrate concentration

Question 28

Non-competitive inhibitors

Answer 28

Bind to the allosteric site, causing an alteration to the tertiary structure and active site so substrate is no longer complementary and bind
Fewer ESC formed
Decreased rate of reaction
Can’t be overcome

Question 29

An enzyme controlled reaction is inhibited by substance X
Suggest a simple way in which you could tell whether substance X is acting as a competitive or non-competitive inhibitor

Answer 29

Calculate the rate of reaction- if it plateaus at a low rate it is a non-competitive inhibitor, if increases to maximum- competitive