Proteins and Enzymes Unit 1.3

Question 1

What is the general structure of an amino acid?

Answer 1

Amine group NH2
R group (carbon containing side chain
Carboxyl group COOH

Question 2

What does a condensation reaction between two amino acids form

Answer 2

• Dipeptide

- Peptide bond

Question 3

What does the condensation reaction between many amino acids form

Answer 3

Polypeptide Chain

Question 4

What is the structure of a polypeptide?

Answer 4

A chain of amino acids joined in a condensation reaction

Question 5

Primary structure of protein

Answer 5

• Sequence of amino acids in protein

- determines rest of structure

Question 6

Secondary structure of protein

Answer 6

-held together by hydrogen bonds between the carboxyl groups and amine groups of two amino acids
-Most common structures:
Alpha helix
Beta pleated sheet

Question 7

Tertiary structure of protien

Answer 7

Compact globular sturcture form by the folding of the whole polypeptide
Held together by bonds between the R groups
1 weak hydrogen bonds
2 ionic bonds
3 disulphide bonds

Question 8

Quaternary structure of protein

Answer 8

More than one polypeptide chain

Question 9

What is the test for protiens?

Answer 9

• mix blue BIURET solution with sample

- If protien present solution will turn purple/ lilac

Question 10

What is the structure of an enzyme molecule

Answer 10

• Enzymes are globular proteins
• Have a specific 3D shaped active site specific to one substrate
• provide alternative reaction pathway which lowers activation energy
• speeds up rate of reaction

Question 11

What is the lock and key hypothesis?

Answer 11

-The shape of the active site is exactly complimentary to the subject molecule

Question 12

What is the induced fit Hypothesis

Answer 12

• Active sight thought to change slightly to fit to substrate (rather than being rigid shape)
• Enzyme puts strain on substrate molecule
• Lowering activation energy needed to break bonds by putting stress on bonds

Question 13

What is a competitive inhibitor

Answer 13

• Similar shape to real substrate (Complimentary to active sight of enzyme)
• Fit into enzymes active sight and block it but are not permanently bound
• Prevents enzyme substrate complexes forming
• Decreased rate of reaction

Question 14

What is a non-competitive inhibitor?

Answer 14

• Bind to the enzyme anywhere other than active sight
• Alter the shape of active sight so no longer complimentary to substrate
• No enzyme substrate complexes can form
• Rate of reaction decreased

Question 15

What do enzymes form when reacting with a substrate?

Answer 15

-Enzyme substrate complexes

Question 16

What is the effect of temperature on rate of reaction

Answer 16

-as temp increases rate of reaction increases
because particles have more kinetic energy more frequent, successful collisions
-Reaches optimum temperature where rate highest
-After rate decreases rapidly as enzymes denature
-(Hydrogen bonds break changing tertiary structure causing active sight to change shape so no longer complimentary)

Question 17

What is the effect of PH on rate of reaction

Answer 17

• Optimum PH is where rate is highest (the right conc of hydrogen ions)
• When altered from optimum tertiary structure changed causing active sight to change shape and be no longer complimentary to substrate
• Enzymes denatured

Question 18

Effect of substrate concentration on rate of reaction?

Answer 18

• as substrate concentration increases rate increases
• substrate concentration is limiting factor as not enough to fit into all enzyme active sights
• rate then plateaus
• as now not enough active sights for all substrates so enzyme concentration becomes the limiting factor

Question 19

Effect of enzyme concentration on rate of reaction

Answer 19

• As enzyme concentration increases rate of reaction increases
• Here enzyme concentration is limiting factor as not enough enzymes to react with all substrates
• Rate of reaction then plateaus
• As substrate concentration becomes the limiting factor as there is a excess of enzymes with not enough substrate to fill the active site