Protein and enzyme 12.2

Question 1

structure of amino acid

Answer 1

Each amino acid contains a central(alpha )
carbon atom which a nitrogen containing group (H2N) and a carboxyl group (COOH) are attached

Question 2

R groups are….and can be…

Answer 2

Variable groups

• R-groups can be:Positively charged +Negatively charged -Hydrophilic (attracted to water)Hydrophobic (repelled by water)

Question 3

The bond between amino acids is…

Answer 3

formed by a condensation reaction (forming a peptide bond)

Question 4

What groups are on each end of the chain?

Answer 4

A peptide chain will always have an amine group at one end and a carboxyl group in the other end.

Question 5

The number of peptide bonds in a chain will be…

Answer 5

one less than the total number of amino acids originally joined together (dipeptide is 2 amino acids so 1 peptide bond)

Question 6

Primary structure is…

Answer 6

the number and sequence of amino acids in a polypeptide chain.

Question 7

Secondary structure is…

Answer 7

The way the polypeptide chain folds OR coils into:

ALPHA HELIXES AND/OR BETA PLEATED SHEETS

these are held together by weak hydrogen bonds ONLY

Question 8

Tertiary structure is…

Answer 8

Further folding the polypeptide chain the specific complex 3D shape

The R-groups determine how the polypeptide chain folds into the specific 3D shape. The 3D shape is help together by bonds between the R groups of amino acids

Question 9

3 types of bonds in tertiary structure is…

Answer 9

WEAK HYDROGEN BONDS - between C=O and NH of adjacent amino acids)

IONINC BONDS - also weak bonds which form between oppositely charged R groups.

DISULPHIDE BRIDGES - strong bonds that form between cysteine amino acids only

Question 10

SPECIFIC tertiary structure + SPECIFIC shape = ??????

Answer 10

SPECIFIC function

Question 11

THE QUATERNARY STRUCTURE IS….

Answer 11

Some proteins consists of 2 or more polypeptide chains joined together

Question 12

Proteins denature…

Answer 12

at HIGH temperature and changes to the pH

Question 13

Increased temperature…

Answer 13

Increases kinetic energy of molecules making them vibrate more which breaks the hydrogen bonds in the secondary and tertiary structure.

Changing pH breaks ionic bonds between R groups in tertiary structure

Question 14

Biuret test

Answer 14

put small volume of sample in a labelled test tube

add equal amount of buret solution

If present it will change to lilac/purple/violet

Question 15

Enzymes are a globular protein that act as…

Answer 15

biological catalysts

Question 16

What is a catalyst?

Answer 16

increase rate of reaction but remain unchanged or unaffected by the reaction
They take part in the reaction but don’t get used up

Question 17

What do enzymes lower?

Answer 17

Activation energy

Question 18

When enzyme-substrate complexes form, what do they do to the bonds?

Answer 18

distort/stress them

Question 19

All proteins have binding sites only enzymes have…

Answer 19

Active sites

Question 20

Enzymes have a specific…

Answer 20

tertiary structure

Question 21

Active sites are made up of…

Answer 21

less than 10 amino acid R groups

Question 22

Explain the lock and key model

Answer 22

Active site is specifically complementary to its substrate like a key and lock

Active site -lock
substrate - Key

Question 23

STAGES OF LOCK AND KEY

Answer 23

1. Active site is rigid and doesn’t change shape
2. Substrate binds to the enzymes active site
3. Substrate fits exactly into the active site (complementary)
4. Produces are formed and no longer fit into active sit so its released
5. Enzyme can take part in another reaction

Question 24

STAGES OF INDUCED FIT MODEL

Answer 24

1. substrate enters active site and binds to it forming enzyme-substrate complex
2. binding of substrate induces the change of shape in the active site
3. “slight” change in shape of the specific 3D tertiary structure of the active site applies stress or distorts the bonds within the substrates molecules with lowers the activation energy of the reaction
4. When the substrate leaves the active site reruns to original shape

Question 25

FACTORS AFFECTING ENZYME ACTION

Answer 25

• Temperature and pH
• Inhibitors
• Substrate concentration

Question 26

how temperature effects enzyme action

Answer 26

Inc temperature = inc kinetic energy which bring more successful collisions so more forming of Enzyme-Substrate complexes.

Optimum temp - maximum energy that can be supplied before hydrogen and ionic bonds start to weaken

OVER OPT TEMP - change in shape of active site so no longer complementary so less ES complexes are formed.