Proteins + Enzyme

Question 1

1. what is an Amino Acid

Answer 1

MONOMERS of a POLYPEPTIDE (protein)

Question 2

1. What Is a DIPEPTIDE?

Answer 2

The CONDENSTATION REACTION of 2 Amino Acids

Question 3

1. What is a FUNCTIONAL PROTEIN

Answer 3

1 or more POLYPEPTIDE

Question 4

1. What are the 4 types of Protein Structure

Answer 4

Primary, Secondary, Tertiary, and Quaternary structure.

Question 5

1. What is THE PRIMARY structure of Proteins

Answer 5

sequence of amino structure

Question 6

1. What is THE SECONDARY structure of Proteins

Answer 6

Amino acid sequence, or a primary structure folds into structures called alpha helices or beta-pleated sheets

Question 7

1. What holds alpha helices or beta-pleated sheets?

Answer 7

H Bonds hold them together for stability

Question 8

1. What is THE TERTIARY structure of Proteins and what do they do for enzymes?

Answer 8

Alpha helices or beta-pleated sheet FOLD further to form a specific, 3D structure. These are the bases for enzyme specificity, which allow certain chemical reactions to be catalyzed in the body

Question 9

1. What provides stability to the Protein?

Answer 9

Ionic bonds and disulphide bridges hold structure

Question 10

1. What is THE QUATERNARY structure of Proteins

Answer 10

MORE than 1 POLYPEPTIDE CHAIN bind to a prosthetic/non-protein group (metal ion) e.g. hemoglobin

Question 11

1. Biuret test for proteins

Answer 11

1. Add a few drops of Na0H (base) to solution - alkaline
2. Add a few drops of aqueous Copper Sulfate to test solution
3. Observe color change of test solution
   blue = -
   purple precipitate = +

Question 12

2. What are Enzymes ?

Answer 12

They are globular Proteins -> biological catalytic. Catalyse reactions lower activation energy to speed up the chemical ROR. Active site is specific to the shape to its substrate = complimentary.

Question 13

What is the Induced Fit Model ?

Answer 13

• SUBSTRATE INDIUCE A COMFORMATIONAL CHANGE IN THE ACTIVE SITE/ITS TERTIARY STRUCTURE. This allows the SUBSTRATE to BIND to an ACTIVE SITE to form an ENZYME-SUBSTRATE CONPLEX
• Theory states enzyme + substrate complex are almost complimentary but when the substrate enters Active site, interactions between substrate and AMINO ACIDS cause SHAPE of the AS TO CHANGE and become COMPLIMENTARY TO THE SUBSTRATE.

Question 14

What is Enzyme Specificity

Answer 14

tertiary structure of the AS, its extremely specific. Only complementary substrates to bind to AS to form an enzyme - substrate complexes

Question 15

How is an enzyme reaction effected by Temperature?

Answer 15

IT GOES UP (A) - as the temp increases = more KE, therefore more successful collisions between E-S complexes. THE PEAK AS IT REACHES OPTIMUM TEMP (B), here E-S complexes formed. THEN GOES DOWN (C) Enzymes denature, The H & ionic bonds break this changes the tertiary structure of the AS, so it is no longer complimentary.

Question 16

How is an enzyme reaction effected by PH?

Answer 16

(its drawn like TEMP but up and straight down and equal) Either side of optimum PH (Enzymes are sensitive to the change in PH). The Enzymes DENATURE because, the H & ionic bonds break this changes the tertiary structure of the AS, so the substrate and AS are no longer complimentary. (Fewer E-S COMPLEXES FORMED).

Question 17

How is an enzyme reaction effected by Concentration of Substrate ?

Answer 17

IT GOES CONSTANTLY UP (A). Here the increase in sub conc. = the higher the ROR and successful collisions. The substrate conc. is limiting. THEN IT PLAUES (B) Substrate conc. is no longer l8imiting as the ROR doesn’t increase. Enzyme conc. maybe limiting as all AS maybe in use.

Question 18

What does Chromatography do?

Answer 18

It superstrates molecules e.g. Amino acids according to their solubility in a solvent

Question 19

The more soluble the chemical is ….

Answer 19

The higher up the paper it travels

Question 20

Method of chromatography

Answer 20

1. Add drop of solution to origin line, allow to dry & repeat to concentrate the sample
2. Calc the RF value of Amino acid = distance travelled by the component / the distance travelled by the solvent

Question 21

2 - way chromatography

Answer 21

New Solvent front, Diff solvent, New origin line

Question 22

What does lower affinity mean?

Answer 22

The sample has travelled up the paper more

Question 23

What does higher solubility mean?

Answer 23

travels up paper faster and will end up closer to the top of the solvent front = higher RF value

Question 24

What does Competitive inhibition mean for E-S complexes?

Answer 24

Fewer will be formed = block access from the substrate

Question 25

What is Competitive Inhibition ?

Answer 25

Are structurally analogous to the normal substrate that the enzymes bind to, decreasing its activity as they compete with substrate for the enzyme. The amount of product formed remains the same, however the rate at which product formation occurs decreases. The higher the concentration of competitive inhibitor the lower the reaction rate. Increasing the substrate reverses the effect of competitive inhibitors by outcompeting them.

Question 26

Non-competitive Inhibitors?

Answer 26

Do not bind to the active site; it binds at another site on the enzyme - the allosteric site. Binding of the non-competitive inhibitors changes the shape of the active site therefore preventing the binding of the substrate. Increasing the concentration of substrate has no effect on non-competitive inhibition.

Question 27

What is an inhibitor?

Answer 27

An inhibitor is a substance which slows down or stops a reaction by affecting the binding of substrate to the enzymes. Inhibitors can either be reversible and irreversible.

Question 28

Suggest how Binding of Cytochrome oxidase affects the enzyme

Answer 28

Inhibition (compet and non). Changes the tertiary structure of Enzyme and Blocks AS of enzyme = no E-S complexes formed

Question 29

Suggest how antidote can reduce poisoning by cyanide

Answer 29

Antidote binds to cyanide so cyanide cannot bind to enzyme

Question 30

Suggest one advantage of trapping the enzyme within gel beads

Answer 30

• the enzyme can be reused

Question 31

when flow rate of milk increases, concentration of glucose decreases. explain why. [1]

Answer 31

• too fast for lactose molecules to bind to active site of the lactase enzyme
• enzyme substrate complexes can’t form

Question 32

Galactose has a similar structure to part of the lactose molecule. Explain how galactose inhibits lactase. [2]

Answer 32

• Galactose is a competitive inhibtitor;
  binds to active site instead of lactase
• reducing enzyme substrate complexes formed between lactose and lactase enzyme
• fewer available lactase molecules