Protiens and Enzymes M2

Question 1

Describe the reaction of two amino acids

Answer 1

1. condensation reaction forms a molecule of H20, bond forms between the amine group of one amino acid and the carboxyl group of another. (2. hydrolysis will then break it down again) 3. peptide bond

Question 2

Describe the ways that the physical properties of water allow organisms to survive over a range of temperatures

Answer 2

1. high specific heat capacity meaning alot of energy is required to change its temp (stable temp and habitat, as animals waste less energy on temp control and biological reactions can occur). 2. high latent heat heat of evaporation, large amount of energy required to change from liquid to gas, acts as a cooling mechanism. 3. Water is less dense as a solid, provides a habitat for animals like polar bears and an insulating layer for fish beneath the water. 4, solvent to transport mediums/dilute toxic subtances.

Question 3

‘Lock and Key’ Model

Answer 3

enzyme and complementary substrate collide and form an E-S complex. The substrate fits into the enzyme the same way a key fits in a lock.

Question 4

Describe the main difference between the Lock and Key Model and the Induced fit model

Answer 4

Induced fit explains why enzymes are so specific and only bind with one particular substrate. As well as the substrate being the right shape, the active site has to change shape in the right way.

Question 5

Intracellular enzymes

Answer 5

works within the cell ie lysozyme and catalase

Question 6

Extracellular enzymes

Answer 6

work outside the cell ie amylase, lipase and protease

Question 7

Describe and explain the effect of increasing temperature on enzymes

Answer 7

1. Initially, increase temp will mean more KINETIC ENERGY and increase the chance if a SUCCESSFUL COLLISION between ane enzyme and its COMPLEMENTARY substrate, and ROR increases
2. Once the temperature passes the OPTIMUM temperature, the enzyme will DENATURE, the bonds will break and its TERTIARY STRUCTURE and ACTIVE SITE will change and the COMPLEMENTARY substrate will not be able to bind and therefore no E-S complex will form. ROR will decrease.

Question 8

Competitive inhibitor

Answer 8

similar shape to substrate molecules, compete with substrate molecule to bind with the active site.

Question 9

A non-competitive inhibitor

Answer 9

bind to enzymes away from the active site, known as the allosteric site. This causes the active site to change shape and substrate molecules can no longer bind

Question 10

(metabolic poison) Arsenic and Cyanide are non-reversible inhibitors that didn’t o enzymes involved in respiration. Why does cyanide kill you?

Answer 10

It binds permanently to an enzyme that catalyses respiration reactions, meaning cells can no longer respire and die.

Question 11

Globular protein

Answer 11

circular + compact. Soluble, hydrophobic R groups pushed to the outside of the protein. weak bonds to break apart in high temps/changes in pH. Messengers and enzymes

Question 12

Fibrous protein

Answer 12

Several rope-like chains. Insoluble. not sensitive, due to strong bonds. Strong covalent bonds. Offer structural support

Question 13

Enzyme precursors

Answer 13

part of a precursor inhibits its use - once this part if removed via chemical reactions the enzyme becomes active.

Question 14

Cofactors

Answer 14

a non-protein substance that must be present for an enzyme to work.

Question 15

Explain the term biological catalyst

Answer 15

proteins used in the metabolic pathway and they lower the activation energy

Question 16

Examples of globular proteins

Answer 16

Haemoglobin, conjugated haem group, iron binds to oxygen and carries oxygen in RBC, 4 polypeptide chains. Insulin, secreted by the pancreas and soluble so can be transported in the blood, 2 polypeptide chains. Amylase, an enzyme that catalyses the breakdown of starch, include Cl- ion.

Question 17

Examples of fibrous proteins

Answer 17

Collagen, 3 polypeptide chains, minerals bind to it to increase rigidity, the connective tissue found in skin and bones. Keratin, 2 polypeptide chains, flexible and hard/tough. In the skin, it stretches and as nails, it is very hard. Elastin has crosslinks between chains, able to stretch and relax ie in arteries. Allows tissue to return to the original shape.