-1A: proteins

Question 1

what are proteins monomers?

Answer 1

amino acids

Question 2

draw the structure of an amino acid, labelling the groups

Question 3

what are the 5 parts to an amino acid?

Answer 3

-amino/amine group
-variable group
-central carbon
-hydrogen
-carboxyl group

Question 4

how is a dipeptide formed?

Answer 4

-via condensation reactions between the OH of the carboxyl + H of the amino group
-release a molecule of water
-forming a peptide bond
-making a dipeptide

Question 5

name the 4 structural stages of a protein

Answer 5

-primary
-secondary
-tertiary
-quaternary

Question 6

how do each of these stages develop from one another?

Answer 6

each of the stages are ‘processed’ to move onto the next

Question 7

primary stage?

Answer 7

the order of amino acids in a polypeptide chain

Question 8

secondary stage?

Answer 8

-sequence of amino acids causes parts of protein molecule to bend into a helix/fold into beta pleated sheets
-held together by hydrogen bonds (forming between OH of carboxyl group and H of amine group)

Question 9

tertiary stage?

Answer 9

-further folding of secondary structure
-into unique 3D shape
-held together by ionic/hydrogen/disulphide bonds/bridges between R groups of different amino acids

Question 10

quaternary stage?

Answer 10

-protein that is made up of more than one polypeptide chain
-eg haemoglobin (4 chains)

Question 11

what happens when an enzyme denatures?

Answer 11

-bonds that hold secondary + tertiary structures in place break -> unique 3D structure is lost -> enzyme no longer has specific unique active site

Question 12

what conditions causes enzymes to denature, why?

Answer 12

-too high temperatures (too much kinetic energy)
-conditions too acidic/alkali (pH too low/high) (too many H+/OH- ions)

Question 13

what is the significance of the sequencing of amino acids in the primary structure?

Answer 13

-if even one amino acid is different
-hydrogen/ionic/disulphide bonds form in a different location -> different 3D shape -> active site will have a different shape + will be non functioning

Question 14

what about carrier proteins?

Answer 14

-different shaped binding site
-molecules are no longer complementary + can no longer be transported across membranes

Question 15

state and describe test for presence of proteins

Answer 15

-add biuret reagent
-positive result: colour change from blue -> purple

Question 16

give 3 functions of proteins

Answer 16

-enzymes
-antibodies
-transport proteins

Question 17

describe how you would test for presence of protein in a sample

Answer 17

-biuret test
-add a few drops of sodium hydroxide solution -> to make solution alkaline
-add copper II sulfate solution
-positive -> stay purple, negative -> stay blue

Question 18

describe how a dipeptide is formed

Answer 18

-condensation reactions between 2 amino acids
-forming a peptide bond
-between OH of carboxyl group + amine/o group
-releasing a molecule of water

Question 19

describe the induced fit model of enzyme action

Question 20

explain how a change in amino acid sequence of an enzyme may prevent it from functioning properly

Question 21

describe competitive + non-competitive inhibition:

Answer 21

-competitive: molecules have similar shape to substrate molecules, compete with substrate molecules to bind to active site of enzyme, stopping substrate molecule from binding
-non-competitive: molecules bind to enzymes away from active site -> allosteric site, slightly changing shape of tertiary structure -> changing shape of active site so complementary substrate no longer fits