biological molecules (proteins)

Question 1

what is the primary structure of a protein?

Answer 1

the sequence of amino acids

Question 2

what is the secondary structure of a protein?

Answer 2

hydrogen bonds
coils to form an alpha helix
or folds to form a beta pleated sheet

Question 3

what is the tertiary structure of a protein?

Answer 3

hydrogen and ionic bonds, disulphide bridges, 3D structure

Question 4

what is the quarternary structure of a protein?

Answer 4

when several polypeptides join together

Question 5

what are amino acids composed of?

Answer 5

carboxyl group (COOH), amine group (NH2), R group

Question 6

how many amino acids are there?

Answer 6

20

Question 7

what causes the differences between amino acids?

Answer 7

their R group

Question 8

what bonds are present in proteins?

Answer 8

peptide bonds

Question 9

what are examples of protein functions?

Answer 9

enzymes, antibodies, transport proteins, structural proteins

Question 10

how do you carry out the Biuret test for proteins?

Answer 10

add a few drops of sodium hydroxide solution
add some copper II sulfate solution
if protein present the solution turns purple
if no protein present stays blue

Question 11

what is the job of an enzyme?

Answer 11

speeds up the rate of reaction by acting as a biological catalyst

Question 12

what type of molecule is an enzyme?

Answer 12

protein

Question 13

why is the shape of an enzyme specific?

Answer 13

due to its tertiary structure

Question 14

how does an enzyme speed up the rate of reaction?

Answer 14

lowers the activation energy needed to start a reaction
eg) by reducing repulsion between substrates so they can bond more easily, when an enzyme enters the active site, puts a strain on bonds in substrate so it can be broken up more easily

Question 15

what is the lock and key model?

Answer 15

suggests that the substrate fits into the enzyme in the same way that a key fits into a lock

Question 16

what model was the lock and key replaced with?

Answer 16

induced fit

Question 17

what happens in the induced fit model?

Answer 17

as the substrate binds, the active site slightly changes shape

Question 18

how does temperature influence enzyme activity?

Answer 18

an increase in temperature means that the enzyme’s molecules have more kinetic energy (move faster, more collisions) which increases the rate of reaction
if the temperature goes above a certain level, the vibration breaks bond that hold together the active site, active site changes shape so substrate no longer fits= denatured

Question 19

how does pH affect enzyme activity?

Answer 19

enzymes have an optimum pH value
significantly above or below this the enzyme is denatured
H+ and OH- ions found in acids and alkalis can disrupt the ionic/hydrogen bonds that hold the enzyme’s tertiary structure in place
=change in active site= denatured

Question 20

how does enzyme concentration affect the rate of reaction?

Answer 20

more enzyme molecules available= more likely a substrate is to collide and form an enzyme-substrate complex
increasing enzyme concentration increases rate of reaction
if amount of substrate is limited- adding more enzyme molecules will have no further effect

Question 21

how does substrate concentration affect the rate of reaction?

Answer 21

higher the substrate concentration, the faster the reaction
more substrate molecules means a collision is more likely so more active sites are used
only up to saturation point
substrate concentration will decrease with time so rate highest at the start of the reaction

Question 22

what is a competitive inhibitor?

Answer 22

molecule that has a similar shape to a substrate molecule

Question 23

how do competitive inhibitors work?

Answer 23

compete with the substrate molecules to bind to the active site, blocking the active site so that a substrate molecule cannot fit in

Question 24

how is rate of reaction affected by competitive inhibition?

Answer 24

inhibitor takes up active sites, so hardly any substrate gets to the enzyme, decreases the rate of reaction
increasing the substrate concentration will help to increase the rate of reaction

Question 25

what is a non competitive inhibitor?

Answer 25

molecule that binds to the enzyme away from its active site

Question 26

how does a non competitive inhibitor work?

Answer 26

causes the active site to change shape, so the substrate molecules can no longer bind to it

Question 27

how does a non competitive inhibitor affect rate of reaction?

Answer 27

increasing substrate concentration doesn’t make a difference, non competitive inhibitor will always decrease the rate of reaction