B3b - proteins and mutations

Question 1

Describe proteins(3)

Answer 1

Made of long chains of amino acid joined together

Each protein has its own number and sequence of amino acids
-which results in differently shaped molecules, which have different functions

Question 2

Describe functions of protein(4)

Answer 2

Structural proteins(e.g.collagen) build cells and tissues

Make hormones which carry messages to control a reaction(e.g.insulin)

Carrier proteins(e.g. haemoglobin)

Enzymes

Question 3

Describe enzymes(6)

Answer 3

Biological catalysts

Catalyses chemical reactions occurring in living cells (e.g. photosynthesis, respiration, protein synthesis)

Have a high specificity for their substrate

• substrate molecules fits into the active site of the enzyme like a key into a lock
• substrate molecules have to be the right shape
• each enzyme only works on a particular substrate

Question 4

How does changing temperature and pH, away from the optimum, change the rate of reaction of an enzyme-catalysed reaction(5)

Answer 4

The rate of reaction will decrease if the temperature or pH is changed away from the optimum

At low temperatures molecules move slowly so the enzymes and substrates are less likely to collide

At extremes of pH and high temperature enzymes become denatured

• enzyme function is inhibited(stopped)
• the shape of the active site changes so the substrate cannot fit

Question 5

What is the Q10 value(2)

Answer 5

Shows how much the rate of reaction changes when temperature is increased by 10°C

= rate at higher temp/rate at lower temp

e.g. value of 2 = rate doubled when temp raised by 10°C

Question 6

Describe the effects of gene mutation(3)

Answer 6

Alters, or prevents the production of the protein which is normally made
-changes the base code of DNA, so the order of amino acids in the protein are also changed, resulting in the production of different proteins

Mostly harmful, but can also be beneficial or have no effect

Question 7

What may cause mutations(2)

Answer 7

Spontaneous(natural causes)

Radiation or chemicals makes it occur more often

Question 8

Why are only certain proteins made in different cells(2)

Answer 8

Although every cell in the body has the same genes, this does not mean that all the same proteins are made

Genes which code for certain types of proteins are switched off in different cells, so those proteins are not produced
-e.g. genes which codes for proteins specific to muscle cells are switched off in skin cells

Question 9

How is the function of a cell determined

Answer 9

By the genes that are switched on in that cell