Biochemicals

Question 1

Chemical elements in carbohydrates

Answer 1

Carbon, oxygen, hydrogen

Question 2

Chemical elements in proteins

Answer 2

Carbon, oxygen, hydrogen, nitrogen

Question 3

Chemical elements in lipids

Answer 3

Carbon, oxygen, hydrogen

Question 4

Structure of carbohydrates

Answer 4

Composed of individual units called monosaccharides or simple sugars

Question 5

Structure of proteins

Answer 5

A sequence of amino acids linked together to form a polypeptide chain

Question 6

Structure of lipids

Answer 6

A glycerol backbone, 2 fatty acid tails and a phosphate group

Question 7

Test for glucose

Answer 7

Reagent: benedicts solution
Colour change : blue + heat —> orange

Question 8

Test for starch

Answer 8

Reagent: iodine
Colour change: orange —> blue/black

Question 9

Test for proteins

Answer 9

Reagent: Biuret
Colour change: blue —> lilac

Question 10

Test for lipids

Answer 10

Reagent: ethanol/water
Colour change: clear - cloudy

Question 11

Role of enzymes as biological catalysts in metabolic reactions

Answer 11

Speed up rate of biological reactions in the body without getting used up or altered in the process

Question 12

How can temperatures affect enzyme function

Answer 12

Higher than optimum - enzyme becomes denatured as bonds that hold the enzyme together will break and the active sight will change shape not allowing for the substrate to fit in the active sight anymore.

Lower temps - slows down the rate of the enzymes function because the molecules move more slowly as there is less kinetic energy

Question 13

Practical to test how enzyme activity can be affected by changes in temperature

Answer 13

• add 5cm3 of starch solution to a test tube and heat to a set temp using a beaker of water with a Bunsen burner
• add a drop of iodine to each of the wells in a spotting tile
  Use a syringe to add 2cm3 of amylase to the starch solution and mix well
  Every minute add a droplet of the solution to a new well of iodine
  Repeat process until iodine solution stops turning blue-black
  Record time taken for reaction to be complete
  Repeat for a range of temperatures from 20 degrees to 60 degrees

Question 14

How is enzyme function affected by change in PH

Answer 14

• enzyme optimum PH is 7
• when the PH is moved too far away from the optimum then the bonds between the amino acids are broken and the enzyme changes shape and becomes denatured
• the substrate cannot fit anymore

Question 15

Practical for the enzyme activity change for different PHs

Answer 15

• add a drop of iodine to each well in a spotting tile
• use a syringe to put 2cm3 of amylase into a test tube
• add 1cm3 of PH3 buffer solution to the test tube using a syringe
• use another test tube to add 2cm3 of starch solution to the amylase and buffer solution, start the stopwatch whilst mixing
• Every 10s put a droplet of the solution into a new well on the spotting tile
• repeat process until the iodine doesn’t turn blue/black
  Record time taken for completion of reaction
  Repeat for PH values ranging from 3-11