Biological Molecules

Question 1

structure of carbohydrates

Answer 1

• C H O
• starch and glycogen are large complex carbohydrates which are made up of smaller units (eg. glucose or maltose) joined together in a long chain.

Question 2

structure of proteins

Answer 2

• made up of long chains of AMINO ACIDS

- C H O N

Question 3

structure of LIPIDS

Answer 3

• made up of FATTY ACIDS and GLYCEROL

- C H O

Question 4

test for GLUCOSE

Answer 4

• BENEDICT’S SOLUTION (blue)
• HEAT
• glucose ✅= brick red

Question 5

test for STARCH

Answer 5

• IODINE SOLUTION (brown)

- starch ✅= blue-black

Question 6

test for PROTEINS

Answer 6

• BIURET’S SOLUTION (blue)

- proteins✅= purple

Question 7

test for LIPIDS

Answer 7

• SUDAN III stain solution (clear)
• add 3 drops to a food sample in a test tube and shake.
• lipids✅= mixture separates into 2 layers and top layer BRIGHT RED

Question 8

what are enzymes?

Answer 8

BIOLOGICAL CATALYSTS in metabolic reactions

Question 9

how are enzymes very specific?

Answer 9

• every enzyme molecule has an ACTIVE SITE (part where a substrate joins onto the enzyme)
• each enzyme only catalyses one reaction. for an enzyme to work, a substrate has to be the CORRECT SHAPE to fit into the active site in order to react.
• ‘lock and key’ model

Question 10

how does TEMPERATURE affect enzyme function?

Answer 10

• higher temperature increases the rate at first. the enzyme and substrate have more energy so they move about more and are more likely to collide and form enzyme-substrate complexes.
• if it gets too hot, some of the bonds holding the enzyme together break. this changes the shape of the enzymes active site so the substrate won’t fit anymore. the enzyme is DENATURED.
• all enzymes have an optimum temperature

Question 11

how does pH affect enzyme function?

Answer 11

• if pH is too high or too low, it interferes with the bonds holding the enzyme together.
• this changes the shape of the active site and denatures the enzyme.
• optimum pH is usually 7.