4: Biological molecules

Question 1

Use of water (3 processes)

Answer 1

Solvent in which reactions occur:
e.g. transport,
excretion
digestion - to provide medium for enzymes

Question 2

DNA structure

how do the bases pair up?

Answer 2

DNA - deoxyribonucleic acid

two strands coiled together to form a double helix
– each strand contains chemicals called bases
– cross-links between the strands are formed by pairs of bases
– the bases always pair up in the same way:
A (adenine) & T (thymine)
C (cytosine) & G (guanine)

Question 3

Carbohydrates are made up of…
bigger molecules are made from smaller molecules
examples

Answer 3

(sugar molecules) carbon, hydrogen, oxygen
source of energy for respiration

pasta, bread, potato, rice

Question 4

Fats and oils

Answer 4

(lipids that are solid at room temp) carbon, hydrogen, oxygen

Made from FATTY ACIDS & GLYCEROL
insulation, energy, waterproofing, structure, protection around delicate organs

oily fish, meat, cheese, full-fat diary, nuts

Question 5

Proteins

what is it made from
how different sequences of amino acids affect shapes of proteins?
functions

Answer 5

(chain of amino acids) nitrogen, sulfur, carbon, hydrogen, oxygen

Different sequences of amino acids give different shapes to protein molecules

e.g. of functions
active site of enzymes
binding site of antibodies

Question 6

Test for starch

Answer 6

IODINE solution

+ve test = yellow/brown ➝ blue/black

Question 7

Test for vitamin C

Answer 7

DCPIP (dark blue)

+ve test = dark blue ➝ colourless

Question 8

Test for protein

Answer 8

BIURET test

+ve test = blue ➝ purple
-ve test = stays blue

Question 9

Test for glucose (reducing sugars)

The hazard is fixed by?

Answer 9

BENEDICT’S solution

warm in water bath, contains copper sulfate

+ve test = blue ➝ orange/brick red
Cu 2+ ions reduced to Cu2O3

goggles / gloves when testing for presence of reducing sugars

Question 10

Test for fats & oils (lipids)

Answer 10

ETHANOL

+ve test = colourless ➝ cloudy white, emulsion forms
-ve test = stays colourless

Question 11

What does glucose form? (2)

Answer 11

Glucose forms:

1. CELLULOSE - used for structure, cell walls
2. STARCH (in plants) and GLYCOGEN (in animals) - stored in cells, used in respiration to provide energy.