Module 2: Biological molecules

Question 1

Importance of water having a high latent heat of vaporisation

Answer 1

Large amount of energy required to change from liquid to gas. Therefore when water evaporates it can help cool living things and keep temperature stable.

Question 2

Importance of water having a high specific heat capacity

Answer 2

Large amount if energy required to change temperature therefore:
Thermally Stable environment for aquatic organisms
Aquatic organisms use less energy on temperature control
Living things have a stable temperature for enzyme controlled reactions

Question 3

Structure of glycogen

Answer 3

a-glucose molecules joined by 1,4 and 1,6 glycosidic bonds
Large side branches
Compact

Question 4

Importance of ice being less dense than water

Answer 4

Aquatic organisms have stable environment to live in during water
Provides insulation for ponds against extreme cold

Question 5

Starch: Structure related to function

Answer 5

Compact so doesn’t occupy a large amount of space
Insoluble so has no osmotic effect
Can be hydrolysed quickly

Question 6

Cellulose: Structure related to function

Answer 6

Microfibrils and macro-fibrils have high tensile strength
Macro-fibrils criss-cross for extra strength
Insoluble

Question 7

Structure and Function of Insulin

Answer 7

Structure:
2 polypeptide chains- A chain begins with a-helix B chain ends with b-pleated sheet
R group on the outside of molecule - makes it soluble in water
Function:
Binds to glycoprotein receptors on muscle and fat cells to increase uptake of glucose

Question 8

Tertiary Structure

Answer 8

a-helices and b-pleated sheets along with areas of straight chains of amino acids fold further to form a 3D structure

Held together by:
hydrogen bonds 
ionic bonds
Disulfide bridges
Hydrophobic and hydrophilic interactions

Question 9

Importance of water having cohesion and surface tension

Answer 9

Collums of water in plant vascular tissue are pulled up the xylem tissue together from the roots.
Insects like pond-skaters can walk on water

Question 10

Test for non-reducing sugars

Answer 10

Boil a sample with hydrochloric acid to hydrolyse sucrose into glucose and fructose
Cool solution and neutralise with sodium hydrogen carbonate
Test for reducing sugars again
Green,yellow orange and red indicate presence of sugar

Question 11

Structure of Haemoglobin

Answer 11

Made of 4 polypeptides- 2 a-chains and 2 b-chains
1 haem group per polypeptide- 4 haem groups per molecule
Haem is prosthetic group which contains iron (Fe2+)

Question 12

Primary structure

Answer 12

Sequence of amino acids in a protein chain

Question 13

General structure of an amino acid

Answer 13

One central carbon atom bonded to:
Hydrogen atom
carboxyl group
amino group
R group

Question 14

Test for lipids

Answer 14

Mix sample with ethanol
Filter it and pour solution into water
Cloudy white emulsion indicates presence of lipids

Question 15

Importance of water being a solvent

Answer 15

Medium for metabolic reactions
Molecules and ions can be transported around living things
Able to dilute toxic substances

Question 16

Function and properties of collagen

Answer 16

Provides mechanical strength:

• Artery walls prevent it from bursting
• Tendons made from collagen connects muscle to bone
• cartilage and connective tissue made from collagen

Question 17

Structure of Amylopectin

Answer 17

a-glucose molecules joined by 1,4 glycosidic and 1,6 glycosidic bonds
Branched and coiled
Compact

Question 18

Iodine test for starch

Answer 18

Add iodine solution to sample

If starch is present colour will change form yellow brown to blue-black

Question 19

Function of phospholipid

Answer 19

Help form plasma membranes of cells

Form a bilayer with fatty acid stains facing into each other and polar heads facing outwards

Question 20

Structure of a Triglyceride molecule

Answer 20

1 glycerol
3 fatty acids
bonded by ester bonds

Question 21

Function of Haemoglobin

Answer 21

Carry oxygen from lungs to tissues

Question 22

Structure and function of pepsin

Answer 22

Structure:
- Single polypeptide chain of 327 amino acids folded into a symmetrical tertiary structure
-Held together by hydrogen bonds and 2 disulphide bridges
Function:
Digests protein in stomach

Question 23

Structure of a phospholipid molecule

Answer 23

1 glycerol
2 fatty acids
a phosphate group
Bonded by ester bonds

Question 24

Quaternary structure

Answer 24

Interaction between two or more polypeptides

Question 25

Secondary structure

Answer 25

Chain of amino acids
Some coil into a-helices some fold into b-pleated sheets
Both held together by hydrogen bonds
Bonds form between amino group and carboxyl group

Question 26

Properties and function of elastin

Answer 26

Cross-linking and coiling make it strong and extensible
Skin can stretch around bones and muscles
allows lungs to inflate and deflate
helps bladder expand to hold urine

Question 27

Structure of cellulose

Answer 27

long, unbranched aims of b-glucose
Joined by 1,4 glycosidic bonds
every other b-glucose molecule in chain is rotated 180º to stop spiralling
Many cellulose chains form microfibrils which form macro-fibrils

Question 28

Structure of Amylose

Answer 28

unbranched chain of a-glucose molecules joined by 1,4 glycosidic bonds
coiled
very compact

Question 29

Formation of hydrogen bonds between two water molecules and how water forms these bonds

Answer 29

Bond between O and H of adjacent molecules
Bond between electropositive Hydrogen and electronegative oxygen.
Water forms these bonds because it is polar

Question 30

Test for reducing sugar

Answer 30

Add Benedict’s reagent to sample and heat in a water bath at 80ºC for 3 mins
Orange-red precipitate indicates reducing sugar is present

Question 31

Function of cholesterol

Answer 31

Sits in the middle of hydrophobic part of bilayer to regulate fluidity of membrane so its not too fluid or stiff

Question 32

Test for proteins

Answer 32

Add Biuret reagent

Colour changes from blue to lilac

Question 33

Properties and function of keratin

Answer 33

Rich in cysteine so lots of disulphide bridges
waterproof
Found in:
Finger nails
Hair 
Claws
Fur