Biological Molecules

Question 1

Name 9 properties of water

Answer 1

High specific heat capacity
High latent heat of evaporation 
Ice is less dense that water 
Good solvent 
Adhesion 
Cohesion 
Surface tension 
Transparent 
High density as a liquid

Question 2

How is the cohesion property of helpful for a plant?

Answer 2

Cohesion is the attraction of similar molecules

This helps pull water molecules up xylem vessels

Question 3

How is the adhesion property of water helpful for a plant?

Answer 3

Adhesion is the hydrogen bonding of unlike molecules

Helps water to adhere to xylem vessel walls

Question 4

What bonds join monosaccharides?

Answer 4

Glycosidic bonds

Question 5

What monosaccharides make…

Maltose
Sucrose
Lactose

Answer 5

Maltose = 2x Glucose

Sucrose = Glucose + Fructose

Lactose = Glucose + Galactose

Question 6

What’s a feature of starch making it a good storage molecule?

Answer 6

It’s insoluble so plant cell won’t swell

Question 7

What are the features of Amylose?

▪▪▪

Answer 7

Unbranched chain of a-glucose

Compacts easily so good for storage

Only 1,4 glycosidic bonds

Question 8

What are the features of Amylopectin?

▪▪▪

Answer 8

Branched chain with 1,4 + 1,6 glycosidic bonds

Branches allow enzymes to break down glycosidic bonds easily

Glucose released quickly

Question 9

What is the bonding in lipids/fats?

Answer 9

Ester bonds

Question 10

Tryglyceride features when used to store energy

▪▪

Answer 10

Lipids contain twice as much energy per gram than carbohydrates (long hydrocarbon chain has lots of energy

Insoluble so water won’t enter via osmosis so cell won’t swell / won’t dissolve in water

Question 11

Role of cholesterol

Answer 11

Makes membrane less fluid and more rigid

Binds to hydrophobic tails of phospholipid and causes it to pack together more closely

Question 12

What’s the bond between proteins?

Answer 12

Peptide bonds

Question 13

Define primary structure

Answer 13

The sequence and order of amino acids in the chain

Question 14

What are the 2 secondary structures?
▪▪
What are the bond present?

Answer 14

A- helix + B-pleated sheets

Hydrogen bonds

Question 15

Define tertiary structure

What binds are present?

Answer 15

3D shape of the protein from further twisting and coiling

Hydrogen bonding
Ionic bonding
Disulfide bridges

Question 16

Define quaternary structure

Answer 16

Multiple polypeptide chains held together by peptide bonds

Question 17

Name a globular protein

What are 4 features of it

Answer 17

Haemoglobin

Quarternary structure

Hydrophilic regions on outside, water soluble

4 polypeptide subunits

Each subunit has one haem- group with Fe 2+ ion – this is a prosthetic group

Question 18

Name a fibrous protein

4 features of it

Answer 18

Collagen

3 polypeptide chains

Quaternary structure

Insoluble

No prosthetic group

Question 19

Similarities of collagen and haemoglobin?

▪▪▪▪

Answer 19

Peptide bonds

Amino acid chain

Helix

Quaternary level Protein

Hydrogen, ionic bonds and disulphide bridges

Subunits

Question 20

Test for proteins?

Positive result observation

Answer 20

Biuret test

Solution turns purple (from blue)

Question 21

Test for starch

Positive result observation

Answer 21

Iodine test

Solution turns blue-black (from brown-orange)

Question 22

Test for lipids

Positive result observation

Answer 22

Emulsion test

Solution turns milky (from colourless)

Question 23

Test for reducing sugar

How it’s done

Positive result observation

Answer 23

Benedict’s test

Add Benedict’s solution and heat

Green, yellow, orange, brick red (from blue)

Question 24

Test for non reducing sugars

How is it done?

Positive result observation

Answer 24

Benedict’s test

Add dilute HCl and heat
Add sodium hydrogen carbonate
Heat sample with Benedict’s reagent

Solution green, yellow, orange, brick red (from blue)