Biological Molecules

Question 1

Monomers of: Maltose, Sucrose and Lactose.

Answer 1

Maltose: Glucose-Glucose
Sucrose: Glucose-Fructose
Lactose: Glucose-Galactose

Question 2

Test for Non-reducing Sugars.

Answer 2

Add HCl. Heat for few mins. Add sodiumhydrogencarbonate. Add Benedict’s solution. Heat for few mins.
Blue-Green-Orange-Brick red.

Question 3

Test for Reducing sugars.

Answer 3

Add Benedict’s solution. Heat for a few minutes.
Blue-Green-Orange-Brick red.

Question 4

Test for Starch.

Answer 4

Add Iodine.
Amber-Blue/Black

Question 5

Test for Proteins.

Answer 5

Add Biuret A+B.
Blue-Purple/Lilac.

Question 6

Test for Lipids.

Answer 6

Add Ethanol.
Colourless-Milky white

Question 7

Alpha vs Beta glucose - Similarities

Answer 7

Same Molecular Formula.
Both formed into polymers through condensation reactions, which contain glycosidic bonds.

Question 8

Define:

• polar molecule
• hydrogen bond
• glycosidic bond
• metabolism

Answer 8

• molecules with an uneven distribution of charge.
• a bond formed between polar molecules.
• a covalent bond forming between sugar molecules.
• the combination of chemical reactions taking place within a cell.

Question 9

Reducing sugar vs Non-reducing sugar.

Answer 9

Reducing - ‘donate’ electrons to other molecules in chemical reactions.

Non-reducing - don’t ‘donate’ electrons during chemical reactions.

Question 10

What are the properties of starch?

Answer 10

Branched chain - allows the molecule to be easily hydrolysed by many enzymes simultaneously.
Coiled shape - allows the molecule to be easily compacted, so large amounts of it can be stored in small spaces.
Insoluble - won’t affect the cells water potential, and it can’t diffuse out of the cell.
Large - the molecule can’t diffuse out of the cell.

Question 11

What are the properties of cellulose?

Answer 11

Straight, unbranched chain - allows for hydrogen bonds to form, increasing strength of molecule.
Grouped molecules - form microfibrils, which when grouped form fibres, providing more strength to the molecule.

Question 12

What are the properties of glycogen?

Answer 12

Insoluble - it won’t affect the cells water potential, and can’t diffuse out of the cell.
Branched chain - allows the molecule to be easily hydrolysed by many enzymes simultaneously.
Coiled shape - allows the molecule to be compacted easily to store large amounts in small areas.
Large - the molecule can’t diffuse out of the cell.

Question 13

Properties and uses of Triglycerides

Answer 13

Properties:
- contains ester bonds.
- contains carbon, hydrogen and oxygen.
- the fatty acids can be saturated or un-saturated.
- they only contain a hydrophobic region.
- they are formed by condensation reactions.
- they contain three fatty acids and glycerol.
- non-polar molecule, so won’t affect water potential of cell.
Uses:
- large form of energy storage due to high number of C-H bonds.
- used for insulation and protection of organs.
- important source of water due to release of water when oxidised as high H:O ratio.

Question 14

Properties and uses of Phospholipids

Answer 14

Properties:
- contains ester bonds.
- contains carbon, hydrogen, oxygen and phospholipids.
- their fatty acids can be saturated or un-saturated.
- they contain both a hydrophobic and hydrophilic region.
- they are formed by condensation reactions.
- they are polar molecules, which form a bilayer with an aqueous environment.
- they contain glycerol, two fatty acids and a phospholipid group.
Uses:
- help maintain stability and strength of cells.
- act as semi-permeable barrier, helping maintain proper balance of substances within cell.
- aids protection against ‘environmental insults’.
- forms the phospholipid bilayer.

Question 15

Uses of Lipids

Answer 15

• Energy source
• Insulation.
• Protection.
• Waterproofing.

Question 16

Proteins:

• What they are made of;
• Definition of ; primary, secondary, tertiary and quaternary structures

Answer 16

• made of a carboxyl group, an amine group, a hydrogen and carbon, and an R group.
• contain peptide bonds
• primary; specific sequence of chain of amino acids
• secondary; hydrogen bonding of peptide backbone causes amino acids to fold into repeating patterns (alpha helix/beta pleats)
• tertiary; 3-D folding pattern of secondary structure (polypeptide chains) due to side chain interactions (di-sulphide bridges, ionic bonds, hydrogen bonds, hydrophobic interactions)
• quaternary; multiple polypeptide chains held together

Question 17

Fibrous proteins; structure and function

Answer 17

• form long (polypeptide) chains which run parallel to one another. the chains are linked by cross-links/bridges, forming very stable molecules.
• provide structural functions.

Question 18

Globular proteins; structure and function

Conjugated proteins; structure

Answer 18

• form ‘round’ structures due to the hydrophobic areas (R groups in amino acids) folding inwards while the hydrophilic areas arrange around the external surface.
• provide metabolic functions.
• proteins that occur in combination with a non-protein (prosthetic) substance that is permanently bound to the protein, and are specific non-polypeptides required for the biological function of some proteins.

Question 19

The induced fit hypothesis

Answer 19

When the substrate binds to the enzymes active site, it ‘induces’ a change of shape onto the active site. This puts strain onto the substrate, which distorts it, lowering the activation energy.

Question 20

Factors affecting enzyme activity and how

Answer 20

Temperature; increasing temp mean increased kinetic energy, resulting in the enzymes and substrate moving more rapidly and successfully colliding more often in a given time.

pH; a change in pH alters the charges on the amino acids that make up the active site of enzymes, resulting in changes of shape of the active site, therefore no longer complementary to substrate, so enzyme-substrate complex cannot be formed.

Enzyme Concentration;
- Low - too few enzyme molecules to allow for all substrate molecules to find an active site at one time.
- Intermediate - all substrate molecules can occupy an active site at one time.
- High - excess enzyme molecules has no effect due to there being enough active sites already.

Question 21

What are the two types of enzyme inhibitor?

Answer 21

Competitive inhibitor
Non-competitive inhibitor

Question 22

Competitive inhibitors function

Answer 22

have similar molecule shape to substrate molecules. occupy the active site of an enzyme, ‘competing with it’. not permanent however greatly slows rate of reaction.

Question 23

Non-competitive inhibitors function.

Answer 23

attach to enzyme at ‘non-active site’ binding site, and alters the shape of the active site by changing the enzyme shape. stops active site and substrate being complementary so can’t bind. only permanent if inhibitor remains bound to enzyme.