Biological molecules

Question 1

Phospholipid structure

Answer 1

-phosphoric acid head (hydrophilic)
-glycerol
-2 fatty acid chains (hydrophobic)

Question 2

Triglyceride

Answer 2

-one glycerol
-3 fatty acid chains
-ester bond (esterification)

Question 3

Difference between saturated and unsaturated fatty acids

Answer 3

Saturated - No carbon-carbon double bond (have kinks)
(Fats)
Unsaturated - carbon-carbon double bond (no kinks)
(Oils)

Question 4

Amino acid structure

Answer 4

Amine group (NH2)
Carboxyl group (COOH)
R-group (variant)
Hydrogen

Question 5

Polypeptide chain

Answer 5

Long chain of two or more amino acids joined together by peptide bonds

Question 6

Peptide bond

Answer 6

Condensation reaction between carboxyl group and hydroxyl group
H2O released

Question 7

Levels of protein structure

Answer 7

Primary - Specific sequence of amino acids in polypeptide
Secondary - Primary but coiled or folded on itself, hydrogen bonds β, α
Tertiary - Further coiled/folded, 3D shape
Quaternary - Interaction between two or more polypeptides

Question 8

α (secondary) helix

Answer 8

• strong
• helical shape
• result of hydrogen bonds

Question 9

β (secondary) pleated sheet

Answer 9

• weak
• strength achieved through layers and bonds
• result of hydrogen bonds

Question 10

Interactions between R-groups (tertiary)

Answer 10

-disulphide bonds
-ionic bonds
-hydrogen bonds
-hydrophilic/hydrophobic reactions

Question 11

Haemoglobin

Answer 11

• biologically active when it becomes a quaternary structure
• 4 sub-chain units (2 alpha and 2 beta)
• has a prosthetic group called haem group (carry pigment and iron)
• globular protein

Question 12

Globular proteins

Answer 12

• Roll up to form a ball
• Hydrophobic R-groups turn inwards so hydrophilic R-groups outwards
• Usually have metabolic roles
• Enzymes, Plasma proteins, Antibodies, Hormones (insulin), haemoglobin

Question 13

Fibrous Proteins

Answer 13

• Form fibers
• Repetitive sequence of amino acids
• Usually insoluble
• Structural roles
• Collagen and keratin

Question 14

Difference between collagen (C) and haemoglobin (H)

Answer 14

• H is globular, C is fibrous
• H is soluble, C is insoluble
• H has a range of amino acids , C primary structure = 35% glycine
• H has prosthetic haem group, C has no prosthetic group
• H has 2 alpha and 2 beta, C is majority left- handed helix structures

Question 15

Roles of water

Answer 15

• Solvent
• Liquid
• Cohesion and adhesion
• Freezing
• High latent and thermal stability
• Metabolic
• Habitat

Question 16

Why is a molecule polar?

Answer 16

One region of molecule is on average negatively charged than the opposite region
Slightly negative attracted to slightly positive

Question 17

Structure of water

Answer 17

• Oxygen slightly negatively charged
• Hydrogen slightly positively charged
• Covalent bonds

Question 18

What are monomers and polymers?

Answer 18

• Monomer : Individual molecules
• Polymer : The individual molecules bonded to identical molecules
  e.g. chain of identical glucose molecules (monomer) is a (polymer) called starch

Question 19

What is a condensation reaction?

Answer 19

• Two molecules join together
• Release water
  e.g. two glucose molecules

Question 20

What is an hydrolysis reaction?

Answer 20

• When a water molecule is added to split two molecules