1. Biological Molecules

Question 1

Uses of carbohydrates

Answer 1

1. Respiratory substrates in cells
2. Form structural components in plasma membranes and cell walls

Question 2

Uses of lipids

Answer 2

1. Bilayer of plasma membranes
2. Hormones
3. Respiratory substrates

Question 3

Uses of proteins

Answer 3

1. Form cell structures
2. As enzymes
3. As chemical messengers
4. As components of the blood

Question 4

Uses of nucleic acids

Answer 4

Carry the genetic code for the production of proteins. (in viruses & all living organisms-> evidence for evolution)

Question 5

Def and examples of monomers

Answer 5

The smaller units from which larger molecules are made.
eg. 1️⃣ Monosaccharides
2️⃣ Amino acids
3️⃣ Nucleotides

Question 6

Polymers

Answer 6

Molecules made from a large no. of monomers joined tgt.

Question 7

Condensation reaction

Answer 7

Joins 2 molecules tgt
w/ the FORMATION of a chemical BOND &
involves the ELIMINATION of a molecule of WATER.

Question 8

Hydrolysis

Answer 8

BREAKS a chemical BOND between 2 molecules &
involves the USE of a WATER molecule.

Question 9

Monosaccharides
- def
- general formula
- examples

Answer 9

• the monomers from which larger carbohydrates are made
• (CH2O)n
• 1️⃣ Glucose
  2️⃣ Galactose
  3️⃣ Fructose

Question 10

Condensation reaction between 2 monosaccharides

Answer 10

1. Glycosidic bond
2. Water

Question 11

Formation of polysaccharides by condensation- examples

Answer 11

α-glucose -> glycogen
-> starch
β-glucose -> cellulose

Question 12

Examples of disaccharides

Answer 12

1. M𝘢𝘭tose- 2 x glucose (p𝘢𝘭)
2. S𝘶crose- gl𝘶cose + fr𝘶ctose
3. Lactose- Glucose + galactose

Question 13

General formula of monosaccharides

Answer 13

(CH2O)n

Question 14

α-glucose

Answer 14

CH2OH–O
H

Question 15

What is an isomer?

Answer 15

Same molecule (same no. of atoms), different arrangement

Question 16

Organisms that move use lipids rather than carbohydrates as an energy source. Suggest why.

Answer 16

Lipids provide more than twice as much energy as carbohydrate when oxidised.
This means the same amount of energy can be provided for less than half the mass.
Therefore, it is a lighter storage product- major plus if the organism is motile (able to move around).

Question 17

The points where one collagen molecule ends and the next begins are spread out throughout the fibre, rather than all being in the same position along it.
Explain how this arrangement of collagen molecules is necessary for the efficient functioning of a tendon.

Answer 17

The junctions between adjacent collagen molecules- points of weakness.
If they are all at the same point in a fibre
-> a major weak point
=> the fibre might break

Question 18

What is a DNA molecule?

Answer 18

• double helix
• 2 polypeptide chains
• held tgt by H bonds
• between specific complementary base pairs

Question 19

What kind of reactions can the hydrolysis of ATP be coupled to?

Answer 19

Energy-requiring reactions within cells.

Question 20

What are the roles of lipids?

Answer 20

1. Source of energy
   
   • releases > 2x energy than carbohydrates when oxidised + produces water
2. Waterproofing
   
   • insoluble in water
3. Insulation
   
   • retain body heat ∵ slow conductors of heat
   • electrical insulators- myelein sheath around nerve cells
4. Protection around delicate organs

Question 21

Advantages of triglycerides

Answer 21

1. Source of energy
   
   • ↑ energy-storing CH bonds : C atoms
2. Good storage molecules
   
   • ↓ mass : energy (↑ energy stored in small vol–> ↓ mass
3. Insoluble in water
   
   • x affect H2O potential ∵ large & non-polar
4. Source of water
   
   • ↑ H : O atoms –> release water when oxidised

Question 22

Why did many scientists initially doubt that DNA was the genetic code?

Answer 22

• chemically simple w/ few components
• proteins in chromosomes believed to contain genetic info ∵ proteins showed ↑ variation

Question 23

Describe 3 roles of RNA.

Answer 23

1. transfer genetic info from DNA to ribosomes
2. • proteins –> ribosomes
3. protein synthesis

Question 24

What is a metabolic pathway?

Answer 24

A series of reactions in which each step is catalysed by an ezyme.

Question 25

What is end-product inhibition?

Answer 25

- non-competitive - negative feedback loop of end product inhibiting action of first enzyme in the metabolic pathway - if conc of end product ↑, inhibition of first enzyme ↑ ∴ ↓ end products produced --> conc back to normal

Question 26

Suggest how the cross-linkages between the amino acids of polypeptide chains increase the strength and stability of a collagen fibre.

Answer 26

- prevents individual polypeptide chains from sliding past one another --> gain strength ∵ act as a single unit

Question 27

Explain why changing certain amino acids that are not part of the active site also prevents the enzyme from functioning.

Answer 27

- changed a.a. may be one that forms H bonds w/ other a.a. - if new a.a. X form H bonds, - tertiary structure changes- including a.s. - substrate will no longer fit

Question 28

Suggest a possible purpose of enzyme Y in the mammalian stomach.

Answer 28

- milk = only food in diet of young mammals - enzyme coagulates milk--> remains in stomach for longer --> ↑ time for enzymes to act on + broken down & absorbed - if liquid--> passes thru stomach ↑ quickly--> only partially digested

Question 29

Suggest why enzymes are attached to the inner membrane of an organelle 'in a very precise sequence'.

Answer 29

- product of one reaction acts as substrate for next reaction - sequence ↑ chance of each enzyme coming into contact w/ substrate - ↑ efficient production of end product

Question 30

Suggest an advantage of end-product inhibition being non-competitive rather than competitive.

Answer 30

- level of end product X fluctuate w/ changes in level of substrate - non-comp X competing for a.s. - X affected by substrate conc.

Question 31

Role of iron ions

Answer 31

- haemoglobin- 4 polypeptide chains w/ Fe2+ in the centre - binds to O2 (temprarily becomes Fe3+ until O2 is released)

Question 32

Role of hydrogen ions

Answer 32

Affects enzyme-controlled reactions - conc. of H+

Question 33

Role of sodium ions

Answer 33

co-transport of glucose & amino acids across cell surface membrane alongside Na+

Question 34

Roles of phosphate ions

Answer 34

1. bonds between phosphate group STORE ENERGY in ATP 2. phosphate groups in DNA & RNA --> nucleotides join to form polynucleotides

Question 35

Structure of glycerol

Answer 35

---H l H-C-OH l H-C-OH l H-C-OH l H