Topic 2 Molecular Biology 2.1-2.4

Question 1

2.1 Name the common elements in living organisms

Answer 1

Carbon, hydrogen, oxygen, nitrogen

Question 2

2.1 Define organic

Answer 2

Contains carbon/ C-H bonds

Question 3

2.1 What are the 4 types of molecules

Answer 3

Carbohydrates, lipids, proteins and nucleic acids

Question 4

2.1 Exceptions to “organic=has carbon and C-H bonds”

Answer 4

CO2 has carbon but inorganic, urea no C-H bonds but organic

Question 5

2.1 What is anabolism and catabolism

Answer 5

Anabolism: from macromolecules to monomers, require ATP to build large molecules from small ones
Catabolism: from monomers to macromolecules, releases energy from breaking down larger molecules, the energy is reused in the cell

Question 6

2.1 What is metabolism

Answer 6

Sum of all enzyme catalysed reactions in an organism

Question 7

2.1 Name a substance that contains 1) nitrogen and 2) phosphorus

Answer 7

1) amino acids

2) nucleic acids

Question 8

2.2 What is hydrogen bonding?

Answer 8

Bonds formed between hydrogen (partially positive) of a molecule and an electronegative atom from another- usually oxygen, nitrogen, fluorine (partially negative).

Question 9

2.2 Explain what is cohesion and adhesion

Answer 9

Cohesion= the attraction between water molecules allowing them to stick together
Adhesion= the hydrogen bonds that can form between water and other polar molecules

Question 10

2.2 How are water’s cohesive and adhesive properties useful to living organisms- state example

Answer 10

Allows water to travel up xylem vessels in plants, keeping cell walls moist

Question 11

2.2 What are water’s thermal properties? Explain them

Answer 11

• (High) latent heat of vaporization= the heat needed to break hydrogen bonds allowing them to change state, high meaning it doesn’t vaporize easily
• (High) specific heat capacity= heat needed to raise water temperature by 1 degree. hydrogen bonds restrict movement of water molecules so lots of energy is needed to increase temp
• (High) boiling point= highest temperature a substance can reach at liquid state. water doesn’t start to boil until high temperatures

Question 12

2.2 How are water’s thermal properties significant to living organisms?

Answer 12

Allows water to be a stable and neutral habitat since temperature does not fluctuate easily

Question 13

2.2 Explain solvent properties, surface tension and transparency of water

Answer 13

Solvent properties= dissolves ions and polar molecules
Surface tension= surface acts like an elastic sheet caused by intermolecuar forces, resembles a stretched membrane
Transparency= its transparent!

Question 14

2.2 How are water’s solvent properties, surface tension and transparency useful to living organisms?

Answer 14

Solvent properties allows organisms to use water to transport substances and allows dissolved substances to react easily with one another
Surface tension allows organisms such as insects to travel on its surface without sinking
Transparency allows sunlight to pass through for photosynthesis to happen and allow animals to see

Question 15

2.2 Water vs methane in terms of mp, bp, heat capacity and latent heat

Answer 15

Water higher mp, bp, heat capacity and latent heat than methane because of hydrogen bonds restricting movements. More energy is needed to melt it, boil it to turn it into vapour, or increase temperature.

Question 16

2.2 How is sodium chloride transported in blood?

Answer 16

Sodium chloride is an ionic compound so its soluble in water, transported dissolved as Na+ and Cl- ions

Question 17

2.2 How is oxygen transported in blood?

Answer 17

Oxygen is non-polar but small enough to be transported in small amounts, relies on hemoglobin in red blood cells to carry large amounts

Question 18

2.2 How are glucose and amino acids transported in blood?

Answer 18

Glucose and amino acids are polar so they can be transported dissoled

Question 19

2.2 How are cholesterol and fats transported in blood?

Answer 19

They are non-polar and insoluble so they have to be transported in lipoprotein complexes

Question 20

2.3 What are carbohydrates?

Answer 20

Organic compounds made of carbon hydrogen and oxygen

Question 21

2.3 What are monosaccharides, disaccharides and polysaccharides?

Answer 21

Monosaccharides= single sugar units with general formula CH2O
Disaccharides= two monosaccharides linked together
Polysaccharides= many monosaccharides

Question 22

2.3 How are monosaccharides converted into polysaccharides?

Answer 22

Through condensation reaction (anabolic process) where the -H group from one molecule and -OH from the other joins to form H2O, allowing many monosaccharides to join together to form polysaccharide

Question 23

2.3 How are disaccharides converted into monosaccharides?

Answer 23

Through hydrolysis reaction (catabolic process) which is the addition of water to split a molecule, reverse of the condensation reaction where water is produced

Question 24

2.3 Name the polysaccharides produced by α-glucose and β-glucose (3 total)

Answer 24

α-glucose - starch and glycogen

β-glucose - cellulose

Question 25

2.3 What are features of the structure of starch? Uses? (7 points)

Answer 25

Made by linking α-glucose molecules, insoluble, -OH groups pointing in same direction/ same orientation giving the polymer a helical shape- good for storage, easy to add or remove glucose molecules, used by plants to store glucose

Question 26

2.3 What are features of the structure of cellulose? Uses? (7 points)

Answer 26

Made by linking β-glucose molecules, insoluble, unbranched, -OH groups pointing in opposite directions/ alternating orientation makes polymer straight, allows cellulose molecules to be arranged in parallel and linked by hydrogen bonds forming cellulose microfibrils- incredible tensile strength, basis of plant walls

Question 27

2.3 Two forms of starch: amylose and amylopectin, which one is branched?

Answer 27

Amylopectin is branched, amylose unbranched

Question 28

2.3 What are features of glycogen? Uses? (5 points)

Answer 28

Made by linking α-glucose molecules, insoluble, similar to amylopectin but more branched, -OH groups pointing in same direction/ same orientation, used by animals to store glucose in liver and muscle cells

Question 29

2.3 What do the monosaccharides, glucose, fructose and galactose make?

Answer 29

α-glucose + α-glucose = maltose
glucose + fructose = sucrose
glucose + galactose = lactose

Question 30

2.3 What are lipids?

Answer 30

Organic compounds made of carbon hydrogen and oxygen, long hydrocarbon chain, do not form polymers, mostly or entirely hydrophobic

Question 31

2.3 What are the three main types of lipids? Describe them

Answer 31

Triglycerides: 3 fatty acids, 1 glycerol, formed from condensation reaction
Steroids: 4 fused rings in their molecules, eg. cholesterol and estrogen
Phospholipids: 2 fatty acids, 1 phosphate, 1 glycerol, partly hydrophobic partly hydrophilic, basis of membranes

Question 32

2.3 What are the 2 parts to a fatty acid?

Answer 32

Carboxyl group and hydrocarbon chain

Question 33

2.3 What are the different types of fatty acids? State their features

Answer 33

Saturated= all single bonds
Unsaturated= one or more double bonds
Monounsaturated= only ONE double bond in chain
Polyunsaturated= MORE THAN ONE double bond
Cis-unsaturated= hydrogen bonds on the same side of double bond
Trans-unsaturated= hydrogen bonds on the opposite sides of double bond

Question 34

2.3 Why do cis-unsaturated fats have lower melting points than trans-unsaturated fats?

Answer 34

There is a bend at the double bond of hydrocarbon chain of cis-unsaturated fats so the molecules don’t stack together as well, usually liquid at room temperatures- oil, trans is solid fat

Question 35

2.3 Discuss health risks of a diet rich of lipids, 3 marks

Answer 35

Saturated fats cause high cholesterol, trans fats causes coronary heart disease, but some populations like kenyans have diets rich in lipids but CHD occurrence is rare

Question 36

2.3 Name uses of lipids, 5 marks

Answer 36

hormone production, cushioning, protection, insulation, form membranes, energy store

Question 37

2.3 How to calculate BMI?

Answer 37

mass in kg/ (height in meters)^2

Question 38

2.3 Carbohydrates vs lipids, name some differences

Answer 38

• carbs stored in liver as glycogen, lipids stored as fat around body
• carbs is short term energy, lipids long term energy
• carbs easier to digest release energy quicker, lipids release more energy per gram. therefore adds less mass to body for same amount of energy stored

Question 39

HOW TO IDENTIFY/DRAW: AMINO ACIDS

Answer 39

1) amine group -NH2 (left)
2) R group (below carbon)
3) carboxyl group -COOH (right)
4) central carbon atom (middle)

Question 40

HOW TO IDENTIFY/DRAW: CARBOHYDRATES- GLUCOSE and RIBOSE

Answer 40

CARBOHYDRATES- arranged in a ring
α-glucose & β-glucose
1) hexagon shape
2) 1st carbon- α has H on top, β has OH on top
3) 2nd- H on top, 3rd- OH on top, 4th- H on top
4) 5th carbon- CH2OH
5) plus oxygen to complete hexagon

ribose
1) pentagon shape
2) 1st-3rd carbon all H on top
3) 4th carbon- C on top, H on bottom
4) Carbon^ connected to H on both sides + OH on top
(C on top can be written as CH2OH instead)

Question 41

HOW TO IDENTIFY/DRAW: LIPIDS + GLYCEROL

Answer 41

• Triglyceride: 3 hydrocarbon chains
• Phospholipids: 2 hydrocarbon chains + phosphate
• Steroid: quadruple 4 ring structure
• glycerol: H-C-C-C-H with H on top of C and OH on the bottom

Question 42

HOW TO IDENTIFY/DRAW: FATTY ACIDS

Answer 42

• Monounsaturated= only ONE double bond in chain
• Polyunsaturated= MORE THAN ONE double bond
• Cis-unsaturated= hydrogen bonds on the same side of double bond
• Trans-unsaturated= hydrogen bonds on the opposite sides of double bond