Optional: Biochemistry

Question 1

Define Km

Answer 1

Inverse measure of affinity of enzyme for a substrate

Question 1

How to convert between exponenital and log form?

Answer 1

a^x = b
x = loga b

Question 2

Iodine number

Answer 2

(Mass of iodine reacted/mass of lipid) *100

Question 3

Site of reactivity and conditions that favour oxidative and hydrolytic rancidity

Answer 3

Oxidative: Carbon=carbon unsaturated bond and light
Hydrolytic: ester and high heat and temperature

Question 4

Describe the function of chlorophyll in photosynthesis. (2)

Answer 4

Aborbs light energy and transfers electrons

Question 5

Bonding in cellulose, starch and glycogen

Answer 5

Cellulose: straight chain 1-4 beta
Starch: Amylose 1-4 alpha straight, branched chain amylopectin alpha 1-4 and 1-6
Glycogen: Highly branched like amylopectin but more 1-6 bonds

Question 6

Suggest why glycine and isoleucine separate slightly at pH = 6.5

Answer 6

They are different sizes/molar masses so they move at different speeds

Question 7

Functional group responsible for holding protein in secondary structure

Answer 7

Carboxamide

Question 8

Explain why linoleic acid, C18H32O2, is a more efficient energy storage molecule than raffinose, C18H32O16 (2)

Answer 8

Linoleic acid is more exothermic and less oxidized so can be oxidized and lose more e providing energy

Question 9

What does water solubility depend on

Answer 9

Forming MANY hydrogen bonds with water

Question 10

Whcih fat has highest boiling point?

Answer 10

Straight chain, saturated, more LDF

Question 11

General formula of carbohydrate

Answer 11

Cx(H2O)y

Question 12

Why is Vitamin D soluable in fats?

Answer 12

Hydrcarbon chain forms LDF with fats

Question 13

How do heavy metals decrease enzyme action?

Answer 13

They react with enzyme, breaking disulfide bonds

Question 14

Suggest one challenge scientists face when scaling up synthesis of a new compound

Answer 14

Minimizing negative impact on environemnt and considering atom economy

Question 15

Why is DNA negatively charged

Answer 15

Phosphate group ionized

Question 16

Why do anthocyanins absorb visible light?

Answer 16

Extensive conjugation

Question 17

Explain the shape of the oxygen dissociation curve at the start (low oxygen partial pressure?

Answer 17

Oxygen binds to first active site of hemoglobin which alters shape of other active sites

Cooperative binding causes increased affinity of hemoglobin to O2

**no coperative binding in mygolbin cause only 1 heme group

Question 18

Outline how the formation of 11-trans-retinal results in the generation of nerve signals to the brain (2)

Answer 18

11 trans retinal no longer fits into rhodspin, leading to conformational change in rhodospin to opsin generating signals

Question 19

What allows rhodospin to abosrb visible light?

Answer 19

Extensive conjugation

Question 20

Vision cycle (3)

Answer 20

Extensive conjugation. Vitamin A is oxdized to 11-cis retinal. Cis retinal binds to opsin forming rhodospin . When visible light absorbed, cis-retinal changes to trans retinal which triggers nerve signal. Trans retinal detatches from opsin and is converted back to cis retinal

Question 21

Determine iodine number when given molar mass of compound

Answer 21

1) mass of iodine x number of double bonds
2) (1)/molar mass of compounds * 100

Question 22

How can inclusion of starch in plastics make them biodegradable?

Answer 22

• Carbohydrates make plastic more hydrophillic
• Carbohydrates are broken down by bacteria
• Carbohydrates weakens LDF between polymer chains in the plastic

Question 23

Define GMO

Answer 23

Organism whose DNA has been altered by genetic engineering techniques

Question 24

Wedge and dash of amino acids?

Answer 24

Wedge: Nh2
Dash R group

Question 25

Diffeence between glucose and galactose

Answer 25

H and OH are reversed on C-4

Question 26

D vs L sugars and alpha vs beta

Answer 26

On chiral carbon furthest from aldehyde or ketone group

D - hydrxoyl right
L - hydroxyl left

Alpha - OH below plane C1
Beta - OH above plane C1

Question 27

Why are cellulose fibers strong?

Answer 27

Long straight chains, held by lots of H bonds that make microfibrils

Question 28

Why is cellulose important part of diet?

Answer 28

Adds fiber and prevents obesity

Question 29

Convert between straight chain and cyclic

Answer 29

1) carbon in straight chain, carbonyl group highest priority
2) hydroxyl on second last carbon
3) O from hydroxyl bonds with c 2 and H joins with carbonyl oxygen to form hydroxyl on second carbon

Question 30

Why is atom economy not always a good measure of sustainability

Answer 30

Doesnt take into account catalysts which are renewable and promote pathway of less energy

Question 31

Hemoglobin vs myoglibin

Answer 31

Hemo - 4 polypeptide chains and 4 heme groups, transport O2 and CO2 in bloodstream
Myo - 1 polypeptide chain and 1 heme goup, store O2

Heme group binds to oxygen for hemoglobin to transfer which causes oxidation from iron II to iron III then reduction when oxygen released to cell for respiration, myoglobin

Question 32

why do lipids produce more energy than carbs?

Answer 32

Larger number of reduced carbons so can be oxidized easier

Question 33

Does quinodal base or flavilum red predominent at pH 12

Answer 33

Quinodal loss of proton and positive ion unlikely

Question 34

Similarity between myoglobbin and hemoglbin

Answer 34

Fe cation