biological molecules

Question 1

properties of water

Answer 1

• cohesion and surface tension
• high specific heat capacity
• high latent heat of vaporisation
• solvent

Question 2

carbohydrates general

Answer 2

contain oxygen, carbon and hydrogen 
3 forms 
1. glucose = energy source 
2. starch and glycogen = energy store 
3. cellulose = support/ structure

Question 3

glucose

Answer 3

• alpha and beta
• energy source
• component of starch and carbs
• hexose sugar
• highly soluble/ easily transportable

Question 4

disaccharides

Answer 4

2 alpha glucose = maltose (R)
2 beta glucose = cellulose
alpha glucose + fructose = sucrose (NR)
alpha glucose + b galactose = lactose (R)

Question 5

starch

Answer 5

energy store in plants

amylose

• straight chain
• helical
• 1-4 glycosidic
• NO branches

amylopectin

• spiral chape
• 1-4, 1-6 glycosidic
• SOME branches

both plant energy stores, compact so more can be stored and insoluble

Question 6

glycogen

Answer 6

animal and fungi energy store

• 1-4, 1-6 glycosidic bonds
• branched structure
• alpha unit = basic unit

Question 7

starch vs glycogen

Answer 7

starch less compact and less branched, plants have lower metabolic activity and respiration rate compared to animals so require less energy

Question 8

cellulose

Answer 8

plant cell wall component provides structure and support

• straight-chain
• beta = basic unit
• 1-4 glycosidic, H bonds
• NO branches
• insoluble
• flexible

forms fibres - high tensile strength + crisscrossing

Question 9

lipids general

Answer 9

contain carbon, hydrogen and oxygen atoms

soluble in alcohol

Question 10

triglycerides

Answer 10

function = energy source, energy store, insulation

1 glycerol molecule + 3 fatty acids

made by condensation reactions
- ester bond between fatty acid and glycerol

NON-polar - can’t dissolve in water

Question 11

phospholipid

Answer 11

function = make up cell membranes, water-proofing

phosphate head + 2 fatty acid tails

2 ester bonds form
1 between phosphate and body of the molecule
1 between fatty acid tails and body

polar molecules - hydrophobic and hydrophilic parts

Question 12

cholesterol

Answer 12

4 carbon-based rings

Question 13

proteins general

Answer 13

polynucleotides made up of amino acids

peptide bonds form in condensation reactions

Question 14

protein structure levels

Answer 14

PRIMARY
- sequence of amino acids joined by peptide bonds

SECONDARY

• alpha helix coil held together by H bonds
• beta pleated sheets held together by H bonds between parallel chains

TERTIARY

• 3D and globular proteins
• coils, pleats and straight chains
• H, ionic, disulfide bonds and hydrophobic/philic interactions

QUATERNARY

• 2 or more globular chains
• different subunits
• H, ionic, disulfide bonds and hydrophobic/philic interactions

Question 15

globular vs conjugated

Answer 15

globular

• spherical
• soluble in H2O
• compact
• tertiary structure

conjugated

• type of globular
• contain prosthetic group

Question 16

fibrous

Answer 16

long thin structures
insoluble in water
metabolically inactive
STRUCTURAL role

Question 17

CATIONS

calcium 2+

sodium 1+

potassium 1+

hydrogen 1+

ammonium 1+

Answer 17

nerve impulse transmission, muscle contraction

kidney function, carb absorption

protein synthesis, stomata opening

pH, blood regulation, catalysis of reactions

pH, production of nitrate ions, amino acid + nucleic acid

Question 18

ANIONS

nitrate 1-

chloride 1-

hydrogen carbonate 1-

hydroxide 1-

phosphate 3-

Answer 18

nitrogen supply in plants, protein production

balance + charge of K+ and Na+ ions

pH, carbon dioxide transport

pH, catalysis of reactions

cell membranes, nucleic acid, ATP, bone formation

Question 19

non-reducing sugar test

Answer 19

boil in HCl
add sodium hydrogen carbonate
add excess benedict’s
heat 80 degrees 5 mins

Question 20

reducing sugar test

Answer 20

excess benedict’s

heat 80 degreed 5 mins

Question 21

sugar concentration colours

Answer 21

most concentrated - brick red

                             - orange
                             - yellow 
                             - green

Question 22

starch test

Answer 22

add iodine

red - blue/black

Question 23

protein test

Answer 23

add biurets

violet - blue

Question 24

lipid test

Answer 24

ethanol
water
clear - emulsion/cloudy

Question 25

chromatography TLC

Answer 25

thin-layer chromatography

qualitative method
separates individual components of the mixture

2 phases
1 - stationary (paper/silica gel)
2 - mobile (organic solvent)

used to separate amino acids 
rate depends on 
- solubility in the solvent 
- interaction with silica (OH groups very polar allows the formation of H bonds)
- polarity (very polar = fast)
- molecule size

for colourless molecules

1. UV
2. ninhydrin
3. iodine

Question 26

Rf value

Answer 26

= distance travelled by substance/ distance travelled by solvent