Biological Molecules

Question 1

Water properties

Answer 1

• polar molecule
• liquid, low viscosity and transport medium
• provide habitats
• more dense than ice
• high specific heat capacity
• high latent heat of evaporation

Question 2

monosaccharides

Answer 2

simple sugars- CnH2nOn
3 types - glucose, fructose, galactose
many together make polysaccharides
hexose monosaccharides= glucose&galactose

Question 3

reducing sugars

Answer 3

can donate electrons (lactose&maltose)

Question 4

non reducing sugars

Answer 4

cannot donate electrons

• cannot oxidise so must be hydrolysed to break into monosaccharides (then use benedicts)
• sucrose

Question 5

polysaccharides

Answer 5

many monosaccharides joined together by glycosidic bonds

• starch
• protein
• DNA

Question 6

carbohydrates

Answer 6

function
-source and store of energy
-structural units
-can form larger molecules
made of carbon oxygen hydrogen
glucose (monomer) - starch(polymer)

Question 7

amylose

Answer 7

form of starch in plants
long alpha glucose spiral chains with glycosidic bonds between carbons (1&4)
-some hydrogen bonds (help spiral shape)

Question 8

amylopectin

Answer 8

form of starch in plants branched

• alpha glucose chains & glycosidic bonds between (1&4)
• also has branching chains between carbons (1&6)

Question 9

glycogen

Answer 9

storage of alpha glucose in animals
-more easily broken down than starch as animals have high metabolic rate
- shorter and more branched than starch
has gb’s between 1&4 and hydrogen bonds 1&6

Question 10

lipids

Answer 10

contain carbon, hydrogen, oxygen

• insoluble in water
• but soluble in organic substances (alcohol)
• made of saturated fatty acids
• fats solid at room temp
• oils made of unsaturated fatty acids

Question 11

triglycerides

Answer 11

Made of 3 fatty acids and glycerol

• each FA forms an ester bond with glycerol
• insoluble in water
• release water when oxidised
• low mass : energy ratio

Question 12

phospholipids

Answer 12

Made of 2 fatty acids, glycerol & phosphate group
phosphate head= hydrophylic
fatty acid tail=hydrophobic (create bilayer)
-Amphipathic
-structure allows them to bind with carbohydrates forming glycolipids

Question 13

cholesterol

Answer 13

small, fully hydrophobic molecule
Functions-makes hormones, testosterone&oestrogen
-in plants, produce stigmasterol (a derivative in membranes)
thin-inserts self into bilayer

Question 14

Proteins

Answer 14

Large molecules made of long chains of amino acids
eg enzymes
combine in polymer = polpeptides 
amino acid = monomer

Question 15

Amino acids

Answer 15

Made of:
amine group (NH2) , R group, carboxyl group (COOH) acid part
-Plants make their own amino acids using nitrates7& products from photosynthesis
-Animals make some but need to digest others

Question 16

protein structures

Answer 16

primary-sequence of amino acids& peptide bonds
(condensation reaction)
Secondary- alpha helix or beta pleated sheet -hydrogen bonds on peptide back bone
Tertiary- disulphide bridges formed between R groups,ionic bonds between amine&carboxyl group
Quaternary-many polypeptide chains& prosthetic group

Question 17

Fibrous proteins

Answer 17

Formed of regular&repetitive amino acids sequence
-Form paralell polypeptide chains
eg collagen-(connective tissue)
keratin-(nails&claws)
silk-(forms spiders webs)

Question 18

globular proteins

Answer 18

Have a spherical shape
-tightly folded polypeptide chains
-hydrophobic groups-inside
-hydrophylic-outside
eg transport proteins-haemoglobin,myoglobin
Enzymes-lipase&DNA polymerase

Question 19

Inorganic ions

Answer 19

an ion-atom or molecule that has an electric charge
-mostly those that DO NOT contain carbon
cations = ca2+, Na+, K+
anion = NO3-, OH-, HCO3-

Question 20

food tests

Answer 20

starch- iodine drop goes blue/black
lipids-emulsion test -add ethanol & shake then add water (white emulsion)
proteins-use buiret if protein is present then solution changes from blue–>lilac (shows peptide chains)

Question 21

testing for reducing & non reducing sugars

Answer 21

reducing- donate electrons
heat with benedicts solution= brick red if present
Non reducing- hydrolyse first to free up reducing groups
-test for reducing to make sure there are non present to start
-boil with HCl to hydrolyse the sucrose into glucose & fructose
-use sodium hydrocarbonate to neutralise
-test for reducing sugars as normal= yellow/orange result =eg sucrose was present

Question 22

fibrous proteins

Answer 22

fibrous-formed of regular&repetitive amino acid sequences (parallel polypeptide chains)

• collagen; connective tissues
• keratin; nails&claws
• silk; spiders webs

Question 23

globular proteins

Answer 23

Have spherical shape caused by tightly folded polypeptide chains
-hydrophobic groups inside
hydrophylic group on outside
-enzymes (lipase)
-hormones (oestrogen)