Biological molecules

Question 1

Hydrolysis reaction

Answer 1

Reaction which uses water to break down a polymer (incl. disaccharide or polysaccharide) into its constituent monomers by breaking glycocidic bonds

Question 2

Condensation reaction

Answer 2

Reaction between monomer units to form polymers held together by glycosidic bonds, also forming small molecules of H20

Question 3

Metabolism

Answer 3

The sum of all reaction in a cell or organism

Question 4

Isotopes

Answer 4

Atoms of the same element with the same number of protons but different number of neutrons

Question 5

General formula of a monosaccharide

Answer 5

(CH20)n where n=any number between 3 and 7

Question 6

Isomer

Answer 6

Molecules with the same molecular formula but with atoms connected differently

Question 7

Isomers of glucose

Answer 7

ALPHA glucose: on carbon 1 has H on top the OH

BETA glucose: on carbon 1 has OH on top then H

Question 8

Glucose + glucose =

Answer 8

maltose

Question 9

Glucose + fructose =

Answer 9

sucrose

Question 10

Glucose + galactose =

Answer 10

lactose

Question 11

Test for reducing sugars

Answer 11

• add benedict’s solution (copper (ii) suplfate) to food sample
• heat
• an insoluble red precipitate of copper (ii) oxide will form

Question 12

Test for non-reducing sugars

Answer 12

• add Benedict’s solution to to foood sample
• heat
• if remains blue = no reducing sugar present
• add HCl + heat (HCl hydrolyses any disaccharides)
• add sodium hydrogencarbonate solution to neutralise
• check pH
• test with Benedict’s again

Question 13

Test for starch

Answer 13

• add iodine

- if present = blue/black

Question 14

which sugars are reducing?

Answer 14

all monosacharrides and some disaccharides

Question 15

which sugars are non-reducing?

Answer 15

some disaccharides

Question 16

3 main functions of starch in relation to structure

Answer 16

1) insoluble in water = good storage material and doesn’t affect water potential
2) amylose helixs forms compact shape = allows tight packing
3) amylopectine has many protruding ends which can be hydrolysed rapidly = allows rapid release of glucose

Question 17

what is starch made up of?

Answer 17

made of two polymers of alpha glucose:
- amylose
- amylopectin
monomers connected by glycosidic bonds formed in condensation reactions
can be branched or unbranched

Question 18

what is the structure of amylose?

Answer 18

• polysaccharide
• unbranched = coils
• glucose linked linearly with alpha 1-4 linkage

Question 19

what is the structure of amylopectin?

Answer 19

-branched

Question 20

structure of glycogen

Answer 20

• polymer of alpha glucose
• has more branches + shorter branches than starch
• more compact than amylopectin

Question 21

function of glycogen

Answer 21

• compact structure allows faster hydrolysis than starch = faster release of glucose in animals/bacteria (higher surface area for enzymes to work)
• insoluble = doesn’t affect osmosis + doesn’t diffuse out cells

Question 22

where is glycogen stored in animals

Answer 22

muscles and liver as small granules

Question 23

what is cellulose made up of?

Answer 23

• alpha AND beta glucose (different to starch + glycogen)
• forms straight, unbranched chains (not coiled) which run parallel to each other with hydrogen bonds forming cross linkages
• cellulose molecules grouped together to form microfibrils then fibres

Question 24

how is the structure of cellulose suited to its function?

Answer 24

• hydrogen bond cross links in thr long, unbranched fibrous structure gives great physical strenght - good for cell walls
• hydrogen bonds prevent water entering molecule so molecules are resistant to enzyme hydrolysis = strong

Question 25

what are lipids made up of?

Answer 25

carbon, oxygen, hydrogen the proportion of carbon to oxygen and hydrogen is smaller than in carbohydrates

Question 26

are lipids insoluble or soluble?

Answer 26

insoluble in water soluble in organic solvents, e.g. acetone or alcohols

Question 27

what are the four roles of lipids?

Answer 27

- insulation - energy source (when oxidised, more than carbs) - waterproofing - protection

Question 28

what is the structure of a triglyceride?

Answer 28

- consists of : 3 fatty acids and 1 glycerol - each fatty acid forms an ester bond with glycerol in a condensation reaction - the difference between different lipids is due to the varying structure of fatty acids

Question 29

whats the difference between a saturated, mono-unsaturated and a polyunsaturated fatty acid?

Answer 29

- saturated = no double bonds - monounsaturated = a single double bond - polyunsaturated = more than 1 double bond

Question 30

functions of triglycerides related to their structure

Answer 30

- have a high ratio of energy-strong carbon-hydrogen bonds to carbon atoms = good energy source - low mass to energy ratio = lots of energy in small area - insoluble: doesn't affect cell water potential - when oxidised release water due to lots of hydrogen/oxygen

Question 31

whats the difference between a triglyceride and a phopholipid

Answer 31

one fatty acid molecule is swapped for a phosphate group

Question 32

where are phopholipids used and why?

Answer 32

cell membranes because they have: - a hydrophobic tail (repel water) - a hydrophillic head (attracts water) so they form a bilayer, controlling what can enter/exit the cell (water-soluble substances can't easily pass through)

Question 33

steps in the emulsion test for lipids

Answer 33

- place test substance in test tube w/ ethanol + shake - add distilled water - any lipid = milky emulsion