A-level bio

what are monomers

smaller repeating units from which larger molecules are made

what are polymers

molecules made from many similar monomer molecules

condensation reaction

joins monomers together and forms a chemical bond and releases water

hydrolysis reaction

2 monomers separated,

breaks a chemical bond

and uses water

carbohydrates

What are monosaccharides? Give 3 common examples

● Monomers from which larger carbohydrates are made

● Glucose, fructose, galactose

α-glucose

beta glucose

Describe the difference between the structure of α-glucose and β-glucose

● Isomers - same molecular formula but differently arranged atoms

● OH group is below carbon 1 in α-glucose but above carbon 1 in β-glucose

What are disaccharides and how are they formed?

● Two monosaccharides joined together with a glycosidic bond

● Formed by a condensation reaction, releasing a water molecule

List 3 common disaccharides & monosaccharides from which they’re made

gm

gl

fs

Draw a diagram to show how two monosaccharides are joined together

What are polysaccharides and how are they formed?

● Many monosaccharides joined together with glycosidic bonds

● Formed by many condensation reactions, releasing many water molecules

Basic function of cellulose

FUNCTION:
provides strength and structural support to plants/algae cell walls

STRUCTURE

• cellulose is made of beta-glucose by condensation reaction (monomer)

• has a straight chain

• has only 1-4 glycosidic bonds

how does the structure of cellulose relates to it function

Every other β-glucose molecule is inverted

1. Long and straight chains;

2. Become linked together by many hydrogen bonds to form fibrils;

3. Provide strength (to cell wall)

1.basic function of starch and 2.structure

1.energy store in plant cells

2. - polysaccharide of alpha-glucose

• amylose has 1,4-glycosidic bonds so is unbranched

• amylopectin has 1,4 and 1,6 glycosidic bond so is branched

how does the structure of starch relate to its function

• insoluble —→ so dosent affect water potential

• helical ——> compact

• large molecule —→ cannot leave cell

• branched —→ so makes molecule compact

• polymer of alpha glucose —> so provides glucose for respiration

• branched ——> more ends for fast breakdown/hydrolysis

basic function and structure of glycogen

function - energy store for animal cells

structure:

polysaccharide of alpha glucose

branched

has 1,4 and 1,6 glycosidic bonds

coiled

suggest how glycogen acts as a source of energy

• hydrolysed to glucose

• glucose used in respiration

describe how the structure of glycogen relates to its function

• insoluble —> dosent affect water potential

• branched —→ so makes molecule compact

• polymer of alpha- glucose —→ so provides glucose for respiration

• branched —→more ends for fast breakdown /hydrolysis

• large - cant cross/leave cell membrane

which are reducing and non-reducing sugars

reducing sugars:

• all monosaccharides (glucose, fructose, galactose)

• maltose

• lactose

non - reducing sugar:

sucrose

TEST FOR REDUCING SUGARS

• add benedicts solution to the sample

• heat in boiling water bath

• +ve result —→ green/yellow/orange/ red precipitate

TEST FOR NON- REDUCING SUGAR

• do benedicts test and it remains blue/ -ve

• heat in a boiling water bath with acid

• neutralise with alkali

• heat in a boiling water bath with benedicts solution

• +ve —→ green/yellow/orange/ red precipitate

TEST FOR STARCH

• add iodine dissolved in potassium iodide and stir it

• +ve result —> blue-black

Use of a colorimeter in a investigation would improve the repeatability of the student’s results.

• quantitative

• strandises the method