Biology eduqas CC1

Function of Iron ion in animals

Found in haemoglobin which carries oxygen in the blood

Function of phosphate ion in living organisms

Used to form phospholipids which make up cell membranes

Used to make ADP and ATP

Function of calcium ions in living organisms

Used to strengthen tissues in animals such as bones and teeth and cell walls in plants

What is a metabolite

A molecule formed or used in metabolic reactions.

Why is water an important solvent for organisms

Water is a polar universal solvent. It enables chemical reactions to take place within cells, the transport of materials in the plasma and the removal of metabolic waste.

Why is the high surface tension of water important for organisms

Enables the transport of long columns pf water and nutrients up the stem in the xylem pf plants and small blood vessels in the body

Allow some organisms like pond skaters to walk on water

What is a monosaccharide

simple sugar

general formula CnH2nOn

Examples of monosaccharides

glucose, fructose, galactose, ribose, deoxyribose, glyceraldehyde

Name of the bond formed when two monosaccharides react?

Glycosidic bond

Structure of starch

Polymer of α-glucose monomers; Two forms: amylose (α-1,4-glycosidic bonds, unbranched) and amylopectin (α-1,4- and α-1,6-glycosidic bonds, branched).

How does the structure of glycogen relate to its function?

Its highly branched enabling the rapid hydrolysis of glucose molecules

Describe the function and structure of cellulose

Linear polysaccharide that is the main component of the cell wall in plants.

Consists of many B-glucose molecules joined by B-1-4 glycosidic bonds

Alternate glucose molecules rotated 180 degrees allowing hydrogen bonds between parallel chains, forming microfibrils

Describe the structure and function of chitin

Linear polysaccharide found in the exoskeletons of insects and crustaceans as well as fungal cell walls; Consists of many β-glucose molecules (with amino acid side chains) joined by β-1,4-glycosidic bonds; Alternate glucose molecules rotated 180° allowing hydrogen bonds between parallel chains, forming microfibrils.

Relate the structure of triglycerides to their functions

High energy-to-mass ratio- energy storage, high calorific value from oxidation

Insoluble hydrocarbon chain- no effect on water potential of cells, used for waterproofing

Slow conductor of heat- thermal insulation

Less dense than water- buoyancy of aquatic animals

What is a phospholipid?

A type of lipid formed by the condensation of one molecule of glycerol, two molecules of fatty acid and a phosphate group.

Relate the structure of phospholipids to their functions

Glycerol backbone attached to two hydrophobic fatty acid tails and one hydrophilic polar head

Forms phospholipid bilayer in water- component in cell membranes

Tails splay outwards- waterproofing eg skin

Differentiate between monounsaturated fatty acids and polyunsaturated fatty acids

Monounsaturated fatty acids contain one carbon-carbon double bond

Polyunsaturated fatty acids contain more than one carbon-carbon double bond

What is meant by a low density lipoprotein (LDL)

Combination of triglycerides from saturated fats and protein; Blocks receptor sites, reducing cholesterol absorption; Known as 'bad' lipoproteins.

How do LDLs contribute to the risk of cardiovascular disease?

The high blood cholesterol level caused by LDLs leads to the formation of atherosclerosis plaques

Describe the structure of an amino acid

- Amine group (NH2)

- Carboxyl group (COOH)

- Central carbon atom

- R group (variable depending on the amino acid)

H atom

How are polypeptides formed?

Many amino acid monomers joined together in condensation reaction forming peptide bonds

What is the primary structure of a protein?

sequence of amino acids

Describe the secondary structure of a protein

interaction of amino acids resulting in a-helix or b-pleated sheet

hydrogen bonds hold arrangements in place

Describe the tertiary structure of a protein

Folding of a protein to make a three-dimensional structure held in place by various interactions and bonds

disulphide bonds, ionic bonds, hydrogen bonds, hydrophobic interactions

Describe the quaternary structue

interactions of more than one polypeptide chain

may involve addition of prosthetic groups eg metal ions or phosphate groups

Describe how the structure of fibrous proteins relates to their functions

long polypeptide chains folded in parallel

little tertiary/quaternary structure aside from cross-linkages for strength

this makes them insoluble and good for structural roles

Describe how the structure of globular proteins relate to their function

spherical, compact, highly folded with complex tertiary/quaternary structures

hydrophilic R groups face outwards and hydrophobic R groups face inwards therefore water soluble

metabolic roles eg enzymes

Difference between a reducing and non-reducing sugar

Reducing sugar has a free aldehyde or ketone functional group so can act as a reducing agent

A non-reducing sugar does not have a free aldehyde or ketone functional group so cannot act as a reducing agent

Describe Benedicts test for reducing sugars

1. Add an equal volume of Benedict's reagent to a sample.

2. Heat the mixture in an electric water bath at 100℃ for 5 mins.

3. Observe colour of precipitate formed

Describe the positive test for reducing sugars

Colour change from green to yellow to orange to brown to brick red depending on the quantity of reducing sugar present

Describe the Benedict's test for non-reducing sugars

1. Negative test for reducing sugar

2. Hydrolyse non-reducing sugars with an equal volume of dilute HCl

3.Heat in a boiling water bath for 5 minutes

4. Add NaHCO3 to neutralise the acid

5.Re-test resulting solution with Benedicts reagent

6. Observe the colour of the precipitate formed

Describe the positive result for non-reducing sugars

Colour change from green to yellow to orange to brown to brick red depending on the quantity of non reducing sugars present

Food test used to identify proteins

Biuret test

Describe Biuret test

1. Add an equal volume of the sample to be tested and NaOH. 2. Add a few drops of dilute copper (II) sulfate solution.

3. Mix gently and record any observations.

Describe positive result of Biuret test

Colour change from pale blue to purple.

Describe the iodine-potassium iodide test for starch

Add iodine-Kl solution

Colour change from orange to blue/black in the presence of starch

Describe the emulsion test for fats and oils

- Add ethanol to the sample and shake.

- Allow the mixture to settle.

- Add an equal volume of water.

- Record any observations.

Describe the positive result of an emulsion test

White, cloudy emulsion forms