Topic 1 - Biological Molecules + Enzymes Flashcards
What is the test for reducing sugars? How does it work?
Benedict’s Test
1) Add food sample into test tube.
2) Add Benedict’s reagent into it.
3) Heat mixture in water bath for 5 minutes.
4) Positive result = green, yellow, orange, red.
Which disaccharide does alpha glucose and galactose make?
Lactose
What disaccharide does alpha glucose and alpha glucose make?
Maltose
What disaccharide does alpha glucose and fructose make?
Sucrose
How is a disaccharide formed?
When monosaccharides join, a molecule of water is removed (condensation reaction). The bond formed is a glycosidic bond.
What is the test for non-reducing sugars? How does it work?
Benedict’s Test
1) Add dilute hydrochloric acid and leave in water bath for 5 minutes
2) Add sodium hydrogencarbonate solution to neutralise acid.
3) Add Benedict’s reagent and place back in water bath for 5 minutes.
4) Positive result = green, yellow, orange, red
The polymer Glycogen:
Monomer it is made from
Structure
Role
Why its role is suited for its structure.
- Alpha glucose
- 1-4 and 1-6 glycosidic bonds, highly branched.
- Storage.
- Insoluble (does not diffuse out of cells), compact, more rapidly broken down to form glucose.
The polymer Cellulose:
Monomer it is made from
structure
role
why its role is suited for its structure.
- Beta glucose.
- 1-4 glycosidic bonds, unbranched, microfibril chains.
- Keeping structure of plant cell walls stable.
- Hydrogen bonds form crosslinks between adjacent chains which strengthens it, high tensile strength of fibres maintain shape and rigidity.
The polymer Starch:
Monomer it is made from
structure
role
why its role is suited for its structure
- Alpha glucose.
- 1-4 and 1-6 glycosidic bonds, branched, coil shape held together by hydrogen bonds.
- Energy storage.
- Insoluble (doesn’t affect water potential, water not drawn into cells by osmosis). Compact, when hydrolysed forms alpha glucose which is easily transported and used in respiration.
What is the test for starch? How does it work?
1) Place sample in test tube.
2) Add few drops of iodine solution.
3) Positive result = blue-black colour.
What are the main roles of lipids?
- Energy source (provide twice as many calories as carbohydrates + proteins).
- Waterproofing (waxy cuticle).
- Insulation.
- Protection (delicate organs have fat around them).
What is a triglyceride? What is the main features of them?
Composed of 1 glycerol molecule and 3 fatty acids that join via 3 condensation reactions. The bond that joins them is an ester bond.
- Low mass to energy ratio (good storage).
- Insoluble in water.
- High ratio of hydrogen to oxygen atoms (release water when oxidised).
- High ratio of energy-storing carbon-hydrogen bonds to carbon atoms (excellent source of energy).
Do saturated fatty acids have single carbon bonds or double?
Single.
Do unsaturated fatty acids have single carbon bonds or double?
Double.
What is a phospholipid? What are its main features?
One fatty acid replaced by a phosphate molecule.
- Hydrophilic ‘head’ (likes water, not fat).
- Hydrophobic ‘tail’ (hates water, mixes with fat).
- Bipolar layer (hydrophilic head faces outwards, hydrophobic tails face towards the centre).
What is the test for lipids? How does it work?
Emulsion test.
1) Add sample to test tube.
2) Add ethanol and shake vigorously.
3) Add distilled water and shake gently.
4) Positive result = milky-white emulsion.
What is a protein? What are the 3 major parts of them?
Three dimensional molecules whose monomers are the 20 different amino acids found in nature.
Consists of: Amine group, R group, and a Carboxyl group.
How are dipeptides formed?
Amino acids become linked by a new peptide bond between carbon atom of one amino acid and the nitrogen atom of the other. Formed by the removal of water (hydrolysis reaction).
What is the primary structure of protein responsible for?
Polymerisation forms polypeptides - determines the protein’s shape and function. Sequence of amino acids.
What is the secondary structure of a protein responsible for?
Long polypeptide chain twisted into a 3D shape - alpha helix or beta pleated sheets.
What is the tertiary structure of a protein responsible for? What bonds does it contain?
Structure gives complex, specific 3D structure of each protein.
- Disulfide bridges (fairly strong).
- Ionic bonds (weak, formed between carboxyl and amino groups).
- Hydrogen bonds (weak and easily broken, but numerous).
What is the quaternary structure of a protein responsible for?
More than one polypeptide group. May also contain non-protein groups.
What is the test for proteins? How does it work?
Biuret test.
1) Place sample in test tube.
2) Add sodium hydroxide (room temp).
3) Add few drops of dilute copper(II) sulfate solution and mix gently.
4) Positive result = violet/purple.
What are the main properties of enzymes?
- Biological catalysts.
- Globular proteins at tertiary level.
- Effective in small amounts.
- Most reactions are reversible.
- Most denatured by extreme pH and temperature.
