Biological Molecules Flashcards
What is meant by a polymer?
Molecule made from a large number of monomers joined together.
Explain the difference between triglycerides and phospholipids.
Phospholipids have one phosphate that replaces a fatty acid tail.
What are lipids saturated with?
Hydrogen
What are the 4 properties of saturated fats?
- All three fatty acid tails have single bonds.
- Solid at room temperature.
- Higher melting point than unsaturated fats.
- Usually derived from animals.
What are the 4 properties of unsaturated fats?
- One or more fatty acids have one or more double bond.
- Usually liquid at room temperature.
- Have lower melting point than saturated fats.
- Usually derived from plants.
Are saturated fats liquid or solid at room temperature? Why?
Solid, because they have no double bonds, so the fatty acid tails don’t kink (like unsaturated do), so the triglycerides are closely compact, so have a higher melting point.
Describe a test and the positive result of lipids present in a food sample.
Crush food sample.
Mix 2 cm^3 of sample in a dry and grease free test tube with 5 cm^3 of alcohol (ethanol).
Shake.
Pour the mixture into 5 cm^3 of water.
A white emulsion shows that a lipid is present.
Is the hydroxyl group at the bottom or top for alpha glucose?
Bottom
What bond is formed when two glucoses form a disaccharide, during a condensation reaction?
Glycosidic bond
Sucrose = _______+______
Sucrose = glucose + fructose
Lactose = _______+________
Lactose = glucose + galactose
Maltose = ________+_______
Maltose = glucose + glucose
Describe the method for testing for reducing sugars.
- Add an equal quantity of Benedict’s reagent to approximately 2 cm^3 of sample solution.
- Stir, and heat for a few minutes and 95oC in a water bath.
- A precipitate indicates reducing sugar.
No reducing sugar = blue (sucrose)
0.5% green
1% yellow
2% brick red
What are reducing sugars?
Sugars that can donate electors to another molecule, becoming the reducing agent, because OILRIG.
Give an example of a non-reducing sugar.
The disaccharide Sucrose
What are the two types of polysaccharide?
Storage: starch and glycogen
Structural: cellulose
What is the test for starch?
Iodine test
1. Place 2 cm^3 of test solution into a test tube.
2. Add two drops of iodine solution and shake and stir.
3. Turns iodine blue-black from yellow if starch is present.
Explain how the glycogen molecule is suited to its function.
Molecules of alpha-glucose joined by 1,4 and 1,6 glycosidic bonds.
Has a large number of side branches meaning that enemy can be released quickly as enzymes can act simultaneously on themselves branches.
Large but compact molecule, stores a lot of energy in a small space.
It is insoluble so doesn’t affect water potential.
Is insoluble so doesn’t diffuse out of cells.
Define an isomer.
Monomers that have the same chemical formula but different structural formulas.
What chemical is used to measure glucose concentration?
Potassium permanganate
Why is glucose stored as glycogen in animals and not as starch?
Animals have a higher metabolism and glycogen is much more branched.
What is a hydrolysis reaction?
Breaks a chemical bond between two molecules and involves the use of a water molecule.
What is the test for non-reducing sugars?
- Sample in liquid form.
- Add equal volumes of Benedict’s solution to the sample in a test tube.
- Place sample in a water bath and gently boil: if solution doesn’t change colour then a reducing sugar isn’t present.
- Add a new amount of sample solution to a new test tube, adding an equal volume of dilute Hydrochloric acid, to hydrolyse any disaccharides into their monosaccharides.
- Gently boil sample for 5 minutes.
- Neutralise the Hydrochloric acid with sodium hydrogencarbonate.
- Add Benedict’s reagent and gently boil in a water bath.
- If a non-reducing sugar is present, the Benedict’s reagent turns orange-brown.
Define monomers.
Give three examples.
Monomers are the smaller units from which larger molecules are made.
Monosaccharides, amino acids and nucleotides.
