Biological Molecules

Question 1

Water

Answer 1

Water
- Water is a polar molecule (2H+, 1O-)

• Water is a metabolite (used in metabolic reactions such as condensation and hydrolysis.
• Water is a solvent in which chemical reaction can take place (also used to carry substances such as in blood)
• Water has a high specific heat capacity, minimises temperature fluctuations so acts as a buffer in living organisms
• Water has a high latent heat of vaporisation, evaporation of water provides cooling effect with minimum water loss
• Water has strong cohesion between water molecules, allows transport of water in columns. Strong cohesion creates surface tension between water and air (pond skaters)
• Ice is less dense than liquid water so floats to top. This acts as an insulator for the water bellow and as a habitat for organisms (polar bears)

Question 2

Monomers and Polymers

Answer 2

Monomers and Polymers
- Monomers, small units that are a part of larger molecules
- Polymers, are molecules made out of monomers
- Condensation combines monomers by creating chemical bond between two molecules
- Hydrolysis breaks chemical bond between two molecules

Monomers: Monosaccharides (Carbohydrates), Amino Acids and nucleotides

Question 3

Carbohydrates

Answer 3

Carbohydrates
- Carbon, Hydrogen and Oxygen
- Joined together by glycosidic bonds

Question 4

Monosaccharides

Answer 4

Monosaccharides
- Glucose, contains 6 carbon atoms (hexose sugar)
- Alpha Glucose, Carbon 1 hydroxyl group points below the ring
- Beta Glucose, Carbon 1 hydroxyl group points above the ring

Question 5

Disaccharides

Answer 5

Disaccharides
- Maltose = Glucose + Glucose
- Sucrose = Glucose + Fructose
- Lactose = Glucose + Galactose

Question 6

Polysaccharides

Answer 6

Polysaccharides

• Glycogen, formed from alpha glucose molecules joined together by 1,4 glycosidic and 1,6 glycosidic bonds. Large number of branches and compact
• Starch consists of Amylose and Amylopectin
• Amylose is unbranched chain of glucose molecules joined by 1,4 glycosidic bonds. Amylose is coiled and very compact so can store lots of energy
• Amylopectin is branched chain of glucose molecules joined by 1,4 and 1,6 glycosidic bonds. Similar to glucose but has less branches due to less energy demands in plants than animals
• Cellulose, consists of unbranched beta glucose chains joined by beta 1,4 glycosidic bonds
• Microfibrils are strong threads
  which are made of long cellulose chains joined together by hydrogen bonds and they
  provide structural support in plants cells.

Question 7

Lipids

Answer 7

Lipids
- Saturated Lipids don’t contain carbon double bonds, all carbon atoms are bonded to 2 hydrogen atoms
- Unsaturated Lipids, Contain carbon-carbon double bonds, not all carbon atoms are bonded to 2 hydrogen atoms
- More unsaturated bonds, weaker intermolecular forces, lower melting points

Triglycerides
- One molecule of glycerol attached to three molecules of fatty acids
- Used as energy reserves in plants and animals

Phospholipids
- One of the fatty acid tails in the triglycerides is substituted for a phosphate group (phosphate head)
- The phosphate head is Hydrophilic (attracted to water) and the tails are hydrophobic (repel water). This forms the phospholipid bilayer

Question 8

Proteins

Answer 8

Proteins
- Amino group, NH2
- Carboxylic Group
- Variable R group

• Amino acids are joined by peptide bonds
• Primary Structure, order of amino acids in a chain
• Secondary Structure, hydrogen bonds cause chain to fold into its secondary structure, region of beta plated sheets or alpha helixes can form
• Tertiary Structure, Further folds into its 3D structure