Biology AS - Biological Molecules

Hydrogen bond- A weak interaction that can occur wherever molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen.

- Density: At colder temperatures, hydrogen bonds form a crystaline structure (Ice) which is less dense and floats - insulates water underneath and protects organisms during winter - Laten Heat of Fusion

- Stable Habitat: Relative amount of energy needed to increase temperature - keeps temperature in rivers and lakes stable for life - Specific Heat Capacity

- Universal Solvent: Allows lots of solutes to dissolve in it - useful in bodily function and for reactions (e.g. blood) - Surface Tension (equal amount throughout bodies)

- Reactions: Water takes place in many important reations in the body and outer world

Adhesion: Water sticks to polar substances

Capillarity: water molecules attracted together and Adhesion - water travels against Gravity

Functions:

• Structural components (Muscle & bone)
• Membrane carriers & pores (Active transport & facilitated diffusion)
• Enzymes are proteins
• Hormones can be proteins and antibodies are proteins too

Bond between Amino Acids is a Peptide Bond

Secondary Structure- Refers to coiling and pleating of parts of the polypeptide molecule (Alpha Helix or Beta Plate)

Tertiary Structure- The overall 3D structure of the final polypeptide/protein molecule - stabilised by coils/pleats and held together by hydrogen bonds. 

- Heating increases kinetic energy of the molecule - causing it to vibrate and break some bonds that hold the tertiary structure in place - denaturing the Protein

- Globular Proteins - Ball shaped structure and are usually soluble in water. They usually have metabolic roles (Enzymes) - Hydrophobic R groups are turned inwards towards the centre of the structure and hydrophillic R groups are usually on the outside so they're soluble

- Fibrous- Form fibres, usually have regular repetitive sequences of amino acids. Usually insoluble in water and have structural roles - e.g. Collagen

Fatty acid molecules have tails of hydrocarbons and are hydrophobic (water repellent)

 - Make lipids insoluble in water

• Saturated Fatty Acids: no double bonds between carbon and tails – saturated with hydrogen
• Unsaturated fatty Acids: double bonds between tail and hydrogen

Ester Bond – created in condensation reaction and broken in a hydrolysis reaction

Cholesterol: help strength the cell membrane – small size allow it to fit between phospholipids and pack closer together (less fluid and more rigid)

Phospholipids: Found in the cell membrane and make up Phospholipid bilayer – the centre (due to the tails) is Hydrophobic so water-soluble substances cannot pass through easily - acts as a cell barrier

- Macromolecules are complex molecules – e.g. Proteins, Lipids and some carbohydrates

- Polymers are large, complex molecules made out of long chains of monomers - broken down in hydrolysis reactions, breaks chemical bond with water molecule

- Biological polymers are formed through condensation reactions – releases water molecules

Alpha & Beta Glucose:

• Has a soluble structure – easily transported
• Chemical bonds contain lots of energy

• Carbohydrates are made up of carbon, hydrogen and oxygen
• Monosaccharides are monomers that make up carbohydrates
• Monosaccharides are bonded together with glyosidic bonds
• Two monosaccharides make up a disaccharide
• More than two monosaccharides make up a polysaccharide

• Calcium – e.g. transmission of nerve impulses and release of insulin
• Sodium – e.g. generating nerve impulses, muscle contraction and regulating fluid balance
• Potassium – e.g. generating nerve impulses, muscle contraction and regulating fluid balance
• Hydrogen – e.g. affects pH, helps photosynthesis and respiration reactions
• Ammonium – e.g.  Absorbed from soil by plants and source of Nitrogen

• Nitrate – e.g. Absorbed from soil by plants -  Nitrogen
• Hydrogencarbonate – e.g. buffer and maintain pH

• Chloride - e.g. maintain pH in blood during gas exchange - acts as cofactor
• Phosphate – e.g. photosynthesis and respiration reactions – synthesis of many biological molecules
• Hydroxide - e.g. affects pH substances