A-Level Biology 9700 Notes

Micelles - Stable ball-like structures in the water, hydrophilic tails project inwards away from the water  Fluid mosaic model  Fluid - Phospholipids move sideways  Mosaic - Pattern produced by the scattered protein molecules  Fluidity depends on:  Unsaturated ↑, fluid ↑ Longer the tail, fluid ↓   Temperature ↓, fluid ↓  When temperature decreases, cholesterol intercalates between phospholipid and prevents them from moving around  Ion transportation  Unable to pass through the hydrophobic core of the phospholipid bilayer.  Lined with amino acids with hydrophilic R group  Aquaporin  Water is polar, so it is unable to pass through the hydrophobic part of the phospholipid tail.  Channel proteins are hydrophilic Aqauporins increase permeability of membrane to water  Roles of the components of cell membrane  Phospholipids  Forms a barrier to charged particles  Can modify chemically to act as signalling molecules  Activate other enzymes  C

A catalyst: substance which speeds up the rate of a reaction without itself undergoing permanent change.  Enzymes  Globular proteins Increase the rate of reaction  Enzyme-substrate complex  Lock and key theory  The substrate molecule is held within the active site by bonds that temporarily form between the R groups of the amino acids of active site and substrate molecules  Induced fit mechanism  Substrate shape is not exactly complementary to the shape of the active site  Active site changes its shape slightly when substrate binds  This allows them to fit better  Forms enzyme-substrate complex  Products leave  Lysozyme is a natural defence against bacteria (peptidoglycan/ murein cell wall) that is found in tears, saliva  Activation energy  An enzyme requires lower activation energy compared to without enzyme  When a chemical reaction takes palce, bonds within the reactants are broken and new bonds are made to form products  Breaking bonds require

Molecular biology: The study of biological molecules  Metabolism: The sum total of all the biochemical reactions in the body  Catabolism - breaks down  Anabolism - synthesis of complex molecules Metabolism is complex but has an underlying simplicity Has a close relationship between the structure and their functions  The building blocks of life  Hydrogen, carbon, oxygen and nitrogen  Monomers - single repeating units that are joined to form polymer  Macromolecules - giant molecule made from many repeating units.  Types of reaction:  Condensation - Removal of water  Hydration - Addition of water  Polysaccharides - food storage/ structural purposes Nucleic acid and proteins are informational molecules  Monomers Polymers Monosaccharides Polysaccharides Amino acids Proteins Glycerol & fatty acids Lipids Nucleotides Nucleic acid Carbohydrates (CHO)  Monosaccharides (glucose, galactose, fructose)  Sweet-tasting  Sing

Cell - Fundamental unit of all living things. Microscope: Light Microscope (LM) → μm  200 nm or further apart  Electron microscope (EM) → nm Close together as 0.1 nm  Why use electrons?  Wavelength is extremely short  Negatively charged, so it can be focused easily using electromagnets  Disadvantages of EM:  Specimen must be dead - viewed in a vacuum, water in the cells boil away so spciment must have all water removed  Expensive to buy and run Preparation of material is time consuming and requries expert trainings  Magnificaton  I = AM  Max resolution: 200nm, an objects closer than 0.2μm appear as a single item  Magnification ↑ Size of image ↑, but does not always increase the resolution  Resolution is the ability to distinguish two separate points  Resolution ↑ clearer and precise image is produced  Determined by wavelength of rays that are being used to view the specimen Max resolution: ½ * 400 = 200 nm The electroma