Created by beccy.booster over 4 years ago
Biological Molecules IntroMetabolism- The chemical processes that occur within a living organism in order to maintain life.The sum of all chemical reactions.Anabolic reactions- Build new molecules or store energy. generally refers to combining simpler substances into more complex ones, using energy.Monomers and polymers- Monomers are small molecules that are joined together in various patterns to form specific natural or synthetic macromolecules (polymers) Alpha and Beta glucose- The monosaccharide glucose exists as 2 isomers of which only the D-glucose is biologically active. D glucose also has two forms- alpha and beta. In alpha glucose the OH on C1 points down and in beta, points up. Two alpha glucose molecules joined are called maltose and, if more are joined, it is known as amylose. Amylose can be made of many thousands of glucose molecules bonded together and coils into a compact spring (these springs are why iodine turns black).Alpha glucose can also form starch which consists of coils of amylose and branched chain amylopectin (this is stored in chloroplasts and starch grains). Glycogen is another storage molecule (animal starch) made from alpha glucose. It contains more 1-6 branches than starch and has shorter 1-4 glucose chains so is more compact and forms granules in the liver. Beta glucose forms cellulose, a long, straight chain molecule that does not compact into springs. Cellulose chains are stronger than amylose and form H bonds due to the straight nature of the molecule. 60-70 cellulose molecules become cross linked with H bonds to form microfibril bundles and groups of these form macrofibrils. the macrofibrils are embedded in a polysaccharide 'glue' of pectins and this forms the cell wall of plants.
LipidsFunctions-Energy source -Energy storage (adipose cells)-Cell surface membranes-Insulation (whale blubber)-Protection (waxy cuticles)-Some hormones All energy storage fats/oils contain glycerol and different fatty acids (some of which - essential fatty acids- must be taken in by the body as they cannot be made). All lipids have the same glycerol molecule but fatty acids can vary, they: -Consist of an acid group and hydrocarbon chain (2-20 Cs long)-Can have an unsat or sat C-H chain; unsat fatty acids will be more fluid as molecules push apart (oils contain unsat acids whilst solid fats are sat) Types of lipid:1) Triglycerides 1 glycerol and 3 fatty acids Condensation reaction forms ester bond Insoluble in water 2) PhospholipidsStructure very similar to triglycerides but only 2 fatty acids; the 3rd OH group joins to a hydrophilic phosphate 'head' insteadWhen surrounded by water, forms a bilayer that is the basis of plasma membranes in cellsSince phospholipids contain fatty acid tails they can be saturated or unsaturated- this controls the fluidity of the membranes and allows animals to adapt (animals in cold climates will have more unsaturated fatty acids in their membrane to keep it moving)3) Cholesterol Made from 4 carbon based ringsFits in between phospholipids in membranes and provides mechanical stability 4)Cholesterol based hormonesTestosterone, oestrogen and vitamin D are all steroid hormones made from cholesterol They can pass straight through the bilayer as well as the nuclear envelope and bind to their target receptor site (often in the nucleus) Note: Cholesterol can form gallstones in bile and cause atherosclerosis in blood vessels. FHC is a cholesterol related genetic disease that causes strokes and mycardial infarctions; people do not have the receptor that binds to the protein that controls cholesterol in the blood so keep making more.The respiration of lipids- Ester bond is broken in hydrolysis reaction (CO2, water and 'energy' released). Long term, lipids can be stored in cells without affecting water potential for respiration at another time (e.g. camels store fat to release water).
Carbohydrates Function: Energy storage, structure (cellulose cell walls), energy source for respirationCan form: Nucleic acids, glycolipids/proteinsMade from: Monosaccharides (like glucose) joining together in condensation reaction to form glycosidic bondAre all: soluble in water, able to form crystals, sweet tastingOther examples: Chitin (forms yeast cell wall and insect exoskeleton) and peptidoglycan (forms cell wall of prokaryotes/bacteria).
Proteins- Amino acids join to make a dipeptide by a condensation reaction (forms peptide bond). Polypeptides form when more and more acids join. Note: The amino acids are described as 'residues' because part of the molecule is lost when they join.Primary structure- the sequence of amino acids specific to that proteinSecondary structure-the polypeptides spiral or fold into alpha helices or beta pleated sheetsTertiary structure- bonds/attractions form between the helices/sheets; these can include disulphide bridges, hydrogen bonds, ionic bonds and hydrophilic-phobic interactions. Each gives the protein its specific 3D shapeQuaternary structure- refers to proteins than contain more than one polypeptide chain; can be fibrous (like collagen) or globular (like haemoglobin).Heat: Heating a protein gives the molecules more kinetic energy which causes them to vibrate; vibrations can cause bonds to break and the 3D structure unravels. This 'denaturation' is irreversible and prevents the protein performing its function (as this is specific to its shape).