Biological molecules Flashcards
7 properties of water
-Liquid- water molecules constantly move and therefore constantly make and break hydrogen bonds. These hydrogen bonds prevent water molecules evaporating into a gas providing habitats, forming major component of tissues, effective transport medium etc.
-Density- ice is less dense then water due to hydrogen bonds forming an open lattice when water is frozen. Is more dense up until 4 degrees, then from there until freezing its less dense than water. This layer of ice offers insulation for the water underneath reducing heat loss from the pond
-Solvent- water is polar, with positive and negative ends. Therefore are attracted to positive and negative ions. Water molecules surround the solute, dissolving it
-Cohesion + surface tension- Hydrogen bonding pulls the water molecules together= cohesion. Water molecules more attracted to water beneath than air, meaning water surfaces can resist a force applied to it allowing pond skaters to walk on water
-High specific heat capacity- lots pf energy needed to change the temp of water due to hydrogen bonds, providing a stable habitat.
-High latent heat of vaporisation- lots of energy needed for water to evaporate due to hydrogen bonds
-Reactant- important in photosynthesis and digestion
Monosaccharide
-simplest carbohydrate
-soluble in water
-insoluble in non-polar solvents
-different isomers eg alpha and beta glucose
Disaccharide formation equations
A glucose + A glucose = maltose
A glucose + fructose= sucrose
B galactose + A glucose= lactose
B glucose + B glucose= cellobiose
A glucose
H,H,OH,H
-component of glycogen + starch (energy store)
B glucose
OH,H,OH,H
-component of cellulose (structural support)
Why polysaccharides are good energy stores
-compact, don’t occupy a large space
-glucose molecules in chains so can be easily snipped off when required
-less soluble in water than monosaccharides, therefore doesn’t alter water potential in cytoplasm
Amylose- starch in plants
-unbranched (1-4 glycosidic)
-chain A glucose molecules
-coil held with hydrogen bonds
-hydroxyl groups on carbon 2 are inside the coil making it less soluble + allow hydrogen bonds to form
Amylopectin- starch in plants
-branched (1-4, 1-6 glycosidic bonds)
-coil held with hydrogen bonds
-branches emerge from the spiral
-A glucose
Glycogen- animals
-branches (1-4,1-6 glycosidic bonds)
-smaller chains so less likely to coil
-more branches so can snip of monosaccharides for quick release of energy
-A glucose
Cellulose- polysaccharide
-B glucose molecules form through condensation reactions, forming glycosidic bonds
-every other B glucose molecule is rotated 180 prevents spiralling
-hydrogen bonding between rotated B glucose molecules also prevents spiralling
-hydrogen bonding between chains gives structural strength
-60-70 chains bundle to form microfibrils
-400 microfibrils bundle to form macrofibrils
Structure and function of plant cell walls
-macrofibrils have high tensile strength because of glycosidic and hydrogen bonds
-criss cross for extra strength
-difficult to digest because of glycosidic bonds, most animals don’t have correct enzyme to digest
-space between macrofibrils for water and mineral ions making cell wall fully permeable
-reinforced with other substances eg. cutin + suberin (waxes that fill gaps for waterproofing), lignin
Other structural polysaccharides
-bacterial cell walls- peptidoglycan, long parallel polypeptide chains criss-crossed by shorter chains
-exoskeleton- chitin, cross links between parallel chains of acetylglucosamine
Lipids
-insoluble in water
-not polar
-dissolve in alcohol
-important lipids are triglycerides, phospholipids and steroids
-examples of macromolecules
Triglyceride structure
-3 fatty acids, 1 glycerol
-glycerols has 3 OH groups
-Fatty acids have COOH on one end, saturated no double bonds
Ester bond
-condensation reaction between COOH of fatty acid and OH of glycerol
-glycerol has 3 OHs so 3 fatty acids bond
