Biology 1.1 chemical elements and biological compounds

biological molecules

based on a small number of chemical elements and frequently consists of monomers combined into polymers

the 3 types of carbohydrates

monosaccharides, disaccharides and polysaccharides

monosaccharides

a sweet and soluble single sugar unit with a general formula of Cn(H₂O)_n, are reducing sugars

isomers

same molecular formula but different structural formula

5 reducing sugars

glucose, galactose, fructose, maltose and lactose

alpha glucose

O-H group on the bottom right, e.g. starch or glucose

beta glucose

O-H group on the top right, e.g. cellulose

how is maltose formed?

when 2 alpha glucose molecules undergo a condensation reaction and form glycosidic bonds between the 2 molecules

what is lactose formed by

the bonding of glucose and galactose

Sucrose

a non-reducing sugar produced from glucose and fructose, transport in phloem

hydrolysis

breaking down a chemical compound

amylose

a substance in starch, has an unbranching/linear chain with coiled springs. it has 1,4 alpha glycosidic bonds and is insoluble and compact

amylopectin

mostly made of 1-4 link but has some 1,6, branched but not coiled

glycogen

a compact storage molecule in animal tissues, branched and chemically similar to amylopectin but has more 1,6 bonds

cellulose

a beta glucose molecule which flips each module. it is unbranching and can easily link and unlink glucose particles from its structure

cellulose fibres

70 chains of beta glucose combine to form a microfibril, lots of microfibrils are held together to form fibres, these are incredibly strong- withstands turgid pressures

plant cell walls are…

rigidity and strong due to the incorporation of cellulose into their structure

Chitin

similar structure to cellulose with an (NHCOCH₃) molecule, forms a mucopolysaccharide, used in exoskeletons, strong, waterproof and lightweight

what kind of molecule is water?

a dipolar molecule, it is slightly negative as it has 2 positive hydrogen atoms and 1 negative oxygen element

what is calcium used for in living things

bone and teeth to strengthen them by hardening

what is phosphorus used for in living things

DNA and RNA, cell membranes and part of the phosphate groups in ATP

what is iron used for in living things

haem in haemoglobin and cytochromes

what is magnesium used for in living things

a component of chlorophyll

what do water molecules form

hydrogen bonds between the O of one molecule and the H of another as they are oppositely charged, they continually break and reform and are weak

cohesion

water molecules attract each other forming hydrogen bonds, forming a lattice. the sticking together of the molecules is called cohesion

why is cohesion useful

produces enough surface tension for small insects to walk on water

adhesion

water molecules are attracted and adhere to the walls of its container, the interaction between water molecules and different water molecules

why is adhesion useful

it attracts water molecules to the sides of xylem vessels, helping to support water as it moves up the vessel

why does water have a high specific heat capacity

it can absorb or lose a large amount of heat energy without a large change in temperature

why is a high specific heat capacity useful for water

helps to avoid fluctuations in the temperature of water and keep a stable aquatic habitat so that animals can maintain an internal temperature

why does water have ahigh latent heat of vaporisation

when water molecules evaporate they must break hydrogen bonds with other water molecules, this requires a relatively large amount of energy

why is it useful that water has a high latent heat capacity

heat is removed with the evaporated water so the surface it was on becomes cooler

why is water being dense useful

when water becomes ice, it expands and so ice is less dense that water, this can provide isolation and warmth for animals in a frozen river

solvent properties

water will dissolve any molecule that is polar, this is because a solute with slightly positive and negative poles interacts with water molecules

hydrophyllic

substances dissolve well

hydrophobic

substances do not dissolve well

buoyancy

the balance of the downward force of gravity and the upward pressure exerted by the fluid belowt

transmission of light in water

water is colourless and is therefore transparent to light, this means that sunlight can reach the cells and pass through them

what are fat and oil molecules made out of

fatty acids and glycerol

what are phospholipids made out of

fatty acids, glycerol and phosphorus

what reaction takes place when triglycerides are formed

condensation reaction, forming an ester bond between the oxygen on the glycerol group and the carbon on the fatty acid group, water is a biproduct

saturated fatty acid

only contains C-C single bonds, e.g. palmitic acid. usually solid

unsaturated acid

one C=C bond means its monounsaturated, more than one means its polyunsaturated. usually a liquid and has a kink e.g. linoleic acid

some functions of lipids

energy reserves, protection, thermal insulator

are phospholipids hydrophilic or hydrophobic

the fatty acid group is non polar and hydrophobic. the phosphate group is polar and hydrophilic

phospholipid bilayer

when the hydrophilic head of the phospholipid faces out and the hydrophobic tail faces in

what are phospholipids important for

electrical insulation of the myelin sheath around neurones

lipids emulsion test

when shaken with ethanol, lipids with produce a clear solution. add that on top of cold water and a white precipitate forms

lipoprotein

lipids are transported in the blood association with proteins

are lipoproteins associated with coronary heart disease

higher ratios of lower density lipoproteins are associated with a higher incidence of heart disease while high density lipoproteins are not

are saturated or unsaturated fats correlated to higher levels of circulating LDL

high intake in saturated fats may contribute to higher levels of heart disease

hydrophobic R group

form hydrophobic bonds with each other or with other hydrophobic compounds

polar R group

form hydrogen bonds, weak bonds broken by high temperatures

charged R groups

form ionic bonds, bonds broken by changes in pH

contain sulphur

form bonds called disulphide bridges which are covalent and strong

the peptide bond

amino acids join by a condensation reaction, a molecule of water is released

protein food test

add biuret’s solution to the solution and shake well, in the presence of proteins it will turn from blue-black to purple

primary structure of a protein

type, number and sequence of amino acid determined by the sequence of bases in the gene

secondary structure of a protein

polar peptide bond, can form H bonds with other peptide bonds to make alpha or beta structures

alpha helix structure

chain coils up, H bonds form between polar peptide bonds separated by four amino acid residues

beta pleated sheet structure

the chain turns back on itself, held by H bonds between peptide bonds

tertiary structure of a protein

bonds form between the R group , the whole structure folds up to form a very specific 3D shape, this is vital for function

quaternary structure of a protein

more then one polypeptide chain are needed to make a functional protein, similar bonds to a tertiary structure, can be associated with non-protein groups to make large and complex molecules

globular proteins

the protein folds into a compact shape that is vital for function

fibrous proteins

usually insoluble in water and are not easily denatured

keratin

a fibrous protein found in hair and feathers, insoluble in water

colagen

alpha helixes linked into strands. very important in the extra cellular matrix

role of polar and non-polar amino acids

controlling the position of proteins in membranes, creating hydrophilic channels through membranes and the specificity of active sites in enzymes