BIOLOGICAL MOLECULES

BYMR SAMMYBio Teacher

Cellulose

Cellulose straight, long, unbranched chains form H-bonds, with adjacent chains monomer: ß-glucose; 2 ß-glucose molecules condense together forming 1,4 glycosidic bonds; alternate molecules (2nd, 4th, 6th, etc) are rotated through 180o allowing appropriate –OH groups to react function: structure and support in cell walls of plant cells

LIPIDS organic compounds whose molecules contain atoms of C, H and O only; ratio of H to O is always greater than 2:1 insoluble in water examples: fats and oils (triglyceride), waxes (insects’ chitin exoskeletons & leaves of plants), steroids (oestrogen and testosterone), phospholipids (including cholesterol)

LIPIDS triglyceride structure

LIPIDS triglyceride structure

LIPIDS phospholipid structure

LIPIDS phospholipid structure

LIPIDS functions: high energy stores: 1 g of lipid over 2x as much energy as 1 g CHO/Protein waterproof coverings (bird’s feather; bouyancy) insulation: poor conductor of heat shock-absorbing layers: compressible; protects delicate organs like kidney and heart

LIPIDS functions: major components of cell surface membrane: phospholipids , cholesterol

PROTEINS organic compounds consisting of C, H, O, N and (sometimes) Smonomer: amino acids

PROTEINSAmino acids are joined together by peptide bonds. The reaction involves the formation of water molecule: condensation polymerisation reaction:

LEVELS OF PROTEIN STRUCTURE Primary Structure• literally the order or sequence of amino acids in the protein/polypeptide.Order is determined by the base sequences in DNA

LEVELS OF PROTEIN STRUCTURE Secondary Structure• Secondary structure is the coiling or folding of the polypeptide chain•Hydrogen bonds form between :oxygen of a C=O of one amino acid hydrogen of a N-H of another amino acid four places ahead of it in the polypeptidecauses the polypeptide to coil into α helix which is stabilised by the hydrogen bonds

LEVELS OF PROTEIN STRUCTURE Secondary Structure•

LEVELS OF PROTEIN STRUCTURE Secondary Structure• Sometimes a polypeptide might fold into a much looser shape called a β pleated sheet •shape is stabilised by hydrogen bonding

Adjacent portions of different polypeptide chains (if formed in opposite directions to each other, H-bonds form the –CO gr of 1 chain and –NH gr of neighbouring chains

LEVELS OF PROTEIN STRUCTURE Tertiary Structure• Note: •hydrogen bonds are weak •easily brokenhigh temperatures pH changes both cause breakage of hydrogen bonds affect the shape and functioning of a protein•permanent change results in denaturation

LEVELS OF PROTEIN STRUCTURE Tertiary Structure• the final 3D structure of a protein• shaping of the secondary structure due to bonds formed bet. parts of the R-groups of the chains

LEVELS OF PROTEIN STRUCTURE Tertiary Structure• held together by 4 diff. bonds and interaction1)Disulphide bond – strong double bond (S=S) formed between the Sulphur atoms between cysteine amino acids2) Ionic bond – formed between 2 oppositely charged R groups of amino acid

LEVELS OF PROTEIN STRUCTURE Tertiary Structure• held together by 4 diff. bonds and interaction3)Hydrogen bond4) Hydrophobic and Hydrophilic Interactions – amino acids: hydrophobic or hydrophilic- globular protein orientates itself inward or towards its centre (hydrophobic) and towards its edges (hydrophobic)

LEVELS OF PROTEIN STRUCTURE Tertiary Structure• can be broken down by the action of heat- Increased KE of protein = vibrate=weak bonds like H-bond and ionic bond which maintain the shape of protein break=DENATURATION

TYPES OF PROTEIN WITH 3D STRUCTURE Globular Protein• forms ball-like structure: hydrophobic part –towards the centre; hydrophilic- towards the edges• water-soluble

TYPES OF PROTEIN WITH 3D STRUCTURE Fibrous Protein• forms long fibres and mostly consists of repeated sequences of amino acids• insoluble in water

LEVELS OF PROTEIN STRUCTURE QUATERNARY STRUCTURE • made up of two or more polypeptide chains• sometimes with an inorganic component called prosthetic group• examples: Hb, collagen

haemoglobin water soluble globular protein composition: 2 ɑ polypeptide chains and 2 ß polypeptide chain prosthetic group: haem function: ?

collagen fibrous protein consisting of 3 polypeptide chains H-bonds form between chains around 1000 amino acids in length structural protein functions: form the structure of bones; makes up cartilage and connective tissues; prevents arteries from bursting; main component of tendon