Biology 2.1.2- Biological molecules

• What is the structure of an amino acid

  Amino group , Carboxyl group , Residual group (changes between amino acids)
• What are proteins made of

  carbon, hydrogen, oxygen, nitrogen, sulphur (CHONS)
• Describe the formation of a dipeptide molecule

  When an OH group from a carboxyl group and the hydrogen from an amine group bond to create a water molecule.

  A peptide bond is formed between amino acids (C-N)
• Describe the primary structure of proteins and its bonds

  The sequence of amino acids in a polypeptide. Held together by peptide bonds
• Describe the secondary structure of proteins and its bonds

  The way the polypeptide folds to form alpha helices and/or beta pleated sheets. Held together by peptide bonds and hydrogen bonds

  
• Describe the tertiary structure of proteins and its bonds

  Further folding of the polypeptide to form its 3D shape. Held together by hydrogen bonds, ionic bonds, hydrophobic and hydrophilic interactions and disulfide bridges.
• Describe the quaternary structure of proteins and its bonds

  The way that more than one polypeptide interacts / bonds to form a protein (and sometimes non-protein components). Held together by hydrogen bonds, ionic bonds, hydrophobic and hydrophilic interactions and disulfide bridges.
• Features of a structural protein

  Fibrous

  Insoluble in water

  Repeated subunits (amino acids)
• Features of a functional protein

  Globular

  Water soluble

  Non-repeated amino acid sequence
• Describe the structure of haemoglobin

  Red, oxygen carrying pigment

  Made from four polypeptides

  Each subunit contains a prosthetic haem group which binds to oxygen

  Quaternary structure
• Describe the structure of insulin

  Hormone secreted by the pancreas and helps regulate blood-glucose level

  Transported in the blood (soluble)

  Consists of two polypeptide chains, held together by disulfide bonds

  Quaternary structure
• Describe the structure of amylase

  Enzyme that catalyses the breakdown of starch

  Made of single chain amino acids

  Contains both alpha-helix and beta pleated sheets

  Tertiary structure
• Describe the structure of collagen

  Found in animal connective tissue

  Very strong but flexible molecule

  Minerals can bind to the protein to increase its rigidity

  Quaternary structure
• Describe the structure of elastin

  Found in elastic connective tissue

  Its elastic so allows tissues to return to their original shape after being stretched

  Quaternary structure
• Describe the structure of keratin

  Found in many of the external structures of animals

  Can either be flexible (like hair) or hard and tough (like nails)

  Quaternary structure
• What elements make up lipids

  carbon, hydrogen, oxygen (+phosphorus for pospholipids)
• Describe the structure of triglyceride

  One glycerol and three fatty acid chains. 3 ester bonds
• What is esterification and how does it happen

  Formation of ester bonds between fatty acid and glycerol molecule. H of carboxyl group joins with OH of glycerol molecule
• How do you identify a lipid, using elements

  Lipids have a higher proportion of Hydrogen / Carbon compared to oxygen
• Describe the structure of phospholipids

  Hydrophilic phosphate head, Glycerol, 2 hydrophobic fatty acid chains. 2 ester bonds
• Describe the structure of cholesterol

  4 'c' ring structure

  Hydrophilic OH group at one end
• What are functions of lipids

  Energy store

  Insulation

  Protection of organs

  Buoyancy (aquatic mammals)

  Components of membranes

  Formation of hormones / vitamin D
• Whats the difference between alpha-glucose and beta-glucose

  The OH (hydroxyl) group on carbon 1 is in opposite positions

  
• Whats the difference between hexose monosaccharide and pentose monosaccharide

  Hexose monosaccharides have six carbon atoms and pentose only have five carbon atoms
• What happens to form glycosidic bonds

  Two hydrogen and an oxygen atom are removed from the glucose monomers and form a water molecule

  A bond forms between carbons 1 and 4 to join the molecules

  A covalent bond called a glycosidic bond is formed (1,4 glycosidic bond)
• How is glucose released for respiration

  Starch or glycogen undergo hydrolysis reactions requiring addition of water molecules