1. Biological Molecules

• Carbohydrates

  monomers: Monosaccharide

  e.g: glucose, galactose, fructose

  General formula: (CH2O)n
• Disaccharide is a sugar formed by the condensation of two monosaccharides joined via glycosidic bonds

  E.g: Maltose, lactose, sucrose
• Polysaccharide is many monosaccharides joined together by glycosidic bonds
• Alpha glucose, used in macromolecules, energy store (glycogen and starch)

  1ºC = H
• How are antibodies made?

  1. Vaccine contains antigen from pathogen/weakened form of pathogen

  2. Phagocyte presents antigen on its cell membrane ;

  3. T cell with complementary receptor protein binds to antigen;

  4. T cell stimulates B cell;

  5. (With) complementary antibody on its surface;

  6. B cell secretes large amounts of antibody;

  7. B cell divides to form clone all secreting / producing same antibody.
• Define a monomer

  A small molecule which reacts with similar molecules to produce a larger dimer/polymer
• Name commonly occurIng monosaccharides

  Glucose (alpha & beta), fructose and galactose
• Name the monosaccharides used to form a molecule (disaccharide ) of

  i) Maltose

  ii) Lactose

  iii) sucrose

  i) Glucose + Glucose

  ii) Glucose + Galactose

  iii) Glucose + Fructose
• Describe test for reducing sugar

  Mix sample with an equal volume Benedict's reagent, heat gently.

  Colour change = blue——>brick red
• Explain how to obtain a positive test for a non - reducing sugar

  Test with Benedict’s Reagent, Heat sample with HCL, neutralise it with sodium hydrogencarbonate, retest using Benedict's reagent
• 4 chemical groups attached to the central carbon of an amino acid are....

  Amino group (-NH3)

  Carboxylate group (-COOH)

  R-group

  Hydrogen atom (-H)
• What makes a amino acid different to each other is....

  Their R-groups
• Monomers and type of bonds in carbohydrates

  Monomer : monosaccharides

  Type of bond formed : glycosidic
• Monomers and type of bonds in lipid

  Monomer : glycerol and fatty acid

  Type of bond formed : ester
• Monomers and type of bonds in protein

  Monomer : amino acids

  Type of bond formed : peptide
• Biuret solution ....

  Used to test for presence of proteins and is made up of NaOH and dilute Cu sulphate solution
• What is the basic monomer unit in a carbohydrate

  A monosaccharide
• What is a disaccharide molecule made up of

  Two monosaccharides held together by a glycosidic bond due to a condensation reaction
• What do properties of polysaccharides depend on

  The arrangement of monomers in their structure
• What is a reducing sugar

  Carbohydrates which can donate electrons to another chemical
• What are examples of reducing sugars

  All monosaccharides maltose and lactose
• What substance is used to test for the presence of a reducing sugar

  Benedicts reagent and alkaline solution containing copper (II) sulphate
• What is the positive test for a reducing sugar

  Change from blue to a brick red solution this is because a precipitate of copper one oxide forms
• Proteins can be classed as either...

  Fibrous Or globular
• Lipid test

  Shake sample with ethanol, then add water

  Positive test: milky emulsion

  Negative: colourless solution
• Test for starch: Add iodine dissolved in potassium iodide to the sample.

  Positive test: Orange brown to blue black
• Structure of starch related to its function 

  Helical makes starch very compact.

  Large and insoluble so osmotically inactive 

  Branched so more enzymes can attach to the ends and glucose is easily released for respiration
• Structure of cellulose related to its function

  Long, straight/unbranched chains of beta glucose 

  Joined by hydrogen bonding 

  To form microfibrils 

  Provides rigidity/strength
• Structure of glycogen related to its function

  -Branched; can be rapidly hydrolysed to release glucose for respiration to provide energy

  -Large polysaccharide molecule; can't leave cell

  -Insoluble in water; water potential of cell not affected i.e. no osmotic effect
• Why are lipids insoluble in water?

  Lipids are non-polar whilst water is a polar solvent so lipids will not dissolve in water
• Why are unsaturated fats liquid at room temperature but saturated fats are solid at room temperature

  Unsaturated fats have bend/kinks in their structure this presents them packing closely together as a result the intermolecular forces between the molecules are weaker
• Identify the three broad uses of triglycerides:

  Waterproofing

  Thermal insulation

  Protection/shock absorption

  Source of energy
• What is emulsion ?

  A dispersion of droplets of one liquid in another liquid in which it won't dissolve
• 1st level of protein structure is....

  The primary structure - sequence of amino acids in the polypeptide chain
• 2nd level of protein structure

  secondary structure is folding of polypeptide chain due to hydrogen bonding

  This can form a alpha helix or beta pleated sheet.
• 3rd level of protein structure

  tertiary structure- 3D shape of the polypeptide chain due to ionic bonding, disulphide bridging or hydrogen bonding between R-groups causing it to fold.
• 4th level of protein structure

  Quaternary structure - multiple polypeptide chains chemically bonded together
• Characteristics and uses of globular proteins

  Rounded/spherical because of irregular polypeptide chains which causes fewer cross-linkages.

  Soluble in water because of large number of polar chains.

  Have less bonds/cross linkages so is less stable and easier to break.

  Used in metabolism because of rounded shape.
• Characteristics and uses of fibrous proteins

  Long narrow shape due to many cross linkages between polypeptide chains, meaning the polypeptides can be held close to each other, making them useful in providing strength and structure.

  Insoluble in water because of large numbers of non-polar side chains.
• What is a calibration curve?

  A series of known concentrations to be used as a comparison to identify or estimate a unknown concentration.