biology from notes

• Monomers are small repeating units which polymers are made from. Examples include monosaccharides and amino acids.

  Polymers are large molecule made from multiple monomers
• Condensation: Joins two molecules together releasing water

  Hydrolysis: Breaks bond between molecules using water
• 3 types of monosaccharides:

  1. Glucose
  2. Galactose
  3. Fructose
• 3 types of disaccharides:

  1. Maltose (glucose + glucose)
  2. Sucrose (glucose + fructose)
  3. Lactose (glucose + galactose)
• The 3 polysaccharides:

  1. Glycogen
  2. Starch
  3. Cellulose
• Glycogen:

  • alpha glucose
  • used as an energy storage in animals
  • coiled, branched and compact
  • insoluble so doesn't affect water potential
  • contains 1,4 and 1,6 glycosidic bonds
• Starch:

  • alpha glucose
  • 1,4 and 1,6 glycosidic bonds
  • insoluble so doesn't affect water potential
  • helical and compact
  • large molecule so cannot leave the cell
  • amylose => unbranched and coiled (1,4)
  • amylopectin => branched and both bonds
• Cellulose:

  • beta glucose
  • 1,4 glycosidic bonds
  • long parallel straight chains
  • linked by hydrogen bonding to form macrofibrils
  • provides strength to cell wall
• Lipids examples:

  • triglycerides and phospolipids
• Triglycerides:

  • formed from a condensation reaction between one glycerol and three fatty acids
  • ester bonds
  • R group of fatty acids may be saturated (single bond) or unsaturated (double bond)
  • Energy storage due to large ratio carbon-hydrogen bonds
  • Metabolic water source as releases water if oxidised due to hydrogen:oxygen
  • Hydrophobic so doesn't affect water potential
• Phospholipids:

  • Made of 2 fatty acids and one phosphate
  • Hydrophyllic head and hydrophobic tail
  • Used in cell surface membrane
  • Insoluble in water
• What is the test for lipids?

  Emulsion test: Mix sample in ethanol, add water and a white emulsion should form
• Amino acids:

  • monomers of proteins
  • amino acids only differ in their side chain / R group
  • peptide bond forms between amine group and carboxyl group

  
• Describe the structure of proteins?

  1.Amino acids are joined by peptide bonds through condensation

  2. Primary structure is the specific sequence of amino acids

  3. Secondary structure is the folding of the polypeptide chain due to hydrogen bonding (beta pleated or alpha helix)

  4. Tertiary structure is 3D folding due to hydrogen, ionic bonds and disulfide bridges

  5. Quaternary structure is 2 or more polypeptide chains
• What is the test for proteins?

  Biuret test: add biuret solution and shake, a positive test will turn from light blue to lilac
• What is an enzyme?

  a protein that catalyses a reaction by lowering the activation energy
• globular proteins: compact and water soluble (enzymes/metabolic reactions)

  fibrous proteins: long, insoluble and useful for structure
• Factors affecting rate of reaction catalysed by enzymes:

  1. pH
  2. temperature
  3. enzyme and substrate concentration
• Competitive inhibition:

  • inhibitor similar shape to substrate so binds to active site
  • inhibition can be overcome by adding more substrate
• Non-competitive inhibitors:

  • Inhibitors bind to enzyme on allosteric site which changes shape of active site
  • cannot be overcome
• DNA and RNA are polymers of nucleotides.

  Nucleotide structure:

  A) phosphate group

  B) pentose sugar

  C) nitrogenous base

  
• Semi-conservative replication:

  1. Helicase unwinds double helix by breaking weak hydrogen bonds
  2. Each strand is used as a template
  3. New DNA nucleotides are attracted to exposed bases on parent strand
  4. DNA polymerase joins adjacent nucleotides by condensation by forming phosphodiester bonds
• ATP:

  • structure : adenine, ribose and 3 phosphate groups
  • releases small amounts of energy instantaneously
  • phosphorylates other compounds to make them more reactive
  • rapidly resynthesised
  • not lost from cells
• Describe the 5 properties of water:

  1. Metabolite => in condensation/hydrolysis reactions
  2. Solvent => allows transport of substances
  3. High SHC => buffers changes in temperature
  4. Large latent heat of vaporisation => provides cooling effect through evaporation
  5. Cohesion between molecules => supports columns of water in plants
• What does the immune system detect?


  Pathogens, abnormal body cells, cells from other organisms and toxins
• Antigens: proteins found on surface of cells which signals to immune system if it is non-self
• Phagocytosis:

  1. Debris released by pathogen is detected by phagocyte
  2. Phagocyte changes shape and engulfs pathogen
  3. Pathogen contained in phagosome vesicle
  4. Lysosome fuses with vesicle; releasing enzymes which hydrolyses it
  5. Antigens on pathogen displayed on cell membrane
• Describe the cell mediated response?

  Helper T cells receptors attach to antigens on APC

  T cells divide by mitosis

  Clones differentiate into helper T cells, cytotoxic and memory T cells

  Cytotoxic cells release perforin, which makes pores in the cell membrane so water moves in and the cell bursts
• Describe the Humoral response


  B cell binds to complementary antigen and engulfs it (endocytosis) and presents antigen on cell surface

  Complementary T cell binds to B cell

  B cell goes through clonal expansion to produce plasma and memory cells

  Plasma cells produce antibodies

  Antibodies clump together cells through agglutination to form antigen-antibody complexes

  This makes it easier for phagocytes to detect
• How many polypeptide chains are antibodies made of?

  4
• Antibodies have 2 binding sites so they can clump cells together
• Antibodies have strong disulfide bridge to hold polypeptides together and hinge region so it can bend
• Antibody structure:

  • Heavy and light chains
  • constant region and variable region

  
• What is the function of the golgi?


  Packages and modifies proteins
• Active immunity:

  Body produces it's own antibodies so long term
• What is a mutation?


  Change in the base sequence of DNA which occurs spontaneously during DNA replication
• What are the types of mutations?


  Addition, Deletion and substitution
• Not all substitution mutations result in a change of amino acids as genetic code is degenerate
• Mutations in number of chromosomes arises by chromosome dysjunction during meiosis so chromosomes don't separate properly
• Meiosis:

  • produces 4 genetically different cells
  • haploid
  • number of chromosome combos is 2 to the power of n
  • split into 2 divisions