PAPER 1

• DIFFERENT MOLECULES ASSOCIATED WITH NUCLEOTIDES, NUCLEOTIDE DERIVATIVES, NUCLEIC ACIDS?

  • DNA
  • RNA (mRNA/ tRNA/ rRNA/ siRNA)
  • ATP
  • FAD/ NAD/ NADP
  • cAMP
• ANTIBIOTIC RESISTANCE?

  • allele codes for enzyme
  • breaks down antibiotic
  • bacteria asexually reproduce (binary fission)
  • all offspring are clones and have allele
  • so evolution is rapid
• KEY POINTS ABOUT ATP?

  • energy currency
  • ATP hydrolase
  • energy released in small packets
  • hydrolysis of ATP can be coupled to energy-requiring reactions
• WHAT IS TRANSLOCATION?

  transport of dissolved sucrose (or assimilates - sucrose/ AAs) from source to sink in phloem
• RATIOS OF EPISTASIS?

  9 : 3 : 4 (recessive epistasis) or 12 : 3 : 1 (dominant epistasis)
• TRIGLYCERIDE PROPERTIES?

  1. Energy source (large ratio of energy storing C-H bonds to C atoms)
  2. Metabolic water source (releases water if oxidised, high ratio of H to O atoms) so useful for desert animals
  3. Insoluble in water (large and hydrophobic/ non-polar)
  4. Relatively low mass (but high energy, not increase mass/ prevent movement)
• GLOBULAR PROTEINS?

  • round structures (hydrophobic fold inwards, hydrophilic arranged around external surface)
  • hydrophilic, water-soluble, polar
  • enzymes, transport proteins (haemoglobin), messenger proteins (hormones)
• FIBROUS PROTEINS?

  • long chains (long polypeptide chains twisted together)
  • hydrophobic, fat-soluble, non-polar
  • structural proteins (as stable and insoluble, so support and protect tissues, e.g. keratin/ collagen)
  • COLLAGEN: connective tissue, hydrogen bonding + covalent bonding so strong, provide support and tensile strength as present as fibres
• FUNCTION OF SER?

  synthesis and store of lipids and carbohydrates
• CELL WALLS?

  PLANT: cellulose

  BACTERIA: murein/ peptidoglycan

  FUNGI: chitin
• TEM VS SEM?

  TEM:

  • electron beam through sample produces 2D image
  • absorb
  • high resolution
  • vacuum
  • very thin samples

  SEM:

  • electrons are reflected producing 3D image
  • lower resolution
  • thick or thin samples
• BINARY FISSION?

  1. Replicate circular DNA and plasmids
  2. Cytoplasm divides
  3. Two daughter cells, single copy of DNA, variable number of plasmids
• CHOLESTEROL?

  • very hydrophobic
  • reduce water/ dissolved ion leakage
  • reduces lateral movement
  • less fluid at high temperatures
• TYPES OF SOLUTION?

  • ISOTONIC: water potential is same in solution and cell (no change, incipient plasmolysis)
  • HYPOTONIC SOLUTION: water potential of solution higher than water potential in cell (protoplast swells, turgid)
  • HYPERTONIC SOLUTION: water potential of solution lower than water potential in cell (protoplast shrinks, plasmolysis)
• CELL MEDIATED IMMUNITY?

  1. APCs
  2. Receptors on specific T helper cells attach
  3. T helper cells divides by mitosis and clones
  4. Releases cytokines
  5. Cytokines trigger release of T cytotoxic cells, T helper cells (B cells, phagocytes), T memory cells
• HUMORAL IMMUNITY?

  1. B cell accepts antigen and presents on cell-surface membrane
  2. Complementary T helper cells attach and activate B cells
  3. B cells divide by mitosis and clone
  4. Differentiate into plasma cells
  5. Secrete specific antibodies
  6. Memory cells (clonal selection, clonal expansion)
• PULMONARY VENTILATION?

  total volume of air moved into lungs during one minute

  -> tidal volume x ventilation rate
• FICK'S LAW?

  diffusion ∝ (SA x difference in concentration) / diffusion pathway length
• TYPES OF PEPTIDASES?

  ENDOPEPTIDASES: middle of polymer

  EXOPEPTIDASES: ends of polymer

  MEMBRANE-BOUND DIPEPTIDASES: two amino acids
• LIPID ABSORPTION?

  1. Liver produces bile
  2. Emulsifies large lipid droplets into smaller lipid droplets (larger SA)
  3. Hydrolysed by lipase and water = FAs + MGs
  4. Combine with bile salts = micelles
  5. Release FAs + MGs at epithelial cells
  6. Enter cell by simple diffusion
  7. FAs + MGs recombine in SER = TGs
  8. Combine with cholesterol + lipoproteins at Golgi Apparatus = chylomicrons
  9. Exit cell by exocytosis
  10. Chylomicrons enter lacteals, eventually reaches bloodstream
  11. TGs hydrolysed by enzymes in capillary endothelium = FAs + glycerol
  12. Diffuse into cells
• WHAT DO MICELLES CONSIST OF?

  fatty acids, monoglycerides, bile salts
• WHAT DO CHYLOMICRONS CONSIST OF?

  triglyceride, cholesterol, lipoproteins
• WHAT DO MICELLES DO?

  • increase solubility of fatty acids in water
  • carry fatty acids to epithelial cell
  • maintain higher concentration of fatty acids compared to epithelial cell
• WHAT TYPE OF PROTEIN IS HAEMOGLOBIN?

  globular so soluble in water
• OXYGEN DISSOCIATION CURVES?

  SHIFTS RIGHT (Bohr Effect)

  • high CO2 concentration
  • affinity for oxygen decreases
  • unloads more oxygen

  SHIFTS LEFT

  • low CO2 concentration
  • affinity for oxygen increases
  • loads more oxygen
• ADAPTIONS OF HAEMOGLOBIN?

  HUMAN FETUS

  • myoglobin
  • higher affinity for oxygen (left)
  • loads more oxygen in the placenta (low partial pressure of oxygen)

  LLAMA

  • higher affinity for oxygen (left)
  • higher altitudes (low partial pressure of oxygen)

  DOVE

  • lower affinity for oxygen (right)
  • faster metabolism, flying, muscle contractions

  EARTHWORM

  • very high affinity for oxygen (left)
  • underground (low partial pressure of oxygen)
• WHY DOES BLOOD FLOW THROUGH THE LUNGS AT A LOWER PRESSURE?

  • prevents capillary damage in alveoli
  • reduces speed of blood flow, more time for gas exchange
• CHARACTERISTICS OF CARDIAC MUSCLE?

  • myogenic (contract/ relax without nervous/ hormonal stimulation)
  • never fatigues but requires constant oxygen supply
• WHY DOES BLOOD NEED TO BE A LOWER PRESSURE IN THE RIGHT VENTRICLE?

  • prevent capillary damage
  • slow blood flow
  • more time for gas exchange
• PURPOSE OF THE SEPTUM?

  separates oxygenated and deoxygenated blood to maintain a concentration gradient
• PURPOSE OF ADAPTIONS OF BLOOD VESSELS?

  ARTERY

  • thick muscle layer for constriction/ dilation to control volume of blood, prevent bursting
  • thick elastic layer to maintain blood pressure by stretching/ recoiling

  CAPILLARIES

  • narrow diameter, slows blood flow, squashes RBCs against walls to maximise diffusion

  ARTERIOLES

  • thicker muscle layer than arteries to restrict blood flow into capillaries
  • thinner elastic layer than arteries due to lower pressure
• CARDIAC CYCLE?

  DIASTOLE

  • atria and ventricles are relaxed
  • blood enters atria via vena cava and pulmonary vein
  • increasing pressure in atria
  • semi-lunar valves close

  ATRIAL SYSTOLE

  • atria contract, ventricles are relaxed
  • increasing pressure in atria
  • atrioventricular valves open
  • blood enters ventricles

  VENTRICULAR SYSTOLE

  • ventricles contract, atria relax
  • increasing pressure in ventricles above atrial
  • atrioventricular valves close
  • semi-lunar valves open
  • blood pushed out ventricles into pulmonary artery and aorta
• CARDIAC OUTPUT?

  volume of blood leaving ventricle in one minute

  -> heart rate x stroke volume
• TRANSPIRATION?

  1. Water evaporates out stomata
  2. Loss in water volume = lower pressure
  3. More pulled up xylem to replace
  4. Molecules are cohesive due to hydrogen bonds = column of water
  5. Molecules adhere to xylem walls, pulled up xylem creating tension
  6. Pulls xylem in to become narrower
• MASS FLOW HYPOTHESIS?

  1. Sucrose actively transported from companion cells into STE
  2. Decreases water potential in phloem
  3. Water enters phloem by osmosis
  4. Increases hydrostatic pressure (higher at source than sink)
  5. Solutes move down pressure gradient to sink cell
  6. Solutes removed so water potential near sink increases
  7. Water moves out phloem by osmosis, maintaining hydrostatic pressure gradient
• ACTIVE LOADING?

  1. Companion cells pump H+ out cytoplasm via proton pump using ATP
  2. Large concentration of H+ in cell wall of companion cells
  3. Diffuse down concentration gradient back into cytoplasm through co-transporter protein
  4. Carry sucrose into companion cells against concentration gradient
  5. Sucrose enters sieve tubes via plasmodesmata
  6. High concentration of sucrose, decreases water potential in phloem
  7. Water enters phloem by osmosis
  8. Increases hydrostatic pressure (higher at source than sink)
  9. Mass flow of sucrose to sink, unloaded
• GENE?

  sequence of DNA nucleotide bases that codes for the amino acid sequence of a polypeptide or functional RNA
• GENOME?

  full set of genes in a cell of an organism
• PROTEOME?

  full range of proteins a cell is able to synthesise from the genome
• HOW ARE INTRONS SPLICED OUT?

  spliceosome