questions 1

• describe the processes in which amino acids are used to make proteins(5)

  • translation
  • MRNA attaches to a ribosome
  • TRNA charged with an amino acid has a complementary anticodon to the first codon on the MRN
  • anticodon on TRNA complementary base pairs to codon on the MRNA
  • 2 amino acids are joined by peptide bond, the first TRNA leaves and ribosome moves along
• explain how the eye lens protein has a shape that enables it to function

  • there is a gene for the eye lens protein
  • during transcription, uses gene to make MRNA
  • each codon on the MRNA codes for a specific amino acid
  • during translation, the codons are used to join amino acids together by peptide bonds-primary structure
• what features are used to classify organisms

  • phenotypes
  • genotypes
  • and how they are related
• describe how 2 species can evolve from a common ancestor

  • geographical isolation splits the original population into 2
  • natural selection acts on each population seperately
  • because different selection pressures in are so different alleles are advantageous
  • so different alleles/characteristics allow organisms to survive and reproduce and frequency of allele increases in gene pool
  • 2 populations become reproductively isolated, reducing gene flow between the two populations
  • different species
• compare and contrast allopatric speciation to sympatric speciation

  • allopatric requires geographical isolation whereas sympatric speciation does not
  • allopatric results in populations experiencing different selection pressures but sympatric does not
  • in allopatric speciation, natural selection acts on 2 populations but sympatric acts within a population
• types of mutations

  substitution=different amino acid or same amino acid as DNA code is degenerate

  deletion or insertion=causes a frame shift, all codons that follow mutation are changed

  • primary sequence of protein is changed resulting in different R groups so different bonds in the tertiary structure(disulphide)
  • could result in stop codon so polypeptide is short
• describe the light dependant reactions of photosynthesis

  • light energy absorbed by photosystem(2)
  • an electron in chlorophyll excited
  • electrons move to higher energy level, these move down ETC to photosystem(1), losing energy as they move down
  • energy used to produce ATP from ADP+PI
  • electrons excited again at photosystem and electrons transferred to NADP to form NADPH
• describe the light-independent reaction

  • carbon fixation, c02+RuBP catalysed by RUBISCO forming unstable GP(6 carbon)
  • GP reduced using ATP and hydrogen from NADPH to form GALP
  • 1/6 GALP converted to glucose and 5/6 for the regeneration of RuBP
• why does a low metabolic rate mean sloths can survive on very little food

  • low metabolic rate means less demand for ATP
  • ATP produced during aerobic respiration
  • which uses glucose and oxygen
  • glucose is produced by plants
  • demand for glucose is low so sloths can survive on less food
• describe the structure of an antibody

  • 4 polypeptide chains
  • 2 heavy and 2 light chains
  • each chain has a variable region and a constant region
  • variable region of antibody form the antigen binding sites
  • the shape of the variable region is complementary to a particular antigen
• describe the mechanisms mammals will use to maintain 38 degrees in a hot environment

  • sweating increased=water evaporates from the skin surface and removed heat from the body
  • vasodialation=arterioles near skin surface dialate, more blood flows through the capillaries in the surface of skin-more heat is lost by radiation
  • hairs lie flat=erector pili muscles relax, less air trapped so skin is less insulate, more heat can be lost
• heat is produced during aerobic respiration when ATP is produced during oxidative phosphorylation. Describe this process

  • hydrogen atom released from reduced NAD and reduced FAD
  • hydrogen split into protons(H+) and electrons
  • the electrons move down the ETC along electron carriers via redox reactions, releasing energy
  • energy used to pump protons into intermembrane space creating proton gradient
  • protons move down electrochemical gradient back into matrix through ADP synthase
  • ATP created-called chemiosmosis
  • electrons recombine with protons and react with oxygen to form water
• describe how muscle contracts(3)

  • myosin and actin myofilaments slide over one another
  • sarcomeres contract
  • sarcomere shortens and muscle contracts
• explain how the muscles of marathon runner are adapted for long-distance running(5)

  • high proportion of slow twitch fibres
  • muscles contract slowly for endurance
  • energy releases slowly through aerobic respiration
  • lots of mitochondria for aerobic
  • lots of blood vessels to supply oxygen and glucose for respiration
  • red in colour due to high conc of myoglobin
• explain how the muscles of an Olympic weightlifter are adapted for small,powerful movements(5)

  • higher proportion of fast twitch muscle fibres
  • as muscles contracting very quickly for short bursts of speed and power
  • energy released via anaerobic respiration-using glycogen
  • very few mitochondria and blood vessels-low demand for 02 and aerobic respiration
  • whitish as not much myoglobin
• suggest why high concentrations of lactic acid would cause muscle fatigue

  • H+ ions produced when lactic acid dissociates
  • lowers the PH
  • denaturing enzymes involved in production of ATP
  • less ATP is available for muscle contraction
• suggest how an enzyme could convey tolerance to lactic acid

  • lactate hydrogenase
  • converts lactic acid to pyruvate
  • reducing H+ ion concentration