Exam Q mistakes cells topic two

• Other than being smaller give two ways in which prokaryotic dna is different from eukaryotic

  • Prokaryotic dna is circular eukaryotic is linear
  • Prokaryotic dna isnot associated with histones
• Student cut thin section of tissue to view with an optical microscope

  Explain why it’s important that the sections were thin

  1. It allows more light to pass through
  2. so a single layer of cells can be viewed
• Suggest one advantage of the higher percentages in cholesterol in red blood cells

  Red blood cells are free in the blood so cholesterol helps maintain the shape
• E. coli, I have no cholesterol in its cell surface membrane despite this maintains a constant shape. Explain why.

  1. The cells unable to change shape.
  2. as it has a cell wall
  3. made of murein/ peptidoglycan
• Which organelle is not surrounded by two membranes

  Golgi apparatus
• Explain the role of these cells in the production and secretion of breast milk

  • many Golgi vesicles to transport protein out of the cell
  • Many mitochondria which produce atp which releases energy for synthesis of proteins / active transport / movement of vesicles
• Explain how the organelles (mitochondria) help the cell of small intestine absorb the product of digestion

  1. Mitochondria is the site of Aerobic respiration which produces ATP and release energy
  2. For active transport
• A transmission electron microscope was used explain why

  1. High resolution
  2. So you can see the internal structures of an organelle
• Advantage of TEM than SEM

  1. Higher resolution
  2. Allows internal structures of an organelle to be seen
• Advantage of SEM than TEM

  1. Thin sections don’t need to be prepared
  2. Can have 3D images / shows surface of specimen
• Homologous chromosomes CARRY the same GENES but aren’t genetically identical explain why

  Different allele
• give two reasons why from the image you could tell it was anaphase

  • chromatids are in two groups at poles of the cell at the end of the spindle
  • v shape shows the sister chromatids being pulled apart from the centromere
• Describe and explained what the student should have done when counting cells to make sure that the mitotic index he obtained from the root tip was accurate

  1. Examine large numbers of field of views
  2. To ensure it’s a representative sample
  3. Repeat the count
  4. To ensure his figure is correct
  5. Count only whole cells
  6. To standardise counting
• Suggest how the chemical stops the growth of roots

  1. It stops mitosis/ cell division / anaphase
  2. By stopping spindle fibres from forming
  3. Prevents the separation of sister chromatids
  4. So no new cells are added to the root top therefore no growth
• From looking at a diagram what evidence does it give that they are homologous chromosomes

  1- same size

  2- same shape

  3- same loci

  4- same genes
• telophase chromosomes behaviour and appearance

  chromosomes uncoil and become thinner and longer
• graph tip for mitosis

  remember that for next stage of mitosis to start the previous one needs to end
• explain how you would recognise which cells are in interphase

  no visible chromosomes
• explain how you would identify which tissue was taken from a cancerous

  tumour using data on tables

  Higher percentage of cells in mitosis.

  more cells dividing much more quickly
• The rate of self division is important in investigation into cancer. Suggest why?

  • Faster rate of division means faster rate of growth of cancer
  • measuring rate of cell division would help to show how effective treatment was
• Suggest why they gave bromelain in addition to rather than instead of the usual treatment

  • Not ethical to replace a conventional treatment
  • Life of patient at risk if bromelain isn’t effective
• Describe role of 1 named organelle in digesting bacteria

  1. Lysosome
  2. Fuses with vesicles
  3. Release hydrolytic enzymes
• outline the role of organelles in production transport and released of proteins in eukaryotic cells

  1. dna in nucleus codes for proteins
  2. ribosomes produce /synthesise proteins
  3. mitochondria produce atp for protein synthesis
  4. Golgi apparatus modifies and packages proteins
  5. vesicles transport
  6. vesicles fuse with cell surface membrane
• Explain why the specimen was thin when using optical microscope

  1. allows light to pass through the specimen
  2. A single layer of cells can be viewed
• Describe how you would make a temporary amount when using an optical microscope (4)

  1. Place A drop of water on a glass slide
  2. Use forceps to get A thin layer of tissue and place on top of water droplet
  3. Stain with iodine in potassium iodide
  4. Use mounted needle to slowly lower coverslip
• Contrast how an optical microscope and a TEM work and contrast their limitation of use when studying cells (6)

  1. TEM used electrons and optical uses light
  2. TEM allows greater resolution
  3. So with TEM smaller organelles can be viewed
  4. Tem only views dead specimens and optical can view living
  5. Tem doesn’t show colour and optical can
  6. Tem requires thinner specimen
  7. Tem requires a more complex time consuming preparation
  8. Tem focuses using electromagnets and optical uses glass lenses
• before cells were examined it was stained that caused parts of the cell surface membrane to appear as two dark lines

  suggest an explanation for appearance of cell surface membrane as two dark lines

  1. membrane has phospholipid bilayer
  2. stain binds to phosphate
  3. on inside and outside of membrane
• osmosis practical the student did several repeats explain why repeats are important

  Helps to identify anomalies

  2) makes average more reliable
• The student calculated percentage change in mass rather than the change in mass explain the advantage in thsi

  1. It allows you to compare
  2. As each potato cylinder has different initial masses
• before requesting the student blotted dry each cylinder outside explain why

  1. excess water on outside will affect the mass
  2. amount of water on each cylinder varies
• The scientist concluded that the cells in flask g took up sodium ions by active transport explain how the information given supports this

  1. Uptake in flask g is much more greater than flask F
  2. Which shows the use of atp in flask g
  3. Also sodium concentration in flask g falls to zero
  4. Which helps to show an uptake against the concentration gradient

  
• The curve for flaks f levelled of after twenty minutes explain why

  1. uptake by facilitated diffusion
  2. Equilibrium of concentrations was met

  
• Explain how the active transport of amino acids into the blood stream from epithelial help create the conditions needed for process a ( facilitated diffusion of aa from gut lumen to epithelial )

  1. Lower the concentration of amino acids in epithelial
  2. Helps to establish a concentration gradient between lumen and cell
• Suggest 1 explain action for faster rate of plasmid replication in cells growing in a culture with a high amino acid concentration (2)

  1. Amino acids are used in protein synthesis
  2. So more enzymes for plasmid replication or more dna polymerase
  3. Amino acids used in respiration
  4. So more energy for plasmid replication
• student cut a thin section of tissue to view with optical microscope explain why it’s important that the sections were thin

  1. allows light to pass through
  2. so a single layer of cells can be viewed
• describe how a sample of chloroplast would be isolated from leaves 4

  1. grind the leaves in a blender to homegenise then filter to remove large tissue debris
  2. use a cold isotonic buffered solution
  3. centrifuge and spin to remove nuclei
  4. centrifuge at higher speed so chloroplast settle at the bottom as a pellet
• Describe three properties of cell fractionating solution and explain how each property prevented damage to organelle

  1. Ice cold - lowers kinetic energy which reduces enzyme activity to prevent digestion of organelle
  2. isotonic - same water potential to prevent lysis or shrivelling of organelle by osmosis
  3. Buffered - maintains ph to prevent enzyme and proteins from denaturing
• describe and explain how centrifuging the culture allowed scientists to obtain a cell free liquid (3)

  large dense heavy cells

  • form a pellet at bottom of tube
  • liquid supernatant can be removed
• what’s homologous chromosomes

  pair of chromosomes with same genes in the same loci
• give two peice of evidence from figure one to support that these two are homologous chromosomes

  1. same shape
  2. same length
  3. same loci
  4. same genes