RANDOM AS - SHORT EXAM QS

• Give the two types of molecule from which a ribosome is made?

  rRNA/ RNA

  Protein
• 4 structural differences between DNA and mRNA?

  DNA has deoxyribose, mRNA has ribose

  DNA is double stranded/ helix, mRNA is single stranded

  DNA is long, mRNA is short

  DNA has thymine, mRNA has uracil

  DNA has hydrogen bonds, mRNA has no hydrogen bonds

  DNA has complementary base pairing, mRNA does not
• One difference between TEM and scanning electron microscope? and why?

  3D with SEM, but 2D with TEM OR

  only surface visible with SEM but internal structures visible with TEM

  ---------------------------------------------

  because electrons are deflected (in SEM)

  OR

  electrons transmitted/pass through (using TEM)
• The resolution of an image obtained using an electron microscope is higher than the resolution of an image obtained using an optical microscope. EXPLAIN WHY?

  shorter wavelengths between electrons

  OR

  longer wavelengths between light
• A student determined the size of a cell structure from a photograph obtained using a microscope. He used a ruler and a calculator and answered μm. Describe how the student determined the size of the structure (2)?

  Measure the length of the structure

  divide by magnification

  correct conversion from measured length to micrometers.
• Name two structures found in all bacteria that are not found in plant cells?

  Circular DNA

  Murein cell wall/ peptidoglycan cell wall/ glycoprotein cell wall
• Name two features of HIV particles that are not found in bacteria. (2)?

  Envelope proteins

  Reverse transcriptase

  Caspid

  RNA genome
• Describe how the scientist will use information from the colorimeter and her calibration curve to determine the pO2 in a sample of lugworm blood.?

  Measure light (absorption/transmission)

  interpolate/ draw line to curve line then to pO2

  or read off pO2 figure against absorbance/transmission value obtained
• Describe how monomers join to form the primary structure of a protein?

  Condensation reaction between amino acids

  forming peptide bonds

  creating specific sequence/ order of amino acids
• Describe one similarity and one difference between the induced-fit model of enzyme action and the lock and key model of enzyme action.?

  Similarity:

  • substrate fits/binds to active site
  • OR enzyme substrate complex formed

  Difference:

  • Active site changes shape, but does not change in lock and key
• State how enzymes help reactions to proceed quickly at lower temperatures?

  Reduce activation energy
• Explain a property of iron ions that enables these ions to carry out their role in red blood cells.?

  Is charged/ polar - so is part of haem

  SO binds/associated/loads oxygen

  OR forms oxyhaemoglobin

  OR transports oxygen
• What is a tumour?


  Mass abnormal cells/ tissue

  produced from uncontrolled mitosis/ cell division
• Describe how you would determine a reliable mitotic index (MI) from tissue observed with an optical microscope.?

  Count cells in mitosis in field of view

  Divide this by the total number of cells in field of view

  Repeat many times (min 5 times)

  OR

  select field of view at random
• The student used a sterilised pipette to transfer E. coli into each culture. Suggest why the number of E. coli cells per mm3 in each culture after 24 hours might have been lower if the student had not used a sterilised pipette. Explain your answer?

  Unknown/ new microorganisms/bacteria/pathogens introduced

  These bacteria use food or space

  and produce toxins
• Describe how the composition of blood in the pulmonary artery of a fetus is different from the composition of blood in the pulmonary artery of its mother.?

  Fetal blood has more oxygen + less CO2

  because gas exchange occurs in placenta

  BUT does not occur in fetal lungs
• Explain how a fetus is protected against the pathogens that infect its mother during pregnancy (lines 5–6)?

  Antibodies from mother are complementary/ bind specifically

  To pathogens crossing the placenta

  Giving passive immunity in fetus

  OR

  giving immediate protection in fetus
• Explain how a fetus is protected against the pathogens that infect its mother during pregnancy (lines 5–6)?

  production of more memory cells

  so higher concentration of antibodies in blood

  so more rapid production of antibodies (on further infection)
• What is a gene?


  A sequence of DNA bases that codes for a polypeptide
• Describe how the production of messenger RNA (mRNA) in a eukaryote cell is different from the production of mRNA in a prokaryote cell?

  Pre-mRNA produced in eukaryote cell

  Splicing only occurs in eukaryote cell

  Introns removed in eukaryote

  INTRONS not present in prokaryote
• Scientists produced a short, single-stranded, artificial nucleic acid, called PNA. The PNA binds to a small section of DNA. The scientists introduced PNA into cells and discovered that these cells produced less mRNA than cells that did not contain PNA. Suggest how PNA affected the transcription of the section of DNA (2)?

  PNA is complementary to DNA/ forms base pairs with DNA

  Prevents RNA polymerase activity/binding

  OR reduces transcription
• Describe the role of ATP in the process of translation in protein synthesis?

  Provides energy

  So peptide bonds form between amino acids

  OR amino acids join to tRNA
• What term is used to describe the different structures of α-glucose and β-glucose?

  Isomers
• A student investigated the difference in the reducing sugar content of two fruit juices. He performed a biochemical test on each fruit juice using Benedict’s solution. He then used a colorimeter with each test result. Describe how the results from the colorimeter can identify the fruit juice containing the higher sugar content?

  Higher absorbance has more sugar

  OR lower transmission has more sugar
• The student controlled variables in the test using Benedict’s solution. Give two variables the student controlled.?

  Benedicts solution - VOLUME

  Benedicts solution - CONC

  Fruit juice - VOL

  Water bath - Temperature
• Iodine solution stains fresh apple tissue black. When iodine solution is added to apples stored for a week, the stain is less black. The water potential of apple juice decreases when apples are stored. Suggest why the water potential of apple juice decreases when apples are stored?

  Starch has hydrolysed

  Maltose is soluble - so has reduced water potential

  OR STARCH IS INSOLUBLE
• Describe and explain two ways that structures shown in Figure 1 increase the rate of absorption by this cell?

  Microvilli increase surface area for DIFFUSION or FOR more channel/carrier proteins

  AND many mitochondria release ATP for active transport

  
• The protein ZO-1 is found on the surface of ileum cells. A scientist used an anti-ZO-1 monoclonal antibody to identify ileum cells in a sample of intestine observed using an optical microscope. Suggest how the monoclonal antibody helped the scientist to identify ileum cells in the sample of intestine.?

  ZO-1 located in cell surface membrane

  Antibody is complementary to ZO-1

  so it binds to THE ZO-1 protein

  CELLS identified with stain/dye or fluroscent marker linked to antibody
• Describe how organisms are grouped in a phylogenetic classification system?

  Hierarchy of groups with no overlaps // SMALLER GROUPS WITHIN LARGER GROUPS WITH NO OVERLAPS

  Grouped according to evolutionary origins
• give three control measures the student must use to reduce the risks associated with carrying and using a scalpel?

  Carry with blade protected

  Cut away from body

  Cut on hard surface

  Disinfect/ dispose of used scalpel (as instructed)
• Name the type of selection the scientist investigated in this fish tank. Explain why this selection affected the frequency of alleles in the population of guppies in this fish tank?

  Directional

  Fish with more spots more likely to be predated

  Alleles for more spots not passed on

  so frequency of more spots alleles decreases
• Suggest: • a further investigation the scientist could do to confirm that the brightly coloured stones had affected guppy behaviour • a null hypothesis for the new investigation.?


  Investigation: repeat without stones/ or with uniformly coloured stones Null hypothesis: Brightly colored stones have no effect on guppy behavior.
• Suggest one type of guppy behaviour that could be affected by the presence of brightly coloured stones.?

  Mating/ courtship/ sexual behaviour
• Other than a change in temperature, give one change the scientist could make to the environmental conditions to increase the cut flowers’ shelf life?

  Reduce light intensity

  Stomata close

  So decreased rate of transpiration/evaporation

  ----------------------------------------------

  Increase humidity

  Reduces water potential gradient

  Decreased rate of transpiration/evaporation
• Name the type of bond between: complementary base pairs?

  Hydrogen bonds
• Name the type of bond between: adjacent nucleotides in a DNA strand?

  phosphodiester bond
• Describe two differences between the structure of a tRNA molecule and the structure of an mRNA molecule.?

  tRNA has clover leaf shape, mRNA is linear

  tRNA has hydrogen bonding, mRNA does not

  tRNA has an amino acid binding site, mRNA does not

  tRNA has anticodon, mRNA has codon
• In a eukaryotic cell, the structure of the mRNA used in translation is different from the structure of the pre-mRNA produced by transcription. Describe and explain a difference in the structure of these mRNA molecules?

  mRNA has no introns - only exons (less nucleotides)

  OR

  pre-mRNA has exons and introns (more nucleotides)

  because of splicing
• Explain why it is not possible to determine the identity of the structures labelled X using an optical microscope.?

  resolution is too low

  because wavelength of light is too long
• U. marinum cells ingest bacteria and digest them in the cytoplasm. Describe the role of one named organelle in digesting these bacteria.?

  Lysosomes

  fuse with vesicles

  release hydrolytic enzymes