Mocks

• Define universal.


  The same codon/triplet always codes for the same amino acid.
• Describe how the appearance of the area containing DNA in a TEM image of a eukaryotic cell would differ from a prokaryotic cell.


  1. The DNA would be contained in a nucleus
  2. Would see a nucleolus
• Describe the mechanism of breathing that causes air to enter the lungs.


  1. The diaphragm contracts and flattens.
  2. The external intercostal muscles contract and the ribcage is pulled up.
  3. The volume increases and pressure decreases in the lungs, causing air to enter the lungs.
• Suggest how bacteria with a thicker capsule are more likely to survive and so cause lung disease.


  1. The phagocyte would have to travel further to bind to the murein cell wall.
  2. Phagocytes wouldn't be stimulated so there would be more bacterial growth.
• COOH is the carboxyl group of an amino acid and is always there.
• Describe 3 functions of bile salts.


  1. They emulsify larger fat droplets into ones that are small enough to be digested
  2. They form micelles
  3. Increase the surface area for increased lipase activity
• State one feature that shows the images were taken with an electron microscope and not an optical microscope.

  TEM has greater resolution and visible organelles e.g. nuclear membrane/ribosomes.
• Describe the role of tRNA in translation.


  1. Anticodon binds to complementary codon on mRNA.
  2. tRNA carries specific amino acid to ribosome.
• Suggest how the shape of the ATP synthase catalyses the synthesis of ATP.


  The active site is complementary to ADP and Pi so enzyme-substrate complex forms.
• Suggest how the shape of ATP synthase allows the movement of H+ ions.


  The protein channel allows facilitated diffusion of H+.
• Give the order of structures through which the blood will pass as it enters the heart and flows through the left ventricle.

  1. Pulmonary Vein
  2. Left Atrium
  3. Left AV valve
  4. Left Ventricle
  5. Left SL valve
  6. Aorta
• What causes the increase in cardiac output from rest to medium-intensity exercise?


  Increased stroke volume and increased heart rate.
• What causes the increase in cardiac output from medium-intensity exercise to high-intensity exercise?


  Increased heart rate.
• Name the type of blood vessel that controls blood flow to muscles and explain how these blood vessels change blood flow during exercise.

  Arteriole --> smooth muscle relaxes, vasodilation increase blood flow.
• A student prepared a plant root to observe cells undergoing mitosis. Why did he put the plant root in acid?


  1. To hydrolyse cell wall.
  2. Allow cells to be more easily squashed.
  3. Allows stain to diffuse into cells.
  4. Stop mitosis.
• Explain how sucrose-transport proteins in leaf cells enable the production of a pressure gradient in the phloem.


  1. Sucrose is co-transported into the phloem
  2. Causes decrease in water potential
  3. So water enters by osmosis
• Potato plants with fewer sucrose-transport proteins produce fewer potatoes and accumulate sugars in their leaves.

  Explain why.

  Carbohydrates made by photosynthesis, less sucrose transported into phloem at leaf/source.
• Give two reasons why glucose uptake by muscle cells increases significantly during exercise.

  Explain your answers.

  1. Muscle cells need to respire more to provide more ATP for muscle contraction.
  2. Increased glucose usage so concentration gradient for glucose so glucose enters by facilitated diffusion.