Biology

• Advantages of statins


  it is easy to take .

  decreases the blood cholesterol in the heart muscle .

  slows down the build up of fatty materials.

  low cost.

  maintains blood flow.
• Disadvantages of statins.


  Might be side effects.

  effects of the drug takes time to happen.

  drug will need to be taken long term .
• Advantages of stents


  Blocked artery is held open.

  Blood flow is increased.

  it will stay in place for a long time .

  effect of drug is immediate.

  rapid recovery from operation.
• Disadvantages of stents


  Risk of infection from operation.

  risk of surgery.

  risk if blood clot .

  it is expensive.
• A microscope has x5 eyepiece lens .

  describe how to use this microscope to observe a prepared slide of root hair cells at a magnification of x50

  -Place slide on stage

  -use lowest power

  -adjust mirror

  -move stage close to lens (avoid stage from touching lens)

  -turn focussing knob until image comes into focus

  -use fine focus to clear image

  -x50/x5=x10

  -refocus slide
• Describe how nitrate ions are used in a plant to help it grow .


  Nitrate ions are used with glucose to form amino acids used to synthesise proteins.
• Explain why plants infected with tobacco mosaic virus grow slowly 


  Less chlorophyll which causes discolouration so reduced photosynthesis and less glucose is produced so less proteins for growth
• Explain how the structure of enzymes molecules is related to the effect of the PH on the activity of amylase.


  -enzymes are protein molecules and have 3D structure which is the lock and key theory

  they have an active site which has a specific shape so the shape only matches shape of substrate .

  • starch is substrate for amylase

  at PH values the shape of active site changes and the substate can no longer fit it .

  • if its too high the enzyme denatures so the shape of active site is changed so amylase can no longer digest starch
  • so rate of digestion decreases
• Plants absorb water by osmosis through a partially permeable membrane and travels through xylem to leaves and water is lost through the stomata driven out by transpiration🌳
• control conditions in greenhouses to reduce limiting factors can improve crop yields

  Heating

  artificial lighting

  Extra carbon dioxide
• Uses of glucose in plants

  Respiration

  stored as insoluble starch

  fats or oils

  combine with nitrate from soil to form amino acids for protein synthesis.
• Lactic acid builds up in the muscles cells during exercise ~ blood flows through the muscle cells and transports the lactic acid to the liver ~ the liver oxidises the lactic acid and converts it back to glucose. 


  Response to exercise HT
• Specialised cells in plants

  Root hair

  xylem

  phloem
• Specialised cells in animals 


  Nerve

  sperm

  muscle
• Magnesium ions are needed to make chlorophyll-not enough leads to leaves turning yellow.


  Nitrate ions are needed for protein synthesis- lack of nitrate leads to stunted growth
• Clinical trials use healthy volunteers and patients.

  1. health volunteers try a small dose of the drug to check if it is safe and record any side effects.
  2. a small amount of patients try the drug at a low dose to see if it works.
  3. A larger number of patients;different doses trialled to find the optimum dose
  4. a double blind trial will occur and the patients are divided into groups and some will be given the drug and some a placebo
• Arteries carries blood away from the heart

  1. Arteries walls are strong and elastic so they can carry blood at a high pressure.
  2. the walls are thick .
  3. they contain thick layers of muscle to make them strong and elastic fibres to all them to strech and spring back.


  Veins carries blood to the heart.

  1. blood is carried at a lower pressure so the walls don’t need to be thick .
  2. they have a bigger lumen to help with blood flow
  3. they have valves to prevent blood from flowing backwards.