Specific details

• Epidermal tissues


  Covered with a waxy cuticle which helps to reduce water loss by evaporation
• The upper epidermis

  Is transparent so that light can pass through it to the palisade layer
• Spongy mesophyll

  Contains big air spaces to allow gases to diffuse in and out of the cells
• Xylem and phloem


  They transport things like water, mineral ions and food around the plant
• Meristem tissue 


  This is found at the growing tips of shoots and roots and is able to differentiate into lots of different types of plant cell, allowing the plant to grow
• Palisade mesophyll


  This is the part of the leaf where most photosynthesis happens
• Xylem:

  • Made of dead cells joined end to end with no end walls between them and a hole down the middle
  • They are strengthened with a material called lignin
  • Carry water and mineral ions
  • The movement of water from the roots through the xylem and out of the leaves is called the transpiration stream
• Phloem:

  • Made of columns of elongated living cells with small pores in the end walls to allow cell sap to flow through
  • They transport food substances (mainly dissolved sugars) made in the leaves to the rest of the plant for immediate use or for storage
  • The transport is bidirectional
  • This process is called translocation
• Transpiration


  caused by the evaporation and diffusion of water from a plant's surface
• Arteries 


  The heart pumps the blood out at high pressure so the artery walls are strong and elastic

  The walls are thick compared to the size of the hole down the middle(lumen)

  They contain thick layers of muscle to make them strong and elastic fibres to allow them to stretch and spring back
• Veins


  Capillaries eventually join up to make veins

  The blood is at low pressure in the veins so the walls don't need to be as thick as artery walls

  They have a larger lumen than arteries to help the blood flow despite the lower pressure

  Have valves to prevent back flow of blood
• Capillaries


  Arteries branch into capillaries

  Capillaries are too small to see

  Carry blood really close to every cell in the body to exchange substances with them

  They have permeable walls so substances can diffuse in and out

  Walls are one cell thick

  Take waste away like co2 and water
• How a heart uses its chambers


  Blood flows into the 2 atria from the vena cava and the pulmonary vein .

  The atria contract, pushing the blood into ventricles

  The ventricles contract forcing the blood into the pulmonary artery and the aorta out of the heart

  The blood then flows to organs via arteries and returns through veins

  The atria fill again and the cycle starts again
• Coronary heart disease


  When the coronary arteries that supply blood to the muscle of the heart get blocked up by layers of fatty material building up

  This causes the arteries to become narrow, so blood flow is restricted and there's a lack of oxygen to the heart muscle, this can result in a heart attack
• Stents 


  tubes that are inserted inside arteries. They keep them open making sure blood can pass through to the heart muscles, keeps the heart beating

  Lowers the risk of a heart attack happening and recovery time is quick

  There are risks during the operation, as well as picking up infections or even blood clots developing called thombosis
• Statins 


  Having too much LDL(bad cholesterol) can cause health problems.

  Too much (LDL) can cause fatty deposits to form inside the arteries which can lead to coronary heart disease

  Statins are a drug that can reduce the amount of bad cholesterol present in the bloodstream. This slows down the rate of fatty deposits forming
• Advantages of statins


  Statins can reduce the risk of strokes, coronary heart disease and heart attacks

  Increase levels of HDL which can help remove LDL

  Statins may also help prevent other diseases
• Disadvantages of statins


  Are a drug that must. be taken long term and regularly. There is a risk of. forgetting to take the drug

  Can cause negative side effects

  The effect of statins is not instant. It takes time to kick in
• The role of bile in emulsification


  Bile emulsifies fat

  It creates a larger surface of fat for the lipase

  Lipase can break down fat quicker
• Food tests --> Starch

  Add iodine solution to the sample

  Mix the contents

  If the sample contains starch the colour of the solution will change from orange to blue-black
• Food tests --> Protein

  Add Biuret's solution to the sample

  Mix the contents

  If the sample contains protein the solution will change from blue to lilac
• Food Tests --> Sugars

  Add some Benedict's solution to the test tube (about 10 drops)

  Place the test tube in the water bath using a test tube holder and leave it there for 5 mins

  If the sample contains less sugar it will go from blue to green

  medium sugar: blue to yellow

  high sugar: blue to brick red
• Testing drugs 6 marker:

  1. Preclinical trials of the drug on animals to test toxicity
  2. Clinical trials on healthy volunteers and patients at low doses
  3. Monitors side effects
  4. Then trials done to check dose
  5. Double-blind trials and use of placebo which doesn't contain drug
  6. Random allocation of patients to groups
  7. So no-one knows who has placebo
  8. Peer-review of data to prevent false claims
• Differences in anaerobic respiration


  Yeast produces ethanol

  Muscles produce lactic acid

  Both release small amounts of energy quickly

  Yeast produces CO2 muscles don't
• HCG hormone 6 marker

  (as) urine passes through reaction zone

  HCG hormone binds to the mobile HCG antibody (in the reaction zone) (passes up the stick) HCG hormone binds to the immobilised HCG antibodies in the results zone

  (the other) antibodies which do not attach to HCG

  bind to antibodies in control zone

  blue dye appears in both control and results zones (to show positive result)
• Mechanical valves:

  • More long-lasting
  • More durable
  • No ethical issues
  • Expensive
  • readily available
  • anti-clotting medicine required
  • risk of blood clotting
  • Risk of heart attack
• Biological valves;

  • Potential immune response
  • Higher death rate after put in place
  • Ethical issues as a pig's valve is used
  • Readily available
  • Potential need of immunosuppressants
  • More likely needing replacing and future operations
• Cell cycle


  Stage 1: The nucleus divides and replicates genetic information and the sub-cellular structures replicate

  Stage 2: One set of chromosomes is pulled to each end of the cell

  Stage 3: The cytoplasm and cell membrane replicate