biology

• How can embryonic stem cells be encouraged to differentiate?

  Embryonic stem cells can be encouraged to differentiate into most types of specialized cells.
• How could stem cell technology be used to repair damaged organs?

  Scientists and doctors could use stem cell technology to repair damaged organs by growing new tissue from stem cells produced by embryos created using genetic information from the patient.
• What is a limitation of adult stem cells compared to embryonic stem cells?

  Adult stem cells can be cultured in the lab and made to differentiate into specialized cells, but of fewer types than embryonic stem cells (predominantly cells of the blood).
• What are some potential diseases that stem cells could be used to cure in the future?

  Stem cells could be used to cure many diseases in the future, such as diabetes and paralysis.
• 3 substances that can diffuse through cell membranes

  1. oxygen

  2. carbon dioxide

  3. urea
• what is diffusion


  The net movement of particles from an area of high concentration to an area of low concentration.
• 2 substances that cant diffuse through membranes

  1. starch

  2. proteins

  (big molecules)
• Describe how you could investigate the effect of pH on the rate of amylase activity

  1. Put a drop of iodine solution in each well of a spotting tile.

  2. Place a Bunsen burner on a heat proof mat with a tripod and gauze over the Bunsen burner. Put a beaker of water on top f the tripod and heat the water until its 35 degrees using a thermometer. (keep temperature consistent throughout)

  3. Use a syringe to add 1cm(3) of amylase solution and 1cm(3) of buffer solution with a pH of 5 to a boiling tube. Put the tube in the beaker of water wait 5 minutes.

  4. Use a different syringe to add 5cm(3) of starch solution to the boiling tube.

  5. Immediately mix the contents of the boiling tube and start the stopwatch.

  6. Use continuous sampling to record how long it takes for the amylase to break down all the starch. To do this, use a dropping pipette to take a fresh sample from the boiling tube every 30 seconds and put a drop into a well. When the iodine solution remains browny-orange, starch is no longer present.

  7. Repeat the whole experiment with buffer solutions of different pH value.
• How do you prepare a food sample

  1. grind the food with a pestle and mortar.

  2.Transfer the food to a beaker and add some distilled water.

  3. Stir the mixture

  4. Filter the solution to get rid of any solid bits.
• What is the test for sugars

  Benedict's test, turns from blue to brick red (or green/ yellow)
• What is the test for starch

  Iodine test, turns from brown/orange to blue/black
• What is the test for proteins

  Biuret test, from blue to pink/purple
• What is the test for lipids

  Sudan III test, 2 layers will form, the top layer being bright red, if not there's no lipids.
• adaptations of arteries


  They carry blood under high pressures so the walls are thick and elastic.

  Small lumen

  Contain thick layers of muscle to make them strong and elastic fibers to allow them to stretch and spring back.
• Why are arteries adapted to carry blood under high pressures?

  Arteries have thick and elastic walls.
• What is the function of the thick layers of muscle in arteries?


  To make arteries strong.
• Why do arteries have elastic fibers in their walls?

  To allow arteries to stretch and spring back.
• What is the significance of the small lumen in arteries?

  It helps maintain high blood pressure.
• Adaptations of capillaries


  Arteries branch into capillaries,

  They are very tiny- too small to see

  They carry blood really close to every cell to exchange substances with them.

  They have permeable walls, so substances can diffuse in or out.

  They supply food and oxygen and take away waste like carbon dioxide

  One cell thick walls, short diffusion path
• How do arteries relate to capillaries?

  Arteries branch into capillaries
• What is a key characteristic of capillaries in terms of size?

  They are very tiny- too small to see
• What is the main function of capillaries in the body?

  They carry blood really close to every cell to exchange substances with them
• Why are capillary walls considered permeable?

  They have permeable walls, so substances can diffuse in or out
• What substances do capillaries transport to and from cells?

  They supply food and oxygen and take away waste like carbon dioxide
• What is the advantage of capillaries having one-cell-thick walls?

  One cell thick walls, short diffusion path
• What structures join up to form veins?

  Capillaries
• adaptations of veins


  Capillaries join up to form veins.

  The blood is at a lower pressure here so the walls don't need to be as thick

  They have bigger lumen to help the blood flow

  They have valves to keep the blood flowing in the right direction.
• Why do veins have thinner walls compared to arteries?

  The blood is at a lower pressure in veins
• What is the purpose of the larger lumen in veins?

  To help the blood flow
• What is the function of valves in veins?

  To keep the blood flowing in the right direction
• Advantages of statins


  Reduces the risk of strokes, heart attacks, and coronary heart disease

  Reduces bad cholesterol and increases good/HDL cholesterol

  Can prevent other diseases
• Disadvantages of statins


  Must be taken long term and regularly to work

  Can have negative side effects like headaches, kidney failure, liver disease, or memory loss

  Effects are not instant, takes time to kick in
• what is transpiration


  evaporation of water from plant leaves
• factors that affect the rate of transpiration and how

  - an increase in temperature will increase the rate, as more energy is transferred to the water particles to allow it to evaporate

  - faster air flow will increase the rate, as it will blow away water vapor allowing more to evaporate

  - increased light intensity will increase the rate, as it will cause stomata to open

  - an increase in humidity will decrease the rate as the air contains more water vapor, so the concentration gradient for diffusion is lower
• factors that affect the rate of transpiration


  light intensity, temperature, wind speed, humidity
• how can you measure the rate of transpiration

  Using a potometer to measure the uptake of water by a plant because you can assume that water uptake is directly related to water loss

  (keep the conditions constant throughout like humidity and temperature)
• Symptoms and treatments of gonorrhoea

  STI

  pain when urinating and colored discharge

  treated with antibiotics but some have is resistant now

  use barrier methods like condoms
• where did aspirin originally come from

  willow
• where did digitalis originally come from

  foxgloves
• What are monoclonal antibodies

  Produced from lots of clones of a single white blood cell

  They're all identical & will only target one specific protein antigen