Biology Paper 1 - AQA

• • eukaryotic cells are complex. all animal and plant cells are eukaryotic.
• • prokaryotic cells are smaller and simpler. bacteria are prokaryotic.
• • magnification = image size/real size
• • the process by which cells change to be specialised is called differentation. as cells change they develop different subcellular strucutres. they turn into different cells that make them carry out specfic functions.
• • the nucleus of a cell contains chromosomes. each chromosome carries a large number of genes. when the cycle divides this is mitosis.
• • diffusion is the spreading out of particles from an area of higher concentration to an area of low concentration. diffusion happens in both gasses and solutions.
• • osmosis is the movement of water molecules across a particulary permeable membrane from a less concentrated solution to a more concentrated solution.
• • active transport allows the plant to absorb minerals from a very dilute solution in the soil it moves the minerals againts the concentration gradient. but activation needs energy from respiration to make it work again.
• the alveoli are specialised for the diffusion of oxygen and carbon dioxide they have:

  • large surface area
  • very thin walls
  • good blood supply
• the inside of the small intestine is covered in millions of villi. they increase the surface area so that digested food is absorbed more quickly into the blood. they have:

  • a single layer of surface cells
  • very good blood supply
• two types of microscopes

  light and electron
• Using a light microscope


  1. Clip the stage onto the stage

  2. Select the objective lens with the lowest magnification

  3. Use the coarse adjustment knob to the stage up to just below the objective lens

  4. Look down the eyepiece. Move the stage downwards until the image is roughly on focus

  5. Move the fine adjustment knob, until you get a clear image of what's on the slide

  6. If you want a bigger image, use the objective lens with a higher magnification and refocus
• two different types of stem cells

  embryonic and adult stem cell
• adult stem cell


  certain places in the bone marrow ( a tissue inside bones ) and can only produce certain types of specialised cell eg blood cells
• embryonic stem cell 


  could be used to replace faulty cells in sick people eg you could make nerve cells for people with paralysis (where they can't move a part of the body due to a injury to their spine ) or insulin producing cells for people with diabetes
• therapeutic cloning 


  its possible to make an embryo that has the same genes as a patient
• stem cells


  there can be risks involved in using stem cells in medicine. For example the stem cells could be infected with a virus. the virus could be passed on to a patient and make them sicker
• meristems 


  plants have tissues
• meristems

  are where growth occurs- in the tips of roots and shoots and the meristems contain stem cells that can differentiate into any type of plant cell. they can do this all through the plants entire life
• meristems 


  these cells can be used to make clones ( identical copies )of plants quickly and cheaply clone can be made of rare species and crop plants
• rare species 


  to prevent them being wiped out
• crop plants 


  that have features that are useful fro farmers eg plants aren't killed by a disease
• factors of diffusion 


  concentration gradient, temperature,surface area
• cells can use diffusion to get rid of waste products such as 


  carbon dioxide - ( from respiration ) and urea ( from the breakdown of proteins ) - urea diffuses from cells into the blood plasma. it is then removed from the body by the kidneys
• calculate an organism surface area to volume ratio

  surface area, volume, surface area to volume ratio
• • a tissue is a group of similar cells that work together to carry out a function.
• • an organ is a group of different tissues that work together to perform a certain function. an organ system is a group of organs working together to perform functions. it breaks down and absorbs food.
• • a catalyst is a substance which increases the speed of reaction without being changed or used up.
• • carbohydrases:
  • amylase
  • amylase is made in the salivary glands. pancrease and small intestine
  • it works in the mouth and small intestine
• • protease:
  • proteases are made in the stomach and pancrease and the small intestine
  • they work in the stomach and small intestine
• • lipases:
  • lipases are made in the stomach and pancrease and small intestine
  • they work in the small intestine
• • bile is produced in the liver. it's stored in the gallbladder before it's released into the small intestine.
• • the air you breathe in goes through the trachea. then it passes through the bronchi then the bronchioles and ends up in the alveoli. alveoli carries out gas exchange.
• communicable disease is a disease that can be spread from a person to a person or between ani and people. communicable diseases can be caused by bacteria, pathogens or fungi. measles and malaria are example of communicable diseases.
• • non communicable diseases are diseases that can not be spread between people or between animals and people. coronary heart disease is an example of non communicable disease.
• • stents are tubes that are put inside coronary arteries by surgery. they keep the arteries open. this allows blood to reach the heart muscle and reduces the risk of heart attack.
• • stents are effective for a long time. recovery time from the surgery is also quite quick. but there are risks, these include having a heart attack during the operation, or getting an infection after surgery. paitents may also develop a blood clot near the stent.
• satins are drugs that can reduce the amount of cholesterol in the blood. this slows down the rate of fatty deposits forming. advantages:

  • risk of strokes, heart disease, coronary heart disease
  • help prevent other diseases
• disadvantages of statins

  • must be taken reguarly
  • can casue unwanted side effects
  • it takes time to work
• artificial hearts can be used to keep a person alive until a donor heart is avaliable. sometimes artifical hearts are permanent, so donor hearts isn't needed anymore.