Biology Paper 1

• Bacterial cells are prokaryotic- this means they have no nucleus.
• Structure of a Bacterial cell:

  ~cell membrane- controls what goes in and out

  -Chromosomal DNA- large loop controls most of cell activity

  -Plasmid DNA- small loop

  -flagella-helps cell move
• Ribosomes are where proteins are made.
• The cytoplasm contains all the organelles within the cell.
• Plant and Animal cells are eukaryotic cells, which means they have a nucleus
• Enzymes are proteins that act as biologic catalysts, often breaking down molecules into short ones (Polymer to Monomers)
• Amylase breaks down starch into glucose.

  Protease breaks down proteins into amino acids

  Lipase breaks down lipids into glycerol and fatty acids
• The substrate fits into the active site of the enzymes, where its broken down into smaller substrates ( known as lock and key)
• ENZYME PRACTICAL-

  1)mix amylase with starch and set a timer

  2)remove few drops from mixture every 10 seconds and add iodine. Put drops into spotting tile.

  3) record time taken for no starch to be detected ( colour will remain orange)

  4) repeat at different temps or pH's

  5) plot a graph
• FOOD TESTS:

  starch-turns iodine orange to black

  sugars-turns Benedict's solution from blue to orange

  protein-turns Blurets's regant blue to purple

  lipids-turns cold ethanol cloudy
• Diffusion is the movement of particles from an area of high concentration to an area of low concentration. This is a passive process.
• Osmosis is the diffusion of water across a semi-permeable membrane to balance the concentration of solution from inside and out of a cell. Its from a low to high concentration
• Active transport is the movement of particles through a membrane via carrier proteins. This requires energy so it can move against the concentration gradient
• Magnification= image side/ actual size
• Cells specialise depending on different function they need to fulfill
• Stem cells haven't yet specialised so can differentiate into any type of cell. Found in meristems and embryo's
• Embryo clones can be made of a person to harvest stem cells that can then be used to treat certain conditions within the persons body without them being rejected
• Communicable diseases can be spread from person to person e.g. measles. They are spread by pathogens such as bacteria or viruses.
• Non-communicable diseases are diseases that cannot be spread from person to person e.g. coronary heart disease.
• Health- state of physical and mental wellbeing.
• Ill health can be caused by both communicable and non-communicable diseases.
• Physical barrier to infection:

  1. Skin- a thick barrier where pathogens can only enter via wounds or vectors that pierce the skin e.g. mosquitos.
  2. Mucus- a sticky secretion produced by lining mouth, nose, windpipe. It traps pathogens trying to enter the body.
  3. Ciliated cells- found in nose, trachea, and brush pathogens away or out the body.
• Chemical defence to infection:

  1. Hydrochloric acid- found in the stomach, most pathogens are killed or destroyed due to low pH.
  2. Lysozyme- an enzyme that breaks down (digests) the cell walls of some bacteria. Found in tears, mucus, and vaginal fluid.
• Clinical Trials:

  1. The pre-clinical stage of testing is done on cells and tissue.
  2. Testing may be carried out on animals.
  3. A small clinical trial is held.
  4. A large scale trial is carried out with people with the disease.
• Vector- an organism that transfers pathogens from one person to another e.g. mosquito.
• Pandemic- Global infection.
• Epidemic- an infection in a country or particular area e.g. ebola.
• Lymphocytes- a type of white blood cell.

  Antigens- molecules on the surface of all cells and virus particles.

  Antibodies- are produced by lymphocytes, they are molecules that attach to antigens of pathogens and destroy them.
• Memory lymphocytes remain in the blood after an infection. They respond to the same pathogen much faster and more antibodies and produced, as a secondary response occurs. This leads to immunity.
• Immunisation- a vaccine contains dead or inactive forms of the pathogen. It initiates a primary response. If the real pathogen enters the body a secondary response occurs and the person wont become ill. They are immune.
• Cardiovascular disease is the disease of the cardiovascular system ( heart, arteries, capillaries, veins). It's non-communicable.
• BMI= weight (kg)/ height (m)^2
• Alleles are different forms of the same gene. They are responsible for variation within a species e.g. eye colour.

  Homozygous- alleles with the same chromosomes e.g. BB or bb

  Heterozygous- alleles with different chromosomes e.g. Bb or Cc
• Dominant alleles- the more power allele e.g. the B in Bb

  Recessive alleles- 2 of these are required eg. bb

  Genotype- all the alleles in an organism

  Phenotype- physical characteristics inherited e.g. purple flowers
• Stimulus, receptor, sensory neurone, CNS, motor neurone, effector, response
• Stimulus, receptor, sensory neurone, CNS, motor neurone, effector, response
• Sensory neurone adaptations:

  long to allow fast transmission.

  mylien sheath which is a fatty layer that insulates neurone to stop it from passing transmission to other neurones.
• Synapse is a gap or junction between neurones. It slows down transmission speed. Ensures impulses flow in one direction.
• DNA is a polymer, the nucleotides are the monomers. They are made up of a sugar a base and a phospate group
• The complementary bases in DNA are held together by weak hydrogen bonds