Biology paper 1

• Long sighted people have short eyes and the image focuses behind the retina (converging lens) whereas short sighted people have long eyes and the image focuses in front of the retina (diverging lens)
• What do pathogens do?

  they attack cells and use enzymes to break down cell wall in order to get nutrients they need inside the cytoplasm.
• Why would someone with cataracts see blurry and what is the treatment?

  They would see blurry because protein has built up in the lens therefore light has dispersed and they would remove the cataract from the cornea to treat.
• What are the cell division stages?

  interphase- the DNA copies itself and the cell enlarges

  prophase- the cell condenses DNA into chromosomes and breaks down the nucleus

  metaphase- chromosomes line up in the middle of the cell

  anaphase- chromosomes are pulled to opposite ends of the cell

  telophase- two nuclear membranes form around the chromosomes at each end of the cell

  cytokinesis - cell divided down the middle to become two daughter cells
• What is the prokaryotic cell wall composed of?

  Peptidoglycan
• What are plasmids? 


  they are in prokaryotic cells and are small loops of DNA found free in the cytoplasm and separate from the main DNA. It carries genes
• What are the two types of cell?

  Eukaryotic( animals and plants ) - has a nucleus

  prokaryotic( bacteria ) - a simple cell that does not have a nucleus and the DNA is free in the cytoplasm
• What is the lytic pathway?


  -the virus attaches itself to a specific host cell and injects its genetic material into the cell

  -the virus uses proteins and enzymes in the host cell to replicate its genetic material and produce the components of new viruses

  -the viral components assemble

  -the host cell splits open, releasing the new viruses, which infect more cells ( viral replication)
• what is the lysogenic pathway?

  A type of viral replication where the virus integrates its genetic material into the host cell's DNA and remains dormant until triggered to enter the lytic pathway.

  -the injected genetic material is incorporated into the genome(DNA) of the the host cell

  -the viral genetic material gets replicated along with the host DNA every time the host cell divides but the virus is dormant( inactive) and no new viruses are made.

  -eventually a trigger causes the viral genetic material to leave the genome and enter the lytic pathway
• What are communicable and non-communicable diseases?

  Communicable - diseases that can be spread between individuals

  non-communicable diseases - can’t be transmitted between individuals
• What are the processes to your body fighting off pathogens in the immune response? 


  1-pathogens enter the body with some antigens

  2-pathogens come into contact with lymphocytes

  3-antibodies that match attach onto the antigens to become activated

  4-activated lymphocytes divide rapidly to produce identical copies with some antibodies

  5-some lymphocytes release antibodies into the blood

  6-the antibodies attach onto pathogens and cause them to die

  7-when all pathogens are dead a few memory lymphocytes remain in the blood
• What are the differences and similarities of sexual and asexual reproduction?

  Differences: Genetic variation, offspring number, and involvement of gametes. Similarities: Both involve reproduction and passing on genetic material. Also cell division occurs.
• Purpose of cell Wall?

  It is made of cellulose and supports the cell and strengthens it to prevent the cell bursting when water enter by osmosis
• Purpose of the nucleus


  Contains genetic material that controls the activities of the cell. Genetic material is arranged into chromosomes
• Purpose of chloroplasts 


  Where photosynthesis occurs which makes food for the plant. They contain a green substance called chlorophyll
• Purpose of ribosomes


  Involved in plant translation of genetic material in protein synthesis
• Purpose of cell membrane 


  Holds the cell together and controls what goes in and out
• Purpose of the permanent vacuole 


  Contains cell sap, a weak solution of sugar and salts. Maintains the internal pressure to support the cell
• Purpose of cytoplasm


  A gel-like substance where most of the chemical reactions happen. It contains enzymes that control these chemical reactions
• Purpose of mitochondria 


  Where most of the reactions for respiration take place. Respiration transfers energy that the cell needs to work.
• Examples of communicable diseases

  Cholera-bacterium (symptoms are diarrhoea and is contaminated via water sources)

  tuberculosis-bacterium (symptoms are coughing and lung damage and spreads through the air)

  malaria-a protist

  stomach uclers-bacterium

  ebola-virus

  cholera ash dieback-fungus infects ash trees
• Stem cells are undifferentiated meaning they don’t have a specific function or structure. they are used to replace warn out cells when they die.
• What are the differences between mitosis and meiosis 


  Mitosis: makes 2 identical daughter cells, that are diploid (46 chromosomes)

  meiosis: produces 4 genetically different cells that are gametes and are haploid (23 chromosome)
• What is the calculations for rate of an enzyme reaction

  Amount of substrate used/time taken
• Carbohydrate- breaks down carbohydrates ( amylase )

  lipase- breaks down fats

  protease- breaks down proteins
• Calculating magnification


  Size of image/actual size x magnification
• What is the structure of DNA


  -double helix

  -complimentary base pairs

  -held together by weak chemical hydrogen bonds

  —built up of nucleotides
• -A genome is made from all the chromosomes put together

  -a pair of genes is an allele

  -a small section of DNA is called a gene
• What are gametes


  They are also known as sex cells. Female gametes are called ova or egg cells and male gametes are called sperm

  they are haploid cells
• Stem cells


  Cells that can make all the cell types needed in your body
• Development of stem cells

  1. Single cell when egg and sperm join

  2. Cell divides by mitosis

  3. Hollow ball of 200-300 tiny cells

  4. Cells on inside layer can make all cell types
• Embryonic stem cells


  • Divide by mitosis so embryo grows
  • Differentiate to become specialised cells
• Adult stem cells


  More limited than embryonic stem cells
• Plant stem cells


  • In the meristem
  • Used to make clones of parent plant
• Growing embryonic stem cells in lab


  1. Scientists have found ways

  2. Trying to use them to cure conditions like diabetes

  3. Replacing insulin producing cells

  4. Regrowing spinal nerves
• Clinical challenge with embryonic stem cells

  • Encouraging them to develop into what is needed
• Embryonic stem cells


  Ethically challenging because they come from human embryos
• Adult stem cells


  • Used in bone marrow transplants
• Enzymes


  Enzymes are catalysts produced by living things and have special shoes so they can catalyse reactions
• Core practical: antibodies

  • make sure the Petri dish is covered in agar and is smooth
  • Remove a sterile pipette from the wrapper
  • open the bottle of bacterial culture and pass the neck through a flame to sterilise
  • insert the pipette and collect a small amount of the culture
  • pass the neck t the flame again
  • lift the lid of the petri dish and gently add a couple drops of the culture into the agar and place the pipette in disinfectant
  • unwrap a sterile spreader and spread the drops of culture across the agar And place lid on abd put spreader in disinfectant