Biology paper 1

• Stages of the cell cycle (mitosis)

  • stage 1- sub cellular structures replicate
  • stage 2-one of the pairs chromosome split and pulled to opposite ends of the cell
  • cytoplasm Divides and new cell membrane is formed around each. producing two identical daughter cells
• lock and key 


  emzyme active site binds to substrate as they are complementary.

  substrate is broken down into products

  enzyme is not changed
• enzymes are biological catalysts
• catalyst - substance that speeds up chemical reactions without being used up or changing itself.
• active site - where enzymes react with their substrates
• How to plants store excess glucose

  As starch
• How is a bacteria benefitted from living inside organisms

  Obtain glucose from the organism.

  that Glucose is then used for respiration
• What are nitrate ions used for In plants

  Needed to make proteins for growth
• Effects of liver failure

  • No bile made , so can’t emulsify fats or produce optimum ph for enzymes to work in so problems with digestion
  • protiens/ amino acids will not be broken down (into ammonia then urea for removal) so there will be an accumulation of amino acids In the blood
  • liver doesn’t filter/ remove toxins in the blood Eg (ammonia and alcohol) so body will be poisoned
• Clinical trials on people

  Give low dose to check

  toxicity

  then test on patients with the disease to check

  optimum dose

  toxicity/ side effects

  use a double blind Trial with real drug and placebo drug
• virus

  Tiny pathogens, live inside body cells using the cells machinery to multiply. cause cell to burst which causes illness

  cannot be killed by antibiotics
• What Is a pathogen

  Microorganism that can cause disease
• Ways pathogens can be spread

  Air droplets

  water

  direct contact
• types of pathogens

  Bacteria

  virus

  protist

  fungi
• Bacteria 


  Small cells that produce toxins
• Protists 


  Often parasites ( live on or inside another organism) often transferred to the organism by a vector eg. Inspect that carries protist
• Fungi

  Produce spores which can be spread to other plants and animals
• Viral diseases

  Measles (skin rash)

  HIV (weaknes immune system and turns into aids)

  tobacco mosaic virus (TMV) causes discolouration
• fungal disease

  Rose black spot

  causes purple black spots, means less photosynthesis

  spreads through environment by wind

  treated by fungicides
• measles 


  Viral disease

  • spread by droplets
  • red skin rash and fever and serious cases effect brain and become fatal
  • most people vaccinated is treatment
• HIV

  • virus spread by exchanging body fluids (often sexual contact)
  • attacks immune system ( easily die from little disease as weak immune system)
  • treated with antiretroviral
• TMV

  • causes discolouration, means can’t carry out photosynthesis effectively so not good growth
• Malaria


  Protist disease

  - fever (it can be fatal)

  • stop mosquitoes from breeding
• Bacterial diseases

  Salmonella

  gonorrhoea
• Salmonella

  • fever caused by toxins that bacteria produce
  • treated by vaccinating poultry
• gonorrhoea

  • Std
  • pain when urinating, yellow discharge
  • use barrier methods such As condoms
• Body defence systems

  • Skin
  • hairs and mucus
  • stomach acid
  • immune system attacks them
• White blood cells react to pathogens in body

  • release antitoxins
  • release antibodies (specifically produced to lock into the antigen of pathogen so they can be found and destroyed by white blood cells)
  • engulf and digest them, phagocytosis
• vaccine

  • inject dead/inactive pathogens.
  • antibodies are produced which bind to antigen of pathogen
  • if real pathogen infects then antibodies produced rapidly
• Antibiotics

  Kill bacteria

  cant kill virus Also bacteria can become resistant to the antibiotic
• monoclonal antibodies

  • produced by B-lymphocytes ( type of white blood cell)
  • all antibodies produced by the B-lymphocyte are identical also and bind to identical antigens on pathogens
  • however b-lymphocytes divide very slowly, so they are fused with tumour cells. this is called a hybridoma
  • all these antibodies produced will only target one specific antigen
• Uses of monoclonal antibodies

  Pregnancy test.

  antibodies have dye on them and binds to the hormone that indicates pregNancy.

  then travels down the stick to the test strip where antibodies and stuck down.

  if pregnant the hormones will bind to the test strip and because the hormones are binded to the blue dye through antibodies also the test strip is blue
• Monoclonal antibodies uses

  Treat specific diseases eg. Cancer

  an anticancer drug can be attached to the antibodies. Then when delivered into the body the monoclonal antibodies will bind the spefic cancer cells antigen and basically deliver the drug right to the cell. which reduces the damgae to other cells around it which is caused by alternative treatments
• Monoclonal antibodies negative

  Do have more side effects than expected

  eg. Fever vommiting
• What mineral ions do plants need

  • nitrate ions (needed to make proteins for growth) a lack would lead to stunted growth
  • magnesium ions ( needed to make chlorophyll for photosyntheis) a lack would lead to yellow leaves
• plants defences

  Physical (waxy cuticle, cell walls, bark

  chemical (poison, antibacterial chemicals)

  mechanical (thorns, droop or curl, mimicry eg. White spots to mimic butterfly eggs. some look like stones
• process that cells go though to become specialised

  Differentiation
• Sperm cells adaptations

  -enzyme in head (digest cell membrane of egg)

  -long tail and streamline head help it swim to egg

  -lots of mitochondria to provide energy to move
• Nerve cells

  carries electrical signals from one part of the body to another.

  -cells are long (cover more distance) and have branched connections, to form a network throughout the body
• Muscle cells

  function is to contact quickly

  -long (so have space to contact)

  -contain lots of mitochondria to generate the energy needed for contraction