Biology paper 1

• Communicable diseases can be spread from one person to another by pathogens

  non communicable diseases cannot be spread
• Pathogen is an organism that causes disease
• Black rose spot is caused by a fungus

  symptoms are black spots on leaves and leaves may turn yellow and fall off

  reduces plant growth due to lack of chlorophyll so it cannot photosynthesise

  can be prevented by chemical fungicides
• Tobacco mosaic virus

  symptom is mosaic pattern on leaves by discolouration

  reduces plant growth due to lack of chlorophyll so it can’t photosynthesise

  no treatment but good field hygiene and pest control can help prevent spread
• Plant pathogen transmission

  -in the air

  -by direct contact eg. Pests act as vectors

  -in water
• Uses of glucose

  -oils for germination

  -respiration for energy

  -amino acids for protein for growth

  -starch

  -cellulose for cell walls
• Nitrate ions are needed to make sugar for protein for growth (amino acids)

  a lack will limit plant growth due to less protein
• Magnesium ions are needed to make chlorophyll needed for photosynthesis

  a lack of this will make leaves turn yellow and growth slows as it cannot photosynthesise
• symptoms of disease in plants

  -lack of growth

  -spotted leaves

  -areas of rotting

  -growths

  -malformed stems and leaves

  -discolouration

  -visable pests eg. Aphids
• Plant physical defences/barriers

  -cell wall made of cellulose

  -waxy cuticle

  -bark on trees

  -leaves fall

  chemical barriers

  -natural antibiotics
• Plant defences against herbivores

  —curling leaves

  -mimicry

  -thorns

  -poison

  -hairy leaves
• Factors that affect human health

  • diet
  • genetics
  • disease
  • lifestyle
  • location
• Transmission of human disease

  • droplets from breathing
  • direct contact : sexual contact , cuts/needles give access to blood
  • contaminated food and water enters the digestive system
• Preventing infection

  • hygiene: wash hands, wear mask
  • isolation
  • controlling vectors
  • vaccination
• Viruses invade living cells and incorporate their dna in that host cell to reproduce and leave the cell, destroying it
• Measles

  symptoms may be a fever, red skin rash

  transmitted by inhalation of droplets from coughing

  no treatment they must be isolated but there is a children vaccination scheme
• HIV

  -symptoms may be a flu like illness and weak immune system

  -transmitted by sexual contact, exchange bodily fluids eg needles, or mother to child breastfeeding

  -prevented with condoms or not sharing needles

  -treatment of antiretroviral drugs
• Salmonella-bacterial

  -symptoms could be fever,cramps,vomiting

  -transmitted by raw meat containing the bacteria

  -prevented by cooking chicken thoroughly and washing hands and surfaces

  -treated with vaccinating poultry
• Gonorrhoea-bacterial

  -transmitted by sex

  -symptoms: thick yellow discharge ,pain urinating ,infertility

  -using a condom

  -treatment using antibiotics
• Malaria

  caused by protists

  transmitted by mosquitos as a vector

  prevent by using insecticide, mosquito nets

  symptoms of fever and chills
• Infectious diseases can spread rapidly due to high population density and poor hygiene
• The immune response involves phagocytes engulfing pathogens and lymphocytes producing antibodies which bind to specific antigens on the surface of pathogens
• body defences to infection

  • platelets clot blood forming scabs
  • skin
  • stomach acid
  • cilia and mucus in the trachea
• How white blood cells destroy pathogens

  • ingesting the pathogen and destroying it
  • producing antibodies specific to kill a certain pathogen
  • producing antitoxins to neutralise pathogens
• -A vaccine is a dead pathogen injected in the body

  -wbc produce specific antibodies to destroy it

  -memory cells form

  -when the alive pathogen invades the body, memory cells rapidly produce the specific antibody in large numbers

  -this destroys it before symptoms can occur
• Antibiotics only kill bacteria

  painkillers treat the symptoms of a diease
• -Aspirin is made from willow tree bark, it is a painkiller and has anti inflammatory properties

  -digitalis is made from foxgloves to treat heart failure

  -penecillin(made by alexander flemming) is made from penicillium (mould) and it is an antibiotic
• What are drugs tested for:

  • toxicity
  • efficacy
  • dosage
  • stability
  • successful uptake/removal
• drug development

  • in a lab on cells/tissues/organs for efficacy and toxicity
  • in a lab on animals for side effects
  • in a hospital on small group of healthy volunteers for side effects and safe dosage
  • tested on larger number of patient volunteers for optimum dosage and efficacy
  • large scale trial and a placebo is used and it it double blind
  • drug is peer reviewed to avoid bias and can then be prescribed
• Producing monoclonal antibodies

  • inject mouse with specific antigen
  • collect blood from the mouse and extract B lymphocytes
  • fuse together the B cells with cancer cells to create hybridoma cells
  • hybridomas replicate, producing many clones each with the same specific monoclonal antibody
• Monoclonal antibodies used to treat disease

  • direct use of monoclonal antibodies to trigger immune response
  • used to block receptors on surface of cancer cells, stopping cell growth and division
  • used to carry toxic drugs to stop cell division, attacks cancer cells directly without harming other body cells
• Monoclonal antibody advantages:

  • only bind to specific damaged cells
  • treats a wide variety if conditions

  monoclonal antibody disadvantages

  • very expensive to develop
  • can create side effects due to use of mouse cells due to their antibodies trigger an immune response in humans
• Pregnancy test

  • urine applied to sample pad- contains hcg if pregnant
  • hcg binds to mobile antibodies that have an enzyme attached to them
  • immobilised antibodies in test zone bind to hcg
  • enzyme on first antibody changed test line colour
  • excess antibodies bind to immobilised antibodies in control zone to show if test worked properly
• Cell cycle

  • growth- Cells grow, dna replicates and more organelles are made
  • Mitosis- chromosomes are pulled to each end of dividing cell and nucleus divides
  • new cells- cytoplasm and cellmembranes divide, and two genetically identical daughter cells are made
• Causes of cancer

  • genetic
  • mutation -change in genes
  • ionising radiation -changes genes
  • viruses
• Benign tumour- non-cancerous, not spread to other parts of the body but is an abnormal group of cells

  malignant tumour- cancerous, spreads to other parts of the body and invades other cells, moves in the blood
• Benefits of regular exercise

  • fitter hearts
  • bigger lungs
  • muscles respire more
• A stem cell is an undifferentiated cell that has the ability to differentiate into a specialised cell
• Adult stem cells:

  • can only differentiate into certain cell types
  • found in various body tissues
  • no ethical issue

  embryonic stem cells:

  • can differentiate into any cell type
  • found in the embryo
  • ethical issues regarding destruction of embroyos
• Stomach structure:

  • epithelial tissue protects the organ and is an effective exchange surface
  • glandular tissue secretes enzymes and hormones
  • muscular tissue contracts to churn food