Biology paper 1

• Pathogens


  A micro-organism that causes a disease
• Main types of pathogens

  • Bacteria
  • Fungi
  • Viruses
  • Protists
• How pathogens spread

  1. Cough/sneeze

  2. Infected needles

  3. Food/water

  4. Animal bites
• Viral diseases

  Caused by a virus that replicates by invading our cells, causing the cells to burst and release new viruses, making us ill
• Viral diseases


  • Measles
  • Tobacco Mosaic virus
  • HIV
• Viruses cannot reproduce by themselves, they need a host
• Bacterial diseases


  Bacteria reproduce rapidly inside the human body and can release harmful toxins that damage tissues and make us ill
• Bacterial diseases


  • Salmonella
  • Gonorrhoea
• Communicable diseases

  Diseases spread by pathogens such as bacteria or viruses from person to person
• Non-communicable diseases


  Diseases that cannot be passed from person to person, e.g. coronary heart disease
• Phagocytosis


  White blood cells detect chemicals from pathogens, move towards them, ingest them, and use enzymes to destroy them
• Blood vessels

  • Arteries take blood from the heart to organs, have thick walls
  • Veins take blood from organs to the heart, have thin walls and valves
  • Capillaries allow substances to pass in and out of the blood
• Antibodies

  Protein molecules produced by white blood cells that stick to pathogens and destroy them
• Antitoxins


  Stick to toxin molecules and prevent them from damaging cells
• Non-specific defence systems


  • Skin
  • Nose
  • Lungs
  • Stomach
• Antibiotics


  Kill infective bacteria inside the body, e.g. penicillin discovered by Alexander Fleming
• Vaccination


  Small amounts of dead/inactive pathogens are put into the body, stimulating white blood cells to make antibodies that can rapidly respond to future infections
• Antigen


  A unique protein found on the surface of a pathogen
• Rose black spot


  A fungal disease that causes leaves to develop purple/black spots, turn yellow, and fall off, reducing the rate of photosynthesis and growth
• Treatment for rose black spot

  Spray plants with chemicals that kill fungi, remove infected plants
• Testing medicines


  1. Preclinical testing on cells, tissues, live animals

  2. Clinical testing with a dummy drug, double-blind test
• Animal cells


  • Cytoplasm where chemical reactions take place
  • Cell membrane controls what enters and leaves
  • Mitochondria where aerobic respiration takes place
  • Ribosomes where protein synthesis occurs
• Plant cells


  • Chloroplasts contain chlorophyll and photosynthesis takes place
  • Cell wall made of cellulose, strengthens the cell
  • Vacuole filled with cell sap, helps give the cell shape/structure
• Nerve cells


  • Axon carries electrical impulses, dendrites increase surface area
  • Synapses allow impulses to pass from one nerve cell to another
• Muscle cells


  • Contain protein fibres that can change length, packed with mitochondria to provide energy for contraction
• Root cells


  • Hairs increase surface area to absorb water and minerals, do not contain chloroplasts
• Xylem


  • Long tubes found in plant stems with very thick walls to provide support
• Using a microscope


  Place slide on stage, use lowest power objective lens, focus using coarse then fine adjustment
• Diffusion


  The spreading of particles from an area of high to low concentration
• Factors affecting diffusion rate

  Higher temperature, greater surface area
• Cell division


  DNA replicates, mitosis occurs, cytoplasm and cell membrane divide to form two identical cells
• Osmosis


  The diffusion of water from a dilute to a concentrated solution through a partially permeable membrane
• Active transport


  Moves substances from a more dilute to a more concentrated solution, requires energy from respiration
• Digestive system


  Food is chewed in mouth, enzymes in saliva digest starch, food goes to stomach where hydrochloric acid digests proteins, then to small and large intestine
• Enzymes


  Speed up chemical reactions
• Bile


  Helps speed up digestion of lipids, is also an alkaline
• Food tests


  Test for starch with iodine, test for sugar with Benedict's solution, test for protein with biuret
• Circulatory system


  Blood is pumped from heart to lungs to collect oxygen, then back to heart and around body
• Blood vessels


  • Arteries have thick muscular walls, veins have thin walls and valves
• Blood components


  • Plasma transports substances, red blood cells transport oxygen