biology p1

• Eukaryotic cells


  Plant and animal cells
• Features of eukaryotic cells

  • Cell membrane
  • Cytoplasm
  • Genetic material enclosed in a nucleus
  • Ribosomes
  • Mitochondria
• Features only found in plant cells


  • Chloroplasts
  • Permanent vacuole filled with cell sap
  • Cellulose cell wall

  
• Stages of mitosis


  1. Cell growth and increase in mitochondria and ribosomes

  2. DNA replication to form 2 copies of each chromosome

  3. One set of chromosomes pulled to each end of the cell and nucleus divides

  4. Cytoplasm and cell membranes divide to form 2 identical cells
• Stem cell


  An unspecialised cell that can turn into any specialised cell
• Function of stem cells

  To differentiate into different types of cells for cell replacement and repair
• Sources of stem cells

  • Embryos
  • Bone marrow in mammals
  • Meristem tissue in plants
• Uses of stem cells


  • Medically to help with conditions such as diabetes and paralysis
  • To clone plants quickly and economically
• Issues with using stem cells

  • Transfer of viral infections
  • Risk of becoming cancerous
  • Ethical or religious objections (especially to the use of embryos)
• Binary fission


  A type of simple cell division in bacteria
• Aseptic technique


  Making sure all equipment is sterilised before using it to transfer or grow bacteria so no contamination occurs
• Examples of aseptic technique


  • Use a sterile petri dish and sterile agar
  • Sterilise loops by passing them through a flame
  • Only open plate when transferring bacteria
• To grow bacteria safely in school: Tape the lid of the petri dish closed, grow it at 25ºC (to prevent growth of harmful bacteria which grow at body temperature, 37º)
• Diffusion


  The spreading out of the particles from an area of higher concentration to an area of lower concentration. It is a passive process (needs no energy).
• Factors affecting rate of diffusion

  • Temperature
  • Concentration gradient
  • Surface area of the membrane
• Examples of substances diffused in organisms

  • Oxygen in, carbon dioxide out (animal cells)
  • Carbon dioxide out, oxygen in (plant cells)
  • Glucose in (animal cells)
• Adaptations to maximise diffusion

  • Large surface area
  • Thin membrane (for short diffusion pathway)
  • Good blood supply
  • Ventilation (movement of air or water)
• Osmosis


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


  Moves substances from an area of lower concentration to an area of higher concentration (against the concentration gradient). Requires energy from respiration.
• Examples of substances actively transported

  • Glucose (in the small intestine of animals)
  • Mineral ions (in plant root hair cells)

  
• Hierarchy of organisation in living organisms

  • Cell
  • Tissue
  • Organs
  • Organ Systems
  • Organisms
• Organs involved in digestion

  • Mouth
  • Oesophagus
  • Stomach
  • Pancreas
  • Small intestine
  • Large intestine
  • Liver
  • Gall bladder
• Enzyme


  A biological catalyst, which speeds up chemical reactions in an organism
• "Lock and key" theory

  Only molecules which are the correct shape can fit into the active site of the enzyme so only that reaction is affected by the enzyme
• Where enzymes are made

  • Salivary glands (amylase)
  • Pancreas (amylase, protease, lipase)
  • Stomach (protease)
  • Small intestine (protease, lipase)
• Where enzymes act


  • Mouth (amylase)
  • Small intestine (amylase, protease, lipase)
  • Stomach (protease)
• How amylase digests food

  It breaks down starch into simple sugars which are small enough to pass into the bloodstream
• How protease digests food

  They break down proteins into amino acids which are small enough to pass into the bloodstream
• How lipase digests food


  They break down fats into fatty acids and glycerol which are small enough to pass into the bloodstream
• Organs involved in bile production and storage

  • Liver (produces bile)
  • Gall bladder (stores bile)
• Function of bile


  It is alkaline to neutralise hydrochloric acid from the stomach. It also emulsifies fat to form small droplets which increases the surface area. The alkaline conditions and large surface area increase the rate of fat breakdown by lipase.
• Factors affecting enzyme activity

  • Temperature
  • pH
• Effect of temperature on enzyme activity

  A small increase in temperature can increase enzyme action as the substrate collides with the active site more often. High temperatures can denature enzymes, changing the shape of the active site so the substrate no longer fits.
• Effect of pH on enzyme activity

  pH changes can denature enzymes, changing the shape of the active site so the substrate no longer fits.
• Tests for biological molecules

  • Sugar - Benedict's solution goes from blue to brick red
  • Starch - Iodine solution goes from orange to blue-black
  • Protein - Biuret reagent goes from blue to lilac
  • Lipids - Emulsion test (adding ethanol then water gives a cloudy white suspension)
• Flow of blood through the heart

  Vena Cava (from the body) -> Right Atrium -> Right Ventricle -> Pulmonary Artery (to the lungs) -> Pulmonary Vein (from the lungs) -> Left Atrium -> Left Ventricle -> Aorta (to the body)
• Types of blood vessel

  • Arteries (carry blood away from the heart)
  • Capillaries (tiny vessels found inside the tissues)
  • Veins (carry blood back towards the heart)
• Function of coronary artery

  Supplies blood containing oxygen and glucose to the heart muscle cells so they can respire
• Valve


  Prevents blood flowing in the wrong direction. Found in the heart and in veins.
• Pacemaker


  Controls the heart rate (one is naturally in the heart or artificial ones can be fitted by doctors)