biology paper 1

• Microscopes


  Normal light microscope can see cells and nucleus, electron microscope can see subcellular structures in more detail
• Calculating cell size

  1. Measure image size

  2. Divide by magnification
• Eukaryotic cells


  Have a nucleus containing DNA
• Prokaryotic cells


  Do not have a nucleus, DNA is in a ring called a plasmid
• Cell structures


  • Cell membrane
  • Cell wall (in plants and bacteria)
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts (in plants)
• Bacterial binary fission

  1. Genetic material duplicates

  2. Cell divides into two identical cells

  3. Number of bacteria doubles every 10 minutes
• Diploid cells


  Have 23 pairs of chromosomes
• Haploid cells


  Have 23 single chromosomes
• Mitosis


  1. Genetic material duplicates

  2. Nucleus breaks down

  3. Chromosomes separate to opposite sides

  4. New nuclei form in daughter cells
• Stem cells


  • Unspecialised cells that can develop into different cell types
  • Found in embryos and meristems of plants
  • Can be used to treat conditions like diabetes and paralysis
• Diffusion

  Passive movement of molecules/particles from high to low concentration
• Osmosis

  Diffusion of water across a semi-permeable membrane
• Practical on osmosis

  1. Cut equal size vegetable cylinders

  2. Weigh and place in sugar solutions

  3. Reweigh after a day

  4. Calculate percentage change in mass

  5. Plot against sugar concentration to find no change point
• Active transport


  Using energy to move substances against a concentration gradient
• Tissues


  • Heart tissue
  • Digestive tissue
• Digestion


  1. Stomach acid breaks down food

  2. Bile and enzymes in small intestine break down further

  3. Nutrients absorbed by intestinal villi
• Enzymes


  • Biological catalysts that are specific to certain substrates
  • Work on a lock and key principle
  • Activity increases with temperature until denaturation, also affected by pH
• Practical on enzyme activity

  1. Mix amylase and starch at different temperatures or pH

  2. Test for starch presence every 10 seconds using iodine

  3. Plot time taken for starch breakdown against temperature or pH
• Food tests

  • Iodine for starch
  • Benedict's solution for sugars
  • Biuret reagent for proteins
  • Ethanol for lipids
• Breathing vs respiration

  Breathing provides oxygen for respiration to occur in cells
• Gas exchange


  1. Air enters trachea, bronchi, bronchioles, alveoli

  2. Oxygen diffuses into blood, carbon dioxide diffuses out
• Circulatory system


  • Double circulatory system - blood enters heart twice per cycle
  • Deoxygenated blood enters right side, oxygenated blood leaves left side
• Heart


  • Muscle that needs its own blood supply via coronary arteries
  • Electrical pulses from pacemaker cells cause heart to beat
• Blood vessels


  • Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood towards heart
  • Arteries have thicker walls, veins have valves
• Stents can be inserted into blocked blood vessels, statins reduce cholesterol buildup
• Non-communicable diseases


  Caused by factors within the body, e.g. cardiovascular disease, allergies, cancer
• Communicable diseases


  Caused by pathogens that can be transmitted, e.g. infectious diseases
• Coronary artery


  Delivers blood to the heart muscle to supply oxygen
• Heart attack


  Occurs when coronary arteries are blocked by buildup of fatty deposits, causing coronary heart disease (CHD)
• Stents


  Little tubes inserted into blood vessels to keep them open and allow blood flow
• Statins


  Drugs that reduce cholesterol and fatty deposits
• Faulty heart valves


  Result in backflow, can be replaced with artificial ones
• Blood


  Carries plasma, red blood cells, white blood cells (combat infections), and platelets (clot wounds)
• Cardiovascular disease (CVD)


  An example of a non-communicable disease, caused by factors within the body
• Examples of non-communicable diseases

  • Cardiovascular disease
  • Autoimmune conditions
  • Cancer
• Communicable disease


  Caused by a pathogen (virus, bacteria, fungus, or parasite) that enters the body
• Carcinogen


  Anything that increases the risk of cancer
• Benign cancer


  Doesn't spread through the body, relatively easy to treat
• Malignant cancer


  Cancerous cells spread through the body, much worse
• Leaves


  Where photosynthesis takes place, allowing transpiration