biology p1

• 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
• Subcellular structures


  • Cell membrane
  • Cell wall
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts
  • Vacuole
• Bacterial binary fission


  1. Number doubles every 10 minutes

  2. Practical: Grow culture on agar plate using aseptic technique

  3. Calculate size of culture from initial drop or area not grown
• Diploid cells

  Have 23 pairs of chromosomes
• Haploid cells

  Have 23 chromosomes (not in pairs)
• Mitosis


  1. Genetic material duplicated

  2. Nucleus breaks down

  3. Chromosomes pulled to opposite sides

  4. New nuclei form
• Specialised cell types

  • Nerve
  • Muscle
  • Root hair
  • Xylem
  • Phloem
• Stem cells

  Unspecialised cells that can differentiate
• Diffusion

  Movement of molecules/particles from high to low concentration, passive process
• Osmosis

  Diffusion of water across a semi-permeable membrane
• Practical: Osmosis

  1. Cut potato cylinders

  2. Weigh and place in sugar solutions

  3. Reweigh after a day

  4. Calculate % change in mass

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

  Using energy to move substances against a concentration gradient
• Digestive system processes


  • Acid in stomach
  • Bile and enzymes in small intestine
  • Emulsification of fats
• Enzymes


  Biological catalysts, specific to certain substrates, work on a lock and key principle
• Practical: Enzyme activity

  1. Mix amylase and starch

  2. Test for starch every 10 seconds with iodine

  3. Plot time taken for starch to be broken down against temperature or pH

  4. Find optimum temperature or pH
• Food tests

  • Iodine for starch
  • Benedict's solution for sugars
  • Biuret's reagent for proteins
  • Ethanol for lipids
• Respiration


  Provides energy for cells, different from breathing
• Gas exchange


  1. Air moves down trachea, bronchi, bronchioles to alveoli

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


  Double circulatory system, deoxygenated blood enters right side of heart, oxygenated blood leaves left side
• Heart structure


  • Right atrium and ventricle, left atrium and ventricle
  • Pacemaker cells create electrical pulses to make heart contract
• Blood vessels


  • Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood towards heart
  • Capillaries allow fast diffusion
• Coronary artery


  Supplies heart muscle with oxygen and nutrients
• Stents


  Tubes inserted into blood vessels to keep them open
• Heart valves


  Can be replaced with artificial ones
• Non-communicable diseases


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


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


  Delivers blood to the heart muscle to supply oxygen
• Coronary heart disease (CHD)


  Occurs when coronary arteries are blocked by fatty deposits, causing a heart attack
• Stents


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


  Drugs that reduce cholesterol and fatty deposits
• Heart valve replacement


  Artificial valves can replace faulty ones to prevent backflow
• Blood


  Carries oxygen, nutrients, white blood cells, and platelets
• Cardiovascular disease (CVD)


  Non-communicable disease caused by factors within the body, e.g. obesity, diet, smoking
• Communicable disease


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


  Anything that increases the risk of cancer, e.g. ionizing radiation
• Benign cancer


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


  Cancerous cells spread through the body, much worse