Biology paper 1

• Microscopes


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


  Image size / Object size
• Cell types


  • Eukaryotic cells (have nucleus)
  • Prokaryotic cells (no nucleus)
• Eukaryotic cells


  • DNA is found in the nucleus
  • Examples: plant and animal cells
• Prokaryotic cells


  • DNA is found in a ring called a plasmid
  • No nucleus
• Cell structures


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


  1. Number of bacteria doubles every 10 minutes

  2. After 1 hour: 2^6 = 64 bacteria

  3. After 6 hours: 2^36 = 6.87 x 10^10 bacteria
• Diploid cells


  Cells with 23 pairs of chromosomes (e.g. human body cells)
• Haploid cells


  Cells with 23 single chromosomes (e.g. human gametes)
• Mitosis


  1. Genetic material is duplicated

  2. Nucleus breaks down

  3. Chromosomes move to opposite sides

  4. New nuclei form in the two new cells
• Specialised cell types


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


  Unspecialised cells that can develop into different cell types
• Diffusion


  Movement of molecules/particles from high to low concentration, no energy required
• Osmosis


  Diffusion of water across a semi-permeable membrane
• Factors affecting diffusion/osmosis rate

  • Concentration gradient
  • Temperature
  • Surface area
• Practical: Osmosis in potato cylinders

  1. Cut equal size potato cylinders

  2. Weigh and place in sugar solutions

  3. Reweigh after 1 day

  4. Calculate % change in mass

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


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


  • Stomach acid breaks down food
  • Bile emulsifies fats
  • Enzymes break down food into small molecules
• Enzymes


  Biological catalysts that are specific to certain substrates
• Enzyme activity


  • Increases with temperature until denaturation
  • Optimum pH and temperature for maximum activity
• Practical: Investigating enzyme activity

  1. Mix amylase and starch at different temperatures or pH

  2. Test for starch presence over time using iodine

  3. Plot time taken to break down starch against temperature or pH
• Food tests


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


  • Provides oxygen for respiration
  • Air moves through trachea, bronchi, bronchioles, alveoli
• Circulatory system


  • Double circulatory system - blood passes through heart twice per cycle
  • Arteries carry oxygenated blood, veins carry deoxygenated blood
  • Capillaries allow gas exchange
• Heart pacemaker


  Group of cells that create electrical pulses to make the heart contract
• Coronary artery blockage


  Can cause heart attack (CHD)
• Stents are tubes inserted into blood vessels to keep them open
• Heart valves can be replaced with artificial ones
• Cardiovascular disease (CVD)


  Non-communicable disease caused by factors within the body
• Other non-communicable diseases include autoimmune conditions and cancer
• 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, which reduces fatty deposits
• Heart valves


  Can become faulty, resulting in backflow, and may need to be replaced with artificial ones
• Blood


  Carries oxygen, nutrients, white blood cells to combat infections, and platelets to 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