Biology paper 1

• Light microscope


  Can see cells and maybe the nucleus, but not subcellular structures
• Electron microscope


  Can see much finer details and subcellular structures, has better resolving power and higher resolution
• Calculating cell size


  1. Measure image size

  2. Divide by magnification
• Cell types


  • Eukaryotic cells
  • Prokaryotic cells
• Eukaryotic cells


  • Have a nucleus where DNA is found
• Prokaryotic cells


  • Don't 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. After 1 hour, 64 bacteria

  3. After 6 hours, 6.87 x 10^10 bacteria
• Practical: Bacterial culture on agar

  1. Use aseptic technique

  2. Lift lid towards flame

  3. Use sterilized equipment

  4. Incubate at 25°C
• Measuring bacterial culture


  1. Calculate size from initial drop or area where bacteria did not grow

  2. Use πr^2 or πd^2/4 to calculate area
• Human cells


  • Have 23 pairs of chromosomes (diploid)

  Gametes have 23 chromosomes (haploid)
• Cell division by mitosis

  1. Genetic material duplicated

  2. Nucleus breaks down

  3. Chromosomes pulled to opposite sides

  4. New nuclei form in each cell
• Specialized cell types


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


  Unspecialized cells that can differentiate into various cell types
• Diffusion


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


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

  1. Cut equal size cylinders

  2. Weigh and place in sugar solutions

  3. Reweigh after a day

  4. Calculate percentage change in mass

  5. Plot against sugar concentration
• Active transport


  Using energy to move substances against a concentration gradient
• Tissues


  • Heart tissue
  • Digestive tissue
• Organs


  • Heart
  • Liver
  • Gallbladder
• Organ systems


  • Circulatory system
  • Digestive system
• Enzymes


  Biological catalysts that break down larger molecules into smaller ones

  Work on a lock and key principle with specific substrates

  Rate increases with temperature until denaturation, also affected by pH
• Practical: Investigating enzyme activity

  1. Mix amylase and starch at different temperatures or pH

  2. Test for starch breakdown over time using iodine

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


  Iodine for starch

  Benedict's solution for sugars

  Biuret's reagent for proteins

  Ethanol for lipids
• Respiratory system structures


  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli
• Breathing vs respiration


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

  Oxygen diffuses into blood vessels

  Carbon dioxide diffuses out
• Components of blood


  • Red blood cells

  Plasma

  White blood cells

  Platelets
• Double circulatory system


  Blood enters the heart twice per cycle

  Deoxygenated blood enters right side, oxygenated blood leaves left side
• Heart structure


  • Right atrium and ventricle

  Left atrium and ventricle

  Valves to prevent backflow

  Coronary arteries supply heart muscle
• Cardiovascular disease


  Non-communicable disease caused by factors within the body

  Examples include coronary heart disease and faulty heart valves
• 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
• Stent


  A small tube 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
• Cardiovascular (CV) disease


  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 that enters the body, resulting in viral, bacterial or fungal infection
• Carcinogen


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