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. Ribosomes and mitochondria doubled

  3. Nucleus breaks down

  4. Chromosomes pulled to opposite sides

  5. New nuclei form
• Specialised cell types

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

  Unspecialised 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
• Practical: Investigating enzyme activity

  1. Mix amylase and starch at different temperatures or pH

  2. Test for starch presence with iodine every 10 seconds

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

  Iodine for starch

  Benedict's solution for sugars

  Biuret's reagent for proteins

  Ethanol for lipids
• Breathing and gas exchange

  Air moves down trachea, bronchi, bronchioles to alveoli

  Oxygen diffuses into blood, carbon dioxide diffuses out
• Parts of the circulatory system

  • Right atrium
  • Right ventricle
  • Pulmonary artery
  • Pulmonary vein
  • Left atrium
  • Left ventricle
  • Aorta
• Coronary artery

  Supplies blood to the heart muscle
• Stents

  Tubes inserted into blood vessels to keep them open
• Statins

  Drugs that reduce cholesterol and fatty deposits
• Types of disease

  • Non-communicable diseases (e.g. cardiovascular disease, cancer)

  Communicable diseases (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
• Stent

  A small tube inserted into blood vessels to keep them open and allow blood flow
• 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
• Benign cancer

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

  Cancerous cells spread through the body, much worse