biology paper 1

• Light microscope

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

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


  1. Measure image size

  2. Divide by magnification
• Eukaryotic cells

  Have a nucleus where DNA is found (e.g. plant and animal cells)
• Prokaryotic cells

  Don't have a nucleus, DNA is in a ring called a plasmid
• Subcellular structures

  • Cell membrane
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts (in plant cells)
  • Vacuole (in plant cells)
• Bacteria multiply by binary fission, doubling in number every 10 minutes
• Practical on bacterial growth

  1. Prepare agar plate with aseptic technique

  2. Incubate at 25°C

  3. Measure culture size or area of inhibition around antibiotics
• Diploid cells

  Have 23 pairs of chromosomes
• Haploid cells

  Have 23 unpaired chromosomes
• Mitosis

  1. Genetic material duplicated

  2. Nucleus breaks down

  3. Chromosomes pulled to opposite sides

  4. New nuclei form
• Specialised cells

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

  Unspecialised cells that can differentiate into various cell types
• 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 potato 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
  • Digestive
• Organs


  • Heart
  • Liver
  • Gallbladder
  • Small intestine
• Organ systems

  • Circulatory
  • Digestive
• Enzymes

  Biological catalysts that are specific to certain substrates
• Practical on enzyme activity

  1. Mix amylase and starch at different temperatures or pH

  2. Test for starch breakdown over time

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

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


  Provides oxygen for respiration, not respiration itself
• Air flow in respiratory system

  1. Trachea

  2. Bronchi

  3. Bronchioles

  4. Alveoli
• Alveoli

  Have a large surface area for fast gas exchange
• Blood flow in circulatory system

  1. Deoxygenated blood enters right atrium

  2. Pumped to lungs via pulmonary artery

  3. Oxygenated blood returns to left atrium

  4. Pumped to body via aorta
• Heart pacemaker

  Group of cells that create electrical pulses to make the heart contract
• Arteries

  Carry oxygenated blood away from the heart, have thicker walls
• Veins

  Carry deoxygenated blood towards the heart, have thinner walls and valves
• Capillaries


  Tiny blood vessels with one-cell thick walls for fast diffusion
• Coronary artery

  Supplies the heart muscle with oxygen and blood
• Stents

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

  Prevent backflow of blood
• Non-communicable diseases


  Caused by internal factors, e.g. cardiovascular disease, allergies, cancer
• Communicable diseases

  Caused by external pathogens, 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, which reduces fatty deposits