paper 1 Biology

• 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 growth area or calculate population size
• 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 cells
  • Muscle cells
  • Root hair cells
  • Xylem cells
  • Phloem cells
• 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 tissue
  • Digestive tissue
• Organs


  • Heart
  • Liver
  • Gallbladder
• Organ systems


  • Circulatory system
  • Digestive system
  • Nervous system
  • Respiratory system
• Enzymes


  Biological catalysts that break down larger molecules into smaller ones
• Enzyme specificity


  Enzymes only work on certain substrates due to the lock and key principle
• Enzyme activity


  Increases with temperature until denaturation, has an optimum pH and temperature
• Practical on enzyme activity

  1. Mix amylase and starch at different temperatures or pH

  2. Test for starch presence over time

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


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


  Provides oxygen for respiration, not the same as respiration
• Gas exchange in the lungs

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

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


  Blood enters the heart twice on each circuit around the body
• Blood vessel types


  • Arteries (carry oxygenated blood, thicker walls)
  • Veins (carry deoxygenated blood, thinner walls with valves)
• Coronary arteries supply the heart muscle with oxygen and nutrients
• Stents


  Tubes inserted into blood vessels to keep them open
• Non-communicable diseases

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

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


  Delivers blood to the heart muscle to supply oxygen
• Heart attack

  Caused by blockage of coronary arteries, also known as coronary heart disease (CHD)
• Stents


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


  Drugs that reduce cholesterol and fatty deposits
• Heart valves


  Can become faulty, leading to backflow, and may need to be replaced with artificial ones
• 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