GCSE SCIENCE BIO AQA

• 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. Practical: Grow bacterial culture on agar plate, use aseptic technique, incubate at 25°C, calculate culture size or area of antibiotic inhibition
• Diploid cells


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


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


  1. Genetic material is duplicated

  2. Nucleus breaks down

  3. Chromosomes pulled to opposite sides

  4. New nuclei form in each new cell
• Cell specialisation


  • Cells specialize to perform specific functions (e.g. nerve, muscle, root hair cells)
  • Stem cells are unspecialized
• Diffusion


  Passive movement of molecules/particles from high to low concentration
• Osmosis


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

  Increased concentration difference, temperature, surface area
• Practical: Osmosis in potato cylinders

  Cut equal size potato cylinders, weigh, place in sugar solutions, reweigh after a day, calculate % change in mass, plot against concentration
• Active transport


  Using energy to move substances against a concentration gradient
• Tissues and organs


  • Tissues (e.g. heart tissue)
  • Organs (e.g. heart, liver, stomach)
  • Organ systems (e.g. circulatory, digestive)
• Enzymes


  Biological catalysts that are specific to certain substrates, work on a lock and key principle
• Factors affecting enzyme activity

  Increased temperature (up to optimum) and pH (within optimal range) increase rate
• Practical: Investigating enzyme activity

  Mix amylase and starch at different temperatures/pH, test for starch presence over time, plot time taken to break down starch
• 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
  • Oxygen diffuses into blood, carbon dioxide diffuses out
• Circulatory system


  • Double circulatory system, deoxygenated blood enters right side of heart, oxygenated blood leaves left side
  • Heart has thicker left ventricle wall, pacemaker regulates heartbeat
  • Arteries carry oxygenated blood, veins carry deoxygenated blood, capillaries allow gas exchange
• Coronary arteries supply the heart muscle with oxygen, blockages can cause heart attacks
• Stents


  Tubes inserted into blood vessels to keep them open
• Statins


  Drugs that reduce cholesterol and fatty deposits
• Faulty heart valves can cause backflow, these can be replaced with artificial valves
• Non-communicable diseases


  Diseases caused by internal factors, not transmitted between people (e.g. cardiovascular disease, cancer, allergies)
• Communicable diseases are transmitted between people
• 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
• Stents


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


  Drugs that reduce cholesterol, which in turn reduces fatty deposits
• Faulty heart valves


  Result in backflow, can be replaced with artificial ones
• Blood


  Carries plasma, red blood cells, white blood cells, and platelets
• White blood cells


  Combat infections
• Platelets


  Clump together to clot wounds and stop bleeding
• Cardiovascular disease (CVD)


  An example of a non-communicable disease, caused by factors within the body
• Communicable disease


  Caused by a pathogen that enters the body, can be viral, bacterial, or fungal
• Type 2 diabetes


  Can be caused by obesity and too much sugar