biology paper 1

• Cells


  Can be seen with a normal light microscope, but subcellular structures are not visible. Electron microscopes have better resolving power and resolution to see finer details.
• Cell size


  Can be calculated by knowing the magnification of the microscope: Magnification = Image size / Object size
• Cell types


  • Eukaryotic cells (have a nucleus)
  • Prokaryotic cells (no nucleus, DNA in a ring called a plasmid)
• Eukaryotic and prokaryotic cells


  • Contain similar organelles or subcellular structures
• Cell membrane


  • Keeps everything inside the cell, semi-permeable to allow certain substances to pass through
• Plant cells and most bacteria

  • Have an extra cell wall made of cellulose, providing a rigid structure
• Cytoplasm


  The liquid that makes up the cell, where most chemical reactions take place
• Mitochondria


  • Where respiration takes place, releasing energy for the cell to function
• Ribosomes


  • Where proteins are assembled or synthesized
• Plant cells


  • Contain chloroplasts with chlorophyll, where photosynthesis takes place
  • Contain a permanent vacuole to store sap
• Bacterial multiplication


  1. Binary fission, number doubles every 10 minutes

  2. Can be demonstrated through a practical using agar in a Petri dish and aseptic technique
• Diploid cells


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


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


  Mitosis: Genetic material is duplicated, number of ribosomes and mitochondria is doubled, nucleus breaks down, chromosomes are pulled to opposite sides, new nuclei form in the two identical cells
• Cell specialization


  • Cells specialize to fulfill different functions (e.g. nerve, muscle, root hair, xylem, phloem, stem cells)
• Stem cells


  Unspecialized cells that can differentiate into various cell types, found in embryos and bone marrow
• Diffusion


  The movement of molecules or particles from an area of high concentration to an area of low concentration, down the concentration gradient, without requiring energy input
• Osmosis


  The diffusion of water across a semi-permeable membrane, from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration)
• Factors affecting diffusion and osmosis rates

  Increased concentration difference, temperature, or surface area
• Practical on osmosis


  Cut equal-size vegetable cylinders, weigh, place in varying sugar solutions, reweigh after a day, calculate percentage change in mass, plot against sugar concentration to find the concentration with no change (same as inside the cells)
• Active transport


  The movement of substances through a membrane against a concentration gradient, using energy
• Tissues


  Groups of similar cells connected and working together
• Organs


  Groups of tissues working together to perform a specific function
• Organ systems


  Groups of organs working together (e.g. circulatory, digestive)
• Digestion


  Stomach acid breaks down food, bile and enzymes in small intestine further break down nutrients, which are then absorbed by the villi
• Enzymes


  Biological catalysts that break down larger molecules into smaller ones, specific to certain substrates due to the lock-and-key principle
• Factors affecting enzyme activity

  Temperature and pH - maximum rate at optimum temperature and pH, denaturation at too high or too low values
• Practical on enzyme activity

  Mix amylase with starch at different temperatures or pH, time how long it takes for all starch to be broken down, plot a curve to find the optimum
• Food tests


  Iodine for starch, Benedict's solution for sugars, Biuret's reagent for proteins, ethanol for lipids
• Breathing vs respiration


  Breathing provides oxygen for respiration to occur in cells
• Respiratory system


  • Air moves down trachea, bronchi, bronchioles to alveoli where gas exchange occurs, oxygen binds to hemoglobin in red blood cells, carbon dioxide is exhaled
• Circulatory system


  • Double circulatory system, deoxygenated blood enters right side of heart, goes to lungs, oxygenated blood returns to left side and is pumped to body, coronary arteries supply heart muscle
• Blood vessels


  Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood towards heart, capillaries allow fast diffusion
• Heart valves and pacemaker

  Valves prevent backflow, pacemaker cells create electrical pulses to make heart contract
• Cardiovascular disease


  Non-communicable disease caused by factors within the body, e.g. coronary heart disease, 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