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

  Increased temperature and optimal pH increase rate, but extreme conditions can denature the enzyme
• 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 temperature or pH
• 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 the trachea, bronchi, bronchioles to the alveoli where gas exchange occurs, oxygen binds to hemoglobin in red blood cells and is transported to cells, carbon dioxide is dissolved in blood plasma and exhaled
• Circulatory system


  • Double circulatory system, deoxygenated blood enters right side of heart, pumped to lungs to be oxygenated, then returns to left side of heart to be pumped to body, heart has thicker left ventricle wall to pump to whole body
• Blood vessels


  Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood towards heart, capillaries have thin walls for fast diffusion
• Coronary arteries


  Supply the heart muscle with oxygen and nutrients
• Non-communicable diseases


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


  Diseases caused by pathogens that can be transmitted between organisms
• 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