Paper 1 biology

• 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
• Eukaryotic cell nuclei


  • Contain DNA stored in several chromosomes, humans have 23 pairs (diploid cells)
  • Gametes have half the number of chromosomes (haploid cells)
• Cell division


  Mitosis: Genetic material is duplicated, nucleus breaks down, one set of chromosomes pulled to opposite sides, new nuclei form, resulting in two identical cells
• Cell specialization


  • Cells specialize depending on their function, 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, a passive process
• Osmosis


  The diffusion of water across a semi-permeable membrane
• Factors that increase the rate of diffusion and osmosis: Increased concentration difference, increased temperature, increased surface area</b>
• Practical on osmosis


  Cut equal size cylinders from a vegetable, 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
• Enzymes


  Biological catalysts that speed up chemical reactions, specific to certain substrates due to the lock and key principle
• Factors affecting enzyme activity


  • Rate increases with temperature up to the optimum, then decreases as the enzyme denatures
  • Rate also affected by pH, with an optimum pH
• 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 turns black with starch, Benedict's solution turns orange with sugars, Biuret's reagent turns purple with proteins, ethanol goes cloudy with lipids
• Breathing vs respiration


  Breathing provides the 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 and water are expelled during exhalation
• Circulatory system


  • Double circulatory system, deoxygenated blood enters right side of heart, pumped to lungs, oxygenated blood returns to left side and is pumped to body
  • Heart has thicker walls on left side to pump blood to whole body
  • Blood vessels: Arteries carry oxygenated blood away from heart, veins carry deoxygenated blood towards heart
• Coronary arteries


  Supply the heart muscle with oxygen and nutrients
• 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
• Cardiovascular (CV) disease


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


  • Cardiovascular disease
  • Autoimmune conditions
  • Cancer
• Communicable disease


  Caused by a pathogen that enters the body, resulting in viral, bacterial or fungal infection