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
• 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, nucleus breaks down, chromosomes are pulled to opposite sides, new nuclei form, resulting in 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
• Factors affecting diffusion and osmosis

  Increased concentration difference, temperature, or surface area can increase the rate
• Practical on osmosis


  Cut equal-sized vegetable cylinders, weigh, place in varying sugar solutions, reweigh after a day, calculate percentage change in mass, plot against concentration to find the point of no change (same internal concentration)
• Active transport


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


  Groups of similar cells connected 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 break down larger molecules into smaller ones, specific to certain substrates due to the lock-and-key principle
• Factors affecting enzyme activity

  Increased temperature increases rate until denaturation, optimum pH range
• Practical on enzyme activity

  Mix amylase with starch at different temperatures or pH, time how long it takes to break down all the starch, 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 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, 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, arteries carry oxygenated blood, veins carry deoxygenated blood, capillaries allow fast diffusion
• 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