biology paper 1

• Light microscope


  Can see cells and maybe the nucleus, but not subcellular structures
• Electron microscope

  Can see finer details and subcellular structures, has better resolving power and higher resolution
• Calculating cell size


  1. Measure image size

  2. Divide by magnification
• Eukaryotic cells


  Have a nucleus where DNA is found (e.g. plant and animal cells)
• Prokaryotic cells


  Don't have a nucleus, DNA is in a ring called a plasmid
• Subcellular structures


  • Cell membrane
  • Cell wall (in plant cells and most bacteria)
  • Cytoplasm
  • Mitochondria
  • Ribosomes
  • Chloroplasts (in plant cells)
• Bacterial binary fission


  1. Number doubles every 10 minutes

  2. Practical: Grow culture on agar plate using aseptic technique

  3. Calculate size of culture from initial drop or area not grown
• Diploid cells


  Have 23 pairs of chromosomes
• Haploid cells


  Have 23 chromosomes (not in pairs)
• Mitosis


  1. Genetic material duplicated

  2. Nucleus breaks down

  3. Chromosomes pulled to opposite sides

  4. New nuclei form
• Specialised cells


  • Nerve
  • Muscle
  • Root hair
  • Xylem
  • Phloem
• Stem cells


  Unspecialised cells that can differentiate into different cell types
• Diffusion


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


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


  • Concentration difference
  • Temperature
  • Surface area
• Practical: Osmosis in potato cylinders

  1. Weigh potato cylinders in different sugar solutions

  2. Calculate percentage change in mass

  3. Plot against concentration to find no change point
• Active transport


  Using energy to move substances against a concentration gradient
• Tissues


  • Heart
  • Digestive
• Digestive system processes


  • Acid in stomach
  • Bile and enzymes in small intestine
  • Emulsification of fats
• Enzymes


  • Biological catalysts that are specific to certain substrates
  • Rate increases with temperature until denaturation
  • Rate also affected by pH
• Practical: Investigating enzyme activity

  1. Mix amylase and starch at different temperatures or pH

  2. Time taken for starch to be broken down

  3. Plot against temperature/pH to find optimum
• Food tests


  • Iodine for starch
  • Benedict's solution for sugars
  • Biuret's reagent for proteins
  • Ethanol for lipids
• Respiratory system structures


  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli
• Respiration


  Provides oxygen for cells to carry out cellular respiration
• Circulatory system components


  • Right atrium
  • Right ventricle
  • Pulmonary artery
  • Pulmonary vein
  • Left atrium
  • Left ventricle
  • Aorta
• Heart pacemaker


  Group of cells that create electrical pulses to make the heart contract
• Arteries


  Carry oxygenated blood away from the heart, have thicker walls
• Veins


  Carry deoxygenated blood towards the heart, have thinner walls and valves
• Capillaries


  Tiny blood vessels with one-cell thick walls for fast diffusion
• Coronary artery


  Supplies the heart muscle with oxygen and nutrients
• Stents


  Tubes inserted into blood vessels to keep them open
• Statins


  Drugs that reduce cholesterol and fatty deposits
• Heart valve replacement


  Artificial valves can replace faulty ones
• Non-communicable diseases


  Caused by internal factors, e.g. cardiovascular disease, allergies, cancer
• Communicable diseases


  Caused by external pathogens, e.g. infectious diseases
• 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
• Heart valve replacement


  Artificial heart valves can replace faulty ones to prevent backflow