Biology paper 1

• A light microscope allows you to se the outlines of cells whereas an electron microscope allows you to see finer details and organelles
• resolution is the smallest distance between two objects that can be distinguished as separate objects
• magnification = image size/ actual size
• eukaryotic cells are bigger, have a nucleus and have mitochondria
• prokaryotic cells are smaller, have uncontained genetic material and no mitochondria
• bacteria divide every 20 minutes via binary fission
• Making cultures practical

  1. lift lid of petri dish towards flame to sterilise
  2. use a sterilised inoculating loop to spread culture on agar
  3. put discs of antibiotics on top with one control
  4. secure lid with a bit of tape to allow aerobic respiration and incubate at 25 degress
  5. measure zone of inhibition using pi * r^2
• cells have 46 chromosomes (diploid)
• new cells are made by mitosis for growth and repair
• Stages of the cell cycle

  . cell grows, nucleus dissolves and chromosomes double and organelles double

  . two sets of chromosomes are pulled to each side of the cell

  . nucleus divides and cytoplasm and cell membrane to form two daughter cells
• stem cells can specialise into any cell
• stem cells are found in embryos and some parts in adults. it is also found in the meristem in plants
• Stem cells can be used to treat diseases with faulty cells such as paralysis
• there are ethical reasons against stem cell treatment as an embryo is a potential life
• Diffusion is the movement of particles from an area of high concentration to an area of low concentration. it is passive
• osmosis is the movement of water molecules from a concentrated to a more dilute solution through a partially permeable membrane. it is passive
• active transport is the movement of molecules from a low concentration to a high concentration. it requires energy
• Osmosis practical

  1. weigh and place identical potato cylinders in sugar solutions of varying concentrations with one control
  2. after a day, remove excess water and reweigh
  3. plot % change against sugar conc. on graph and plot a line of best fit. where the line crosses is where the potato sugar conc. = conc. of solution
• Digestion

  1. Teeth break down food mechanically and amalayse breaks down carbohydrates
  2. food goes through oesophagus to stomach where it gets churned and Pepsin beaks down protein
  3. it then goes to small intestine whee nutrients are absorbed into bloodstream via villi. the pancreas also secretes enzymes to small intestine and liver produces bile which emulsifies fat and neutralises stomach acid
  4. water absorbed from food in large intestine
  5. food stored in rectum until excretion
• Enzymes are biological catalysts made of protein and they are specific
• carbohydrates break down into glucose by carbohydrase
• proteins break down into amino acids by protease
• lipids broken into 3 fatty acids and 1 glycerol
• The rate of reaction of enzymes is affected by temperature and pH
• Enzyme practical

  1. mix amylase and starch and pH buffer solution
  2. add drops of the solution into spotting tiles with iodine every 10 seconds
  3. record the time taken for no starch to be detected (no colour change)
  4. repeat with different pH buffer solutions
• Food tests


  iodine: orange - black

  Benedicts : blue - green if little sugar, yellow if moderate sugar and brick red if lots of sugar

  biuret : blue - purple

  ethanol: brick red layer is formed
• alveoli adaptations are one cell thick wall for short diffusion pathway, large SA for higher rate of gas exchange and large supply to maintain concentration gradient
• oxygen diffuses into blood and binds to haemoglobin in red blood cells
• path of blood in the body

  vena cava - right atrium - right ventricle - pulmonary artery - lungs - pulmonary vein - left atrium - left ventricle - aorta - body
• arteries have thick walls and a small lumen to withstand high pressure and carry blood away from the heart
• veins have thin walls, valves and a large lumen to allow blood to flow quickly. they carry blood to the heart
• coronary heart disease is when the artery supplying blood becomes blocked due to cholesterol build up
• treatments of coronary heart disease

  . Statins used to lower cholesterol

  . Stents used to open the vessel

  . Heart bypass used by getting another blood vessel bypassing the blockage
• white blood cells fight infection
• red blood cells transport oxygen
• Platelets help clot blood
• plasma transports everything but O2
• Non communicable diseases cannot be spread and includes diseases such as diabetes and cancer
• cancer is a disease caused by uncontrolled cell division and it forms a tumour
• benign cancer doesn’t spread whereas malignant cancer does spread via bloodstream