BIO PAPER 1

• Light microscope


  Cheap to make, can only see outlines of cells
• Electron microscopes 


  Can see finer details (eg organelles) due to greater resolving power/higher resolution
• Magnification 


  image size ÷ object size
• Eukaryotic vs Prokaryotic


  Eukaryotic have a nucleus to store DNA (animal + plant), prokaryotic DNA found in plasmid (loop of DNA, eg bacteria)
• Binary Fission Practical


  Making cultures with aseptic technique: sterilise petri dish near flame, drop of culture on agar, drops of antibiotic, tape (small amount to allow aerobic respiration), incubate at 25°C, measure size of cultures.
• Chromosomes


  human cells have 23 pairs of chromosomes (diploid), except gametes which have only 23 (haploid).

  New diploid cells made by mitosis
• Mitosis process

  • Nucleus dissolves, genetic material duplicated
  • 2 sets of chromosomes move to different sides
  • Mitochondria, ribosomes etc. duplicated
  • cell divides, producing 2 genetically identical diploid cells
• Specialisation


  Stem cells can specialise to perform specific functions. They are found in animal embryos and plant meristems.

  some stem cells are made in bone marrow, but can only specialise into blood cells.
• Diffusion 


  Movement of particles from area of high to area of low concentration, requires no energy (passive)
• Osmosis


  diffusion of water across semi permeable membrane to balance concentrations inside and outside a cell.
• Osmosis practical


  Weigh and place identical cylinders from oame vegetable (potato) in sugar solutions if varying concentrations.

  After set time, remove excess water and reweugh to calculate percentage change in mass (final mass - initial mass ÷ initial mass × 100). Plot this change against concentration: the conc at 0% change in mass is the same as inside potato.
• Digestive system: teeth

  Break down food mechanically, saliva contains amylase
• Digestive system: Stomach

  contains hydrochloric acid and enzymes which chemically break down food
• Digestive system: Liver

  produces bile which is stored in gall bladder before going to small intestine. Bile emulsifies lipids to form droplets, increasing their surface area
• Digestive system: pancreas

  secretes amylase which breaks down starch into glucose in small intestine
• Enzymes


  Enzymes are special proteins that act as a biological catalyst, often breaking down molecules into shorter ones (polymers into monomers).
• Enzymes break down

  Carbohydrase breaks down carbohydrates into simple sugars (eg. amylase breaks down starch into glucose).

  Proteases break down proteins into amino acids.

  Lipase break down lipids into glycerol and fatty acids.
• Enzyme practical

  Mix amylase with starch and start timer. Remove a few drops from mixture every 10 seconds and add to iodine. Record time taken for no starch to be detected (will remain orange). Repeat at different temperatures or with different pH buffer solutions added.
• Food tests

  Starch: turns iodine from orange to black

  Sugars: turn benedict's solutiin from blue to orange

  Protein: turns buiret's reagent from blue to purple

  Lipids: turn cold ethanol cloudy
• Lactic acid is broken back down into glucose by the liver using oxygen
• anaerobic respiration in plants(fermentation)


  glucose = ethanol + carbon dioxide
• Pondweed practical


  pondweed stem, in inverted cylinder filled with water. (add sodium hydrogen carbonate to provide CO2). Measure distance from light source. Let acclimatise, measure volume of oxygen made in 1 min. Repeat with different light distances.
• The Heart

  Blood enters from right side of heart (Vena Cava) into right atrium, then right ventricle. Then goes through pulmonary artery to the lungs. Comes back to heart from pulmonary vein into left atrium, then left ventricle, then out to the body throught the aorta (all from left to right in drawing).
• Statins

  drugs which lower cholesterol
• Plant structure - leaf

  Photosynthesis, gas exchange, water evaporates out
• Plant structure - Xylem

  tubes which carry water and dissolved mineral ions upwards (transpiration)
• Plant structure - roots

  water enters through osmosis, mineral ions enter through active transport.
• Plant structure - meristem

  Stem cell production
• Plant structure - Phloem


  tubes of cells that carry sugar (eg. sucrose) and other nutrients to where needed (translocation)
• Nitrates are needed for protein synthesis. Deficiency means it has stunted growth.
• Chlorosis is a magnesium deficiency in plants. Yellow leaves and stunted growth as there is less chlorophyll.
• Leaf structure - Waxy cuticle

  waterproof to stop water loss from top of leaf
• Leaf structure - Upper Epidermis


  second, transparent to let light through.
• Leaf structure - Palisade Mesophyll


  Third, most Photosynthesis takes place here.
• Leaf structure - spongy mesophyll


  Fourth, gaps to facilitate gas exchange (large surface area).
• Leaf Structure - Vein/Vascular bundle


  Xylem and Phloem
• Leaf structure - Lower Epidermis + Stomata


  Bottom of leaf / holes in lower Epidermis to allow gases through including water.
• Leaf structure - guard cells

  change size to control rate of gases entering and exiting through stomata
• Nervous system - normal reaction 


  stimulus - receptor - sensory neurone - relay neurone - motor neurone - effector
• Nervous system - reflex arc


  signal bypasses brain, much quicker (eg burn on stove).