Key concepts in Biology

• eukaryotic cell = cell with a nucleus and membrane bound organelles
• prokaryotic cell = single celled microorganisms
• Animal cells – nucleus, cell membrane, mitochondria and ribosomes

  Plant cells – nucleus, cell membrane, cell wall, chloroplasts, mitochondria, vacuole and ribosomes

  Bacteria – chromosomal DNA, plasmid DNA, cell membrane, ribosomes and flagella
• Plant cells:

  • Cell wall- rigid made of cellulose which supports and strengthens cell
  • Chloroplasts- where photosynthesis occurs for food and contains chlorophyll
  • Large vacuole- contains cell sap for internal pressure for support
• Animal cells:


  • Nucleus- contain genetic material that controls activites of cell(chromosomes)
  • Ribosomes- translation of genetic material in synthesis of proteins.
  • Mitochondria- reactions of respiration take place here which transfers energy for cell to work
  • Cell membrane- holds cell together controls what goes in and out.
  • Cytoplasm- gel-like substance where chemical reactions occur (contains enzymes)
• Bacteria cell:

  • Chromosomal DNA- (long circular chromosome) controls activities and replication floats free
  • Cell membrane Plasmid DNA- small loops of extra DNA which contain genes like drug resistance
  • Flagellum- long hair like structure rotates to move away from toxins towards nutrients & oxygen
  • Ribosomes - protein synthesis
• Sperm Cell Adaptations:

  • mitochondria (provides energy to swim)
  • tail (to swim to egg)
  • acrosome (stores enzymes to digest through egg membrane)
  • haploid nucleus
• Egg Cell Adaptations

  • changes in the cell membrane after fertilisation (to stop anymore sperm getting in)
  • nutrients in the cytoplasm (feed embryo)
  • haploid nucleus
• Ciliated Epithelial Cell Adaptations

  • line surface of organs
  • beat to move substances along the surface of tissue
  • lining airways to move mucus up throat to be swallowed and not get to lungs.
• Light microscopes : low resolution and low magnifications
• Electron microscopes : high resolution and high magnification
• UNITS: (going up /1000) (going down x1000)

  • millimetre (10^3)
  • micrometre(10^6)
  • nanometre (10^9)
  • picometre (10^12)
• ENZYME + SUBSTRATE -> ENZYME-SUBSTRATE COMPLEX -> ENZYME + PRODUCTS
• Enzymes = biological catalyst that can break down molecules (digestion) or join substrate molecules (synthesis) if the substrate does not fit the active site the reaction will not be catalysed
• Denature = when a enzyme becomes denatured there is a change to the enzymes active site therefore it cannot catalyse the reaction of its specific substrate.
• TEMPERATURE - EFFECT ON ENZYMES

  • higher the temp=quicker the rate
  • if it gets to hot the enzyme will denature as bonds break= decrease in rate
• pH - EFFECT ON ENZYMES

  • optimum pH (7) pepsin is pH (2) breaks down proteins in stomach.
  • if its too high or too low it will interfere with the enzymes bonds causing it to denature
• SUBSTRATE CONCENTRATION - EFFECT ON ENZYMES

  • after a certain point there are too much molecules as all active sites are full the rate remains constant.
  • high the conc=faster the rate (more likely to meet substrate)
• 1. Protein -> Amylase
  2. Starch -> Glucose
  3. Lipid -> Fatty Acids + Glycerol
• ENERGY IN FOOD (J)= mass of water(g) X temp change of water(dc) X 4.2ENERGY PER GRAM OF FOOD (J/g) = energy in food (J) / mass of food (g)
• DIFFUSION = the net movement of particles from a area of higher concentration to an area of lower concentration
• OSMOSIS = the net movement of water molecules across a partially permeable membrane from a region of higher concentration to a region of lower water concentration.
• ACTIVE TRANSPORT = the movement of particles across a membrane against a concentration gradient using energy transferred during respiration.
• Biuret test - test for protein


  Purple (Positive)

  Pale blue (Negative)
• Iodine Solution - Test for starch


  Blue-black (positive)

  Yellow-Brown (negative)
• Benedict's solution - Test for reducing sugars 


  Little - green

  More - yellow/orange

  Lots - brick red

  Blue (negative)
• Ethanol emulsion test - test for fats and oils 


  Cloudy emulsion (positive)

  Clear (negative)