Biology p1

• 
  

  • Cytoplasm
  • Site of chemical reactions in the cell
  • Enzymes to catalyse the reactions
• Nucleus


  • Contains genetic material
  • Controls the activities of the cell
  • Codes for proteins
• Cell membrane


  Controls the movement of substances in and out of the cell
• ribosome

  • mRNA is Translated to amino acids
  • Site or protein synthesis
• Cellulose


  • Gel-like substance containing enzymes to catalyse reactions
  • Supports and strengthens the cell
• Plasmid


  Small rings of DNA
• Mitochondrion


  Where energy is released for the cell to function
• Eukaryotes


  Complex organisms
• Plant cell


  • Contains all the parts of animal cells plus extras
  • Contains cell sap
  • permanent Vacuole keeps cell turgid
  • Contains sugars and salts in solution
  • Mode of cellulose supports and strengthens the cell
  • Chloroplast is the site of photosynthesis
  • Contains chlorophyll, absorbs light energy
• Undifferentiated cells


  Called STEM cells
• Animal cell differentiation


  • Early stages of development
  • Only for repair and replacement
• Plant cell differentiation


  • All stages of life cycle
  • Stem cells are grouped together in meristems
• Microscopy


  • Magnification = Size of image / Real size of object
  • Light microscope: Magnification up to 1500x, Resolution 200nm
  • Electron microscope: Magnification up to 2,000,000x
• Prefixes


  • centi (cm) = 10^-2 m
  • micro (μm) = 10^-6 m
  • nano (nm) = 10^-9 m
• Endothermic reaction


  Energy is absorbed, breaking bonds
• Exothermic reaction


  Energy is released, making bonds
• Cell


  Smallest structural and functional unit of an organism
• Nucleus


  Structure that contains genetic material and controls cell activities
• Chromosome


  Thread-like structure of coiled DNA found in the nucleus of eukaryotic cells
• DNA


  Polymer made up of two strands forming a double helix
• Gene


  Section of DNA that codes for a specific protein or characteristic
• Cell division


  1. Growth stage

  2. DNA synthesis stage

  3. Mitosis stage
• Adaptations for diffusion


  • Large surface area
  • Thin membranes for short diffusion path
  • Good blood supply to maintain concentration gradient
• Diffusion


  Movement of particles from higher to lower concentration, no energy required
• Osmosis


  Movement of water from dilute to concentrated solution, no energy required
• Active transport


  Movement of particles from dilute to concentrated solution, energy required
• The greater the difference in concentrations, the faster the rate of diffusion
• Mitosis


  • Increases the number of sub-cellular structures
  • Replicates DNA to form two copies of each chromosome
  • One set of chromosomes is pulled to each end of the cell and the nucleus divides
  • Cytoplasm and cell membranes divide to form two identical cells
• Stem cells


  Undifferentiated cells that can divide to form more cells of the same type, and can differentiate to form many other cell types
• Stem cells


  • Human embryonic stem cells
  • Adult bone marrow stem cells
  • Meristems (plants)
• Therapeutic cloning uses stem cells with the same genes so the body does not reject the tissue, but there is a risk of infection
• Tissue from adult stem cells is matched to avoid rejection, but only a few types of cells can be formed
• Cloning with plant meristems can be used to produce clones quickly and economically, e.g. rare species, crop plants with pest/disease resistance
• Treatment with stem cells may be able to help conditions such as diabetes and paralysis, but some people object to the use of stem cells on ethical or religious grounds
• Enzymes


  • Catalyse (increase the rate of) specific reactions in living organisms
  • Activity is affected by changes in temperature and pH
• Enzyme action


  The lock and key theory is a simplified model to explain enzyme action
• Digestive enzymes


  Speed up the conversion of large insoluble molecules (food) into small soluble molecules that can be absorbed into the bloodstream
• Large changes in temperature or pH can stop the enzyme from working (denature)
• Digestive enzymes


  • Carbohydrases (e.g. amylase)
  • Proteases
  • Lipases
• Bile


  • Not an enzyme, emulsifies lipids to increase surface area to increase the rate of lipid breakdown by lipase
  • Changes pH to neutral for lipase to work