1.1

• Features common to plant and animal cells

  • Cytoplasm
  • Cell membrane
  • Nucleus
  • Mitochondria
• Cytoplasm


  Where chemical reactions that make up life take place
• Cell membrane


  Controls what enters and exits the cell
• Nucleus


  Contains DNA
• Mitochondria


  Carries out aerobic respiration, supplies cells with energy
• Plant cells


  • Have cell wall made of cellulose
  • Have central vacuole filled with sap
• Plant cells


  • Have chloroplasts that absorb light for photosynthesis
• Sperm cells


  • Have little cytoplasm and a tail to swim fast toward the egg
• Red blood cells


  • Have lost their nuclei and are packed with haemoglobin to carry oxygen around the body
• Xylem cells


  • Form tubes which carry water to the plant, cell walls are thick, cytoplasm dies off to leave a hollow tube
• Levels of organization

  • Cell
  • Tissue
  • Organ
  • Organ system
  • Organism
• Tissue


  A group of similar cells with similar functions
• Organ


  A collection of tissues that do specific functions
• Organ system

  A collection of several organs that work together
• Organism


  The whole animal or plant
• Diffusion is the passing movement of substances down a concentration gradient
• Cell membrane forms a selectively permeable barrier that allows diffusion of water
• Active transport is an active process by which substances can enter cells against a concentration gradient
• Enzymes


  Proteins made by living cells which catalyse the rate of chemical reactions
• High temperatures and extremes can denature an enzyme
• Enzyme catalysis


  1. Enzyme and substrate collide

  2. Enzyme-substrate complex forms

  3. Catalysis occurs

  4. Products are released
• Substrate


  The substance that an enzyme acts upon
• Prokaryotic cells


  a cell which does not have a nucleus - the DNA strands are free in the cytoplasm
• Eukaryotic cells


  a cell which has a nucleus, eukaryotic cells also have other structures in the cytoplasm which have membranes around them
• Stem cells


  embryonic stem cells - undifferentiated, have potential to turn into any cell

  adult stem cells - found in bone marrow, can only form a certain cell ( eg blood cells )
• Uses of stem cells

  • replaces faulty blood cells
  • making insulin producing cells
  • making nerve cells
• Bacterial cells

  • Prokaryotic cells
  • contain a plasmid
  • cell splits into two
• For embryonic stem cell research

  • curing patients with stem cells are more important than the rights of embryos
  • they are only using unwanted embryos from fertility clinics, which would normally be destroyed
• Against embryonic stem cell research

  • embryos are human life
  • scientists should find other sources of stem cells ( eg adult stem cells )
• Stem cells in plants

  • found in meristem
  • produce clones of plants
  • can grow crops with specific features ( eg disease resistant )
• Examples of tissues, organs and organ systems

  • tissue - bone muscle, blood, xylem, epidermis
  • organs - kidney, brain, heart, leaf, flower
  • organ systems - digestive system, nervous system, shoot system