Cell structure and processes

Cell structure and processes

1. Transport across cells

   • Passive processes (do not require energy)
     • Diffusion
       • Net movement of molecules of a substance from a region of high concentration to a region of low concentration until equilibrium is achieved (only for liquids/gas)
         • Concentration gradient --> difference in concentration
         • Moving down/along the concentration gradient --> high con. to low con.
         • Moving against the concentration gradient is not in the lower sec. syllabus
         • Example: A hidden durian is brought into the classroom (the durian smell would diffuse until the whole classroom smells evenly of durian)
     • Osmosis
       • Net movement of water molecules in a liquid body from a region of higher water potential through a partially permeable membrane to a region of lower water potential until equilibrium is achieved
         • Water potential --> % of water a substance contains
           • Hypotonic to ___ --> solution has a higher water potential
           • Isotonic to ___ --> solution has an equal water potential
           • Hypertonic to ___ --> solution has a lower water potential
           • Symbol for <water potential> --> Ψ
   • Active processes (require energy)
     • Active transport

2. Structure of cells

   • Eukaryotic (membrane bound organelles)
     • Animal cell
     • Plant cell
   • Prokaryotic (non-membrane bound organelles)
     • Root hair cell
     • Red blood cell (erythrocyte)

3. Things to know

   • Nucleus
     • Controls activity of the cell
     • Stores genetic information (for reproduction)
   • Chloroplast
     • Site for photosynthesis
   • Mitochondria
     • Site of respiration/energy (ATP) production
   • Vacuoles
     • Storage
   • Plasma membrane
     • Compartmentalise biochemical reactions
     • Regulates substances travelling in & out
     • Contains the cytoplasm of the cell
   • Cellulose cell wall
     • Provide structural support
       • Fully permeable
   • Note: Cytoplasm --> cytosol + organelles

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