BIO10004 WK 2

• Cells are produced by the division of pre-existing cells
• Cells maintain homeostasis at the cellular level
• Cells are the building blocks of all plants, fungi, and animals
• Cell

  • Is surrounded by extracellular fluid
  • Has an outer boundary called the cell membrane
  • Contains internal medium or cytoplasm
  • Contains mitochondria (ATP power station)
  • Contains a nucleus (locus of genetic information)
• Cytoplasm


  • Contains the fluid (cytosol) with ions
  • Contains the organelles the cytosol surrounds
• Osmosis


  1. Diffusion of water across a semipermeable membrane in response to solute differences

  2. Osmotic pressure = force of water movement into a solution

  3. Water molecules undergo bulk flow

  4. Hydrostatic pressure opposes and balances out osmotic pressure
• Active transport

  1. Consumes energy (ATP)

  2. Independent of concentration gradients

  3. Types include Ion pumps, Secondary active transport
• At higher levels, the combined, coordinated action of many cells is observed
• Cells are the smallest units that perform all vital physiological functions
• Levels of organisation

  • Organism
  • Organ system
  • Tissue
  • Cellular
  • Chemical/molecular
• Cytology is the study of cells
• The cell membrane functions include physical isolation, regulation of exchange of ions & molecules with the environment, and structural support
• Cell membrane

  • It is a phospholipid bilayer with proteins, lipids, and carbohydrates
• Diffusion


  1. Movement of a substance from an area of high concentration to low

  2. Continues until concentration gradient is eliminated
• Permeability


  Cell membranes are selectively permeable
• Effects of osmotic solutions on cells

  • Isotonic = no net gain or loss of water
  • Hypotonic = net gain of water into cell
  • Haemolysis (or Hemolysis)
  • Hypertonic = net water flow out of cell
  • Crenation
• The Sodium-Potassium Exchange Pump results from ionic concentrations and difference in electrical potential from inside to outside the cell
• Facilitated diffusion


  Compounds to be transported bind to a receptor site on a carrier protein
• An undisturbed cell has a resting potential of around 70 mV (outside more positive)
• Nucleus function

  • control of the genetical information of the cell and thus the heredity characteristics of an organism,
  • control of the protein and enzyme synthesis.
  • control of cell division and cell growth.
  • storage of DNA, RNA and ribosome.
  • regulation of the transcription of the mRNA to protein.
  • production of ribosomes.
• Importance of cell division

  1. Renewing of damaged cells.
  2. Production of new cells from older ones.
  3. Maintains the total number of chromosomes.
  4. Provides more cells for growth and development.
  5. Repairs and controls damages caused to the cells.