Biology unit 1

• Unicellular organism


  One single cell
• Multicellular organism


  Made up of many cells
• Cell ultrastructure


  Internal structure revealed under magnification with a microscope
• Ultrastructure of an animal cell

  • Cell membrane
  • Nucleus
  • Cytoplasm
  • Mitochondria
  • Ribosomes
• Ultrastructure of a plant cell

  • Cell wall
  • Cell membrane
  • Nucleus
  • Cytoplasm
  • Sap vacuole
  • Mitochondria
  • Ribosomes
  • Chloroplasts
• Ultrastructure of a fungal cell

  • Cell wall
  • Cell membrane
  • Nucleus
  • Cytoplasm
  • Vacuole
  • Mitochondria
  • Ribosomes
• Ultrastructure of a bacterial cell

  • Cell wall
  • Cell membrane
  • Cytoplasm
  • Plasmids
  • Ribosomes
• Nucleus


  Contains genetic material (DNA) and controls cell activities
• Cell membrane


  Controls the entry and exit of substances into and out of the cell
• Cell organelles


  Compartments found in the cytoplasm and are the site of chemical reactions
• Bacterial cells do not contain organelles
• Cell wall


  For support and shape and prevents plant cells from bursting. Plant cell walls are made of cellulose.
• Vacuole


  Stores a watery solution of salts and sugars and helps to support cells
• Chloroplasts


  Contain chlorophyll and are the sites of photosynthesis
• Mitochondria


  Are the sites of aerobic respiration in cells
• Ribosomes


  Are the sites of protein synthesis in cells
• Plasmids


  Hold some of the genetic material (DNA) of the bacterial cell
• Plant, fungal and bacterial cell walls have different structures and are composed of different chemicals
• Bacterial cells are usually a lot smaller than other cells
• Cell membrane


  Composed of (phospho)lipid and protein
• Cell membrane


  Selectively permeable. Membrane proteins have channels that allow substances to enter and leave the cell
• Concentration gradient


  A difference in concentration of a substance
• Passive transport


  Movement of molecules down the concentration gradient from a high concentration to a lower concentration, without requiring additional energy
• Passive transport processes


  • Diffusion
  • Osmosis
• Diffusion


  Movement of substances from a high concentration to a lower concentration down a concentration gradient
• Substances that enter most cells by diffusion

  • Oxygen
  • Glucose
  • Amino acids
• Substances that leave most cells by diffusion

  • Carbon dioxide
  • Urea
• Osmosis


  Movement of water from a region of high water concentration to a region of lower water concentration through a selectively permeable membrane
• Plasmolysed


  Term used to describe a cell in which the vacuole has shrunk due to water loss, causing the cell membrane to move away from the cell wall
• Turgid


  Term used to describe a cell or tissue in which the vacuole has swollen due to water gain and presses the cytoplasm and cell membrane against the cell wall
• Active transport


  Movement of molecules from a region of low concentration to a region of higher concentration, against the concentration gradient, requiring additional energy (ATP)
• Substances actively transported


  • Sodium
  • Potassium
  • Iodine
• Diffusion and osmosis are passive processes and do not require extra energy
• Active transport requires energy
• Osmosis is a type of diffusion but always involves water passing through a membrane
• To take up substances against a concentration gradient, cells use oxygen for respiration to release energy for active transport
• Chromosomes


  Made up of regions called genes
• DNA


  A complex substance that forms the genes of all living organisms. Genetic information; information for making proteins. A gene is a section of DNA which codes for one protein.
• DNA molecule


  A double-stranded helix
• Types of DNA base

  • Adenine (A)
  • Thymine (T)
  • Guanine (G)
  • Cytosine (C)