Classification

• Cells are the building blocks of living things
• Characteristics of living things

  • Possess the 7 characteristics mentioned earlier
• List the function of cell organelles

  • Cell membrane
  • Cytoplasm
  • Nucleus
  • Nucleolus
  • Chromosomes
  • Mitochondrion
  • Ribosomes
  • Cell wall
  • Chloroplasts
  • Vacuoles
• • Chromosome not enclosed in a nucleus (prokaryotic)
  • Chromosome enclosed in a nucleus (eukaryotic)
  • Most are unicellular
• Cell membrane


  Selectively or partially permeable barrier which controls exchange between the cell and its environment
• Cytoplasm


  Jelly-like substance that holds the organelles, 70% water, medium for chemical reactions
• Nucleus


  Controls the functioning/activities of the cell, surrounded by nuclear membrane, contains chromosomes with DNA
• Nucleolus


  Located in the nucleus, produces ribosomal RNA (rRNA) for ribosomes
• Chromosomes


  Carry genetic information in the form of DNA, responsible for traits and characteristics
• Mitochondrion


  The "power-house" of the cell, produces energy for the cell by breaking down glucose (respiration)
• Ribosomes


  Found on the endoplasmic reticulum, manufacture, package and transport various substances, site of protein synthesis
• Cell wall


  Rigid structure that surrounds the cell membrane and gives the plant its sturdy structure, contains cellulose and other tough materials
• Chloroplasts


  Lens-shaped structures found only in plant cells, contain chlorophyll which gives plants their green colour, site of photosynthesis
• Vacuoles


  Fluid-filled sacs surrounded by a vacuolar membrane, store sugar, minerals, waste, food substances
• Types of microbes


  • Viruses
  • Bacteria
  • Fungi
  • Protoctists (algae and protozoa)
• Viruses


  • Not made of cells, only virus particles or virions, can only live inside other cells
• Bacteria

  • Do not have membrane-bound organelles, have a nucleoid region containing genetic material, some have capsules and cell walls, have flagella for movement
• Fungi


  • Can be unicellular or multicellular, heterotrophic, obtain food from the environment, digest food outside their bodies using enzymes
• Algae


  • Make their own food by photosynthesis, live as single cells or in groups/colonies
• Protozoa


  • Unicellular and heterotrophic, cause diseases like malaria and sleeping sickness
• Cell specialization


  When a cell contains certain organelles or structures that allow it to perform a specific set of functions
• Cell differentiation


  The process by which unspecialized cells become specialized cell types
• Examples of specialized cells

  • Red blood cell
  • Nerve cell
  • Epithelial cell
  • Sperm cell
  • Egg cell
  • Bone cell
  • Skeletal muscle cell
  • Smooth muscle cell
  • Cardiac muscle cell
• Red blood cell


  • Function: Transport oxygen, Adaptation: No nucleus, flexible to squeeze through capillaries
• Nerve cell


  • Function: Send messages throughout the body, Adaptation: Shape allows dendrites to receive messages, axon to transmit messages
• Epithelial cell


  • Function: Line, cover and protect organs and systems, Adaptation: Flat cells that can stack to create lining
• Sperm cell


  • Function: Fertilize egg, Adaptation: Tail for swimming, head with enzymes and nucleus
• Egg cell


  • Function: Be fertilized, Adaptation: Large with yolk for food storage, produced in ovaries
• Bone cell


  • Function: Support the body, Adaptation: Thick and compact for strength
• Skeletal muscle cell


  • Function: Move bones, Adaptation: Long, cylindrical, striated fibres that can shorten
• Smooth muscle cell


  • Function: Contract to cause movement in internal organs, Adaptation: Can shorten to cause contraction
• Cardiac muscle cell


  • Function: Contract to pump blood, Adaptation: Striated appearance, form branching threads
• Plant cell structures


  • Xylem vessels
  • Phloem vessels
• Xylem vessels


  Transport water, made of hollow cells joined end-to-end, have no cytoplasm or nucleus, walls made of cellulose and lignin
• Phloem vessels


  Transport soluble food like glucose, made of cells joined end-to-end with sieve plates, contain cytoplasm but no nucleus, have companion cells
• Cells are arranged to form multi-cellular organisms
• Diffusion in the cell

  Molecules move from high to low concentration without energy input
• Osmosis in the cell

  Movement of water across a semi-permeable membrane from low to high solute concentration
• Osmosis experiments


  • Water moves in/out, solute moves in/out, liquid level rises/falls, no net movement
• Active transport


  Movement of substances across a membrane against a concentration gradient, using energy from the cell