cells

• Cells


  The basic units of life that can carry out all life processes
• All living organisms, unicellular and multicellular, are made of cells
• Types of living organisms

  • Unicellular
  • Multicellular
• Unicellular organisms


  • Amoeba
  • Bread yeast
  • Protozoa
• Multicellular organisms


  • Animals
  • Humans
  • Plants
• Organelles


  Groups of complex substances inside a cell which carry out specific functions within the cell
• Protoplasm


  The living contents of a cell that is surrounded by a cell membrane
• Animal cells


  • Do not have a fixed shape because they do not have the rigid cellulose cell wall to keep them in a specific shape
• Plant cells


  • Have a rigid cellulose cell wall to keep them in a specific shape
• Protoplasm vs Cytoplasm


  Protoplasm: living contents of a cell including cell membrane, Cytoplasm: gel-like substance inside a cell.
• Cell Organelles in Animal and Plant Cells

  • Nucleus
  • Cell membrane
  • Cytoplasm
  • Vacuole
• Nucleus


  Contains hereditary materials called chromosomes which are made up of DNA. The information that DNA contains is passed from one generation to the next
• Cell membrane


  Forms a boundary between cytoplasm and the outside of the cell. A semi-permeable (or partially or selectively permeable) membrane which allows certain substances to pass through only
• Cytoplasm


  Gel-like fluid in which many organelles and dissolved chemicals are found. Made up of water mainly
• Vacuole


  Membrane bound bubbles. Animal cells have small and numerous vacuoles. Plant cells have one large central vacuole (cell sap)
• Humans have 46 chromosomes (23 from egg, 23 from sperm cell)
• Plant cells have a cell wall
• Cell wall


  • Fully permeable (allows everything to pass through)
  • Contains cellulose
  • Gives plant cells a regular shape
  • Protects plant cells from injury
• Chloroplasts


  • Surrounded by double membrane
  • Contain chlorophyll to absorb light energy for photosynthesis
• Not every cell in a multicellular organism performs the same function
• Specialized cell


  Designed to do a particular task in an organism
• Red blood cell


  • Contains hemoglobin that helps the transport of oxygen
  • No nucleus in order to contain more hemoglobin
• Muscle cell


  • Has fibres which allow muscle contraction
• Nerve cell


  • Has a long fibre to transmit electrical signals from one part of the body to another quickly
• Root hair cell


  • Has an elongated structure to increase the surface area so the absorption of water and minerals can take place quickly
• Palisade cell


  • Contains numerous chloroplasts to carry out photosynthesis more efficiently
• xylem water carrying tubes
• Phloem


  • Food carrying tube
• Nucleus

  The 'control centre' as it controls all the activities in a cell such as growth and repair
• Cell membrane


  Controls the movement of substances in and out of the cell
• Cytoplasm


  It is where most chemical reactions take place
• Vacuoles in animal cells

  Store dissolved nutrients and mineral salts
• Vacuoles in plant cells

  Filled with cell sap which stores nutrients and mineral salts, and provides turgidity to the cell by pushing the cytoplasm outward against the cell wall
• red blood cell

  has a biconcave shape to increase surface area for faster diffusion of oxygen
• Division of labour


  (in multicellular organisms) Each type of cell specialises in performing one particular function
• Benefits of division of labour in a multicellular organism

  1. Different functions can be performed at the same time

  2. Ensures smooth and efficient functioning of the organism as a whole
• Levels of cellular organisation in multicellular organisms

  • Cells
  • Tissues
  • Organs
  • Organ systems
  • Organism
• Cells


  Basic units of life
• Cells in animals


  • Muscle cell
• Tissues


  A group of similar or different cells working together to perform a similar function