Natural Science (GRADE 9)

• Cell


  Fundamental structural unit of organisms
• Cells


  • Provide a structure for the body
  • Assist in the growth of organisms by dividing themselves
  • Take nutrients from food and convert them into energy
• Cells are too small to see with a naked eye and can only be seen through a microscope (microscopic)
• Parts of the cell

  • Cell membrane
  • Cell wall
  • Cytoplasm
  • Nucleus
  • Mitochondria
  • Vacuole
  • Chloroplast
• Cell membrane


  A thin semipermeable layer of protein and fat that surrounds the cell
• Cell wall


  An organelle made of cellulose and only found in plant cells
• Cell wall


  • Protects the cell organelles
  • Gives the cell strength and structure or shape
• Cytoplasm


  The gel-like appearance mainly composed of water with enzymes, salts, organelles and organic molecules
• Cytoplasm


  • Houses the cell's organelles
  • Gives shape to the cell
  • Supports biochemical reactions like respiration

  
• Nucleus


  An organelle that is enclosed by a membrane and found in most cells except bacteria and blue green algae (found in eukaryotic cells)
• Nucleus


  • Contains the DNA or carries the genes of the organism
  • Controls and regulates the activities in the cell, e.g. growth and metabolism
• Mitochondria


  An organelle with a round to oval shape
• Mitochondria


  • Generates energy for the activities of the cell or release energy from food
• Vacuole


  An organelle in the cell filled with cell sap
• Vacuole


  • Stores water, food and metabolic waste
• Chloroplast


  A cell organelle found in plants, algae and cyanobacteria and more concentrated in the leaves, with a high concentration of chlorophyll
• Chloroplast


  • Contains chlorophyll which absorbs light energy for photosynthesis
  • Produce energy for the cell through photosynthesis

  
• Differences between a plant and animal cells

  • Plant cell has chloroplast, vacuole, cell wall
  • Animal cell has no chloroplast, small or no vacuole, no cell wall

  
• Cells


  • Different sizes and shapes
  • Specialized in their functions
  • Combine and work together to form a tissue
  • Tissues form an organ
  • Organs work together to form a system
  • Systems work together to form an organism
• Stem cells


  Special human cells from which all other specialized cells are generated
• Stem cells


  • Can develop into different types of cells
  • Can renew themselves or multiply / divide
  • Are not specialized
• A cell is a basic unit of all organisms which means all organisms are made up of cells
• Microscopic


  Can be seen with the help of a microscope
• Nucleus


  • Acts like the brain of the cell or coordinates the activities of the cell
  • Contains the DNA or holds a genetic code of the organism
• The nucleus can only be found in eukaryotic cells and not prokaryotic cells
• Eukaryotic and prokaryotic cells

  Eukaryotic cells have a defined nucleus while prokaryotic cells do not have a defined nucleus
• Natural Sciences Grade 9
• Notes


  23/Jan/2023
• If an organism has no nucleus it means the DNA is floating around the cell in the nucleoid
• Mitochondrion


  • Where respiration takes place
• Cell membrane


  Plasma membrane
• Cell membrane


  • Controls what enters and leaves the cell
• Chloroplast


  • Where photosynthesis takes place

  
• Cell wall


  The protective structure of the cell which strengthens the cell and gives it structure or shape
• Cell wall


  • Gives the cell shape
  • Makes the cell rigid
• Unicellular organisms


  Organisms consisting of one cell
• Differences between plant and animal cells

  • Plant cell has chloroplast, vacuole, cell wall
  • Animal cell has no chloroplast, small or no vacuole, no cell wall

  
• Cells have different sizes and shapes depending on the type of plant
• Tissue, organ and system

  1. Cells combine and work together form a tissue

  2. Tissues form an organ

  3. Organs work together to form a system
• Stem cells


  • Can develop into different specialized cells such as brain, skin, muscle etc.
  • Can renew themselves or multiply / divide
  • Are not specialized