Year 9

• Nucleus:

  • Controls the cell’s activities
  • Contains genetic material
• Cell membrane:

  • Controls the movement of substances into and out of the cell
• Cytoplasm:

  • Jelly-like substance where chemical reactions take place
• Mitochondria:

  • The site of respiration
• Ribosome:

  • Site of protein synthesis (proteins are made)
• Cell wall:

  • Strengthens the cell
  • Made of cellulose
• Chloroplast:

  • Site of photosynthesis
  • Contains chlorophyll, a green pigment which absorbs light
• Vacuole:

  • Filled with cell sap to help keep the cell turgid (stiff) to provide support
• DNA:

  • The molecule that holds the genetic information in a cell
• Plasmid:

  • A small loop of DNA, only found in prokaryotic cells (bacteria)
• Eukaryotic cell:

  • DNA contained within nucleus (plant and animal)
• Prokaryotic cell:

  • DNA not contained in nucleus (bacteria)
• Cell differentiation:

  • Cells become specialised by developing different sub-cellular structures to help them function
• Chromosomes:

  • Found in nucleus of a cell
  • Made of DNA
  • Usually found in pairs
  • Humans have 46 chromosomes (23 pairs) in a body cell
• Mitosis – cell division:

  • Cell grows, number of sub-cellular structures increases and DNA replicates to form two copies of each chromosome
  • Nucleus divides and one set of chromosomes is pulled to each end of the cell
  • Cytoplasm and cell membranes divide to form two identical cells
• Stem cells:

  • An undifferentiated cell of an organism capable of giving rise to many more cells
• Stem cells are undifferentiated cells capable of giving rise to many more cells of the same type
• Stem cells can help conditions such as diabetes and paralysis
• Embryo, adult, and meristem stem cells can be cloned and differentiated into most types of human cells
• Adult bone marrow can form many types of cells including blood cells
• Stem cells can differentiate into any type of plant cell throughout the life of the plant
• Microscopy
• Magnification = size of image ÷ size of real object
• Start with lowest magnification to focus image
• Resolution is the measure of the level of detail you can see in the image using a microscope
• Light microscopes use visible light and lenses to produce an enlarged image with a maximum magnification of 1500x and low resolution
• Electron microscopes have much higher magnification and resolution than light microscopes
• Transport across membranes
• Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration
• Occurs in solutions and gases
• Osmosis is the diffusion of water from a dilute to concentrated solution across a partially permeable membrane
• Movement of water across cell membranes into and out of cells
• Active transport is the movement of particles from a low concentration to a high concentration using energy from respiration
• Absorption of mineral ions into plant root hairs and absorption of sugar molecules in the gut
• Levels of organisation
• Cell is the smallest unit for building all organisms
• Tissue is a group of cells with a similar structure and function working together e.g., muscle tissue
• Organ is a group of different tissues working together e.g., heart
• Organ system is a group of different organs working together e.g., circulatory system
• Organism is a living thing capable of the 7 life processes