Cells

• Characteristics of living things

  • Movement
  • Reproduction
  • Sensitivity
  • Nutrition
  • Excretion
  • Respiration
  • Growth
• Levels of organisation within organisms

  • Cell
  • Tissue
  • Organ
  • System
  • Organism
• Multi-cellular organisms must have specialised tissues, organs and organ systems
• This helps them to exchange substances with the environment, transport substances within their body, and communicate between cells
• Organ systems in the human body

  • Digestive
  • Respiratory
  • Skeletal
  • Circulatory
  • Excretory
  • Reproductive
  • Nervous
• Cells contain smaller units called organelles
• Cytoplasm


  Jelly-like liquid where chemical reactions in the cell happen
• Cell membrane


  Semi-permeable and controls the movement of substances in and out of the cell
• Nucleus


  Contains chromosomes with genetic instructions where proteins are made
• Ribosomes


  Where proteins are made to make new cells
• Mitochondria


  Where energy is released in respiration
• Chloroplasts


  Green structures which contain chlorophyll for photosynthesis
• Vacuole


  A space inside the cell filled with a watery liquid that helps the cell keep its shape and stores nutrients
• Cell wall


  A tough supporting structure that helps the cell keep its shape, found on the outside of the cell and made of cellulose
• Bacterial cells have a cell membrane, cytoplasm and ribosomes like animal and plant cells, but their cell wall is not made of cellulose
• Organelles found only in bacterial cells


  • Loop of DNA
  • Plasmids
  • Flagellum
• Specialised cells


  • Leaf palisade cell
  • Root hair cell
  • Red blood cell
  • White blood cell
  • Sperm cell
  • Neurone
• Adaptation and function of specialised cells

  • Leaf palisade cell: lots of chloroplasts to trap sunlight for photosynthesis
  • Root hair cell: long and thin to increase surface area for water absorption
  • Red blood cell: no nucleus, disc-shaped for oxygen transport
  • White blood cell: has a nucleus to make antibodies
  • Sperm cell: tail to swim to ovum
  • Neurone: long to transmit electrical signals