Cell structure and organisation

• Cell structure

  • Nucleus
  • Cytoplasm
  • Mitochondria
  • Golgi body
  • Endoplasmic reticulum
  • Ribosomes
  • Vacuole
  • Cell wall (plant cell)
  • Chloroplasts (plant cell)
  • Centrioles (animal cell)
• Nucleus


  • Contains DNA which with protein comprises the chromosomes
  • Has a nuclear envelope with pores that allow mRNA and nucleotides in from cytoplasm
• Ribosomes


  • Site of protein synthesis
  • Large and small subunit
  • 70s in prokaryotes, 80s in eukaryotes
• Endoplasmic Reticulum (ER)


  • Rough ER covered in ribosomes for protein synthesis
  • Smooth ER for synthesis and transport of lipids
  • Links with nucleus
  • Transports proteins after protein synthesis
• Golgi body


  • Modifies and packages proteins into vesicles
  • Produces secreting enzymes
  • Secretes carbohydrates
  • Produces glycoproteins
  • Transports and stores lipids
• Vacuole


  • Forms lysosomes and digestive enzymes
  • Contains cell sap and is surrounded by the tonoplast membrane
• Cell wall (plant cell)

  • Made from cellulose microfibrils and pectin
  • Fully permeable for the transport of substances
  • Provides strength to the plant
  • Communicates through the cell wall via plasmodesmata
• Mitochondria


  • Site of aerobic respiration
  • Cylindrical shape for large surface area and reduced diffusion distance
  • Double membrane
  • Inner membrane folded into cristae (has stalked particles involved in ATP Synthesis)
  • Outer membrane controls entry and exit of materials
• Chloroplasts (plant cell)


  • Enables plants to make glucose by photosynthesis
  • Can carry out photosynthesis as they have ribosomes
  • Inner membrane (grana) stacked like coins and connected by lamellae
• Centrioles (animal cell)


  2 cylinders of microtubules that form the spindle during cell division
• Apoplast


  The space outside cells where solution moves (main way that water crosses cell)
• Symplast


  The pathway where strands of cytoplasm pass through narrow pores and pits to connect cells
• Plasmodesmata


  Narrow pores and pits where strands of cytoplasm pass to connect plant cells
• Prokaryotes


  • Lack membrane bound organelles
  • DNA loose in cytoplasm
  • 70S ribosomes
• Viruses


  • Have a protein coat (capsid) around a nucleic acid (DNA or RNA)
  • Not a living thing and not a cell (needs a host cell)
  • Injects its genetic material into a living cell
• New cells are formed from other existing cells
• Cell is a fundamental unit of structure, function, and organisation in all living organisms
• Animal and plant cells are eukaryotic
• They contain membrane bound organelles
• DNA is found within the nucleus
• Cell walls are made of cellulose
• Aerobic respiration occurs within mitochondria
• Endosymbiotic theory


  The presence of 70S ribosomes and DNA in both mitochondria and chloroplasts suggests that they were once free-living cells engulfed by ancient bacteria and a symbiotic relationship was developed
• Differentiation and specialisation


  • Tissue - group of specialised cells of the same type that work together to carry out a particular function
  • Organ - several tissues working together to perform a specific function
  • Organ system - a collection of organs working together to perform a function
  • Organism - all the systems of a body working together, making up an organism
• Epithelial tissue


  • No blood vessels
  • May have nerve endings
  • Forms a continuous layer lining the internal and external surfaces of the body
• Types of epithelial tissue

  • Cuboidal epithelium
  • Ciliated epithelium
  • Squamous epithelium
• Cuboidal epithelium


  • Single layer of cuboidal cells on a basement membrane
  • Line many glands and ducts (e.g. tubules of kidney)
  • May have microvilli on surface to increase surface area for reabsorption of substances
• Ciliated epithelium


  • Cilia move materials from one place to another
  • Line fallopian tubes, trachea, bronchi and bronchioles
• Squamous epithelium

  • Flattened cells on a basement membrane
  • Form alveoli walls and line renal (Bowman's capsule of the nephron in the kidneys)
• Muscle tissue


  • Skeletal muscle
  • Smooth (involuntary) muscle
  • Cardiac muscle
• Skeletal muscle


  • Attached to bones
  • Generates locomotion in mammals
  • Voluntary muscle that tires easily
• Smooth (involuntary) muscle


  • Fibres are spindle-shaped cells
  • Contracts rhythmically and doesn't tire
  • Found in skin, walls of blood vessels, respiratory and digestive tracts
  • Controlled by nerves from autonomic system
• Cardiac muscle


  • Contracts rhythmically and doesn't tire
  • Only found in the heart
  • Properties are between skeletal and smooth muscle
  • Myogenic - can contract without nervous input
• Connective tissue


  • Connects, supports or separates tissues and organs
  • Contains elastic and collagen fibres in an extracellular fluid or matrix
  • Strong tissue
  • Contains fat storing cells (adipocytes) and cells of the immune system