bio p1

• Specialised cell

  A cell that has a particular structure and composition of subcellular structures
• Structural differences between different types of cells


  • Enable them to perform specific functions within the organism
• Cell specialisation


  Undergoing a process known as differentiation
• Components of eukaryotic cells

  • Cell membrane
  • Cytoplasm
  • Ribosomes
  • Nucleus
• Eukaryotic cells have their genetic material (DNA) enclosed within a nucleus
• Eukaryotic cell size

  Usually between 10 and 100 µm
• Animal and plant cells are both eukaryotic cells as their genetic material is packaged in a nucleus
• Nerve cell (neurone)

  • Characteristically elongated structure
  • Allows coordination of information from brain and spinal cord with rest of body
• Nerve cell function

  Conduction of impulses
• Nerve cell adaptations

  • Cell body where most cellular structures are located and protein synthesis occurs
  • Extensions of cytoplasm form dendrites (receive signals) and axons (transmit signals)
  • Axon covered with fatty sheath to speed up nerve impulses
• Muscle cell

  • Contains layers of fibres which allow them to contract
• Muscle cell function

  Contraction for movement
• Muscle cell adaptations

  • Three types: skeletal, smooth and cardiac
  • Protein filaments that can slide over each other causing contraction
  • High density of mitochondria to provide energy for contraction
  • Skeletal muscle cells fuse together during development
• Sperm cell

  • Mobile, with a tail to propel it forward
  • Head contains haploid nucleus and acrosome with digestive enzymes
  • Mid-piece packed with mitochondria to provide energy for tail movement
• Sperm cell function

  Reproduction (pass on father's genes)
• Prokaryotic cell

  • Genetic material not enclosed in a nucleus, found as a single loop of DNA
  • May also contain smaller circular pieces of DNA called plasmids
  • Cell membrane surrounded by a cell wall (usually made of peptidoglycan)
  • Much smaller than eukaryotic cells, around 1 µm
• Root hair cell

  • Extension of cytoplasm to increase surface area for absorption of water and minerals
  • Thinner walls than other plant cells for easier water movement
  • Permanent vacuole contains concentrated cell sap to maintain water potential gradient
  • Mitochondria for active transport of mineral ions
• Root hair cell function

  Absorption of water and mineral ions from soil
• Xylem vessel

  • Cells lose top and bottom walls to form continuous tubes for water transport
  • Cells are essentially dead, with no organelles or cytoplasm
  • Outer walls thickened with lignin to strengthen the tubes
• Xylem function

  Transport tissue for water and dissolved ions
• Phloem cell

  • Cells retain some subcellular structures and are living
  • Cells joined end-to-end with holes in end walls (sieve plates) to allow flow of sugars and amino acids
  • Few subcellular structures to aid flow of materials
• Phloem function


  Transport of dissolved sugars and amino acids
• Eukaryotic cells

  Have subcellular structures, each carrying out a particular function
• Organelles

  Subcellular 'compartments' where specific processes take place within the cell
• Main subcellular structures in animal cells

  • The nucleus
  • Cell membranes
  • Mitochondria
  • Ribosomes
  • Cytoplasm
• Some cellular structures can only be seen when viewed with an electron microscope
• Cell structures table
• Additional subcellular parts found in plant cells

  • A cell wall made of cellulose (algal cells also have this structural feature)
  • A permanent vacuole filled with cell sap
  • Chloroplasts
• Plant cells found in the leaf and stem may also contain chloroplasts
• Function of neurones

  Conduction of impulses
• Neurones

  • Has a cell body where most of the cellular structures are located and most protein synthesis occurs
  • Extensions of the cytoplasm from the cell body form dendrites (which receive signals) and axons (which transmit signals), allowing the neurone to communicate with other nerve cells, muscles and glands
  • The axon (the main extension of cytoplasm away from the cell body) is covered with a fatty sheath, which speeds up nerve impulses. Axons can be up to 1m long in some animals
• Muscle cells

  • Contain layers of fibres which allow them to contract
  • There are three different types of muscle in animals: skeletal, smooth and cardiac (heart)
  • All muscle cells have layers of protein filaments in them. These layers can slide over each other causing muscle contraction
  • Muscle cells have a high density of mitochondria to provide sufficient energy (via respiration) for muscle contraction
  • Skeletal muscle cells fuse together during development to form multinucleated cells that contract in unison
• Function of sperm cells

  Reproduction (pass on fathers genes)
• Sperm cells

  • The head contains a nucleus which contains half the normal number of chromosomes (haploid, no chromosome pairs)
  • The acrosome in the head contains digestive enzymes that can break down the outer layer of an egg cell so that the haploid nucleus can enter to fuse with the egg's nucleus
  • The mid-piece is packed with mitochondria to release energy (via respiration) for the tail
  • The tail rotates, propelling the sperm cell forwards (allowing it to move/swim)
• Function of root hair cells

  Absorption of water and mineral ions from soil
• Root hair cells

  • The root hair is an extension of the cytoplasm, increasing the surface area of the cell in contact with the soil to maximise absorption of water and minerals
  • Thinner walls than other plant cells so that water can move through easily (due to shorter diffusion distance)
  • Permanent vacuole contains cell sap which is more concentrated than soil water, maintaining a water potential gradient
  • Mitochondria for active transport of mineral ions
• Function of xylem vessels


  Transport tissue for water and dissolved ions
• Xylem vessels

  • No top and bottom walls between cells to form continuous hollow tubes through which water is drawn upwards towards the leaves by transpiration
  • Cells are essentially dead, without organelles or cytoplasm, to allow free passage of water
  • Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant
• Function of phloem cells


  Transport of dissolved sugars and amino acids
• Phloem cells

  • Made of living cells (as opposed to xylem vessels which are made of dead cells) which are supported by companion cells
  • Cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes which allow sugars and amino acids to flow easily through (by translocation)
  • Cells also have very few subcellular structures to aid the flow of materials