Specialised cells

• • Eukaryotic cells are specialised to perform particular functions.​
  • Specialisation occurs through differentiation from stem cells. ​
  • The structure of cells and how this relates to their function:
  • Erythrocytes ​
  • Neurones ​
  • Squamous epithelial cells ​
  • Sperm cells ​
  • Ova ​
  • Striated muscle cells 
• Erythrocyte:

  Cells that contain haemoglobin, an oxygen-transporting protein that gives blood its red colour.​

  ​

  • haemoglobin that carries oxygen ​
  • lacks nucleus, endoplasmic reticulum and mitochondria​
  • small and flexible so can squeeze along narrow capillaries ​
  • biconcave shape that gives large surface area to volume ratio
• • Sensory neurons send information from the eyes, ears, nose, tongue, and skin to the brain.​
  • Relay (Interneurons) transfer signals between sensory and motor neurons ​
  • Motor neurons carry messages from the CNS to the rest of the body.
• Neurons:

  What is their function?​

  • To transmit information electrically and chemically​.

  How do they do this?​

  • Receiving input from another neuron, or a sensory receptor​
  • Conducting an action potential down the axon​

  Then sending a chemical message across a synapse

  ​How are they adapted for this role?

  • ​Highly branched to make lots of connections
  • Axon is long and thin (like a wire) to transmit information quickly and far, and insulated with a myelin sheath​
  • They have important protein channels and carriers across their cell-surface membrane
• spermatozoon:

  The reproductive cell of human males, carried in semen, that fertilizes the ovum to create a new human being. ​

  ​

  • nucleus contains 23 chromosomes (haploid nucleus)​
  • head – acrosome​
  • acrosome - enzyme to digest a path through the outer membrane (zona pellucida) of egg (ovum)​
  • mid-section contains large numbers of mitochondria - aerobic respiration​
  • tail – motility
• Ova:

  Connect with the male sperm cell in order to become fertilised and produce offspring. Create the right environment to enable fertilisation by the sperm. ​

  ​

  • nucleus contains 23 chromosomes (haploid nucleus)​
  • large cytoplasm, organelles and energy store​
  • outer membrane (zona pellucida)​
  • corona radiata – outer protective layer, supplies protein to the fertilised egg cell
• Squamous epithelial cell:

  • Flattened – thin (the thinnest of all epithelial cell-types) a large surface area​
  • one cell-layer thick​
  • bound together by tight junctions, forming selective barrier​
  • Substances like oxygen + water can easily pass through them
  • protection, secretion + absorption
  • Function as mediators of filtration and diffusion. Due to simple and thin construct, they allow for easy transmembrane movement of small molecules.
  • outer layer of your skin (epidermis).​
  • lining of intestines.​
  • lining of respiratory tract.​
  • lining of abdominal cavity.​
  • Your sweat glands
• Skeletal muscle cell:

  • Functions to contract in response to a stimulus (voluntary control). Producing movement, sustaining body posture and position, maintaining body temperature, storing nutrients, and stabilising joints. 
  • Elongated cells with a very elastic and resistant plasma membrane, called the sarcolemma​
  • They look striated, or striped​
  • Nuclei located at the outer edge of the cell​
  • Many mitochondria​
  • flexible muscle fibres