specialised cells

• Chiasmata - Sections of DNA which become entangled during crossing over
• Reduction division - Cell division resulting in a haploid cell from a diploid cell.
• Homologous - Matching pair of chromosomes, one from each parent
• Histones - Proteins that form a complex with DNA called chromatin
• Cells within a multicellular organism are differentiated, meaning that they are specialised to carry out specific functions. These cells may have specific adaptations.

  Certain cells have different structures or are shaped in different ways so that they can carry out a specific function.
• All blood cells begin as unspecialised Stem Cells in the bone marrow, which then differentiate through various paths to become specialised cells, such as Erythrocytes and neutrophils
• Erythrocytes are Red Blood Cells. Their function is to transport oxygen from the lungs to respiring tissues.

  • They contain large amounts of Haemoglobin.
  • Many of the organelles present in normal cells are not present in Erythrocytes, to make space for more Haemoglobin and to increase flexibility.
  • They are biconcave- this maximises surface area for oxygen transportation
• Neutrophils are a type of White Blood Cell. They ingest and destroy invading microorganisms and pathogens

  • They have large amounts of Lysosomes, which contain enzymes that kill ingested cells
  • Lobed Nucleus, which allows for greater flexibility.
• Palisade cell : Function- to absorb large amounts of light for photosynthesis
• Root Hair Cells are found in the roots of plants. Their role is to absorb water and minerals in the soil.

  • They have long extensions to increase surface area and the uptake of water and minerals from the soil.
  • Large amount of Mitochondria, which provide more energy for Active Transport.
• Guard cells: Function- to control the opening of the stomata to regulate water loss and gas exchange
• There are four main types of specialised tissues you need to know.

  1. squamous epithelium
  2. cartilage
  3. muscle tissue
  4. ciliated epithelium
• squamous epithelium -

  • Sometimes known as pavement epithelium due to its flat appearance
  • Very thin only one cell thick
  • Present when rapid diffusion across the surface is essential
  • Forms the lining of the lungs

  
• muscle tissue -

  • Needs to be able to shorten in length and contract in order to allow for movement.
  • Different types- cardiac muscle, skeletal muscle.
  • Skeletal muscle fibres contain myofibrils which contain contractile proteins.

  
• cartilage -

  • It is a connective tissue found in the outer ear, nose, at the ends of bones
  • It contains fibres of the proteins elastin and collagen
  • A firm connective tissue composed on chondrocyte cells within a matrix.
  • Can help to prevent rubbing of bone.

  
• ciliated epithelium -

  • Ciliated epithelial cells have hair like cilia structures on one surface.
  • Lines the trachea.
  • Contain goblet cells- these release mucus to trap any unwanted particles, preventing them from reaching the alveoli