Specialised Cells

• Differentiation

  The process where a cell transforms into a specialised cell for a specific job
• Stem cells

  Undifferentiated cells
• Sperm cell - specialised for reproduction

  • Designed to deliver male DNA to female DNA.
  • They have a LONG TAIL for mobility.
  • They have MANY MITOCHONDRIA for energy.
  • The head is STREAMLINED to make movement more efficient.
  • The head contains ENZYMES that can digest through the membrane of the egg cell.

  A) tail

  B) streamlined head

  C) mitochondria

  D) enzymes

  
• Nerve Cells - specialised for sending electrical signals

  • Carry messages in the form of electrical signals across the body.
  • They are LONG to cover more distance.
  • They have BRANCHED CONNECTIONS called Dendrites to create a large network around the body.

  A) dendrites

  B) axon

  C) myelin sheath

  
• Muscle cells - specialised for contraction

  • They are LONG, so they have space to contract.
  • They are filled with MANY MITOCHONDRIA to transfer energy for contraction.

  A) mitochondria

  
• Root hair cell - specialised for absorbing water and minerals

  • Grow long "hairs" to INCREASE SURFACE AREA for absorption from the soil.
  • Contain NO CHLOROPLASTS as they are found underground and do NOT receive light for photosynthesis.

  A) root hair

  
• Phloem cell - specialised for transporting food substances

  • Cells are joined end to end to form TUBES to transport food in plants.
  • They have very FEW SUBCELLULAR STRUCTURES to help substances flow through easily.

  A) phloem cell

  B) food substances

  
• Xylem cell - specialised for transporting water and minerals

  • Cells are joined end to end to form TUBES to transport water and minerals in plants.
  • They are HOLLOW for easy flow.
  • They are made up of dead cells strengthened with LIGNIN.

  A) water and ions

  B) xylem cell

  
• Differentiation

  Involves the development of DIFFERENT SUBCELLULAR STRUCTURES for various functions.
• differentiation

  In animal cells, most differentiation occurs at an early stage as the organism develops.

  • In MATURE animals' cells, the ability to differentiate is mainly used for REPAIRING AND REPLACING cells, such as skin or blood cells.
• • Plants NEVER lose their ability to differentiate.
• What does the structure of the companion cell suggest about the process that moves dissolved sugars through the phloem tissue?

  Suggests that it requires energy, because it has many mitochondria.

  
• Describe why it's important that dissolved sugars are moved both upwards and downwards in a plant.

  sugars are made in the leaves by photosynthesis and all cells need sugar for respiration, so sugars are transported for storage as starch.
• describe how the cell is adapted to increase the absorption of substances from the soil.

  has a large surface area.

  
• compare the structure of xylem tissue and phloem tissue.

  Structure:

  • xylem is made of dead cells and phloem is made of living cells.
  • both are made of cells
  • phloem cells have pores in their end walls and xylem cells don't.
  • phloem contains cytoplasm and xylem is hollow
  • xylem contains lignin and phloem doesn't
• compare the function of xylem and phloem tissue.

  • xylem transports water and phloem transports sugars
  • xylem is involved in transpiration and phloem is involved in translocation.
  • xylem transports in one direction and phloem transports in 2 opposite directions (upwards and downwards)
  • both transport substances throughout the plant.
• Root hair cell take up water from the soil, its adapted to this function by:

  its large surface area for more osmosis.
• Explain one way sieve tube cells are specialised for their function.


  Has no nucleus to have more space to move food.

  
• Transpiration

  the process by which plants give off water vapor through the stomata in their leaves
• translocation

  A genetic change in which a piece of one chromosome breaks off and attaches to another chromosome.