Specialised Cells

Red Blood cell - carries oxygen from our lungs our body cells. Then they take carbon dioxide from the cells back to our lungs to be exhaled.

Adaptions:

  • Contain haemoglobin ( a red protein that binds with oyxgen
  • No nucleus so have space for more haemoglobin
  • Small and flexible with a biconcave shape (large SA:V ratio) so can fit through narrow blood vessels.

Neurone - process and transmit impulses from neurone to neurone down a chain.

Adaptions:

  • Have a long fibre (axon) so they can carry messages up and down the body over long distances.
  • Myelin (a fatty sheath) insulates the axon to increase the speed of the nervous impulses along the neuron.

White Blood cell - engulfs and destroys bacteria.

Adaptions:

  • Can change shape and move between cells
  • Large cell size so can effectively engulf bacteria

Ciliated Epidermal cell - keeps the trachea clear of dust and microbes by moving mucus containing dust and microbes.

Adaptions:

  • Has tiny cilia (hairs) that move mucus past them

Sperm cell - fertilises an egg for reproduction.

Adaptions:

  • Has a powerful flagellum with many mitochondria to power it
  • An acrosome (part of the tip of the head) releases enzymes to digest the egg membrane

Egg cell - connects with a sperm cell to become fertilised and produce offspring.

Adaptions:

  • Large cell size to allow for more space for nutrients to be stored inside the cell
  • Cytoplasm contains nutrients to support a developing embryo

Root Hair cell - absorbs water and minerals.

Adaptions:

  • Long thin hair extends from each cell inside the soil, increasing the cell’s SA:V ratio
  • Each root has many thousands of root hairs

Xylem cell - transports water and minerals up the stem to the leaves and flowers.

Adaptions:

  • Dead cells are joined end to end to form a continuous tube so can transport substances through them.
  • Have no cytoplasm
  • Cell walls contain lignin for strength and support

Phloem cell - transports sugars, amino acids, and other substances, up and down the stem to the leaves, flowers, and roots.

Adaptions:

  • Made of tube-like living cells joined end to end so can transport substances through them.
  • Do have cytoplasm

Palisade cell - photosynthesis

Adaptions:

  • Contains the largest number of chloroplasts per cell, maximising the production of photosynthesis and therefore energy for the cell
  • Closely packed together
  • Situated at the top of the plant

Stem cells

All Stem cells can ^^divide and self-renew^^, and can ^^differentiate^^.

The process of a stem cell becoming specialised for a particular function is called cell differentiation.

How they differentiate: the process takes place when genes are expressed in response to certain stimuli, which can activate/deactivate certain genes - this produces particular proteins, which alter the structure of the cell, determining its function.

Embryonic stem cells

  • Can differentiate into any type of body cell (TOTIPOTENT)
  • They are harvested from a 5=7 day old blastocyst.

Adult stem cells

  • Have lost the ability to differentiate into any type of cell but can form a limited number of specialised tissues (PLURIPOTENT)
  • Present in certain adult tissues e.g. bone marrow, skin, and the lining of the intestine.

Induced Pluripotent stem cells (iPS cells)

  • Adult stem cells that are reprogrammed in the lab to become stem cells that can develop into any cell type.

What is the main source of embryos to provide stem cells for research?

Ans = IFV (in vitro fertilisation (outside the body))

Advantages of using stem cells:

  1. Has the potential to treat many diseases which cannot be cured by conventional medicene.
  2. Limbs and organs could be grown in a lab from stem cells and then be transplanted.
  3. They will help scientists learn about human growth and development.
  4. Potential drugs and medicine can be tested on a target group of cells without the use of animal/human testers.

Disadvantages of using stem cells:

  1. Adult stem cells have limited potency to become a cell type.
  2. Using embryonic stem cells have ethical issues.
  3. Immune rejection is high in embryonic stem cells.
  4. Have the potential to from tumours if not properly differentiated and isolated.