cells that have developed certain characteristics to carry out particular functions
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how do cells specialise?
they undergo differentiation
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differentiation
process involving the cell gaining new sub-cellular structures for it to be suited to its role
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differentiation in animals
mostly only once
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differentiation in plants
most cells can retain this ability
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specialised cells in animals
- sperm cells - nerve cells - muscle cells
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sperm cells
function: carry male's DNA to the egg cell for reproduction - streamlined head and long tail for swimming - many mitochondria to supply energy to move - acrosome with digestive enzymes to break down outer layers of egg cell
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nerve cells
function: transmit signals from one place to another in the body
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muscle cells
function: specialise to contract and expand quickly
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specialised cells in plants
- root hair cells - xylem cells - phloem cells
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root hair cells
function: take up water by osmosis and mineral ions by active transport - large surface area for more absorption - permanent vacuole to speed up movement - mitochondria for energy for active transport
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xylem cells
function: transports water and mineral ions from roots to shoots
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phloem cells
function: carries products of photosynthesis to all parts of the plant
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stem cell
undifferentiated cell that can undergo division to produce many similar cells
- form when egg and sperm fuse to form zygote - can differentiate into any type of cell - can be cloned - could replace insulin-producing cells
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adult stem cells
if found in bone marrow can form many types of cells
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meristems
- found in root and shoot tips - can differentiate into any type of plant - can differentiate throughout plant life - can be used to make plant clones
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benefits of stem cells in medicine
- replace damage cells - bone marrow transplants (treat blood cell cancers) - can grow organs for transplant - no rejection (if made from patient) - allows testing without animals
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risks of stem cells in medicine
- ethical issues (unused embryos) - no guarantee of success - possible long term effects - mutations - difficult to find donors