Stem cells

Stem cells

Unspecialised cells that can differentiate into different types of cell

Differentiate

The process by which a cell becomes specialised

Embryonic stem cells

Found in the blastocyst

Placenta and umbilical cord blood stem cells

Found in the foetus

Adult stem cells

In foetus, baby and through life

Induced pluripotent stem cells

Adult stem cells induced into embryonic stem cells

Stem cells in plants

They are needed to make new plant tissue as plants are always growing. They are found in the meristem and cambium meristem cells can differentiate into xylem tissue and phloem sieve tube

Stem cells in medicine

They can be grown into new tissue and used to test the effectiveness, side effects and toxicity of new drugs. They can also be grown and studied to see how they develop into different cell types and cell function can be studied using them

How do they become specialised

Under certain conditions genes can be switched on or off meaning only certain genes are transcribed and translated. Genes that are expressed produce proteins which modify the cell and in turn determine its structure and function

Self renew importance

Stem cells can self renew which I important because if they were unable to they would quickly run out and this allows them to maintain a pool of stem cells through a persons life

Differentiate importance

Specialised cells are unable to replicate themselves even though they are used up, damaged or die all the time so differentiation ensures specialised cells can always be replaced

Adaptations of erythrocytes

Carry oxygen in the blood (red blood cells) Bioconcave disc shape which provides a larger surface area for gas exchange and they have no nucleus so have room for more haemoglobin.

Adaptations of neutrophils

Defend body against disease (white blood cells). Have a flexible shape which allows them to engulf pathogens. Contain mostly lysosomes in their cytoplasm to break down the engulfed pathogens

Epithelial cells

Cover the surface of organs and are joined by interlinking cell membranes at their base. Have micro-villi folds in the cell membrane that increase the cells surface area. Squamous epithelia are very thin to allow for diffusion. Collimated epithelia have cilia that beat to move particles away

Sperm cells

Male gametes. Have a flagellum so they can swim to the egg. Contain lots of mitochondria to provide energy for them to swim. Their acrosome contains digestive enzymes to enable the sperm to penetrate the surface of the egg

Palaside mesophyll cells

Found in leaves and carry out photosynthesis. Contain lots of chloroplast so can absorb lots of sunlight. Have thin walls so CO2 can diffuse into the cell

Root hair cell adaptation

Absorb water and mineral ions from the soil. Have a large surface area for absorption amd a thin permeable ćell wall so water and ions can enter. Cytoplasm contains extra mitochondria to provide the energy needed for active transport

Neurone cell adaptations

Carry electrical impulses. Have long axon so they can carry messages over a long distance

Totipotent stem cell

Stem cells which have the ability to turn into any type of cell found in embryos up to the 32 cell stage

Pluripotent stem cells

Stem cells which have the ability to turn into a number of different cells found on embryos with up to 150 cells before implantation

Multipotent stem cells

Stem cells which have the ability to turn into a specialised group of cells

Unipotent stem cells

Stem cells which can only differentiate into one type of cell