| Define stem cells | unspecialised cells, that can develop into different types of cells |
| Define differentiation | the process by which a cell becomes specialised for its job |
| Where can you find adult stem cells | - in the bone marrow
- here they divide and differentiate to replace worn out blood cells (erythrocytes and neutrophils) |
| What can you find in embryos | Stem cells that can develop into any type of human cell |
| What do adult stem cells do | they replace damaged cells |
| Where can you find stem cells in plants | in the meristems, where they divide and differentiate into xylem vessels and phloem sieve tubes. |
| How can stem cells be used to cure diseases such as Parkinson's | - the disease causes the loss of a particular type of nerve cell found in the brain
- these cells release a chemical called dopamine, which is needed to control movement
- transplanted stem cells may help to regenerate the dopamine producing cells |
| What are erythrocytes | - they are red blood cells that carry oxygen in the blood
- they have a biconcave disc shape which provides a large surface area for gas exchange
- they have no nucleus so there's more room for haemoglobin |
| What are neutrophils | - a type of white blood cell
- their flexible shape allows them to engulf foreign particles or pathogens
- their cytoplasm contains many lysosomes to break down engulfed particles |
| What are epithelial cells | - cells that cover the surface of organs
- the cells are joined by interlinkingg cell membranes and a membrane at their base |
| What are sperm cells | - male sex cells
- they have a flagellum so they can swim to the egg
- they have lots of mitochondria to provide energy to swim
- the acrosome contains digestive enzymes to enable the sperm to penetrate the surface of the egg |
| What are palisade cells | - cells in the leaves
- does most of the photosynthesis
- they contain many chloroplasts, so they can absorb a lot of sunlight
- the walls are thin, so carbon dioxide can easily diffuse into the cell |
| What are guard cells | - cells found in pairs, with a gap between them to form a stomata |
