Unit 2 - Cell organisation and stem cells Flashcards
Define cell
a single repeating unit of an organism
Define tissue
a collection of differentiated cells that have a common function
Define organ
a group of tissues that work together to carry out a common function
Define organ system
a group of organs that carry out a common function
Define specialised
having particular structure to serve a particular function
Define differentiated
the process by which a less specialised cell develops a distinct form and function,a cell specialising
Why do multicellular organisms need specialised cells?
- complex communication in a multicellular organism
- specialised functions need specialised cells
- maximise efficiency of processes like absorbing nutrients
What features does an erythrocyte have to suit it for its function?
Biconcave disc- maximises SA to carry oxygen
No nucleus- more room for haemoglobin
Flexible- can squeeze through narrow capillaries
What features does a neutrophil have to suit it for its function?
Multilobed nucleus- makes it easier for neutrphils to squeeze through small gaps
Granular cytoplasm- contains many lysosomes which contain enzymes used to attack pathogens
What features does a root hair cell have to suit its function?
Root hairs- increase surface area to maximise uptake of water/minerals from the soil
What features does a sperm cell have to suit it for its function?
Mitochondria- supplies the energy to swim
Tail- allows for movement
Acrosome- contains digestive enzymes which digest protective layers around ovum
What features does a palisade cell have to suit it for its function?
Chloroplasts- absorb a large amount of light
Rectangular- packs closely to form a continuous layer
Chloroplasts are able to move in cytoplasm- so can absorb more light
What features does a guard cell have to suit it for its function?
Cell wall thicker on inside than outside- so cell doesn’t change symmetrically as its volume changes
Gap in the centre- allows gases in and out
What are the 4 main categories of tissues in animals?
Nerve tissue
epithelial tissue
muscle tissue
connective tissue
What are stem cells?
Undifferentiated cells with the potential to differentiate into a variety of the specialised cell types of an organism
Define undifferentiated
An unspecialised cell originating from mitosis or meiosis
Define potency
the ability of a stem cell to differentiate into different cell types
Define totipotent
A stem cell that can differentiate into any type of cell (including extra-embryonic) and form a whole organism
Define pluripotent
a stem cell that can form all types of tissue but not a whole organism
Define multipotent
can only form a range of cells from a certain cell lineage
Give an example of where totipotent cells are found in a human
In a zygote
Give an example of where pluripotent cells are found in a human
Blastocyst
Give an example of where multipotent cells are found in a human
Blood stem cells
What are the characteristics of stem cells?
- can repeatedly undergo cell division
- not adapted to a specific function
- can give rise to specialist cells
- few epigenetic markers
What are stem cells used for in the body?
- growth
- development (of am embryo)
- tissue repair
Where are stem cells found in plants?
Vascular cambium Meristematic tissue (e.g roots and shoots)
How do cells become specialised?
- all cells have the same DNA
- genes are switched on and off by epigenetics
- different proteins are produced in the cell
- so the cell can undergo a specialised function due to the proteins
How long do erythrocytes live for?
120 days
How long do neutrophils live for?
6 hours
