1.1 intro to cells Flashcards
what is the cell theory?
- Living organisms are composed of cells and cell products.
- Cells are the smallest unit of life that are capable of survival.
- All new cells are formed only by the division of pre-existing cells. The idea of spontaneous generation has been shown to be impossible.
what are exceptions to the cell theory?
Striated muscles
* Striated muscle cells are made up of fibres and can be much larger than normal animal cells.
* It may have a length up to 300 mm.
* These cells are also multi-nucleated (consists of many nuclei).
Giant algae:
* These are unicellular and grow much larger than regular algae at up to 100 mm in size.
* It is unusual that a large organisms to still consist of only one single cell.
* One example is called Acetabularia, which grows in subtropical waters.
Aseptate fungal hyphae:
* Fungal hyphae are very large cells with multiple nuclei.
* Some have cell walls composed of chitin instead of cellulose, and
have continuous cytoplasm with no end cell wall or membrane, meaning each hypha is an uninterrupted tube-like structure.
* Other hyphae have internal walls called septa.
* This challenges the idea that living structures are composed of discrete cells.
what are the The 7 life functions?
- Nutrition: obtaining food.
- Metabolism: chemical reactions occurring inside cells e.g. cell respiration.
- Growth: increase in size.
- Response: detecting and responding to external environment stimuli.
- Excretion: removal of waste products generated within the cell.
- Homeostasis: maintaining the internal environment of the cell despite external environment fluctuations.
- Reproduction: producing offspring.
- Many unicellular cells have a method of movement, but some remain fixed in a position or drift with water/air currents.
SA to volume ratio?
- the larger the surface area the better but dont want big volume
- to big cant get rid of excess heat, slow waste disposal and food uptake
- cells fold, and elongate to create things like villi to increase SA but keep volume from increasing to much
what are multicellular organisims?
- groups of cells can organise themselves and interact with each other with distinctive properties.
- can achieve more than the sum of what each cell could achieve individually due to the complex interactions between cells.
- This is known as emergent properties
what is cell differentiation?
- Multicellular organisms have many specialised cells, and each will have a specific function e.g. blood or cardiac cells.
- Cells have specialised structures so to perform the specific function more efficiently than if they had many roles.
- This process of specialisation occurs by cell differentiation.
- A group of cells that specialise in the same way to perform the same function are called a tissue
how does gene expression lead to differentiation?
- As all cells contain the same DNA and genes, it is through the expressing some genes that results in cells becoming specialised.
why are stem cells good?
- Stem cells are undifferentiated, which means they have not yet specialised.
- have the potential to
differentiate.
where can you get stem cells from?
- They can be used in medical research and in the treatment of diseases including
leukaemia. - The umbilical cord and bone marrow are common sources of human stem cells.
- can also get embryotic stem cells
what are stem cells used for
- used in leukemia some of the patient’s stem cells are removed and frozen for storage before chemotherapy.
- The patient then undergoes chemotherapy to destroy cancerous cells, and then the stem cells are returned to re-establish in the bone marrow.
- used in Stargardt’s muscular dystrophy is a genetic disease that causes progressive vision loss
- the retinal cells to degenerate, so less light is detected and vision becomes progressively impaired.
- Embryonic stem cells can be injected into the eye to replace the dead cells in the retina, and thus improve vision with no side effects.
Embryonic stem cells.
-Almost unlimited growth potential.
* Can differentiated into any type of cell.
* Has the potential to cure diseases that are incurable at the moment to reduce individual suffering.
* More risks of becoming tumour cells than adult stem cells.
* Less chance of genetic damage due to accumulation of mutations than in adult stem cells.
* Likely to be genetically different from an adult patient receiving the cells.
* Removal of cells from the embryo kills it unless it 1-2 cells are removed.
Cord blood stem cells.
- Easily obtained and stored.
- Commercial collection and storage services already available.
- Completely compatible with the tissues of the adult that grows from the baby so there are no rejection
problems. - Limited capacity to differentiated into different cell types.
- Limited quantities obtained from one baby’s umbilical cord.
- Umbilical cord is discarded whether stem cells are removed or not.
Adult stem cells.
- Difficult to obtain as there are very few cells and they are buried deep within tissues.
- Less growth potential than embryonic stem cells.
- Less chance of malignant tumours developing than from embryonic stem cells.
- Limited capacity to differentiate into different cell types.
- Fully compatible with the adults’ tissue so no rejection problems.
- Removal of stem cells does not kill the adult.
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