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Title: Cell theory, cell specialization and cell replacement
Description: International Baccalaureate Biology SL Topic 1.1 2016 Clear and detailed notes of topic 1.1 from the book and lecture
Description: International Baccalaureate Biology SL Topic 1.1 2016 Clear and detailed notes of topic 1.1 from the book and lecture
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Cell theory, differentiation, stem cells
Topic 1
...
Cell Theory
1
...
Cells are the smallest units of life
3
...
Only after exposure to pre-existing cells was life able to
re-establish itself in the sterilized chicken broth
...
Metabolism
■ All chemical reactions in cells
■ Energy being converted from one form to another
2
...
Reproduction
■ Either asexual or sexual
■ Hereditary molecules being passed to offspring
4
...
Homeostasis
■ Organisms maintain a constant internal environment or at least close
to optimal state
6
...
Excretion
■ Unusable or toxic compounds need to be disposed of
■ Essential for the organism
1
Cell theory, differentiation, stem cells
Topic 1
...
However, not all genes of the cell’s genome will be
expressed
○ This means that each cell will become a specific type of a cell depending on
which DNA segment (gene) becomes active
➢ Some cells can keep dividing after differentiation
○ For example, skin cells divide in order to heal wounds
○ Die very often and replace themselves
➢ Some are unable to do that
○ For example, nerve and muscle cells
○ Don’t die, until you die
○ Difficult to be repaired
Limiting cell size
➢ Most cells can only be seen by using a microscope
○ Cells are so small due to a principle called “the surface area to volume ratio”
■ As cells increase in volume, their surface area also increases, but at a
much slower rate
2
Cell theory, differentiation, stem cells
Topic 1
...
Therefore, they
need a lot of nutrition and have a lot of waste
But not all cells follow this norm
➢ Some cells have evolved into different shapes
○ Cells that are large in size have modifications that allow them to function
efficiently
■ Changes in shape, in- or out- foldings => increase of surface area
○ Some atypical examples
■ Striated muscles => flat and long rather than spherical
■ Giant algae => interconnected with each other with small openings
■ Acetate fungal hyphae => the roots of a certain fungi, physically
connected with each other, however they
Title: Cell theory, cell specialization and cell replacement
Description: International Baccalaureate Biology SL Topic 1.1 2016 Clear and detailed notes of topic 1.1 from the book and lecture
Description: International Baccalaureate Biology SL Topic 1.1 2016 Clear and detailed notes of topic 1.1 from the book and lecture