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BIO152 WK1 Lecture Notes
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BIO152 Sem 2 2018 Lecture Notes
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BIO152 WEEK 1Introduction to Cells
Cells
- The most basic unit of life is the cell.
- Organisms are either single celled or multicellular
- All life is cellular
The Cell Theory
- Early microbiologist, Robert Hooke, discovered that the smallest units of life are cells
(1665) and that cells can be seen with a compound microscope.
- Cell theory is that all living things are composed of cells
- Antoni van Leeuwenhoek observed animalcules (late 1600s to early 1700s).
- He observed this through a single-lens microscope on rainwater and material
scraped from his teeth.
- Cell theory explains the relationship between life and properties of the cel
- All organisms consist of one or more cell
- The cell is the basic unit of all organisms
- All cells come from pre-existing, living cells
Common functions of cells
- Bacterial, protozoan, plant, animal
- Duplicate DNA
- Use DNA and RNA to make proteins
- Handle energy transfer
- Regulate exchange of materials
Common structures of cells
- Plasma membrane; outer covering that separates the cells interior from the
environment
- Cytoplasm; material within the cell with other cellular components
- DNA; the genetic material of the cell
- Ribosomes; structures that make proteins
What limits cell size?
- Cells are limited in size despite their shapes
- Cell range; bacteria and archaea, 1-5 micrometres and higher plants and animals, 10-
100 micrometres
- To successfully survive, cells need to exchange gases, nutrients, wastes and other
molecules with their environment and transport material within the cell
Problems for large cells
- Information transfer from the nucleus to the rest of the cell
- Rate of difusion of nutrients and wastes in and out of the cell
- Not enough surface area (e.g surface to volume ratio)
, - A cell that is too large in volume does not have the surface area of plasma
membrane to efectively transport particles in and out of the cell
Solutions to limit size
- Cells remain unicellular but are small and successful, e.g. bacteria
- Organisms become large, multicellular and complex but cells remain small e.g. plants
and animals
Prokaryote vs. Eukaryote
Prokaryote:
- Single celled
- Rapid growth
- Small size, 0.5-3 micrometres
- Does not have a nucleus
- No membrane bound organelles
- Single circular chromosomal DNA
- Small 70S ribosomes
- Cell wall is mostly present
- Cell division is binary fssion
- E.g. Bacteria and archaea
Eukaryote:
- Single or multi celled
- Growth is slow
- Large size, 5-20 micrometres
- Has a nucleus
- Has many membrane bound organelles
- Double linear chromosomal DNA
- Large 80S ribosomes
- Cell wall is present in some
- Cell division by mitosis
- E.g. animals and plants
Animal Cell (Eukaryote)
- Organelles that are membrane bound require membrane fusion events to exchange
materials
- Divide by mitosis – chromosomes replicate and are distributed equally into daughter
cells
Plant Cell (Eukaryote)
- Plant cells have walls containing chitin and large vacuoles
Bacterial Cell (Prokaryote)
- The common bacterial, E.coli has chromosomal material (1300micrometres) longer
than itself so it is folded and packed tightly (nucleoid) to ft inside the cell (1-2
micrometres).
- Division by binary fssion
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