This is a common liver cell inside the human body. Organelles are similar to little factories that specialize inside the cell. Be sure to remember the names of the organelles.
The size of an animal cell is 100 micrometer
Free ribosome: site of protein synthesis
Golgi apparatus: processes, packages and secreting organelle of the cell. It modifies protein for export by the cell.
Lysosome: membrane-bound vesicles which contain enzymes. site of protein digestion, food digestion and bacterial digestion.
Nucleus: controls and directs the activities of the cell
Rough endoplasmic reticulum (rER): Site of synthesis of proteins that will be exported from cells
Mitochondria: Site of pathway of aerobic respiration and ATP formation.
Cytoplasm - Site of the chemical reactions of life/Site of metabolic activities
2.3.3 Identify structures from 2.3.1 in electron micro-graph of liver cells.
This is an electron micro-graph of a liver cells.
Note: There is no cell wall in a liver cell. There is a dark patch which is the nucleus. There will be a clear circle which will be lysosome. Mitochondria are circular patches which are darker than the cytoplasm. There is a difference between Golgi apparatus and rough endoplasmic reticulum in the electron micro-graph. The difference is whether it is a patch of curved lines (rER) or just a simple curve line (Golgi).
2.3.4. Compare prokaryotic and eukaryotic cells.
Prokaryotes
- Size - Cells are extremely small, typically 5-10 µm
- Genetic material - Nucleus absent; circular strand of DNA helix in the cytoplasm, not supported by histone protein and it's called a 'nucleoid'.
- Cell wall - Cell wall present (not of cellulose)
- Organelles - Few organelles; membranous organelles absent or very simple
- Protein synthesis -Protein synthesized in small ribosome (705)
- Motile organelles - Some cells have simple flagella, 20 nm in diameter
- Size - Cells are larger, typically 50-150 µm
- Genetic material - Nucleus has distinct nuclear membrane (with pores), and chromosomes of linear DNA helix supported by histone protein
- Cell wall - Cell wall present in plants and fungi
- Organelles - Many organelles bounded by double membrane (e.g. mitochondria, nucleus) or single membrane (e.g. Golgi apparatus, lysosome, vacuole, rough endoplasmic reticulum)
- Protein synthesis - Proteins synthesized in large ribosomes (805)
- Motile organelles - Some cells have cilia or flagella with internal structures, 200 nm in diameter
2.3.5 State three differences between plant and animal cells.
Centrosome, an organelle that lies close to the nucleus in animal cells. This tiny organelle is involved in nuclear division in animal cells.
Vacuole is a fluid-filled space within the cytoplasm, surrounded by a single membrane. Plant cells frequently have a large, permanent vacuole present. By contrast, animal cells may have small vacuole, but these are mostly temporary.
Chloroplasts are the sites where green plant cells manufacture elaborated food molecules by a process known as photosynthesis.
Plant
- Cell wall - Cellulose cell wall present
- Chloroplasts - Many cells contain chloroplasts; site of photosynthesis
- Permanent vacuole - Large, fluid-filled vacuole typically present
- Centrosome - No centrosome
- Carbohydrate storage product - Starch
- Cell wall - No cellulose cell walls
- Chloroplasts - No chloroplasts; animal cells cannot photosynthesis
- Permanent vacuole - No large permanent vacuole
- Centrosome - A centrosome present
- Carbohydrate storage product - Glycogen
2.3.6 Outline two roles of extracellular components.
Extracellular Components
Cell walls is an example of extracellular component. Cellulose microfibrilis are assembled inside the cell and pass out through the plasma membrane to add to the thickness of the wall. When a plant cell grows, the wall becomes attenuated or thinner and so more cellulose must be added to maintain its thickness. The wall maintains the shape of the cell and supports the plasma membrane. When water enters the plant cell by osmosis the wall prevents the expansion of the cell contents. Instead of this pressure builds up inside the cell. This eventually prevents more water from entering. The pressure also makes the cell almost rigid, so that it helps to hold the whole plant up against the whole force of gravity.
Another example is extracellular matrix (ECM) of animal cells.
ECM is made and orientated by the cells within it and takes two general forms. Interstitial matrix is a three-dimensional gel that surrounds cells and fills space. The other form, basement membrane, is a mesh-like sheet formed at the base of epithelial tissues, thin layers of cells that cover internal and external surfaces of the body and that perform protective, secretary or other functions. Basement membrane is a remarkable cellular organizer. In culture on plastic, the cells just sit in a layer but when you put them on basement membrane they differentiate. The cells that line blood vessels form capillary-like tubes all over the culture dish. Neuronal cells send out long, thin extensions. Salivary gland cells join into little balls and begin producing secretory proteins. Such behaviour is characteristic or normal cells. They do not grow unless properly anchored to the matrix.
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