2.1 Cell Structure

Ultrastructure of a Eukaryotic Cell

A eukaryotic cell is defined as having a true nucleus
The nucleus is incased in an envelope which has pores on the surface
These nulear pores allow for the movement of molecules into and out of the nucleus e.g. RNA
Within the nucleus, there is a nucleolus which is the site of ribosome production
The nucleus also stains the darkest
The rough endoplasmic reticulum is a series of many flattened sacs studded with ribosomes for protein synthesis
The rough ER processes proteins produced by the ribosomes
The smooth endoplasmic reticulum is a series of membrane bound sacs which produces and processes lipids
The golgi appratus is a series of fluid filled, flattened, and curved sacs with vesicles that surround the edges
The golgi body proccesses and packages proteins and lipids but also produces lysosomes
The mitochondria has a double membrane and contains all the enzymes needed for respiration
Centrioles are hollow cylinders containing microtubles which are at right angles to each other
Centrioles are involved in cell division
Ribosomes are the site of protein synthesis
Lysosomes are a vesicle bound by a single membrane which contains digestive enzymes

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Proteins are produced on the ribosomes
Proteins that are produced by the ribosomes studded on the rough ER are processed by the rough ER
The proteins are then packaged into vesicles and transported to the golgi apparatus from the rough ER
At the golgi apparatus, the proteins are modified (cis face - trans face)
From the golgi apparatus, the proteins are again packaged into a vesicle to be transported around the cells wherever they are needed
Some proteins, e.g. extracellular enzymes, leave the cell by exocytosis

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A prokaryotic cell is defined as having no true nucleus
The cell wall is a rigid outer covering made of peptidoglycan
The capsule is a protecive, slimy layer which helps the cell retain moisture and adhere (stick) to surfaces
The plasmid is a circular piece of DNA (deoxyribonucleic acid)- this is instead of a nucleus
The flagellum is a tail-like structure which allows the cell to move by rotating it
The pili are hair-like structures that allow a bacterial cell to attach to other bacterial cells
The ribosomes are the site of protein production

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