Organelles

Between the cell membrane and the nucleus is the cytoplasm which includes organelles - structures with very specific functions. Organelles working within a cell to keep a cell healthy and performing the cell's functions. Many organelles are membrane bound, but several are not.

Membrane-bound organelles and their general functions:

• Mitochondria - produce ATP.

• Lysosome - contains digestive enzymes which are used within the cell to perform functions such as digesting unwanted or damaged organelles, and can also break down polysaccharides.

• Rough endoplasmic reticulum and Golgi apparatus - process, modify, and package proteins.

• Smooth endoplasmic reticulum - produce lipids needed by the cell such as phospholipids and detoxifies.

• Peroxisomes - lipid metabolism and chemical detoxification.

Non-membrane bound organelles and their functions:

• Ribosomes - protein production.

• Nucleolus - produces ribosomes.

• Cytoskeleton - gives structure to the cell, organizes organelles.

• Centrosome - involved in cell division (mitosis and meiosis).

• Proteasome - breaks down proteins.

Modifications of the cell membrane

There are 3 modifications to the cell membrane that are rather important for many cellular functions.

• Microvilli - increase surface area for absorption and secretion (among other select functions).

• Cilia - move substances in one direction such as mucous (with trapped bacteria) towards the throat or movement of the egg towards the uterus.

• Flagella - in humans, only found as part of sperm for motility.

Cell-to-cell connections

• Tight Junctions - much like sewing cells together and ensuring water and substances do not move between cells (think about how important this is in the digestive tract).

• Desmosomes - VERY strong connections between cells (think about how strong your skin is).

• Gap junctions - not very strong connections, but a pore is created that allows a signal to pass from one cell to the next extremely quickly.