The Cell

The Plasma Membrane

The plasma membrane provides a boundary for the cell, maintaining its integrity.  The protein molecules embedded in it perform various functions; as markers to identify cells, as receptors for certain hormones and other molecules and as transport mechanisms.

The plasma membrane is made of a bi layer of phospholipid molecules arranged with their non-polar tails pointing towards each other.

Cholesterol molecules help to stabilise the flexible bi-layer structure and prevent breakage.

Protein molecules and protein hybrid molecules may be found on the outer surface of the bi-layer or more likely extending all the way through the membrane.

Membrane channels

Gated channel proteins form tunnels through which specific molecules may pass (as long as the gates are open).

Transported molecules move from an area of high concentration to low concentration.



The Cell

Cell membrane as we have seen provides protection, markers in the form of proteins which also provide receptor points and also channels for transportation.

Ribosomes these are the protein factories of the cell which attach to the rough endoplasmic reticulum and synthesise proteins that leave cells via the golgi apparatus.

Smooth Endoplasmic reticulum processes lipids which are incorporated into cell membranes and steroid hormones.  It  also synthesises some carbs, which exit through the golgi apparatus where they are combined with protein into forming glyco proteins.

Mitochondria; This is the powerhouse of the cells, where ATP is synthesised and converted into energy for all of the cell processes.

Nucleus: Contains DNA blueprint for the cells.  It houses the genetic code which in turn dictates protein synthesis to provide cell transport, metabolism and growth.

Nucleolus  plays an essential role in the formation of ribosomes.

Lysosomes are the digestive system of the cell

Peroxisomes use enzymes to break down and cleanse the waste from the cell.

Cytoskeleton provides structure and support to the cell and its organelles and can also assist with cell movement and form cell extensions.

Cilia and Flagella are hair like extensions which serve to move substances across the surface of the cell or propel sperm cells.


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