Prokaryotic and Eukaryotic Cells

Prokaryotic cells have simpler internal structures. They have no membrane enclosed organelles. For example: bacteria and archaea.

Eukaryotic cells are larger and more structurally complex. Examples are algae, fungi and protozoa. Multicellular plants and animals consist of eukaryotic cells and they contain membrane enclosed organelles.
The nucleus contains the cells genetic information and is the site of transcription.
The mitochondria is incharge of energy generation and the chloroplasts in plants aids in photosynthesis.

The cell membrane is a thin structure about 8nm thick separating the inside of the cell from its environment. It is highly selective and enables the cell to concentrate specific metabolites and excrete waste materials. It is called a phospholipid bilayer which means it has both hydrophobic and hydrophyllic components. The fatty acids pointing inward to form a hydrophobic environment while hydrophillic components point outwards exposed to the aqueous environment. The arrangement is mostly stable. Cytoplasmic membrane proteins have hydrophobic external surfaces in the regions of the protein that span the membrane whilst hydrophillic components make contact with the aqueous environment. Hydrogen bonds and hydrophobic interactions stabilize the structure of the membrane. Magnesium and calcium ions combine ionically with the negative charges of the phospholipids.

Membrane proteins interact with proteins that bind substrates or process large molecules for transport into the cell. The inner side of the cytoplasmic membrane faces the cytoplasm and interacts with proteins involved in energy yielding reactions and other important cellular function.
Integral membrane proteins are firmly embedded in the membrane. Some not embedded in the membrane but associate with the membrane surfaces and function as if they were membrane bound proteins for example periplasmic proteins. Some are lipoproteins. The membranes are quite fluid. Eukaryotes have sterols which add rigidity, while prokaryotes for example bacteria, hopanoids might be present to stabilize the membrane.

The cell membrane uses it’s permeable membrane to prevent the passive leakage of cytoplasmic constituents into or out of the cell.
Proteins are located in the membrane. Those that are enzymes are involved in bioenergetic functions and transport.
The cell membrane is involved in energy conservation. Inside of the cell has a net negative charge whereas outside of the cell has a net positive charge. Charge separation is a form of energy called proton motive force.

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