Describe the structure and function of the cellular membrane, including the role of proteins, lipids and sugars in the membrane.

The cell membrane (plasma membrane) is a thin semi-permeable membrane that surrounds the cytoplasm of a cell. Its function is to protect the integrity of the interior of the cell by allowing certain substances into the cell, while keeping other substances out. It also serves as a base of attachment for the cytoskeleton in some organisms and the cell wall in others. Thus the cell membrane also serves to help support the cell and help maintain its shape.

Another function of the membrane is to regulate cell growth through the balance of endocytosis and exocytosis. In endocytosis, lipids and proteins are removed from the cell membrane as substances are internalized. In exocytosis, vesicles containing lipids and proteins fuse with the cell membrane increasing cell size. Animal cell, plant cell, prokaryotic cell, and fungal cell have plasma membranes. Internal organelles are also encased by membranes.

he cell membrane is primarily composed of a mix of proteins  and lipids. Depending on the membrane’s location and role in the body, lipids can make up anywhere from 20 to 80 percent of the membrane, with the remainder being proteins. While lipids help to give membranes their flexibility, proteins monitor and maintain the cell's chemical climate and assist in the transfer of molecules across the membrane.

The cell membrane contains two types of associated proteins. Peripheral membrane protein  are exterior to and connected to the membrane by interactions with other proteins. Integral membrane protein  are inserted into the membrane and most pass through the membrane. Portions of these trans membrane proteins are exposed on both sides of the membrane. Cell membrane proteins have a number of different functions.  

Structural proteins help to give the cell support and shape.

Cell membrane receptor proteins help cells communicate with their external environment through the use of hormones , neurotransmitters, and other signaling molecules.

Transport proteins, such as globular proteins, transport molecules across cell membranes through facilitated diffusion.  

Glycoproteins have a carbohydrate chain attached to them. They are embedded in the cell membrane and help in cell to cell communications and molecule transport across the membrane.

Blood Types

Blood transfusions are a lifesaving treatment for many Americans. Blood transfusions are needed for many reasons, including surgery, after accidents, and for patients with chronic illnesses and cancer.

Blood cannot be artificially made, so doctors rely on volunteer donations. To keep the blood supply safe, every donation is tested for blood type and checked for infectious diseases.

O negative. This blood type doesn't have A or B markers, and it doesn't have Rh factor.

O positive. This blood type doesn't have A or B markers, but it does have Rh factor. O positive blood is one of the two most common blood types (the other being A positive).

A negative. This blood type has A marker only.

A positive. This blood type has A marker and Rh factor, but not B marker. Along with O positive, it's one of the two most common blood types.

B negative. This blood type has B marker only.

B positive. This blood type has B marker and Rh factor, but not A marker.

AB negative. This blood type has A and B markers, but not Rh factor.

AB positive. This blood type has all three types of markers — A, B, and Rh factor.

(sorry if im wrong)

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