What Is The Function Of The Cell Membrane – What is the plasma membrane? What does the plasma membrane do? View a plasma membrane definition, plasma membrane function, and plasma membrane structure. Updated: 21/11/2023

The illustration of the plasma membrane is from your lesson. Test your memory of the structural components and their organization by identifying components A-D.

What Is The Function Of The Cell Membrane

What Is The Function Of The Cell Membrane

1. Study the illustration from Activity 2. Which of the named components can regulate the entry of calcium into a cell?

Knowledge Area: Life At The Molecular, Cellular And Tissue Level

1. Component C, an integral protein, can function as a channel that regulates the movement of calcium into or out of a cell.

2. As an ion, calcium is highly hydrophilic and the hydrophobic interior of the phospholipid bilayer acts as a barrier to calcium’s movement across the bilayer. Non-polar molecules are hydrophobic and can diffuse across the phospholipid bilayer via hydrophobic interactions with the phospholipid tails.

What is a plasma membrane? The plasma membrane, also known as the cell membrane, is the thin, flexible barrier that separates the cell from its environment. The plasma membrane name comes from its ability to move with the cell in a flexible manner, such as plasma flow, and its function to create a barrier or membrane to separate the cell from the environment. All cells have a cell membrane and this is one of the defining characteristics of cells.

The plasma membrane is present in all types of cells and is an outer barrier to protect the cell

Cell Membrane Structure And Function

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The most important plasma membrane function is protection. The plasma membrane creates a barrier that separates the cell from the environment. It keeps materials inside the cell that are needed, such as macromolecules and nutrients, and keeps molecules outside the cell that could be harmful, such as toxins and pathogens.

What Is The Function Of The Cell Membrane

The plasma membrane is selectively permeable, meaning that it only allows certain materials into or out of the cell. The plasma membrane allows small, non-polar molecules to diffuse directly across, such as oxygen and carbon dioxide. This is important in the lungs, where diffusion of gases across the plasma membrane of alveolar cells is essential to carry out gas exchange.

Worksheet. Cell Membrane Structure And Function

Larger molecules, such as glucose, require a transport protein to move. Even larger molecules, or molecules in large quantities, can be moved through vesicles during endocytosis, to move molecules into the cell, or exocytosis, to move molecules out of the cell.

For example, neurons use exocytosis to release neurotransmitters through the plasma membrane, which are necessary for communication with the nervous system. When neurons receive an electrical stimulus at the axon terminal, vesicles containing neurotransmitters are mobilized to the plasma membrane. Here the vesicles fuse with the plasma membrane and release their contents into the synapse. The neurotransmitters can diffuse across the synapse and activate receptors on the next neuron, allowing neurotransmission to occur.

The plasma membrane is particularly important in multicellular organisms. On the surface of the plasma membrane are marker molecules, such as proteins and carbohydrates, which inform other cells about what type of cell it is and that it belongs to the host. This is how the body is protected from destruction by the immune system. Host cells are marked as such by markers on the surface of the plasma membrane and thus avoid immune detection.

For example, the different human blood groups are caused by different expressions of carbohydrates on the surface of the plasma membrane. The specific sugar of one blood group is recognized as self by the immune system, and so the cells are left alone to do their work in the body. However, if a person were to receive blood of a different type, the immune system of the recipient would not recognize the carbohydrates on the plasma membrane of the donor cells as itself. This leads to an immune reaction to the blood, and the patient may go into shock.

Membrane Functions And Models

The plasma membrane plays an important role in cell signaling between cells. Molecules attach to receptors on the surface of the cell membrane and can trigger a host of internal changes, called a signaling cascade. This can ultimately lead to changes in transcription and the function of the cell.

For example, hormones bind to receptors embedded in the surface of the cell membrane. One type of hormone, insulin, is released into the blood in response to elevated blood sugar levels. Insulin binds to insulin receptors on the surface of cells. This sets off an intracellular signaling cascade within the cell that causes the translocation of glucose transport proteins to the cell surface. This allows the cells to take up glucose from the environment, thereby lowering blood sugar levels and maintaining homeostasis.

Other signaling molecules can make cells divide, grow or change their behavior. This in turn regulates the function of the organs, organ systems and ultimately the organism. The presence of different receptors in the plasma membrane allows the cell to detect these different stimuli in the environment.

What Is The Function Of The Cell Membrane

What is the plasma membrane made of? The plasma membrane structure is unique and this allows for its function. The plasma membrane structure is primarily made of a phospholipid bilayer. Phospholipids are amphipathic, meaning they have both hydrophilic parts, parts that love water, and hydrophobic parts, parts that hate water. The heads are hydrophilic and face both the outer environment and the internal cytoplasm. The hydrophobic tails point inside the membrane away from the aqueous environment.

Cellular Structure And Function: Video & Anatomy

There are other types of lipids in addition to phospholipids in the bilayer, such as sterols and sphingolipids. Sterols include molecules such as cholesterol that are based on a carbon ring structure. Sphingolipids are based on ceramide and have either a phosphocholine head group or a carbohydrate structure. These lipids are in smaller amounts compared to phospholipids and play an important role in cellular functions.

In addition to the phospholipid bilayer, there are also additional parts of the plasma membrane. Some of those parts include:

Proteins serve many important functions in the plasma membrane. Proteins that span the plasma membrane are called integral proteins. These proteins can be structural, helping to keep the shape of the cytoskeleton inside the cell. Proteins in the cell membrane can also help it to anchor to other cells, such as cadherin proteins. Proteins can act as pumps or channels, allowing the passage of specific molecules through the membrane. Proteins are also receptors, which respond to changes in the extracellular environment and create signaling cascades within the cell.

Membrane proteins are essential for cellular function. Even small changes to membrane proteins can have serious consequences for the cell and even the entire organism. For example, the CFTR protein is a chloride channel protein located in the plasma membrane. A single point mutation can occur in this protein causing cystic fibrosis. During this disease, the CFTR protein does not work properly and therefore does not transport chloride effectively. This in turn affects the water balance of the cell. This causes the mucus produced in the lungs to become sticky and thick, trapping bacteria and leading to breathing problems associated with the disease.

Cell Bio Chapter 4

Carbohydrates are macromolecules attached to the surface of the plasma membrane. Carbohydrates are always located on the outside of the cell, due to the reducing nature of the cytoplasm. Carbohydrates are bound to proteins as glycoproteins or to lipids as glycolipids. The main function of carbohydrates in the membrane is recognition. The carbohydrate-enhanced molecules act like name tags for the cell, allowing other cells to recognize them.

Carbohydrates are usually short chains and branched, called oligosaccharides. The highly branched and unique nature of the carbohydrates creates specific recognition sites for proteins from other cells.

Glycoproteins are created in the endoplasmic reticulum and the Golgi apparatus. Glycoproteins formed in the endoplasmic reticulum are called N-linked, because the carbohydrate chain is attached to a nitrogen atom. Glycoproteins synthesized in the Golgi apparatus are called O-linked, because the carbohydrates are attached to an oxygen atom. Glycoproteins synthesized in the endomembrane system are then transported via vesicles to the plasma membrane where they are integrated into the phospholipid bilayer. Proteoglycans are a special type of glycoprotein where a long carbohydrate chain is attached to an integral membrane protein. These long-chain carbohydrates help connect the cell to the extracellular matrix.

What Is The Function Of The Cell Membrane

Glycolipids are also synthesized in the Golgi apparatus and then transported to the membrane in vesicles. There are three main types of glycolipids: glycosphingolipids, glycoglycerolipids and glycophosphatidylinositol. Glycosphingolipids are most abundant in animal cells and play an important role in cellular functions, including cell signaling and cell proliferation.

In The Cell Membrane/plasma Membrane/phospholipid Bilayer, What Do The Peripheral And Integral Protein Do?

Cholesterol plays an important role in the regulation of membrane fluidity. Cholesterol is a small steroid lipid that fits between the hydrophobic tails of the phospholipids. The membrane becomes less fluid as the temperature drops and can become too fluid as the temperature increases. In order to increase the temperature range at which the membrane is stable, cells use cholesterol to

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