What Is The Function Of Proteins In The Cell Membrane – Proteins are the “workhorses” of the body and participate in many bodily functions. As we have already discussed, proteins come in all sizes and shapes, and each one is specially designed for its specific function. This page describes some of the important functions of proteins. As you read through them, remember that the synthesis of all these different proteins requires sufficient amounts of amino acids. As you can imagine, consuming a diet deficient in protein and essential amino acids can impair many body functions. (More on this later in the unit.)

Figure (PageIndex): Examples of proteins with different functions, sizes, and shapes. “Enzymes, Antibodies, and Hormones” from “Protein Functions”, Section 6.4 of Introduction to Nutrition (v. 1.0), licensed under CC BY-NC-SA 3.0.

What Is The Function Of Proteins In The Cell Membrane

The main types and functions of proteins are summarized in the table below, and the following sections of this page provide more detail about each.

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Digest macronutrients into smaller monomers that can be absorbed; Performs steps in metabolic pathways to allow utilization of nutrients

Table (PageIndex): Protein types and functions. “Protein Types and Functions” by Timberly Powell is licensed under CC BY-NC-SA 2.0

More than 100 different structural proteins have been discovered in the human body, but by far the most abundant is collagen, which makes up about 6 percent of the total body weight. Collagen makes up 30 percent of bone tissue and contains large amounts of cartilage, ligaments, cartilage, skin, and muscles. Collagen is a strong, fibrous protein composed mostly of the amino acids glycine and proline. In its four-dimensional structure, three strands of protein are twisted around each other like a rope, and then these collagen ropes are joined together.

This highly ordered structure is even stronger than steel fibers of the same size. Collagen makes bones strong but flexible. Collagen fibers in the dermis of the skin provide this structure, and elastin protein fibrils make it flexible. Put the skin on your hand and then leave; The collagen and elastin proteins in the skin allow it to return to its original shape. Smooth muscle cells that secrete collagen and elastin proteins surround blood vessels, providing structure and flexibility to the vessels after blood is pumped through them. Another strong, fibrous protein is keratin, an important component of skin, hair and nails.

The Structure And Function Of Proteins

Enzymes are proteins that carry out specific chemical reactions. The job of an enzyme is to prepare a site for a chemical reaction and reduce the amount of energy and time it takes for that chemical reaction to occur (this is known as “catalysis”). On average, more than 100 chemical reactions occur in cells every second, and many of them require enzymes. The liver alone has over 1,000 enzyme systems. Enzymes are unique and will only use specific substrates that fit into their active site, like the way a lock can only be opened with a special key. Fortunately, an enzyme can perform its role as a catalyst over and over again, even though it is eventually destroyed and regenerated. All bodily functions, including breaking down nutrients in the stomach and small intestine, converting nutrients into molecules the cell can use, and building all macromolecules, including protein, involve enzymes.

Figure (PageIndex): Enzymes are proteins. The enzyme’s job is to provide a site for substances to react chemically and form products, and to reduce the amount of energy and time it takes for this to happen. “Enzyme Activity” from “Protein Functions”, section 6.4 from the book Introduction to Nutrition (v. 1.0), licensed under CC BY-NC-SA 3.0.

Are chemical messengers produced by the endocrine glands. When an endocrine gland is stimulated, it releases a hormone. The hormone is then transported in the blood to its target cells, where it sends a message to initiate a specific response or cellular process. For example, when you eat food, your blood glucose level rises. In response to increased blood glucose, the pancreas releases the hormone insulin. Insulin tells the body’s cells that glucose is available and takes it from the blood and stores it or uses it to make energy or make macromolecules. A major function of hormones is to activate and deactivate enzymes, so some proteins can even regulate the actions of other proteins. While not all hormones are made of proteins, most are.

Adequate protein intake enables the body’s basic biological processes to maintain homeostasis (constant or stable conditions) in a changing environment. One aspect of this is fluid balance, maintaining the proper distribution of water in different parts of the body. If too much water suddenly moves from the blood into the tissue, the result is swelling and potentially cell death. Water always flows from an area of ​​higher concentration to an area of ​​lower concentration. As a result, water moves toward areas with higher concentrations of other solutes, such as protein and glucose. In order for water to be evenly distributed between blood and cells, proteins are constantly circulating in the blood in high concentrations. The most abundant protein in the blood is a butterfly-shaped protein known as albumin. The presence of albumin in the blood makes the protein concentration in the blood similar to that in the cells. Therefore, the fluid exchange between blood and cells is not intense, but is reduced to maintain homeostasis.

Carbohydrates, Proteins, And Fats

Figure (PageIndex): The butterfly-shaped protein, albumin, has many functions in the body including maintaining fluid and acid-base balance and transporting molecules. “Albumin” is in the public domain by Jawaharlal Swaminathan and MSD staff

Protein is also needed to maintain proper pH balance (a measure of how acidic or basic a substance is) in the blood. Blood pH is maintained between 7.35 and 7.45, which is slightly basic. Even a small change in blood pH can affect the body’s functions. The body has many systems that keep the pH of the blood within a normal range to prevent this from happening. One of these is circulating albumin. Albumin is slightly acidic, and because it is negatively charged it neutralizes many of the positively charged molecules in the blood, such as hydrogen protons (H.

), calcium, potassium and magnesium. Albumin acts as a buffer against sudden changes in the concentration of these molecules, thus maintaining blood pH balance and homeostasis. The protein hemoglobin also participates in acid-base balance by binding hydrogen protons.

Protein also plays an important role in transporting substances around the body. For example, albumin binds chemically to hormones, fatty acids, certain vitamins, essential minerals, and drugs, and transports them throughout the circulatory system. Each red blood cell contains millions of hemoglobin molecules that bind oxygen in the lungs and carry it to all the tissues of the body. The plasma membrane of the cell is usually impermeable to large polar molecules, so in order for the necessary nutrients and molecules to reach the cell, many transport proteins are present in the cell membrane. Some of these proteins are channels that allow specific molecules to move in and out of cells. Others act as one-way taxis and require energy to function.

Nanoscale ‘computer’ Controls Function Of Protein, Influences Cell Behavior

Figure (PageIndex): Molecules move in and out of cells through transport proteins that are either channels or carriers. “Protein Carriers in Cell Membranes” by Lydif Hats, Mariana Ruiz Villarreal is in the public domain

Video (PageIndex): “The Sodium-Potassium Pump” by RicochetScience, YouTube (May 23, 2016), 2:26 min. This lesson explains how the sodium-potassium pump uses active transport to move sodium ions (Na+) out of the cell and potassium ions (K+) into the cell.

Protein also plays an important role in the body’s immune system. The strong collagen fibers in the skin provide it with structure and support, but it also acts as a barrier against harmful substances. The immune system’s attack and destruction functions depend on enzymes and antibodies, which are also proteins. For example, an enzyme called lysozyme is secreted in saliva and attacks the walls of bacteria, causing them to disintegrate. Certain proteins circulating in the blood can be directed to form molecular knives that pierce the cell membrane of foreign invaders. Antibodies secreted by white blood cells survey the entire circulatory system, looking for harmful bacteria and viruses to surround and destroy. Antibodies also trigger other factors in the immune system to seek out and destroy unwanted intruders.

Video (PageIndex): “Specific Immunity, Antibodies,” by Corp. Noctum, YouTube (Dec. 11, 2007), 1 min. Watch this video to see how antibodies protect against foreign invaders.

Cell Membrane Function And Structure

Some amino acids in proteins can be broken down and used to make energy. Only about 10 percent of dietary protein is used to generate cellular energy each day. The liver is capable of breaking down amino acids into carbon skeletons, which can then be fed into the citric acid or Krebs cycle. This is similar to the way glucose is used to make ATP. If a person’s diet does not contain enough carbohydrates and fats, the body will use more amino acids to create energy, which can compromise the synthesis of new proteins and break down muscle proteins if calories are insufficient. There is also consumption.

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