What makes proteins different from one another

In people with celiac disease, an autoimmune reaction can occur from exposure to the protein called gluten, found in wheat, rye and barley. Aglaee Jacob is a registered dietitian. She has experience working with people who have diabetes, cardiovascular disease, hypertension and obesity issues. Jacob obtained a bachelor of science and a master of science, both in nutrition, from Laval University in Quebec City, Canada. Healthy Eating Nutrition Protein.

By Aglaee Jacob. Related Articles. Amino Acids Proteins are made of amino acids. Animal Protein Animal proteins differ from vegetarian sources of protein because they are complete and have a better balance of the different essential amino acids. The information on this site should not be used as a substitute for professional medical care or advice.

Contact a health care provider if you have questions about your health. What are proteins and what do they do? From Genetics Home Reference. Proteins can be described according to their large range of functions in the body, listed in alphabetical order: Examples of protein functions Function Description Example Antibody Antibodies bind to specific foreign particles, such as viruses and bacteria, to help protect the body.

Immunoglobulin G IgG Enzyme Enzymes carry out almost all of the thousands of chemical reactions that take place in cells. Phenylalanine hydroxylase Messenger Messenger proteins, such as some types of hormones, transmit signals to coordinate biological processes between different cells, tissues, and organs.

Growth hormone Structural component These proteins provide structure and support for cells. Topics in the How Genes Work chapter What are proteins and what do they do? How do genes direct the production of proteins? Can genes be turned on and off in cells? As proteins fold, they test a variety of conformations before reaching their final form, which is unique and compact. Folded proteins are stabilized by thousands of noncovalent bonds between amino acids. In addition, chemical forces between a protein and its immediate environment contribute to protein shape and stability.

For example, the proteins that are dissolved in the cell cytoplasm have hydrophilic water-loving chemical groups on their surfaces, whereas their hydrophobic water-averse elements tend to be tucked inside. In contrast, the proteins that are inserted into the cell membranes display some hydrophobic chemical groups on their surface, specifically in those regions where the protein surface is exposed to membrane lipids.

It is important to note, however, that fully folded proteins are not frozen into shape. Rather, the atoms within these proteins remain capable of making small movements.

Even though proteins are considered macromolecules, they are too small to visualize, even with a microscope. So, scientists must use indirect methods to figure out what they look like and how they are folded. The most common method used to study protein structures is X-ray crystallography. With this method, solid crystals of purified protein are placed in an X-ray beam, and the pattern of deflected X rays is used to predict the positions of the thousands of atoms within the protein crystal.

In theory, once their constituent amino acids are strung together, proteins attain their final shapes without any energy input.

In reality, however, the cytoplasm is a crowded place, filled with many other macromolecules capable of interacting with a partially folded protein. Inappropriate associations with nearby proteins can interfere with proper folding and cause large aggregates of proteins to form in cells.

Cells therefore rely on so-called chaperone proteins to prevent these inappropriate associations with unintended folding partners. Chaperone proteins surround a protein during the folding process, sequestering the protein until folding is complete.

For example, in bacteria, multiple molecules of the chaperone GroEL form a hollow chamber around proteins that are in the process of folding. Molecules of a second chaperone, GroES, then form a lid over the chamber.

Eukaryotes use different families of chaperone proteins, although they function in similar ways. Chaperone proteins are abundant in cells.

These chaperones use energy from ATP to bind and release polypeptides as they go through the folding process. Chaperones also assist in the refolding of proteins in cells. Folded proteins are actually fragile structures, which can easily denature, or unfold. Although many thousands of bonds hold proteins together, most of the bonds are noncovalent and fairly weak. Even under normal circumstances, a portion of all cellular proteins are unfolded. Increasing body temperature by only a few degrees can significantly increase the rate of unfolding.

When this happens, repairing existing proteins using chaperones is much more efficient than synthesizing new ones. Interestingly, cells synthesize additional chaperone proteins in response to "heat shock. All proteins bind to other molecules in order to complete their tasks, and the precise function of a protein depends on the way its exposed surfaces interact with those molecules.

Proteins with related shapes tend to interact with certain molecules in similar ways, and these proteins are therefore considered a protein family. The proteins within a particular family tend to perform similar functions within the cell. Proteins from the same family also often have long stretches of similar amino acid sequences within their primary structure.

These stretches have been conserved through evolution and are vital to the catalytic function of the protein. For example, cell receptor proteins contain different amino acid sequences at their binding sites, which receive chemical signals from outside the cell, but they are more similar in amino acid sequences that interact with common intracellular signaling proteins. Protein families may have many members, and they likely evolved from ancient gene duplications.

These duplications led to modifications of protein functions and expanded the functional repertoire of organisms over time.