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Proteins
Chapter 6 of Human Nutrition
| Term | Definition |
|---|---|
| proteins | Large molecules, made up of chains of amino acids, found in all living cells. |
| amino acids | Fundamental units of proteins; composed of carbon, hydrogen, oxygen, and nitrogen. |
| amine group | Nitrogen-containing compound (NH2) connected to the central carbon of an amino acid. |
| side chain | Part of an amino acid that provides its unique qualities; also referred to as the R group. |
| peptide | Chain of amino acids. |
| dipeptide | Chain of two amino acids joined together by a peptide bond. |
| tripeptide | Chain of three amino acids joined together by peptide bonds. |
| polypeptide | Chain consisting of 10 or more amino acids joined together by peptide bonds. |
| peptide bonds | Bonds that connect amino acids; created when the acid group of one amino acid is joined with the amine group of another through condensation. |
| essential amino acids | Nine amino acids that the body cannot synthesize; they must be obtained through dietary sources. |
| nonessential amino acids | Eleven amino acids the body can synthesize and that therefore do not need to be consumed in the diet. |
| conditionally essential amino acids | Nonessential amino acids that become essential (and must be consumed in the diet) when the body cannot make them. |
| primary structure | First stage of protein synthesis after transcription when the amino acids have been linked together with peptides bonds to form a simple linear chain. |
| secondary structure | Shape of a protein in which hydrogen bonding between carboxyl and amine groups has caused the straight chain to fold and twist. |
| tertiary structure | Protein structure that occurs when the side chains of the amino acids, most often containing sulfur, form bonds resulting in loops, bends, and folds in the molecule. |
| quaternary structure | Rod-like or globular structure of a protein formed when two or more polypeptide chains cluster together. |
| denature | To alter a protein's secondary, tertiary, or quaternary structure, thereby disabling its function; the amino acids of the primary structure remain linked together by peptide bonds. |
| amino acid pools | Limited supplies of amino acids that accumulate in the blood and cells; amino acids are pulled from the pools and used to build new proteins. |
| protein turnover | Continual process of degrading and synthesizing protein. |
| genes | A segment of DNA that codes for a protein; genes are inherited from our parents and determine a variety of characteristics. |
| ribosomes | Organelles found in the cytoplasm that read the mRNA and build the protein in the proper sequence during elongation. |
| transcription | First stage in protein synthesis, in which the DNA sequence is copied from the gene and transferred to messenger RNA. |
| messenger RNA (mRNA) | Type of RNA that copies the genetic information from the DNA and carries it from the nucleus to the ribosomes in the cell. |
| translation | Second phase of protein synthesis; the process of converting the information in mRNA to an amino acid sequence in the ribosomes. |
| transfer RNA (tRNA) | Type of RNA that transfers a specific amino acid to a growing polypeptide chain in the ribosomes during protein synthesis. |
| elongation | Phase of protein synthesis in which the polypeptide chain grows longer by adding amino acids. |
| sickle cell anemia | Blood disorder caused by a genetic defect that results in the synthesis of hemoglobin S, which makes the red blood cells likely to distort into a sickle shape. |
| deamination | Removal of the amine group from an amino acid. |
| urea | Nitrogen-containing waste product of protein metabolism that is mainly excreted through the urine via the kidneys. |
| transamination | Transfer of an amino group from one amino acid to a keto acid to form a new nonessential amino acid. |
| catabolic | Energy-releasing process that breaks larger molecules into smaller parts. |
| anabolic | Energy-requiring process in which smaller molecules are combined to form larger molecules. |
| albumin | Protein produced in the liver and found in the blood that helps maintain fluid balance. |
| edema | Accumulation of excess water in the spaces surrounding the cells, which causes swelling of the body tissue. |
| acidosis | Condition in which the blood pH is too low, generally due to excessive hydrogen ions. |
| alkalosis | Condition in which the blood pH is too low due to a low concentration of hydrogen ions. |
| buffers | Substances that help maintain the proper pH in a solution by accepting or donating hydrogen ions. |
| transport proteins | Proteins that carry other substances, mainly nutrients, through the blood to various organs and tissues. Proteins can also act as channels through which some substances enter your cells. |
| antibodies | Proteins that identify and participate in the destruction of pathogens as part of the body's immune response. |
| immunity | State of having built up memory immune cells that target a particular pathogen so that any subsequent encounter with that pathogen prompts rapid production of specific antibodies. |
| allergen | Substance, such as wheat protein, that causes an allergic reaction. |
| glucogenic amino acids | Amino acids that can be used to form glucose through gluconeogenesis. |
| nitrogen balance | Difference between nitrogen intake and nitrogen excretion. |
| amino acid score | Composition of essential amino acids in a protein compared with a standard, usually egg protein. |
| limiting amino acid | Essential amino acid that is in the shortest supply, relative to the body's needs, in an incomplete protein |
| protein digestibility corrected amino acid score (PDCAAS) | Score measured as a percentage that takes into account both digestibility and amino acid score and provides a good indication of the quality of a protein. |
| complete protein | Protein that provides all the essential amino acids, along with some nonessential amino acids. Soy protein and protein from animal sources are complete proteins. |
| incomplete protein | Protein that is low in one or more of the essential amino acids. Proteins from plant sources tend to be incomplete. |
| isoflavones | Naturally occurring phytoestrogens, or weak plant estrogens, that function in a similar fashion to the hormone estrogen in the human body. |
| protein-energy malnutrition (PEM) | Lack of sufficient dietary protein and/or kilocalories. |
| kwashiorkor | State of PEM in which there is a severe deficiency of dietary protein. |
| marasmus | State of PEM in which there is a severe deficiency of kilocalories, which perpetuates wasting; also called starvation. |
| vegetarian | Person who avoids eating animal foods. Some vegetarians only avoid meat, fish, and poultry, while others (vegans) avoid all animal products, including eggs and dairy. |
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bsauveur
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