Glossary of general medical terms
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This glossary provides pronunciations and easy-to-understand definitions for terms commonly used in basic biomedical research.
The region on an enzyme's surface where only a specific substrate can bind, resulting in a chemical reaction.
The study of how the body absorbs, distributes, breaks down (metabolizes), and eliminates drugs. Sometimes, T is included for transports.
(AG-uh-nist) A molecule that binds to a receptor in a cell to trigger a response, such as muscle contraction or hormone release.
(uh-MEE-no) A chemical building block of proteins. There are 20 standard amino acids, each of which has the same basic structure with a different side chain. The side chain gives the amino acid its unique properties.
(an-l-JEE-zik) An agent or drug that reduces pain without affecting consciousness.
(an-uhs-THEE-zhuh) Medical treatment with a drug, called an anesthetic, that prevents patients from feeling pain during surgery. General anesthesia affects the whole body, making patients unconscious and unable to move. Local and regional anesthesia numbs just a small or large part of the body, respectively, without affecting consciousness
(an-uhs-thee-zee-OL-uh-jee) The medical field related to using anesthetic drugs to prevent patients from feeling pain during surgery. Doctors in this field, called anesthesiologists, carefully monitor patients throughout surgery and during recovery
(an-TAG-uh-nist) A molecule that binds to a receptor in a cell to prevent a response, such as a muscle contraction or hormone release. For example, some medicines to treat opioid addiction bind to opioid receptors, blocking heroin or other opioids from activating them
A medicine that can kill bacteria or keep them from growing.
When bacteria change in ways that make antibiotic medicines ineffective.
A protein the immune system produces in response to a foreign substance such as a virus or bacterium.
A drug that reduces inflammation.
(an-tee-OCK-si-duhnt) A natural or man-made substance that may prevent or delay some types of cell damage. The body and many foods, including fruits and vegetables, naturally produce antioxidants
(ap-uhp-TOH-sis) A process in which cells in the body die in a controlled and predictable way because they have DNA damage or are not needed. The other type of cell death is necrosis.
A fundamental unit of matter, the substance a physical object is composed of, consisting of a nucleus and electrons.
(ah-DEH-no-seen try-FOSS-fate)The major source of energy for biochemical reactions in all organisms. ATP is formed when animals digest food or plants undergo photosynthesis. Energy is released when certain chemical bonds in ATP are broken.
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(bak-TEER-ee-uhm) (plural: bacteria) A one-celled microorganism without a nucleus. Bacteria live almost everywhere in the environment. Some bacteria may infect humans, plants, or animals. They may be harmless, or they may cause disease. Scientists often use bacteria as research organisms to study basic biological processes
How quickly and to what extent the active part of a drug is absorbed by the body and is available at the site where it’s needed.
The scientific study of the chemistry of living cells, tissues, organs, and organisms.
Capable of being broken down physically and/or chemically by microorganisms.
A highly organized community of microorganisms that develops naturally on certain surfaces. Biofilms can be helpful in treatment of wastewater, for example. But they can also be harmful, like when they form on medical devices implanted in people. These biofilms are highly resistant to antibiotic medicines
A field of research that relies on computers to store and analyze large amounts of biological data.
An organism’s innate timing device. Composed of proteins that interact in cells throughout the body, these clocks produce circadianrhythms and regulate their timing.
A natural or synthetic material introduced into living tissue, often as part of a medical device such as an artificial joint
A system or device that converts a biological response into an electrical signal. For example, in a blood glucose monitor, a test strip contains an enzyme that reacts to glucose in the blood, creating an electrical signal that indicates the amount of glucose in the blood. People use biosensors in many fields, including food processing, medicine, and defense
The use of living organisms or biological systems to make useful products and processes.
(bla-STEE-muh) A specialized bud of cells that rapidly divide to form skin, scales, muscle, bone, or cartilage needed to create a lost limb, fin, or tail in animals such as lobsters, catfish, and lizards.
Tissue damage caused by heat, chemicals, electricity, sunlight, or nuclear radiation. Burns are defined by how deep they are and how large an area they cover. Types of burns include:
First degree: Damage only to the outer layer of skin (epidermis)
Second degree: Damage to the outer layer and the layer beneath it (dermis)
Third degree: Damage or complete destruction of both layers of skin
Fourth degree: Extends into fat
Fifth degree: Extends into muscle
Sixth degree: Extends to bone
(kahr-SIN-uh-jen)Any substance that causes cancer.
(KAT-uh-list) A substance that speeds up a chemical reaction that would have occurred without help, but at a much slower rate.Enzymes are biological catalysts
The basic subunit of any living organism; the simplest form of life. Cells house the biological machinery that makes the proteins, chemicals, and signals responsible for everything that happens inside the body.
The steps of a cell copying its contents and dividing in two.
Prophase (PRO-faze): Chromosomes condense and become visible and the spindle forms. The spindle is a football-shaped array of fibers made of microtubules and associated proteins. Some of the fibers attach to the chromosomes and help draw them to opposite ends of the cell.
Prometaphase (pro-MET-uh-faze): The nuclear membrane breaks apart, and the spindle starts to interact with chromosomes.
Metaphase (MET-uh-faze): Copied chromosomes align in the middle of the spindle.
Anaphase (ANN-uh-faze): Chromosomes separate into two genetically identical groups and move to opposite ends of the spindle.
Telophase (TEE-lo-faze): Nuclear membranes form around each of the two sets of chromosomes, the chromosomes begin to spread out, and the spindle begins to break down.
Cytokinesis (SY-toh-kin-EE-sis): The cell splits into two daughter cells.
Interphase (IN-tur-faze) is the period in a cell's life cycle when it is not undergoing cell division. There are several checkpoints where the cycle can pause if there’s a problem, such as incomplete DNA synthesis or damaged DNA
The brain and spinal cord, which control all the workings of the body.
A hollow or pore-containing protein that spans a cell membrane and allows small molecules, such as charged particles (ions), to move from one side of the membrane to the other.
A protein that helps other proteins fold or move throughout the cell.
A field that blends chemistry and biology and involves the application of chemical techniques and tools to the study of biological systems.
A physical force holding atoms together to form a molecule.
Covalent bonds form when electrons travel between the atoms' nuclei and are thus “shared.” Molecules can contain single, double, and triple covalent bonds.
Peptide bonds are specific covalent bonds formed by joining two amino acids.
Ionic bonds are forces that hold together two ions.
Metallic bonds are forces that hold atoms together in a metallic substance where electrons continually move from one atom to another and are not associated with any specific pair of atoms.
A collection of chemicals that are stored along with related information, such as the chemical structure, purity, quantity, and other characteristics of the substance.
The use of computer and information technologies to study problems in chemistry
A field of study concerned with the composition, properties, and reactions of substances.
(kee-moh-TAK-sis) The movement of a cell toward or away from a chemical force
A waxy lipid produced by animal cells that is a major component of cell membranes and a building block for some hormones. Cholesterol is also found in foods from animal sources. Good cholesterol carries cholesterol from other parts of your body back to your liver where it can be removed. Bad cholesterol can build up in the arteries, causing them to narrow or become blocked.
(KROH-muh-tin)The part of the nucleus that consists of DNA and proteins and forms chromosomes
(KROH-muh-sohm) A cellular structure in the nucleus containing genes. Chromosomes are composed of DNA and proteins, and they split into two identical strands, called chromatids, during cell division. Humans have 23 pairs of chromosomes in every cell in their bodies. One of each pair is from the mother and the other is from the father.
(SIL-ee-uhm) (plural: cilia) A hairlike projection from a cell surface. The rhythmic beating of cilia can move fluid or mucus over a cell or can allow single-celled organisms to move. Cilia are shorter than flagella.
(sur-KAY-dee-uhn) Pertaining to a period of about 24 hours; applied especially to rhythmic biological repetition like the sleep-wake cycle and the release of some hormones, called circadian rhythms
A scientific study of an intervention in people. The intervention can be a medication, medical device, procedure, or change in behavior. The goal is to find out if the intervention is safe and effective.
In genetics, the process of making many identical copies of a gene or a whole organism. The term also refers to the isolation and manipulation of a gene
A helper molecule (either inorganic, such as a metal ion, or organic, such as a vitamin) an enzyme needs to work
The random assembly of various chemical units into chemical libraries of new synthetic compounds.
(juh-NOH-miks) The study of human genetics by comparisons with other organisms' genetics.
(kuhm-PEN-suh-tawr-ee hahy-PUR-truh-fee) In humans and some other animals, when part of an organ is removed or destroyed, the remaining portion grows to allow the organ to function as it did before. The liver can regrow to its original size. A kidney, pancreas, thyroid, adrenal gland, or lung can undergo the same process, but in a more limited way. This is one type of regeneration.
A field of science that uses computers to study complex biological processes that involve many molecular interactions.
An immune system in bacteria that recognizes and destroys invading DNA and maybe RNA. It’s been adapted into a gene-editing tool widely used in basic and applied research.
A process that occurs during meiosis, in which chromosome partners, one inherited from each parent, physically swap sections with one another. This creates hybrid chromosomes that are a patchwork of the original pair. Crossing over occurs in species that reproduce sexually and increases the genetic variety of offspring
A type of transmission electron microscopy (TEM) where scientists freeze a biological sample so quickly that water molecules don’t have time to form ice crystals. This keeps cellular materials in their normal place. Cold samples are more stable and can be imaged many times
(sahy-KLOH-sis) Movement of nutrients and organelles within cells to carry out various cellular functions. The cytoplasm within the cell creates a directional flow that pushes around the content of the cells
(SAHY-tuh-PLAZ-uhm) The material found between the cell membrane and the nuclear envelope. It includes the cytosol and allorganelles except the nucleus
(SAHY-toh-SKEL-uh-tuhn) A collection of fibers that gives a cell shape and support and allows movement within the cell and, in some cases, by the entire cell. The three main types of cytoskeletal fibers are actin filaments, intermediate filaments, and microtubules.
Actin filaments (AK-tin FIL-uh-muhnt) Fibers that contract or lengthen to give cells the flexibility to move and change shape. Together with the protein myosin, actin filaments are responsible for muscle contraction.
Intermediate filaments Fibers that provide strength in things like nails, hair, the outer layer of skin, nerves, and certain organs.
Microtubules (MY-kroh-TOO-byool) Strong, hollow fibers that act as a structural support for the cell. During cell division, microtubules form the spindle that directs chromosomes to the daughter cells. Microtubules also serve as tracks for transportingvesicles and give structure to flagella and cilia.
(SAHY-tuh-sol) The semi-fluid portion of the cytoplasm, excluding the organelles. The cytosol is a concentrated solution of proteins, salts, and other molecules.
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(dif-uh-ren-shee-AY-shuhn) When an unspecialized cell becomes a specialized cell with a specific function. During development, embryonic stem cells differentiate into the many cell types that make up the human body. Adult stem cells differentiate into the type oftissue in which they are located to replace cells lost to age, disease, or injury.
(DIP-loyd) A cell or organism that has paired chromosomes, one from each parent.
Using a network of hundreds or thousands of computers to perform complex calculations that usually can’t be done on a single computer. For example, researchers have used distributed computing to study the dynamics of how proteins fold.
(dee-AWK-see-RAHY-boh-noo-CLAY-ik) The substance of heredity. A long, usually double-stranded chain of nucleotides that carries the information needed for all cellular functions, including protein production.
(POL-uh-muh-rays) An enzyme that copies, and sometimes repairs, DNA.
(SEE-kwuhn-sing) Sometimes called gene or genome sequencing, a lab technique used to find the exact order of the bases in a DNAmolecule. The DNA sequence carries information a cell needs to make proteins and RNA molecules
The way a health care provider gives medicine to a person or animal. Drugs can be given by mouth (oral); through the skin (topical), mucous membranes (nasal), or lungs (inhaled); or into a vein through a needle (intravenous)
(ih-DEE-muh) Swelling caused by fluid in the body's tissues. It usually occurs in the feet, ankles, and legs, but it can involve the entire body.
(ih-LEK-truh-lahyt) A mineral in the body that has an electric charge. Electrolytes help balance the amount of water in the body and the pH (acid/base) level; move nutrients into and wastes out of cells and make sure nerves, muscles, the heart, and the brain work the way they should. Electrolytes include sodium, calcium, potassium, chlorine, phosphate, and magnesium.
(ih-LEK-troh-mag-NET-ik ray-dee-AY-shuhn) Energy produced in the form of a wave. It includes all kinds of radiation, including, in order of increasing energy: radio waves, microwaves, infrared radiation (heat), visible light, ultraviolet radiation (the part of sunlight that causes sunburn), X-rays, and gamma radiation (made by nuclear reactions)
A very small particle that has a negative charge of electricity and travels around the nucleus of an atom.
A technique that uses beams of fast-moving electrons instead of light to magnify samples. Powerful magnets focus the electrons into an image.
A pure substance that can't be chemically separated into simpler substances. Carbon, hydrogen, and oxygen are fundamental elements in biology.
(en-doh-sahy-TOH-sis) A process cells use to absorb nutrients, fluids, proteins, and other molecules. The cell membrane curves inward, encircling the material, then pinches off, producing a vesicle inside the cell.
(EN-doh-plaz-mik reh-TIK-yuh-luhm) An organelle made up of interconnected tubes and flattened sacs. There are two kinds of ER: rough ER, which adds sugars to proteins after they're without being used up recreated by ribosomes, and smooth ER, which helps make lipids and neutralizes toxins.
(EN-zahym) A biological catalyst that is almost always a protein and speeds up the rate of a specific chemical reaction in the cell
(ep-ih-juh-NET-iks) The study of changes in gene expression or phenotypes that are not the result of changes in DNA sequence
(yoo-KAYR-ee-ah-tik) A cell with a membrane-bound nucleus and other organelles not found in prokaryotic cells. Eukaryotic cells make up animals, plants, fungi, and some single-celled organisms
(ek-soh-sahy-TOH-sis) A process cells use to dump wastes outside of the cell via vesicles
(ek-struh-SEL-yuh-ler MEY-triks) The material around, within, and between the body's organs, tissues, and cells. In some tissues, it's a thin layer separating cells. In others, it's the major component. The extracellular matrix is most prevalent in connective tissue, the material that forms our skeletons, cushions our internal organs, and winds between blood vessels and around nerves.
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(fluh-JEL-uhm) (plural: flagella) A long, tail-like structure extending from a cell. Sperm and many microorganisms move using flagella
(floh-RES-uhns) Giving off light at one wavelength (emission) after absorbing light of a different wavelength (excitation). Researchers use fluorescent dyes to take images of cells.
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A protein located on the inside of the cell membrane that helps transmit signals from hormones into cells
A unit of heredity; a segment of DNA that contains the code for making a specific protein or RNA molecule.
When the information in a gene directs the building of a protein. The cell reads the gene in groups of three nucleotides. Each of these groups corresponds to one of 20 different amino acids used to build the protein
The instructions in a gene that tell the cell how to make a specific protein
The manipulation of an organism's genes—introducing, eliminating, or changing them—using modern molecular biology techniques
The scientific study of genes and heredity—of how certain qualities or traits are passed from parents to offspring as a result of changes in DNA sequence
(JEE-nohm) All of an organism's genetic material
(jee-NOHM-iks) The study of all of an organism's genetic material.
(glahy-koh-LIP-id) A lipid bound to a sugar.
(glahy-koh-PROH-teen) A protein bound to a sugar
(glahy-koh-SAHY-uhns) A branch of chemistry dedicated to the study of the many types of carbohydrate molecules.
(glahy-kah-sih-LAY-shun) The process of adding specialized chains of sugar molecules to proteins or lipids; occurs in the endoplasmic reticulum and Golgi.
(GAWL-jee) Also called the Golgi apparatus or Golgi complex; an organelle composed of membranous sacs in which many newly made proteins mature and become functional
(HAP-loid) A cell with one copy of each chromosome, as in a sperm or egg.
(HIS-tohn) A type of protein found in chromosomes; DNA wraps around histones
A chemical messenger that affects processes in the body such as growth and development, turning food into energy, sexual function and reproduction, and mood. Hormones are made in one part of the body and travel through the bloodstream to tissues and organs. Examples include insulin, estrogen, and testosterone.
(HAHY-druh-kahr-buhn) An organicmolecule consisting of hydrogen and carbon atoms only
A network of cells, tissues, and organs that work together to protect the body from infection.
(im-yoo-noh-THAYR-uh-pee) A medical treatment to stimulate or suppress a patient's immune system to help the body fight disease. Health care providers can use immunotherapy to treat patients with cancer or after an organ transplant, among other uses.
When a gene may be expressed differently in an offspring depending on whether it was inherited from the father or the mother
The body's response to infection or injury, causing redness, swelling, heat, and pain.
A molecule that "inhibits," or blocks, the biological action of another molecule
A substance not derived from a living organism and/or not composed of carbon and hydrogen. Opposite of organic
An electrically charged atom.
(AHY-suh-tohp) A form of a chemical element that contains the same number of protons but a different number of neutrons than other forms of the element. Researchers often use isotopes to trace atoms or molecules in a metabolic pathway
Any of a diverse group of organic compounds that don't dissolve in water. Lipids include fats, oils, hormones, and certain parts of cellmembranes
(LAHY-puh-sohm) An oily, microscopic capsule designed to package and deliver biological cargo, such as drugs, to cells in the body
(LAHY-suh-sohm) A bubblelike organelle that contains powerful enzymes that break apart biological materials into nutrients and building blocks. Lysosomes also break apart waste and transport the waste to the outside of the cell
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(spek-TROM-ih-tree) An analytical technique used to determine the composition and abundance of the atoms in a molecular substance. Typical applications include dating of geologic samples; analysis of inorganic and organic chemicals, especially for small amounts of impurities; and determining the structural formula of complex organic substances
An area of study involved with designing and making medicines for use in humans and animals.
(mahy-OH-sis) The type of cell division that makes egg and sperm cells. Meiosis generates cells that are genetically different from one another and contain half the total number of chromosomes in the parent cell. The other type of cell division is mitosis.
A semi-fluid layer of lipids and proteins. Membranes enclose cells and organelles and control passage of materials into and out of them.
(met-uh-BOL-ik) A linked series of chemical reactions occurring within a cell that build up or break down organic molecules, making or using energy in the process, called metabolism
A technology used to study the expression of many genes at once. A scientist places thousands of gene sequences in known locations on a glass slide called a gene chip. A sample containing DNA or RNA is placed in contact with the gene chip. Light is produced to show genes expressed in the sample
(mahy-kroh-BAHY-ohm) The genomes of the bacteria, fungi, and viruses found in a living organism
An organism that can be seen only with the aid of a microscope and is usually just a single cell.
A short piece of RNA that binds to messenger RNA, blocking its ability to make proteins.
(mahy-tuh-KON-dree-uhn) (plural: mitochondria) The cell's power plant; the organelle that converts food and oxygen into energy to fuel the cell. Mitochondria contain their own small genomes and appear to have descended from free-living bacteria.
(mahy-TOH-sis) The type of cell division that eukaryotic cells use to make new body cells. Mitosis results in two daughter cells that are genetically identical to the parent cell. The other type of cell division is meiosis.
A small group of research organisms that help us understand the biology of humans. Examples include yeast, fruit flies, worms, zebrafish, and mice
The molecule researchers design a drug to bind to, producing therapeutic effects. These molecules are called receptors, and the drug can be an agonist that activates the receptor or an antagonist that blocks the receptor
The smallest unit of matter that retains all of the physical and chemical properties of that substance. It consists of one or more identical atoms or a group of different atoms bonded together. For example, a water molecule contains two hydrogen atoms and one oxygen atom.
(myoo-TAY-shuhn) A change in a DNA sequence. Mutations can be caused by mistakes during cell division, exposure to some types of radiation or chemicals, or viral infections. Mutations in egg or sperm cells can be passed on to offspring, while mutations in body cells aren't passed on
(MAHY-uh-lin) A fatty covering that protects nerve fibers and makes nerve signals move quickly through the nervous system
(NAN-uh-tek-nol-uh-jee) Study of the control of matter on an atomic and molecular scale. A nanometer is one-billionth of a meter, or about the circumference of a marble in comparison to that of the Earth. Researchers can use nanotechnology across many fields of science, such as chemistry, biology, physics, and materials science
A molecule produced by a living organism—a plant, marine organism, or microorganism—that often has a medicinal use.
(neh-KROH-sis) Cell death caused by trauma or infection. The other type of cell death is called apoptosis
A cell in the nervous system that carries information through electrical impulses and chemical messengers. Also called a neuron.
(nyoor-oh-TRANS-mit-ur) A chemical messenger that passes signals between nerve cells or between a nerve cell and another type of cell
Non-steroidal anti-inflammatory drug, such as aspirin or ibuprofen, that reduces pain and inflammation.
(NOO-klee-ur) A barrier that encloses the nucleus of a cell and controls the passage of molecules between the nucleus and cytoplasm. For example, RNA molecules made in the nucleus need to be passed into the cytoplasm for protein synthesis
(NOO-klee-ur mag-NET-ik REZ-uh-nuhns spek-TROS-kuh-pee) A technique used to determine the detailed, three-dimensional structure of molecules and, more broadly, to study the physical, chemical, and biological properties of matter. It uses a strong magnet that interacts with the natural magnetic properties in atomicnuclei
(NOO-klee-uh-tahyd) A building block of DNA or RNA. It includes one base, one phosphate molecule, and one sugar molecule (deoxyribose in DNA, ribose in RNA). Thousands of nucleotides bind together to form a molecule of DNA or RNA
(NOO-klee-uhs) (plural: nuclei) Biology: The membrane-bound structure within a eukaryotic cell that contains most of the cell's geneticmaterial. Chemistry: the positively charged core of an atom, consisting of protons and neutrons
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(OH-uh-sahyt) The developing female reproductive cell; an immature egg
A group of cells and tissues that perform a specific job, including the heart, brain, kidneys, liver, and lung.
(Ohr-guh-NEL) A specialized, membrane-bound structure that has a defined function in the cell. Organelles include the nucleus,mitochondria, Golgi, endoplasmic reticulum (ER), and lysosomes
Carbon-containing compounds that are the basis for all living organisms. Opposite of inorganic.
An individual animal, plant, or single-celled life form.
(PEP-tahyd) A molecule consisting of a chain of amino acids; a small protein fragment
(puh-RIF-ur-uhl) The part of the nervous system outside of the brain and spine
(fahr-muh-koh-dahy-NAM-iks) The study of how drugs act at target sites, called receptors, on organs and tissues in the body
(fahr-muh-koh-juh-NET-iks) The study of how people's genes affect their bodies’ responses to medicines, often one gene at a time
(fahr-muh-koh-jee-NOHM-iks) The study of how people's genes affect their bodies’ responses to medicines, often encompassing the entire genome
(fahr-muh-koh-kih-NET-iks) The study of the level of a drug and its breakdown products in the blood over time
(fahr-muh-KOL-uh-jee) The study of how molecules from outside the body interact with organ systems, for example in cell signaling and communications
(fos-foh-LIP-id) A type of lipid molecule made up of two fatty acids, a phosphate group (phosphorous and oxygen), and glycerol (a type of alcohol). Fatty acids are long chains containing mostly hydrogen and carbon. The phosphate “head” of a phospholipid attracts water while the fatty acid chains repel water, so the molecules line up in a double layer with phosphate groups on the outside and fatty acids on the inside to form membranes
A natural process where green plants, algae, and some bacteria use the sun's energy to make carbohydrates from carbon dioxide and water. The carbohydrates are then broken down to produce energy, allowing the plant to grow.
A serious injury to the body, such as the following:
Blunt-force trauma: When an object or force strikes the body, often causing concussions, deep cuts, or broken bones
Penetrating trauma: When an object pierces the skin or body, usually creating an open wound
Surgery can also cause physical trauma, sometimes called a controlled injury.
(fiz-ee-OL-uh-jee) The study of how living organisms function
A double layer of phospholipids with embedded proteins that separates the contents of a cell from its outside environment.
(POL-uh-mur) A large molecule formed by combining small molecules in a simple repeating pattern
An emerging approach for disease prevention and treatment that takes into account individual differences in lifestyle, environment, and biology.
(proh-KAYR-ee-oh-tik) A cell that lacks a nucleus, such as a bacterium
(PRO-tee-uh-zohm) A cellular machine that breaks down proteins that are no longer needed and recycles or removes the resultingmolecules
A large, biological molecules composed of amino acids. Proteins are essential for all life processes. They are arranged in a specific order determined by the genetic code and folded into a specific three-dimensional shape with well-defined structures. Protein structures include alpha helixes, short, spiral-shaped sections, and beta sheets, pleated sections.
The process the body uses to create proteins from amino acids in the cell’s ribosomes.
Transcription: The first step, in which the information coded in DNA is copied (transcribed) into mRNA
Translation: The second step, in which the information encoded in mRNA is used to build the right sequence of amino acids.
(proh-tee-OM-iks) The systematic, large-scale study of all proteins in an organism
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A protein found on the cell surface to which a signal molecule attaches. This leads to a cascade of reactions involving several other molecules inside the cell. Specific signal molecules bind to specific receptors, fitting together like a key in a lock. Many medicines target receptor proteins, either triggering a response (agonist) or preventing a response (antagonist).
(ree-KOM-buh-nuhnt) Hybrid DNA produced in the lab by joining pieces of DNA from different sources
A natural process that allows plants and animals to replace or restore damaged or missing cells, tissues, organs, and even entire body parts to full function. Compensatory hypertrophy is a type of regeneration.
(rep-li-KAY-shuhn) When a DNA copies itself to make a new genome to pass on to a daughter cell
Any creature that scientists use to study life. Examples range from single-celled organisms such as bacteria to more complex ones such as mice.
(RAHY-buh-sohm) A molecular complex in which proteins are made. It’s composed of proteins and ribosomal RNA
(RAHY-buh-noo-clay-ik) A long, usually single-stranded chain of nucleotides. There are three major types of RNA, which are all involved in protein synthesis:
Messenger RNA (mRNA) is complementary to one of the DNA strands of a gene and carries genetic information to the ribosomefor protein synthesis.
Transfer RNA (tRNA) works with mRNA to make sure the right amino acids are inserted into the protein being made.
Ribosomal RNA (rRNA) (RAHY-buh-sohm-uhl) helps a protein separate from the ribosome when synthesis is complete.
Certain viruses contain RNA, instead of DNA, as their genetic material.
(POL-uh-muh-rays) An enzyme that makes RNA using DNA as a template in a process called transcription
When noncoding pieces of RNA, called introns, are removed and coding pieces of RNA, called exons, are joined together to produce an mRNA molecule.
A naturally occurring process in which small pieces of double-stranded RNA are used to prevent translation of messenger RNA. The process occurs in many organisms to silence genes when their protein products are no longer needed. When RNAi doesn’t work as it should, it may lead to certain diseases. RNAi has an important role in basic research allowing scientists to directly observe the effects of the loss of function of specific genes.
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A serious medical condition caused by an overwhelming immune response to infection. The body releases immune chemicals into the blood to combat the infection. Those chemicals trigger widespread inflammation, which leads to blood clots and leaky blood vessels. As a result, blood flow is impaired, depriving organs of nutrients and oxygen and leading to organ damage. There are four levels of sepsis:
Systemic inflammatory response syndrome (SIRS): Low body temperature or fever; fast heart rate; quick breathing or hyperventilation; and white blood cell count that’s either too low or too high
Sepsis: SIRS in response to a confirmed infection
Severe sepsis: Sepsis plus problems with organ function, low blood pressure, or insufficient blood flow to one or more organs
Septic shock: Sepsis with low blood pressure or insufficient blood flow to one or more organs that doesn’t improve with fluids
The effect of a drug, other than the desired effect, sometimes in an organ other than the target organ.
(tranz-DUHK-shuhn) When chemical, electrical, or biological signals are transmitted into and within a cell
A cell that can develop into many different cell types in the body. When stem cells divide, they can form more stem cells or other specialized cells.
Adult stem cells: Cells found throughout the body that replace tissue damaged by disease, injury, or age
Embryonic stem cell (em-bree-ON-ik): A cell found in early embryos that can become any kind of cell in the body
Induced pluripotent stem cells (iPS) (ploor-uh-POHT-nt): Specialized tissue or organ cells that have been reprogrammed in a lab into a stem cell-like state and can become just about any cell type
The study of how biological molecules are built. Imaging techniques allow scientists to view molecules in three dimensions to see how they are put together, how they function, and how they interact.
A molecule that binds to an enzyme and undergoes a chemical change during the ensuing reaction.
(SING-kruh-tron) A large machine that accelerates electrically charged particles to nearly the speed of light and maintains them in circular orbits. Originally designed for use by high-energy physicists, synchrotrons are now heavily used by structural biologists as a source of very intense X-rays
The science of the formation of more complex chemical molecules from simpler building blocks.
A field focused on the study of relationships and interactions between various parts of a biological system (metabolic pathways, organelles, cells, and organisms) and that integrates this information to understand how biological systems function.
(tuh-LOM-uh-rays) An enzyme that adds a repetitive segment of DNA, or telomere, to the ends of chromosomes, so the chromosomes don’t shrink during each cell division
A group of cells that act together to carry out a specific function in the body. Examples include muscle tissue, nervous system tissue (including the brain, spinal cord, and nerves), and connective tissue (including ligaments, tendons, bones, and fat). Organs are made up of tissues.
A field of study that combines cells, engineering, and materials methods, with the goal of improving or replacing biological functions.
The most powerful type of electron microscopy (EM), which uses electrons to create an image of a sample. TEM can magnify objects more than 10 million times, making the outline and some details of cells, viruses, and even some large molecules visible.
(yoo-BIH-kweh-tin) A small protein that attaches to and marks other proteins for the proteasome to destroy
(VES-ih-kuhl) A small, membrane-bounded sac that transports substances between organelles as well as to and from the cellmembrane
An infectious agent composed of proteins and genetic material (either DNA or RNA) that requires being in a host cell, such as a plant, animal, or bacterium, in order to reproduce. A virus is neither a cell nor a living organism because it can't reproduce on its own.
(kris-tl-OG-ruh-fee) A technique used to determine the detailed, three-dimensional structure of molecules. It’s based on the scattering of X-rays through a crystal of the molecule under study
(ZAHY-goht) A cell resulting from fusing an egg and a sperm
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