The Structure And Function Of Biological Molecules

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alpha (a) helix

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A spiral shape constituting one form of the secondary structure of proteins, arising from a specific pattern of hydrogen bonding.

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amino acid

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An organic molecule possessing both carboxyl and amino groups. They serve as the monomers of polypeptides.

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antiparallel

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The opposite arrangement of the sugar-phosphate backbones in a DNA double helix.

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atherosclerosis

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A cardiovascular disease in which fatty deposits called plaques develop in the inner walls of the arteries, obstructing the arteries and causing them to harden.

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beta (ß) pleated sheet

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One form of the secondary structure of proteins in which the polypeptide chain folds back and forth. Two regions of the chain lie parallel to each other and are held together by hydrogen bonds.

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bioinformatics

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The use of computers, software, and mathematical models to process and integrate biological information from large data sets.

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carbohydrate

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A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides).

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catalyst

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A chemical agent that increases the rate of a reaction without being consumed by the reaction.

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cellulose

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A structural polysaccharide of plant cell walls, consisting of glucose monomers joined by ß glycosidic linkages.

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chaperonin

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A protein molecule that assists in the proper folding of other proteins.

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chitin

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A structural polysaccharide, consisting of amino sugar monomers, found in many fungal cell walls and in the exoskeletons of all arthropods.

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cholesterol

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A steroid that forms an essential component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids, such as hormones.

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collagen

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A glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue and bone; the most abundant protein in the animal kingdom.

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condensation reaction

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A reaction in which two molecules become covalently bonded to each other through the loss of a small molecule, usually water, in which case it is also called a dehydration reaction.

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dehydration reaction

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A chemical reaction in which two molecules covalently bond to each other with the removal of a water molecule.

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deoxyribonucleic acid (DNA)

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A double-stranded, helical nucleic acid molecule consisting of nucleotide monomers with a deoxyribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T); capable of replicating and determining the inherited structure of a cell’s proteins.

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deoxyribose

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The sugar component of DNA nucleotides, having one fewer hydroxyl group than ribose, the sugar component of RNA nucleotides.

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disaccharide

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A double sugar, consisting of two monosaccharides joined by a glycosidic linkage formed during dehydration synthesis.

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disulfide bridge

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A strong covalent bond formed when the sulfur of one cysteine monomer bonds to the sulfur of another cysteine monomer.

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double helix

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The form of native DNA, referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape.

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emergent properties

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New properties that arise with each step upward in the hierarchy of life, owing to the arrangement and interactions of parts as complexity increases.

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endorphin

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Any of several hormones produced in the brain and anterior pituitary that inhibits pain perception.

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enzyme

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A macromolecule serving as a catalyst, a chemical agent that changes the rate of a reaction without being consumed by the reaction.

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fat

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A lipid consisting of three fatty acids linked to one glycerol molecule; also called a triacylglycerol or triglyceride.

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fatty acid

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A long carbon chain carboxylic acid. They vary in length and in the number and location of double bonds; three linked to a glycerol molecule form a fat molecule, also known as a triacylglycerol or triglyceride.

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gene

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A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).

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glycosidic linkage

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A covalent bond formed between two monosaccharides by a dehydration reaction.

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hydrolysis

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A chemical process that lyses, or splits, molecules by the addition of water, functioning in disassembly of polymers to monomers.

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hydrophobic interaction

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A type of weak chemical bond formed when molecules that do not mix with water coalesce to exclude water.

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insulin

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A hormone secreted by pancreatic beta cells that lowers blood glucose levels. It promotes the uptake of glucose by most body cells and the synthesis and storage of glycogen in the liver and also stimulates protein and fat synthesis.

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lipid

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One of a group of compounds, including fats, phospholipids, and steroids, that mix poorly, if at all, with water.

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messenger RNA (mRNA)

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A type of RNA, synthesized using a DNA template, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein.

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monomer

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The subunit that serves as the building block of a polymer.

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monosaccharide

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The simplest carbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides. Also known as simple sugars, they have molecular formulas that are generally some multiple of CH₂O.

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nucleic acid

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A polymer (polynucleotide) consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA.

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nucleotide

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The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group.

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peptide bond

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The covalent bond between the carboxyl group on one amino acid and the amino group on another, formed by a dehydration reaction.

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phospholipid

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A lipid made up of glycerol joined to two fatty acids and a phosphate group. The hydrocarbon chains of the fatty acids act as nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head. They form bilayers that function as biological membranes.

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polymer

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A long molecule consisting of many similar or identical monomers linked together.

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polynucleotide

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A polymer consisting of many nucleotide monomers in a chain; nucleotides can be those of DNA or RNA.

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polypeptide

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A polymer (chain) of many amino acids linked together by peptide bonds.

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polysaccharide

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A polymer of many monosaccharides, formed by dehydration reactions.

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primary structure

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The level of protein structure referring to the specific sequence of amino acids.

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protein

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A functional biological molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure.

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protein kinase

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An enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein.

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purine

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One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused to a five-membered ring. Adenine (A) and guanine (G) are examples.

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pyrimidine

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One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring. Cytosine (C), thymine (T), and uracil (U) are examples.

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quaternary structure

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The particular shape of a complex, aggregate protein, defined by the characteristic three-dimensional arrangement of its constituent subunits, each a polypeptide.

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ribonucleic acid (RNA)

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A type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis, gene regulation, and as the genome of some viruses.

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ribose

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The sugar component of RNA nucleotides.

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saturated fatty acid

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A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms that are attached to the carbon skeleton.

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secondary structure

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The localized, repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bond formation between constituents of the backbone.

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starch

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A storage polysaccharide in plants, consisting entirely of glucose monomers joined by a glycosidic linkages.

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steroid

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a type of lipid characterized by a carbon skeleton consisting of four rings with various chemical groups attached.

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tertiary structure

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Irregular contortions of a protein molecule due to interactions of side chains involved in hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.

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trans fat

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An unsaturated fat containing one or more trans double bonds.

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triacylglycerol

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Three fatty acids linked to one glycerol molecule; also called a fat or a triglyceride.

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unsaturated fatty acid

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A fatty acid possessing one or more double bonds between the carbons in the hydrocarbon tail. Such bonding reduces the number of hydrogen atoms attached to the carbon skeleton.

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X-ray crystallography

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A technique that depends on the diffraction of an X-ray beam by the individual atoms of a crystallized molecule to study the three-dimensional structure of the molecule.