Structure and Functions of Biological Molecules

Vocabulary flashcards covering the four major biological molecules: carbohydrates, lipids, nucleic acids, and proteins, including their structural components, chemical bonds, and metabolic roles.

Biological molecules

Essential building blocks of life that perform a wide range of structural and functional roles in living organisms, including carbohydrates, lipids, proteins, and nucleic acids.

Molecule

Two or more chemically joined atoms.

Ionic bond

The result of electrical attraction between two ions with opposite charges, generally forming between an atom with an almost empty outermost shell and one with a nearly full valence shell.

Covalent bond

A bond where two atoms share electrons, which travel around both nuclei and strongly connect the atoms together.

Hydrogen bond

An attraction between opposite partial charges on adjacent molecules, or within a single large molecule, where the positive charge is always a hydrogen atom.

Organic molecules

Chemical compounds that contain both carbon and hydrogen.

Hydrocarbons

Organic molecules consisting almost entirely of carbon and hydrogen, such as methane ($CH_4$).

Polymers

Chains of smaller molecular subunits called monomers.

Dehydration synthesis

A chemical reaction, also called a condensation reaction, used to link monomers into polymers by removing a hydroxyl group from one molecule and a hydrogen atom from another to form $H_2O$.

Hydrolysis

A chemical reaction that breaks covalent bonds linking monomers by using atoms from water to add a hydroxyl group to one molecule and a hydrogen atom to another.

Carbohydrates

Organic compounds consisting of simple sugars and complex carbohydrates that serve as the body's primary source of energy.

Monosaccharides

The smallest carbohydrates, usually containing five or six carbon atoms, such as glucose and fructose ($C_6H_{12}O_6$).

Disaccharide

Two monosaccharides joined by a glycosidic linkage through dehydration synthesis.

Oligosaccharides

Carbohydrate chains consisting of 3 to 100 monomers.

Polysaccharides

Huge molecules consisting of hundreds or thousands of monosaccharide monomers, such as cellulose, chitin, starch, and glycogen.

Glycogenesis

The formation of glycogen from glucose, occurring in the liver and muscle cells when blood glucose levels are high.

Glycogenolysis

The process of breaking down glycogen into glucose-6-phosphate to maintain blood glucose levels or provide immediate energy.

Gluconeogenesis

The production of glucose from non-carbohydrate sources such as lactate and pyruvate, principally occurring in the liver and kidneys.

Starch

A polymer of glucose monomers stored by plants as granules within plastids to stockpile surplus glucose.

Glycogen

A highly branched animal equivalent of starch stored mainly in liver and muscle cells of vertebrates.

Cellulose

An unbranched polysaccharide that is the most abundant organic compound on Earth and a major component of plant cell walls.

Chitin

A nitrogen-containing polysaccharide used by arthropods to build exoskeletons and by fungi for cell walls.

Lipids

Hydrophobic organic compounds that do not dissolve in water and consist of diverse structures rather than long chains of monomers.

Triglyceride

Commonly known as fat, it consists of three fatty acids linked to one glycerol molecule.

Saturated fatty acid

A fatty acid with no double bonds between carbon atoms, meaning the carbon skeleton is fully bonded with hydrogen atoms.

Unsaturated fatty acid

A fatty acid with one or more double bonds, often containing cis double bonds that create a kink in the hydrocarbon chain.

Trans fats

Unsaturated fats with straight fatty acid tails due to trans double bonds, commonly found in fast and fried foods.

Phospholipids

Molecules with a hydrophilic head and two hydrophobic tails that form the bilayers of cell membranes.

Steroids

Lipids characterized by a carbon skeleton consisting of four fused rings, such as cholesterol.

Lipogenesis

The process of converting excess acetyl CoA generated by glycolysis into fatty acids, triglycerides, and other lipids.

Lipolysis

The process of breaking down triglycerides into fatty acids and glycerol via hydrolysis to obtain energy.

Nucleic acids

Polymers made of monomers called nucleotides, including DNA and RNA, which store and transmit genetic information.

Nucleotide

A monomer consisting of a five-carbon sugar (ribose or deoxyribose), a phosphate group, and a nitrogenous base.

Pyrimidines

A family of nitrogenous bases with one six-membered ring, including cytosine (C), thymine (T), and uracil (U).

Purines

A family of nitrogenous bases with a six-membered ring fused to a five-membered ring, including adenine (A) and guanine (G).

Gene expression

The process by which DNA directs protein synthesis through an RNA intermediate.

ATP (Adenosine triphosphate)

A modified RNA nucleotide that carries the energy cells use for many biological functions.

Amino acids

The 20 organic molecules that serve as the building blocks of proteins, categorized by the properties of their side chains (R groups).

Peptide bond

A covalent bond formed by a dehydration reaction between two amino acids.

Primary (1°) structure

The linear sequence of amino acids in a polypeptide chain linked by peptide bonds.

Secondary (2°) structure

Folding of the amino acid chain into coils (alpha helices) or sheets (beta sheets) due to hydrogen bonds.

Tertiary (3°) structure

The overall three-dimensional shape of a polypeptide resulting from interactions between side chains (R groups).

Quaternary (4°) structure

The structure resulting from interactions between multiple polypeptide subunits, such as in collagen or hemoglobin.

Denaturation

The loss of a protein's functional shape due to changes in heat, salt concentration, or pH.

Enzymes

Proteins that act as catalysts by providing an alternative reaction site and lowering the energy and time required for reactions.