Biomolecules and Enzymes

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Monosaccharide Noun

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[mon-oh-sak-uh-rahyd]

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Monosaccharide

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The simplest form of carbohydrate, a single sugar molecule that serves as a building block for more complex carbohydrates.

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Example: This diagram shows that a large starch molecule (a polysaccharide) is broken down during digestion into many small glucose molecules (monosaccharides).

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Polysaccharide Noun

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[pol-ee-sak-uh-rahyd]

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Polysaccharide

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A large carbohydrate polymer composed of many monosaccharide units joined together by glycosidic bonds, used for energy or structure.

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Example: This diagram shows that a polysaccharide, like starch, is a large biomolecule made of many smaller glucose sugar molecules linked together in a chain.

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Glycosidic Linkage Noun

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[glahy-koh-sid-ik ling-kij]

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Glycosidic Linkage

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A type of covalent bond that joins a carbohydrate molecule to another group, forming disaccharides and polysaccharides.

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Example: This diagram shows how two simple sugar molecules, glucose and galactose, are joined by a special chemical bond called a glycosidic linkage to form lactose.

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Glycogen Noun

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[glahy-kuh-juhn]

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Glycogen

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The main form of glucose storage in animals, a highly branched polysaccharide found primarily in the liver and muscles.

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Example: This image shows glycogen granules as small dots within the cytoplasm of an animal cell, indicating where this energy-storing biomolecule is found.

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Amino Acid Noun

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[uh-mee-noh as-id]

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Amino Acid

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An organic molecule containing both carboxyl and amino groups, which serves as the monomer unit for building proteins.

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Example: This diagram shows that large protein molecules are broken down during digestion into their smaller building blocks, which are called amino acids.

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Peptide Bond Noun

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[pep-tahyd bond]

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Peptide Bond

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A covalent chemical bond formed between two amino acid molecules, linking them together to form polypeptide chains.

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Example: This diagram shows two amino acids linking by removing a water molecule. The new connection formed between them is called a peptide bond.

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Polypeptide Noun

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[pol-ee-pep-tahyd]

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Polypeptide

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A long, unbranched chain of amino acids linked together by peptide bonds, which folds to form a functional protein.

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Example: This diagram shows that individual amino acids (dots) link together in a sequence to form a long chain, which is a polypeptide.

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Zwitterion Noun

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[tsvit-er-ahy-on]

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Zwitterion

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A molecule, such as an amino acid, that has both a positive and a negative charge but is electrically neutral overall.

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Example: This diagram shows an amino acid (Alanine) as a zwitterion, a molecule with both a positive charge (+) and a negative charge (-).

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Hydrophobic Adjective

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[hahy-druh-foh-bik]

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Hydrophobic

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The physical property of a nonpolar molecule that is repelled by water, making it insoluble in aqueous solutions.

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Example: A water droplet beads up on a leaf because the leaf's waxy surface, made of lipid biomolecules, is hydrophobic and repels water.

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Lipid Noun

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[lip-id]

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Lipid

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A class of organic molecules, including fats and oils, that are insoluble in water and serve as energy storage.

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Example: This image shows how lipids (specifically, phospholipids) form a bilayer, with water-loving (hydrophilic) heads facing out and water-fearing (hydrophobic) tails facing in.