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Biochemistry terms


Anything that has mass and takes up space.


The simplest form of matter.


The smallest form of an element that still displays its unique properties.


Ion with a positive charge that contains more protons than electrons.


Ion with a negative charge that contains more electrons than protons.


Elements are combined to form entities called compounds.

organic compounds

Carbon-containing compounds. Important examples include carbohydrates, proteins, lipids, and nucleic acids.

inorganic compounds

For the most part, compounds containing no carbon. There are some exceptions such as carbon dioxide, carbon monoxide, and others.


Organic compound used by the cells of the human body in energy-producing reactions and as structural material. The three main types of carbohydrates are monosaccharides, disaccharides, and polysaccharides.


Organic compound composed of chains of amino acids that function as structural components, transport aids, enzymes, and cell signals, among other things.


Hydrophobic organic compounds used by cells as energy stores or building blocks. Three important lipids are fats, steroids, and phospholipids.

nucleic acid

Macromolecule composed of nucleotides, sugars, and phosphates that serve as genetic material of living organisms (DNA and RNA).

functional groups

The groups responsible for the chemical properties of organic compounds.


Lipids, made by combining glycerol and fatty acids, used as long-term energy stores in cells. They can be saturated or unsaturated.


Type of lipid.


Lipids composed of four carbon rings. Examples include cholesterol, estrogen, progesterone, and testosterone.


Lipid with both a hydrophobic tail and a hydrophillic head; the major component of cell membranes with the hydrophilic phosphate group forming the outside portion and the hydrophobic tail forming the interior of the wall.


Three-carbon molecule that combines with fatty acids to produce a variety of lipids.

fatty acid

Long carbon chain that contains a carboxyl group on one end that combines with glycerol molecules to form lipids.

saturated fat

Fat that contains no double bonds. It is associated with heart disease and atherosclerosis.

unsaturated fat

Fat that contains one or more double bonds; found in plants.


The simplest form of a carbohydrate. The most important monosaccharide is glucose, which is used in cellular respiration to provide energy for cells.


A sugar consisting of two monosaccharides bound together. Common disaccharides include sucrose, maltose, and lactose.


A carbohydrate usually composed of hundreds or thousands of monosaccharides, which acts as a storage form of energy, and as structural material in and around cells. Starch and glycogen are storage polysaccharides; cellulose and chitin are structural polysaccharides.


Storage polysaccharide made of glucose molecules; seen in plants.


Storage polysaccharide made of glucose molecules used by animals.


Polysaccharide composed of glucose used by plants to form cell walls.


Polysaccharide that is an important part of the exoskeletons of arthropods such as insects, spiders, and shellfish.


Catalytic proteins that are picky, interacting only with particular substrates. However, the enzymes can be reused and react with more than one copy of their substrate of choice and have a major effect on a reaction.


Molecules that speed up reactions by lowering the activation energy of a reaction.


Substances that enzymes act upon.

active site

Part of the enzyme that interacts with the substrate in an enzyme-substrate complex.

induced-fit model

Theory that suggests that when an enzyme and a substrate bind together, the enzyme is induced to alter its shape for a tighter active-site/substrate attachment, which places the substrate in a favorable position to react more quickly.

competitive inhibition

Condition in which an inhibitor molecule resembling the substrate binds to the active site and physically blocks the substrate from attaching.

noncompetitive inhibition

Condition in which an inhibitor molecule binds to an enzyme away from the active site, causing a change in the shape of the active site so that it can no longer interact with the substrate.

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