Biochemistry Lecture Flashcards

Vocabulary flashcards covering introductory biochemistry concepts including atomic structure, chemical bonds, aqueous solutions, pH, biological macromolecules, enzymes, and membrane transport.

Atom

The smallest chemical unit that makes up an element.

Atomic number

The number of protons in each atom of an element, which determines the identity of the element.

Ion

An atom with a net electric charge formed when it loses or gains electrons.

Molecule

Two or more atoms bonded together through interactions between their electrons.

Reactants

The starting substances in a chemical reaction that undergo change, shown on the left side of a chemical equation.

Products

The new substances formed in a chemical reaction, shown on the right side of a chemical equation.

Subscripts

Small numbers in a chemical formula that specify the number of atoms of the element directly to their left.

Coefficients

Large whole numbers placed in front of chemical formulas that state how many units of that entire molecule are present.

Ionic bond

A chemical bond formed when electrons are completely transferred from one atom to another, resulting in oppositely charged ions that attract each other.

Nonpolar covalent bond

A chemical bond formed when two atoms share electrons equally, resulting in an even charge distribution across the molecule.

Polar covalent bond

A chemical bond formed between atoms with different attractions for electrons, causing unequal sharing of electrons and a charge difference across the molecule.

Hydrogen bond

A weak attraction between an atom with a slight positive charge and an atom with a slight negative charge on another molecule or a different part of the same molecule.

Solute

A substance that is dissolved in a solvent to form a solution.

Solvent

The liquid component present in the greater amount within a solution.

Aqueous solution

A solution in which water acts as the solvent.

Hydrophilic

Describes molecules with ionic or polar covalent bonds that readily dissolve in water (“water-loving”).

Hydrophobic

Describes nonpolar molecules that do not dissolve in water (“water-fearing”).

Amphipathic

Describes a molecule that contains both hydrophilic and hydrophobic regions.

Hydrophobic force

The force exerted by the hydrogen-bonded network of water molecules that brings two nonpolar surfaces together by excluding water between them.

pH

A measure of the concentration of hydrogen ions ($H^+$) in a fluid.

Acid

A solution containing a high concentration of hydrogen ions ($H^+$) with a pH value below 7.

Base

A solution containing a low concentration of hydrogen ions ($H^+$) with a pH value above 7.

Organic molecule

A biologically important molecule that contains both carbon and hydrogen.

Monomer

A small building-block molecule that can bind with other similar molecules to form a polymer.

Polymer

A long molecule consisting of many similar building blocks (monomers) connected together.

Dehydration synthesis

A reaction that links monomers together into a polymer by releasing a water molecule and consuming energy.

Hydrolysis

A reaction that breaks polymers apart into individual monomers by adding a water molecule and releasing energy.

Monosaccharide

A single sugar monomer, such as glucose, fructose, or galactose.

Disaccharide

A carbohydrate composed of two monosaccharides joined together, such as sucrose, lactose, or maltose.

Polysaccharide

A carbohydrate polymer composed of chains of hundreds or thousands of monosaccharides, such as cellulose or chitin.

Amino acid

The monomer of proteins; consists of a common backbone structure and one of 20 unique side chains (R groups) that determine its specific chemical properties.

Polypeptide

A long chain of amino acids linked together by peptide bonds.

Denaturation

The process in which environmental deviations from homeostasis (such as excessive heat) cause a protein to unravel and lose its shape, making it non-functional.

Enzyme

A specialized protein that acts as a biological catalyst to accelerate specific chemical reactions without being consumed.

Active site

The specific region of an enzyme that is structurally shaped to bind particular reactant molecules (substrates).

Substrate

The specific reactant molecule that binds to the active site of an enzyme.

Cofactor

A nonprotein chemical compound (such as an inorganic mineral or organic coenzyme) required by an enzyme for its catalytic activity.

Nucleic acid

A polymer (such as DNA or RNA) responsible for the storage, expression, and transmission of genetic information.

Nucleotide

The structural monomer of nucleic acids, consisting of a sugar, a phosphate group, and a nitrogenous base.

Adenosine triphosphate (ATP)

A nucleotide that stores chemical energy in its easily hydrolyzed phosphoanhydride bonds.

Lipid

A class of hydrophobic organic molecules that do not form true polymers, including phospholipids and cholesterol.

Fluid mosaic model

A structural model describing cell membranes as dynamic arrangements of phospholipids, proteins, and cholesterol that move laterally within the lipid bilayer.

Selective permeability

The property of a cell membrane that allows only certain substances (small, nonpolar, uncharged molecules) to cross the hydrophobic core directly.

Diffusion

The passive process by which molecules spread out evenly into available space, moving down their concentration gradient.

Passive transport

The movement of substances across a membrane down their concentration gradient without requiring energy expenditure.

Osmosis

The net diffusion of water across a selectively permeable membrane toward the region with a higher solute concentration.

Isotonic solution

A solution whose solute concentration is equal to the solute concentration inside a cell.

Hypertonic solution

A solution with a higher solute concentration relative to the inside of a cell, causing animal cells to crenate (shrivel) and plant cells to undergo plasmolysis.

Hypotonic solution

A solution with a lower solute concentration relative to the inside of a cell, causing animal cells to lyse (burst) and plant cells to become turgid.

Plasmolysis

The phenomenon in plant cells where the cytoplasm and plasma membrane shrink away from the rigid cell wall in a hypertonic environment.

Turgid

The firm state of a plant cell when its membrane is pushed tightly against the cell wall by internal water pressure in a hypotonic environment.

Facilitated diffusion

A form of passive transport where molecules move down their concentration gradient through specific transmembrane protein channels or carriers.

Active transport

The energy-requiring movement of substances across a cell membrane against their concentration gradient using transmembrane proteins.

Bulk transport

The transport of large particles or large quantities of substances across the membrane using membrane-bound vesicles.

Endocytosis

A process of bulk transport where the cell membrane invaginates around extracellular material and pinches off to form an intracellular vesicle.

Exocytosis

A process of bulk transport where an intracellular vesicle fuses with the cell membrane to secrete its contents to the exterior of the cell.