Biochemistry, Cell Membrane Structure, and Cellular Transport

Comprehensive vocabulary flashcards covering atomic structure, organic and inorganic biomolecules, classes of polymers and monomers, pH, cell membrane anatomy, and mechanisms of passive and active cellular transport.

Biochemistry

The branch of science focused on the chemistry of life and how organisms function on a molecular level.

Atom

The smallest unit of matter, composed of three subatomic particles: protons and neutrons in a central nucleus, and electrons circulating in surrounding orbits.

Proton

A subatomic particle carrying a positive electrical charge ($+$) located in the nucleus at the center of an atom.

Neutron

A subatomic particle that carries no electrical charge and resides within the nucleus of an atom.

Electron

A negatively charged ($-$) subatomic particle in constant motion within orbits outside the nucleus that participates directly in chemical bonding.

Element

A distinct kind of atom defined by its unique number of protons; neutral elements have an equal number of protons and electrons.

Synthesis

The biochemical process by which living organisms combine smaller molecules and atoms together to construct larger, more complex molecules.

Molecule

A particle of a substance formed when specific elements are chemically bonded together in a fixed, specific ratio.

Covalent Bond

A strong chemical bond formed when two atoms share outer valence electrons to complete their outer shells, storing chemical potential energy.

Ionic Bond

A chemical attraction between oppositely charged ions ($+$ or $-$) formed when one atom transfers electrons to another, such as in table salt ($\text{NaCl}$).

Organic Molecule

A carbon-based molecule characteristic of living organisms that contains both carbon ($\text{C}$) and hydrogen ($\text{H}$) atoms bonded together.

Inorganic Molecule

A molecule that does not contain both carbon and hydrogen atoms together (for example, $\text{H}_2\text{O}$, $\text{CO}_2$, and $\text{NaCl}$).

Polymer

A large, complex macromolecule constructed from repeating smaller subunits (monomers) joined by chemical bonds.

Monomer

A small molecular subunit or building block that chemically links with other identical or similar subunits to build a polymer.

Carbohydrate

An organic biomolecule composed of carbon, hydrogen, and oxygen ($\text{C, H, O}$) that includes simple sugars and complex starches.

Monosaccharide

A single simple sugar unit (such as glucose, galactose, or fructose) that serves as the basic monomer subunit of carbohydrates.

Polysaccharide

A complex carbohydrate polymer composed of long chains of repeating monosaccharide subunits, including starch, glycogen, and cellulose.

Lipid

A hydrophobic biomolecule composed of fatty acids and glycerol that includes fats, oils, and waxes.

Fatty Acids and Glycerol

The fundamental monomer subunits that chemically bond to form lipid molecules.

Protein

A macromolecule composed of carbon, hydrogen, oxygen, and nitrogen ($\text{C, H, O, N}$) that functions as enzymes, antibodies, hormones, structural components, and transport channels.

Amino Acid

The monomer building block of proteins, featuring an amino group ($-\text{NH}_2$), a carboxyl group ($-\text{COOH}$), and a distinctive radical ($\text{R}$) group.

Peptide Bond

The covalent linkage formed between the amino group of one amino acid and the carboxyl group of an adjacent amino acid during protein synthesis.

Nucleic Acid

An organic biomolecule (such as $\text{DNA}$, $\text{RNA}$, and $\text{ATP}$) responsible for storing, transmitting, and utilizing genetic information and cellular energy.

Nucleotide

The basic monomer subunit of nucleic acids, consisting of a phosphate group, a $5$-carbon sugar, and a nitrogenous base.

pH Scale

A scale ranging from $0$ to $14$ used to measure the acidity or alkalinity of an aqueous solution, with $7$ being neutral.

Acid

A substance with a pH less than $7$ that produces an excess of hydrogen ions ($\text{H}^+$) in solution.

Base

An alkaline substance with a pH greater than $7$ that produces an excess of hydroxide ions ($\text{OH}^-$) in solution.

Cell Membrane

A selectively permeable boundary surrounding the cell that regulates substance movement, separates the cytoplasm from the external environment, and facilitates cellular communication.

Phospholipid

The structural lipid of the cell membrane, consisting of a polar hydrophilic phosphate head and two nonpolar hydrophobic fatty acid tails.

Selectively Permeable

A property of biological membranes that allows only certain substances to pass through while preventing the passage of others.

Passive Transport

The movement of substances across a cell membrane along their concentration gradient (from high to low concentration) without consuming cellular energy ($\text{ATP}$).

Diffusion

The net passive movement of particles from a region of higher concentration to a region of lower concentration driven by random thermal motion.

Facilitated Diffusion

A form of passive transport where ions or polar molecules cross the membrane down their concentration gradient using specific channel or carrier proteins.

Osmosis

The passive diffusion of water molecules across a semi-permeable membrane from an area of higher water concentration to an area of lower water concentration.

Aquaporin

A specialized membrane channel protein that enables rapid facilitated diffusion of water molecules across the phospholipid bilayer.

Active Transport

The energy-requiring ($\text{ATP}$) movement of particles across the cell membrane against their concentration gradient (from low to high concentration) or via membrane shape changes.

Endocytosis

An active transport process in which the cell membrane folds inward to bring external materials or large particles into the cell within vesicles.

Phagocytosis

A type of endocytosis where a cell extends pseudopods to engulf large solid particles, food, or other cells into a vacuole.

Pinocytosis

A type of endocytosis involving the pinching in of the cell membrane to take in extracellular fluid and dissolved solutes within small vesicles.

Exocytosis

An active transport mechanism by which internal vesicles fuse with the cell membrane to discharge substances or cellular waste out of the cell.

Hypertonic Solution

An external environment having a higher solute concentration and lower water concentration than the cell interior, causing net water loss and cell shrinkage.

Hypotonic Solution

An external environment having a lower solute concentration and higher water concentration than the cell interior, causing water influx and cell swelling.

Isotonic Solution

A solution whose solute and water concentrations equal those inside the cell, resulting in no net movement of water across the membrane.