Macromolecules, Cell Membranes, and Cellular Transport

Comprehensive vocabulary flashcards covering macromolecules, chemical reactions (dehydration synthesis and hydrolysis), cell membrane structure and dynamics, osmosis, and passive versus active transport mechanisms.

Organic Chemistry

The branch of chemistry dedicated to studying chemicals that contain carbon.

Macromolecule

A large biological molecule built with a carbon backbone, created by bonding smaller units together.

Monomer

A single molecular subunit or building block that bonds with others to form a larger chain.

Polymer

A large molecule composed of many repeating monomers joined together in a long chain.

Dehydration Synthesis

A chemical reaction in which monomers are linked to build polymers by removing a molecule of water ($H_2O$).

Hydrolysis

A chemical reaction that breaks a polymer apart into individual monomers by adding a molecule of water ($H_2O$).

Carbohydrate

A polar macromolecule containing only carbon, hydrogen, and oxygen ($C$, $H$, and $O$) that functions as a source of chemical energy, cell recognition markers, and structural support.

Monosaccharide

The monomer building block of carbohydrates, representing a simple sugar such as glucose or fructose.

Disaccharide

A carbohydrate composed of two joined monosaccharide units, such as lactose, maltose, or sucrose.

Polysaccharide

A carbohydrate polymer formed by three or more monosaccharides linked together, including starch, glycogen, and cellulose.

Cellulose

A tough carbohydrate polysaccharide that serves as the main structural component of plant cell walls (fiber).

Glycogen

A carbohydrate polysaccharide used by animals to store energy.

Lipid

A non-polar, hydrophobic macromolecule composed of $C$, $H$, $O$ (and $P$) that includes fats, oils, and waxes and stores more energy than carbohydrates.

Fatty Acids and Glycerol

The monomer subunits that join together to form lipid molecules.

Hydrophobic

A property describing non-polar molecules that cannot form hydrogen bonds with water, cannot dissolve in water, and cannot get wet.

Protein

A macromolecule composed of $C$, $H$, $O$, $N$, and $S$ that performs functions including structural support, transport, catalysis, and immunity.

Amino Acid

The monomer of proteins; there are $20$ different types, each characterized by a distinct R-group.

Keratin

A structural protein that forms hair and nails.

Enzyme

A specialized catalytic protein that speeds up chemical reactions by efficiently building or breaking down substances.

Hemoglobin

A transport protein in red blood cells that binds and carries oxygen throughout the body.

Nucleic Acid

A macromolecule composed of $C$, $H$, $O$, $P$, and $N$—such as DNA or RNA—whose primary function is storing inheritable genetic information.

Nucleotide

The monomer building block of nucleic acids, consisting of a phosphate group, a pentose sugar, and a nitrogenous base.

Homeostasis

The biological process of maintaining a stable internal cellular environment, keeping conditions like pH and temperature balanced.

Fluid Mosaic Model

A structural model describing the cell membrane as a flexible mosaic of constantly moving phospholipids, proteins, cholesterol, and carbohydrates.

Phospholipid

A membrane molecule consisting of a hydrophilic (polar) phosphate group head and two hydrophobic (non-polar) fatty acid tails.

Cholesterol

A lipid embedded in the plasma membrane that prevents it from becoming too fluid and keeps the fatty acid tails from sticking together.

Glycoprotein

A membrane structure consisting of carbohydrates attached to proteins, essential for cell identification and immune responses.

Glycolipid

A membrane structure consisting of carbohydrates attached to lipids, functioning in cell-to-cell communication and immune responses.

Selectively Permeable

A property of the cell membrane that allows only certain substances to cross while barring others.

Concentration

The measure of the amount of a given substance in a defined space.

Diffusion

The passive movement of molecules from an area of higher concentration to an area of lower concentration down their gradient.

Dynamic Equilibrium

The state reached when molecules are evenly distributed throughout an area and continue moving with no net change in concentration.

Passive Transport

The movement of substances across a cell membrane down their concentration gradient without the expenditure of cellular energy.

Facilitated Diffusion

Passive transport in which molecules move across a membrane down their concentration gradient with the assistance of channel or carrier proteins.

Channel Protein

A transmembrane protein that forms an open path or pore through the lipid bilayer, allowing specific materials to cross.

Carrier Protein

A transport protein that binds specific solute particles and changes conformation to move them across the plasma membrane.

Solute

The substance that is dissolved by a liquid solvent to produce a solution.

Solvent

The dissolving agent (such as water) capable of dissolving solutes to create a solution.

Osmosis

The diffusion of water across a semipermeable membrane from an area of higher water concentration (lower solute) to lower water concentration (higher solute).

Isotonic Solution

A solution that has an equal solute concentration compared to the inside of the cell, providing the ideal condition for animal cells.

Hypertonic Solution

A solution with a higher solute concentration than the cytoplasm of the cell, causing water to exit and the cell to shrink.

Hypotonic Solution

A solution with a lower solute concentration than the cell, causing water to rush in.

Lysis

The rupture or bursting of an animal cell caused by excessive water intake in a hypotonic solution.

Turgor Pressure

The outward hydrostatic pressure exerted against a plant cell wall when the central vacuole fills with water in a hypotonic environment.

Active Transport

The movement of substances across a cell membrane against their concentration gradient (from low to high) requiring cellular energy.

Protein Pump

A transmembrane protein that uses cellular energy to force molecules or ions (such as sodium and potassium) against their concentration gradient.

Endocytosis

An active transport mechanism by which a cell takes in external materials through the inward folding of the membrane to create vesicles or vacuoles.

Phagocytosis

A form of endocytosis ('cell eating') where large particles or entire cells are engulfed into food vacuoles using pseudopodia.

Pinocytosis

A form of endocytosis ('cell drinking') where the cell membrane invaginates to form fluid-filled vesicles.

Exocytosis

An active transport process in which intracellular vesicles fuse with the plasma membrane to expel substances from the cell.