Cell Biology and Membrane Transport

Vocabulary practice flashcards covering cell structure, organelles, plasma membrane components, cellular energy (ATP/ADP), and modes of cellular transport.

Plasma Membrane

The protective and enclosing barrier of all types of cells that encloses the cytoplasm, composed of a thin layer of phospholipids with embedded proteins.

Phospholipid Bilayer

The structural basis of the cell membrane, featuring a double layer of phospholipids with hydrophilic heads facing the aqueous fluids and hydrophobic tails facing inward.

Nucleus

A membrane-bound organelle that protects DNA and provides instructions for cell activities, enclosed by a nuclear envelope that separates chromatin from the cytoplasm.

Chromatin

The material in the cell nucleus consisting of DNA packaged together with proteins.

Ribosome

A non-membrane-bound structure found throughout the cytoplasm in both eukaryotic and prokaryotic cells that manufactures proteins using instructions from DNA.

Endomembrane System

A collection of interrelated cellular membranes and organelles that includes the endoplasmic reticulum, Golgi apparatus, lysosomes, and vacuoles.

Rough Endoplasmic Reticulum

A membrane-bound network studded with ribosomes where synthesized polypeptides are threaded inside, modified, and packaged into transport vesicles.

Smooth Endoplasmic Reticulum

A region of the endoplasmic reticulum that lacks ribosomes on its outer surface.

Golgi Apparatus

An organelle featuring a receiving side and a shipping side that accepts transport vesicles from the rough ER, modifies products, and pinches off new vesicles.

Chloroplast

An organelle found only in plant cells that performs photosynthesis by converting sunlight into chemical energy to build sugars.

Photosynthesis

The biological process occurring within chloroplasts that utilizes sunlight to build sugars.

Mitochondria

Organelles found in all eukaryotic cells that carry out cellular respiration by breaking down sugars to produce energy in the form of ATP.

Cellular Respiration

The metabolic pathway by which cells harvest chemical energy from fuel molecules such as glucose to synthesize ATP.

Cytoskeleton

A structural network of protein fibers responsible for maintaining cell shape and facilitating cell movement.

Microtubules

Cytoskeleton protein fibers that support cell shape and drive motility, such as the crawling locomotion of an Amoeba through rapid degradation and rebuilding.

Chemical Energy

Potential energy stored within the covalent chemical bonds of macromolecules and food fuel molecules.

ATP (Adenosine Triphosphate)

The primary energy unit for cellular work that acts as a rechargeable battery, releasing energy when converted into ADP and an inorganic phosphate group.

ADP (Adenosine Diphosphate)

The lower-energy, uncharged form of the cellular energy molecule containing two phosphate groups that is re-energized into ATP via cellular respiration.

Cell Surface Markers

Surface membrane structures consisting of a carbohydrate portion attached to a protein portion that identify the specific type of cell.

Receptor Proteins

Membrane proteins that recognize and bind to external chemical substances outside the cell.

Transport Proteins

Membrane proteins that span or embed within the bilayer to assist specific substances in crossing the plasma membrane.

Diffusion

The passive net movement of molecules down their concentration gradient from an area of high concentration to low concentration until equilibrium is reached, without requiring energy.

Facilitated Transport

The passive movement of substances across a membrane down their concentration gradient (high to low) with the assistance of membrane transport proteins, requiring no energy.

Aquaporin

A specialized channel protein embedded within the plasma membrane that facilitates the rapid diffusion of water across the bilayer.

Osmosis

The passive transport of water across a semipermeable membrane from an area of higher water concentration to lower water concentration toward equilibrium, determined by solute concentrations.

Isotonic Solution

A solution where solute concentration outside the cell equals solute concentration inside, resulting in equal movement of water in and out of the cell so size remains constant.

Hypotonic Solution

A solution having a lower solute concentration than the inside of the cell, causing net water flow into the cell and leading to swelling (normal turgid state in plants; lysis in animal cells).

Hypertonic Solution

A solution having a higher solute concentration than the inside of the cell, driving water out of the cell and causing it to shrivel or shrink.

Turgor Pressure

The hydrostatic pressure exerted by a plant cell's internal fluid contents against its cell wall, keeping the cell in a firm (turgid) state.

Active Transport

The movement of substances across the plasma membrane against their concentration gradient (from low to high concentration), requiring energy in the form of ATP.

Sodium-Potassium Pump

An active transport carrier protein that hydrolyzes ATP to export three sodium ions ($\text{Na}^+$) out of the cell and import two potassium ions ($\text{K}^+$) into the cell.

Endocytosis

An active transport process that uses membrane movement and vesicle formation to bring large particles or fluids into the cell, requiring ATP.

Exocytosis

An active transport mechanism by which intracellular vesicles fuse with the plasma membrane to secrete substances out of the cell, requiring ATP.