Energetics, Cell Structure, and Membrane Transport Vocabulary

Vocabulary practice flashcards covering cell energetics, organelles, cytoskeleton, and membrane transport concepts from lecture notes.

Free Energy

Energy available to perform useful work in a system under uniform temperature and pressure.

Potential Energy

Stored energy due to an object's or system's position, arrangement, or internal chemical interactions.

Kinetic Energy

The energy associated with the random or direct motion of atoms, molecules, or objects.

Exergonic Reaction

A spontaneous reaction that proceeds with a net release of free energy ($\Delta G < 0$).

Endergonic Reaction

A nonspontaneous reaction that absorbs free energy from its surroundings ($\Delta G > 0$).

Change in Gibbs Free Energy ($\Delta G$)

The difference between the free energy of the final state and the initial state, calculated as $\Delta G = \Delta H - T\Delta S$.

Enthalpy ($\Delta H$)

The change in heat energy absorbed or released by a chemical system at constant pressure.

Entropy ($\Delta S$)

A measure of disorder, randomness, or the dispersal of energy and matter among possible microscopic arrangements.

Adenosine Triphosphate (ATP)

The primary cellular energy carrier, holding four negative charges at physiological $\text{pH} \approx 7$ ($\text{ATP}^{4-}$) that create high electrostatic repulsion and potential energy.

Phosphorylation

The transfer of a phosphate group from ATP to another molecule or protein, increasing its potential energy or inducing a structural shape change.

Energetic Coupling

The mechanism of driving an endergonic (unfavorable) reaction forward by linking it to an exergonic (favorable) process such as ATP hydrolysis.

Hexokinase

The enzyme that mechanistically couples the unfavorable phosphorylation of glucose to the favorable hydrolysis of ATP, resulting in an overall exergonic reaction ($\Delta G^{\circ\prime} = -16.7\,\text{kJ}\,\text{mol}^{-1}$).

Prokaryotic Cell

A cell type lacking a membrane-enclosed nucleus and membrane-bound organelles, containing its genetic material in an unbound nucleoid.

Eukaryotic Cell

A cell type containing a double-membrane-bound nucleus housing linear chromosomes along with membrane-bound organelles.

Archaea

A domain of single-celled prokaryotic extremophiles adapted to habitats such as deep sea vents, hot springs, or environments with extreme pH and salinity.

Peptidoglycan

The mesh-like material in bacterial cell walls composed of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) sugars cross-linked by short peptides.

Nuclear Envelope

The double membrane surrounding the eukaryotic nucleus, fitted with nuclear pores that regulate molecular traffic between the nucleus and cytoplasm.

Cristae

Infoldings of the inner mitochondrial membrane that house the electron transport chain and ATP synthase complexes for ATP generation.

Prokaryotic Flagella

Locomotive appendages made of large filaments that rotate $360^\circ$ to drive bacterial movement.

Turgor Pressure

The fluid pressure exerted by water inside the plant central vacuole pushing outward against the cell wall to maintain structural rigidity.

Chloroplast

A double-membraned plant organelle containing thylakoids and stroma that performs photosynthesis by converting solar energy into chemical energy.

Chlorophyll

The photosynthetic pigment embedded in thylakoid membranes that absorbs blue and red wavelengths while reflecting green light.

Endomembrane System

A functional group of eukaryotic membranes and organelles working together to synthesize, modify, package, and transport lipids and proteins.

Rough Endoplasmic Reticulum (Rough ER)

A region of the endoplasmic reticulum studded with ribosomes on its outer surface, specialized for protein synthesis, folding, and processing.

Smooth Endoplasmic Reticulum (Smooth ER)

A region of the ER lacking ribosomes that functions in lipid synthesis, carbohydrate metabolism, calcium storage, and chemical detoxification.

Golgi Apparatus

An organelle of flattened membranous sacs (cisternae) with a cis receiving face and a trans shipping face that modifies, sorts, and packages ER products.

Microfilaments (Actin Filaments)

Cytoskeletal fibers constructed from two twisted strands of G-actin subunits that maintain cell shape, support the cell cortex, and drive muscle contraction alongside myosin.

Intermediate Filaments

Cable-like cytoskeletal elements formed from fibrous proteins such as keratins and lamins that provide mechanical strength and reinforce the nuclear envelope.

Microtubules

Hollow cytoskeletal tubes made of $\alpha$-tubulin and $\beta$-tubulin dimers that guide organelle movement, separate chromosomes, and form cilia and flagella.

Kinesin

A motor protein that hydrolyzes ATP to undergo conformational shape changes and walk along microtubule tracks carrying membrane vesicles.

Messenger RNA (mRNA)

An RNA copy of a specific gene synthesized in the nucleus that exits through nuclear pores to provide blueprints for ribosomal protein synthesis.

Amphipathic

Refers to a molecule possessing both hydrophilic (polar) and hydrophobic (nonpolar) chemical regions.

Fluid Mosaic Model

A model describing the plasma membrane as a dynamic, fluid bilayer of phospholipids mixed with proteins, cholesterol, and oligosaccharides.

Oligosaccharides

Short sugar chains ($6$ to $10$ units long) extending from the exterior cell membrane surface that serve as cellular recognition markers.

Integral Membrane Proteins

Proteins embedded directly into the phospholipid bilayer, including transmembrane proteins that extend entirely across both lipid layers.

Peripheral Membrane Proteins

Proteins bound to the interior or exterior surface of the phospholipid bilayer without penetrating the hydrophobic core.

Saturated Fatty Acid Tails

Hydrocarbon chains lacking carbon-carbon double bonds, forming straight structures that pack closely together to decrease membrane fluidity.

Unsaturated Fatty Acid Tails

Hydrocarbon chains containing one or more carbon-carbon double bonds, creating kinks that prevent tight packing and increase membrane fluidity.

Cholesterol

An amphipathic steroid with four fused rings that integrates into animal cell membranes to strengthen hydrophobic interactions and restrict lipid movement.

Membrane Fluidity

The degree to which lipids and proteins freely move laterally within the cell membrane, enhanced by higher thermal energy, shorter tails, and unsaturated bonds.

Selective Permeability

The property of a plasma membrane that lets small, nonpolar, uncharged molecules cross freely while restricting large, polar, or charged species.

Diffusion

The spontaneous net movement of solutes down a concentration gradient from higher concentration to lower concentration areas.

Osmosis

The passive diffusion of water molecules across a selectively permeable membrane toward a region of higher solute concentration.

Facilitated Diffusion

The passive movement of polar or charged substances down their concentration gradient using transmembrane channels or carrier proteins without ATP.

Channel Proteins

Transmembrane proteins that form open hydrophilic tunnels allowing specific ions or water molecules to diffuse passively through the lipid bilayer.

Cystic Fibrosis Transmembrane Conductance Regulator (CFTR)

An ATP-regulated chloride channel protein facilitating passive $\text{Cl}^-$ movement down its concentration gradient when open; mutations cause cystic fibrosis.

Carrier Proteins

Transmembrane proteins that undergo a conformational shape change upon binding a specific target molecule to release it on the opposite side of the membrane.

Glucose Transporter 1 (Glut1)

A specific membrane carrier protein that undergoes a shape change following random glucose collisions to transport glucose passively into cells.

Active Transport

The nonspontaneous transport of ions or molecules across a cell membrane against their concentration gradient using transmembrane protein pumps and ATP energy.

Sodium-Potassium Pump ($\text{Na}^+/\text{K}^+$-ATPase)

A transmembrane active transport protein that hydrolyzes ATP to pump $3\,\text{Na}^+$ ions out of the cell and $2\,\text{K}^+$ ions into the cell.