Cytology and Bioenergetics Flashcards

Vocabulary practice flashcards covering cytology, membrane transport mechanisms, thermodynamics, cellular respiration, photosynthesis, plant adaptations, and ecological bioenergetics.

Cytology

The branch of biology focused on the study of cell structure and function.

Cell Theory

A unifying biological concept stating that all living things are composed of one or more cells, the cell is the smallest structural and functional unit of life, and all cells arise from pre-existing cells.

Surface Area-to-Volume Ratio Constraint

The physical limitation where increasing cell volume (e.g., by 8x) results in a smaller proportional increase in surface area (e.g., 4x), making diffusion inefficient and requiring cells to remain small or possess specialized frilly surfaces.

Prokaryotic Cell

A cell type lacking a membrane-bound nucleus and internal subdivisions or organelles, characterized by a single circular chromosome in a nucleoid region, cytosol, and small loops of DNA called plasmids.

Eukaryotic Cell

A complex cell type containing a true nucleus with linear chromosomes and specialized membrane-formed compartments called organelles.

Plasmids

Small loops of DNA in prokaryotic cells that exist separate from the main circular chromosome.

Endomembrane System

A network or continuous series of membrane-bound organelles within eukaryotic cells—including the endoplasmic reticulum, Golgi body/complex, lysosomes, peroxisomes, and vacuoles/vesicles—that compartmentalize cellular processes.

Endosymbiotic Theory

The evolutionary theory stating that eukaryotic organelles such as mitochondria and chloroplasts originated from engulfed prokaryotes, supported by their circular bacterial DNA, double membranes, and independent replication.

Fluid Mosaic Model

A model describing the cell membrane structure as a mosaic of phospholipids (with charged heads and neutral tails) and embedded proteins that perform transport, reception, communication, and recognition functions.

Passive Transport

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

Membrane Transport Mechanisms

The pathways by which substances cross the lipid bilayer, including simple diffusion of lipid-soluble molecules down a gradient, facilitated diffusion via protein channels, and active transport utilizing ATP to move solutes.

Diffusion

The passive movement of dissolved or suspended solute molecules away from an area of higher concentration, driven by the kinetic energy of the molecules.

Osmosis

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

Facilitated Diffusion

Passive transport of water and water-soluble solutes across a membrane down a concentration gradient using channel proteins, gated channel proteins, or carrier proteins.

Aquaporins

Specialized channel proteins embedded in the cell membrane that facilitate the rapid passage of water molecules.

Active Transport

The movement of small molecules, ions, or macromolecules across a membrane against their concentration gradient, requiring energy (ATP) expenditure by the cell.

Sodium-Potassium Exchange Pump

An active transport mechanism that pumps sodium out of and potassium into the cell, creating an electrochemical gradient with a higher $\text{Na}^+$ concentration outside the cell.

Endocytosis

An active transport process where cells ingest bulk external materials or macromolecules, divided into phagocytosis (cell eating) and pinocytosis (cell drinking).

Exocytosis

An active transport process in which substances enclosed in vesicles are exported out of the cell by fusing with the cell membrane.

First Law of Thermodynamics

The law stating that the total amount of energy in the universe remains constant; energy cannot be created or destroyed, only transformed.

Second Law of Thermodynamics

The principle stating that energy conversions always produce some useless energy or loss of usable heat, causing systems to naturally tend toward increased entropy and disorder.

Entropy

A measure of useless energy or disorder within a system, where low entropy represents high molecular order and high entropy represents disorder.

Adenosine Tri-Phosphate (ATP)

A nucleotide composed of adenine, ribose sugar, and three phosphate groups that functions as the primary usable chemical energy currency and energy-coupling agent in cells.

ATP Energy Cycle

The continuous conversion where energy from photosynthesis or respiration yields ATP from ADP and phosphate, which is then hydrolyzed to release usable energy for biological work.

Endergonic Reaction

A chemical reaction that requires an input of energy because its products contain more free energy (\text{\Delta G}) than its reactants.

Exergonic Reaction

A chemical reaction that occurs spontaneously and releases energy because its products contain less free energy (\text{\Delta G}) than its reactants.

Enzymes

Biological protein catalysts that speed up chemical reactions by lowering the activation energy without being consumed or permanently altered in the process.

Aerobic Cellular Respiration

The catabolic process by which cells break down glucose in the presence of oxygen to release usable energy, summarized as $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + \Delta G$.

Oxidation-Reduction (Redox) Reactions

Coupled chemical reactions where oxidation represents the loss of electrons from an atom or molecule and reduction represents the gain of electrons.

Glycolysis

The initial anaerobic stage of cellular respiration occurring in the cytoplasm, where ten enzyme-catalyzed steps convert a 6-carbon glucose molecule into two 3-carbon pyruvate molecules and yield ATP.

Citric Acid Cycle (Krebs Cycle)

A cyclic metabolic pathway in the mitochondrial matrix that consumes pyruvate derivatives across two turns to generate 2 ATP, 6 NADH, and 2 $\text{FADH}_2$ electron carriers.

Electron Transport Chain

A series of membrane-bound protein complexes in the inner mitochondrial membrane that conduct redox reactions to pump protons ($\text{H}^+$) into the intermembrane space, using oxygen as the final electron acceptor.

Chemiosmosis

The generation of ATP via oxidative phosphorylation as accumulated protons ($\text{H}^+$) flow down their concentration gradient through ATP Synthase across the inner mitochondrial membrane.

Fermentation

An anaerobic process following glycolysis in which organic molecules accept hydrogen atoms from NADH, recycling $\text{NAD}^+$ so glycolysis can continue generating ATP.

Fast Glycolytic Fibers (FG)

Muscle fibers containing few mitochondria and low myoglobin content ('white' appearance) that contract rapidly and strongly during anaerobic activity and rapidly accumulate lactic acid.

Slow Oxidative Fibers (SO)

Fatigue-resistant muscle fibers packed with high mitochondria count and high myoglobin concentration ('red' appearance) powered by aerobic respiration for sustained endurance activity.

Free Radicals

Highly reactive oxygen ions generated by malfunctioning mitochondria that cause cumulative damage to cellular proteins and DNA over time.

Light-Dependent Reactions

The photosynthetic stage occurring in chloroplast thylakoids where photons excite electrons in chlorophyll, producing ATP, NADPH, and $\text{O}_2$ from split water molecules.

Calvin Cycle (Light-Independent Reactions)

The enzymatic pathway occurring in the chloroplast stroma that utilizes ATP and NADPH to fix atmospheric carbon dioxide into glucose.

Transpiration

The movement and loss of water vapor from plant tissues to the atmosphere through open stomata.

Photorespiration

A wasteful pathway in $\text{C}_3$ plants triggered by closed stomata in high temperatures, causing Rubisco to bind $\text{O}_2$ instead of $\text{CO}_2$ and consuming energy.

$\text{C}_4$ Plants

Plants with physiological adaptations that bypass photorespiration by actively pumping carbon dioxide directly to photosynthetic cells using extra chemical reactions.

CAM Plants

Arid-adapted plants that open stomata at night to absorb and convert carbon dioxide into stored organic acids, releasing it for the Calvin cycle during daylight while keeping stomata closed.

Food Web

A network displaying the multiple interconnected feeding relationships and energy transfer pathways among autotrophs, herbivores, and carnivores in an ecosystem.

Greenhouse Effect

The retention of thermal energy in Earth's atmosphere when re-emitted solar radiation is absorbed and trapped by atmospheric greenhouse gases.

Carbon Sequestration

The process by which plants and trees capture and store atmospheric carbon dioxide through photosynthetic activity.