General Biology 01 - Cell Specialization, Transport, and Metabolism

Vocabulary flashcards focusing on biological terms, cellular specialization, cell transport mechanisms, mitosis, membrane structural components, enzymes, and redox dynamics based on lecture notes.

Parenchyma Cells

The most abundant plant cells, featuring thin, flexible primary cell walls and large central vacuoles; they are living at maturity and function in photosynthesis, storage, growth, and wound repair.

Collenchyma Cells

Elongated, flexible living plant cells with unevenly thickened primary cell walls located beneath stems and leaves to provide flexible structural support to growing tissues.

Sclerenchyma Cells

Plant cells with thick, lignified secondary cell walls that are dead at maturity, providing mechanical strength and structural support to mature, non-growing regions.

Tracheids

Elongated, tapered xylem cells responsible for transporting water and dissolved minerals throughout the plant.

Vessel Elements

Shorter and wider xylem cells found only in flowering plants that line up end-to-end to form continuous tubes for efficient water transport.

Sieve Tube Elements

Elongated phloem cells connected end-to-end by sieve plates, serving as the primary pathway for sugar transport across the plant.

Companion Cells

Specialized phloem cells connected to sieve tube elements that supply ATP and metabolic support.

Guard Cells

Epidermal cells that surround stomata to regulate their opening and closing, controlling $CO_2$ intake as well as $O_2$ and water vapor release.

Trichomes

Hair-like epidermal projections on plant surfaces that reduce transpiration, reflect sunlight, and deter herbivores through toxins or essential oils.

Goblet Cells

Unicellular epithelial cells that produce and secrete mucins to form a protective mucus layer and release antimicrobial peptides.

Skeletal Muscle

Striated, multinucleated, voluntary muscle tissue consisting of long cylindrical fibers attached to bones that contain sarcomeres to generate body movement.

Cardiac Muscle

Striated, involuntary, branched muscle tissue found only in the heart that is rich in mitochondria and capable of pacemaking through electrical impulses.

Smooth Muscle

Non-striated, involuntary, spindle-shaped muscle tissue with a single nucleus that controls blood pressure, airway diameter, and peristalsis.

Fibroblasts

The most common connective tissue cells, responsible for synthesizing collagen, elastin, and fibronectin to maintain matrix integrity and repair wounds.

Mast Cells

Immune cells located in connective tissue containing histamine granules that detect pathogens and allergens to trigger inflammatory and allergic responses.

Alveolar Macrophages

Phagocytic immune cells located in the lungs that destroy pathogens via phagocytosis, form phagolysosomes, and aid in tissue repair.

Neuroglia

Non-neuronal support cells of the nervous system that provide structural support, supply nutrients, regulate signal transmission, and repair neural damage.

Apical Modification

Cellular adaptations located on the top surface of epithelial cells facing a lumen or external environment, specialized for secretion, absorption, or movement.

Plasmodesmata

Microscopic channels traversing plant cell walls that connect adjacent cytoplasm to allow direct intercellular transport and communication.

Casparian Strip

A basal band of cell wall material in plant roots that acts as a impermeable barrier regulating water and mineral passage into vascular tissue.

Totipotent Stem Cells

Stem cells with the highest differentiation potency (e.g., morula stage), capable of giving rise to all cell types of the body plus extraembryonic tissues like the placenta.

Pluripotent Stem Cells

Stem cells derived from the inner cell mass of blastocysts that can differentiate into any body cell type from the three germ layers, excluding extraembryonic tissues.

Apical Meristem

Unspecialized plant tissue located at the tips of roots and shoots responsible for primary growth, or increase in length.

Lateral Meristem

Unspecialized plant tissue extending along the sides of stems and roots that drives secondary growth, increasing girth or thickness.

Homeostasis

The steady-state physiological condition where a cell or organism maintains a stable internal environment despite surrounding fluctuations.

G0 Phase

A non-dividing, quiescent or senescent resting stage entered from the $G_1$ phase where cells remain metabolically active but cease division.

G1 Checkpoint

A critical control point in the cell cycle located between $G_1$ and S phase that assesses cell size, energy reserves, growth factors, and DNA integrity.

G2 Checkpoint

A cell cycle checkpoint between $G_2$ and M phase that ensures complete and error-free DNA replication prior to nuclear division.

Spindle Checkpoint

A metaphase cell cycle checkpoint that verifies all sister chromatids are correctly attached to spindle microtubules at the metaphase plate before separation.

Cyclin-Dependent Kinases (CDKs)

Protein kinase enzymes whose activity fluctuates based on cyclin binding, regulating cell cycle progression through target protein phosphorylation.

Maturation-Promoting Factor (MPF)

An active protein complex consisting of a cyclin bound to a CDK that triggers entry into mitosis by driving chromosome condensation and nuclear envelope breakdown.

Sister Chromatids

Two identical copies of a duplicated chromosome produced during S phase and joined together at the centromere.

Kinetochore

A specialized multiprotein complex located on the centromere where spindle microtubules attach during cell division.

Prophase

The first phase of mitosis, characterized by chromatin condensation into visible chromosomes, nucleolus disappearance, breakdown of the nuclear envelope, and spindle assembly.

Anaphase

The shortest phase of mitosis, during which centromeres split and sister chromatids are pulled apart to opposite poles of the cell.

Cleavage Furrow

A contractile ring of microfilaments (actin) formed during animal cell cytokinesis that pinches the cell membrane inward to divide the cytoplasm.

Cell Plate

A structure formed in dividing plant cells during cytokinesis by the fusion of Golgi-derived vesicles along the equatorial plane, leading to a new cell wall.

Phospholipid Bilayer

A double-layered membrane composed of amphipathic phospholipids with hydrophilic heads facing aqueous environments and hydrophobic tails facing inward.

Cis Double Bond

A carbon-carbon double bond in a fatty acid tail that creates a structural kink, preventing tight phospholipid packing and enhancing membrane fluidity.

Cholesterol

A steroid lipid embedded within the cell membrane that acts as a fluidity buffer, stabilizing fluidity at high temperatures and preventing rigidity at low temperatures.

Integral Protein

A membrane protein permanently attached or embedded within the hydrophobic core of the phospholipid bilayer.

Carrier Protein

A transmembrane protein that selectively binds a target molecule and undergoes a conformational shape change to transport it across the membrane.

Channel Protein

A transmembrane protein containing a hydrophilic channel that allows specific ions or polar molecules to pass through down their concentration gradient.

Simple Diffusion

The passive net movement of small, nonpolar solute molecules directly across the phospholipid bilayer from an area of higher to lower concentration.

Osmosis

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

Hypertonic Solution

A surrounding solution with a higher non-penetrating solute concentration than the cell cytoplasm, causing water exit and cell shrinkage.

Hypotonic Solution

A surrounding solution with a lower non-penetrating solute concentration than the cell cytoplasm, causing water influx and cell swelling.

Facilitated Diffusion

Passive transport of polar or charged substances across a membrane down their concentration gradient with the aid of specific transmembrane channel or carrier proteins.

Active Transport

The energy-requiring (ATP-dependent) movement of a solute across a cell membrane against its concentration gradient, from low to high concentration.

Sodium-Potassium Pump

A primary active transport membrane pump that hydrolyzes 1 ATP molecule to export 3 $Na^+$ ions and import 2 $K^+$ ions against their respective electrochemical gradients.

Phagocytosis

A form of endocytosis ('cellular eating') in which a cell engulfs large particles, microorganisms, or cellular debris via pseudopods to form a vacuole.

Pinocytosis

A type of endocytosis ('cellular drinking') where the cell unspecifically fluidizes small invaginations to absorb droplets of extracellular fluid and dissolved solutes.

Receptor-Mediated Endocytosis

A highly selective mode of endocytosis where specific cell-surface receptor proteins bind ligand molecules prior to vesicle internalization.

Exocytosis

The energy-consuming process by which cellular contents stored in secretory vesicles are released outside the cell via vesicle fusion with the plasma membrane.

Apoenzyme

The inactive protein component of an enzyme that requires a non-protein cofactor or coenzyme to become catalytically functional.

Holoenzyme

The complete, catalytically active enzyme structure consisting of an apoenzyme combined with its necessary cofactor or coenzyme.

Active Site

The specific microenvironment or pocket on an enzyme where substrate binding and catalytic bond-cleavage or bond-formation take place.

Allosteric Site

A binding site on an enzyme distinct from the active site, where non-substrate regulatory molecules bind to alter the enzyme's conformation and catalytic rate.

Activation Energy ($E_a$)

The minimum energy threshold required to break initial chemical bonds and initiate a chemical reaction, which is lowered in enzyme-catalyzed pathways.

Induced-Fit Model

The refined concept of enzyme action stating that substrate binding induces a dynamic structural shift in the active site to enhance chemical conversion.

Vmax

The maximum initial velocity of an enzyme-catalyzed reaction attained when all available active sites are fully saturated with substrate.

Km (Michaelis Constant)

The substrate concentration at which the reaction velocity reaches half of $V_{max}$, serving as an inverse measure of the enzyme's affinity for its substrate.

Oxidation

The chemical loss of electrons from a molecule, atom, or ion, accompanied by an increase in oxidation state.

Reduction

The chemical gain of electrons by a molecule, atom, or ion, accompanied by a decrease in oxidation state.

Oxidizing Agent

The electron acceptor in a redox reaction that induces the oxidation of another compound while itself becoming reduced.

Reducing Agent

The electron donor in a redox reaction that induces the reduction of another compound while itself becoming oxidized.

Oxidoreductase

An enzyme class that catalyzes biological oxidation-reduction reactions by facilitating the transfer of electrons, hydrogen atoms, or oxygen.

RuBisCO

Ribulose-1,5-bisphosphate carboxylase/oxygenase; the essential Calvin cycle enzyme in $C_3$ plants that fixes atmospheric $CO_2$ into organic compounds.

Oxidative Stress

A physiological imbalance caused by excessive reactive oxygen species (ROS) production exceeding cellular antioxidant neutralization capacity, causing macromolecular damage.