Cells, Organelles, Hydration, and Electrolyte Balance

Comprehensive vocabulary flashcards covering prokaryotic and eukaryotic cellular structures, organelle functions, and the physiological roles of water and electrolytes in cellular homeostasis.

Cell

The smallest unit of life capable of carrying out all basic processes that keep living organisms alive.

Prokaryotic Cell

A simple, small cell ranging from $0.1\text{ to }5\,\mu\text{m}$ that lacks a membrane-bound nucleus and membrane-bound organelles; examples include bacteria and archaea.

Eukaryotic Cell

A complex, larger cell ranging from $10\text{ to }100\,\mu\text{m}$ containing a membrane-bound nucleus and specialized membrane-bound organelles; found in plants, animals, fungi, and protists.

Nucleoid

The region within the cytoplasm of a prokaryotic cell where genetic material (DNA) floats freely without a membrane barrier.

Compartmentalization

The organization of a eukaryotic cell into distinct, membrane-enclosed spaces or organelles that allow specialized division of labor and efficient regulation.

Organelles

Specialized internal structures within cells that act like organs to perform distinct physiological processes.

Nucleus

The command center of a eukaryotic cell that safely stores DNA, directs cell activities, and initiates protein synthesis by transcribing DNA into messenger RNA ($\text{mRNA}$).

Nuclear Envelope

A double-layered membrane enclosing the nucleus that protects DNA and regulates the passage of materials entering and exiting the nucleus.

Chromatin

The organized combination of DNA and proteins found within the eukaryotic nucleus.

Mitochondria

Double-membrane organelles with cristae that generate ATP through cellular respiration, regulate apoptosis, manage calcium levels, generate heat in brown fat, and facilitate metabolic signaling.

Cellular Respiration

A multi-step metabolic pathway in mitochondria that breaks down glucose and other nutrients in the presence of oxygen to produce ATP.

Apoptosis

Programmed cell death regulated by mitochondria, essential for proper tissue development and disease prevention.

Adenosine Triphosphate (ATP)

The primary energy currency molecule that stores and transfers chemical energy inside biological cells.

Ribosomes

Small, non-membrane-bound structures found in both prokaryotes and eukaryotes that synthesize proteins by translating $\text{mRNA}$ instructions into amino acid sequences.

Rough Endoplasmic Reticulum (RER)

A network of internal membranes studded with ribosomes that modifies, folds, and transports proteins destined for the cell membrane or extracellular secretion.

Smooth Endoplasmic Reticulum (SER)

A membrane network lacking ribosomes that synthesizes lipids (such as fats and hormones) and detoxifies drugs and harmful chemicals, abundantly found in liver cells.

Golgi Apparatus

A stack of flattened membranes that modifies, packages, sorts, and attaches chemical address tags to proteins and lipids received from the endoplasmic reticulum.

Lysosomes

Membrane-bound digestive vesicles primarily in animal cells containing enzymes that break down waste, damaged organelles, cellular debris, and engulfed pathogens.

Tay-Sachs Disease

A genetic disorder characterized by the malfunction of lysosomal enzymes, causing toxic molecule accumulation in nerve cells and damage to the nervous system.

Vacuoles

Membrane-bound storage compartments holding water, ions, nutrients, and waste products to help cells manage their internal environment.

Turgor Pressure

The internal hydrostatic pressure exerted by a fluid-filled central vacuole against the plant cell wall that keeps the plant upright, firm, and structurally supported.

Chloroplasts

Double-membrane organelles containing chlorophyll found in plants and algae that capture solar energy to synthesize glucose via photosynthesis.

Chlorophyll

A green pigment within chloroplasts responsible for capturing light energy necessary to drive photosynthesis.

Endosymbiosis

The biological process by which formerly free-living prokaryotic organisms were engulfed by ancestral host cells and evolved into organelles like chloroplasts and mitochondria.

Cell Membrane

A flexible outer boundary composed of a phospholipid bilayer with embedded proteins that regulates the movement of substances entering and exiting the cell.

Selective Permeability

The property of the cell membrane that allows specific essential substances like nutrients in while blocking harmful compounds and allowing waste elimination.

Cell Wall

A rigid outer protective and structural layer found in plant cells, fungi, and some prokaryotes; composed primarily of cellulose in plants.

Cellulose

A tough structural carbohydrate forming the plant cell wall that prevents bursting and serves as dietary fiber in human nutrition.

Hydration

The balance and availability of fluid within the body, across tissues, organs, and intracellular spaces, making up approximately $60\%$ of average human body mass.

Interstitial Fluid

The fluid located in the spaces between cells that facilitates substance transport and helps maintain tissue pressure.

Electrolytes

Charged ions formed when atoms or molecules gain or lose electrons, enabling the transmission of electrical impulses, muscle contraction, and fluid balance regulation.

Sodium ($\text{Na}^+$)

A major extracellular electrolyte that regulates blood pressure, fluid volume balance, and nerve impulse signaling.

Potassium ($\text{K}^+$)

A key intracellular electrolyte critical for regulating muscle contractions, nerve transmission, and healthy heart rhythm.

Calcium ($\text{Ca}^{2+}$)

An essential electrolyte needed for muscle contraction, bone integrity, and nerve signal transmission.

Magnesium ($\text{Mg}^{2+}$)

An essential electrolyte that stabilizes cell membranes, regulates muscle contraction, and supports over $300$ enzymatic reactions.

Chloride ($\text{Cl}^-$)

A vital negative electrolyte that helps maintain proper fluid balance and acid-base (pH) equilibrium.

Osmosis

The net movement of water molecules across a semi-permeable membrane to balance solute concentrations on either side.

Homeostasis

The maintenance of a stable, healthy, and regulated internal physiological environment necessary for cell survival.

Dehydration

A pathological state occurring when fluid output exceeds fluid input, decreasing blood volume and impairing heart, kidney, and brain function.

Hyponatremia

A dangerous medical condition caused by overhydration where blood sodium concentration becomes critically diluted, causing cellular swelling, confusion, seizures, or coma.

Kidneys

The primary organs of the urinary system that filter blood and regulate body fluid volume and electrolyte concentrations by adjusting the volume and solute concentration of urine.

Diuretics

Substances such as caffeine and alcohol that promote increased urine production, thereby increasing fluid loss from the body.