3. Cell Anatomy and Physiology

Vocabulary practice flashcards covering eukaryotic and prokaryotic cell structures, organelles, cell division phases, passive diffusion, osmosis, tonicity, and active transport systems.

Prokaryote

An organism lacking a true nucleus and organelles, characterized by nuclear material scattered throughout the cytoplasm.

Eukaryote

An organism composed of cells that possess a true nucleus enclosing genetic material, as well as distinct membrane-bound organelles.

Plasma Membrane

The selectively permeable outer barrier of the cell that encloses internal structures and regulates entry and exit between internal and external environments.

Phospholipids (Membrane)

Lipid molecules that make up approximately $75\%$ of the cell membrane's lipid bilayer.

Glycolipids (Membrane)

Lipids with attached carbohydrate chains that constitute approximately $5\%$ of plasma membrane lipids and are located exclusively on the external membrane surface.

Cholesterol (Membrane)

Lipid molecules accounting for approximately $20\%$ of membrane lipids, functioning primarily to provide structural support to the cell membrane.

Amphipathic

Possessing both a hydrophilic (water-loving) polar end and a hydrophobic (water-fearing) nonpolar end, a key chemical property of membrane lipids.

Cilia

Tiny, hair-like external projections that beat rhythmically to move fluids across the outer surface of a cell.

Flagella

Long, whip-like external appendages that propel the cell through surrounding fluid.

Cytosol

The intracellular gel-like fluid of a cell containing dissolved proteins, enzymes, ions, carbohydrates, and small molecules; classified as a colloid solution.

Cytoplasm

The entire cellular content between the plasma membrane and nucleus, comprising the cytosol, inclusions, and organelles (excluding the nucleus and cytoskeleton).

Cytoskeleton

A network of protein filaments (microtubules and microfilaments) in the cytoplasm that provide structural support and assemble or disassemble to alter cell shape and enable sliding movements.

Inclusions

Temporary structures within a cell that serve secretory, storage, or transport roles, including vacuoles, cellular debris, or engulfed bacteria and viruses.

Mitochondria

Self-replicating organelles responsible for cellular respiration and the synthesis of adenosine triphosphate ($\text{ATP}$).

Cristae

The internal folds of the inner mitochondrial membrane that serve as the primary site of $\text{ATP}$ synthesis.

Ribosome

The smallest cellular organelle, composed primarily of ribosomal RNA ($\text{rRNA}$), that translates $\text{mRNA}$ to carry out protein synthesis.

Cisternae

The flattened, membrane-bound sacs and passageways that form the structures of the endoplasmic reticulum and Golgi apparatus.

Rough Endoplasmic Reticulum (RER)

An extensive network of narrow cisternae continuous with the nuclear membrane, studded with attached ribosomes that synthesize proteins for transport.

Smooth Endoplasmic Reticulum (SER)

A network of tubular, short cisternae devoid of ribosomes that synthesizes lipids (fatty acids, phospholipids, steroids) and detoxifies chemical agents in hepatocytes.

Golgi Apparatus

An organelle made of cisternae that receives molecules from the endoplasmic reticulum, processes and repackages them into secretory vesicles, and forms lysosomes.

Lysosome

A digestive vesicle produced by the Golgi apparatus that contains enzymes to degrade macromolecules, engulfed bacteria, food particles, and worn-out organelles.

Autolysis

The programmed self-destruction of a cell triggered when lysosomes rupture and release their hydrolytic digestive enzymes throughout the cytoplasm.

Peroxisome

An organelle derived from the endoplasmic reticulum that uses oxidizing enzymes to detoxify harmful substances, generating and subsequently degrading hydrogen peroxide ($H_2O_2$).

Catalase

An antioxidant enzyme present in peroxisomes that decomposes toxic hydrogen peroxide ($H_2O_2$) into water ($H_2O$) and oxygen ($O_2$).

Centrosome

An organelle containing a pair of cylindrical centrioles made of microtubule triplets that organizes the mitotic spindle during cell division and forms cilia/flagella bases.

Nucleus

The cellular control center enclosed by a double-layered nuclear envelope with pores, containing chromatin (DNA) and nucleoplasm.

Nucleolus

A dense, non-membrane-bound subnuclear region rich in ribosomal RNA ($\text{rRNA}$) that serves as the site of ribosome assembly.

Mitosis

The nuclear division of a somatic parent cell producing two genetically identical daughter cells for growth and tissue repair.

Meiosis

A specialized form of cell division that generates haploid male and female gametes for sexual reproduction.

Interphase

The non-dividing phase of the cell cycle during which the cell grows, performs normal metabolic activities, replicates DNA, and prepares for division.

$G_1$ Phase

The initial growth stage of interphase (lasting $8\text{--}10\,\text{hours}$) where the cell is metabolically active, duplicates organelles, and begins centrosome replication.

S Phase

The interphase synthesis stage (lasting $6\text{--}8\,\text{hours}$) dedicated to replicating nuclear DNA and chromosomes.

$G_2$ Phase

The final stage of interphase (lasting $4\text{--}6\,\text{hours}$) where enzyme and protein synthesis continues and centrosome replication is completed.

$G_0$ Phase

A non-dividing, quiescent state where cells that exit the cell cycle remain indefinitely without undergoing replication.

Prophase

The first phase of mitosis where chromatin condenses into distinct chromosomes, the nuclear envelope disassembles, and centrosomes migrate to opposite poles.

Metaphase

The mitotic phase where chromosomes align along the equatorial plane (metaphase plate) and spindle fibers attach to centromeres.

Anaphase

The mitotic phase characterized by the separation of sister chromatids to opposite poles, cell elongation, and initial cleavage furrow formation.

Telophase

The final stage of mitosis where chromosomes decondense, nuclear envelopes reassemble around separated sets of chromatin, and cleavage furrow deepens.

Cytokinesis

The physical cleavage and partitioning of the cytoplasm via a contractile ring that splits the parent cell into two separate daughter cells.

Intracellular Fluid (ICF)

Fluid found within the interior of cells, consisting primarily of cytosol.

Extracellular Fluid (ECF)

All body fluids situated outside the cells, encompassing interstitial fluid and intravascular plasma.

Interstitial Fluid

A specific component of extracellular fluid occupying the microscopic spaces between tissue cells.

Permeability

The property of a biological membrane that dictates the rate and extent to which gasses, liquids, and dissolved solutes can pass through it.

Diffusion

The passive net movement of solute molecules from a region of higher concentration to a region of lower concentration until uniform equilibrium is established.

Osmosis

The net movement of a solvent (water) across a selectively permeable membrane toward a higher solute concentration to establish proportional equilibrium.

Tonicity

A measure of the osmotic pressure gradient between two solutions separated by a semipermeable membrane, determining the direction of water flow.

Oncotic Pressure

The specific colloid osmotic pressure exerted by large plasma proteins that regulates fluid distribution between intravascular blood and interstitial fluid.

Isotonic Solution

A solution whose solute concentration equals that of the intracellular fluid (e.g., $0.9\%\,NaCl$), causing no net water movement or cell volume change.

Hypertonic Solution

A solution with a higher solute concentration than the intracellular fluid (e.g., $3\%\,NaCl$), prompting water outflow and cellular crenation (shrinkage).

Hypotonic Solution

A solution with a lower solute concentration than the intracellular fluid (e.g., $0.45\%\,NaCl$), promoting water entry that causes cell swelling and potential hemolysis.

Colloid Solution

An intravenous hypertonic fluid containing large particles that cannot cross capillary walls, utilized to draw fluid from interstitial tissues into blood vessels to increase blood pressure.

Active Transport

An energy-dependent transportation mechanism that consumes $\text{ATP}$ to pump solutes against their concentration gradient via specific protein carriers.

Phagocytosis

A form of endocytosis by which specialized cells internalize large, solid particles such as bacteria or cellular debris.

Pinocytosis

A form of endocytosis involving the non-specific uptake of extracellular fluid droplets and dissolved small molecules.

Receptor-Mediated Endocytosis

A highly selective endocytic process where specific ligands (proteins, ions, organic compounds) bind to surface receptors before being internalized in vesicles.