Principles of Anatomy and Physiology - Chapter 3: The Cellular Level of Organization

Comprehensive vocabulary flashcards covering key terms and concepts from Chapter 3: The Cellular Level of Organization, including cellular structure, plasma membrane transport, organelles, protein synthesis, and cell division.

Plasma Membrane

A flexible yet sturdy lipid bilayer studded with proteins that surrounds and contains the cytoplasm of a cell, regulating the entry and exit of substances.

Cytoplasm

All cellular contents located between the plasma membrane and the nucleus, consisting of two components: cytosol and organelles.

Cytosol

The fluid portion of the cytoplasm (also known as intracellular fluid) composed of water, solutes, suspended particles, lipid droplets, and glycogen granules, serving as the site for many metabolic reactions.

Organelles

Specialized structures within a cell with characteristic shapes that perform specific functional roles in cellular growth, maintenance, and reproduction.

Nucleus

Large organelle consisting of a nuclear envelope with pores, nucleoli, and chromatin; contains genes that control cellular structure and direct cellular activities.

Integral Proteins

Membrane proteins that extend into or through the lipid bilayer; most are transmembrane proteins that span the entire membrane.

Peripheral Proteins

Membrane proteins attached loosely to the inner or outer surface of the membrane or to integral proteins, but not embedded in the lipid bilayer.

Concentration Gradient

The difference in the concentration of a chemical substance between one side of the plasma membrane and the other.

Electrical Gradient

The difference in electrical charge (concentration of ions) between one side of the plasma membrane and the other.

Electrochemical Gradient

The combined influence of a chemical's concentration gradient and electrical gradient on its movement across the plasma membrane.

Simple Diffusion

A passive transport process in which nonpolar, hydrophobic solutes move down their concentration gradient through the lipid bilayer without membrane transport proteins.

Facilitated Diffusion

A passive transport process in which polar or charged solutes move down their concentration gradient through the lipid bilayer via transmembrane channels or carriers.

Osmosis

The passive net movement of solvent (water) across a selectively permeable membrane from an area of higher water concentration to lower water concentration until equilibrium is reached.

Tonicity

A measure of a solution's ability to change the volume of body cells by altering their water content through osmosis.

Hemolysis

The swelling and rupture of red blood cells caused by the osmotic influx of water when placed in a hypotonic solution.

Crenation

The shrinkage of red blood cells caused by the osmotic movement of water out of the cells when placed in a hypertonic solution.

Primary Active Transport

An active process in which energy derived from the hydrolysis of ATP is directly used by a carrier protein (pump) to move a substance across the membrane against its concentration gradient.

Secondary Active Transport

Coupled transport process in which the movement of $\text{Na}^+$ or $\text{H}^+$ down its electrochemical gradient drives another substance across the membrane against its own concentration gradient.

Antiporters

Transporters in secondary active transport that move $\text{Na}^+$ (or $\text{H}^+$) across the membrane in one direction while moving another substance in the opposite direction.

Symporters

Transporters in secondary active transport that move $\text{Na}^+$ (or $\text{H}^+$) and another substance in the same direction across the membrane.

Receptor-Mediated Endocytosis

A selective vesicular transport process where ligand-receptor complexes trigger the infolding of clathrin-coated pits to take specific ligands into the cell.

Phagocytosis

A form of endocytosis ('cell eating') in which large solid particles, such as bacteria or cell debris, are engulfed by pseudopods to form a phagosome.

Bulk-Phase Endocytosis

A form of endocytosis ('cell drinking' or pinocytosis) involving the nonselective uptake of extracellular fluid and dissolved solutes into a vesicle.

Exocytosis

An active transport process in which membrane-enclosed secretory vesicles fuse with the plasma membrane to release their contents into the extracellular fluid.

Transcytosis

An active process that moves a substance entirely across a cell, combining endocytosis on one side with exocytosis on the opposite side.

Cytoskeleton

A network of protein filaments—microfilaments, intermediate filaments, and microtubules—that maintains cell shape, organizes contents, and directs cell movements.

Centrosome

An organelle consisting of a pair of centrioles and pericentriolar matrix, which contains tubulins used for microtubule formation and mitotic spindle assembly.

Cilia

Short, hair-like motile projections containing 20 microtubules that sweep fluids across the cell's surface.

Flagella

Long, whip-like motile projections containing 20 microtubules that move an entire cell through its environment, such as a sperm cell.

Ribosome

An organelle composed of two subunits containing ribosomal RNA and proteins, serving as the physical site of protein synthesis.

Rough Endoplasmic Reticulum

A membranous network of flattened sacs covered with ribosomes; synthesizes glycoproteins and phospholipids for organelles, plasma membrane, or secretion.

Smooth Endoplasmic Reticulum

A membranous network lacking ribosomes; synthesizes fatty acids and steroids, detoxifies drugs, removes phosphate from glucose-6-phosphate, and stores/releases calcium ions in muscle cells.

Golgi Complex

An organelle composed of 3 to 20 flattened membranous sacs (cisternae) divided into entry (cis), medial, and exit (trans) regions; modifies, sorts, packages, and transports proteins from the rough ER.

Lysosome

A membrane-enclosed vesicle containing digestive enzymes that break down endocytosed contents, worn-out organelles (autophagy), or whole cells (autolysis).

Peroxisome

A small vesicle containing oxidases and catalase that oxidizes organic substances like fatty acids and detoxifies harmful metabolic byproducts like hydrogen peroxide.

Proteasome

A tiny barrel-shaped structure containing proteases that degrades unneeded, damaged, or faulty proteins into small peptides.

Mitochondrion

An organelle consisting of external and internal membranes, cristae, and matrix; site of aerobic cellular respiration producing most ATP, and plays a role in apoptosis.

Transcription

The process occurring in the nucleus where genetic information in DNA is copied onto a strand of RNA to direct protein synthesis.

Translation

The process occurring in the cytoplasm/ribosome where the nucleotide sequence of mRNA is read to assemble a specific amino acid sequence into a protein.

Interphase

The period of the somatic cell cycle between cell divisions during which the cell grows, performs metabolic activities, and replicates its DNA ($\text{G}_1$, $\text{S}$, and $\text{G}_2$ phases).

$\text{G}_1$ Phase

The stage of interphase in which the cell is metabolically active, duplicates most of its organelles and cytosolic components, and begins chromosome replication.

$\text{S}$ Phase

The stage of interphase lasting about 8 hours during which DNA and centrosomes are replicated.

$\text{G}_2$ Phase

The stage of interphase lasting 4 to 6 hours during which cell growth continues, enzymes and proteins are synthesized, and centrosome replication is completed.

Mitosis

Nuclear division in somatic cells that results in the distribution of two identical sets of chromosomes into two separate nuclei.

Prophase

The first phase of mitosis in which chromatin fibers condense into visible paired chromatids, the nucleolus and nuclear envelope disappear, and centrosomes move to opposite cell poles.

Metaphase

The stage of mitosis in which centromeres of chromatid pairs align along the metaphase plate in the center of the cell.

Anaphase

The stage of mitosis in which centromeres split and identical sister chromatids separate, moving toward opposite poles of the cell.

Telophase

The final stage of mitosis in which nuclear envelopes and nucleoli reappear, chromosomes uncoil into chromatin, and the mitotic spindle dissolves.

Cytokinesis

The division of the parent cell's cytoplasm where a contractile ring forms a cleavage furrow, splitting the cytoplasm into two equal portions.

Meiosis

Reproductive cell division in the gonads that produces gametes with a haploid ($n$) number of chromosomes through two successive nuclear divisions.

Synapsis

The pairing of homologous chromosomes during prophase I of meiosis to form tetrads, enabling crossing-over between nonsister chromatids.