Chapter 3: Cells - Structure, Function, and Cell Cycle

A collection of vocabulary flashcards covering key cellular structures, organelles, transport mechanisms, the cell cycle, and cellular differentiation based on Chapter 3 lecture notes.

Differentiated Cell

A cell that has developed specialized characteristics, with structures adapted to perform specific functions in the body.

Composite Cell

A generalized cell model showing the major components and organelles common to most cells, including the nucleus, cytoplasm, and cell membrane.

Cytosol

The liquid portion of the cytoplasm in which organelles and other cellular components are suspended.

Cell Membrane (Plasma Membrane)

The outer boundary of a cell that maintains cell integrity, separates intracellular fluid from extracellular fluid, and regulates the entry and exit of substances.

Phospholipid Bilayer

The structural framework of the cell membrane consisting of hydrophilic (water-soluble) heads forming the outer surfaces and hydrophobic (water-insoluble) tails forming the interior.

Cellular Adhesion Molecules (CAMs)

Membrane proteins, such as selectins and integrins, that guide migrating cells and enable cells to stick to each other or attach to capillary walls.

Ribosomes

Organelles composed of protein and RNA that provide structural support and enzymatic activity to link amino acids during protein synthesis.

Endoplasmic Reticulum (ER)

A complex network of membrane-bound sacs, canals, and vesicles that functions as a tubular transport system within the cell.

Rough Endoplasmic Reticulum (RER)

A region of endoplasmic reticulum studded with ribosomes on its outer surface, primarily involved in protein synthesis and processing.

Smooth Endoplasmic Reticulum (SER)

A region of endoplasmic reticulum lacking ribosomes that conducts lipid synthesis and metabolism.

Golgi Apparatus

An organelle composed of flattened membranous sacs that refines, packages, and delivers proteins synthesized on the rough ER.

Mitochondrion

A membrane-bound organelle containing matrix and cristae that carries out cellular respiration to extract energy from nutrients and generate $ATP$.

Lysosome

A membranous sac containing digestive enzymes that degrade proteins, carbohydrates, nucleic acids, foreign debris, and worn-out cell parts.

Peroxisomes

Membranous sacs containing enzymes that breakdown lipids, alcohol, and hydrogen peroxide.

Microfilaments

Tiny cytoskeletal rods composed of actin protein that enable cellular movements, such as muscle contraction.

Microtubules

Tubes composed of tubulin protein that maintain cell shape, move organelles, and form cilia, flagella, and centrioles.

Cytoskeleton

A structural framework inside the cytoplasm formed by a network of microfilaments, microtubules, and intermediate filaments.

Centrosome

A structure located in the cytoplasm near the nucleus consisting of two cylindrical centrioles that form spindle fibers during cell division.

Cilia

Short, motile hair-like extensions of the cell membrane composed of microtubules that beat in a coordinated manner to move materials across the cell surface.

Flagellum

A long motile projection of the cell membrane, structurally similar to cilia, that propels an entire cell (e.g., the tail of a sperm cell).

Microvilli

Tiny extensions of the cell membrane supported by actin filaments that increase surface area for absorption.

Cell Nucleus

The organelle containing genetic material (DNA) that directs cell activities, enclosed by a nuclear envelope with nuclear pores.

Nucleolus

A dense body of RNA and protein inside the cell nucleus where ribosomes are produced.

Chromatin

Fibers of DNA wound around proteins located in the nucleoplasm that carry instructions for protein synthesis.

Diffusion

The passive movement of atoms, molecules, or ions from a region of higher concentration to a region of lower concentration due to molecular motion.

Facilitated Diffusion

Passive transport of water-soluble substances across the cell membrane down a concentration gradient using ion channels or carrier proteins without using $ATP$.

Osmosis

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

Isotonic Solution

A solution that has the same osmotic pressure as intracellular fluid, causing no net movement of water into or out of the cell.

Hypertonic Solution

A solution with higher osmotic pressure than intracellular fluid, causing water to leave the cell and leading to cell shrinkage (crenation).

Hypotonic Solution

A solution with lower osmotic pressure than intracellular fluid, causing water to enter the cell and leading to swelling or lysis.

Filtration

A passive process in which hydrostatic or blood pressure forces molecules through a membrane to separate smaller molecules from larger ones.

Active Transport

The process that moves substances across a cell membrane against a concentration gradient using carrier proteins and $ATP$ energy.

Secondary Active Transport

A mechanism where a carrier protein uses an established ion concentration gradient (such as $\text{Na}^+$) to transport another substance across a membrane without consuming $ATP$ directly.

Pinocytosis

A type of endocytosis where the cell membrane indents and engulfs tiny droplets of extracellular fluid within a vesicle.

Phagocytosis

A type of endocytosis where the cell membrane engulfs solid particles into a vesicle for intracellular digestion.

Receptor-Mediated Endocytosis

A specific endocytosis process where target ligands bind to specific receptor proteins on the cell membrane before being internalized inside a vesicle.

Exocytosis

The process in which intracellular vesicles fuse with the cell membrane to release their contents outside the cell.

Transcytosis

A transport process combining receptor-mediated endocytosis followed by exocytosis to transport substances across a barrier formed by tightly connected cells.

Interphase

The active phase of the cell cycle comprising $G_1$, $S$, and $G_2$ phases, during which the cell grows, performs normal functions, and replicates DNA and organelles in preparation for division.

Mitosis

The division of the somatic cell nucleus consisting of prophase, metaphase, anaphase, and telophase to produce two identical nuclei.

Cytokinesis

The division of the cytoplasm during cell division via a cleavage furrow created by a contractile ring of actin filaments.

Telomeres

Structures located at chromosome tips that shorten with each round of mitosis, functioning as a biological mitotic clock.

Oncogenes

Abnormal or overexpressed forms of regulatory genes that accelerate cell division and can induce tumor development.

Tumor Suppressor Genes

Genes that normally limit cell division; their inactivation or mutation removes controls on mitosis, predisposing cells to cancer.

Stem Cell

An undifferentiated cell capable of self-renewal through cell division or producing a specialized progenitor cell.

Progenitor Cell

A partially specialized daughter cell of a stem cell that is restricted to developing into a limited number of cell types.

Totipotent

Describing cells (such as a fertilized egg) that possess the developmental potential to differentiate into any cell type.

Pluripotent

Describing stem or progenitor cells capable of differentiating into a restricted, specific range of cell types.

Apoptosis

Programmed, stepwise cell death that removes unnecessary or damaged cells as a normal part of development and homeostasis.

Necrosis

Unregulated cell death caused by direct physical injury or pathological damage.