Cellular Form and Function

Comprehensive vocabulary flashcards covering cellular form, membrane structure, transport mechanisms, and intracellular organelles based on Chapter 3 lecture notes.

Cytology

The scientific study of cells, which began when Robert Hooke observed the empty cell walls of cork.

Robert Hooke

The English scientist who coined the term cellulae to describe the empty cell walls of cork, founding the field of cytology.

Theodor Schwann

The scientist who concluded, approximately two centuries after Hooke, that all animal tissues are composed of cells.

Louis Pasteur

The scientist who established beyond reasonable doubt that 'cells arise only from other cells,' definitively refuting spontaneous generation.

Spontaneous Generation

The refuted concept that living organisms arise spontaneously from nonliving matter.

Modern Cell Theory

The biological principle stating that all organisms consist of cells and cell products, the cell is the simplest structural and functional unit of life, organismal activities depend on cellular activities, cells arise only from preexisting cells, and cells share fundamental similarities in chemical composition and metabolism.

Cytoplasm

The fluid and cellular contents located between the nucleus and the surface plasma membrane.

Cytosol (Intracellular Fluid, ICF)

The clear, intracellular fluid in which organelles and the cytoskeleton are suspended.

Extracellular Fluid (ECF)

Any body fluid located outside the plasma membrane of a cell.

Plasma Membrane

A unit membrane composed of lipids and proteins that defines cell boundaries, controls the passage of materials, and governs interactions with other cells.

Phospholipids (Membrane)

Amphiphilic molecules making up $75\%$ of plasma membrane lipids, arranged in a bilayer with hydrophilic phosphate heads exposed to water and hydrophobic tails directed toward the center.

Cholesterol (Membrane)

A lipid comprising $20\%$ of membrane lipids that fits between phospholipids to stiffen the membrane and regulate fluidity.

Glycolipids

Phospholipids with short carbohydrate chains situated on the extracellular face, making up $5\%$ of membrane lipids and contributing to the glycocalyx.

Transmembrane Proteins

Membrane proteins that span completely through the phospholipid bilayer, possessing both hydrophilic and hydrophobic regions.

Peripheral Proteins

Membrane proteins that do not penetrate the phospholipid bilayer but adhere to one face of the membrane, often anchored to transmembrane proteins or the cytoskeleton.

Glycocalyx

A unique, fuzzy carbohydrate coating external to the plasma membrane formed by glycoproteins and glycolipids that functions in cell protection, immunity, adhesion, and identification.

Microvilli

Plasma membrane extensions ($1\text{--}2\,\mu\text{m}$ long) supported by actin filaments that increase an absorptive cell's surface area by $15$ to $40$ times.

Brush Border

A dense, fringe-like surface array of microvilli found on cells specialized for absorption.

Cilia

Hairlike processes ($7\text{--}10\,\mu\text{m}$ long); nonmotile types act as sensory antennae, while motile types use power and recovery strokes to sweep substances across epithelial surfaces.

Cystic Fibrosis

A hereditary disorder in which cells fail to install chloride pumps in the plasma membrane, causing thick mucus to block pancreatic ducts and respiratory tracts, leading to chronic infections and an average life expectancy of $30$ years.

Flagellum

A long, whiplike process with an axoneme identical to a cilium, found on human sperm, which moves with an undulating, snakelike motion without power and recovery strokes.

Simple Diffusion

The net movement of particles from an area of higher concentration to an area of lower concentration driven by spontaneous particle motion.

Osmosis

The flow of water across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.

Osmotic Pressure

The exact amount of hydrostatic pressure required to prevent the osmotic flow of water across a membrane.

Reverse Osmosis

A process where external mechanical pressure overrides osmotic pressure to drive water against its concentration gradient, such as capillary filtration driven by the heart.

Hypotonic Solution

A solution that has a lower concentration of nonpermeating solutes than the intracellular fluid, causing cells to absorb water, swell, and potentially lyse.

Hypertonic Solution

A solution that has a higher concentration of nonpermeating solutes than the intracellular fluid, causing cells to lose water and crenate (shrivel).

Isotonic Solution

A solution with a nonpermeating solute concentration equal to that of the intracellular fluid, producing no net change in cell volume or shape.

Sodium-Potassium Pump ($\text{Na}^+\text{--}\text{K}^+$ Pump)

A transmembrane active-transport mechanism that consumes one $\text{ATP}$ to export three $\text{Na}^+$ ions and import two $\text{K}^+$ ions, consuming approximately half of daily caloric intake.

Endocytosis

Vesicular transport mechanisms that bring matter, fluid droplets, or large molecules into a cell via membrane enclosures.

Phagocytosis

A form of endocytosis ('cell eating') in which pseudopods engulf large particles such as bacteria or cellular debris to form a phagosome.

Pinocytosis

A form of endocytosis ('cell drinking') in which the plasma membrane invaginates to take in droplets of extracellular fluid containing molecules useful to the cell.

Exocytosis

A vesicular transport process in which secretory vesicles fuse with the plasma membrane to release material from the cell, energized by $\text{ATP}$.

Cytoskeleton

A network of protein filaments and cylinders that structurally supports the cell, determines its shape, organizes cellular components, and directs intracellular movement.

Microfilaments

Thin cytoskeletal filaments composed of actin that form the terminal web immediately inside the plasma membrane and support microvilli.

Intermediate Filaments

Cytoskeletal protein fibers thicker than microfilaments that provide support, mechanical strength, and structural resistance to physical stress.

Microtubules

Hollow cylinders of tubulin protein that provide tracks for moving organelles, form structural cores in cilia and flagella, and govern cell division.

Nucleus

The largest cellular organelle, surrounded by a double unit membrane, containing chromatin, nucleoplasm, and nucleoli.

Nuclear Envelope

A double unit membrane enclosing the nucleus, perforated by protein-lined nuclear pores that regulate molecular traffic.

Nucleolus

One or more dark-staining masses inside the nucleus responsible for producing ribosomes.

Rough Endoplasmic Reticulum

Parallel, flattened cisternae continuous with the nuclear envelope and studded with ribosomes, responsible for synthesizing membrane phospholipids, membrane proteins, and proteins for secretion or packaging.

Smooth Endoplasmic Reticulum

Branching tubular cisternae lacking ribosomes that synthesize steroids and other lipids, detoxify drugs and alcohol, and manufacture all cell membranes.

Ribosomes

Small granules of protein and RNA found free in the cytosol, in the nucleolus, and on the rough ER and nuclear envelope that read mRNA and synthesize proteins.

Golgi Complex

A stack of flat cisternae that receives newly synthesized proteins from the rough ER, sorts and chemically modifies them, and packages them into membrane-bound Golgi vesicles.

Lysosomes

Membrane-bound packages of hydrolytic digestive enzymes that break down proteins, nucleic acids, carbohydrates, phospholipids, and other cellular substances.

Autophagy

The lysosomal degradation and recycling of worn-out organelles, such as aged mitochondria.

Autolysis

The programmed digestion of surplus or damaged cells by the coordinated release of their own lysosomal enzymes ('cell suicide').

Peroxisomes

Organelles that utilize molecular oxygen to oxidize organic molecules, producing and breaking down hydrogen peroxide ($\text{H}_2\text{O}_2$) via catalase, neutralizing toxins, and processing fatty acids.

Mitochondria

Double-membraned organelles specialized in synthesizing $\text{ATP}$ through aerobic respiration, containing internal folds called cristae and an enzyme-rich matrix.

Cristae

Infoldings of the inner mitochondrial membrane that project into the matrix and house key enzymes for ATP synthesis.

Mitochondrial DNA (mtDNA)

A small circular DNA molecule inside the mitochondrial matrix that replicates independently of nuclear DNA and is inherited almost exclusively through the mother.

Centriole

A short cylindrical organelle composed of nine groups of three microtubules that resides in a perpendicular pair within the centrosome to organize cell division.

Inclusions

Non-essential cellular structures not bound by unit membranes, divided into stored cellular products (glycogen, pigments, fat droplets) and foreign bodies (phagocytized bacteria, viruses, or dust).