Introductory Biology I – Chapter 6: A Tour of the Cell

Vocabulary flashcards covering key terms from Chapter 6 lecture on cell structure, microscopy, organelles, and cellular components.

Cell Theory

States that (1) all organisms are composed of one or more cells, (2) the cell is the smallest living unit, and (3) all cells arise from pre-existing cells by division.

Magnification

Microscopy parameter describing the ratio of an object’s image size to its real size; LMs can magnify up to about 1,000×.

Resolution

The clarity of an image; the minimum distance at which two points can be distinguished as separate (≈200 nm for light microscopes).

Contrast

Microscopy parameter that accentuates differences in parts of a sample; often improved by staining or labeling.

Light Microscope (LM)

Instrument that passes visible light through a specimen and glass lenses to produce a magnified image of living or fixed cells.

Scanning Electron Microscope (SEM)

Electron microscope that scans a beam over the surface of a specimen to create detailed 3-D images.

Transmission Electron Microscope (TEM)

Electron microscope that passes electrons through a thin specimen to reveal internal ultrastructure.

Cell Fractionation

Laboratory technique that separates cell components by differential centrifugation to study organelle function.

Organelle

A membrane-bound structure with specialized functions within eukaryotic cells (e.g., mitochondrion, lysosome).

Prokaryotic Cell

Cell lacking a nucleus and membrane-bound organelles; DNA resides in an unbounded region called the nucleoid.

Eukaryotic Cell

Cell with a true nucleus enclosed by a nuclear envelope and numerous membrane-bound organelles.

Plasma Membrane

Selective phospholipid bilayer that encloses the cell, regulating passage of substances in and out.

Cytosol

The semifluid, jelly-like portion of the cytoplasm in which organelles reside.

Nucleus

Double-membrane organelle housing chromatin; contains nucleoli for ribosome assembly and pores for molecular traffic.

Chromatin

Complex of DNA and proteins that condenses to form chromosomes during cell division.

Ribosome

Particle of rRNA and protein that carries out protein synthesis; can be free in cytosol or bound to rough ER.

Endomembrane System

Interconnected network including nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles, and plasma membrane that traffics proteins and lipids via vesicles.

Smooth Endoplasmic Reticulum (Smooth ER)

ER region lacking ribosomes; synthesizes lipids, metabolizes carbohydrates, detoxifies drugs, and stores Ca²⁺.

Rough Endoplasmic Reticulum (Rough ER)

ER studded with bound ribosomes; synthesizes secretory proteins, forms glycoproteins, and generates membrane.

Golgi Apparatus

Stack of flattened cisternae that modifies, sorts, and packages ER products into vesicles; has cis (receiving) and trans (shipping) faces.

Lysosome

Acidic, enzyme-filled vesicle in animal cells that hydrolyzes macromolecules and recycles damaged organelles (autophagy).

Vacuole

Large membrane-bounded vesicle; types include food vacuoles (phagocytosis), contractile vacuoles (pump excess water), and central vacuoles (plant storage).

Mitochondrion

Double-membrane organelle with cristae and matrix that performs cellular respiration to generate ATP.

Chloroplast

Photosynthetic organelle in plants/algae containing thylakoids and stroma; converts light energy to chemical energy.

Endosymbiotic Theory

Proposes mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral eukaryotic cells.

Peroxisome

Single-membrane compartment that contains enzymes transferring H to O₂, forming and then detoxifying H₂O₂.

Cytoskeleton

Network of protein fibers (microtubules, microfilaments, intermediate filaments) that supports cell shape, organizes organelles, and drives movement.

Microtubule

25 nm hollow tubes of α- and β-tubulin; resist compression, form tracks for organelle movement, and make up cilia, flagella, and the mitotic spindle.

Centrosome

Microtubule-organizing center in animal cells containing a pair of centrioles.

Cilia

Short, numerous, microtubule-based extensions that move fluid across cell surfaces with a coordinated stroke.

Flagellum

Long, usually single, microtubule-based appendage that propels cells with a whip-like motion.

Microfilament (Actin Filament)

7 nm strands of actin; bear tension, enable muscle contraction, cytoplasmic streaming, and amoeboid movement.

Intermediate Filament

8–12 nm fibrous proteins (e.g., keratin) that provide mechanical strength and anchor organelles; form nuclear lamina.

Cell Wall

Rigid extracellular layer of cellulose (plants) that protects, maintains shape, and prevents excess water uptake.

Extracellular Matrix (ECM)

Animal-cell network of glycoproteins (e.g., collagen, fibronectin) and proteoglycans that supports, adheres, and signals.

Plasmodesmata

Channels in plant cell walls that connect cytoplasm of adjacent cells for substance exchange.

Tight Junction

Animal-cell junction where membranes press together to prevent leakage between cells (e.g., intestinal lining).

Desmosome

Anchoring junction fastening cells via intermediate filaments; provides mechanical strength (e.g., muscle tissue).

Gap Junction

Animal-cell channel allowing ions and small molecules to pass for cell-to-cell communication.

Surface Area–to–Volume Ratio

Relationship that limits cell size; smaller cells have higher ratios, enhancing material exchange efficiency.

Seven Characteristics of Life

Traits shared by living organisms: cellular organization/DNA, response to stimuli, homeostasis, metabolism, growth & development, reproduction, evolution/adaptation.