Chapter 3: Cell Theory, Structure of a Cell Membrane, and Membrane Transport

Vocabulary flashcards covering cell theory, microscopy techniques, prokaryotic vs. eukaryotic cell characteristics, membrane lipids, membrane fluidity, cholesterol, and membrane proteins based on lecture notes.

Atom

The smallest unit of matter that still retains the unique properties of its chemical element.

Radioactive Isotopes

Isotopes with an unstable nucleus that decays spontaneously, releasing subatomic particles and energy.

Electronegativity

An atom's measure of attraction for electrons in a chemical bond, which depends on its atomic number and the distance of valence electrons from the nucleus.

Cell Theory

The foundational principle of biology stating that: 1. All organisms are made up of cells; 2. The cell is the fundamental unit of life; and 3. Cells come from pre-existing cells.

Light Microscopy

A technique using light and glass lenses to observe living samples with magnifications greater than $1000\times$ and an optical resolution limit of $200\,\text{nm}$.

Electron Microscopy

A high-power visualization technique using electron beams to examine dead, prepared samples with a minimum resolution limit of $1\,\text{angstrom}$ ($0.1\,\text{nm}$).

Confocal Microscopy

A type of light microscopy that uses lasers to scan fluorescently stained specimens point-by-point in a very narrow focal plane, creating sharp computer-reconstructed images.

Microvilli

Thin, comblike projections of the cell membrane on intestinal cells that increase absorptive surface area.

Prokaryotic Cell

A cell that lacks a nucleus and membrane-bound organelles, typically small ($1\text{--}2\,\mu\text{m}$ in size), with its genetic material located in an unenclosed nucleoid region.

Eukaryotic Cell

A cell containing a membrane-bound nucleus and internal membrane-bound organelles, typically larger in size ($10\text{--}20\,\mu\text{m}$).

Nucleoid

The irregularly shaped, non-membrane-enclosed region within a prokaryotic cell where the cell's genetic material (DNA) is located.

Amphipathic

Describing a molecule containing both hydrophobic (nonpolar) regions and hydrophilic (polar) regions, such as phospholipids and cholesterol.

Micelle

A spherical aggregate formed by phospholipids with large, bulky polar head groups and a single hydrophobic tail when placed in an aqueous environment.

Liposome

A spherical, closed lipid bilayer surrounding an inner aqueous space, formed spontaneously by phospholipids in water to shield hydrophobic tails from water contact.

Fluid Mosaic Model

The model describing biological membranes as dynamic structures where lipids and proteins form a mosaic and can move laterally within the lipid bilayer plane.

Saturated Fatty Acid

A fatty acid chain lacking double carbon bonds, resulting in a straight structure that packs tightly, increases melting temperature, and decreases membrane fluidity.

Unsaturated Fatty Acid

A fatty acid chain containing one or more double carbon bonds that introduce kinks, reducing tight packing and increasing membrane fluidity at lower temperatures.

Cholesterol

An amphipathic lipid present in animal cell membranes that acts as a fluidity buffer, preventing extreme fluidity at high temperatures and preventing excessive rigidity at low temperatures.

Transporter Protein

A membrane protein that facilitates the movement of ions and molecules across the lipid bilayer.

Receptor Protein

A membrane protein that binds extracellular chemical signals, allowing the cell to sense and respond to its environment.

Integral Membrane Protein

A protein permanently associated with the cell membrane, which cannot be removed without disrupting the lipid bilayer structure.

Peripheral Membrane Protein

A protein temporarily associated with either the internal or external surface of the cell membrane through non-covalent interactions.

Transmembrane Protein

A specific type of integral membrane protein that spans the entire lipid bilayer, with regions exposed on both sides of the membrane.

Photobleaching (FRAP)

An experimental technique in which a laser bleaches a region of fluorescently tagged membrane molecules; the return of fluorescence demonstrates lateral movement of proteins within the fluid membrane.