Cell Discovery, Structure, and Transport

Comprehensive vocabulary flashcards covering the history of cell theory, microscope technologies, cell structures, organelles, plasma membrane properties, and cellular transport mechanisms.

Cell

The basic structural and functional unit of all living organisms.

Robert Hooke

An English scientist who made a simple microscope in 1665, observed small, box-shaped structures in dead oak bark cork, and named them cellulae (cells).

Anton van Leeuwenhoek

A Dutch scientist who designed his own microscope in the late 1600s and discovered living organisms in pond water, milk, and other substances.

Matthias Schleiden

A German scientist who carefully studied plant tissues in 1838 and concluded that all plants are composed of cells.

Theodor Schwann

A German scientist who reported in 1839 that animal tissues are composed of individual cells.

Rudolph Virchow

A Prussian physician who proposed in 1855 that all cells are produced from the division of existing cells.

Cell Theory

A fundamental idea of modern biology summarizing three principles: (1) all living organisms are composed of one or more cells, (2) cells are the basic unit of structure and organization of all living organisms, and (3) cells arise only from previously existing cells by passing genetic material to daughter cells.

Resolution

The ability of a microscope to make individual components visible clearly.

Transmission Electron Microscope (TEM)

A microscope developed in the 1940s that uses magnets to aim a beam of electrons through thin, dead specimens stained with heavy metals onto a fluorescent screen, magnifying up to $500{,}000\times$.

Scanning Electron Microscope (SEM)

An electron microscope that directs electrons over the surface of a nonliving specimen to produce a three-dimensional image.

Plasma Membrane

A special thin, flexible boundary between a cell and its environment that helps control what enters and leaves the cell.

Organelles

Distinct internal structures within a cell that carry out specific cell functions.

Eukaryotic Cells

Cells that contain a nucleus and other membrane-bound organelles.

Nucleus

A distinct central organelle in eukaryotic cells that contains the cell's genetic material in the form of DNA.

Prokaryotic Cells

Simpler cells defined as lacking a nucleus and other membrane-bound organelles, such as bacteria.

Endosymbiont Theory

The theory that eukaryotic cells evolved from prokaryotic cells millions of years ago through a symbiotic relationship where one prokaryotic cell lived inside another and both benefited.

Homeostasis

The process of maintaining balance in an organism's internal environment.

Selective Permeability

A key property of the plasma membrane by which it allows some substances to pass through while keeping others out.

Phospholipid Bilayer

A structure composed of two layers of phospholipids arranged tail-to-tail, with polar hydrophilic phosphate heads facing water and nonpolar hydrophobic fatty acid tails facing the interior.

Transport Proteins

Proteins that span the entire plasma membrane and move needed substances or waste materials through it, contributing to selective permeability.

Cholesterol (in Plasma Membrane)

A nonpolar molecule positioned among the phospholipids that helps prevent the fatty acid tails from sticking together, contributing to membrane fluidity.

Fluid Mosaic Model

A model describing the plasma membrane as a 'sea' of phospholipids in which proteins and other molecules can float and move sideways in constant motion.

Cytoplasm

The semifluid material environment inside the plasma membrane in which cellular processes take place.

Cytoskeleton

A supporting network of long, thin protein fibers that forms a framework for the cell, anchors organelles, and functions in cell movement.

Microtubules

Long, hollow protein cylinders that form a rigid skeleton for the cell and assist in moving substances within the cell.

Microfilaments

Thin protein threads that help give the cell shape and enable parts of the cell or the entire cell to move.

Endoplasmic Reticulum (ER)

A membrane system of folded sacs and interconnected channels that serves as the site for protein and lipid synthesis.

Rough Endoplasmic Reticulum

The region of the endoplasmic reticulum that is studded with ribosomes and produces proteins intended for export to other cells.

Smooth Endoplasmic Reticulum

The region of the endoplasmic reticulum without ribosomes that synthesizes complex carbohydrates and lipids (including phospholipids) and detoxifies harmful substances in the liver.

Lysosomes

Vesicles containing digestive enzymes that break down excess or worn-out organelles, food particles, and invading bacteria and viruses.

Centrioles

Organelles made of groups of microtubules located near the nucleus in animal cells and most protists that function during cell division.

Golgi Apparatus

A cellular structure that packages proteins into vesicles and transports them to other organelles or out of the cell.

Diffusion

The net movement of particles from an area of higher concentration to an area of lower concentration driven by random motion without additional energy input.

Brownian Motion

The continuous, random motion of particles in solids, liquids, and gases that causes them to collide with each other.

Osmosis

The diffusion of water across a selectively permeable membrane toward the side with the greater solute concentration.

Isotonic Solution

A solution that has the same concentration of water and solutes as the cytoplasm of the cell, resulting in no net movement of water and allowing the cell to retain its normal shape.

Hypotonic Solution

A solution that has a lower solute concentration than the inside of the cell, causing water to enter the cell by osmosis, increasing internal pressure and potentially bursting animal cells.

Hypertonic Solution

A solution with a higher concentration of solute than the inside of the cell, causing net water loss from the cell, which results in shriveling of animal cells and wilting of plant cells.

Active Transport

The movement of substances across the plasma membrane against a concentration gradient (from lower to higher concentration) using carrier proteins (pumps) and cellular energy.

Endocytosis

The process by which a cell surrounds an external substance, encloses it within a portion of the plasma membrane, and pinches off a vacuole inside the cell.

Exocytosis

The secretion or expulsion of materials (such as wastes or hormones) at the plasma membrane by vesicle fusion, requiring energy input.