Cell Structure and Function

Comprehensive practice flashcards covering vocabulary terms, key scientists, structures, and processes from Chapter 16: Cell Structure and Function.

Cell

The smallest living unit of any organism and the basic unit of structure and function in living things.

Robert Hooke

An English scientist who, in 1665, observed thin slices of nonliving cork under an early microscope and coined the term "cells" because they resembled a monastery's tiny rooms.

Anton van Leeuwenhoek

A Dutch microscopist who used a single-lens microscope to make the first observations of living microorganisms in pond water and from his own mouth.

Matthias Schleiden

A German botanist who concluded in 1838 that all plants are made of cells.

Theodor Schwann

A German biologist who stated in 1839 that all animals are made of cells.

Rudolf Virchow

A German physician who published the concept in 1855 that new cells can be produced only from the division of existing cells.

Cell Theory

A fundamental biological concept stating that: 1. All living things are made up of cells; 2. Cells are the basic units of structure and function in living things; and 3. New cells are produced from existing cells.

Compound Light Microscope

A microscope that passes light through a specimen and uses two lenses (the objective lens and the ocular lens) to form an image, producing clear images up to a magnification of about $1000\times$.

Objective Lens

The primary lens located directly above the specimen on a light microscope that enlarges the image of the specimen.

Ocular Lens

The eyepiece lens of a compound light microscope that further magnifies the image produced by the objective lens.

Fluorescence

A property of certain dyes that emit light of a particular color when exposed to specific wavelengths of light, used to label and track molecules inside living cells.

Electron Microscope

A microscope that uses beams of electrons focused by magnetic fields rather than light, providing higher resolution than light microscopes and capable of viewing structures as small as 1 billionth of a meter ($10^{-9}\,\text{m}$) in nonliving, preserved samples.

Transmission Electron Microscope (TEM)

An electron microscope that passes electron beams through ultra-thin slices of chemically preserved specimens, producing flat, two-dimensional images of cellular structures and large protein molecules.

Scanning Electron Microscope (SEM)

An electron microscope that scans a pencil-like electron beam across the surface of a specimen, creating detailed three-dimensional images without requiring the sample to be sliced.

Micrograph

A photograph taken of an object viewed through a microscope.

Nucleus

A large membrane-enclosed structure in eukaryotic cells that contains genetic material in the form of DNA and serves as the cell's control center.

Prokaryote

A unicellular organism, such as a bacterium, that lacks a nucleus and does not enclose its genetic material within a membrane.

Eukaryote

An organism whose cells enclose their DNA inside a membrane-bound nucleus; includes unicellular protists as well as multicellular plants, animals, and fungi.

Cyanobacteria

The earliest photosynthetic prokaryotes to appear on Earth nearly 3 billion years ago, which released oxygen into the atmosphere and made plant and animal life possible.

Cytoplasm

The portion of a eukaryotic cell outside the nucleus, or the entire fluid interior of a prokaryotic cell.

Organelle

A specialized sub-cellular structure—literally meaning "little organ"—that carries out specific functions within a eukaryotic cell.

Nuclear Envelope

A double-membrane barrier surrounding the nucleus that is dotted with thousands of nuclear pores.

Nuclear Pores

Openings in the nuclear envelope that permit the bidirectional passage of proteins, RNA, and other molecules between the nucleus and the cytoplasm.

Chromatin

A granular, threadlike complex of DNA bound to proteins spread throughout the nucleus that condenses into visible chromosomes when a cell divides.

Nucleolus

A small, dense region located inside the nucleus where the assembly of ribosomes begins.

Ribosome

A cellular structure composed of RNA and protein found in both prokaryotes and eukaryotes that synthesizes proteins by following instructions coded in DNA.

Endoplasmic Reticulum (ER)

An internal membrane system in eukaryotic cells responsible for synthesizing lipids, membrane components, and proteins destined for export.

Rough Endoplasmic Reticulum (Rough ER)

The portion of the endoplasmic reticulum studded with ribosomes on its surface, where newly synthesized proteins enter to be chemically modified before export or transport to specific cellular destinations.

Smooth Endoplasmic Reticulum (Smooth ER)

The ribosome-free portion of the endoplasmic reticulum that contains specialized collections of enzymes for lipid synthesis, carbohydrate synthesis, and the detoxification of drugs.

Golgi Apparatus

An organelle appearing as a stack of flattened membranes that modifies, sorts, and packages proteins and other materials received from the ER for storage or cellular export.

Vesicle

A small membrane-bound sac that stores and transports materials between organelles, as well as to and from the cell membrane.

Vacuole

A large saclike, membrane-enclosed organelle that stores materials such as water, salts, proteins, and carbohydrates.

Central Vacuole

A single, large liquid-filled vacuole found in plant cells whose fluid pressure increases cell rigidity, enabling plants to support heavy structures like stems and leaves.

Contractile Vacuole

A specialized, star-shaped organelle in freshwater unicellular organisms, such as Paramecium, that rhythmically contracts to pump excess water out of the cell.

Lysosome

An enzyme-filled organelle that breaks down lipids, carbohydrates, and proteins into small usable molecules and disassembles old or worn-out organelles to prevent cellular clutter.

Cytoskeleton

A dynamic network of protein filaments that gives eukaryotic cells their shape and internal organization, helps transport materials, and is involved in cell movement.

Microfilaments

Threadlike cytoskeletal structures made of the protein actin that form flexible frameworks and produce cytoplasmic movements, such as amoeboid crawling.

Actin

The protein that polymerizes into microfilaments within the eukaryotic cytoskeleton.

Microtubules

Hollow cytoskeletal cylinders made of tubulin proteins that maintain cell shape, form the mitotic spindle during cell division, and construct cilia and flagella.

Tubulin

The protein subunit that forms microtubules, centrioles, and the structural core of eukaryotic cilia and flagella.

Centrioles

Paired organelles formed from tubulins located near the nucleus in animal cells that help organize cell division (not found in plant cells).

"9+2" Pattern

The specific arrangement of microtubules found in eukaryotic cilia and flagella, in which nine outer doublets surround two central microtubules.

Chloroplast

A two-membrane organelle found in plant cells and algae that contains chlorophyll-containing membrane stacks and converts solar energy into food-stored chemical energy during photosynthesis.

Chlorophyll

The green photosynthetic pigment contained within the internal membrane stacks of chloroplasts that captures solar energy.

Mitochondrion

A double-membraned organelle containing an extensively folded inner membrane that converts chemical energy in food into compounds convenient for the cell to use.

Lynn Margulis

The American biologist who proposed the endosymbiotic theory based on the discovery of distinct DNA in mitochondria and chloroplasts.

Endosymbiotic Theory

The theory stating that chloroplasts and mitochondria are descended from ancient, free-living prokaryotes that established an endosymbiotic relationship inside ancestral eukaryotic cells over a billion years ago.

Cell Wall

A strong, porous supporting layer situated outside the cell membrane that shapes, supports, and protects cells; found in prokaryotes, plants, and fungi, but absent in animal cells.

Cell Membrane

A thin, flexible barrier composed of a lipid bilayer that surrounds all cells and regulates the entry and exit of materials.

Lipid Bilayer

A double-layered sheet of lipids forming the core of biological membranes, consisting of hydrophobic fatty acid tails facing inward and hydrophilic heads facing outward.

Hydrophobic

"Water-hating"; describes nonpolar molecules or chemical groups, such as the fatty acid tails of membrane lipids, that turn away from water.

Hydrophilic

"Water-loving"; describes polar molecules or chemical groups, such as the phosphate head groups of membrane lipids, that interact strongly with water.

Selectively Permeable

A property of biological membranes that allows some substances to pass freely across while blocking others; also referred to as semipermeable.

Fluid Mosaic Model

The model representing the cell membrane as a mosaic of diverse protein and carbohydrate molecules embedded within and freely moving through a flexible lipid bilayer.