Cell Structure and Function

Vocabulary flashcards covering key concepts of cell structure, plasma membrane transport, organelles, the cytoskeleton, cell junctions, and cellular metabolism from Chapter 3.

Cell Theory

A foundational biological theory stating that a cell is the basic unit of life, all living things are made up of cells, and new cells arise from pre-existing cells.

Surface-Area-to-Volume Ratio

A physical relationship where smaller cells have a larger surface area relative to their volume, allowing them to efficiently move nutrients in and waste out while remaining metabolically active.

Compound Light Microscope

A type of microscope with lower magnification that uses light beams to view images and can be used to view live specimens.

Transmission Electron Microscope (TEM)

An electron microscope that uses electrons to produce a high-magnification 2-D image of internal cellular structures, which cannot view live specimens.

Scanning Electron Microscope (SEM)

An electron microscope that uses electrons to yield high-magnification 3-D images of surface structures, which cannot view live specimens.

Prokaryotic Cell

A basic cell type lacking a nucleus and membrane-bound organelles, containing a nucleoid and typically measuring $0.2\text{--}5\,\mu\text{m}$; found in domains Bacteria and Archaea.

Eukaryotic Cell

A cell type containing a nucleus and membrane-bound organelles; found in domain Eukarya, including protists, fungi, plants, and animals.

Endosymbiosis

The evolutionary hypothesis that eukaryotic organelles developed from early eukaryotic cells engulfing prokaryotic cells.

Fluid Mosaic Model

A structural model of the plasma membrane describing it as a phospholipid bilayer embedded with movable proteins, cholesterol for support, and attached carbohydrates like glycoproteins and glycolipids.

Selective Permeability

The characteristic of the plasma membrane that allows certain substances to pass into or out of the cell while restricting others.

Diffusion

The random movement of molecules down a concentration gradient from an area of higher concentration to an area of lower concentration.

Osmosis

The diffusion of water molecules across a membrane from an area of high water concentration to an area of low water concentration.

Facilitated Transport

The transport of molecules from a higher to lower concentration across a membrane via specific protein channels without requiring energy.

Active Transport

The movement of molecules from lower to higher concentration across a membrane via a protein carrier or pump, requiring energy in the form of ATP.

Endocytosis

The process of transporting molecules or cells into the cell via invagination of the plasma membrane to form a vesicle.

Pinocytosis

A form of endocytosis in which a cell engulfs fluid containing small particles.

Phagocytosis

A form of endocytosis in which cells, such as white blood cells, engulf pathogens or large particles.

Receptor-Mediated Endocytosis

A targeted form of endocytosis initiated when specific particles bind to receptors in the plasma membrane.

Exocytosis

The transport of molecules out of a cell via the fusion of a vesicle with the plasma membrane.

Nucleus

The storage place of genetic information in a eukaryotic cell, bound by a nuclear envelope with nuclear pores, housing chromatin and the nucleolus.

Nucleolus

An area within the nucleus containing ribosomal RNA (rRNA) where ribosomal subunits are assembled.

Ribosomes

Organelles made of rRNA and protein that serve as the sites of protein synthesis; found attached to the endoplasmic reticulum or free-floating in the cytoplasm.

Polyribosomes

Groups of free-floating ribosomes in the cytoplasm that synthesize proteins in clusters.

Endomembrane System

A series of cellular membranes that transport molecules; composed of the nuclear envelope, endoplasmic reticulum, vesicles, Golgi apparatus, and lysosomes.

Rough Endoplasmic Reticulum (RER)

A membrane system studded with ribosomes used to synthesize proteins that are packaged into membranes or vesicles.

Smooth Endoplasmic Reticulum (SER)

A membrane system lacking ribosomes that synthesizes lipids and conducts carbohydrate metabolism, drug metabolism, and ion storage (especially $\text{Ca}^{2+}$).

Sarcoplasmic Reticulum

A specialized smooth endoplasmic reticulum in muscle cells that triggers contractions when it releases its stored $\text{Ca}^{2+}$ ions.

Golgi Apparatus

A stack of flattened membranous sacs that modifies, sorts, packages, and secretes proteins and lipids received from the endoplasmic reticulum.

Lysosomes

Membranous vesicles produced by the Golgi apparatus that contain hydrolytic enzymes to break down cell parts or foreign substances.

Lysosomal Storage Diseases (LSD)

Genetic disorders caused by the lack of a specific lysosomal enzyme, causing un-hydrolyzed macromolecules to accumulate and eventually lead to cell death.

Cytoskeleton

A network of protein fibers in the cell that maintains shape, anchors organelles, and enables cell movement.

Microtubules

The largest cytoskeletal fibers, composed of tubulin dimers, which function in maintaining shape, vesicle transport, and spindle formation during cell division.

Actin Filaments

Thin cytoskeletal fibers involved in cellular movement, muscle contraction alongside myosin, cleavage furrow formation, and structural support of microvilli.

Intermediate Filaments

Medium-sized cytoskeletal fibers, such as keratin, that provide mechanical strength to cells and anchor organelles.

Cilia and Flagella

Microtubule-containing cellular projections responsible for movement, such as propelling sperm (flagella) or sweeping mucus along the respiratory tract (cilia).

Extracellular Matrix (ECM)

A protective network of proteins and polysaccharides outside the cell containing collagen for strength, elastin for elasticity, and fibronectin connected to integrins.

Adhesion Junctions

Intercellular junctions that firmly attach the cytoskeletons of adjacent cells together.

Tight Junctions

Intercellular junctions consisting of fused plasma membrane proteins that create a tight, leak-proof barrier between cells.

Gap Junctions

Intercellular junctions formed by fused membrane channel proteins that allow direct communication and molecule transfer between adjacent cells.

Mitochondria

Double-membraned organelles with inner cristae folds that produce cellular energy by converting glucose into ATP via cellular respiration.

Cellular Respiration

The aerobic process in cells that breaks down glucose into carbon dioxide and water to generate ATP while consuming $\text{O}_2$ and releasing $\text{CO}_2$.

Glycolysis

An anaerobic process occurring in the cytoplasm that splits glucose into two pyruvate molecules, yielding 2 ATP and NADH.

Citric Acid Cycle

A cyclic pathway in the mitochondria that breaks down pyruvate derivatives, releases $\text{CO}_2$, and produces 2 ATP along with electron-carrying NADH.

Electron Transport Chain

A sequence of membrane-bound carriers in mitochondria that uses electrons from NADH to generate 32–34 ATP, requiring $\text{O}_2$ as the final electron acceptor.

Fermentation

An anaerobic metabolic pathway that produces ATP when $\text{O}_2$ is absent, yielding lactate in animal cells and ethanol with $\text{CO}_2$ in yeast and plant cells.

Enzymes

Biological catalysts (typically proteins) that speed up chemical reactions by lowering the required activation energy without being consumed.

Activation Energy

The amount of energy required to initiate a chemical reaction, which is lowered in the presence of an enzyme.

Active Site

The specific structural region on an enzyme where a substrate molecule binds to undergo a reaction.

Coenzymes

Nonprotein organic molecules, often derived from vitamins like C, B12, folic acid, or niacin, that assist enzyme function.