Chapter 4: A Tour of the Cell – Vocabulary Flashcards

Key terms and definitions to review core concepts from the cell biology lecture, including cell types, organelles, organelle functions, and the flow of genetic information.

Electronegativity

The attractive force that an atom exerts on shared electrons in a bond; determines bond type (ionic, polar covalent, non-polar covalent) based on differences between atoms.

Ionic bond

A bond formed by transfer of electrons from one atom to another, resulting in oppositely charged ions held together by electrostatic attraction.

Polar covalent bond

A covalent bond with unequal sharing of electrons, creating partial positive and negative charges within the molecule.

Non-polar covalent bond

A covalent bond with equal sharing of electrons, resulting in no partial charges.

Hydrogen bond

A weak intermolecular interaction between partial charges, notably between water molecules, contributing to properties like water cohesion.

Prokaryotic cell

A cell without a nucleus or membrane-bound organelles; includes Bacteria and Archaea.

Eukaryotic cell

A cell with a nucleus and membrane-bound organelles; generally larger and more complex than prokaryotic cells.

Nucleus

Organelle that houses DNA; site of genetic control and transcription; contains the nucleolus and chromatin.

Chromatin

DNA wrapped around histone proteins inside the nucleus.

Chromosome

Visible, condensed form of DNA and proteins during cell division.

Nucleolus

Nuclear subregion where ribosomal RNA (rRNA) synthesis and ribosome assembly begin.

Ribosome

Molecular machine that synthesizes proteins; can be free in cytosol or bound to the rough endoplasmic reticulum.

Rough Endoplasmic Reticulum (Rough ER)

ER studded with ribosomes; synthesizes proteins destined for secretion or membrane localization.

Smooth Endoplasmic Reticulum (Smooth ER)

ER lacking ribosomes; synthesizes lipids, stores calcium, and detoxifies certain substances.

Golgi apparatus

Modifies, sorts, and ships proteins received from the ER via vesicles; prepares them for their final destinations.

Vesicles

Small membrane-bound sacs that transport proteins and other molecules between organelles or to the plasma membrane.

Lysosome

Organelle with digestive enzymes that degrade macromolecules and old organelles; involved in apoptosis and immune defense.

Vacuole

Membrane-bound organelle; plant vacuoles are large and store water and solutes, providing turgor; other vacuoles store materials.

Mitochondrion

Organelle that produces ATP through cellular respiration; contains its own DNA and ribosomes.

Chloroplast

Organelle that conducts photosynthesis in plants and algae; converts light energy into chemical energy; contains its own DNA.

Endosymbiont theory

Hypothesis that mitochondria and chloroplasts originated as free-living prokaryotes engulfed by a host cell and evolved mutualism.

Cytoskeleton

Network of protein filaments (microfilaments, intermediate filaments, microtubules) that supports cell shape and enables movement.

Microfilaments (actin filaments)

Thinnest cytoskeletal filaments involved in cell movement and muscle contraction.

Intermediate filaments

Cytoskeletal filaments that provide mechanical support and anchor organelles.

Microtubules

Thick, hollow tubes that organize cell structure and serve as tracks for motor proteins; form the spindle apparatus.

Cilia

Short, numerous projections that move cells or extracellular fluids; powered by dynein atop microtubules.

Flagella

Long projections that enable cell movement (e.g., sperm); propelled by dynein and composed of microtubules.

Extracellular Matrix (ECM)

Structural network outside the cell that holds tissues together and supports the plasma membrane; rich in collagen.

Collagen

A major structural protein in the ECM; accounts for a large portion of body protein and provides tensile strength.

Tight junctions

Junctions that seal neighboring cells to prevent fluid leakage between cells.

Desmosomes (anchoring junctions)

Junctions that fasten cells together in strong sheets by linking intermediate filaments.

Gap junctions

Intercellular channels that allow the passage of ions and small molecules for cell-to-cell communication.

Plasmodesmata

Plant cell–wall channels that enable transport and signaling between adjacent plant cells.

Plasma membrane

Phospholipid bilayer that encloses the cell; regulates substances entering and leaving (selectively permeable).

Cell wall

Rigid layer outside the plasma membrane in plants and some organisms; mainly cellulose in plants; provides protection and support.

Central dogma (DNA–RNA–Protein flow)

Describes the directional flow of genetic information: DNA is transcribed to RNA, which is translated into protein.

DNA

Double-stranded molecule encoding genetic information; organized into chromatin and chromosomes.

RNA

Ribonucleic acid; single-stranded molecule that carries genetic instructions from DNA to ribosomes for protein synthesis.

Transcription

Process by which RNA is synthesized from a DNA template inside the nucleus.

Translation

Process by which ribosomes synthesize proteins using mRNA as a template in the cytoplasm.

Nuclear envelope

Double membrane surrounding the nucleus; contains nuclear pores for transport between nucleus and cytoplasm.

Nuclear pores

Channels in the nuclear envelope that regulate movement of molecules between the nucleus and cytoplasm.

Cytosol

Fluid component of the cytoplasm where dissolved ions and proteins reside; part of the cytoplasm.

Endomembrane system

Interconnected membrane system including ER, Golgi, lysosomes, vacuoles, and plasma membrane involved in protein and lipid processing and transport.

Mitochondrial DNA (mtDNA)

Genetic material found in mitochondria; maternally inherited and separate from nuclear DNA; used in certain forensic contexts.

Maternally inherited

Inheritance pattern where genetic material is passed from mother to offspring, such as mtDNA.

Ribosomal RNA (rRNA)

RNA component of ribosomes synthesized in the nucleolus; essential for ribosome function.