Cell Biology Review: Cell Structure, Function, and Biological Molecules

Vocabulary flashcards covering cell structure, organelles, microscopy methods, model organisms, and biological macromolecules from essential cell biology lectures.

Cytoplasma

All the cellular contents situated between the plasma membrane and the cell nucleus, including the cytosol, organelles, and the cytoskeleton.

Cytosol

The aqueous, gel-like fluid portion of the cytoplasm surrounding the organelles, dense with proteins and molecules, where processes like protein synthesis on free ribosomes and glycolysis occur.

Cytoskeleton

A dynamic network of protein filaments in the cytoplasm—comprising intermediate filaments, microtubules, and actin filaments—that gives the cell shape, mechanical strength, and enables intracellular transport and division.

Intermediate Filaments

Cytoskeletal filaments ("steel cables") such as keratin that provide mechanical strength, withstand tensile stress, and maintain cell shape.

Microtubules

Cytoskeletal components ("railroad tracks") composed of tubulin that organize cellular contents, guide intracellular transport, and form the mitotic spindle during cell division.

Actin Filaments

Microfilaments ("ropes and motors") composed of actin that interact with myosin to enable cell movement, muscle contraction, and cytokinesis.

Nucleus

The eukaryotic control center surrounded by a double nuclear membrane (nuclear envelope) with nuclear pores, storing DNA and acting as the site for DNA replication and transcription.

Nuclear Pores

Protein-lined channels in the nuclear envelope that selectively regulate the transport of molecules between the nucleus and the cytoplasm.

Ribosomes

Cellular structures composed of small and large subunits that perform protein synthesis (translation) by reading mRNA sequences, existing free in the cytosol or bound to the rough ER.

Rough Endoplasmic Reticulum (rER)

Membrane-bound organelle studded with ribosomes on its outer surface, dedicated to the synthesis and processing of proteins destined for membranes, endomembrane organelles, or secretion.

Smooth Endoplasmic Reticulum (sER)

Region of the endoplasmic reticulum lacking ribosomes that functions in lipid synthesis, carbohydrate metabolism, drug detoxification, and storage of calcium ions ($Ca^{2+}$).

Golgi Apparatus

Membrane-bound organelle consisting of flattened membrane stacks (cisternae) that receives proteins and lipids from the ER, modifies, sorts, and packages them into transport vesicles.

Lysosome

Single-membrane organelle maintaining an acidic interior ($pH \sim 5.0$) filled with acid hydrolases (such as nucleases, proteases, and lipases) that degrade and recycle waste and worn-out cell components.

Peroxisome

Membrane-bound organelle that carries out oxidative reactions, breaks down very long chain fatty acids via $\beta$-oxidation, and contains catalase to neutralize toxic hydrogen peroxide ($H_2O_2$).

Mitochondrion

Double-membrane organelle that generates ATP via the citric acid cycle in its matrix and oxidative phosphorylation across its folded inner membrane (cristae).

Endosymbiotic Theory

Theory proposing that eukaryotic organelles like mitochondria and chloroplasts evolved from ancient prokaryotes that were engulfed by an ancestral host cell, supported by their circular DNA, 70S ribosomes, and binary fission.

Prokaryotic Cells

Single-celled organisms (bacteria and archaea) that lack a membrane-bound nucleus and specialized membrane-bound organelles, conducting all biochemical reactions within the cytoplasm.

Eukaryotic Cells

Complex cells (found in plants, animals, fungi, and protists) characterized by internal compartmentalization, a membrane-enclosed nucleus, and multiple specialized organelles.

Virus

A non-living infectious agent consisting of genetic material inside a protein coat that lacks independent metabolic machinery and must utilize a host cell to replicate.

Light Microscopy

Visualization method using visible light ($400\text{--}700\,nm$) and a system of lenses to observe cells and tissue sections, with a limit of resolution around $0.2\,\mu m$ ($200\,nm$).

Fluorescence Microscopy

Microscopy technique in which specific cells, organelles, or proteins are labeled with fluorescent dyes or fluorophore-coupled antibodies and illuminated at specific light wavelengths.

Confocal Microscopy

Advanced fluorescence technique that uses a laser and pinhole aperture to eliminate out-of-focus light, yielding sharp optical sections and 3D reconstructions of specimens.

Transmission Electron Microscopy (TEM)

High-resolution imaging technique that passes a beam of electrons through ultrathin fixed sections to reveal cellular ultrastructure and organelle details at the nanometer scale ($\sim 0.1\text{--}1\,nm$).

Model Organism

A species studied in research (e.g., E. coli, S. cerevisiae, C. elegans, D. melanogaster, X. laevis, Danio rerio, Mus musculus) to understand fundamental biological principles, genetics, and human disease mechanisms.

Central Dogma

The core framework of molecular biology stating that genetic information flows from DNA through replication to RNA via transcription, and from RNA to protein via translation.

DNA (Deoxyribonucleic Acid)

Double-stranded helical molecule composed of deoxyribose, phosphate groups, and four nitrogenous bases (Adenine, Tymin, Guanin, Cytosin) that encodes genetic instructions in genes.

Nucleosome

The basic structural subunit of chromatin, consisting of a length of DNA wrapped around a core complex of histone proteins ("beads-on-a-string") containing $\sim 200$ nucleotide pairs of DNA.

Condensation Reaction

A synthetic chemical reaction in which two monomer molecules are joined together covalently with the concurrent removal of a water molecule ($H_2O$).

Hydrolysis Reaction

A chemical reaction in which the covalent bond linking subunits within a polymer is broken by the addition of a water molecule ($H_2O$).

Peptide Bond

The covalent linkage formed between the carboxyl group ($C\text{-terminus}$) of one amino acid and the amino group ($N\text{-terminus}$) of another during a condensation reaction.

Hydrophobic Collapse

A key folding event in an aqueous environment where nonpolar amino acid side chains pack together inside the interior core of a protein to avoid contact with water.

Disulfide Bond

Covalent bond formed by an oxidation reaction between the sulfhydryl ($\text{-SH}$) groups of two cysteine residues, providing structural stability to folded proteins.

Carbohydrate

Organic compound consisting of Carbon, Hydrogen, and Oxygen ($C, H, O$), ranging from monosaccharides (e.g., glucose) and disaccharides to oligosaccharides and polysaccharides (e.g., glycogen, starch).

Phospholipid

Amphipathic lipid molecule composed of a hydrophilic phosphate head and two hydrophobic fatty acid tails, serving as the main structural component of cellular membranes.

Membrane Permeability

Property of lipid bilayers allowing rapid passive movement of small nonpolar molecules ($O_2, CO_2$), reduced passage of small uncharged polar molecules ($H_2O$), and blocking large polar molecules (glucose) and ions ($Na^+, K^+, Cl^-$).

Channel Protein

A membrane transport protein containing a hydrophilic, water-filled pore that allows specific ions or small molecules to pass across the membrane.

Transporter Protein

A membrane protein that binds a specific solute at a solute-binding site and undergoes a conformational change to transfer the molecule across the lipid bilayer.