BSC1010 Chapter 3: Cells and Cell Communication

Comprehensive vocabulary flashcards covering cell structure, microscopy, membranes, eukaryotic organelles, the cytoskeleton, and cell communication mechanisms from Chapter 3.

Micrograph

A photographic image of an object or specimen taken through a microscope.

Scanning Electron Microscope (SEM)

A microscope that scans the surface of a specimen with a focused beam of electrons to produce detailed, high-resolution three-dimensional images of surface topography.

Transmission Electron Microscope (TEM)

A microscope that transmits a beam of electrons through an ultrathin specimen section to view detailed internal ultrastructure and cellular cross-sections.

Light Microscope

An optical instrument that uses visible light and glass lenses to magnify and resolve images of cells and small biological specimens, allowing observation of living organisms.

Surface Area-to-Volume Ratio

The relationship between cell surface area ($\text{Surface Area} = 6 \times \text{Area}$) and internal volume ($\text{Volume} = l \times w \times h$), which decreases as a cell grows larger, restricting maximum cell size for efficient exchange of materials.

Amphipathic

Having both hydrophilic (water-loving) and hydrophobic (water-fearing) regions, a property characteristic of membrane phospholipids.

Fluid Mosaic Model

A structural model describing the plasma membrane as a dynamic, fluid phospholipid bilayer embedded with a mosaic of proteins, cholesterol, and carbohydrates.

Integral Membrane Proteins

Proteins embedded permanently within the lipid bilayer that penetrate or span the hydrophobic core of the plasma membrane.

Peripheral Membrane Proteins

Proteins that are loosely bound to the exterior or interior surfaces of the phospholipid bilayer rather than embedded in the hydrophobic core.

Glycoprotein

A membrane protein covalently linked to a carbohydrate chain, projecting into the extracellular space to aid in cell-cell recognition and signaling.

Glycolipid

A membrane lipid covalently attached to a carbohydrate chain, located on the outer surface of the bilayer and functioning in cellular recognition.

Endomembrane System

A eukaryotic internal membrane network—including the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, and plasma membrane—that compartmentalizes and carries out cellular metabolic functions (excluding mitochondria and chloroplasts).

Rough Endoplasmic Reticulum (rER)

A region of the endoplasmic reticulum studded with attached ribosomes that functions in the synthesis, folding, and transport of membrane and secretory proteins.

Smooth Endoplasmic Reticulum (sER)

A region of the endoplasmic reticulum devoid of ribosomes that specializes in lipid synthesis, carbohydrate metabolism, and chemical or poison detoxification.

Golgi Apparatus

A eukaryotic organelle composed of flattened membranous sacs that modifies, sorts, and packages proteins and lipids received from the endoplasmic reticulum for secretion or delivery.

Lysosome

A membranous digestive organelle containing hydrolytic enzymes used to break down macromolecules, recycle cellular components, and digest foreign materials engulfed via phagocytosis.

Ribosome

A cellular complex composed of a large subunit and a small subunit that translates messenger RNA into polypeptide chains during protein synthesis.

70S Ribosome

The sedimentation size of ribosomes found in bacterial cells, as well as inside eukaryotic mitochondria and chloroplasts.

80S Ribosome

The sedimentation size of ribosomes found in the cytoplasm and on the rough endoplasmic reticulum of eukaryotic cells.

Nucleus

The double-membrane-bound eukaryotic organelle that houses genetic material (chromatin/DNA) and directs cellular growth and reproduction.

Nucleolus

A dense structure inside the nucleus responsible for ribosomal RNA (rRNA) synthesis and the assembly of ribosome subunits.

Chromatin

The complex of genomic DNA and associated proteins that fills the eukaryotic nucleus and condenses to form chromosomes during cell division.

Nuclear Pores

Protein complexes perforating the nuclear envelope that regulate the bidirectional exchange of macromolecules, including RNA and proteins, between the nucleus and the cytoplasm.

Nuclear Lamina

A network of intermediate filaments lining the inner surface of the nuclear membrane that mechanically supports the envelope and maintains nuclear shape.

Peroxisome

A specialized metabolic compartment containing oxidative enzymes that transfer hydrogen atoms to oxygen to form hydrogen peroxide, functioning in fatty acid breakdown and detoxifying compounds.

Mitochondrion

A double-membrane eukaryotic organelle containing cristae, circular DNA, and $70\text{S}$ ribosomes that performs cellular respiration to generate ATP.

Cristae

Infoldings of the inner mitochondrial membrane that expand the surface area available for electron transport chains and ATP synthesis complexes.

Mitochondrial Matrix

The fluid-filled inner compartment enclosed by the inner mitochondrial membrane containing circular DNA, $70\text{S}$ ribosomes, and metabolic enzymes.

Chloroplast

A double-membrane photosynthetic organelle in plant and algal cells containing thylakoids, stroma, circular DNA, and $70\text{S}$ ribosomes, responsible for converting light energy into chemical energy.

Stroma

The fluid-filled internal space surrounding thylakoids inside a chloroplast where circular DNA, $70\text{S}$ ribosomes, and carbon-fixation enzymes reside.

Endosymbiosis Theory

The evolutionary theory stating that mitochondria and chloroplasts originated from ancestral prokaryotic organisms that were engulfed by a host eukaryotic cell.

Cytoskeleton

A dynamic intracellular network of protein fibers comprising microtubules, microfilaments, and intermediate filaments that provides structural shape, mechanical support, and movement.

Microtubules

Hollow cylindrical cytoskeletal fibers constructed of tubulin subunits that maintain cell shape, coordinate chromosome movement during division, and act as tracks for organelle transport.

Microfilaments

Solid, thin protein filaments composed of actin chains that bear tension, support cell shape, and drive cellular motility and muscle contraction.

Intermediate Filaments

Tension-bearing cytoskeletal fibers of medium diameter that provide mechanical stability, anchor the nucleus and organelles, and reinforce the nuclear lamina.

Cell Wall

A rigid extracellular layer outside the plasma membrane in plant, fungal, and bacterial cells that maintains structural shape, provides protection, and prevents excessive water uptake.

Local Signaling

Intercellular communication occurring across short distances, including paracrine and synaptic signaling, where signaling molecules diffuse to nearby target cells.

Endocrine Signaling

Long-distance cellular communication where specialized endocrine cells secrete hormones directly into body fluids or the bloodstream to travel to distant targets.

Paracrine Signaling

A form of local signaling where a cell secretes messenger molecules into the local extracellular environment to act on nearby target cells.

Synapse

The narrow junction between the axon terminal of a sending neuron and the dendrite or membrane of a target cell where neurotransmitters diffuse.

Neurotransmitter

A chemical messenger synthesized by nerve cells that diffuses across a synapse to bind specific receptors on an adjacent neuron or effector cell.

Signal Transduction Pathway

A sequence of molecular interactions (reception, transduction, and response) that relays and converts an extracellular signal from a membrane receptor to produce a specific cellular response.

G Protein-Coupled Receptor (GPCR)

A cell-surface transmembrane receptor that interacts with an intracellular G protein to activate an enzyme or downstream signaling pathway upon ligand binding.

Receptor Tyrosine Kinase (RTK)

A plasma membrane receptor exhibiting enzymatic kinase activity that transfers phosphate groups from ATP to tyrosine amino acids, triggering multiple transduction pathways.

Intracellular Receptor

A receptor protein located in the cytoplasm or nucleus that binds small, hydrophobic signaling molecules (such as steroid hormones) that diffuse across the plasma membrane.

Phosphorylation Cascade

A series of sequential enzymatic steps during signal transduction where protein kinases phosphorylate and activate one another, amplifying the original signal.

Second Messenger

Small, non-protein, water-soluble molecules or ions—such as cyclic AMP ($\text{cAMP}$) or calcium ions ($\text{Ca}^{2+}$)—that diffuse rapidly through the cytoplasm to propagate an intracellular signal.