Cell Biology Part 1 – Plasma Membrane & Organelles

Vocabulary flashcards covering key terms on cell structure, plasma membrane components, transport mechanisms, microscopy, and organelle functions from the lecture notes.

Cell Metabolism

All chemical reactions occurring within a cell, often coupled so that energy released by one fuels another.

Synthesis of Molecules

Cellular production of proteins, nucleic acids, lipids, etc., which determines a cell’s structure and function.

Cell Communication

Transmission of chemical or electrical signals between cells, e.g., nerve-to-muscle signaling.

Reproduction and Inheritance

Cell division that copies DNA and the passing of genetic traits to the next generation via gametes.

Plasma Membrane

Lipid bilayer with embedded proteins forming the cell’s outer boundary; regulates entry/exit and communication.

Nucleus

Membrane-bound organelle that houses DNA and directs cellular activities.

Cytoplasm

Region between plasma membrane and nucleus containing cytosol and organelles.

Organelle

Specialized intracellular structure performing a specific function.

Ribosome

Non-membranous organelle (rRNA + proteins) that serves as the site of protein synthesis.

Rough Endoplasmic Reticulum (RER)

Membranous tubules with attached ribosomes; synthesizes proteins for the Golgi apparatus.

Smooth Endoplasmic Reticulum (SER)

Membranous tubules lacking ribosomes; synthesizes lipids/carbohydrates, detoxifies chemicals, stores Ca²⁺.

Golgi Apparatus

Stack of flattened membranes that modifies, packages, and distributes proteins & lipids.

Lysosome

Membrane-bound vesicle from Golgi containing digestive enzymes.

Peroxisome

Membrane vesicle that degrades lipids & amino acids and breaks down hydrogen peroxide.

Proteasome

Tubelike protein complex that breaks down cytoplasmic proteins.

Mitochondrion

Double-membrane organelle with cristae; major site of aerobic ATP production.

Centrioles

Cylindrical microtubule triplets that organize microtubule formation and form basal bodies of cilia/flagella.

Cilia

10-µm plasma-membrane extensions containing microtubule doublets; move materials over cell surfaces.

Flagellum

55-µm plasma-membrane extension; propels human spermatozoa.

Microvilli

Microfilament-filled membrane folds that increase surface area for absorption/secretion or sensory reception.

Light Microscope

Uses visible light; ~0.1 µm resolution; routine for biopsies with staining.

Electron Microscope

Uses electron beams; ~0.1 nm resolution; includes TEM (through specimen) and SEM (surface).

Transmission Electron Microscope (TEM)

Electron microscope passing electrons through a thin specimen to reveal internal structures.

Scanning Electron Microscope (SEM)

Electron microscope reflecting electrons off a specimen’s surface to create 3-D images.

Atomic Force Microscope (AFM)

Uses a deflected mechanical probe to map surfaces in three dimensions.

Membrane Potential

Electrical charge difference across plasma membrane (positive outside, negative inside) due to ion regulation.

Membrane Lipids

Primarily phospholipids and cholesterol forming the bilayer; minor carbohydrates present.

Phospholipid

Amphipathic molecule with hydrophilic head and hydrophobic tail; assembles into bilayers.

Hydrophilic

Water-loving; polar regions that interact with aqueous environments.

Hydrophobic

Water-fearing; non-polar regions that avoid water.

Phospholipid Bilayer

Double layer with tails inward and heads outward forming the core of the plasma membrane.

Fluid-Mosaic Model

Concept that the membrane is flexible with proteins ‘floating’ in a fluid lipid bilayer.

Cholesterol

Minor membrane lipid whose amount modulates membrane fluidity; OH group aligns near phospholipid heads.

Glycolipid

Lipid with attached carbohydrate on outer membrane surface; part of glycocalyx.

Glycoprotein

Protein with attached carbohydrate; often serves as marker, receptor, or part of glycocalyx.

Glycocalyx

Outer surface coat of glycolipids, glycoproteins, and adsorbed molecules involved in cell recognition & protection.

Integral Membrane Protein

Protein embedded deeply in the bilayer; often spans the membrane.

Peripheral Membrane Protein

Protein attached to inner or outer membrane surface without penetrating the bilayer deeply.

Marker Molecule

Cell-surface glycoprotein or glycolipid enabling cell identification, e.g., immune self-recognition.

Attachment Protein

Integral protein (cadherin/integrin) connecting cells to each other or to extracellular molecules/cytoskeleton.

Cadherin

Attachment protein that links one cell to another cell.

Integrin

Attachment protein that links a cell to extracellular matrix molecules.

Transport Protein

Integral protein enabling ions or molecules to cross the plasma membrane; exhibits specificity, competition, saturation.

Specificity (Transport)

Each transport protein binds and moves only a particular molecule or ion type.

Competition (Transport)

Similar molecules vie for the same transport protein binding site.

Saturation (Transport)

Maximum transport rate reached when all binding sites on proteins are occupied.

Channel Protein

Transport protein forming a hydrophilic pore; includes leak and gated channels.

Leak Channel

Channel protein always open, allowing passive ion movement at rest.

Gated Channel

Channel that opens/closes in response to stimuli (ligand or voltage).

Ligand-Gated Ion Channel

Channel that opens/closes when a specific chemical signal binds to its receptor site.

Voltage-Gated Ion Channel

Channel that opens/closes in response to changes in membrane potential.

Carrier Protein (Transporter)

Integral protein that binds a substance, changes shape, and moves it across the membrane.

Uniport

Carrier-mediated movement of a single type of molecule/ion across the membrane.

Symport (Cotransport)

Carrier-mediated movement of two different substances in the same direction.

Antiport (Counter-transport)

Carrier-mediated movement of two different substances in opposite directions.

ATP-Powered Pump

Transport protein that hydrolyzes ATP to move ions/molecules against gradients.

Receptor Protein

Membrane protein with an extracellular binding site that detects specific ligands for cell signaling.

Ligand

Any chemical signal molecule that binds to a receptor to alter cell activity.

G Protein Complex

Trimeric (αβγ) intracellular complex activated by receptors; mediates signal to intracellular effectors.

Membrane-Associated Enzyme

Protein in or on the membrane catalyzing reactions, e.g., intestinal dipeptidases.

Cystic Fibrosis

Genetic disease caused by defective chloride ion channels leading to thick secretions in lungs and pancreas.

Membrane Fusion

Process where fluid lipid bilayers merge, aided by membrane fluidity.