BIOL101 Unit 1: Cells, Membranes, & Homeostasis

Vocabulary flashcards covering cell theory, prokaryotic vs eukaryotic cells, membrane structure and transport, the endomembrane system, and cellular organelles.

Cell Theory

The fundamental biological principle stating that all living organisms are made up of cells, the cell is the fundamental unit of life, and all cells come from preexisting cells.

Prokaryotic Cell

A cell type that lacks a nucleus and has no internal compartmentalization.

Eukaryotic Cell

A cell type that contains a nucleus and other internal membrane-bound organelles.

Amphipathic

Describing a molecule, such as a phospholipid, that possesses both hydrophilic (water-loving) and hydrophobic (water-fearing) regions.

Micelle

A spherical structure formed by lipids with bulky heads and single hydrophobic tails, packed with hydrophobic tails on the inside away from water.

Liposome

A spherical structure formed by a lipid bilayer enclosing a central aqueous compartment.

Fluid Mosaic Model

A model describing cell membranes as dynamic structures composed of lipids and embedded proteins that move laterally within the bilayer.

Saturated Fatty Acid

A fatty acid chain that lacks double bonds between carbon atoms, resulting in a straight structure that favors tight phospholipid packing.

Unsaturated Fatty Acid

A fatty acid chain containing one or more double bonds that introduce kinks into the phospholipid tails, reducing packing tightness and increasing membrane fluidity.

Cholesterol

An amphipathic lipid component of animal cell membranes that helps regulate membrane fluidity in response to temperature changes.

Integral Membrane Proteins

Proteins permanently associated with the cell membrane, including transmembrane proteins that span the entire lipid bilayer.

Peripheral Membrane Proteins

Proteins temporarily associated with either the internal or external surface of the cell membrane.

Transporter

A membrane protein that moves ions or molecules across the cellular membrane.

Receptor

A membrane protein that binds extracellular signals and transmits information into the cell.

Anchor

A membrane protein that attaches to cellular components or other proteins to help maintain cell structure and position.

Selective Permeability

The property of the cell membrane that allows only specific molecules to pass through while preventing others.

Passive Diffusion

The random movement of solute particles from an area of higher concentration to an area of lower concentration down their concentration gradient without energy input.

Osmosis

The passive movement of water molecules across a selectively permeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Facilitated Diffusion

The passive transport of molecules down their concentration gradient across a membrane through channel or carrier proteins.

Active Transport

The movement of molecules across a membrane against their concentration gradient, requiring cellular energy expenditure.

Sodium-Potassium Pump ($\text{Na}^+/\text{K}^+$ Pump)

An active transport antiporter that consumes ATP to move $3\,\text{Na}^+$ ions out of the cell and $2\,\text{K}^+$ ions into the cell against their concentration gradients.

Secondary Active Transport

Transport mechanism where the movement of a molecule against its concentration gradient is driven by an electrochemical gradient created by primary active transport (such as pumping $\text{H}^+$).

Hypertonic Solution

An extracellular solution with a higher solute concentration than the cell interior, causing water to leave the cell and the cell to shrink.

Hypotonic Solution

An extracellular solution with a lower solute concentration than the cell interior, causing water to enter the cell and potentially leading to cell lysis.

Isotonic Solution

An extracellular solution having the same solute concentration as the cell interior, resulting in no net water movement.

Contractile Vacuole

A specialized organelle in single-celled organisms that absorbs excess internal water and expels it outside to preserve osmotic balance.

Turgor Pressure

The force exerted by water pushing against the rigid plant cell wall, providing structural stability and rigidity to the plant.

Endomembrane System

A network of interconnected internal membranes in eukaryotic cells, including the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, and cell membrane.

Nucleus

The membrane-bound organelle that stores genetic information and serves as the primary site for RNA synthesis in eukaryotic cells.

Nuclear Envelope

A double membrane that encloses the nucleus and isolates genetic material from the cytoplasm.

Nuclear Pore

A protein-lined channel in the nuclear envelope that allows passive diffusion of small molecules and ions while actively regulating transport of large proteins and RNA.

Rough Endoplasmic Reticulum (RER)

The portion of the ER studded with ribosomes on its outer membrane, serving as a primary site for protein synthesis.

Smooth Endoplasmic Reticulum (SER)

The portion of the ER that lacks ribosomes and functions as the primary site of lipid and steroid synthesis.

Golgi Apparatus

An organelle composed of flattened membrane stacks (cisternae) that modifies, sorts, and packages proteins and lipids, as well as synthesizes carbohydrates.

Lysosome

A specialized vesicle originating from the Golgi apparatus containing digestive enzymes that break down macromolecules at an acidic internal $\text{pH } 5$.

Peroxisome

An organelle that degrades specific organic molecules, such as fatty acids, and synthesizes other molecules, including cholesterol and certain phospholipids.

Mitochondria

Double-membrane organelles that generate ATP through cellular respiration and contain their own genome and internal electron transport chain.

Chloroplast

A double-membrane organelle containing thylakoid membranes that captures light energy to produce sugars via photosynthesis.

Endosymbiont Theory

The theory stating that mitochondria and chloroplasts evolved from free-living prokaryotes that were engulfed by an ancestral eukaryotic cell.

Cytoskeleton

A network of protein filaments in eukaryotic cells that provides internal structural support and maintains cell shape.

Plasmodesmata

Membrane-lined channels penetrating plant cell walls that connect the cytoplasm of adjacent plant cells.

Endocytosis

The cellular process in which the cell membrane invaginates to engulf extracellular material into a membrane-bound vesicle.

Exocytosis

The cellular process in which intracellular vesicles fuse with the cell membrane to export contents into the extracellular space.