Unit 2: Cell Structures, Organelles, and Cellular Transport Vocabulary

Practice vocabulary flashcards covering prokaryotic and eukaryotic cell organelles, structural differences, membrane permeability, and active/passive transport mechanisms.

Prokaryotic Cell

A unicellular organism that lacks a membrane-bound nucleus surrounding its circular DNA and lacks membrane-bound organelles.

Bacterial Capsule

The outermost layer of a bacterium that helps it adhere to surfaces.

Nucleoid

The region in a prokaryotic cell where the single circular piece of DNA is located.

Eukaryotic Cell

A type of cell containing a membrane-bound nucleus around its DNA, multiple linear chromosomes, and membrane-bound organelles.

Organelle

Meaning 'little organ', these are structures within a cell that perform specific functions to keep the cell alive.

Plasma Membrane

A selectively permeable boundary found in all cells composed of a phospholipid bilayer that controls what enters and exits the cell.

Amphipathic

Describing a molecule, such as a phospholipid, that possesses both hydrophilic (water-attracting) glycerol heads and hydrophobic (water-repelling) fatty acid tails.

Nuclear Envelope

A structure composed of two phospholipid bilayers containing nuclear pores that surrounds and protects the nucleus.

Nucleolus

A dense region inside the nucleus whose function is to create ribosomes.

Ribosome

A non-membrane-bound structure found in all cells that serves as the site of protein synthesis by reading RNA to make polypeptides.

Rough Endoplasmic Reticulum (Rough ER)

A membrane-bound organelle studded with ribosomes where newly synthesized proteins fold into their tertiary structure.

Smooth Endoplasmic Reticulum (Smooth ER)

A membrane-bound organelle lacking ribosomes that functions in lipid synthesis, drug detoxification, and calcium storage.

Golgi Apparatus

A membrane-bound organelle that stores, modifies (such as by adding carbohydrates), and packages proteins.

Lysosome

An organelle containing digestive enzymes that breaks down cellular wastes; present in animal cells but absent in plant cells.

Central Vacuole

A large organelle in plant cells that stores water and waste while maintaining turgor pressure on the cell wall.

Contractile Vacuole

A specialized organelle in protists (such as Amoeba, Paramecium, and Euglena) that absorbs and releases excess water to prevent the cell from bursting.

Mitochondria

Double-membraned organelles found in plant and animal cells that manufacture the cell's main energy molecule, ATP.

Chloroplast

A multi-membraned organelle in plant cells that acts as the site of glucose production.

Microtubules

Cytoskeleton structures made of tubulin protein that move and separate chromosomes during cell division and form cilia and flagella.

Microfilaments

Cytoskeleton filaments that provide structural support and facilitate cell motility, such as muscle contraction in humans.

Centrosome

An organelle found exclusively in animal cells that manufactures microtubules.

Plasmodesmata

Tiny tunnels penetrating plant cell walls that enable cell-to-cell communication and intercellular transport.

Endomembrane System

A interconnected network of internal cellular structures that function together to produce, modify, and transport proteins.

Selective Permeability

The characteristic of a membrane that allows certain substances to cross more easily than others.

Diffusion

The passive net movement of particles from an area of high concentration to an area of low concentration due to random motion until dynamic equilibrium is reached.

Osmosis

The diffusion of water across a membrane from a higher concentration of free water to a lower concentration of free water.

Facilitated Diffusion

A passive transport process in which molecules cross the plasma membrane down their concentration gradient through transport channel proteins without expending energy.

Aquaporin

A specialized membrane transport protein that facilitates the rapid diffusion of water across cell membranes.

Hypertonic Solution

An extracellular environment with a higher concentration of solute relative to the inside of the cell, causing net water flow out of the cell.

Hypotonic Solution

An extracellular environment with a lower concentration of solute relative to the inside of the cell, causing net water flow into the cell.

Isotonic Solution

An environment where the solute concentration is equal inside and outside the cell, resulting in no net movement of water.

Active Transport

The movement of substances across a cell membrane against their concentration gradient (from low to high concentration) using cellular energy in the form of ATP.

Sodium-Potassium Pump

An active transport protein mechanism that hydrolyzes ATP to pump 3 $\text{Na}^+$ ions out of the cell and 2 $\text{K}^+$ ions into the cell.

Endocytosis

An active transport mechanism where cells engulf external particles or liquids by wrapping the plasma membrane inward to form a vesicle.

Exocytosis

An active transport process where membrane-bound vesicles fuse with the plasma membrane to secrete materials out of the cell.

Surface Area to Volume Ratio (SA:V)

A mathematical relationship where smaller cells possess a larger ratio, maximizing plasma membrane efficiency for diffusion and exchange of materials.