Cell Biology: Structure and Transport Mechanisms

Vocabulary practice cards defining key cell anatomy terms, plasma membrane components, passive diffusion processes, and active transport mechanisms.

Cell Wall

A cellular structure found in plant cells that gives them a box-like shape, which animal cells lack.

Plasma Membrane

A phospholipid bilayer surrounding each cell that isolates its internal structures and processes from the external environment.

Cytosol

The intracellular fluid located inside the cell, composed mostly of water with dissolved solutes, storage molecule inclusions, and proteins.

Cytoplasm

The region inside the plasma membrane containing cytosol, organelles, and the cytoskeleton, analogous to a factory floor.

Organelles

Variety of cellular machines with specific functions suspended in the cytosol that separate potentially damaging chemical reactions from surrounding structures.

Cytoskeleton

A network of protein filaments that creates and maintains cell shape, holds organelles in place, and provides a means of intracellular transport.

Nucleus

A roughly spherical organelle that contains DNA and serves as the primary site for making RNA to produce proteins.

Prokaryotes

A cell type, such as bacteria, that does not always contain a nucleus.

Eukaryotes

Cell types, such as plant and animal cells, that contain a distinct nucleus.

Hydrophilic Head

The polar portion of a phospholipid molecule that interacts with and dissolves in water.

Hydrophobic Tail

The nonpolar fatty acid portion of a phospholipid molecule that repels water.

Integral Proteins

Membrane proteins that span the entire plasma membrane, also referred to as transmembrane proteins.

Peripheral Proteins

Membrane proteins located on only one side or the other of the plasma membrane.

Simple Diffusion

The passive movement of mostly nonpolar solutes, such as oxygen, $CO_2$, lipids, and hydrocarbons, straight through the phospholipid bilayer without membrane proteins.

Facilitated Diffusion

The passive movement of charged or polar solutes, such as sodium ions or glucose, across the phospholipid bilayer with the help of a membrane protein.

Osmosis

A type of diffusion specifically involving the movement of water into or out of the cell.

Isotonic Solution

A solution that has approximately the same solute concentration as the cytosol, resulting in no net movement of water across the membrane.

Hypertonic Solution

A solution with a higher concentration of solutes outside the cell than inside, pulling water out of the cell.

Crenation

The shrinking or shriveling process of a cell that occurs when water is pulled out of it in a hypertonic solution.

Hypotonic Solution

A solution with a lower solute concentration outside the cell than inside, driving water into the cell and causing it to swell.

Lysis

The rupturing or bursting of a cell resulting from excessive swelling in a hypotonic solution.

Active Transport

Cellular transport processes that require energy in the form of $ATP$ to move substances across the membrane.

Endocytosis

A form of active transport that functions to bring substances into the cell.

Phagocytosis

A form of endocytosis known as cell eating, where a cell ingests large particles like bacteria or dead/damaged cells.

Pinocytosis

A fluid-phase endocytosis known as cell drinking, where a cell engulfs small fluid droplets from the extracellular fluid.

Exocytosis

The process where vesicles fuse with the plasma membrane to push large molecules and secretions out of the cell.

Transcytosis

A process where molecules are brought into the cell by endocytosis, transported across the cell, and secreted on the opposite side by exocytosis.