Cell Membrane & Transport Unit Review

Comprehensive vocabulary flashcards reviewing cell membrane structure, components, tonicity environments, and passive versus active transport mechanisms.

Cell Membrane

A selectively permeable cellular boundary composed of a phospholipid bilayer, proteins, cholesterol, and carbohydrates that controls the movement of substances in and out of the cell.

Cell Membrane Structure

The structural organization of the cell membrane, consisting of a phospholipid bilayer with hydrophilic heads and hydrophobic tails, embedded cholesterol, transport proteins (channel and carrier), and extracellular carbohydrate chains.

Phospholipids

The principal structural lipids of the cell membrane, each composed of a hydrophilic component and a hydrophobic component arranged into a bilayer.

Hydrophilic

Water-attracting; refers to the polar heads of phospholipids that face the aqueous environments inside and outside the cell.

Hydrophobic

Water-repelling; refers to the nonpolar fatty acid tails of phospholipids that turn inward toward the interior of the lipid bilayer.

Cholesterol

A lipid molecule embedded within the hydrophobic core of the phospholipid bilayer that helps maintain membrane fluidity and stability.

Carbohydrates

Molecules attached to proteins or lipids on the extracellular surface of the cell membrane that assist in cell recognition and signaling.

Channel Protein

A membrane transport protein that forms a fixed pore or tunnel through the membrane, allowing specific substances to diffuse passively.

Carrier Protein

A membrane protein that binds specific molecules and changes conformation to transport them across the phospholipid bilayer.

Selectively Permeable (Semi-permeable)

The property of a biological membrane that permits certain substances to pass through while preventing others from crossing, allowing the cell to regulate its internal environment.

Passive Transport

The movement of substances across a cell membrane down their concentration gradient without requiring cellular energy.

Active Transport

The transport of substances across a membrane against their concentration gradient, requiring cellular energy (such as ATP) and transport proteins.

Diffusion

The passive movement of solute particles across the phospholipid bilayer from an area of higher concentration to an area of lower concentration.

Osmosis

The passive movement or diffusion of water across a selectively permeable membrane in response to solute concentration differences.

Facilitated Diffusion

The passive transport of molecules across the cell membrane along their concentration gradient with the assistance of channel or carrier proteins, requiring no energy.

Endocytosis

An active bulk transport mechanism in which the cell membrane invaginates and pinches off to bring materials into the interior of the cell.

Exocytosis

An active bulk transport mechanism where intracellular vesicles fuse with the cell membrane to release their contents outside the cell.

Protein Pumps

Membrane proteins that utilize cellular energy to actively transport ions or molecules across the cell membrane against their concentration gradient.

Equilibrium

The condition in which the concentration of substances or rates of movement across a membrane become equal on both sides, resulting in no net movement.

Hypertonic Solution

A solution with a higher concentration of solutes than the cell interior, causing net movement of water out of the cell and causing the cell to shrivel.

Hypotonic Solution

A solution with a lower concentration of solutes than the cell interior, causing net movement of water into the cell and causing the cell to swell and potentially burst.

Isotonic Solution

A solution having the same solute concentration as the cell interior, where water enters and leaves at equal rates so the cell retains its normal shape.

Tonicity Effects on Red Blood Cells

The physiological responses shown across three solutions: Figure A shows a hypertonic solution where water exits and the cell crenates; Figure B shows an isotonic solution with equal water movement and normal cell shape; Figure C shows a hypotonic solution where water enters and causes the cell to swell and lyse.

Membrane Transport Pathways Diagram

Top: Simple diffusion ($\text{high} \rightarrow \text{low}$, no energy needed). Middle: Facilitated diffusion through a channel protein ($\text{high} \rightarrow \text{low}$, no energy needed). Bottom: Active transport using a protein pump and energy source A ($\text{low} \rightarrow \text{high}$, energy required).