The cell membrane, also called the plasma membrane, is a flexible boundary surrounding every cell. Its basic framework is a phospholipid bilayer: two adjacent layers of phospholipid molecules. In each layer, the phosphate heads face watery environments, while the fatty-acid tails point inward toward one another.
Because the heads face the watery fluid inside and outside the cell, and the tails meet in the membrane’s interior, the bilayer forms a stable boundary between these environments.
All flashcards
Integral and peripheral membrane proteins
Integral proteins are embedded in the lipid bilayer; peripheral proteins associate with its surfaces or with integral proteins.
Channel protein
An integral membrane protein that provides a selective pathway for particular substances to cross the membrane.
Receptor and ligand
A receptor binds a particular molecule, called a ligand, and this binding can trigger a cellular response.
Glycocalyx
A cell-surface coating formed by carbohydrate chains on membrane proteins and some lipids; it supports interactions and cell recognition.
Exocytosis
A process in which a vesicle fuses with the cell membrane and releases its contents outside the cell.
Quiz questions
What does selective permeability mean for a cell membrane?Answer: Some substances pass through more readily than others.
How does facilitated diffusion move substances across a membrane?Answer: Through membrane proteins, down a concentration gradient, without ATP.
What happens to a cell placed in a hypertonic solution?Answer: It loses water and tends to shrink.
What drives filtration across a membrane or tissue barrier?Answer: A hydrostatic pressure difference.
For each ATP molecule used, what does the sodium-potassium pump transport?Answer: Three Na⁺ ions out and two K⁺ ions in.
Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.