Cell biologyLesson 2 of 4 in the course Structure and Function of Plasma Membranes

Passive Membrane Transport: Diffusion, Osmosis, and Tonicity

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

Save course
Lesson progress
0 / 5

Your progress is kept in this browser only.Sign up to save it

Summary

Plasma membranes control what enters and leaves cells. This lesson introduces selective permeability, concentration gradients, and the properties that determine whether substances can cross a membrane.

A plasma membrane is selectively permeable (or semipermeable): it permits some substances to cross while restricting others. This selectivity allows a cell to obtain needed materials, retain essential substances, and limit entry of harmful materials. Without it, the cell could not maintain the conditions required for life.

All flashcards

What is selective permeability?
The property of a membrane that allows certain substances to cross while limiting the passage of others.
What is a concentration gradient?
A difference in the concentration of a substance between locations.
What is facilitated diffusion?
Protein-assisted movement of substances down their concentration gradient without cellular energy expenditure.
When is carrier-mediated transport saturated?
When all available carrier proteins are occupied and transport is at its maximum rate.
What does a hypertonic extracellular solution do to a cell?
It draws water out of the cell, causing the cell to shrink.

Quiz questions

  1. What happens at dynamic equilibrium during diffusion?Answer: Molecules keep moving, but there is no net movement between regions.
  2. What happens to carrier-mediated transport when all available carriers are occupied?Answer: The transport rate reaches its maximum and cannot rise further.
  3. In kidney filtration, what directly drives water and dissolved solutes from blood into renal tubules?Answer: Blood pressure acting across the filtration barrier.
  4. What may happen to a red blood cell in an excessively hypotonic environment?Answer: It takes up water, swells, and may rupture.
  5. How do saltwater fish manage excess salt and water loss?Answer: They secrete salt through their gills and excrete concentrated urine.

Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

More in Cell biology

All Cell biology lessons
Cell biologyKinesin Structure, Motility, Regulation, and Cellular Roles5 flashcards · 5 quiz questions · 4 gamesPlay free →Cell biologyProkaryotic Cell Organization, Envelopes, and Appendages5 flashcards · 5 quiz questions · 4 gamesPlay free →Cell biologyCytoskeletal Filaments, Prokaryotic Systems, and Cellular Mechanics5 flashcards · 5 quiz questions · 4 gamesPlay free →Cell biologyActive and Vesicular Membrane Transport: Gradients, Pumps, and Bulk Transport5 flashcards · 5 quiz questions · 4 gamesPlay free →Cell biologyProkaryotic Binary Fission and FtsZ-Mediated Cytokinesis5 flashcards · 5 quiz questions · 4 gamesPlay free →Cell biologyProkaryotic and Eukaryotic Cell Features and Size Constraints5 flashcards · 5 quiz questions · 4 gamesPlay free →