Table of contents

1. Overview of Cell Biology2h 49m
2. Chemical Components of Cells1h 14m
3. Energy1h 33m
4. DNA, Chromosomes, and Genomes2h 31m
5. DNA to RNA to Protein2h 31m
6. Proteins1h 36m
7. Gene Expression1h 42m
8. Membrane Structure1h 4m
- The Lipid Bilayer
  38m
- Membrane Proteins
  25m
9. Transport Across Membranes1h 52m
10. Anerobic Respiration1h 5m
11. Aerobic Respiration1h 11m
12. Photosynthesis52m
13. Intracellular Protein Transport2h 18m
14. Cell Signaling1h 28m
15. Cytoskeleton and Cell Movement1h 39m
16. Cell Division3h 5m
17. Meiosis and Sexual Reproduction50m
18. Cell Junctions and Tissues48m
19. Stem Cells13m
- Stem Cells
  13m
20. Cancer44m
21. The Immune System1h 6m
22. Techniques in Cell Biology1h 41m

9. Transport Across Membranes

Principles of Transmembrane Transport

Cell Biology

9. Transport Across Membranes

Principles of Transmembrane Transport

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Multiple Choice

Which is an example of facilitated diffusion?

Fat soluble molecules passing through the plasma membrane with the concentration gradient

Water traveling across the plasma membrane with the help of channel proteins called aquaporins

K+ being moved across the plasma membrane against its concentration gradient

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Verified step by step guidance

Understand the concept of facilitated diffusion: Facilitated diffusion is a type of passive transport that allows substances to cross membranes with the assistance of special transport proteins. It does not require energy and moves substances down their concentration gradient.

Identify the role of channel proteins: In facilitated diffusion, channel proteins or carrier proteins help specific molecules or ions to pass through the plasma membrane. These proteins provide a pathway for the molecules to move across the membrane.

Consider the movement of water: Water molecules can move across the plasma membrane through specialized channel proteins known as aquaporins. This process is a classic example of facilitated diffusion, as it involves the passive movement of water molecules down their concentration gradient.

Differentiate from active transport: Active transport, unlike facilitated diffusion, requires energy to move substances against their concentration gradient. For example, the movement of K+ ions against their concentration gradient would require energy, typically in the form of ATP.

Apply the concept to the given examples: Evaluate each example to determine if it involves passive movement with the help of proteins. Water traveling across the plasma membrane with the help of aquaporins fits the criteria for facilitated diffusion, as it involves passive transport with the aid of channel proteins.