6. The Membrane

Passive vs. Active Transport

Structure Of The Cell Membrane: Active and Passive Transport

 Passive transport operates independently of diffusion. 

 No. Passive transport is the diffusion of a solute across a biological membrane. 

 Passive transport operates independently of the concentrations of the moving solute. 

 No. Passive transport must occur down a concentration gradient. 

 In passive transport, solute movement stops when the solute concentration is the same on both sides of the membrane. 

 No. When the concentration is the same on both sides of the membrane, passive transport continues, but the rate of transport is the same in both directions. 

 Passive transport does not occur in the human body. 

 No. Many substances&mdash;such as oxygen, water, and carbon dioxide&mdash;cross membranes by passive transport. 

 Passive transport permits the solute to move in either direction, but the net movement of solute molecules occurs down the concentration gradient of the molecule. 

Consider what is required for passive transport to occur.

Which of the following statements about passive transport is correct?

Classes of Membrane Transport Proteins

Animation: Active Transport

A transport protein that simultaneously transports two different molecules in different directions is called:

 Active transport involves transport proteins, and facilitated diffusion does not. 

 No. Active transport and facilitated diffusion both use transport proteins. 

 Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot. 

 No. The reverse is true. Active transport can move solutes against a concentration gradient, and facilitated diffusion cannot. 

 Facilitated diffusion requires carrier proteins, but active transport requires channel proteins. 

 No. Facilitated diffusion can occur either through channel proteins or via carrier proteins. Active transport cannot occur through channel proteins. 

 Facilitated diffusion involves transport proteins, and active transport does not. 

 No. Both systems depend on specific membrane transport proteins. 

 Active transport requires an input of energy, and facilitated diffusion does not. 

Compare the requirements for these two related processes.

Which of the following is a correct difference between active transport and facilitated diffusion?

Active transport vs Passive transport in just 3 minutes

BioFlix: Membrane Transport Acoss Membranes

Active vs. Passive Transport: Compare and Contrast

Both active and passive transport move substances down their concentration gradients.

Active transport is ATP dependent. Passive transport does not require energy.

Active transport requires cell to cell communication. Passive transport does not require cell communication.

Active transport can be performed without transport proteins while passive transport cannot.

What is the difference between active and passive transport across a membrane?

Cell transport- Passive and Active Transport

Channel Proteins

Movement of Ca2+ into the cell through an ion channel down its concentration gradient

No. A channel protein will permit facilitated diffusion of Ca2+, but the chemical (concentration) gradient is not the only thing contributing to the movement of Ca2+.

Passive diffusion of Ca2+ into the cell down its electrochemical gradient

No. Ca2+ cannot cross a membrane by passive diffusion&mdash;it requires a transport protein (channel or carrier).

Cotransport of Ca2+ into the cell with Cl&ndash;

No. This would not be a good way to get Ca2+ into the cell because it would be coupled to movement of Cl&ndash; against the electrical gradient.

Movement of Ca2+ into the cell through a carrier protein down its electrical gradient

No. A carrier protein will permit facilitated diffusion of Ca2+, but the electrical gradient is not the only thing contributing to the movement of Ca2+.

Facilitated diffusion of Ca2+ into the cell down its electrochemical gradient

Consider all factors involved in the transport of Ca2+ in this situation.

A cell has a membrane potential of &ndash;100 mV (more negative inside than outside) and has 1,000 times more calcium ions outside the cell than inside. Which of the following best describes a mechanism by which Ca2+ enters the cell?

The use of transport proteins to move a substance from low to high concentration.

Movement of a substance down its concentration gradient.

Movement of a substance up its concentration gradient.

Passive membrane transport processes include___________.

Which option below best describes a transporter that requires ATP to move molecules A and B out of the cell?

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1. Introduction to Biology

2. Chemistry

3. Water

4. Biomolecules

5. Cell Components

7. Energy and Metabolism

8. Respiration

9. Photosynthesis

10. Cell Signaling

11. Cell Division

12. Meiosis

13. Mendelian Genetics

14. DNA Synthesis

15. Gene Expression

16. Regulation of Expression

17. Viruses

18. Biotechnology

19. Genomics

20. Development

21. Evolution by Natural Selection

22. Evolution of Populations

23. Speciation

24. History of Life on Earth

25. Phylogeny

26. Prokaryotes

27. Protists

28. Plants

29. Fungi

30. Overview of Animals

31. Invertebrates

32. Vertebrates