Diffusion, Osmosis And Active Transport
Overview
Oxygen has to cross the wall of an alveolus, glucose has to leave your gut and enter your blood, and every cell in your body has to stay exactly the right amount hydrated, none of it under the direct control of a nerve or a muscle. All of this happens because particles move across cell membranes by three physical processes: diffusion, osmosis and active transport.
In this lesson you will learn how each process works, why some substances move for free while others cost the cell energy, and how surface area, temperature and concentration gradient between them determine how fast a substance crosses a membrane, from the lining of the small intestine to a red blood cell placed in the wrong solution.
Objectives
- Know simple definitions of diffusion, osmosis and active transport
- Understand that movement of substances into and out of cells can be by diffusion, osmosis (understanding of water potential is required) and active transport
- Understand the factors that affect the rate of movement of substances into and out of cells to include the effects of surface area to volume ratio, temperature and concentration gradient
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Diffusion, Osmosis And Active Transport. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Which process requires energy from respiration? A) Diffusion B) Osmosis C) Active transport D) None of these Answer: C
- A red blood cell placed in a concentrated salt solution will: A) Gain water and burst B) Lose water and crenate C) Stay exactly the same D) Divide by mitosis Answer: B
- Which of the following increases the rate of diffusion across a membrane? A) A longer diffusion distance B) A lower temperature C) A larger surface area D) A shallower concentration gradient Answer: C
- Osmosis is best described as the net movement of: A) Solute particles down a concentration gradient B) Water molecules from higher to lower water potential C) Any particle against a concentration gradient D) Oxygen only, across the alveoli Answer: B
- Why does the small intestine lining have villi and microvilli? A) To reduce its surface area B) To increase its surface area for absorption C) To slow down diffusion D) To prevent active transport Answer: B
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