This lesson covers:
- What cells need and what they produce
- How diffusion works
What do cells need?
Cells need glucose and oxygen.
These allow cells to release energy during aerobic respiration.
What do cells produce?
Cells produce waste products (e.g., carbon dioxide).
These need to be removed from cells.
Diffusion
Diffusion is the movement of particles from an area of high concentration to an area of low concentration.
Diffusion does not need energy.
The cell membrane is a barrier, controlling what enters and leaves the cell. Many substances can move through the cell membrane by diffusion, like glucose in the diagram below.
- Through diffusion, essential nutrients like glucose and oxygen can enter the cell.
- Waste products can be expelled from a cell by diffusion.
Practice Quiz
1. What is diffusion?
Answer: Diffusion is the movement of particles from an area of high concentration to an area of low concentration. It is a passive process that does not require energy.
2. How does diffusion work?
Answer: Diffusion occurs when particles spread out due to their kinetic energy. They move from an area where they are more concentrated to an area where they are less concentrated until equilibrium is reached.
3. What are some examples of diffusion in biology?
Answer: Examples include the diffusion of oxygen and carbon dioxide across cell membranes, the movement of glucose into cells, and the diffusion of waste products out of cells.
4. Why is diffusion important for cells?
Answer: Diffusion is crucial for cells to obtain essential nutrients and oxygen needed for energy production and to expel waste products to prevent toxicity.
5. What is the role of the cell membrane in diffusion?
Answer: The cell membrane acts as a barrier that controls what enters and leaves the cell. It allows certain substances to pass through by diffusion.
6. What factors affect the rate of diffusion?
Answer: Factors include concentration gradient, temperature, surface area, distance, and the nature of the diffusing particles (e.g., size and polarity).
7. How does the concentration gradient affect diffusion?
Answer: A steeper concentration gradient (a larger difference between high and low concentration) results in a faster rate of diffusion.
8. Does diffusion require energy?
Answer: No, diffusion is a passive process and does not require energy.
9. What is the difference between diffusion and osmosis?
Answer: Diffusion is the movement of any particles from high to low concentration, while osmosis specifically refers to the diffusion of water molecules across a selectively permeable membrane.
10. Can large molecules diffuse through the cell membrane?
Answer: Large molecules typically cannot diffuse through the cell membrane directly and may require transport proteins or other mechanisms like facilitated diffusion.
11. What is facilitated diffusion?
Answer: Facilitated diffusion is the process by which molecules that cannot directly diffuse across the membrane pass through special protein channels.
12. How does temperature affect diffusion?
Answer: Higher temperatures increase the kinetic energy of particles, leading to a faster rate of diffusion.
13. What is meant by equilibrium in diffusion?
Answer: Equilibrium is reached when the concentration of particles is the same throughout a given space, and there is no net movement of particles.
14. What are some real-life examples of diffusion?
Answer: Real-life examples include the spreading of perfume in a room, the dissolving of sugar in water, and the exchange of gases in the lungs.
15. How do cells use diffusion to get glucose?
Answer: Glucose molecules move from an area of high concentration outside the cell to an area of low concentration inside the cell through the cell membrane by diffusion.
16. How is oxygen transported into cells by diffusion?
Answer: Oxygen diffuses from the bloodstream, where its concentration is high, into cells, where its concentration is low, across the cell membrane.
17. How do cells remove carbon dioxide by diffusion?
Answer: Carbon dioxide, produced as a waste product in cells, diffuses from inside the cell, where its concentration is high, to outside the cell, where its concentration is low.
18. What role does diffusion play in respiration?
Answer: Diffusion allows oxygen to enter cells for aerobic respiration and carbon dioxide, a byproduct of respiration, to exit cells.
19. Can diffusion occur in liquids and gases?
Answer: Yes, diffusion can occur in both liquids and gases as particles in both states are in constant motion.
20. What is simple diffusion?
Answer: Simple diffusion is the movement of small or lipid-soluble molecules directly across the phospholipid bilayer of the cell membrane without the assistance of transport proteins.
21. What is the importance of the surface area to volume ratio in diffusion?
Answer: A higher surface area to volume ratio allows for more efficient diffusion as there is more membrane surface available for particles to move across.
22. How does distance affect the rate of diffusion?
Answer: The greater the distance particles must travel, the slower the rate of diffusion. Shorter distances result in faster diffusion.
23. What is the role of diffusion in plant cells?
Answer: Diffusion in plant cells is important for the uptake of carbon dioxide for photosynthesis and the release of oxygen, as well as the transport of nutrients and waste products.
24. How does diffusion differ from active transport?
Answer: Diffusion is a passive process that does not require energy, while active transport requires energy to move substances against their concentration gradient.
25. What substances commonly diffuse through the cell membrane?
Answer: Common substances include oxygen, carbon dioxide, water, and small nonpolar molecules.
26. How does diffusion help in gas exchange in the lungs?
Answer: Oxygen diffuses from the alveoli (high concentration) into the blood (low concentration), and carbon dioxide diffuses from the blood (high concentration) into the alveoli (low concentration) to be exhaled.
27. Why can’t ions diffuse freely through the cell membrane?
Answer: Ions are charged particles and cannot pass through the hydrophobic lipid bilayer of the cell membrane without the help of transport proteins.
28. What is the significance of the lipid bilayer in diffusion?
Answer: The lipid bilayer forms a selective barrier that allows certain small or nonpolar molecules to diffuse through while restricting the passage of larger or polar molecules.
29. How does diffusion play a role in kidney function?
Answer: Diffusion in the kidneys helps in the reabsorption of essential nutrients and the excretion of waste products from the blood into the urine.
30. What is the difference between diffusion and bulk flow?
Answer: Diffusion is the movement of individual particles from high to low concentration, while bulk flow is the movement of fluid and its solutes together from high to low pressure.
31. How does diffusion aid in the distribution of nutrients in the body?
Answer: Nutrients absorbed from the digestive tract diffuse into the bloodstream and are transported to cells where they diffuse into the cells to be used for energy and growth.
32. What is the diffusion coefficient?
Answer: The diffusion coefficient is a measure of how easily a substance diffuses through a medium. It depends on factors like temperature, the medium, and the size of the diffusing particles.
33. Can diffusion occur through a solid medium?
Answer: Diffusion through a solid medium is very slow compared to liquids and gases, as the particles in solids are more tightly packed and have less kinetic energy.
34. How does diffusion help in the process of digestion?
Answer: Digested nutrients diffuse from the intestine into the blood vessels, where they are transported to cells throughout the body.
35. Why is diffusion considered a passive process?
Answer: Diffusion is considered passive because it does not require external energy input; it relies on the natural kinetic energy of particles.
36. What is the role of diffusion in cellular signaling?
Answer: In cellular signaling, molecules like hormones and neurotransmitters diffuse across cell membranes to transmit signals between cells.
37. How do gases exchange in plant leaves through diffusion?
Answer: Gases like carbon dioxide and oxygen diffuse through the stomata (pores) in plant leaves, facilitating photosynthesis and respiration.
38. What is the effect of molecular size on diffusion?
Answer: Smaller molecules diffuse faster than larger molecules because they move more easily through the spaces between other molecules.
39. How does the permeability of the cell membrane affect diffusion?
Answer: The cell membrane’s permeability determines which substances can diffuse through it. Permeable membranes allow certain substances to pass while blocking others.
40. What is the role of diffusion in the immune system?
Answer: Diffusion allows immune cells to release signaling molecules and chemokines that diffuse to other cells, coordinating an immune response.
41. How do lipids diffuse across the cell membrane?
Answer: Lipids can diffuse directly through the lipid bilayer of the cell membrane due to their hydrophobic nature.
42. What is dialysis, and how does it relate to diffusion?
Answer: Dialysis is a medical process that uses diffusion to remove waste products and excess substances from the blood of patients with kidney failure.
43. How does diffusion facilitate the removal of toxins from cells?
Answer: Toxins produced as metabolic waste diffuse from inside the cell, where their concentration is higher, to the outside environment, where their concentration is lower.
44. Why do cells rely on diffusion for nutrient uptake?
Answer: Diffusion is an efficient and energy-free way for cells to absorb essential nutrients needed for their survival and function.
45. How does diffusion impact the function of enzymes?
Answer: Diffusion allows substrates to reach enzymes and products to disperse away from enzymes, facilitating continuous biochemical reactions.
46. What is the relationship between diffusion and passive transport?
Answer: Diffusion is a type of passive transport where substances move across cell membranes without the need for energy input.
47. How does diffusion help maintain cell homeostasis?
Answer: Diffusion helps maintain cell homeostasis by regulating the concentration of various substances, ensuring optimal conditions for cellular functions.
48. How does gas diffusion occur in fish gills?
Answer: In fish gills, oxygen diffuses from the water, where its concentration is higher, into the blood, where its concentration is lower, and carbon dioxide diffuses out of the blood into the water.
49. What is the impact of diffusion on drug delivery in the body?
Answer: Diffusion impacts drug delivery by allowing medications to spread from high concentration areas (e.g., injection site) to low concentration areas (e.g., target tissues).
50. What is the significance of diffusion in maintaining pH balance in cells?
Answer: Diffusion helps maintain pH balance by allowing the movement of hydrogen ions and other pH-regulating substances in and out of cells.