Q. No.I. Over small distances, in plants, substances move by diffusion and by cytoplasmic streaming supplemented by active transport.
II. Transport over long distances, in plants, proceeds through the vascular system and is called as transpiration.
1. Only I is correct
2. Only I is incorrect
3. Both I and II are correct
4. Both I and II are incorrect
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Substances that have a hydrophilic moiety:
1. have to be transported across the plasma membrane by active transport
2. can diffuse across the plasma membrane at a slower rate, if larger in size
3. do not need a concentration gradient to diffuse across the plasma membrane
4. need to be facilitated even along the concentration gradient
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Refer section 11.1.1 of your NCERT. What peculiarity does NCERT mention regarding diffusion and solids ?
1. It does not occur in solids
2. It is more easily visualized in solids
3. It requires expenditure of external energy and occurs against concentration gradient
4. Diffusion in solids rather than of solids is more likely.
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In section 11.1.2, NCERT states that a concentration gradient needs to be present in spite of the fact that facilitated diffusion is facilitated by a carrier. Why is it so?
1. These protein carriers have ATPase activity.
2. These protein carriers can not move in the membrane.
3. These protein carriers can not establish concentration gradients.
4. These protein carriers can provide only symport with the use of external energy.
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Facilitated diffusion allows cells to:
1. achieve uphill transport without ATP energy
2. select substances for uptake
3. stop transport of hydrophilic substances
4. decrease the rate of diffusion of lipophilic substances
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Unlike a symporter and an antiporter, a uniporter:
1. is not an integral membrane protein
2. is a cell surface carbohydrate
3. is not a co-transporter
4. cannot be used for active transport
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Identify the incorrect statement regarding aquaporins:
1. Water channels are transmembrane proteins made up of eight different types of aquaporins.
2. Water moves most rapidly in tissues that have aquaporin water channels.
3. The presence of water channels increases membrane permeability to water.
4. Aquaporins selectively conduct water molecules in and out of the cell but allow some passage of protons.
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| I | II | III | |
| Requires special membrane proteins | No | Yes | Yes |
| Highly selective | No | Yes | Yes |
| Transport saturates | No | Yes | Yes |
| Uphill transport | No | No | Yes |
| Requires ATP energy | No | No | Yes |
| I | II | III | |
| 1. | Simple diffusion | Facilitated diffusion | Active transport |
| 2. | Facilitated diffusion | Simple diffusion | Active transport |
| 3. | Simple diffusion | Active transport | Facilitated diffusion |
| 4. | Facilitated diffusion | Active transport | Simple diffusion |
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Active transport of substances does not involve:
1. transport of solute along the concentration gradient.
2. use of a specific membrane transport protein.
3. hydrolysis of ATP.
4. transport of solute against a concentration gradient.
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The main difference between active transport and facilitated diffusion is:
1. In active transport the molecules move from areas of high to areas of low concentration
2. In active transport, you need carrier proteins
3. In active transport, you need ATP to move molecules against a concentration gradient
4. In active transport, only water molecules move
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