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    which of the following statements about carrier proteins is false?

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    State whether the following statements are true or false.Carrier proteins are necessary for active transport to occur.

    Click here👆to get an answer to your question ✍️ State whether the following statements are true or false.Carrier proteins are necessary for active transport to occur.

    State whether the following statements are true or false.

    Question

    Carrier proteins are necessary for active transport to occur.

    A

    True

    B

    False

    Medium Open in App Solution Verified by Toppr

    Correct option is A)

    Carrier proteins are those which facilitate diffusion of molecules across the cell membrane, they allow movement of molecules in and out of the cells against the concentration gradient. Active transport requires carrier proteins also called as pumps. They need ATP energy because the transport is uphill, against the concentration gradient.

    So, the correct answer is 'True'.

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    Mastering A and P Lab 3 Flashcards

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    Which of the following is NOT a passive process?

    facilitated diffusion

    osmosis vesicular transport filtration

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    vesicular transport

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    When the solutes are evenly distributed throughout a solution, we say the solution has reached _______.

    diffusion equilibrium permeability velocity

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    equilibrium

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    Terms in this set (13)

    Which of the following is NOT a passive process?

    facilitated diffusion

    osmosis vesicular transport filtration vesicular transport

    When the solutes are evenly distributed throughout a solution, we say the solution has reached _______.

    diffusion equilibrium permeability velocity equilibrium

    Which of the following does NOT describe the plasma membrane?

    impermeable

    selectively permeable

    semipermeable

    differentially permeable

    impermeable

    Which of the following requires a membrane-bound carrier for transport?

    simple diffusion filtration

    facilitated diffusion

    osmosis

    facilitated diffusion

    Which of the following statements about carrier proteins is FALSE?

    They assist in simple diffusion.

    They can become saturated if the maximum transport rate is exceeded.

    They might have to change shape slightly to accommodate a solute.

    They are found integrated into the plasma membrane.

    they assist in simple diffusion

    Which of the following statements about facilitated diffusion is FALSE?

    The movement requires a carrier protein.

    The movement of a given solute usually occurs in both directions (into and out of the cell).

    The movement of the solute is passive.

    The movement of the solute is with its concentration gradient.

    the movement of a given solute usually occurs in both directions

    Which of the following is NOT a reason why a solute would require facilitated diffusion?

    The solute is lipid insoluble.

    The solute is too large to pass on its own.

    The solute directly requires ATP for its transport.

    The solute is hydrophilic.

    the solute directly requires atp for its transport

    Which of the following would increase the rate of facilitated diffusion?

    decreasing the number of carrier proteins

    increasing the steepness of the concentration gradient

    decreasing the concentration of solutes

    increasing the amount of ATP available

    increasing the steepness of the concentration gradient

    Which of the following statements about osmosis is FALSE?

    Water moves toward the solution with the lowest concentration of solutes.

    It is passive.

    It is a type of diffusion.

    It is specific for the movement of water.

    water moves toward the solution with the lowest concentration of solutes

    A Hypertonic solution:_______.

    will induce cell swelling

    will induce cell bursting

    will induce no net movement of water

    will induce cell shrinkage

    will induce cell shrinkage

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    Carrier Proteins and Active Membrane Transport

    The process by which a carrier protein transfers a solute molecule across the lipid bilayer resembles an enzyme-substrate reaction, and in many ways carriers behave like enzymes. In contrast to ordinary enzyme-substrate reactions, however, the transported solute is not covalently modified by the carrier protein, but instead is delivered unchanged to the other side of the membrane.

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    Carrier Proteins and Active Membrane Transport

    The process by which a carrier protein transfers a solute molecule across the lipid bilayer resembles an enzyme-substrate reaction, and in many ways carriers behave like enzymes. In contrast to ordinary enzyme-substrate reactions, however, the transported solute is not covalently modified by the carrier protein, but instead is delivered unchanged to the other side of the membrane.

    Each type of carrier protein has one or more specific binding sites for its solute (substrate). It transfers the solute across the lipid bilayer by undergoing reversible conformational changes that alternately expose the solute-binding site first on one side of the membrane and then on the other. A schematic model of how such a carrier protein is thought to operate is shown in Figure 11-6. When the carrier is saturated (that is, when all solute-binding sites are occupied), the rate of transport is maximal. This rate, referred to as max, is characteristic of the specific carrier and reflects the rate with which the carrier can flip between its two conformational states. In addition, each transporter protein has a characteristic binding constant for its solute, m, equal to the concentration of solute when the transport rate is half its maximum value (Figure 11-7). As with enzymes, the binding of solute can be blocked specifically by either competitive inhibitors (which compete for the same binding site and may or may not be transported by the carrier) or noncompetitive inhibitors (which bind elsewhere and specifically alter the structure of the carrier).

    Figure 11-6

    A model of how a conformational change in a carrier protein could mediate the passive transport of a solute. The carrier protein shown can exist in two conformational states: in state A, the binding sites for solute are exposed on the outside of the lipid (more...)

    Figure 11-7

    The kinetics of simple diffusion and carrier-mediated diffusion. Whereas the rate of the former is always proportional to the solute concentration, the rate of the latter reaches a maximum (max) when the carrier protein is saturated. The solute concentration (more...)

    As we discuss below, it requires only a relatively minor modification of the model shown in Figure 11-6 to link the carrier protein to a source of energy in order to pump a solute uphill against its electrochemical gradient. Cells carry out such active transport in three main ways (Figure 11-8):

    Figure 11-8

    Three ways of driving active transport. The actively transported molecule is shown in and the energy source is shown in

    1.

    couple the uphill transport of one solute across the membrane to the downhill transport of another.

    2.

    couple uphill transport to the hydrolysis of ATP.

    3.

    , which are found mainly in bacterial cells, couple uphill transport to an input of energy from light, as with bacterio-rhodopsin (discussed in Chapter 10).

    Amino acid sequence comparisons suggest that, in many cases, there are strong similarities in molecular design between carrier proteins that mediate active transport and those that mediate passive transport. Some bacterial carriers, for example, which use the energy stored in the H+ gradient across the plasma membrane to drive the active uptake of various sugars, are structurally similar to the carriers that mediate passive glucose transport into most animal cells. This suggests an evolutionary relationship between various carrier proteins; and, given the importance of small metabolites and sugars as an energy source, it is not surprising that the superfamily of carriers is an ancient one.

    We begin our discussion of active transport by considering carrier proteins that are driven by ion gradients. These proteins have a crucial role in the transport of small metabolites across membranes in all cells. We then discuss ATP-driven pumps, including the Na+ pump that is found in the plasma membrane of almost all cells.

    Go to:

    Active Transport Can Be Driven by Ion Gradients

    Some carrier proteins simply transport a single solute from one side of the membrane to the other at a rate determined as above by max and m; they are called uniporters. Others, with more complex kinetics, function as in which the transfer of one solute strictly depends on the transport of a second. Coupled transport involves either the simultaneous transfer of a second solute in the same direction, performed by symporters, or the transfer of a second solute in the opposite direction, performed by antiporters (Figure 11-9).

    Figure 11-9

    Three types of carrier-mediated transport. This schematic diagram shows carrier proteins functioning as uniporters, symporters, and antiporters.

    The tight coupling between the transport of two solutes allows these carriers to harvest the energy stored in the electrochemical gradient of one solute, typically an ion, to transport the other. In this way, the free energy released during the movement of an inorganic ion down an electrochemical gradient is used as the driving force to pump other solutes uphill, against their electrochemical gradient. This principle can work in either direction; some coupled carriers function as symporters, others as antiporters. In the plasma membrane of animal cells, Na+ is the usual co-transported ion whose electrochemical gradient provides a large driving force for the active transport of a second molecule. The Na+ that enters the cell during transport is subsequently pumped out by an ATP-driven Na+ pump in the plasma membrane (as we discuss later), which, by maintaining the Na+ gradient, indirectly drives the transport. (For this reason ion-driven carriers are said to mediate whereas ATP-driven carriers are said to mediate Intestinal and kidney epithelial cells, for example, contain a variety of symport systems that are driven by the Na+ gradient across the plasma membrane; each system is specific for importing a small group of related sugars or amino acids into the cell. In these systems, the solute and Na+ bind to different sites on a carrier protein. Because the Na+ tends to move into the cell down its electrochemical gradient, the sugar or amino acid is, in a sense, “dragged” into the cell with it. The greater the electrochemical gradient for Na+, the greater the rate of solute entry; conversely, if the Na+ concentration in the extracellular fluid is reduced, solute transport decreases (Figure 11-10).

    Source : www.ncbi.nlm.nih.gov

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