Textbook Question
Which of the following groups of amino acid residues would likely be found in the portion that crosses the lipid bilayer?
a. Acidic
b. Basic
c. Polar uncharged
d. Nonpolar
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6. The Membrane
Introduction to Membrane Transport
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Which of the following is not a characteristic of carrier-mediated transport?
A
Specificity for certain molecules
B
Requires energy input in all cases
C
Saturation at high substrate concentrations
D
Can be inhibited by similar molecules
Verified step by step guidance1
Understand the concept of carrier-mediated transport: Carrier-mediated transport involves proteins that facilitate the movement of substances across cell membranes. These proteins are specific to certain molecules, meaning they only transport particular substances.
Recognize the characteristic of specificity: Carrier proteins are highly specific, meaning they bind and transport only specific molecules or ions. This specificity is a key feature of carrier-mediated transport.
Identify the concept of saturation: Saturation occurs when all carrier proteins are occupied, and the rate of transport reaches a maximum. At high substrate concentrations, the transport rate cannot increase further, which is a characteristic of carrier-mediated transport.
Consider the concept of inhibition: Carrier-mediated transport can be inhibited by molecules that are similar in structure to the substrate, as they may compete for binding sites on the carrier protein.
Evaluate the requirement for energy input: Not all carrier-mediated transport requires energy. Facilitated diffusion, a type of carrier-mediated transport, does not require energy input, whereas active transport does. Therefore, the statement 'Requires energy input in all cases' is not a characteristic of carrier-mediated transport.
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