Chapter 5 Biology

A phospholipid molecule in a membrane can:

• only spin (rotate around its vertical axis).

• only move side-to-side (lateral movement).

• only flip (rotate between the two halves of the bilayer).

• both spin (rotate around its vertical axis) and move side-to-side (lateral movement).

A protein that is temporarily associated with a biological membrane is a(n):

• peripheral membrane protein.

• transmembrane protein.

• integral membrane protein.

• transmembrane protein and an integral membrane protein.

An amphipathic molecule is one that:

• makes up a membrane.

• contains both polar and nonpolar regions.

• has a head and tail domain.

• can fully dissolve in water.

Predict how phospholipids would arrange if they were placed in a nonpolar solution rather than a polar solution like water.

• The phospholipids would form a normal bilayer.

• The phospholipid tails would orient toward the solution, and the heads would cluster away from the solution.

• The phospholipids would form a normal liposome.

• The phospholipid heads would orient toward the solution, and the tails would cluster away from the solution.

Which lipid composition option has the least membrane fluidity?

• phospholipids with short-chain, unsaturated fatty acids

• phospholipids with long-chain, unsaturated fatty acids

• phospholipids with long-chain, saturated fatty acids

• phospholipids with short-chain, saturated fatty acids

Imagine a cell that has a membrane composed mostly of lipids with saturated fatty acid tails, and that this membrane also has low cholesterol content. What are the characteristics of this cell membrane?

• The lipids would be able to easily transition between the inner and outer layers of the bilayer constituting the cell membrane.

• The lipids contained in such a membrane would be highly mobile and in nearly constant flux.

• Due to its low cholesterol content, the cell membrane would lose its fluidity at cold temperatures.

• The characteristics of this cell membrane will closely mirror those of a membrane composed of only unsaturated fatty acids.

Considering the amino acids that are found in various domains of transmembrane proteins, which statement would be true?

• Polar or charged amino acids would be prevalent in the transmembrane domain, in contact with the environment of the inner membrane.

• Nonpolar amino acids would be prevalent in the extracellular domain, in contact with the environment outside of the cell.

• Polar or charged amino acids would be prevalent in the intracellular domain, in contact with cytosol.

• Nonpolar amino acids would be prevalent in the transmembrane domain, in contact with the environment of the inner membrane.

The random movement of molecules within a solution is referred to as:

• osmosis

• transport

• translation

• diffusion

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Why does active transport of molecules across a membrane require ATP?

• An input of energy is needed to move all molecules across a membrane.

• An input of energy is needed to allow the movement of molecules from an area of low concentration to one of higher concentration.

• An input of energy is needed because the movement of molecules requires the synthesis of additional membrane.

Which molecules can easily diffuse across a plasma membrane?

• gases like O2 and CO2

• small charged molecules, such as ions

• proteins

• large polar molecules