Exam 4: Cell Membranes, Transport, and Communication

The passive movement of water across a selectively permeable membrane is called ________.

Protein-lined tunnels that span the small intercellular space separating adjacent cells and that allow the rapid and direct passage of ions and small molecules,including signaling molecules,are called ________.

Lipids often move within the body in complexes known as lipoproteins; what advantage does this strategy provide?

To coordinate the contraction of the numerous muscle cells that form the heart,signals must travel rapidly between muscle cells.To allow this rapid communication,muscle cells in the heart are connected by

Gap junctions allow large molecules to move from cell to cell.

The concentration of solutes is higher within the mitochondria than it is in the cytosol.Therefore,the cytosol is ________ to the inside of the mitochondrion.

Cell signaling

A white blood cell at the site of a puncture wound engulfs a large cluster of bacteria forming a large internal vesicle.This is an example of

Which of the following would directly supply energy to an active carrier protein?

A positive correlation has been shown between HDL and dementia; unfortunately,lowering HDL without medication is difficult,and serious side effects have been reported.

Short-lived signaling molecules are most effective for

The signaling molecules that interact with cell surface receptors cannot cross the plasma membrane and would generally be classified as large and/or________.

The concentration of glucose inside a cell is higher than the concentration outside that cell,yet glucose continues to enter the cell.This is an example of

Steroids are unable to cross the plasma membrane.

Even though the concentration of water in a cell remains constant in an isotonic solution,the random movement of water molecules during ________ requires that water be constantly moving in both directions across the plasma membrane.

A concentration ________ is said to exist when a molecule is more abundant in one area than it is in another.

Channel proteins provide a means for large,________ molecules to move across the plasma membrane without an expenditure of energy.

During ________ endocytosis,specific substances interact with proteins located in the plasma membrane of the cell.

Elevated HDL (high-density lipoprotein)levels seem to provide positive cardiovascular health effects,even for individuals with abnormally high blood cholesterol.What best describes the beneficial action of HDL?

The following figure illustrates a plasma membrane. Which substance in the figure is crossing the membrane using simple diffusion?