23. Lipids

During respiration, oxygen gas diffuses into cells spontaneously. Which type of transport is this?

How would you expect an H⁺ ion to move out of the cell if [H⁺] inside the cell is lower than extracellular fluid?

In oxidative phosphorylation, H⁺ ions from the intermembrane space of mitochondria to the mitochondrial matrix, which type of membrane transport is this?

As noted earlier (Section 22.3), he first step in glycolysis, which occurs within cells, is phosphorylation of glucose to glucose 6-phosphate. Why does this step prevent passive diffusion of glucose back out of the cell?

Identify the type of transport described by each of the following:

a. A molecule moves through a protein channel.

Identify the type of transport described by each of the following:

b. O₂ moves into the cell from a higher concentration outside the cell.

Identify the type of transport described by each of the following:

a. An ion moves from low to high concentration in the cell.

 Match the lipoprotein (1 to 4) with its description (a to d). (15.6)

1. chylomicrons

2. VLDL

3. LDL

4. HDL

b. transports most of the cholesterol to the cells

Identify the type of transport (passive diffusion, facilitated transport, or active transport) that will occur for the following molecules:

(b) glucose, no energy required

Identify the type of transport (passive diffusion, facilitated transport, or active transport) that will occur for the following molecules:

(b) nitrogen

Do the following processes require energy when transporting molecules across the cell membrane?

(c) active transport

Describe the concentration of the solution outside the cell as hypertonic or hypotonic if that solute is being transported across the cell membrane by

(b) facilitated transport.

Which process requires energy—passive or active transport? Why is energy sometimes required to move solute across the cell membrane?