Chapter 8, Problem 8.102AP

a.

Summary Introduction

To determine:

The concentration of the solution outside the cell as hypertonic or hypotonic if that solute is being transported across the cell membrane by passive diffusion.

Introduction:

Hypotonic solution: in this condition the concentration of solute is greater inside the cell than outside.

Hypertonic solution: in this condition the concentration of solutes is greater outside the cell than inside it.

Passive diffusion: diffusion moves solutes in a direction that attempts to equalize the concentration on either side of a membrane. This process does not require any additional energy, so this simple diffusion process is also called passive diffusion.

b.

Summary Introduction

To determine:

The concentration of the solution outside the cell as hypertonic or hypotonic if that solute is being transported across the cell membrane by facilitated transport.

Introduction:

Hypotonic solution: in this condition the concentration of solute is greater inside the cell than outside.

Hypertonic solution: in this condition the concentration of solutes is greater outside the cell than inside it.

Facilitated transport: small polar molecules diffuse very slowly across the nonpolar barrier found in the centre of the cell membrane. To enable small molecules and ions to pass through the cell membrane, some proteins found in the cell membrane have polar channels that open and close, allowing small polar molecules and ions to be transported across the cell membrane, to equalize the concentration gradient. These proteins are often integral membrane proteins. This type of transport is called facilitated transport and such transport does not require energy.

c.

Summary Introduction

To determine:

The concentration of the solution outside the cell as hypertonic or hypotonic if that solute is being transported across the cell membrane by active transport.

Introduction:

Hypotonic solution: in this condition the concentration of solute is greater inside the cell than outside.

Hypertonic solution: in this condition the concentration of solutes is greater outside the cell than inside it.

Active transport: some ions or small molecules must be transported across the cell membrane in the opposite direction of diffusion. Transporting ions or small polar molecules across the cell membrane in a direction opposite to equalizing concentration is possible and it also requires the assistance of a protein channel. This pumping in the opposite direction is called active transport, and it requires energy.