Biology-Holt Chap 4 Cells and Their Environment

Why is it dangerous for humans to drink sea water? Choose two options.

• Water would enter our cells through osmosis.resulting in dehydration.

• Water would leave our cells through osmosis, resulting in dehydration.

• Drinking sea water increases the concentration of salts in body fluids.

• Drinking sea water decreases the concentration of salts in body fluids.

How does the sodium potassium pump work? Choose 2 options.

• using energy from ATP, transports 3 potassium ions out of the cell, and brings in 2 sodium ions from outside the cell.

• the ions move against their concentration gradient.

• the ions move with(down) their concentration gradient.

• using energy from ATP, transports 3 sodium ions out of the cell, and brings in 2 potassium ions from outside the cell.

Why is the sodium potassium pump important?

• This process prevents potassium from building up in the cell.

• This process prevents sodium from building up in the cell. which can be toxic.

• This process helps maintain the concentration gradients of sodium and potassium ions across the cell membrane.

• This process helps maintain the pinocytosis of sodium and potassium ions across the cell membrane.

Describe 3 ways in which the binding of a signal molecule to a receptor protein can change the activities of the receiving cell.

• The receptor protein can act as an enzyme, chemically changing the molecules in the cytoplasm by activating other enzymes in the cell.

• The receptor protein may cause the formation of a second messenger that can change the functioning of the cell by activating other enzymes or opening ion channels.

• The receptor protein can cause channels in the membrane to open which changes the permeability of the cell membrane.

• The receptor protein can cause channels in the membrane to disappear.

Difference between diffusion and active transport. Choose 3 options.

• Active transport requires energy to move particles against their concentration gradient.

• Active transport only occurs in cells, but diffusion can occur anywhere that a concentration gradient exists.

• Active transport can occur anywhere a concentration gradient exists but diffusion only occurs in cells.

• Diffusion is the random movement of a substance down its concentration gradient and does not require energy

The movement of free water molecules from high concentration to lower concentration is

• exocytosis

• endocytosis

• osmosis

• active transport

Shields molecule from interior of lipid bilayer

• equilibrium

• carrier protein

• second messenger

• exocytosis

used to export proteins

• carrier proteins

• second messenger

• exocytosis

• endocytosis

organisms adjust internally to changing external conditions

• equilibrium

• exocytosis

• endocytosis

• homeostasis

concentration of a substance is equal throughout a space

• homeostasis

• equilibrium

• osmosis

• hypotonic