Membrane Transport - Front Page

Question 1

Transport across Membranes

Answer 1

• Cells are required to maintain a steady internal environment called homeostasis, or maintenance of a dynamic equilibrium
• In order for cells to do this food, water and other substances must be able to cross the phospholipid bilayer

Question 2

What must leave a cell?

Answer 2

Waste products

Question 3

What must enter a cell?

Answer 3

Raw materials/nutrients

Question 4

Extracellular Fluid

Answer 4

The outer solution surrounding membranes

Question 5

Intercellular Fluid

Answer 5

The inner solution within the cell

Question 6

Membranes are…

Answer 6

• Semi-Permeable or selectively permeable
• Membranes are selective for what substances can cross

Question 7

What are the two major forms of membrane transport?

Answer 7

• Passive Transport (no energy)
• Active Transport (Requires energy)

Question 8

Passive Transport

Answer 8

• No chemical energy required
• Movement of substances across membranes without the need for chemical energy

Question 9

Simple Diffusion

Answer 9

• Movement of substances from an area of high concentration to an area of low concentration
• Called movement “down a concentration gradient”
• Diffusion is only useful over short distances

Question 10

In living organisms what molecules use simple diffusion?

Answer 10

• Small, uncharged, non-polar molecules
• Like oxygen and carbon dioxide

Question 11

Facilitated Diffusion

Answer 11

• Diffusion across a membrane at a faster rate
• This is due to the assistance from membrane proteins

Question 12

What are the two types of transport proteins involved in facilitated diffusion?

Answer 12

• Channel Proteins
• Carrier Proteins

Question 13

Channel Proteins

Answer 13

• Have a tunnel-like shape that allows charged molecules and ions to pass through
• Charge on the ion is opposite of the charge on the protein
• Most eukaryotic ion channels are “voltage-gated” which means that they can switch between open and closed

Question 14

Example of cells that use voltage-gated channels

Answer 14

Nerve cells use them to conduct electrical messages

Question 15

Carrier Proteins

Answer 15

• Transport uncharged molecules like glucose
• Bind to molecules and transport them across a membrane
• Alter their shape in the process

Question 16

Solute

Answer 16

Substance that dissolves in a solvent

Question 17

Solute examples

Answer 17

• Salt
• Sugar
• Backing Soda

Question 18

Solvent examples

Answer 18

• Water
• Vinegar
• Alcohol
• Acetone

Question 19

Osmosis

Answer 19

• The diffusion of a solvent, usually water, across a membrane
• The direction of osmosis depends on the relative concentration of water on either side of the membrane

Question 20

Osmotic Pressure

Answer 20

• Pressure created by water molecules as they try to reach equilibrium across a membrane

Question 21

Turgor Pressure

Answer 21

• Outward pressure on the cell wall exerted by water in the vacuole of a plant cell

Question 22

Plasmolysis

Answer 22

• Shrinkage of the cell membrane away from the cell wall, due to the loss of water
• Causes plants to wilt