2.2 Transport of Substances Across a Cell Membrane (CQ - Exam)

Question 1

What is a concentration gradient?

Answer 1

The difference in concentration of a dissolved substance in a solution between a region of high density and one of lower

Question 2

diffusion

Answer 2

Solutes and solvents movement

Question 3

What are three factors that affect the rate of diffusion, and why do they affect it?

Answer 3

1. Higher temperatures - when hotter they move faster, when colder they move slower
2. Physical pressure - it will push the molecules faster
3. Chemical pressure - how concentrated it is during movement

Question 4

Explain the similarities and differences between diffusion and osmosis.

Answer 4

Both balance the concentrations of 2 solutions.

Diffusion moves both solvent and solute particles, and no semipermeable membrane is involved.

Osmosis only moves solvent particles, and semipermeable membrane is involved.

Question 5

Would you expect the normal environment of your cells and plant cells to be typically isotonic, hypertonic, or hypotonic?

Answer 5

• Our cells like to be the same internally as externally, preferring isotonic
• Do not like to expand and contract
• Plants maintain rigid structure, the vacuole pressure on the cell wall relies on that for their structure
• They’d like hypotonic, and want water to be rushing in

Question 6

What do facilitated diffusion and active transport have in common, and how do they differ?

Answer 6

Facilitated diffusion
- They have a channel or carrier (transmembrane protein)
- Moving with the concentration gradient
- Requires no ATP
Active Xport
- Has a protein
- Against the concentration gradient
- Requires ATP
Similar
- Both require proteins

Question 7

Explain how the properties of the molecules and macromolecules that comprise biological membranes are important to processes that transport materials in and out of cells.

Answer 7

• Only non polar molecules can cross because they move with the chemical pressure of a concentration gradient
• Polar things are larger and it requires more effort to cross through

Question 8

Describe the sources of energy used by primary active transport and secondary active transport.

Answer 8

• Source of energy is ATP
• The phosphate binds to the protein causing it to change the shape
• Electrochemical moves the synport
• Primary is ATP
• Secondary is the electrochemical gradient

Question 9

Using your understanding of osmosis, predict what change(s) would occur in an animal cell suddenly exposed to a solution with a much lower solute concentration than the interior of the cell. Explain your reasoning with one or two sentences using the term(s) isotonic, hypertonic, or hypotonic as appropriate.

Answer 9

• Water is going to move from high to low concentration (lysis)
• Water will flow in to the cell due to it being hypertonic
• the solutes on the inside has more than the outside (outside is hypotonic)

Question 10

Plants with non-woody stems (herbaceous plants) rely heavily)’ on turgor pressure to help hold them upright. Given that fact, what do you think the normal, healthy environment is like for those plant cells (isotonic, hypotonic, or hypertonic)?

Answer 10

Hypotonic because the cell wall prevents bursting and organelles are pushed to the edge of cell.

Question 11

Two different molecules (A and B) are the same size and both are polar molecules. Neither molecule diffuses easily through a lipid bilayer, but both have transport proteins for their specific import into cells. Molecule A is transported into cells at a rate that is approximately 1000 times faster than molecule B, even when their concentration gradients are identical. Using your understanding of membrane transport, offer an explanation for the difference in the rates of transport of the two molecules.

Answer 11

• One molecule will move so much faster than the other because one could be a channel and a carrier
• Channel protein would be moving very fast
• Carrier protein would take more time

Question 12

How are pinocytosis and phagocytosis similar? How are they different?

Answer 12

Phagocytosis is when cytoplasmic extension reach debris and is brought into the cell to create a vacuole

Pinocytosis is when the cell membrane creates a pouch and folds to go around extracellular liquid then the cell takes it in. Mainly used to bring in lipids.

Question 13

What happens to the surface area of a cell during exocytosis? Explain.

Answer 13

• The surface area increases as things get pushed out of the cell
• When the cell reaches out to bring in substances, it will increase the surface area