Diffusion, Osmosis, and Other Transport Processes

Question 1

What does Graham’s law of Diffusion state?

Answer 1

The rates of diffusion is inversely proportional to the square root of their densities.

Question 2

Given that HCl is denser than NH4, which of the two will diffuse faster?

Answer 2

Ammonia because it is less dense.

Question 3

Why are air pumps used in aquariums?

Answer 3

Because oxygen is more soluble in air compared to water. Hence, air pumps are used so that the substance would diffuse faster.

Question 4

What is the effect of the presence of other types of molecules on the direction of diffusion?

Answer 4

No effect

Question 5

What is the effect of the presence of other types of molecules on the rate of diffusion?

Answer 5

The presence of other types of molecules decreases the rate of diffusion because of the additional collisions that will occur.

Question 6

This refers to the net movement of molecules from a region of high concentration to a region of low concentration through random thermal motion of individual molecules.

Answer 6

Diffusion

Question 7

Is there diffusion in the state of dynamic equilibrium?

Answer 7

Yes, diffusion still continues in dynamic equilibrium but in a CONSTANT rate. However, there is no net diffusion.

Question 8

An increase in temperature results in a/an ___________ in the rate of diffusion

Answer 8

Increase due to the increase of kinetic activity of molecules

Question 9

How does the concentration gradient affect the rate of diffusion?

Answer 9

An increase in concentration (steeper gradient) will result in having n increased rate of diffusion.

Question 10

This refers to the net diffusion of WATER through a differentially permeable membrane from a region of higher water concentration to a region of low water concentration.

Answer 10

Osmosis.

Question 11

What happens to an animal cell in a hypotonic environment?

Answer 11

Lyse because animals do not have cell walls.

Question 12

What happens to an animal cell in a hypertonic environment?

Answer 12

Shrivel and die

Question 13

What type of solution does an animal cell prefer?

Answer 13

Isotonic solution

Question 14

When can you consider a plant cell to be in its turgid state?

Answer 14

When turgor pressure is equal to the wall pressure.

Question 15

What happens to a plant cell when exposed to an isotonic environment?

Answer 15

It becomes flaccid and may wilt.

Question 16

What happens to a plant cell when exposed to a hypertonic solution?

Answer 16

The plant cell becomes plasmolyzed.

Question 17

This refers to the net diffusion of water through a permeable membrane from an area of high free energy to an area of low free energy of water.

Answer 17

Osmosis

Question 18

How does hydrostatic pressure in an osmometer contribute to reaching the state of equilibrium?

Answer 18

It creates a force and this leads to an increase in the free energy of the water contained in the osmometer. As a result, water would tend to push down until such time that it matches the energy of the water from the beaker.

Question 19

What do you call the measure of free energy of water per unit volume?

Answer 19

Water Potential

Question 20

What is the reference standard of water potential?

Answer 20

Pure water because it has a water potential of 0 MPa.

Question 21

How does the presence of solutes affect water potential?

Answer 21

It reduced water potential because it attracts water. Hence, the capacity of water to move is lessened.

Question 22

What are the possible values of pressure potential?

Answer 22

0 or positive

Question 23

What is the positive pressure operating in plant cells?

Answer 23

Wall pressure or turgor pressure

Question 24

What is the positive pressure potential in the osmometer?

Answer 24

Hydrostatic pressure

Question 25

This refers to the component of water potential that is influenced by the presence of surfaces to which water molecules are adhered to.

Answer 25

Matrix Potential

Question 26

What is the formula for computing the solute potential?

Answer 26

Solute potential = -CRiT

Question 27

What do you call the passive movement of molecules down its concentration gradient?

Answer 27

Facilitated Diffusion

Question 28

What do you call the transport protein that has corridors and is usually involved when large quantities of solutes must be transported across the membrane?

Answer 28

Channel Protein

Question 29

Give examples of channel proteins.

Answer 29

1. Potassium Channel
2. Chloride Channel
3. Calcium Channel

Question 30

What do you call the transport protein that is substrate-specific due to its capacity to perform conformational changes?

Answer 30

Transfer/Carrier Protein

Question 31

Why are transfer/carrier proteins slower compared to channel proteins?

Answer 31

The conformational changes that they have to do slows them down.

Question 32

What is the difference between enzymes and transport proteins?

Answer 32

Transport proteins can only catalyze physical processes, not chemical reactions.

Question 33

How do water molecules actually cross the membranes?

Answer 33

Through aquaporins. Though, note that water molecules could still pass through the lipid bilayer due to its small size even if the lipid bilayer has hydrophobic inner membrane.

Question 34

What advantage does the biological membrane have over artificial membranes composed purely of phospholipids?

Answer 34

Biological membranes are much more permeable towards ions since they have transport proteins that facilitate the passage of such ions and other polar molecules.

Question 35

Both biological and artificial membranes have similar permeability towards what molecules?

Answer 35

1. Non polar (CO2, H3O)

2. Uncharged molecules (glycerol)

Question 36

What do you call the type of transport that requires the cell to expend its own energy to pump solutes against their gradients?

Answer 36

Active Transport

Question 37

Why is it important to have active transport?

Answer 37

Active transport is important to maintain the concentration of small molecules inside the cell that would otherwise diffuse across the membrane.

Question 38

What do you call this type of active transport that is directly coupled to an energy source, such as ATP hydrolysis or oxidation-reduction reactions in the ETC?

Answer 38

Primary Active Transport

Question 39

What are the two (2) types of ion pumps in the primary active transport system?

Answer 39

Electroneutral (no net charge involved) and Electrogenic (net charge involved)

Question 40

Is the H/K ATPase electroneutral or electrogenic? Why?

Answer 40

It is electroneutral because it pumps one hydrogen out and one potassium in.

Question 41

What happens when protons are pumped out of the cell causing the H+ concentration to be higher outside compared to the inside?

Answer 41

> A chemical gradient because pH will be less outside compared to the inside.
A electrical gradient (membrane potential) due to more positive charges being outside the cell.

Question 42

Is the Na/K ATPase an electroneutral or electrogenic ion pump?

Answer 42

Electrogenic because it pumps 3 Na out for every 2 K in.

Question 43

What do you call this type of active transport that uses energy stored in the electrochemical gradients to transport substances against their gradient?

Answer 43

Secondary Active Transport

Question 44

What are the two (2) types of secondary active transport?

Answer 44

Symport (same direction) and Antiport (opposite direction)

Question 45

What do you call the concerted movement of groups of molecules en masse, most often in response to a pressure gradient?

Answer 45

Bulk Flow

Question 46

How is bulk flow different from diffusion?

Answer 46

Bulk flow is independent of solution concentration as it relies mainly on pressure.

Question 47

Using the Poiseuille Equation, how can you prove that the vessel element is more efficient in water transport compared to the tracheids?

Answer 47

Poiseuille Equation: Volume Flow Rate = (pir^4)/(8viscosity of liquid).

Since the volume of flow rate is directly proportional to the radius, an increase in radius size would lead to having an increase in volume of flow rate by up to 16 times. Hence, wider diameter (vessel element) is much more efficient.

Question 48

What is the main method for water transport in the xylem?

Answer 48

Bulk flow