T1 - transport in cells

Question 1

Define the term diffusion.

Answer 1

Diffusion is the spreading out of particles in a solution or a gas, resulting in net movement of particles from a region of higher concentration to a region of lower concentration.

Question 2

What is a concentration gradient?

Answer 2

A concentration gradient is a difference in concentration between two regions.

Question 3

True or False? Diffusion is an active process.

Answer 3

False. Diffusion is a passive process that occurs when molecules spread out due to their random movement.

Question 4

What is a partially permeable cell membrane?

Answer 4

A partially permeable cell membrane allows some substances to pass through while preventing others from entering or leaving a cell.

Question 5

Name an example of diffusion that takes place in the human lungs.

Answer 5

Examples of diffusion in the lungs include: oxygen diffuses from the inhaled air into the blood through the alveolar lining, carbon dioxide diffuses from the blood into the exhaled air through the alveolar lining.

Question 6

True or False? The waste product urea diffuses from body cells into the blood.

Answer 6

True. Urea is a metabolic waste product produced in the cells. It diffuses into the blood before being excreted by the kidneys.

Question 7

What is the relationship between surface area and rate of diffusion into a cell?

Answer 7

As surface area to volume ratio increases, so does the rate of diffusion (and vice versa). This is because a larger surface area provides more space across which diffusion can occur.

Question 8

What is the effect of increasing temperature on the movement of particles?

Answer 8

At higher temperatures particles move around faster; this is because they have more kinetic energy.

Question 9

True or False? Increasing temperature decreases the rate of diffusion.

Answer 9

False. As temperature increases, the rate of diffusion also increases. Molecules move around faster at higher temperatures, resulting in faster diffusion.

Question 10

True or False? Increasing the concentration gradient will increase the rate of diffusion.

Answer 10

True. As concentration gradient increases the rate of diffusion also increases.

Question 11

Define the phrase surface area to volume ratio.

Answer 11

Surface area to volume ratio is the surface area of an object in relation to its volume.

Question 12

What happens to the surface area to volume ratio as cell size increases?

Answer 12

As cell size increases the surface area to volume ratio decreases.

Question 13

Why do multicellular organisms need exchange surfaces and transport systems?

Answer 13

Multicellular organisms need exchange surfaces because their small surface area to volume ratio means that exchange of substances at their body surface is too slow to meet their needs. Multicellular organisms need transport systems because of their large volume; their bodies contain many layers of cells, meaning that internal transport by diffusion alone is too slow.

Question 14

What are the features of an efficient exchange surface?

Answer 14

Features of an exchange surface include: A large surface area, A thin barrier / short diffusion distance, A steep concentration gradient, maintained by having a good blood supply and a good supply of required substances.

Question 15

True or False? The alveoli provide an exchange surface in mammals.

Answer 15

True. The alveoli provide an exchange surface for gas exchange between the lungs and the blood.

Question 16

How do the alveoli aid gas exchange?

Answer 16

Alveoli facilitate gas exchange as follows: They have a large surface area, Their walls are thin, They have a good blood supply, They are well ventilated. These are all features of an efficient exchange surface.

Question 17

What is the function of stomata in leaves?

Answer 17

Stomata are tiny openings that allow air to move in and out of leaves. This decreases the diffusion distance for gas exchange inside the leaf.

Question 18

What is the name of the leaf cell type across which gas exchange occurs inside leaves?

Answer 18

Gas exchange occurs between the leaf air spaces and the interior of the spongy mesophyll cells.

Question 19

How are fish gills adapted for efficient gas exchange?

Answer 19

Fish gills are adapted for gas exchange as follows: Many filaments covered in lamellae increase the surface area, A dense capillary network maintains concentration gradients.

Question 20

True or False? Villi in the small intestine of mammals have a large surface area but are not well supplied with blood.

Answer 20

False. The villi in the small intestine do have a large surface area, but they also have a good blood supply to maintain a steep concentration gradient between the intestine and the blood.

Question 21

Define the term osmosis.

Answer 21

Osmosis is the diffusion of water molecules from a region of higher water concentration (dilute solution) to a region of lower water concentration (concentrated solution), through a partially permeable membrane.

Question 22

True or False? Only water can move by osmosis.

Answer 22

True. Only water can be transported by osmosis.

Question 23

What type of concentration difference leads to osmosis?

Answer 23

The type of concentration difference that leads to osmosis is a difference in water concentration between two regions. This can also be referred to as water potential.

Question 24

True or False? Osmosis only occurs across a partially permeable membrane.

Answer 24

True. Osmosis must take place across a partially permeable membrane. If water moves in any other way, e.g. water vapour moving out of a leaf via the stomata, this is diffusion.

Question 25

Define the term dependent variable.

Answer 25

The dependent variable is the variable that is measured during an investigation.

Question 26

What is the independent variable in the practical that investigates osmosis using potato cylinders?

Answer 26

The independent variable in the osmosis and potato practical is the solute concentration of the solution in which the potato cylinders are placed.

Question 27

In the osmosis and potato practical, why is it important to dry the potato cylinders before weighing?

Answer 27

The potato cylinders are blotted with paper towels before weighing to remove any surface water that could affect the mass measurement.

Question 28

Why is it important that all pieces of potato have the same surface area when measuring the effect of concentration of salt or sugar solution on the mass of plant tissue?

Answer 28

It is important that all pieces of potato have the same surface area when measuring the effect of concentration of a solution on the mass of plant tissue because surface area affects osmosis, so differences in the surface area of the potato pieces would affect the results.

Question 29

True or False? Potato cylinders placed in distilled water should gain mass due to osmosis.

Answer 29

True. Potato cylinders placed in distilled water will gain mass due to the movement of water into the cells by osmosis. This will occur because distilled water has a higher water concentration than potato cell cytoplasm.

Question 30

Give one example of a control variable in the osmosis and potato practical.

Answer 30

Examples of control variables in the osmosis and potato practical include: Volume of (e.g. sucrose) solution, Surface area of potato cylinders, Potato cylinders are all thoroughly dried before weighing, Potato cylinders are left in the solutions for the same length of time.

Question 31

True or False? When a potato cylinder placed in a sucrose solution does not change in mass, this indicates no overall movement of water.

Answer 31

True. If a potato cylinder does not change mass this indicates that the solution has the same water concentration as the cell cytoplasm, so there is no overall movement of water by osmosis.

Question 32

What is the purpose of repeating the osmosis experiment with multiple potato cylinders?

Answer 32

Repeating the experiment with multiple potato cylinders allows for the identification and exclusion of anomalous results when calculating the mean.

Question 33

What is the equation used to calculate the percentage change in mass for each potato cylinder?

Answer 33

The equation used to calculate the percentage change in mass for each potato cylinder is: percent change in mass = ((final mass - initial mass) / initial mass) * 100.

Question 34

When plotting a graph of the results of the osmosis and potato experiment, how can the concentration of sugar/salt inside the potato cells be estimated?

Answer 34

The concentration of sugar/salt inside the potato cells can be estimated by identifying where the line of best fit crosses the x-axis.

Question 35

Define the term active transport.

Answer 35

Active transport is the movement of particles across a cell membrane from a region of lower concentration to a region of higher concentration; this requires energy.

Question 36

True or False? Active transport is the movement of particles down a concentration gradient.

Answer 36

False. Active transport moves particles against a concentration gradient.

Question 37

Which cellular process releases energy for active transport?

Answer 37

Energy for active transport is released during the cellular process of respiration.

Question 38

Why do root hair cells use active transport?

Answer 38

Root hair cells use active transport to move mineral ions from a region of lower concentration in the soil to a region of higher concentration inside the cell cytoplasm.

Question 39

How does active transport aid glucose absorption in the small intestine?

Answer 39

Active transport allows glucose to be transported into the bloodstream from the lumen of the small intestine when the concentration of glucose in the blood is higher than that in the intestine.

Question 40

Compare the energy requirements of diffusion, active transport and osmosis.

Answer 40

The energy requirements of diffusion, active transport and osmosis can be compared as follows: Diffusion and osmosis are both passive processes that do not require energy, Active transport does require energy.

Question 41

How do diffusion, active transport and osmosis differ in terms of concentration gradients?

Answer 41

Diffusion, active transport and osmosis differ in terms of concentration gradients as follows: Diffusion and osmosis move substances down a concentration gradient, from higher to lower concentration, Active transport moves substances against a concentration gradient, from lower to higher concentration.

Question 42

Which cell transport mechanism(s) can only take place across a cell membrane?

Answer 42

Cell transport mechanisms that can only take place across a cell membrane are: Osmosis, Active transport, Diffusion can occur across a cell membrane, but can also occur in the absence of a membrane.