Bio Chapter 2 - Movement of Substances

Question 1

What is the definition of diffusion

Answer 1

Diffusion is the het movement of particles from a region of higher concentration to a region of lower concentration that is, down a concentration gradient, not requiring a membrane

Question 2

Name two examples of diffusion occurring

Answer 2

Gaseous exchange in human lungs
Gaseous exchange in leaves

Question 3

How does diffusion occur in the gaseous exchange in human lungs?

Answer 3

Oxygen diffuses into the bloodin the blood capillaries from the alveolus, small air sacs surrounded by a network of blood capillaries
Carbon dioxide diffuses out of the blood capillaries to the alveolus

Question 4

How does diffusion occur during photosynthesis

Answer 4

When plants photosynthesise,
There is a net movement of carbon dioxide into the leaf from the atmosphere
Het movement of oxygen and water vapour out of leaf to the atmosphere

Question 5

How does diffusion our when plants are not photosynthesising

Answer 5

Net movement of oxygen into leaf from the atmosphere
Net movement of carbon dioxide and water vapour out the leaf to the atmosphere

Question 6

What are the three factors that affect the rate of diffusion and osmosis?

Answer 6

Diffusion/ osmosis distance
Concentration / water potential gradient
Surface area to volume ratio

Question 7

What is the relationship between diffusion/ osmosis distance and the rate of diffusion/osmosis

Answer 7

The shorter the diffusion/osmosis distance, the higher the rate of diffusion

Question 8

Name and describe an example of short diffusion distance

Answer 8

Cells in the wall of the alveolussome one cell thick, decreasing diffusion distance that carbon dioxide molecules have to pass through from blood capillaries to the alveolus
And for oxygen molecules to pass through from alveolus into blood capillaries
Thus, increasing rate of diffusion of carbon dioxide and oxygen

Question 9

What is the relationship between surface areato volume ratio and the rate of diffusion / osmosis

Answer 9

The greater the surfaceareato volume ratio, the higher the rate of diffusion / osmosis

Question 10

Name and describe an example of increased surface area to volume ratio increasing the rate of diffusion

Answer 10

The epithelial cell has microvilli that helps to increase rate of digested nutrients from small intestine into the cell by increasing surface area to volume ratio

Question 11

What is the relationship between the concentration of particles / water potential and the rate of diffusion/osmosis

Answer 11

The greater the difference in concentration of particles / water potential, the faster the rate of diffusion

Question 12

What is the definition osmosis

Answer 12

The net movement of watermorelures from a solution of higher water potential to a solution lower potential , through a partially permeable membrane, that is, down a water potential gradient

Question 13

What is water potential?

Answer 13

Measure of tendency of water molecules to move from one place to another down a water potential gradient

Question 14

What happens when a plant cell is placed in a solution of higher water potential

Answer 14

The cell sap has a lower water potential than that of the external solution
By osmosis, water molecules enter the cell through the partially permeable cell membrane
As water molecules enter the cell, vacuole increases in size and pushes the cytoplasm against the cell wall
The cell does not burst as it is protected by inelastic cell wall
As a result, the cell expands and becomes turgid

Question 15

What happens when a plant cell is placed in a solution of lower water potential

Answer 15

The cell sap has a higher water potential than the external solution
By osmosis, water molecules from the vacuole and cytoplasm leave the cell through the partially permeable cell membrane

Plasmolysis occurs where as the cell loses water, vacuoles decreases in size and cytoplasm shrinks away from cell membrane.
As a result, the cell decreases in size and becomes flaccid or limp

Question 16

What happens when an animal cell is placed in a solution of higher water potential

Answer 16

The cytoplasm has a lower water potential than the solution outside the cell
Water molecules more into the cell by osmosis
Animal cell will swell and may burst because unlike plants, animal cells do not have cell walls to protect them

Question 17

What happens when an animal cell is placed in a solution of lower water potential

Answer 17

The cytoplasm has a higher water potential than the external solution
Water molecules move out of the cell by osmosis
Cremation occurs where animal cell shrinks and spikes appear on the cell surface
The cell will become dehydrated and eventually die

Question 18

Why is turgor important in plants?

Answer 18

Young stems and leaves of herbaceous and non-woody plants are able to remain firm and erect because of turgor pressure within the cell

When there is a high rate of water loss, cells will lose turgidity and the plant will eventually wilt

Question 19

Why is it not advisable to add excessive fertiliser around roots?

Answer 19

The soil solution will become very concentrated as water molecules leaving the roots by osmosis

Question 20

What will happen if the roots are unable to absorb water while there is continued evaporation of water from leaves

Answer 20

Unless sufficient water is added to dilute the soil solution, the plant will eventually wilt