Chapter 1 - diffusion, active transport, osmosis

Question 1

What is the definition of diffusion

Answer 1

The net movement of particles from a region of higher concentration to lower concentration down a concentration gradient, as a result of their random movement

Question 2

Where does the energy for diffusion come from

Answer 2

The kinetic energy of the random movement of molecules and ions

Question 3

What is the importance of the diffusion of gases and solutes

Answer 3

Diffusion helps living organisms

• Obtain many of their requirements
• Get rid of many of their waste products
• gas exchange for respiration

Question 4

How do substances move in and out of cells

Answer 4

Via diffusion through the cell membrane

Question 5

What factors influence diffusion

Answer 5

• tempurature
• surface area
• distance
• concentration gradient

Question 6

Definition of active transport

Answer 6

The movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration

Question 7

When is active transport used

Answer 7

• By root hair cells to move ions from soil into root hair cells when the concentration of ions is higher in the hair than the soil
• By eptihelial cells of the villi in the ileum of humans to move glucose from the intestine into the blood
• By the cells lining kidney tubules to move glucose from the contents of the tubule back into the blood

Question 8

How do protein molecules move particles across a membrane during active transport

Answer 8

• Ions move across the membrane through a protein molecule
• The ion binds to the protein
• The energy from respiration is used to make the protein change shape
• The moves the ion across the cell membrane

Question 9

What diffuses through a partially permeable membrane during osmosis

Answer 9

Water molecules

Question 10

Definition of osmosis

Answer 10

The net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water ptoential (concentrated solution), through a partially permeable membrane

Question 11

How does water move in and out of cells

Answer 11

By osmosis through a cell membrane

Question 12

What is a turgid cell

Answer 12

• A cell that has taken up water by osmosis
• The contents of the cell press out on its walls; this is called turgor pressure
• The cell walls cannot stretch, so the turgidity of the cell helps support the soft parts of the plant, like leaves and flower petals

Question 13

What is a flaccid cell

Answer 13

• A cell that has lost water by osmosis
• When this occurs the contents of the cell shrink so much that the cell membrane pulls away from the cell wall; the cell is said to be plasmolysed

Question 14

What happens when a plant tissue is immersed in a solution with a higher concentration of ions

Answer 14

• Water moves out of cell by osmosis
• cotnets of the cells shrink back from the cell walll
• The cell is plasmolysed, the cell s irreversibly damaged and dies often

Question 15

What happens when a plant tissue is immersed in a solution with a lower concentration of ions

Answer 15

• Water moves into the cell via osmosis
• Contents of the cell push out on the walls; this is turgor pressure)
• Cell is turgid

Question 16

What are plants supported by

Answer 16

• Turgor pressure - contents of cells pushing out on the walls

Question 17

How are plants supported by turgor pressure

Answer 17

• Contents of cells push out on an inelastic wall
• Therefore pressure from the contents of the cells pushing out increases turgor pressure