Topic 11 - Learning Objectives

Question 1

1. List the requirements for cellular respiration and photosynthesis within plant tissues. #understand

Answer 1

• Cellular Respiration: Requires oxygen, glucose, and enzymes. It occurs in mitochondria.
• Photosynthesis: Requires carbon dioxide, water, light energy, and chlorophyll. It occurs in chloroplasts.

Question 2

1. a) Explain how cellular respiration and photosynthesis are interconnected. #evaluate

Answer 2

• Cellular respiration produces carbon dioxide as a byproduct, which is utilized in photosynthesis to produce glucose.
• Photosynthesis produces oxygen as a byproduct, which is used in cellular respiration to generate energy.

Question 3

1. b) List the plant tissues/organs in which each process occurs. #understand

Answer 3

• Cellular respiration occurs in all plant cells, particularly in mitochondria.
• Photosynthesis primarily occurs in chloroplast-containing cells, mainly in leaves, but also in stems and other green tissues.

Question 4

2. Describe the three routes water can move within a plant tissue and the levels of control with each. #analyze

Answer 4

• Apoplast Route: Water moves through cell walls and intercellular spaces without entering the cytoplasm. It is controlled by the permeability of cell walls.
• Symplast Route: Water moves through the cytoplasm via plasmodesmata, connecting adjacent cells. It is controlled by the regulation of plasmodesmata.
• Transmembrane Route: Water crosses cell membranes, passing through the cytoplasm of each cell. It is controlled by the permeability of cell membranes.

Question 5

3. Explain the mechanisms of solute transport across plant cell membranes. #understand

Answer 5

• Active Transport:
  Uses energy to move solutes against their concentration gradient, often involving transport proteins like ATPases.
• Passive Transport:
  Allows solutes to move down their concentration gradient without energy input, including diffusion and facilitated diffusion through channels or carriers.

Question 6

4. Explain how water potential is used to predict the movement of water by osmosis. #apply

Answer 6

• Water potential predicts the direction of water movement, with water moving from regions of higher water potential to lower water potential.

Question 7

4. a) Explain how water potential creates turgor in plants. #apply

Answer 7

• Turgor pressure is created by the pressure exerted by the cell contents against the cell wall due to water uptake, maintaining cell rigidity

Question 8

5. Describe how the endodermis regulates water flow into the vascular cylinder (stele). #analyze

Answer 8

• The endodermis contains the Casparian strip, a band of suberin that blocks water and solutes, regulating their entry into the stele.
• Water and solutes must pass through the selectively permeable plasma membranes of endodermal cells before entering the vascular cylinder.

Question 9

6. Explain how root pressure contributes to xylem transport. #analyze

Answer 9

• Root pressure results from osmotic uptake of water by root cells, creating positive pressure in the xylem.
• This pressure can push water up the xylem, especially in small plants or during periods of high root activity.

Question 10

7. Explain how the cohesion-tension mechanism contributes to xylem transport. #evaluate

Answer 10

• Transpiration at leaf surfaces creates negative pressure (tension) in the xylem, pulling water upwards.
• Cohesion between water molecules and adhesion to xylem walls allow for the continuous column of water to be pulled up through the xylem

Question 11

7. a) Describe how the cohesion-tension mechanism is regulated through the opening and closing of stomata. #apply

Answer 11

• Stomatal opening and closing regulate transpiration rates, affecting the tension in the xylem and thus water transport

Question 12

8. Explain the pressure-flow hypothesis describing how phloem sap moves. #evaluate

Answer 12

• Sugars produced in source tissues (e.g., leaves) are actively transported into the phloem.
• This creates a pressure gradient, causing phloem sap to flow from sources (high pressure) to sinks (low pressure), where sugars are used or stored.

Question 13

8. a) Identify sources and sinks in plants. #understand

Answer 13

• Sources:
  Regions of the plant where sugars are produced (e.g., leaves during photosynthesis).
• Sinks:
  Regions of the plant where sugars are used or stored (e.g., growing roots, developing fruits).

Question 14

9. Diagram and describe the mechanisms of nutrient/water uptake by root cells. #analyze

Answer 14

• Root hairs increase surface area for absorption by creating a thin film of water around them.
• Active transport and passive diffusion move ions and water across cell membranes into the root’s vascular cylinder.

Question 15

10. Identify adaptations that plants may have to acquire nutrients without photosynthesis. #understand

Answer 15

• Mycorrhizal associations increase the surface area for nutrient uptake by forming symbiotic relationships with fungi.
• Parasitic plants obtain nutrients from host plants through specialized structures such as haustoria.

Question 16

Symplast

Answer 16

The interconnected network of living plant cells joined by plasmodesmata, allowing for the movement of water, ions, and small molecules between cells.

Question 17

Apoplast

Answer 17

The extracellular space outside the plasma membranes of plant cells, consisting of cell walls, intercellular spaces, and the continuous network of cell walls through which water and solutes can move freely.

Question 18

Transmembrane

Answer 18

Across or spanning a membrane, referring to molecules or processes that pass through both the lipid bilayer and membrane proteins.

Question 19

Passive transport

Answer 19

The movement of ions or molecules across a membrane down their concentration gradient, requiring no energy input.

Question 19

Primary active transport

Answer 19

The movement of ions or molecules across a membrane against their concentration gradient using energy derived directly from ATP hydrolysis.

Question 20

Secondary active transport

Answer 20

The movement of ions or molecules across a membrane driven by the electrochemical gradient established by primary active transport.

Question 21

Osmosis

Answer 21

The movement of water across a selectively permeable membrane from an area of higher water concentration (lower solute concentration) to an area of lower water concentration (higher solute concentration).

Question 22

Bulk flow

Answer 22

The movement of water and solutes together in response to a pressure gradient, typically occurring in the xylem and phloem of plants.

Question 23

Water potential

Answer 23

The potential energy of water in a particular environment or system, determined by its pressure potential and solute potential.

Question 24

Solute potential

Answer 24

The component of water potential determined by the concentration of solutes in a solution, representing the effect of solute concentration on water movement.

Question 25

Endodermis

Answer 25

The innermost layer of cells in the root cortex of plants, characterized by the presence of the Casparian strip and playing a role in regulating the movement of water and ions into the vascular tissue.

Question 26

Pressure potential

Answer 26

The component of water potential determined by the physical pressure exerted on a solution, representing the effect of pressure on water movement.

Question 27

Positive pressure

Answer 27

Pressure exerted on a solution that pushes water out of the cell, potentially causing turgor pressure in plant cells.

Question 28

Negative pressure

Answer 28

Pressure exerted on a solution that pulls water into the cell, often caused by osmotic potential or transpiration in plants.

Question 29

Stoma(ta)

Answer 29

Small pores on the surface of leaves and stems of plants, surrounded by two guard cells, through which gas exchange and water vapor transpiration occur.

Question 30

Guard cell

Answer 30

Specialized cells surrounding the stomata in plant leaves and stems, regulating the opening and closing of the stomatal pore to control gas exchange and water loss.

Question 31

Aquaporin

Answer 31

Protein channels embedded in the cell membrane that facilitate the transport of water molecules across the membrane.

Question 32

Source

Answer 32

A part of a plant that produces or releases organic compounds, such as sugars, for use by the plant or for export to other parts.

Question 33

Nodule

Answer 33

A specialized structure formed on the roots of certain plants, such as legumes, hosting nitrogen-fixing bacteria that convert atmospheric nitrogen into a form usable by the plant.

Question 34

Sink

Answer 34

A part of a plant that consumes or stores organic compounds, such as sugars, for growth, storage, or other metabolic processes.

Question 35

Root hair

Answer 35

Slender outgrowths of epidermal cells near the tips of plant roots, increasing the surface area for absorption of water and nutrients from the soil.

Question 36

Epiphyte

Answer 36

A plant that grows on the surface of another plant, typically trees, using them for support while obtaining moisture and nutrients from the air and rain.

Question 37

Parasite

Answer 37

An organism that lives on or in another organism (the host), obtaining nutrients and resources at the expense of the host’s health or survival.