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Draw a large labelled diagram of a transverse section through a young root - Leaving Cert Biology - Question c - 2008
Question c
Draw a large labelled diagram of a transverse section through a young root. Water enters the outermost cells of the root by osmosis. What does this tell you about t... show full transcript
Worked Solution & Example Answer:Draw a large labelled diagram of a transverse section through a young root - Leaving Cert Biology - Question c - 2008
Step 1
Draw a large labelled diagram of a transverse section through a young root.
Answer
To draw a transverse section through a young root, start by sketching an oval shape to represent the cross-section. Divide the oval into three distinct regions:
- Dermal Tissue: This is the outer layer of the root and acts as a protective cover.
- Ground Tissue: Located beneath the dermal tissue, it is responsible for storage and photosynthesis.
- Vascular Tissue: Located at the center, this includes xylem and phloem, which are responsible for transport of water and nutrients.
Label each of these parts clearly on your diagram.
Step 2
Water enters the outermost cells of the root by osmosis. What does this tell you about the cell sap of these outermost cells?
Answer
The fact that water enters the outermost cells of the root by osmosis suggests that the cell sap of these cells has a higher solute concentration compared to the surrounding soil solution. This difference in concentration causes water to move from an area of lower solute concentration (i.e., the soil) to an area of higher solute concentration (the cell sap) in order to achieve equilibrium.
Step 3
Osmosis has been described as a special case of diffusion. Explain why.
Answer
Osmosis is considered a special case of diffusion because it specifically refers to the movement of water molecules across a selectively permeable membrane. Unlike general diffusion, which can involve various types of molecules moving from an area of higher concentration to an area of lower concentration, osmosis deals exclusively with water movement. It occurs along a concentration gradient and is driven by differences in solute concentration on either side of the membrane.
Step 4
Describe an investigation that you carried out to demonstrate osmosis.
Answer
To demonstrate osmosis, one simple investigation involves using a potato. Cut potato tubers into equal-sized pieces and rinse them in pure water. Prepare two solutions: one with a high salt concentration and the other with pure water.
Soak one set of potato pieces in the salt solution and another set in the pure water for a few hours. Measure the change in mass of the potato pieces.
The potato pieces immersed in the salt solution will lose mass due to water moving out of the potato cells (osmosis). Conversely, the pieces in pure water will gain mass as water moves into the cells.
Step 5
Describe how minerals such as nitrates enter the root of a plant from the soil.
Answer
Minerals like nitrates enter the roots of plants primarily through active transport processes. The root hairs, which increase surface area for absorption, absorb nitrates from the soil solution. These minerals often exist in low concentrations in the soil compared to the inside of the root cells. Therefore, plant roots use energy to actively transport these minerals against their concentration gradient, ensuring that plants can obtain essential nutrients necessary for growth.