Answer: alternative D.
Explanation: For the DNA to have the double strand structure, it is necessary to copy the sequence of the existing DNA strand in a complementary sequence of nucleotides, forming hydrogen bonds between them. The mRNA also uses this strategy when reading the DNA strand during the transcription, in order for the translation to begin.
- Xylem contains tracheids, vessels, xylem parenchyma and xylem fibre.
- Tracheids: They are elongated, tubular dead cells with tapering end walls.
- Vessels: These are also known as trachea. They are elongated, tubular dead cells. They are joined to each other by end to end forming a continuous pipe. The cells are thick and lignified.
- Xylem parenchyma: They are also called wood parenchyma. This is the only living tissue of xylem.
- Xylem fibre: They are dead cells with thick walled fibre.
- Phloem consists of sieve tubes, companion cells, phloem parenchyma and phloem fibres.
- Sieve tubes: These are elongated, tubular living cells arranged in a row, with their perforated end walls forming a sieve. They are non-nucleated. Their protoplasm are inter-connected through sieve plates. They possess vacuoles.
- Companion cell: They are elongated, lens-shaped cells containing dense cytoplasm and prominent nuclei. These cells maintain connection with sieve cells through pits.
- Phloem parenchyma: They are living thin walled parenchyma cells.
- Phloem fibre: They are also known as bast fibre. They are elongated fibre like sclerenchymatous dead cells with thick walls containing pits and interlocked ends. Phloem fibre are the only dead cells in phloem.
Hope you could get an idea from here.
Doubt clarification - use comment section.
Speciation will only occur if there was life in the area before like a bunrt down forest or soemthing similar
Answer:
1. Part A: No
2. Part B: Yes
3: Part C : Yes
4: Part D : No
Explanation:
1) Part A: Facilitated diffusion of glucose into a muscle cell:
No; sodium ion co - transport is required for active transport of glucose but not for facilitated diffusion of glucose
2) Part B: Active transport of dietary phenylalanine across the intestinal mucosa:
Yes; co - transport of sodium ions drives the inward movement of amino acids and can only occur if sodium ions are actively pumped back out again.
3) Part C: Uptake of potassium ions by red blood cells:
Yes; uptake of potassium ions can occur only via a pump that couples the inward pumping of potassium ions to the outward pumping of sodium ions.
4) Part D: Active uptake of lactose by the bacteria in your intestine
No; active uptake of sugars and amino acids in bacteria is driven by a proton gradient.
