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7.2. Transport mechanisms
A subsection of Biology, 9700, through 7. Transport in plants
Listing 10 of 310 questions
Phloem sieve tube elements and xylem vessel elements are cells that are involved with the transport of substances in plants. Describe two differences between the structure of a phloem sieve tube element and a xylem vessel element. Sucrose is transported in phloem sieve tubes. A student carried out a test to identify the presence of sucrose in a sample of sap taken from inside a phloem sieve tube. One of the steps in the procedure instructed the student to heat the phloem sap with hydrochloric acid. Explain why it is necessary to carry out this step in the procedure. The process of loading sucrose into a phloem sieve tube element involves a companion cell. shows a stage in the process of loading sucrose into the phloem. cell surface membrane of companion cell H+ H+ cytoplasm of companion cell cellulose cell wall of companion cell not to scale ATP ADP + Pi Companion cells contain large numbers of mitochondria and ribosomes. Explain the roles of mitochondria and ribosomes for the stage shown in . Describe and explain how sucrose is transported from the cell wall of the companion cell into the cytoplasm.
9700_s19_qp_23
THEORY
2019
Paper 2, Variant 3
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Questions Discovered
310