There are at least three different types of companion cells in the minor veins of mature, exporting leaves. Which of the following statements about these companion cells is CORRECT?

 a.) transfer cells are transport sugars enter the apoplast during the movement of sugars from mesophyll cells to sieve elements. Transfer cells transport sugars from the apoplast to the symplast of the sieve elements and companion cells in the source.

 b.) the numerous mitochondria in companion cells may supply energy as ATP to the sieve elements

 c.) Ordinary companion cells can function in either symplastic or apoplastic short-distance transport in source leaves, depending in part on plasmodesmatal frequencies

 d.) Intermediary cells, by contrast, function in symplastic transport of sugars from mesophyll cells to sieve elements

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#Question id: 2196

#Unit 2. Cellular Organization

Substance X is a charged molecule of small molecular weight. It is found at higher concentrations outside of cells than inside. How might substance X enter cells?

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#Question id: 11019

#Unit 7. System Physiology – Animal

An 80-year-old man had an EKG taken at his local doctor’s office, and the diagnosis was atrial fibrillation. Which of the following statements are likely conditions in someone with atrial fibrillation?

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#Question id: 20025

#Unit 13. Methods in Biology

For the precipitation will require the antibody must be

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#Question id: 15420

#Unit 5. Developmental Biology

signal from the inducing cell is necessary for initiating new gene expression in the responding cell. Without the inducing cell, the responding cell is not capable of differentiating in that particular way, phenomena known as:

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#Question id: 481

#Unit 1. Molecules and their Interaction Relevant to Biology

In the phosphoglycerate mutase reaction, the side chain of which amino acid in the enzyme is transiently phosphorylated as part of the reaction?