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Plants, cell communication, digestion, and circulation

  1. Nov 8, 2007 #1
    1. The problem statement, all variables and given/known data
    I would like to have some of my homework problems checked. I looked in the book, and answered these the best I could. My answers are in bold. Thanks in advance for the help!

    2. Relevant equations

    3. The attempt at a solution

    1. Which functional plant cells lack a nucleus?

    a. xylem only
    b. sieve cells only
    c. companion cells only
    d. both companion and parenchyma cells
    d. both xylem and sieve-tube cells

    2. Additional vascular tissue produced as secondary growth in a root originates from which cells?

    a. vascular cambium
    b. apical meristem
    c. endodermis
    d. phloem
    e. xylem

    3. Phloem transport is described as being from source to sink. Which of the following would most accurately complete this statement about phloem transport as applied to most plans in the late spring? Phloem transports ___ from the ___ source to the ___ sink

    a. amino acids, root, root
    b. sugars, leaf, apical meristem
    c. nucleic acids, flower, root
    d. proteins, root, leaf
    e. sugars, stem, root

    4. A researcher is studying the signaling pathway of a hormone involved in regulating the sleep cycle. He discovers that the pathway utilizes a G-protein that when activated, promotes the activation of phospholipase C, an enzyme that cleaves inositol bisphosphate into diacylglycerol and inositol trisphosphate. Which of the following statements is most likely to be true?

    a. The ligand is water soluble and the receptor is on the plasma membrane.
    b. The ligand is not water soluble and the receptor is in the nucleus.
    c. The ligand freely circulates throughout the body and the receptor is in the nucleus.
    d. The ligand signals at close range and the receptor spans the membrane one time.
    e. The ligand freely circulates throughout the body and the receptor spans the membrane seven times.

    5. A drug designed to inhibit the response of cells to estrogen would almost certainly result in which of the following?

    a. lower cytoplasmic levels of cAMP
    b. an increase in receptor tyrosine kinase activity
    c. a change in transcriptional activity of certain genes
    d. an increase in cytosolic calcium concentration
    e. a decrease in G-protein activity

    6. Which of the following would most directly be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?

    a. G-protein-linked receptor signaling
    b. ligand-gated ion channel signaling
    c. adenylyl cyclase activity
    d. phosphatase activity
    e. receptor tyrosine kinase activity

    7. Without functioning parietal cells, an individual would

    a. not be able to initiate protein digestion in the stomach
    b. not be able to initiate mechanical digestion in the stomach
    c. only be able to digest fat in the stomach
    d. not be able to produce pepsinogen
    e. not be able to initiate digestion in the small intestine

    8. According to the laws of diffusion, if a substance requires 3 seconds to diffuse 10 mm, how long will it take to diffuse 20 mm?

    a. 3
    b. 6
    c. 9
    d. 12
    e. 27

    9. Supposing that you had a pipe that had a radius of 1 meter and you split (or bifurcate) the water flowing from this pipe into 10 pies, each with a radius of 0.1 meters. Which of the pies will have water moving at the greatest velocity?

    a. the large pipe (radius 1 meter)
    b. neither because the velocity will be the same in the large pipe as in the small pipes
    c. any of the small pipes (radius 0.1 meters)

    10. The Bohr shift on the oxygen-hemoglobin dissociation curve is produced by changes in

    a. the partial pressure of oxygen
    b. the partial pressure of carbon monoxide
    c. hemoglobin concentration
    d. temperature
    e. pH
  2. jcsd
  3. Nov 9, 2007 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    I'll just start with two to help you get on the right track, but you should explain WHY you chose your other answers before getting more help.

    For question 3, what is the function of each part of the plant? The flower, leaf, stem, root, and apical meristem? Which is most likely to be a source of nutrients, and which a sink (i.e., storage site)?

    For question 4, note that the ligand is a g-protein. Where do you usually find g-protein coupled receptors?
  4. Nov 9, 2007 #3
    First of all, after posting this, I changed the last few answers, with the corrected problems as:


    To answer your questions:
    For question 3, the leaf has photosynthetic pigments, producing sugars. The sugars are transferred from the leaf to the root through the stem. So going through this, my answer should now be E. For question 4, g-protein coupled receptors are usually found in the cytosol?
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