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EK Biology questions

Discussion in 'MCAT Study Question Q&A' started by futuredoctor10, Jan 4, 2009.

  1. futuredoctor10

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    "Testosterone is secreted by the seminiferous tubules"
    found on p.265 in EK Biology Content Review Book

    Is this right? I know spermatogenesis, production of sperm, occurs in the seminiferous tubules.

    I know testosterone is synthesized in the testes and also in the adrenal cortex... right? (so within the testes maybe it is made in the seminiferous tubules, I am not sure exactly where tho)

    EK Lec 5 Exam, Q107 on p.213
    The follicle in its earliest stages is called a primordial follicle.
    The primordial follicle most likely contains a:
    B. diploid, primary oocyte

    I know oocytes are arrested at birth in prophase I of meiosis I.
    Females are born with primary oocytes (2n).
    Just before ovulation, this primary oocyte completes meiosis I to become a haploid secondary oocyte :thumbdown:.

    So when this question says "primordial follicle" that means the follicle in its earliest stages before or at birth, so the answer is primary oocyte/diploid?

    When does the "primordial follicle" develop?
    A fully mature follicle would develop after ovulation.
    I wasn't sure when primordial was, thought it was post-ovulation, so I picked haploid, secondary oocyte (C).
     
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  3. Charles_Carmichael

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    Leydig cells synthesize and secrete testosterone but they're not in seminiferous tubules. They're located in the space in between seminiferous tubules. At least, that's what I was taught. And I believe the adrenal cortex doesn't secret testosterone. It secretes the androgens DHEA and androstenedione.

    The primordial follicle is the ovum surrounded by a single layer of granulosa cells; these are what females are born with. The primary follicle occurs during the early stage of the follicular phase and the primary follicle is basically the primordial follicle with additional layers of granulosa cells (ie. these are the ova undergoing growth in the early stage of the follicular phase). The answer of "diploid, primary oocyte" is correct because oocyte has not undergone meiosis yet (because it's still in the early stages of the cycle).
     
  4. futuredoctor10

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    According to EK, the adrenal cortex secretes testosterone [in very low amounts].
    There was some question asking "which of the following might be present in the nucleus of a somatic cell in a pregnant woman?" and the answer was testosterone. The explanation said it is a steroid hormone (thereby would act in the nucleus) and the adrenal cortex secretes testosterone in minor amounts so that could be present.

    Thanks for help on the other questions. Good to know females are born with a form of a follicle, the primordial follicle!
     
  5. Charles_Carmichael

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    Really? Hmmm...the way I learnt it, the zona reticularis cells (in the adrenal cortex) produce DHEA and androstenedione but are lacking the enzyme to convert them to testosterone. So, they secrete DHEA and androstendione into the bloodstream and they are converted to testosterone in the testes and to estrogen in the ovaries. Maybe someone else can confirm this for me. I left all my books at school for break so I can't really check up on this.

    Edit: For the question, it would still make sense if the androgens were converted to testosterone in the pregnant woman. I'm just a bit iffy about their explanation that the adrenal cortex secretes testosterone. Ah well, maybe someone else can shed some light on this. :)
     
    #4 Charles_Carmichael, Jan 5, 2009
    Last edited: Jan 5, 2009
  6. futuredoctor10

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    Maybe EK is wrong...

    Another question of theirs (p. 118, Question 118) says "Which of the following endocrine glands produce testosterone?" and the answer is C) adrenal cortex.
    [Explanation: "adrenal cortex makes many other steroid-based hormones, as well as testosterone"]

    However I did some online research and found one site that said:
    "adrenal contributes most of the precursors for testosterone". That would be in line with what you said.

    Wikipedia (Testosterone) says:
    "Like other steroid hormones, testosterone is derived from cholesterol. The largest amounts of testosterone are produced by the testes in men. It is also synthesized in far smaller quantities in women by the thecal cells of the ovaries, by the placenta, as well as by the zona reticularis of the adrenal cortex in both sexes."

    So what does adrenal cortex secrete- testosterone or testosterone precursors?
    I will go with precursors (more specific) to be safe on the MCAT.
     
  7. Vihsadas

    Vihsadas No summer
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    It could be both! I would go with neither for the MCAT, and keep both possibilities in mind when answering questions! You may find that the question you are doing gives you a hint as to what they are looking for. :)
     
  8. futuredoctor10

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    Good idea! By keeping both in mind when answering a question you can keep an eye out if either response is what they are looking for.
     

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