ippie

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1. CO2 + H2O --> C6H12O2
The above reactions is catalyzed by
a. light
b. ADP
c. CO2
d. chlorophyll
e. none of the above

==> answer : d
I am confused bet. A & D

2. the membrane that functions in respiration in the embryo is the
a. amnion
b. allantois
c. chorion
d. umbilical cord
e. yolk sac

==> answer : b
I am confused bet. B & C

3. the breathing center, which is located in the medulla oblongata, will cause an increase in the rate of breathing when the bolld concentration of
a. O2 decreases
b. CO2 deacreases
c. O2 increases
d. CO2 increase
e. N2 decrease

==> answer : d
I am confused bet. A & D
 

messenger

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the last one is wrong....ventilation increases with a RISE in CO2.
:)
 
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ippie

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yes~ you are right. my mistake.
the last one is D.
 

vize

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the first question is kind of tricky, because it seems obvious light would catalyze the reaction. but actually, light is what causes the reaction, and chlorophyll is what is necessary for the reaction to actually occur (catalyzer)

for the second question, the allantois functions for excretion and respiration because it is the precursor to the umbilical cord in mammals. the question needs to be more specific in what they're asking. so the answer could easily be "b" or "d"

the third answer doesn't really make any sense to me. i thought the medulla oblongata detected CO2 increases by detecting a decrease in pH. but if CO2 levels decreased, that's all the more reason for breathing not to increase. are you sure the answer is not d?
 

bluesdeluxe

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vize said:
the first question is kind of tricky, because it seems obvious light would catalyze the reaction. but actually, light is what causes the reaction, and chlorophyll is what is necessary for the reaction to actually occur (catalyzer)





It seems to me that the best answer to question number one is E none of the above. I don't remember chlorophyll acting as a catalyst. Isn't ATP and NADPH from the light reactions used to reduce CO2 in the dark reactions? This all happens in the choroplast; light and chlorophyll are important but isn't it ATP that is acting and the catalyst? We are talking Calvin cycle and all my books are showing ATP fixing carbon
 

bluesdeluxe

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just reread a couple chapters on photosynthesis and E still seems like the best answer....another possible answer could be Rubisco since carbon fixation completely ceases when excess O2 is present. Infact, Rubisco seems like the best answer to this question since my professors have told me in the past that it's the most common enzyme in the world.
 

djeffreyt

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Tricky wording has definitely killed me because I go really fast on these questions cause I have a hard time with Chem.

But...

for question one,

The answer is chlorophyll because it is asking for what catalyzes the reation. Remember that a catalyst is a molecule that facilitates an increase in the rate of the reaction and is "reversibly changed." The key is that chlorophyll changes its oxidation state of Mg when it acts in the photosynthetic reaction and then changes back to its original state so that it can continue to catalyze the reaction.


For question two,

I personally think the question is unfair since in every definition both the chorion and allantois are membranous structures that facilitate respiration in some way. However, the only knit picking peice of crap I can figure might distinguish the two in this question is: "functions in respiration in the embryo." The Allantois is a membrance that is continuous with membranes that surround the actual growing embryo, while the chorion actually pinches off from these membranes at some point in development. I doubt that's how they made the distinction for this question to find an answer, but I guess since the allantois is more directly associated with the embryo than the chorion, that is the answer here.
 

bluesdeluxe

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Djefferyt, my question is with the first question cause it includes an E) None of the above answer. I need to go read the structure of chorophyll more carefully. I guess none of the above would have to mean Chorophyll is not an answer in any way but when I think of enzymes helping to make carbohydrates I think NADPH and ATP and one step before that Rubisco. Chorophyll seems way to far at the beginning of photosynthesis to be considered a real contender to the answer of this question but maybe I'm reading into it too much.
 

djeffreyt

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Blue,

I understand what you're saying...and I'm the first to agree that quite a few of the practice tests I've taken have had some misleading questions or questions that have good answers if you kinda stretch it a bit. I'm no expert on this, I just think it's chlorophyll because of the reason I gave above...I'm sure more than a few people could come up with multiple legitimate reasons why it shouldn't be a good answer...anyway, back to my studying...whatever good it will do with questions like those.