Chapter 4: Enzymes and Cellular Respiration

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Be the first to discuss this chapter!

[maddiewall2699]

What level of detail are glycolysis, the citric acid cycle and the ETC required to be known in?
There is a lot of detail in the book but they are not mentioned much in the Memorise section at the chapters begining.

[goldstanda3269]

Please be guided by the first page of each chapter. It has been prepared to keep you on track for the GAMSAT.

I know you might ask: why give so much detail if it is not on the real exam. It's because the real exam does not assume that you know or have memorized any of those details BUT they may present passages containing that information. You will have everything you need in the bioenergetics passage for you to answer correctly. However, our experience is that it is helpful for you to read through the material once to get a sense as to how mechanisms work, how different parts interact, etc.

It is very important for you to do some practice ACER materials and some of the questions on our site (chapter review questions which are free with the book or the full length tests) so you can see for yourself and have more confidence with our chapter guides.

[goldstanda3269]

1. No, anaerobic conditions produces 2 pyruvate -> 2 lactate, no acetyl CoA.

BIO 4.4, 4.5

Aerobic: 2 pyruvate -> 2 acetyl CoA -> Krebs cycle

[goldstanda3269]

There is no need to re-read Biology Chapter 4, it is a waste of time. You are only expected to have a general outline of the process as indicated on the first page of the chapter. Watch the video Bioenergetics one more time (taking brief notes on the highlights only) then move on to GS and ACER practice questions.

[goldstanda3269]

"1. Can I get 'general key signs' which is often used in biology?"
- That would be like asking for a 'general key sign' for a dot. A dot is usually a period but it can be used for dozens and dozens of other reasons. You are not expected to memorise each reason.
- Arrows are used in the same general context in General, Organic Chemistry and Biology. When the examiner wants to specify a use then they must include a Key or an explanation. Other, unusual arrows could be introduced by the examiner, but again, they must define its use.


"2. In left side Figure 4.8, can I understand like following
SH2 and NAD+ will 'react' and substrate 'activate' this react.
The result is S and H+ and NADH."
- Your interpretation is reasonable, and it would often be the case as you described. If it was otherwise in an exam, the passage would need to specify the following: 1) S stands for Substrate; 2) Fp = Flavoprotein; 3) Fe is a component of cytochromes.

[BearHay]

Your Answer: C
Correct Answer: B

Explanation:
Working through the pathway, we see that VTC1m alone would not produce GMPP. However, the lysate does show the presence of other enzymes downstream, so both supplement additions must be products created after that step, which rules at B. Because VTC1m samples do show the presence of GME, we can conclude that GDP-D-mannose must have been added, which can be converted to GDP-L-galactose by GME. Between answers C and D, we see that C is correct because neither VTC2m nor VTC4m would produce significant quantities of GDH otherwise.

In the explanatory passage you stated that C was correct which contradicts what your 'Correct Answer' states (B).

[goldstanda3269]

I believe you are referring to Question 17.

You are correct and the Explanation is correct: The answer is indeed C. The programmers will update this shortly, thanks.

[JesseG]

For Question 9 on the review for this chapter.

"Your answer is wrong.
Your choice: B Correct choice: A"

I have gone over it a couple times now and I can't see how A is the correct answer.
Even the explanation seems like it agrees with me.
"[5-peptide: Arg/Lys-Ser-Met-Trp-Arg/Lys] [3-peptide: Glu or Arg/Lys - Arg/Lys or Glu-Gly]
Original octapeptide: Arg-Ser-Met-Trp-Lys-Glu-Arg-Gly"

I bumped into this question in one of the Ochem reviews and I got it wrong there too.
Am I missing something?

Thanks.

[goldstanda3269]

For Question 9 on the review for this chapter.
...
Am I missing something?

You are correct, and the Explanation is correct: The answer is indeed B. We will have a programmer update the typo on Monday. Thanks for bringing this to our attention.

[AnitaK]

Please explain q 21, more specifically

why aren't we finding the delta G for the reaction?

[goldstanda3269]

Please explain q 21, more specifically

why aren't we finding the delta G for the reaction?

Delta G was indeed calculated and the worked solution shows the step-by-step calculation. Consider reviewing Hess's Law (CHM 8.3; and there is a video by the same name in the Video section for General Chemistry).

[horbowiec.7527]

This is regarding Biology Chapter 4 Worked Solution Q8 (BIO-105):

Could you please explain why exactly you made this simplification: "simplifying it further by concluding that if [S] << Km then [S] + Km is approximately equal to Km"?

Mathematically if S = 4 and Km = 5 then yes S << Km but S+Km = 5+4=9 which is not approx = 5 (Km).

Regards,
Ania

[goldstanda3269]

This is regarding Biology Chapter 4 Worked Solution Q8 (BIO-105):

Could you please explain why exactly you made this simplification: "simplifying it further by concluding that if [S] << Km then [S] + Km is approximately equal to Km"?

Mathematically if S = 4 and Km = 5 then yes S << Km but S+Km = 5+4=9 which is not approx = 5 (Km).

Mathematically, your example of S = 4 and Km = 5 is reasonable if the information provided was that S < Km. But why put 2 less-than symbols?

ACER has a graph-based unit where, for concentration, they provide no numbers and no explanation for these 3 symbols:
-
+
++

So, presented with this ambiguity, you are almost forced to deduce that the symbols mean, respectively, little or no concentration, elevated concentration, and very very high concentration.

Similarly, the double less-than sign, <<, is presumably an approximation of the idea of "much-less-than". Now you might argue: how do I know if it is so much less than Km that the effect on the denominator becomes negligible? The hint is that the slope seems to be coming from [S] of zero or so close to zero that it is impossible to discern. Thus, either using the "much-less-than" expression provided or the graph, we can feel confident that [S] is closer to zero than it is to Km.

Alternate for BioMed students: It is not necessary to use assumed knowledge, but some students might recognize Km as the 1/2 maximum substrate concentration (graph in BIO 4.3), and thus notice the big difference between Km and where the slope begins (so close to zero).

[horbowiec.7527]

Thank you, very helpful!

Regards,
Ania