Damn...this is bothering me: Pancreatic amylase vs Salivary amylase

[tak08810]

So in EK Bio, page 124, it says "...pancreatic amylase is much more powerful [than salivary amylase".

But in the answer explanation for Passage 5, Question 31, Chapter 6 in the BR Orgo book (older edition, pg 55), it states "The two forms of amylase are identical enzymes, so they are equivalent in strength."

WTF?

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[BilalL]

So in EK Bio, page 124, it says "...pancreatic amylase is much more powerful [than salivary amylase".

But in the answer explanation for Passage 5, Question 31, Chapter 6 in the BR Orgo book (older edition, pg 55), it states "The two forms of amylase are identical enzymes, so they are equivalent in strength."

WTF?

Pancreatic amylase and salivary amylases are both alpha amylases. The orgo book seems to be talking about alpha vs beta amylase (in plants).

Im not sure about why pancreatic is much more powerful.

 

[tak08810]

Pancreatic amylase and salivary amylases are both alpha amylases. The orgo book seems to be talking about alpha vs beta amylase (in plants).

Im not sure about why pancreatic is much more powerful.

Hmm, thanks for the response but I don' t think that is the answer.

The question is

"Why is amylase released in both saliva and by the pancreas into the small intestine".

And the answer choices are

1.Salivary amylase is destroyed by the gastric fluids (correct answer)
2.Pancreatic amylase is weaker than salivary amylase
3.Salivary amylase is weaker than pancreatic amylase
4.Pancreatic amylase cleaves amylose with b-linkage while salivary amylase cleaves a-linkages.

Looking back, I guess even if pancreatic amylase is indeed stronger 1 is still the best answer, but I would like to know if BR made an error or if EK made an error.

 

[BilalL]

Hmm, thanks for the response but I don' t think that is the answer.

The question is

"Why is amylase released in both saliva and by the pancreas into the small intestine".

And the answer choices are

1.Salivary amylase is destroyed by the gastric fluids (correct answer)
2.Pancreatic amylase is weaker than salivary amylase
3.Salivary amylase is weaker than pancreatic amylase
4.Pancreatic amylase cleaves amylose with b-linkage while salivary amylase cleaves a-linkages.

Looking back, I guess even if pancreatic amylase is indeed stronger 1 is still the best answer, but I would like to know if BR made an error or if EK made an error.

Oh i wasnt sure what were the "forms" of amylase mentioned in the BR book. In that case, yes it seems there is a contradiction between EK and BR.

I dont have the answer to this by the way other than maybe the specificity of the enzymes. I think pancreatic amylase has a lower specificity making it "stronger"?

EDIT:Argh im trying to figure this one out still. Wish I was near my campus so I could get journal access. I cant be bothered to setup VPN.

 

[PingPongPro]

There does appear to be a direct contradiction, but don't let it bother you too much. I've found there are a lot of small differences in the books, but it won't make much of a difference in the grand scheme of things.

This is kind of annoying I agree. I think the BR passage is just making a generalization and saying that alpha amylases are the same enzymes in pancreatic amylase and salivary amylase.

The EK book is saying that pancreatic amylase is better at hydrolyzing. I think its because the small intestine environment as well as the increased surface area of the food here, allows for the pancreatic amylase to have greater strength than the salivary amylase.

So in short, they are the same enzyme in a vacuum, but the different locations/environments accounts for the differences in strength. The salivary amylase gets destroyed by gastric fluids in the stomach, while pancreatic amylase does not.

 

[tak08810]

Thank you for your help guys. I think I just won't worry about it since it seems like a very minute/specific detail.

 

[whiteshadodw]

Thank you for your help guys. I think I just won't worry about it since it seems like a very minute/specific detail.

i think anytime you see enzymes on the MCAT, think about how pH affects activity. i remember this question in the digestion section, and though i really had no idea, i was able to infer based on the fact that the small intestine gets bicarb from the pancreas that the pH in the mouth/saliva is different than the pH in the small intestine. most enzymes are effective only over a small range of pH. furthermore, there are tons of isozymes (same enzyme/catalytic function, but slightly different leading to weird activities in different cells). for example, one version of an enzyme found in liver cells might break down G3P under certain conditions while another isozyme might do something else with G3P (catalyze a reverse reaction).

 

[TieuBachHo]

It's very vague to say which amylases are more "POWERFUL". Are you comparing them in terms of catalytic activities in their optimal pH(s) or a specific environment in which they are both in? They may work diff.ly in diff. pH(s).

 

[BerkReviewTeach]

i think anytime you see enzymes on the MCAT, think about how pH affects activity.

Exactly!

The two enzymes are identical structures, so their activity would be the same under the same conditions. But pancreatic pH and salivary pH are not necessarily the same, so the reactivity is not necessarily the same.