Biology MCQ thread..!!

[aquariangurl]

why is it true??
An enzyme's activity is supposed to increase when the substrate concentration is increased

IF the enzyme is increased along with the substrate THEN activity might increase, it's true cauze see, more substrate molecules, less no. active sites, rate of reaction decreases.

but the statement doesn't mention that there are a limited number of enzymes. So lets think that there is a constant amount of enzymes. starting from zero substrate concentration, if we increase the substrate concentration, the rate of reaction is going to increase. cuz more substrate molecules can form an enzyme-substrate complex with the enzymes. (instead of some enzymes having to wait for a substrate molecule to collide with its active site)

Also, if we change the pH of the solution, the enzyme will be denatured too. So, it WILL be inactivated!

They didn't mention EXTREME cases of pH changes, did they? a slight Ph change does not denature the enzyme!

 

[imissknow2]

why is it true??
An enzyme's activity is supposed to increase when the substrate concentration is increased

IF the enzyme is increased along with the substrate THEN activity might increase, it's true cauze see, more substrate molecules, less no. active sites, rate of reaction decreases.

but the statement doesn't mention that there are a limited number of enzymes. So lets think that there is a constant amount of enzymes. starting from zero substrate concentration, if we increase the substrate concentration, the rate of reaction is going to increase. cuz more substrate molecules can form an enzyme-substrate complex with the enzymes. (instead of some enzymes having to wait for a substrate molecule to collide with its active site)

Also, if we change the pH of the solution, the enzyme will be denatured too. So, it WILL be inactivated!

Answer is D
Question asked for the FALSE statement.

A is correct (optimal temperature)
B is correct (denturation of protein)
C is correct (increase in pH disrupt bonds such as H-bond, ionic bond in enzyme)
D is false (increase in substrate concentration means that more substrate is presence, more active sites are occupied thus enzyme activity WILL increase)

Please note that enzyme activity does not refer to the Rate of enzyme reaction.

 

[histephenson007]

@aquariangurl
The statement was :

C A change in pH can cause an enzyme to be inactivated.

As you yourself have agreed, an extreme change CAN cause an enzyme to be inactivated.

 

[aquariangurl]

True.
But I still wanna know what the MS says!

 

[hassam]

@imissknow2....ur ansers are correct....and aquarian gurl substrate conc...increase cn NEVER DECREASE rate...it generally increases bt when enzyme conc. becomes a limitng factor it becomnes constant !!!

 

[hassam]

ENZYME actiivity is DIRECTLY related to rate of reaction !!!

 

[hassam]

9 Which statement about triglycerides is correct?
A They are made up of three fatty acids combined with glycogen.
B They are more saturated with hydrogen compared with phospholipids.
C They form a bilayer in the membranes of cells.
D They have a lower ratio of oxygen to carbon compared with carbohydrates.
i know the D is anser bt wats wrong with option B

 

[hassam]

damn...its sooo cnfusing....y its D

 

[hassam]

28 When one molecule of oxygen combines with haemoglobin it makes it easier for the next oxygen
molecule to bind, which makes it easier for the next molecule of oxygen to bind.
Which orders of protein structure change to allow this to happen?
A primary and quaternary
B primary and secondary
C secondary and tertiary
D tertiary and quaternary
how the HELL quarternary structure changed....are examiners DUMB or ME

 

[hassam]

yar jaldi reply kya karo.................

 

[hassam]

y its D...see decomposition converted amino acids to ammonium...nitrifying CONVERTED not ADDED ammnium to nitrite...dont these dumb examiners know that

 

[melon159]

hassam can you xplain how crop rotation does help to increase the fertility of soil...i don't get it..

 

[Xthegreat]

hassam can you xplain how crop rotation does help to increase the fertility of soil...i don't get it..

so crop rotation.
- fertility of the soil depends on the amount of nutrients present. nutrients ie. nitrogeneous compunds
- when you plant normal plants ( non-leguminous plants ), they use up the nitrite ions in the soil
- however, if you do crop rotation, it means you plant 1 year normal plants and the next year leguminous plants
- leguminous plants are plants that have root nodules which contains rhizobium
- rhizobium is a nitrogen-fixing bacteria which converts nitrogen in air to nitrogenous compounds in the soil
- so when you do this kind of rotation, the fertility of the soil would not decrease year by year.

 

[hassam]

wat the heel is wrong...y is nt anyonne answering to ma questions........bio nerds where r u.......???????

 

[hassam]

heyyyy r u ppl sleeping

 

[histephenson007]

9 Which statement about triglycerides is correct?
A They are made up of three fatty acids combined with glycogen.
B They are more saturated with hydrogen compared with phospholipids.
C They form a bilayer in the membranes of cells.
D They have a lower ratio of oxygen to carbon compared with carbohydrates.
i know the D is anser bt wats wrong with option B

I think the problem with B is that they haven't mentioned how long the fatty acid chains are. So, if a trigyceride has 3 short fatty acid chains and the phospholipid has 2 very long fatty acid chains, the phospholipid molecule is very capable of having more amount of hydrogen atoms that the triglyceride.

On the other hand, option D looks like a much stronger statement since in carbohydrates like starch many glucose molecules are present. And each glucose molecule has about 6 oxygen atoms. But when it comes to triglycerides, we can only be sure that there are 6 oxygen molecules in the whole triglyceride ( 2 in each ester). The amount of oxygen atoms is totally variable depending on the number of carbonyl groups in the fatty acid chains. And usually, there aren't many carbonyl groups in the fatty acid chains.

 

[hassam]

K THANKS...OTHER QUESTIONSSS

 

[histephenson007]

damn...its sooo cnfusing....y its D

I hate transpiration!!
but, I'd go with C

 

[histephenson007]

28 When one molecule of oxygen combines with haemoglobin it makes it easier for the next oxygen
molecule to bind, which makes it easier for the next molecule of oxygen to bind.
Which orders of protein structure change to allow this to happen?
A primary and quaternary
B primary and secondary
C secondary and tertiary
D tertiary and quaternary
how the HELL quarternary structure changed....are examiners DUMB or ME

Answer is D.
Firstly, options A and B are surely cancelled because primary structure cannot be changed by any external influences like binding of an oxygen molecule.


In one haemoglobin molecule, there are 4 polypeptide chains. Each with one haem group which can bind with an oxygen molecule. And the question mentions that after the binding of first O2 molecule, the next one gets easier...blahblahblah... therefore, this shows evidence that the quarternary strucutre can be changed (binding of one playpeptide affects another one ......)

So, I'd prolly go with D...

 

[histephenson007]

y its D...see decomposition converted amino acids to ammonium...nitrifying CONVERTED not ADDED ammnium to nitrite...dont these dumb examiners know that

The question states that after the 4th year, the plants are plowed into the soil. Which means that, all the minerals in the plants are added back into the soil through decomposition.
Since it is a leguminous plant, it has rhizobium in its root nodules. So, there must be nitrogen fixation...

But I'm not sure about the nitrification....if this question was asked in a real exam, I would've probably gone with B....but could anyone explain why its D????