VCE Biology Question Thread

[vox nihili]

Why is catalase present in potatos?

Catalase is an enzyme that breaks down hydrogen peroxide. Its use is detoxify any hydrogen peroxide present (as it is toxic).

Also worth adding that hydrogen peroxide is produced in any cell that makes energy...so we need to get rid of it!

[hollyrogers]

Hey Guys,
We just did our first Sac today on cellular processes in relation to osmosis in an chicken egg plasma membrane.
- the egg shells were removed by the teachers with vinegar.
- we had 4 eggs and 4 different substances;
1. distilled water (egg increased in weight)
2. 1M salt
3. 5M salt
4. 5M Starch
- we placed each egg in the beaker with solution and recorded their weight ever 10 minutes for 60minutes.
- we found that some eggs became large obvious due to being put in a hypotonic solution.
- we found that some eggs became smaller obvious due to being put in a hypertonic solution.
What is the effect of the varying solution upon the egg specifically? i.e what will the 5M of starch do to the egg?
Thanks 

PS. what does the vinegar specifically do to the plasma membrane

[vox nihili]

Hey Guys,
We just did our first Sac today on cellular processes in relation to osmosis in an chicken egg plasma membrane.
- the egg shells were removed by the teachers with vinegar.
- we had 4 eggs and 4 different substances;
1. distilled water (egg increased in weight)
2. 1M salt
3. 5M salt
4. 5M Starch
- we placed each egg in the beaker with solution and recorded their weight ever 10 minutes for 60minutes.
- we found that some eggs became large obvious due to being put in a hypotonic solution.
- we found that some eggs became smaller obvious due to being put in a hypertonic solution.
What is the effect of the varying solution upon the egg specifically? i.e what will the 5M of starch do to the egg?
Thanks 

PS. what does the vinegar specifically do to the plasma membrane

What do you think?

You really miss out on a lot of opportunity to develop your skills if you don't give your reasoning first and try to work from there.

[Rahim22]

What happens to enzymes at low temperatures? Do they denature like they do at extremely high temperatures?

[Sine]

What happens to enzymes at low temperatures? Do they denature like they do at extremely high temperatures?

Hey

Enzymes will not denature at very low temperatures but their activity will be heavily reduced due to the decrease of average kinetic energy at low temperatures. Once heated back up to optimal temperature the enzyme will continue to function as there is no permanent damage like there is to the 3-D shape(tertiary structure) when the enzyme is heated.

[Bob2468]

1. Why is enzyme regulation (inhibition) important?
2. How are the "lock and key" and "induced fit" models similar? How are they different?

[Bob2468]

1. Why is enzyme regulation (inhibition) important?
2. How are the "lock and key" and "induced fit" models similar? How are they different?

also, what is another factor, besides temperature and pH, that affects enzyme action? How does it affect it [enzyme action]?

[peanut]

also, what is another factor, besides temperature and pH, that affects enzyme action? How does it affect it [enzyme action]?

Concentration of substrates: as the number of substrates increase, more enzymes are able to catalyse the reaction, thus increasing the reaction rate. (There comes a point when adding more substrates does nothing, as all the active sites are used up)

Concentration of products: as the number of products increase, the harder it is for the substrates to bind with the active site (basically). In other words, the product acts as an inhibitor. This slows down the reaction rate.

[peanut]

1. Why is enzyme regulation (inhibition) important?
2. How are the "lock and key" and "induced fit" models similar? How are they different?

1. Sometimes the product isn't required by the cell, so producing it would be a waste of energy and the substrate (remember all reactions require an activation energy to proceed)

2. Similar: both explain how a substrate binds with an enzyme.
Different:
Lock and key states that the substrate is an EXACT fit (has an exact complementary shape) for the active site of the enzyme.
Induced fit states that the substrate has a SIMILAR complementary shape to the enzyme's active site. The active site then changes shape to accommodate the substrate's shape. This change in shape is not permanent and will be reverted once the reaction is finished.

[Bob2468]

Need a solid definition for "Denaturation" please, thx

[Bob2468]

Also, HOW do extreme temperatures and pH denature an enzyme?

[sweetcheeks]

Also, HOW do extreme temperatures and pH denature an enzyme?

Enzymes are proteins that have very specific shapes. Altering the shape in anyway can potentially (and usually) stop the enzyme from being able to function. The tertiary structure of a protein consists of bonding between the side chains of the amino acids, extreme heat allows these bonds to be broken, changing the shape. When cooled down it is improbable that the bonds will reform in the exact same way before the heating, rendering the protein useless.

pH can also break the bonds that hold the side chains together, again disrupting the structure. Simply reversing the pH again is improbable to return the protein back to its original shape.

[ezferns]

Hi everyone!

Sorry if this question has been asked before, but I'm kinda confused about the ATP yield of cellular respiration and what examiners will accept on the exam.

For previous textbooks, NoB has said the total ATP yield of the ETC is 34 but with the new textbook, they're saying the ATP yield of the ETC is realistically 26 even though the theoretical max is 34.
Would examiners accept both answers or would they each have different opinions?

Thanks!

[Quantum44]

Hi everyone!

Sorry if this question has been asked before, but I'm kinda confused about the ATP yield of cellular respiration and what examiners will accept on the exam.

For previous textbooks, NoB has said the total ATP yield of the ETC is 34 but with the new textbook, they're saying the ATP yield of the ETC is realistically  even though the theoretical max is 34.
Would examiners accept both answers or would they each have different opinions?

Thanks!

Glycolysis - 2 ATP (Net)
Krebs cycle - 2 ATP
ETC - 32-34 ATP
Total - 36-38 ATP

For the amount of ATP released from the ETC examiners will accept 32 or 34 but they will not accept a range as your answer. I personally used 32 ATP as my teacher said it was the best answer.

[Bob2468]

What is a cofactor and what is a coenzyme? How are they related? Are they organic? What are some common examples of each?

Thanks in advance