Enzymes question

[psychologie]

Hi, was wondering if anyone would be able to help me out on the following questions regarding enzymes, i have my SAC coming up soon

1. “enzymes are ‘reversible’ and can work in either direction: substrate—> product or product—> substrate” BUT product is never turned into substrate though? even in a catabolic reaction large substrate turned into smaller products

2. is it ok to say ‘active site is a region of the protein molecules which provides a site of attachment for SUBSTRATES’ (rather than REACTANTS)

3. does the concept of ‘enzyme specificity’ apply to the induced fit model? if so, how do you explain this as the shape of the active site isn’t exactly complementary to the shape of the substrate

4. how are all chemical reactions energy dependent/require input of energy? catabolic reactions release energy…

5. are enzymes considered denatured at very low temperatures?

6. is there a difference between rate of enzyme activity/rate of reaction? ex. in the sentence: as enzyme concentration increases, rate of enzyme activity also increases

7. non-competitive inhibitors. Do they prevent binding or just reduce ability to bind?

8. both competitive and non-competitive inhibitors are reversible right?

9. cofactors include coenzymes? or are they separate? what is the extent to which we should know about these

[peterpiper]

Just a disclaimer: this is just personally from what I remember when doing biology, so the answers may be a bit rusty/incorrect.

1. I'm not quite sure what you mean. All we need to know is that an enzyme lowers the activation energy level required by a particular reaction, and it provides an active site for particular substrate/s to bind to.

Hence in the presence of an enzyme, the rate of reaction will usually see an increase.

2. You can simplify that and say: the active site refers to the location at which the substrates bind to on an enzyme molecule.

3. The induced-fit model states that the active site of an enzyme will change its structure to complement the shape of its substrates. I'm not entirely confident enough to answer the enzyme-specificity part of the question (sorry!)

4. In order to start any reaction we need to reach the activation energy level barrier which will allow the reaction to proceed. Catabolic reactions therefore will also need a certain amount of energy in order to start the reaction, even though its products will have less energy content than its reactants.

5. No, enzymes only denature at higher temperatures. At colder temperatures, things or more accurately substrates and enzymes collide less frequently due to a decrease in kinetic energy. Hence rate of reaction decreases, as the proportion of fruitful collisions is diminished. At colder temperatures, the active site of enzyme is not permanently altered like in protein denaturation at high temperatures.

6. Essentially they're the same so far as I'm concerned. You won't a get a question asking you to distinguish between them. They'll only appear on the y-axis of graphs I think.

7. Non-competitive inhibitors bind to what is known as the allosteric site. When this happens, the complex formed will completely alter the structure of the enzyme molecule. Hence active site is changed and substrate-enzyme complexes can no longer form.

8. So far as I'm concerned, I think they are usually reversible.

9. Technically yes. Just know that for some enzymes to be activated, the presence of a cofactor/coenzyme may be needed.

Hope that helped (I'm surprised how much I've retained from bio last year lol). But by no means are these assuredly correct. I'd consult someone like your teacher for confirmation.

[psychologie]

thank you so much!! what a huge help 

[Bri MT]

3. Yes, still complementary just not "perfect" fit. Think about this, if you had an enzyme with an active site where looked designed for an isosceles triangle and it was compatible with a scalene triangle shaped substrate, that makes sense and doesn't mean it would be compatible with a circle shaped substrate.  (The active site is a 3D structure but example given was 2D for simplicity)
4. The reason enzymes increase reaction rate is because they lower the amount of activation energy required. Looking at graphs can help you understand this concept if you still don't get it. As an example of needing activation energy, fires can release a lot of energy, and the activation energy is supplied by the match.
6 enzymes increase the rate of reaction. You can still have reactions take place without using an enzyme it would just be slower, they are not the same thing.    (Enzymes are still very much necessary as the difference in speed can be the difference between life and death. )
8 not necessarily. Do not write that statement in a test as it will be marked wrong.
9 I think there may be a greater emphasis on cofactors and coenzymes in the new study design (can't really remember) so I'd suggest consulting that and your teacher for the extent of knowledge you need. I would recommend you learn their functions and basic structure (organic vs inorganic)

-Completed biology as a head start subject last year