PROTEINS & ENZYMES- AQA A LEVEL BIOLOGY + EXAM QUESTIONS RUN THROUGH

[@AlevelBiologyHelp]

00:49 = Amino acid structure and polypeptides 03:59 = Protein structure (primary, secondary, tertiary & quaternary) 07:40 = Biuret's test for protein 08:43 = How enzymes work and the induced fit model 11:07 = How temperature affects enzyme activity 12:35 = How pH affects enzyme activity 13:54 = How enzyme concentration affects enzyme activity 15:11 = How substrate concentration affects enzyme activity 16:02 = Competitive inhibition of enzymes 17:20 = Non-competitive inhibition of enzymes 18:26 = Exam questions and mark schemes

[@yasminj6945]

Thank you so much for this video, and for explaining the mark scheme it was so helpful!

[@ryankirk4965]

Thank you so much! I have an enzymes test this week so this is very useful :)

[@AlevelBiologyHelp]

You're welcome, let me know how your test goes :)

[@starflowerm5058]

This video was so helpful! I've got a biology test on it tomorrow, so this really helped me. Thank you 👍🏻

[@woknow9356]

at 30:29 you said it was a comparative question but how would you know to compare because it says what is the effect so how would you know to not just explian the effects of each test and know to compare them to eachother is there any command words im missing or not understanding

[@AlevelBiologyHelp]

Hi! Tricky isn't it. So the question is asking about the effect of cyanide in group 1 trials in TABLE 2. Table 2 says "trials allowing comparisons to be made", which infers that you need to compare data (from table 1 as it says) in your answer. Hope this makes sense!

[@jhaddjeri]

for the last question could i explain the curves plateau because at higher temperatures(outside the optimal range) the hydrogen and ionic bonds in the enzymes tertiary structures are affected resulting in change in shape of active site, therefore the enzymes used in the reaction wont be able to form E-S complexes and therefore rate of reaction slows down, or does it have to be because substrate is used up.

[@sshafqat4508]

Girl, you have just nailed the job!

[@seokjinkim9604]

hello, Can I ask if you'd just need to assume that enzymes are made up of only one polypeptide chain for A-level AQA? (because it is always described as in their tertiary structure)

[@AlevelBiologyHelp]

Yes, just assume that :). You don't really need to know loads about protein structure at A Level

[@KL-fd6gn]

Hey there , thank you so much for the video it’s really helpful I was wondering about the answer in 23:29 you wrote that cyanide acts as a competitive inhibitor . Instead isn’t the antidote what acts as the competitive inhibitor or is it the substrate/ cyanide itself that acts as the competitive inhibitor?

[@AlevelBiologyHelp]

Hi! Cyanide is the competitive inhibitor of the enzyme. The antidote acts as a sort of competitive inhibitor for the Cyanide as the antidote prevents binding of Cyanide to the active site :) . Hope this makes sense

[@KL-fd6gn]

A level Biology Help so both the antidote and cyanide are competitive inhibitors?

[@AlevelBiologyHelp]

@@KL-fd6gn Yes! But only Cyanide is a competitive inhibitor towards the enzyme

[@dno.16]

for the biuret test. i know to use biuret's reagent but cgp revision guide memtioned adding sodium hydroxide to make test solution alkaline and then adding copper (II) sulfate solution. is that really necessary to know for biology as year 1 or even in general?

[@AlevelBiologyHelp]

No, that's not necessary. All you need to know is "biuret's reagent". :)

[@natasha0074]

thank you so much you r a blessing

[@AlevelBiologyHelp]

You're welcome! Glad I could help :)

[@rubiksworld2170]

How did you know it was a comparison question for q5 c ii?

[@AlevelBiologyHelp]

Because it is asking about table 2 and group 1, which has made a comparison with A and B. :)

[@Grace-yt1bi]

Great vid🥳

[@jayhoa8249]

Hey how many amino acids sequences does one polypeptide chain contain?

[@AlevelBiologyHelp]

Just one because a polypeptide chain is a chain of amino acids :)

[@courtneyxo631]

would need to know other like forms of proteins like gobular and fibrous and what they contain ?

[@marianna094]

Yes

[@courtneyxo631]

@@marianna094 okay thank you

[@AlevelBiologyHelp]

It's good to be aware of globular and fibrous proteins, but you won't be asked about it in the exam (more than likely)

[@ayeshakhan8726]

Hey, can you recommend me any channel for As physics and chemistry, like yours

[@AlevelBiologyHelp]

Hi! I don't know any Physics channels unfortunately, as I didn't study it. However, a great Chemistry channel is "Eliot Rintoul" :)

[@ayeshakhan8726]

Thanks

[@seokjinkim9604]

what is the difference between enzyme-controlled and enzyme-catalysed reactions? thanks,

[@AlevelBiologyHelp]

Enzyme-catalysed means that the enzyme increases the rate of reaction and enzyme-controlled can mean either increase or decrease. :)