VCE Biology Question Thread

[Bri MT]

Hi guys,
With regards to photosynthesis and cellular respiration, the study design states that "details of the biochemical pathway mechanisms are not required" so how much do we actually need to know about the two processes? Like do we need to understand the steps in the Krebs cycle or the steps in the Calvin cycle? Or do we just need to remember the inputs and outputs?

It's helpful to have a rough understanding of what's going on & why you have those inputs & outputs for each stage, but definitely don't memorise the steps in each.

[miyukiaura]

Hi guys.

When a hydrophobic steroid hormone enters the cell and binds to its specific intracellular receptor, then moves into the nucleus, can it be said that this receptor-hormone complex acts as a transcription factor?

Thanks

[darkz]

Hi guys.

When a hydrophobic steroid hormone enters the cell and binds to its specific intracellular receptor, then moves into the nucleus, can it be said that this receptor-hormone complex acts as a transcription factor?

Thanks

Well transcription factors are basically anything which regulates the transcription of DNA to mRNA e.g. inhibiting it, or stimulating it. Therefore, because the complex is up-regulating the transcription of a particular protein i.e. activating it, I'd consider it to be a transcription factor.

[Sine]

(Image removed from quote.)

can anyone clarify if I've labelled this correctly

thanks.

looks good!

EDIT: only just saw your edit

The principles you talk about such as the possibility of a second pigment being involved is a good reason for the difference between the change in absorption and the rate of photosynthesis. But I am not sure why you say it is absorbed well at 700nm when the peak visibly less than that.

[amanaazim]

Hey guys can someone help me with these questions please.

hey i just wanted to ask if their are behavioural adaptation to plants

Describe the defecation reflex, including the main stimulus, receptors involved and the neuronal pathways.

Describe the main metabolic events of the absorptive state: What happens to the molecules glucose, amino acids and free fatty acids that are absorbed from the digestive tract after a meal?

i searched google but their processes are like 2-3 pages so can someone simplify it please.

Describe the main metabolic events of the post absorptive state. What happens to the molecules glycogen, triglycerides and proteins that are stored as fuel in the body?

i searched on google but the answers were too long like 2 pages, so can someone simplify this question for me please

Mod Edit: Merged the 4 posts into one. Next time when asking multiple questions at the same time, please do so all in one post rather than making 4 seperate ones.

[makram]

When referring to the innate immune response, must there be mention of PAMPS? Or does VCAA accept recognising non-self antigens as the main form of activating innate immune cells?

[Erutepa]

When referring to the innate immune response, must there be mention of PAMPS? Or does VCAA accept recognising non-self antigens as the main form of activating innate immune cells?

Knowing about PAMPs (pathogen associated molecular patterns) and the PRRs (pathogen recognition receptors) on innate immune cells might be helpfull to assist in understanding the non-specific action of this arm of the immune system, however specifically discussing these mechanisms of pathogen detection is not needed at a VCE level. It is suffice to say that these innate immune cells are activated by recognition of non-self antigen.

[tigerclouds]

Hi,
Is non-competitive enzyme inhibition reversible or irreversible? Same with competitive inhibiton, which is it? There's a lot of conflicting evidence online so I'm not sure.

[SmartWorker]

Hi,
Is non-competitive enzyme inhibition reversible or irreversible? Same with competitive inhibiton, which is it? There's a lot of conflicting evidence online so I'm not sure.

So, both could be either reversible or irreversible. It comes down to whether the inhibitor binds covalently or non-covalently. By binding covalently, the enzyme undergoes a conformational change, hence the active site is altered. But when binding non-covalently the enzyme's active site is simply occupied.

Hope it helped. 

[PhoenixxFire]

In the Heinneman textbook there's a section on organelles and macromolecules (proteins, lipids, nucleic acids, carbohydrates). However none of this is explicitly stated on the study design (except for proteins and nucleic acids) - so in how much detail do need to know this? thanks 

Textbooks always have too much info, just know the general details about the ones not specifically mentioned e.g. be able to name and identify them on a diagram and that should be plenty.

Hey guys can someone help me with these questions please.

hey i just wanted to ask if their are behavioural adaptation to plants

Describe the defecation reflex, including the main stimulus, receptors involved and the neuronal pathways.

Describe the main metabolic events of the absorptive state: What happens to the molecules glucose, amino acids and free fatty acids that are absorbed from the digestive tract after a meal?

i searched google but their processes are like 2-3 pages so can someone simplify it please.

Describe the main metabolic events of the post absorptive state. What happens to the molecules glycogen, triglycerides and proteins that are stored as fuel in the body?

i searched on google but the answers were too long like 2 pages, so can someone simplify this question for me please

Mod Edit: Merged the 4 posts into one. Next time when asking multiple questions at the same time, please do so all in one post rather than making 4 seperate ones.

Hey,
given that these appears to be questions you've been given, please give us some indication of what exactly you're stuck on so that we can help you learn rather than simply giving you the answers. What do you think the answer might be? What's confusing you about the questions?

Hi,
Is non-competitive enzyme inhibition reversible or irreversible? Same with competitive inhibiton, which is it? There's a lot of conflicting evidence online so I'm not sure.

For the purpose of VCE Bio, non-competitive is irreversible, competitive is reversible, that just isn't strictly true in reality as SmartWorker said.

[tigerclouds]

So, both could be either reversible or irreversible. It comes down to whether the inhibitor binds covalently or non-covalently. By binding covalently, the enzyme undergoes a conformational change, hence the active site is altered. But when binding non-covalently the enzyme's active site is simply occupied.

Hope it helped. 

Oh ok thank you, but with the non-competitive inhibitors, don't they always cause a conformational change to the enzyme? Does that mean that they always bind covalently?

For the purpose of VCE Bio, non-competitive is irreversible, competitive is reversible, that just isn't strictly true in reality as SmartWorker said.

So with VCAA questions, would we have to pay attention to the question's background info (eg: whether the bonds are covalent or there is excessive substrate) to determine whether the inhibitors are reversible or not? Or do we just take that as a rule of thumb? I'm just confused as to how that dotpoint in the study design can be examined.

[SmartWorker]

Oh ok thank you, but with the non-competitive inhibitors, don't they always cause a conformational change to the enzyme? Does that mean that they always bind covalently?

It is generally the case that non-competitive inhibitors result in irreversible inhibition, however in Biology there is always an exception for every rule, may even be an exception for this rule

[PhoenixxFire]

So with VCAA questions, would we have to pay attention to the question's background info (eg: whether the bonds are covalent or there is excessive substrate) to determine whether the inhibitors are reversible or not? Or do we just take that as a rule of thumb? I'm just confused as to how that dotpoint in the study design can be examined.

VCAA won't talk about covalent bonds in bio. If they say it's non competitive just assume it's irreversible, if they say that there's a competitive inhibitor it'll probably be assumed that they come off eventually, e.g. you'd expect a competitive inhibitor to reduce the enzymes ability to change substrate to product and a non competitive inhibitor to completely stop an enzyme from being able to change substrate to product.

[J_Rho]

is the way the lac operon works an example of feedback inhibition/end product inhibition

[SmartWorker]

is the way the lac operon works an example of feedback inhibition/end product inhibition

The Lac operon is an inducible operon, meaning that its structural genes are transcribed and translated only when lactose is present. When lactose is present, lactose binds to the repressor protein, inactivating it. The key is the Lac Operon only functions in the presence of Lactose, its not end product inhibition because the products of breaking down lactose does not act as an inhibitor directly. Negative feedback inhibition occurs when lactose is not present to bind to repressor protein. So I would say its negative feedback inhibition from the absence of lactose.