VCE Biology Question Thread

[Rishi97]

I was wondering about the fate of the NADH molecules in anaerobic respiration. When the net 2 ATP is produced, and NAD becomes loaded to NADH, what happens to the NADH after that. Surely, they can't get unloaded right, because there's no more ATP produced in that process?

I'll try this:
Are you talking about glycolysis? If yes, I think that when the pyruvate breaks down to form lactic acid (humans), it needs the hydrogen ions from the NADH. So the hydrogen ions and the breaking down of pyruvate, makes lactic acid/ ethanol and CO₂. Then the NADH become NAD and the process begins all over again.
Not sure if this is right though. Can someone please check my explanation

[vox nihili]

I'll try this:
Are you talking about glycolysis? If yes, I think that when the pyruvate breaks down to form lactic acid (humans), it needs the hydrogen ions from the NADH. So the hydrogen ions and the breaking down of pyruvate, makes lactic acid/ ethanol and CO₂. Then the NADH become NAD and the process begins all over again.
Not sure if this is right though. Can someone please check my explanation

Yep, that's correct. That's what lactate formation and fermentation are there for. They don't produce any more energy, they just help unload the carriers Great question and a great explanation.

[RazzMeTazz]

Hi,

What is the path that intracellular proteins take, during their synthesis?

Where do they go after they are synthesised from the free-floating ribosomes in the cytoplasm?
Do they move to the smooth endoplasmic reticulum so that they can be transported to various parts of the cells?
Thanks!

Also do all extracellular proteins that enter the Golgi Body get a carbohydrate group attached to them, to form a glycoprotein? Or do some of them just get modified but not necessarily get a carbohydrate group attached to them?

Thanks 

[RazzMeTazz]

Are carrier proteins and channel proteins only situated on the surface of plasma membranes or are they on the membranes of other organelles within the cell as well?

[jessica666]

During autocrine signalling, does the cell secrete the hormone out of the cell, so it can then bind to the membrane receptor? Or does the hormone remain within the cell after production and bind to the intracellular receptor?

Also, do the terms autocrine, paracrine and endocrine refer to the secreting cell or the hormone itself? Bit confused as some texts have mentioned 'endocrine cells' while i have also heard that these terms are a way of grouping hormones

thanks x

[Scooby]

Are carrier proteins and channel proteins only situated on the surface of plasma membranes or are they on the membranes of other organelles within the cell as well?

Yeah, organelles are bound by plasma membranes that include various transport proteins (eg. channel proteins)

During autocrine signalling, does the cell secrete the hormone out of the cell, so it can then bind to the membrane receptor? Or does the hormone remain within the cell after production and bind to the intracellular receptor?

Also, do the terms autocrine, paracrine and endocrine refer to the secreting cell or the hormone itself? Bit confused as some texts have mentioned 'endocrine cells' while i have also heard that these terms are a way of grouping hormones

thanks x

With autocrine signalling, the cell first secretes (releases) the hormone, which then binds to receptors on that same cell.

[howlingwisdom]

Also, do the terms autocrine, paracrine and endocrine refer to the secreting cell or the hormone itself? Bit confused as some texts have mentioned 'endocrine cells' while i have also heard that these terms are a way of grouping hormones

thanks x

Our teacher has told us that we don't need to know those terms (according to the Bio FAQ that's on the VCAA website I think?) but I think these terms refer to the different ways that hormones travel to get to their target cells, according to the kind of signalling (e.g paracrine signalling- the cell secretes hormones that travel through the extracellular fluid to nearby target cells)

[Jason12]

to what extent do we need to know about blood-glucose concentration/diabetes and also osmoregulation?

[Yacoubb]

to what extent do we need to know about blood-glucose concentration/diabetes and also osmoregulation?

You don't need to know about anything to do with homeostasis. It's all about detecting & responding at the cellular level.

[alchemy]

During autocrine signalling, does the cell secrete the hormone out of the cell, so it can then bind to the membrane receptor? Or does the hormone remain within the cell after production and bind to the intracellular receptor?

Also, do the terms autocrine, paracrine and endocrine refer to the secreting cell or the hormone itself? Bit confused as some texts have mentioned 'endocrine cells' while i have also heard that these terms are a way of grouping hormones

thanks x

Autocrine signalling involves a cell secreting a hormone which then binds to on that same cell. Endocrine signalling occurs in the endocrine system where hormones are sent to cells all over the body through the bloodstream. Paracrine signalling involves sending signalling molecules to cells close by.

[RazzMeTazz]

Would it be correct to say that in the light-dependent stage of photosynthesis,

the acceptor molecule - NADP+ accepts electrons to form NADP and then accepts hydrogen ions to form NADPH?

[RazzMeTazz]

Sorry this is going to sound silly but
For the Calvin cycle we don't include the enzyme 'Rubisco' as an input right?

[alondouek]

Sorry this is going to sound silly but
For the Calvin cycle we don't include the enzyme 'Rubisco' as an input right?

Generally enzymes aren't listed as 'inputs' in a reaction, if that's what you're asking; the reaction is carried out in the presence of the enzyme, rather than it being a reagent.

[jessica666]

To what extent do we need to know about nerve impulses?

•   The impulse (action potential) is initiated by the opening and closing of Na+ and K+ channels, allowing sodium ions to enter and potassium ions to leave the cell.
•   At rest, the cell membrane of a neuron is negative on the inside and positive on the outside
•   Strong stimuli result in higher frequency of impulses
•   Weak stimuli result in lower frequency of impulses

Would this be adequate? Clearly there is much more info in textbooks but i'm not sure how much we need to know.

The study design says "roles of the nerve pathway" and "types of signalling molecules:neurotransmitters"

[alchemy]

To what extent do we need to know about nerve impulses?

•   The impulse (action potential) is initiated by the opening and closing of Na+ and K+ channels, allowing sodium ions to enter and potassium ions to leave the cell.
•   At rest, the cell membrane of a neuron is negative on the inside and positive on the outside
•   Strong stimuli result in higher frequency of impulses
•   Weak stimuli result in lower frequency of impulses

Would this be adequate? Clearly there is much more info in textbooks but i'm not sure how much we need to know.

The study design says "roles of the nerve pathway" and "types of signalling molecules:neurotransmitters"

I think that's probably all you need to know. Bear in mind that the textbook mostly waffles on with lots of fun facts (about nerves, degenerative diseases, etc) that you really don't need to know in the current study design.