VCE Biology Question Thread

[grannysmith]

Explain why a second messenger is needed to convey a signal inside a cell from a water soluble first messenger.

A water soluble signalling molecule cannot pass through the cell membrane (which is hydrophobic).

[Rishi97]

A water soluble signalling molecule cannot pass through the cell membrane (which is hydrophobic).

oh right. Thanks I would get full marks if I wrote this?

[Burt Macklin]

What's the role of NAD+ and NADH in Glycolysis? What exactly are they and how do they come about through the breakdown of glucose into 2 pyruvate molecules?

Where does the electron it's carrying come from?

[soNasty]

whats an excitatory neurone and an inhibitory neurone?

[alchemy]

What's the role of NAD+ and NADH in Glycolysis? What exactly are they and how do they come about through the breakdown of glucose into 2 pyruvate molecules?

Where does the electron it's carrying come from?

^On this note, I was wondering if water involved in the lysis of the glucose molecule? Hence, would the splitting of water itself into Hydrogen load the NAD with Hydrogen ions to form NADH? I'm still unsure about this as some equations have water as a reactant for cellular respiration.

[gohfish]

^On this note, I was wondering if water involved in the lysis of the glucose molecule? Hence, would the splitting of water itself into Hydrogen load the NAD with Hydrogen ions to form NADH? I'm still unsure about this as some equations have water as a reactant for cellular respiration.

From what I know, water is not a reactant of glycolysis. You may be getting this confused with photosynthesis where water is both an input and an output. In glycolysis, NAD+ remove hydrogen atoms from glucose to form NADH. (This isn't entirely correct, as glycolysis is actually a more complex multi-step process, but you don't need to know about this)

As jessica666 said, all you need to know is that NAD+ is reduced to NADH, which carries electrons to the mitochondria where they are used in the electron transport chain to generate ATP.

[millie96]

Can somebody please explain how the signal transduction model and the stimulus response model  work together or differ??

[vox nihili]

Can somebody please explain how the signal transduction model and the stimulus response model  work together or differ??

Stimulus response is broader picture, whereas signal transduction is a bit more specific, talking about how the signal leads to a response.

[grannysmith]

I guess you could relate one to the other.
For example, signal transduction basically involves three parts: reception, transduction and induction. Similarly, the stimulus response model involves a receptor responding to a signal, transmission and coordination of the signal, and lastly, an appropriate response by an effector.
There are many parallels between the two, but I'll let you think about it

[Mongsam]

Is diffusion a molecule-specific process? For example, does diffusion of sucrose molecules take into account the concentration of sucrose molecules only when diffusing or does it also take into account other solutes that are present?

[vox nihili]

Is diffusion a molecule-specific process? For example, does diffusion of sucrose molecules take into account the concentration of sucrose molecules only when diffusing or does it also take into account other solutes that are present?

Both.

[KanMan]

I have a photosynthesis(Elodea/pond water experiment) SAC next week and one of the questions specified in the booklet was :
"Why was aluminium foil wrapped around the culture tubes instead of putting them in a dark place?"

My guess is that the culture tubes need to be completely restricted from light exposure. This can be achieved by wrapping the tubes with a reflective material such as aluminium foil which restrains light waves of varying wavelengths entering the test tube from the external environment, due to the reflective nature of the foil. Perhaps this is different to 'putting them in a dark place' as light energy might still be present, just with a different wavelength, hence not stopping light exposure?

I don't think this is the correct answer, I was wondering if anyone else has a different interpretation.
Thanks

[howlingwisdom]

To what level of depth to we have to know about T and B cells?

[RazzMeTazz]

What is the difference between pathogenicity and virulence.

They both seem pretty similar to me, so I am having a hard time distinguishing between the two.

Any examples would be appreciated!

[katie101]

In what ways are plant hormones different from animal hormones?