VCE Biology Question Thread

[millie96]

Can somebody explain to me the dipole nature of water?

[grannysmith]

Can somebody explain to me the dipole nature of water?

A water molecule is dipole as it has two regions of opposite charge; the oxygen atom, due to its higher electronegativity, attracts the electrons that it shares in a covalent bond closer to itself. In turn, the oxygen atom is slightly (relatively) negative and the hydrogen atoms are made slightly (relatively) positive.

As a result of its dipole nature, it is said to be a universal solvent as it can dissolve other polar substances. It is important to note the notion of 'like dissolves like'.

Edited

[psyxwar]

Can somebody explain to me the dipole nature of water?

Water has an asymmetrical charge distribution; that is, though it is neutral overall, the molecule is not neutral throughout and some parts of the molecule are slightly positive, and others are slightly negative (indicated by a lower case delta (δ) (eg. δ+ refers to it being slightly positive)

This is due to the differences in electronegativity (electron-attracting ability) of its constituent elements, hydrogen and oxygen. Oxygen is a lot more electronegative than hydrogen and you can think of it as "hogging" the electrons shared in the bond. Thus, these electrons in the bonds between hydrogen and oxygen spend a lot more time around oxygen than hydrogen, and thus oxygen becomes slightly negative (due to having more than its fair share of electrons) and hydrogen becomes slightly positive.

[alchemy]

umm, does the light independent (carbon-reduction) stage provide energy for the Calvin cycle to occur?
NoB says that "plants do not build sugar simply by joining CO2 molecules together", so what then is the purpose of the carbon-reduction stage?

[Yacoubb]

umm, does the light independent (carbon-reduction) stage provide energy for the Calvin cycle to occur?
NoB says that "plants do not build sugar simply by joining CO2 molecules together", so what then is the purpose of the carbon-reduction stage?

The Calvin-Benson cycle takes place because carbon must be reduced from its highly oxidised state as carbon dioxide. However, you don't need to know this. For the purpose of VCE Biology, it is sufficient to say that in the stroma of chloroplasts, CO2 molecules react with H+ ions (provided by NADPH from the light-dependent phase), to produce glucose. ATP energy, produced during the light-dependent stage, provides the energy for the anabolic synthesis of glucose.

[alondouek]

umm, does the light independent (carbon-reduction) stage provide energy for the Calvin cycle to occur?
NoB says that "plants do not build sugar simply by joining CO2 molecules together", so what then is the purpose of the carbon-reduction stage?

The light-independent stage serves to produce glucose from CO2 and other compounds. NoB makes the point that it's a complex series of reactions, rather than just CO2+CO2+etc. I've attached a picture of the LIRs below, but you won't need to know any of the enzymes etc. until uni

[alchemy]

The light-independent stage serves to produce glucose from CO2 and other compounds. NoB makes the point that it's a complex series of reactions, rather than just CO2+CO2+etc. I've attached a picture of the LIRs below, but you won't need to know any of the enzymes etc. until uni

Thanks, but what provides energy for the Calvin cycle to occur?

[alondouek]

Thanks, but what provides energy for the Calvin cycle to occur?

Yacoubb answered this, NADPH and ATP

[alchemy]

Yacoubb answered this, NADPH and ATP

Oh right, I didn't see his post. My bad! Sorry Yacoubb.

[Frozone]

In the study guide I'm having trouble understanding what they mean by the packaging,transport, import of bio macromolecules. I'd like this clarified as I hope I'm not studying the wrong thing. 

[alondouek]

In the study guide I'm having trouble understanding what they mean by the packaging,transport, import of bio macromolecules. I'd like this clarified as I hope I'm not studying the wrong thing. 

Is there a specific concept you don't understand that I can help you with?

[Frozone]

Is there a specific concept you don't understand that I can help you with?

It's not the concepts that I'm struggling with(not yet at least), but the study design is vague and I'm not sure what I am supposed to be know for that specific part.

[alondouek]

There's nothing wrong with learning everything in your textbook/study guide about these concepts. That way, you can refine your knowledge later on when you have a better idea of the overall context of intra/extra-cellular transport!

[sprakash97]

Can someone please explain 3' and 5' in  DNA

[alchemy]

Can someone please explain 3' and 5' in  DNA

It's been done before. Check page 2 of this thread.