Biology Unit 3 Questions Megathread

[dooodyo]

Haha ,

That's the definition in the Heinemann book lol 

[shinny]

My chemistry isn't the greatest anymore so I'm happy for anyone to make any corrections, but from what I remember...

whether all non - polar molecules have ph of 7 (or vice versa) thanks

Uh, if they're non-polar, then that means they can't dissolve in water (a polar but not charged substance). If it can't dissolve, how the heck are you going to measure the pH

a polar molecule must be charged.

Explained by Rohitpi above. Read your Chem textbook or my unit 1 notes that I've attached for further clarification though. Your foundations of Chemistry seem a bit weak and if you want to understand Biology to the depth that you seem to be wanting to, you need the principles of Chem unit 1 and some of 2 as well. It's hard for me to fully explain all of this since what I'm covering in this post involves knowledge from across pretty much all of unit 1, so it's best for you to just go back and revise.

In a nutshell though, charged stuff are ions. Molecules (i.e. stuff joined by covalent bonds) are not charged. However, they can be polar if there is non-symmetrical electron distribution around an atom or molecule, resulting in a momentary and temporary dipole arrangement of charge. Therefore, think charge=permanent, polar=temporary charge.

Acidic or Basic substances must have an excess of H or OH as charge?

So does that mean all acidic or basic substances are charged?

Go back to your definitions of acids and bases, and to that of charge. Acids are proton donors; bases are proton receivers. Charge is due to the gain and loss of electrons. They're distinct concepts. So no, this means not all acids/bases are charged. For example, something as simple as ethanoic acid (CH3COOH) isn't charged, but it's an acid as the name implies. Pull simple examples to test any queries you have. That one shouldn't have been very difficult to disprove.

EDIT: Forgot you're only year 11 so you're doing Chem unit 1/2 now In that case, it'll progressively make more sense perhaps as you do Chemistry. A lot of this stuff should've been covered in previous years to some extent though?

[HERculina]

OHHHHHH. despite it being Bazza16 q.s that explanation helped clear things out a bit

Haha ,

That's the definition in the Heinemann book lol 

HEHE, it totes was

[pi]

A lot of this stuff should've been covered in previous years to some extent though?

'Charge' is definitely in VELS yr 10. Polarity might be new though, but is fairly simple once you get the basic idea of electronegativity.

[HERculina]

Yah but the books dont explain it properly and if you went to a shitty school like me, the teacher didnt really teach us chem well...

[WhoTookMyUsername]

My chemistry isn't the greatest anymore so I'm happy for anyone to make any corrections, but from what I remember...

whether all non - polar molecules have ph of 7 (or vice versa) thanks

Uh, if they're non-polar, then that means they can't dissolve in water (a polar but not charged substance). If it can't dissolve, how the heck are you going to measure the pH

a polar molecule must be charged.

Explained by Rohitpi above. Read your Chem textbook or my unit 1 notes that I've attached for further clarification though. Your foundations of Chemistry seem a bit weak and if you want to understand Biology to the depth that you seem to be wanting to, you need the principles of Chem unit 1 and some of 2 as well. It's hard for me to fully explain all of this since what I'm covering in this post involves knowledge from across pretty much all of unit 1, so it's best for you to just go back and revise.

In a nutshell though, charged stuff are ions. Molecules (i.e. stuff joined by covalent bonds) are not charged. However, they can be polar if there is non-symmetrical electron distribution around an atom or molecule, resulting in a momentary and temporary dipole arrangement of charge. Therefore, think charge=permanent, polar=temporary charge.

Acidic or Basic substances must have an excess of H or OH as charge?

So does that mean all acidic or basic substances are charged?

Go back to your definitions of acids and bases, and to that of charge. Acids are proton donors; bases are proton receivers. Charge is due to the gain and loss of electrons. They're distinct concepts. So no, this means not all acids/bases are charged. For example, something as simple as ethanoic acid (CH3COOH) isn't charged, but it's an acid as the name implies. Pull simple examples to test any queries you have. That one shouldn't have been very difficult to disprove.

EDIT: Forgot you're only year 11 so you're doing Chem unit 1/2 now In that case, it'll progressively make more sense perhaps as you do Chemistry. A lot of this stuff should've been covered in previous years to some extent though?

Thanks a lot!
Does that mean though that non - polar don't affect ph of solution? By proton donors and revievers do you just mean H+ ?

I was confused because some of the TSFX notes i bought seemed to suggest only polar substances change ph :S

[shinny]

Non-polar stuff can't even be in the solution to begin with because it can't dissolve. Think of mixing oil and water. It just forms a separate layer on top. And yeh, H+ is essentially just a proton because the most common hydrogen isotope has no neutrons. Therefore a hydrogen atom missing an electron (H+) is just a proton.

[Drunk]

My bio teacher today said that to mix polar and non-polar substances, you'd need something that's both, like detergent or phospholipids.
I haven't really gotten my head around this concept yet - how would you apply this to the oil in water thing? Does it apply? Or am I just taking it out of context?

[Russ]

Read here

The idea is that when you mix the two, polar clumps with polar and non-polar with non-polar. A detergent has areas that can bind polar substances and non-polar substances. That way, it can bind the oil on the plate you're washing as well as the water you're using, in order to pull it off.

[roger-al]

what is an amino acid?

[WhoTookMyUsername]

Building block of polypeptides.

Consist of an amino group, a carboxyl group, a carbon 'centre', a hydrogen sticking out one side, and a variable R group the other side

[pi]

what is an amino acid?

Picture is worth a thousand words...  (although it is a monomer of polypeptides and proteins)

[WhoTookMyUsername]

Don't need to know alpha carbon though? (+ wtf is it)

[Russ]

Just a designation of the central carbon

[pi]

Just a designation of the central carbon

Yep, its just got an awesome name because every scientist wants to be famous for naming something.