Biology Unit 3 Questions Megathread

[shinny]

Is a Lipid a Macromolecule? ( i have a definition that does not include lipids as macromolecules??)

Yes, but they are not polymers. That's the more important distinction to remember.

[pi]

A macromolecule is a very large molecule commonly created by some form of polymerization. In biochemistry, the term is applied to the four conventional biopolymers (nucleic acids, proteins, carbohydrates, and lipids)

...

[Cygnus]

woludn't that be wrong becuase it just says that " biopolymers (lipids)"?

[shinny]

woludn't that be wrong becuase it just says that " biopolymers (lipeds)"?

Appears so. Who wants to go and edit Wiki for us to fix that

[pi]

woludn't that be wrong becuase it just says that " biopolymers (lipids)"?

Its really a tough one. And it depends on how you take the definition of a polymer (hence, disagreement in some textbooks and websites).

A polymer is something that has repeated subunits, and those subunits have to be covalently (...intermolecular) attached. Thats the standard definition.


Why some textbooks classify them as polymers:
Lipids are groups of carbon atoms (the 'monomers') that are attached covalently, and so it fits the overall definition of a polymer. Plus, by doing so they don't need a new big heading for lipids and can make that neat table of the 4 'polymers'.


Why it shouldn't be a polymer:
The subunits for a polymer, the monomers, should not be atoms, but molecules; although this is not specified in the definition of a polymer (or a biopolymer -a polymer produced by living organisms).


My conclusion: as probably realised, this is pretty hazy and definitions are always changing and are accepted by some and not others. If on an exam (and it wouldn't be, so calm down!), I would say they aren't because of the definition of a monomer being a molecule (although this isn't in the definition of a polymer).

[Cygnus]

Hmmm.... I would have just argued that lipids are not polymers since they do not
have repeated identical or similar units.

Though they are biomacromolecules since there are lots of lipids in our cells e.g
phospholipid bilayer and they are synthesized by biological organisms?

[Russ]

Irrespective of whether they're polymers, they're certainly biomacromolecules.

[Cygnus]

Hey guys,

What is meant by a reducing sugar?

_{Russ - merged topic}

[HERculina]

Lipids are macromolecules but definitely not polymers cause theyre not a chain of identical/similar sub-units linking together
glycerol + fatty acid chains aint monomers. well, thats wat Douchy sed

BTW, do we have to know about condensation and hydrolysis reactions? do they appear in sacs/exam?
And do we have to know what specific proteins do?

[WhoTookMyUsername]

Lipids are macromolecules but definitely not polymers cause theyre not a chain of identical/similar sub-units linking together
glycerol + fatty acid chains aint monomers. well, thats wat Douchy sed

BTW, do we have to know about condensation and hydrolysis reactions? do they appear in sacs/exam?
And do we have to know what specific proteins do?

Their not hard really,

Just condensation to form a polymer and hydrolysis to break it down


Does condensation AlWAYS require energy, and hydrolysis ALways release energy?

[Russ]

BTW, do we have to know about condensation and hydrolysis reactions? do they appear in sacs/exam?
And do we have to know what specific proteins do?

As said it's not hard, condensation produces water as it builds up a larger molecule (think peptide bond formation). Hydrolysis is the reverse, it splits a water molecule to add it across either side of a bond, thus breaking it.

It's chemistry so it won't be assessed directly but it's useful to know

I doubt you'll need to know specific proteins, this is only VCE but it can't hurt to know a couple of the major/common ones that come up through the year.

Hey guys,

What is meant by a reducing sugar?

This is chemistry not biology and has me trying to remember my 1st year classes...from memory it's a sugar with a functional group that can be oxidized (this subsequently reduces something else, hence the name). Page Mao for this, it's not really biology

[WhoTookMyUsername]

Does condensation AlWAYS require energy, and hydrolysis ALways release energy?

[Russ]

Not necessarily. The products will be at a higher/lower energy state than the reactants (depending on which process) but it may not "release" energy.

[WhoTookMyUsername]

Where does the energy go then :S

[Russ]

It's not my strength, but it's related to the entropy of the system (Gibbs Free Energy) and how "ordered" it is.

If you want, you can just think of it as always releasing/consuming energy because I don't think the distinction will ever be important