Concept discussion

[alondouek]

Water is more dense than H2O. That is obviously why it floats. Daft moment sorry.

Moral of the story; always review what you write; read the above again

[Yacoubb]

It's because I'm using my phone + it doesn't show every line until I preview it, and by doing that, my stupid phone freezes lol

[Bad Student]

So... can someone explain why lipids are less dense than water? I can't find anything on da interwebz that explains it in language I can understand.

[Stick]

Using only Chemistry 1/2 knowledge, water is held together quite compactly in liquid form since there are hydrogen bonds between molecules, whereas in lipids (eg oils) the molecules are only somewhat held together by weaker dispersion forces. I'm not sure if this is correct but the explanation seems logical.

[alondouek]

To be honest, I would be more concerned about the hydrophobic nature of lipids than their density. Density is something that, IIRC, doesn't factor much into the Biol 3/4 course - it's more chemistry.

Focus more on the fact that lipids are hydrophobic - you'll need to analyse this further when you start learning about the phospholipid bilayer, micelles, etc.

[Bad Student]

Hmmm... makes sense.

[Yacoubb]

To be honest, I would be more concerned about the hydrophobic nature of lipids than their density. Density is something that, IIRC, doesn't factor much into the Biol 3/4 course - it's more chemistry.

Focus more on the fact that lipids are hydrophobic - you'll need to analyse this further when you start learning about the phospholipid bilayer, micelles, etc.

I think that this is an appropriate assumption merely because the course (i.e. as outlined in the textbook), does not go further to mention anything regarding particular bonds between lipids, except in saturated and unsaturated fats where it discusses the compactness of the fatty acid molecules in determining whether a lipid is saturated (solid) or unsaturation (liquid consistency, e.g. oil).

[Yacoubb]

Ooh, okay lets discuss proteins. I'll do my little summary and feel free to give me constructive criticism.

Proteins are organic molecules composed of elements Carbon, Hydrogen, Oxygen, Nitrogen and sometimes Sulfur. Proteins are composed of amino acid subunits.

    R group
         |
H₂N=C=COOH
         |
         H

The above diagram is of an amino acid. There are 20 known amino acids synthesised by living organisms. The essential difference between amino acids is the composition of the R-group, which varies from amino acid to amino acid. During the condensation reaction, amino acids join by strong, peptide bonds in the free ribosomes / rough endoplasmic reticulum, as two hydrogen atom react with an oxygen atom, forming a H₂O molecule that is released for every dipeptide formed. Examples of proteins include enzymes, haemoglobin, keratin.

[alondouek]

There are four stages of structure that many proteins go through before they achieve their final product.

The primary structure is the linear sequence of amino acid subunits. These amino acids are joined by covalent bonding.

The secondary structure is the initial 'folding' of the polypeptide sequence. Most commonly, the secondary structures of a protein are categorised as 'alpha-helix', 'beta-pleating' or 'random coiling'. Other, rarer secondary structure can occur, such as the 'pi helix' or the '3₁₀ helix' (though this is beyond the realms of VCE biology). Generally, hydrogen bonding is involved in the formation of the protein secondary structure

The tertiary structure arises from further folding of the a series of alpha-helices, beta-pleats and random coils. The tertiary structure refers to the protein's 3D structure, which is held in position by varying degrees of hydrophobic and hydrophilic interactions. Tertiary structures can arise from disulfide bonds between two cysteine amino acids in a polypeptide chain; this causes the sequence to fold in on itself. These disulfide bonds aid in maintaining the protein's shape during transport via endo/exocytosis.

The quaternary structure of a protein is essentially the 'bonded aggregation' of multiple tertiary-structured proteins. Haemoglobin is an example of a quaternary protein, as is DNA polymerase.

That's pretty much all I remember

[Yacoubb]

There are four stages of structure that many proteins go through before they achieve their final product.

I don't know if this is due to your expression being wrong, but not all proteins MUST have this molecular organisation (i.e. having a primary/secondary/tertiary/quaternary). Not all proteins have a quaternary structure when investigating molecular organisation. Other than that, all of the above is spot on.

Just adding to Tertiary structure; this makes the protein critical for its function. The tertiary structure of the protein is actually responsible for the formation of a very specific active site in enzymes complementary to a specific substrate, which together form the lock-and-key model in enzymes.

[Yacoubb]

Also thought of addressing Proteomics: the study of the complete array of proteins synthesised by an organism. Proteomics now focusses not only on investigating proteins as single macromolecules, simply because no one protein acts in isolation to another protein. They all interact.

Also, I've heard of marks being deducted for stating Beta-Sheet rather than the official 'beta-pleats or pleated sheet', just to exemplify how meticulous VCAA really is!

[alondouek]

There are four stages of structure that many proteins go through before they achieve their final product.

I don't know if this is due to your expression being wrong, but not all proteins MUST have this molecular organisation (i.e. having a primary/secondary/tertiary/quaternary). Not all proteins have a quaternary structure when investigating molecular organisation.

haha yeah, I was trying to imply that not all proteins have a quaternary structure, hence "many proteins".

[Yacoubb]

I don't know if this is due to your expression being wrong, but not all proteins MUST have this molecular organisation (i.e. having a primary/secondary/tertiary/quaternary). Not all proteins have a quaternary structure when investigating molecular organisation.


haha yeah, I was trying to imply that not all proteins have a quaternary structure, hence "many proteins".

Oh fair enough I cannot wait for this year because I am in love with Bio as you can tell ^ Hoping for a 45+. Shall work thy ass off lol!

[alondouek]

Oh fair enough I cannot wait for this year because I am in love with Bio as you can tell ^ Hoping for a 45+. Shall work thy ass off lol!

You should be in love with it, that's the key to doing well! In my honest opinion, the greatest subject offered by VCAA... shame you don't get to do a U3 mid-year, those are actually a lot of fun.

[Yacoubb]

You should be in love with it, that's the key to doing well! In my honest opinion, the greatest subject offered by VCAA... shame you don't get to do a U3 mid-year, those are actually a lot of fun.

Yeah I do wish we had mid-years but its kinda better for yr 11 students like me who don't miss out on much when during mid years you'd neglect yr 11 for a momentary period! Hehe