VCE Biology Question Thread

[sammiegan]

Hi, I was wondering if  the phospholipid bilayer was a polymer in itself, being made up of phospholipid molecules as its monomer?
And also is haemoglobin a polymer?

thanks!

[alondouek]

Hi, I was wondering if  the phospholipid bilayer was a polymer in itself, being made up of phospholipid molecules as its monomer?
And also is haemoglobin a polymer?

thanks!

Nope on both counts! The phospholipid bilayer is not a polymer, but is is stabilised and given rigidity by membrane molecules such as cholesterol.

Haemoglobin is a quaternary protein with inorganic prosthetic groups inside it, but it isn't a polymer

[DJA]

Hi, I was wondering if  the phospholipid bilayer was a polymer in itself, being made up of phospholipid molecules as its monomer?
And also is haemoglobin a polymer?

thanks!

1) No the phosoplipid bilayer is not a polymer. A polymer is a substance which has a molecular structure composed of a lot of similar units (monomers) bonded together. The phospholipid bilayer while being composed of many many individual phospholipids is not bonded together strongly in the way polymerisation does.
For example with condensation polymerization between a hydroxy and carboxyl group, a covalent bond is formed which is very strong. In comparison, all that holds phospholipids together is fairly weak in comparison van der waals and hydrogen bonding (you don't need to know the specifics for bio). Such weaker forces allow the membrane to be flexible, semi-permeable and definitely not fixed in any way. If it was polymerized, it would be far more fixed. Think of a protein amino chain-completely different story.

2)  Haemoglobin is not a polymer in itself. It is a globular conjugated protein containing 4 polypeptides, 2 identical beta chains and two identical alpha chains which forms around a haem group which binds to oxygen. Note that the polypeptide chains THEMSELVES are polymers as they are composed of amino acid monomers. However the haemoglobin molecule itself is simply a product of a protein's quatenary structure.

Please post if you need further clarification! Hope this helped

beaten by alondoeuk but ill post anyway

[sammiegan]

Nope on both counts! The phospholipid bilayer is not a polymer, but is is stabilised and given rigidity by membrane molecules such as cholesterol.

Haemoglobin is a quaternary protein with inorganic prosthetic groups inside it, but it isn't a polymer

Oh okay! Thankyou so much for the explanation!!:)
From, Sammie

[DJA]

Following psyxwar's very helpful explanation of Cellular Respiration, I have drawn up in color my own diagrammatic representation of Cellular Respiration.
Note that the info goes beyond VCE Biology on many counts. The reason why I personally have decided to learn further than the course is simply because I find you understand more holistically if you go a bit further and hence are more likely to remember it. If you just rote learn facts without understanding I find it personally much harder to learn.

I hope this helps visual learners understand cellular respiration.
Enjoy!

Cheers for the info and fix alondouek!

[MM1]

Can someone clarify what it is meant by the 5' to 3' of a DNA molecule?

Also, are coenzymes a 'category' of cofactors?

Cheers!

[vox nihili]

Can someone clarify what it is meant by the 5' to 3' of a DNA molecule?

Also, are coenzymes a 'category' of cofactors?

Cheers!

So a phosphate group is attached to the number 5 carbon of deoxyribose, so the end of the DNA where the phosphate is the last thing, that's 5' (the end that the phosphates are pointing to per se). A hydroxyl group (OH) is attached to the number 3 carbon of deoxyribose, so that end is called 3'.

Essentially, yep. The VCAA are just painful with this and we have no idea why they even make the distinction...

[MM1]

So a phosphate group is attached to the number 5 carbon of deoxyribose, so the end of the DNA where the phosphate is the last thing, that's 5' (the end that the phosphates are pointing to per se). A hydroxyl group (OH) is attached to the number 3 carbon of deoxyribose, so that end is called 3'.

Essentially, yep. The VCAA are just painful with this and we have no idea why they even make the distinction...

Thanks!

Yeah I've had the same problem with understanding chromatids; is the chromosome holistically considered a chromatid or is it the separate strands held together by the centromere called chromatids. A little confusing. My teacher said both is correct...

[vox nihili]

Thanks!

Yeah I've had the same problem with understanding chromatids; is the chromosome holistically considered a chromatid or is it the separate strands held together by the centromere called chromatids. A little confusing. My teacher said both is correct...

Best way to look at it is that a chromatid is one strand of DNA with histones. Therefore when the chromosomes replicate, you get two chromatids in one chromosome.

[DJA]

Is ATPase a protein complex embedded in the cristae of the mitochondrion or is it simply an enzyme that floats around?

[Shenz0r]

Yup, ATPase is a transmembrane enzyme so it's found on cristae. When the other proteins involved in the electron transport chain receive electrons, they pump protons into the intermembrane space. This creates a proton gradient, and the protons then diffuse through ATPase back into the matrix in order to generate ATP. This is why ATPase cannot be an enzyme that floats around.

This is outside of the course's scope but it should help to understand it nevertheless.

[DJA]

Yup, ATPase is a transmembrane enzyme so it's found on cristae. When the other proteins involved in the electron transport chain receive electrons, they pump protons into the intermembrane space. This creates a proton gradient, and the protons then diffuse through ATPase back into the matrix in order to generate ATP. This is why ATPase cannot be an enzyme that floats around.

Thanks for that.
And similarly what about cytochrome complexes. Are they also embedded in the cristae, or are they just enzymes?

[DJA]

Also could someone please post a concise explanation if possible of photosynthesis according to what needs to be actually known in the scope of the VCE course?

I would be greatly appreciative.

[Yacoubb]

Also could someone please post a concise explanation if possible of photosynthesis according to what needs to be actually known in the scope of the VCE course?

I would be greatly appreciative.

Photosynthesis occurs in two stages:

Light-dependent stage:
1.) This stage takes place in the thylakoid membranes of chloroplasts.
2.) Light energy is absorbed by chlorophyll molecules; electrons within chloroplasts become energised.
3.) Water is split to form H+ ions and oxygen gas.
4.) NADPH and ATP is formed.

Light-independent stage:
1.) This stage takes place in the stroma of chloroplasts.
2.) Carbon dioxide reacts with H+ ions (provided by NADPH) to produce glucose.
3.) ATP provides the energy for the synthesis of glucose.
4.) Excess H+ ions react with O2- ions to produce water (a by-product).

[RazzMeTazz]

Hi, can someone please explain the relationship between the structure and function of the extracellular matrix?

Because I understand its structure, that it consists of long flexible fibres embedded in a glycoprotein and glycolipid matrix but I am unsure of how this relates to its function?

Thankyou