OCR Biology F212 Revision [3rd June 2013] (Now Closed)

I hate the immune system and vaccinations as in every past paper i do i get it wrong. And it comes up a lot, so frustrating.

Could someone describe the structure of collagen please


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Collagen is a fibrous protein. It's made up of 3 polypeptide chains wound around each other. Each of these polypeptides is made up of around about 1000 amino acids. The 3 chains are held together by hydrogen bonding .

Each of these collagen molecules (i.e. the three chains wrapped around each other) is connected to another collagen molecule (another molecule of 3 polypeptides). These are connected by covalent bonds or cross links. These cross links are staggered along the collagen, resulting in a collagen fibril.

Hope that helps

It does help thanks a lot


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It's not covalent bonds, it's hydrogen bonds I swear..?


Posted from TSR Mobile

Collagen is a fibrous protein. It's made up of 3 polypeptide chains wound around each other. Each of these polypeptides is made up of around about 1000 amino acids. The 3 chains are held together by hydrogen bonding .

Each of these collagen molecules (i.e. the three chains wrapped around each other) is connected to another collagen molecule (another molecule of 3 polypeptides). These are connected by covalent bonds or cross links. These cross links are staggered along the collagen, resulting in a collagen fibril.

Hope that helps

My notes saaaaay covalent, between each collagen molecule :/

It's not covalent bonds, it's hydrogen bonds I swear..?


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Hydrogen bonds is correct.

My notes saaaaay covalent, between each collagen molecule :/

can someone explain the relationship between classification and phylogeny?
I think its:
closely related species are placed into groups together. Classification used to be based on observable features but now classification takes into account the evolutionary relationships between species. We can now place species into the correct group by knowing their evolutionary relationships.
Is this right or do I need something else? It's really hard to know what they are looking for with the end couple of topics of the exam, the ocr purple book is really wordy!

Can anyone tell me the difference between chronic bronchitis and emphysema? They both mention inflammation and I am confused. Are they the same form of disease but emphysema is the more serious?

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Chronic bronchitis is the inflammation of the lungs, caused by the damage to cilia and the overproduction of mucus by goblet cells, because when mucus accumulates in the lungs bacteria can thrive and cause infections.
Emphysema normally comes after because phagocytes move to the area to fight the infection but they produce elastase enzymes that break down the elastin in alveolar walls, reducing surface area / preventing recoil. It's basically caused by the destruction of the alveolar walls whereas bronchitis is just the inflammation.


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Thank you so much

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Does anyone know why high blood pressure can increase the deposition of cholesterol :L?


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High blood pressure is caused by excessive salt in the diet, known as hypertension. High blood pressure doesn't directly cause the deposition of cholesterol but it damages the endothelium of the artery wall. This in turn results in LDL's collecting at the site of the damage, cholesterol and other fatty substances are deposited under the endothelium of the artery wall in the process of atherosclerosis. This then forms an atheroma, which eventually becomes a hardened plaque, narrowing the size of the lumen and reducing blood flow etc

I hope this helps, its a very grey area really considering everything pretty much links to atherosclerosis anyone is open to correct me if im wrong as i'm not 100% sure