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

Reply 260

Liamnut

13

Original post by Sophie Hurt

Can somebody explain the differences between 5 kingdoms and 3 domains please :smile:

You know in classification, you place things in taxonomic groups, the groups have a smaller number of species as you go down and the similarities between the species in the groups grow. The different groups are as follows: Domain, kingdom, phylum, class, order, family, genus and species. All groups in the same kingdom, will also be members of the same domain. However, some members of different kingdoms may also be part of the same domain.

I don't really understand how you would explain the differences. Maybe state the 5 kingdoms-prokayote,protoctist, animal, plant and fungus- and state the 3 domains- archbactria, bactria and eukayote. You could say that 4 of the 5 kingdoms (not including prokayote) are part of the same domain.

It's also worth knowing why there are now 3 dormains. My understanding is that archabactria were found to be very similar to eukayortes, in terms of the way DNA replicates and DNA polymerase. You could also say that the flangea of arcabactria and prokayotes is slightly different.

Excuse my bad spelling :-p

(edited 10 years ago)

Reply 261

Liamnut

13

Original post by HarryMWilliams

Natural selection is the driving force behind evolution, think of it as the survival of the fittest argument! Only well-adapted creatures will survive, therefore, those genes will be passed on to the next generations (assuming they reproduce successfully), as a result, evolution occurs.

Adaptations are just features, which species hold allowing them to adapt to their environments - fish have gills to breathe underwater.

Thanks, any ideas on conservation and that jazz? Some stuff on that came up in the most recent paper, but it's still worth knowing some of the key points.

Reply 262

Liamnut

13

Original post by otrivine

Describe the structure of DNA (3)

Do you know the anwser to this?

I'd start by saying that it's made of two, anti-parallel, polynucleotides. Each polynucleotide has a suga phosphate backbone, with nitrogenous bases projecting outwards. The nitrogenous bases of one chain are bonded with the nitrogenous bases of the other chain; this happens by means of hydrogen bonds, A goes with T and G goes with C-there are two hydrogen bonds between A and T and three between C and G. I'd then say the two polynucleotide chains are twisted to form a double helix.

I think you'd get a mark for mentioning the fact that they're anti-parallel, one mark for mentioning double helix and one mark for stating that the two chains are connected at the bases by hydrogen bonds. The rest is just to jazz it up and show them you know what you're talking about. You could even get a mark for saying that the sugas in the nucelotides are deoxyribose sugas.

I imagine the obvious trap in this question is to start talking about the structure of nucleotides, try and avoid this.

(edited 10 years ago)

Reply 263

Liamnut

13

Original post by yasmin.mahfouz

Could someone tell me about tRNA? Not in the guide I have and don't have the textbook :frown:

Posted from TSR Mobile

Do you know how proteins are produced?

To say it briefly, a specific part of the DNA (a gene) comes apart, there are two strands, the coding strand and the template strand, free nucelotides (with ribose sugas) bind to their complementary bases on the template strand, the mRNA then pills away and because of the base pairing rules, the mRNA will be identical to the coding strand, except where there is a T on the coding strand, there will be a U on the mRNA. The mRNA then leaves the nucleus through a nuclear pore and goes to a ribosome, either in the rough ER or in the cyctoplasm, the mRNA moves through the ribosome and as it's doing this, tRNA molecules bring the correct amino acid triplets to the ribosome (depending on the base the mRNA has), as the mRNA moves through the ribosome, more amino acid triplets get brought to the ribosome by tRNA molecules until the whole protein is assembled.

ps. It's hard to give an abstract definition of tRNA so I thought I'd just outline it's role in protein synthesis to give you a better understanding.

Reply 264

Liamnut

13

Original post by HarryMWilliams

You need to know what agglutination is, you don't really need to know lysis/antitoxins/opsonisation - a question which focussed on those would probably give you some text with information in as it isn't specification derived.

Isn't agglutination just when one antibody neutralizes more than one antigen?

Reply 265

wndms

1

In Lung cancer (7 marks) question, why can't we mention adrenaline? What kind of question would ask me to mention adrenaline?

Posted from TSR Mobile

Reply 266

Liamnut

13

Original post by wndms

In Lung cancer (7 marks) question, why can't we mention adrenaline? What kind of question would ask me to mention adrenaline?

Posted from TSR Mobile

Something that asks about the effects of nicotine. How is lung cancer related to adrenaline?

For a question on lung cancer, i.e, the causes, I'd say this:

When you smoke you breath in tar, this tar settles on the inner linings of the lungs. It contains carcinogens, most notably benzopyrene. These carcinogens move into the lung tissue and then move into the nuclese's of the cells that make up this tissue. They then have a direct impact on the genetic material and if they effect the part of the genetic martial responsible for cell division, uncontrolled cell division can take place-cancer.

Reply 267

Gotzz

13

Original post by Liamnut

Something that asks about the effects of nicotine. How is lung cancer related to adrenaline?

For a question on lung cancer, i.e, the causes, I'd say this:

When you smoke you breath in tar, this tar settles on the inner linings of the lungs. It contains carcinogens, most notably benzopyrene. These carcinogens move into the lung tissue and then move into the nuclese's of the cells that make up this tissue. They then have a direct impact on the genetic material and if they effect the part of the genetic martial responsible for cell division, uncontrolled cell division can take place-cancer.

Nuclei*

Reply 268

lauren1brown

Original post by wndms

In Lung cancer (7 marks) question, why can't we mention adrenaline? What kind of question would ask me to mention adrenaline?

Posted from TSR Mobile

A question about adrenaline would probably be how nicotine is a risk factor for CHD / atherosclerosis

Nicotine is a small addictive molecule which increases the body's release of adrenaline. This causes high blood pressure (hypertension) which puts more strain on the endothelium and makes them more likely to be damaged. This could then lead to atherosclerosis which I presume you know how that works? :smile:

Posted from TSR Mobile

Reply 269

HeyMickey6

Can someone please explain how mycoprotein is produced ?

Reply 270

nevarsan

Original post by HeyMickey6

Can someone please explain how mycoprotein is produced ?

A protein made by a fungus. You don't need to know the name of it.

Reply 271

HeyMickey6

Original post by nevarsan

A protein made by a fungus. You don't need to know the name of it.

Do we need to know how it's made tho ?

Reply 272

tssf_skye

15

Hey, could someone explain to me some questions I have about the immune system.. for some reason the textbook does not make this particularly clear.

Are phagocytes part of the primary response?
And for the secondary response.. how does it all tie in? I know what separate things do, e.g. macrophage, T-killers but I don't know when they are stimulated. Could someone give me a run down of what happens step by step once the pathogen enters the body? Thanks! :smile:

Reply 273

t()m

Can someone explain the simpson index to me, using the specimen paper Q4, I cant remember how to calculate it and the mark scheme is crap as it just gives answer. I remember in class thinking it was easy so just need to refresh it, thanks :smile:

Reply 274

Priya08

Original post by tssf_skye

Hey, could someone explain to me some questions I have about the immune system.. for some reason the textbook does not make this particularly clear.

Are phagocytes part of the primary response?
And for the secondary response.. how does it all tie in? I know what separate things do, e.g. macrophage, T-killers but I don't know when they are stimulated. Could someone give me a run down of what happens step by step once the pathogen enters the body? Thanks! :smile:

Primary response is the macrophage injesting the pathogen and putting its antigens on the cell surface membrane becoming an APC and the t lymphocytes bind to these antigens and divide into t helper and t killer cells. the t helper cells release cytokines which activate the b lymphocytes to clone into plasma cells and memory cells which secrete antibodies. these antibodies bind to the APC and kill it (humoral response)
All of that is the primary response
When ur infected by the same pathogen instead of doing that whole process again, only the memory cells clone and it produces all the plasma cells and antibodies specific to the pathogen
So the secondary response does exactly the same thing as the primary response but it uses the memory cells which were made in the primary response so the secondary response is much quicker..so quick u don't get any symptoms of the illness

T killer cells kill infected cells by making holes in their membranes

Posted from TSR Mobile

(edited 10 years ago)

Reply 275

Priya08

Original post by t()m

Can someone explain the simpson index to me, using the specimen paper Q4, I cant remember how to calculate it and the mark scheme is crap as it just gives answer. I remember in class thinking it was easy so just need to refresh it, thanks :smile:

Baiscally te formula is

1 - (Sum of (n/N)^2)

so for q4 on speciman paper, u have to work out simpsons biodiversity index for barley field so what u is

1- ( (32/196)^2 + (78/192)^2 + (86/192)^2 ) =

1 - (64/2401 + 1521/9604 + 1894/9604) =

1 - 37/98 = 61/98 ~~ 0.62

Reply 276

t()m

Original post by Priya08

Baiscally te formula is

1 - (Sum of (n/N)^2)

so for q4 on speciman paper, u have to work out simpsons biodiversity index for barley field so what u is

1- ( (32/196)^2 + (78/192)^2 + (86/192)^2 ) =

1 - (64/2401 + 1521/9604 + 1894/9604) =

1 - 37/98 = 61/98 ~~ 0.62

Thanks I remember now I was making a silly mistake, cheers.