Biology Unit 3 Questions Megathread

[shinny]

its because the neurotransmitter needs a receptor to trigger a response in the next nerve cell, and I'm pretty sure neurons don't have receptors for neurotransmitters inside the cells themselves

Yeah but they bind to a receptor in order to open the channels which are also on the postsynaptic membrane... and it looked like a channel to me :S

Bit of a silly question =S Neurotransmitters open ligand-gated ion channels i.e. ion channels linked to a receptor. You can clearly see that they're defined as both receptors and ion channels within that Wiki page. Unless Russ can shed more light on this, I'd say it could go either way.

[scocliffe09]

its because the neurotransmitter needs a receptor to trigger a response in the next nerve cell, and I'm pretty sure neurons don't have receptors for neurotransmitters inside the cells themselves

Yeah but they bind to a receptor in order to open the channels which are also on the postsynaptic membrane... and it looked like a channel to me :S

Bit of a silly question =S Neurotransmitters open ligand-gated ion channels i.e. ion channels linked to a receptor. You can clearly see that they're defined as both receptors and ion channels within that Wiki page. Unless Russ can shed more light on this, I'd say it could go either way.

Couldn't agree more with Shinny - I was studying this today myself. Stupid question.

[WhoTookMyUsername]

when atp donates its phosphate group to induce a conformational change, does the energy power this exchange?
also when ATP simply releases stored energy to aid enzymes, can it be called a coenzyme?
What type of molecule is a prostglandin that triggers a fever?

[amun]

 their is a question that I don't think I 'm answering properly . can u guys please help.

When a material such a pollen, snake venom,inactive agents or transplanted tissue from a donor enters a persons body and is recognised as non-self , it will usually cause an immune response. A developing foetus could also be considered  an invader or none self , especially if it is developing inside a surrgate mother.


How are foreign cells recognised as non self by a persons body?

 I said foreign cells are  recognised by  t cells receptors  located on the surface of cells.



Is that  wrong ?

[person]

Question: What is the bond for lipids and nucleic acids?

[lexitu]

when atp donates its phosphate group to induce a conformational change, does the energy power this exchange?
also when ATP simply releases stored energy to aid enzymes, can it be called a coenzyme?
What type of molecule is a prostglandin that triggers a fever?

- I'm not too sure about the actual mechanism there, but yes, ATP-splitting powers most energy-requiring processes
- Nope, coenzymes assist structurally; they're actually bound to the enzyme.
- Prostaglandins are fatty acid molecules (which I really doubt you need to know about). Not sure about them triggering fever though. They have a similar role to histamine. Pyrogens are more the fever-trigerring molecules.

[Russ]

How are foreign cells recognised as non self by a persons body?

Foreign cells are generally recognised by absence of "self" receptors or by specific pathogen antigens. You're right, T cells are an important response but the detail you'd need depends on how many marks are assigned

[epinephrine]

Hey guys,

This is  my first post so I don't really know how this works but could someone please explain
this question.

STAV 2006

Another disease of the Thyroid gland is Graves Disease. The sufferer of this condition produces antibodies that bind to the TSH receptor site mimicking the effect of TSH binding.

(i) Would this condition increase or decrease the production of thyroxin? Explain your answer.

their answer: (i)   If these antibodies bind to the TSH receptor site and mimic what would happen if TSH itself bound then the result would be an increase in production of thyroxin (1) as the negative feedback of thyroxin resulting gin less TSH would not result in lowering thyroxin production. (1)

I don't really understand the second part of their answer.

Any help would be much appreciated.

[Russ]

Antibodies mimic TSH -> thyroid hormones (eg thyroxine) produced
Hormones acts in negative feedback -> Decrease pituitary producing TSH
Decreased TSH would NORMALLY cause decreased hormone production but the auto-Ab are not affected by that feedback loop

[epinephrine]

Thank you 

[jane1234]

1. What is the actual function of rRNA aside from making up the main component of ribosomes?

2. Is the sequence on DNA (e.g. AAT CGC) the one that codes for the amino acids, or is it the complementary sequence on mRNA (e.g. UUA GCG) - when reading off those silly tables...

3. The photosynthetic rate of plants drops when they do not recieve enough water. This is due to the fact that:

A. water is a reactant in the light independent reaction
B. water provides oxygen for the light dependent stage.
C. the stomata close, lowering CO2 intake for the light independent stage.
D. hydrogen ions from water are not available for the light dependent stage.

^^ I understand why C is correct (which was the answer they had) but why is D wrong (what I put)?

[poojas73]

1. What is the actual function of rRNA aside from making up the main component of ribosomes?

2. Is the sequence on DNA (e.g. AAT CGC) the one that codes for the amino acids, or is it the complementary sequence on mRNA (e.g. UUA GCG) - when reading off those silly tables...

3. The photosynthetic rate of plants drops when they do not recieve enough water. This is due to the fact that:

A. water is a reactant in the light independent reaction
B. water provides oxygen for the light dependent stage.
C. the stomata close, lowering CO2 intake for the light independent stage.
D. hydrogen ions from water are not available for the light dependent stage.

^^ I understand why C is correct (which was the answer they had) but why is D wrong (what I put)?

hydrogen ions are not needed for the light DEpendent reaction, only the light independent. if it had said that hydrogen ions from water are not available for the light INdependent stage then it would've been correct

[poojas73]

oh and, when writing the formula for cellular respiration, do we need to include 36/38 ADP + 36/38 Pi?

[jane1234]

1. What is the actual function of rRNA aside from making up the main component of ribosomes?

2. Is the sequence on DNA (e.g. AAT CGC) the one that codes for the amino acids, or is it the complementary sequence on mRNA (e.g. UUA GCG) - when reading off those silly tables...

3. The photosynthetic rate of plants drops when they do not recieve enough water. This is due to the fact that:

A. water is a reactant in the light independent reaction
B. water provides oxygen for the light dependent stage.
C. the stomata close, lowering CO2 intake for the light independent stage.
D. hydrogen ions from water are not available for the light dependent stage.

^^ I understand why C is correct (which was the answer they had) but why is D wrong (what I put)?

hydrogen ions are not needed for the light DEpendent reaction, only the light independent. if it had said that hydrogen ions from water are not available for the light INdependent stage then it would've been correct

But they are split in the light dependent reaction? And the H+ ions join with the NADP+ in the light dependent stage... so how are they not "needed" when if you didn't have the H+ ions in the light dependent stage you wouldn't have the carrier molecules (NADPH) needed for the independent?

EDIT: In answer to your question, I'd put it in just in case.

[shinny]

2. Is the sequence on DNA (e.g. AAT CGC) the one that codes for the amino acids, or is it the complementary sequence on mRNA (e.g. UUA GCG) - when reading off those silly tables...

Could be either; simply just look whether the table has U's in it or not to know which one to read off =T