Biology Unit 3 Questions Megathread

[jane1234]

hmmm i think its an organic molecule but i wouldnt call it a biomacromolecule cause its not a big molecules like a protein.

That's what I thought... but Neap 2007 MC:

2. Which of the following biomacromolecules contains smallest number of atoms?

A. phospholipid
B. an amino acid
C. a protein
D. a starch molecule

Answer is B

[HERculina]

:S
sorry, no idea then
i would have chosen (semi guess) and gone with A

[jane1234]

:S
sorry, no idea then
i would have chosen (semi guess) and gone with A

That's what I put... Hate these company exams!

[Russ]

I wouldn't categorize an amino acid as a biomacromolecule but the answer to that question is definitely B.

[Keo]

Would an amino acid coded for a jelly fish that glows in the dark be the same code in perhaps a mice? If so, would that make the mice glow in the dark?

[Drunk]

Would an amino acid coded for a jelly fish that glows in the dark be the same code in perhaps a mice? If so, would that make the mice glow in the dark?

Pretty sure that experiment's been done, but it wasn't an amino acid/protein, it was the code for the glow-in-the-dark gene that they transferred into the mice.

[Russ]

This one?

And yes, it's basically a tag that they can attach to other proteins etc.

[Keo]

This one?

And yes, it's basically a tag that they can attach to other proteins etc.

Yeah that's it, just wanted to clarify something. Thanks!

[WhoTookMyUsername]

how to phagocytes detect pathogens if they do not have specific antibodies?

Is it due to the lack of 'self' receptors or the clear differences (e.g. cell walle tc.)

[Russ]

They have receptors to what are called Pathogen Associated Molecular Patterns (PAMPS). Things like flagellin, that are never found in the human body, trigger uptake by phagocytes. They also have a couple of other tricks, like receptors for antibodies; so once an Ab has bound a pathogen it can be bound by a macrophage for destruction

[WhoTookMyUsername]

Thanks again Russ , another immunity questinon:


Can viruses floating in interstitial fluid trigger a B cell? or does the virus HAVE to be attached to a host cell?

[Russ]

What do you mean by interstitial fluid? If a B cell is in the blood it will bind a free virion but B cells don't really go into the tissues.
Viruses also don't really attach to host cells, it's a very temporary arrangement whilst they either merge with the membrane or are endocytosed.

[WhoTookMyUsername]

sorry didn't make it clear
by interstitial fluid i just meant extracellular fluid circulating through lymphatic system at points

*also, by attach to host cell i mean protein coat left on surface which acts an antigen i believe

so B cells can attach to free viruses?

[Russ]

B cells just have an Ig molecule on their cell surface. If they're exposed to an antigen they will bind it, regardless of where it is etc.

[Kaille]

i don't entirely agree with this answer, I went with c.

Question 16
Thyroxine is a hormone which is released from the thyroid gland into the bloodstream. It is
transported through the circulatory system until reaching target cell receptors around the body.
Thyroxine is synthesised from the amino acid tyrosine and
A. can move through the plasma membrane of the cell because it is small and
hydrophobic.
B. can move through the plasma membrane of the cell because it is small and hydrophilic.
C. binds with a receptor protein on the plasma membrane.
D. binds with a target protein on the plasma membrane.

Answer is A
• A is correct – for an amine-based molecule, thyroxine is small and also hydrophobic so
can therefore move through the plasma membrane.

I thought all protein or amino acid hormones required receptors...and dont amino acids need protein channels to enter the cell anyways?