VCE Biology Question Thread

[warya]

Wold anyone be able to explain signal transduction/amplification as well as transcription of genes?

Are there any really good biology videos anyone knows about (exhausted Bozeman and Khanacademy)

[EspoirTron]

Wold anyone be able to explain signal transduction/amplification as well as transcription of genes?

Are there any really good biology videos anyone knows about (exhausted Bozeman and Khanacademy)

Well lets discuss this in the context of hormones shall we, focussing on how amplification effects gene transcription.

Usually, nuclear receptors reside in the cytosol of the cell. The hormone (ligand) is carried to the target receptor while being bond to serum binding proteins (remember, those hormones that interact with nuclear receptors are lipophilic). They diffuse across the membrane and bind to the given nuclaar receptor.
Ligand binding trigger conformational changes in the receptor protein, which consequently forms a homodimer or heterodimer with other nuclear receptors.
The aggregate then binds to hormone response elements which are adjacent to the specific genes of interest. The receptor then attracts coactivators such as Histone acteyl transferases which acteylate histone residues which reduces chromatin packaging. This allows for general transcription factors to come along and interact with the homodimer/heterodimer complex and recruit RNA Polymerase II for DNA transcription.

Coactivators are going to help promote gene transcription whereas corepressors are going to not favour gene transcription at accelerated rates. I'm not sure if this at VCE-level detail, but if you want more details about specific coactivators and corepressors then I'm more then happy to help.

Although I haven't done VCE Biology myself, so I don't know what level of detail they expect, I think having a read of Alberts: Molecular Biology of the Cell and Principles of Biochemistry by Leningher is a good idea.

[Rishi97]

Wold anyone be able to explain signal transduction/amplification as well as transcription of genes?

Are there any really good biology videos anyone knows about (exhausted Bozeman and Khanacademy)

Listen to Douchy's podcasts they are great!!!

[DJA]

Wold anyone be able to explain signal transduction/amplification as well as transcription of genes?

Are there any really good biology videos anyone knows about (exhausted Bozeman and Khanacademy)

In the context of VCE Biology, this is pretty much all you need to know for Signal Transduction.
Signal Transduction: Signal transduction refers to the series of events that occur after the receipt of a specific signal which is understood by a cell to produce a response.
(Often causes signal amplification as well. For hormones, the signal is either the lipid or protein hormone. Events are different based on these 2 types.)

3 Stages of Signal transduction:
Reception – the binding of the signal molecule (e.g. a hormone) to its specific cell receptor.
Transduction – the second messenger is formed in or released into the cytosol (the second messenger amplifies the stimulus and initiates the cell’s response).
Induction – activation of the cellular process.

EXAMPLES of Signal Transduction
• Lipophobic Hormones (peptides/amino acids)
1. Hydrophilic hormones – peptides or amino acids – travel in the blood and come to cell
2. Hormone must bind to G-protein embedded and traversing the phospholipid bilayer
3. This signals secondary messenger molecules to be released in cell as a result which causes signal amplification
4. These secondary molecules bind to cytoplasmic receptors initiating responses. The multiple secondary molecules allows different outcomes to come out of one signal

• Lipophilic Hormones (steroids) enter cell
1. Carrier molecule (protein which is hydrophilic) attached to the lipophilic steroid hormone carries the hormone through the aqueous blood to target cell.
2. Steroid hormone breaks off from carrier molecule, and diffuses directly through phospholipid bilayer into cell
3. The Steroid binds to another protein carrier molecule to travel through aqueous internal cellular environment
4. The Steroid travels to nucleus to stimulate or supress gene expression

[heids]

Hi Guys does anyone know what the second process of fermentation and explain the process of it?

I don't know quite what you're referring to, but for anaerobic respiration you don't have to know much.  Someone else can explain the process in depth, I just learnt the basics:

Glycolysis occurs in cytosol; without the presence of oxygen, the pyruvate then converts to lactic acid (in animals) or ethanol/carbon dioxide (in plants/yeasts, by fermentation).

[kimmytaaa]

I don't know quite what you're referring to, but for anaerobic respiration you don't have to know much.  Someone else can explain the process in depth, I just learnt the basics:

Glycolysis occurs in cytosol; without the presence of oxygen, the pyruvate then converts to lactic acid (in animals) or ethanol/carbon dioxide (in plants/yeasts, by fermentation).

thanks, because on the sac it asked something about the primary input of fermentation and then asked about the second process of fermentation.I wrote glycolysis but I am pre sure its might be wrong?

[heids]

thanks, because on the sac it asked something about the primary input of fermentation and then asked about the second process of fermentation.I wrote glycolysis but I am pre sure its might be wrong?

No, fermentation occurs after glycolysis.  In respiration every glucose molecule goes through glycolysis first, and then if there isn't oxygen the resulting pyruvate ferments rather than going through the Krebs cycle/electron transport chain.  Fermentation is driven by 'charged' NADH molecules gained from glycolysis, which lose their hydrogen and return to NAD+ molecules during this process.

2 types of fermentation:
a. 2 pyruvate ==> 2 lactate (in animal muscle cells and some bacteria/fungi)
b. 2 pyruvate ==> 2 ethanol + 2 CO2 (in some bacteria and yeasts)

The 'second process' could either be asking for a description of fermentation (i.e. fermentation is the second process of anaerobic respiration - second after glycolysis), or it could be asking for the 2nd way that fermentation occurs (i.e. 2 pyruvate ==> 2 ethanol + 2 CO2).  I think you probably should have described what happens in fermentation.

[TheAspiringDoc]

Listen to Douchy's podcasts they are great!!!

I can testify to this, Douchy's are the best! Only thing is, are they getting a bit outdated or is the content still relevant?
also, just for general interest in science, I'd recommend listening to Dr Karl's Triple J podcasts

[grannysmith]

I can testify to this, Douchy's are the best! Only thing is, are they getting a bit outdated or is the content still relevant?
also, just for general interest in science, I'd recommend listening to Dr Karl's Triple J podcasts

They were released in 2013 for the current study design; so yes, they are still very much relevant.

I recommend Bozeman's videos as well

[tiff_tiff]

hello!

are b cells a type of white blood cell? if so, why are they matured in the bone marrow when white blood cells as matured in the thymus, only red blood cells are matured in the bone marrow?

any help will be greatly appreciated! thx

[TheAspiringDoc]

hello!

are b cells a type of white blood cell? if so, why are they matured in the bone marrow when white blood cells as matured in the thymus, only red blood cells are matured in the bone marrow?

any help will be greatly appreciated! thx

B cells a form of lymphocyte (white blood cell).
All lymphocytes start off in the bone marrow, the only difference is that while T-Cells leave for the thymus, B-Cells remain.
As for what they do, here's a nice little explanation I found on the net:
B lymphocytes and T lymphocytes have separate functions: B lymphocytes are like the body's military intelligence system, seeking out their targets and sending defenses to lock onto them. T cells are like the soldiers, destroying the invaders that the intelligence system has identified.

[tiff_tiff]

thx theaspiringdoc!

Also, what is prostaglandins?
i know they are secrete by mast cells....
histamines are also secreted by mast cells for inflammation but what about the prostaglandins?

[Reus]

thx theaspiringdoc!

Also, what is prostaglandins?
i know they are secrete by mast cells....
histamines are also secreted by mast cells for inflammation but what about the prostaglandins?

They're cyclic fatty acids - lipids - that partake in inflammatory responses through hormonal mechanisms.

You don't really know this. I would however advise you to learn the process of inflammation through histamines (antigens binding to mast cells) with a diagram too.

[adnauseam]

Does anyone know if the different types of antibodies are being tested? ie IgE, IgA IgM ...

[warya]

We've had the practical for that SAC and we exposed different types of bacteria to antifungals and antibiotics, I don't really understand what we did but basically the teacher just said we have to determine if they grew or not i.e. that is their response to external stimuli  and thats all the results we are getting from it lol