VCE Biology Question Thread

[darkz]

Hey thanks so much for the help I have a few more qs:
1) What is the difference between NK cells and cytotoxic t-cells besides the fact that NK belong to innate and cytotoxic to adaptive?
2) If there are 369 base pairs what would be the maximum no. of amino acids? Would it be 122 as the last one has to be a STOP codon which is not considered an amino acid?
3) What is the difference between self and non-self antigens? Do they both trigger an immune response (identified as foreign?).
Thanks!

Well the difference between NK cells and Cytotoxic T cells is really beyond the scope of the course, considering that NK cells are no longer in the study design. However, the main difference is that NK cells only kill the cell if it does not bind to a sufficient number of MHC Class I markers on the cell i.e. their Killer Inhibitory receptors examine the cell surface to determine such levels. If they successfully bind to a sufficient number, then the killing signal is overridden and left for cytotoxic T cells, if they are in fact infected.

Correct, 122 would be the maximum number of amino acids

Self antigens are not detected as being foreign, they are essentially antigens that mark all of our cells so that our immune system can recognise and not kill our own body cells. However, in the rare occurrence that this fails to occur, an autoimmune disease arises

In the Krebs cycle, is FAD an input and FADH2 an output?

Correct

[PhoenixxFire]

In the Krebs cycle, is FAD an input and FADH2 an output?

Worth noting that it's unlikely that you need to know about FAD given the study design specifies ATP, NADH, and NADPH

[galaxy21]

Hey thanks so much for the help I have a few more qs:
1) What is the difference between NK cells and cytotoxic t-cells besides the fact that NK belong to innate and cytotoxic to adaptive?
2) If there are 369 base pairs what would be the maximum no. of amino acids? Would it be 122 as the last one has to be a STOP codon which is not considered an amino acid?
3) What is the difference between self and non-self antigens? Do they both trigger an immune response (identified as foreign?).
Thanks!

1. Out of the course
2. There are 20 amino acids - remember, the genetic code is redundant, meaning that there are multiple codons that code for the same amino acid, so just because there are 122 codons doesn't mean that they all code for the same amino acid. If you look at a codon table, many of the amino acid types are repeated for a number of codes
3. Self antigens are the antigens that are on cells that belong to you. These are the MHC I markers (when they aren't presenting a fragment of a pathogen). Non-self antigens are those either on pathogens, or when an MHC I marker is presenting a fragement of a foreign cell if it is infected (e.g. by a virus). Our immune system has self tolerence, so any cells labelled as 'self' will not be destroyed by our immune system, but non-self antigens are. When self cells are mistakenly recognised as non-self, this is when autoimmmune diseases come about

Hope that helps - please feel free to correct me if I am wrong about anything

[EllingtonFeint]

Could somebody please write down the inputs and outputs of the light dependent and light independent stages of photosynthesis for me pleaseeee?
The NADP, NADP2, H+ ions are messing with my head 

Just a really simple these go in these come out kinda thing  🙏🏼

[darkz]

Could somebody please write down the inputs and outputs of the light dependent and light independent stages of photosynthesis for me pleaseeee?
The NADP, NADP2, H+ ions are messing with my head 

Dependent
In, Water, Light, NADP, ADP + Pi
Out, Oxygen, NADPH, ATP

Independent
In, Carbon Dioxide, NADPH, ATP
Out, Glucose, NADP, ADP + Pi, water

[PhoenixxFire]

Could somebody please write down the inputs and outputs of the light dependent and light independent stages of photosynthesis for me pleaseeee?
The NADP, NADP2, H+ ions are messing with my head 

Light dependant:
12H2O + 12NADP = 6O2 + 12NADPH2
Light independent:
24NADPH2 + 6CO2 = 24NADP + C6H12O6 + 6H2O

[Erutepa]

3) What is the difference between self and non-self antigens? Do they both trigger an immune response (identified as foreign?).
Thanks!

Really self and non-self antigens are all just molecules. The difference is that our immune system 'learns' not to attack self-proteins by mechanisms which induce apoptosis in self-reactive T and B lymphocytes (it also learns not to attack other non-pathogenic antigens like those of allergens usually). The way we develop this tolerance is very interesting, however, it is not relevant. Autoimmune disorders can occur when these self-reactive B and T lymphocytes are not properly killed and still exist, attacking self-antigens in the same way it would to foreign antigens

[hoddemi]

Are anabolic reactions always energy requiring (endergonic), and catabolic pathways always energy releasing (exergonic)?

In the Krebs Cycle is FAD an input and FADH2 an output?

anabolic reactions are energy requiring so they can create molecules, catabolic is energy releasing in order to break down products...
based on my notes and textbook FAD is shown being recycled from FAD to FADH2 but it doesnt list it as an input, probably more important to know its loaded and helps provide energy for electron transport chain to create ATP and glucose.... based on what i have learnt..
also please correct me if any of this is wrong !

[AnonymooseUser]

If a question asked 'describe the steps involved in the cell-mediated immune response', would I refer to naive Tc cells binding to antigens on infected cells or APCs or both? I have looked at various resources that either say one or the other, so am a bit confused. Is there a particular one VCAA would prefer?

Thanks!

[EllingtonFeint]

Light dependant:
12H2O + 12NADP = 6O2 + 12NADPH2
Light independent:
24NADPH2 + 6CO2 = 24NADP + C6H12O6 + 6H2O

Oh you utter legend! Thanks!

[PhoenixxFire]

If a question asked 'describe the steps involved in the cell-mediated immune response', would I refer to naive Tc cells binding to antigens on infected cells or APCs or both? I have looked at various resources that either say one or the other, so am a bit confused. Is there a particular one VCAA would prefer?

Thanks!

In reality both happen, but VCAA want you to talk about Tc cells. I would just talk about Tc cells, but also mention that cytokines released from activated T helper cells cause Tc cells to divide and differentiate.

[C14M8S]

1) How does the body differentiate between self and non-self non-cellular objects (i.e proteins) seeing as proteins lack MHC1 markers, I can't see how they would be distinguished.
2) Are cytotoxic T cells stimulated to divide the same way that B cells are?

[joanna120728]

1) Does founder effect result in speciation always?

2) Is competitive inhibition always go with reversible inhibition, and non-competitive irreversible?

3) Describe a technique that could be used to compare the sequence of the mitochondrial DNA to confirm the arrangement of the phylogenetic tree?
Would DNA sequencing be an option? The more similar the sequence of nucleotides, the less time since divergence from common ancestor thus the more closely related they are.  The only answer given was DNA hybridisation

[galaxy21]

Hey...a few more questions...
1. Does carbon-14 dating have a minimum age of the fossil? My teacher has said 12 years, but I haven't seen this anywhere else.
2. Are glycolipids and glycoproteins used as receptors?
3. After how many years, roughly, is a similarity in traits not considered to have been from a common ancestor, but by convergent evolution?
4. With the final heating stage of DNA hybridisation, is it the point that the DNA strand completely separate, or when 50% of the bonds are broken that the temperature is noted to use to determine relatedness between species?

[Azim.m]

I don’t get the solutions. Could someone help me out please