VCE Biology Question Thread

[BakedDwarf]

A couple of questions on U3 AOS2

Do need to know about specific types of regulation?
AND
What knowledge are we required of Action Potentials?

Not too sure what you mean by the first question (do you mean factors controlled, such as body temperature, blood volume etc?)

For the second question, I think it is required to know that the axon is negatively charged inside relative to the outside of the membrane during resting potential, which is maintained by sodium-potassium pumps. When the electrical impulse arrives, the membrane becomes permeable to sodium ions, which diffuse in rapidly, depolarising the membrane and is now positive relative to the outside (action potential)

[Sine]

Not too sure what you mean by the first question (do you mean factors controlled, such as body temperature, blood volume etc?)

Yes specific types such as blood glucose, osmoregulation.

Thanks for the help 

[cosine]

A couple of questions on U3 AOS2

Do need to know about specific types of regulation?
AND
What knowledge are we required of Action Potentials?

What knowledge are we required of Action Potentials?

An action potential is initially stimulated when a stimulus is received, the action potential of the nerve cell propagates along the axon towards the axon terminals. During the propagation of the action potential, the cell membrane is polarised, and so an influx of Sodium and Potassium ions diffuse in/out along the concentration gradient as there is a higher concentration of potassium inside the cell, and a higher concentration of sodium outside the cell. Once the action potential moves along, the membranes is said to become 'depolarised' and returns to it's normal state (resting potential) and so sodium ions diffuse back out and potassium ions diffuse back in. When the action potential reaches the axon terminals, there is also an influx of Calcium ions present and this causes neurotransmitters, enclosed in vesicles, to fuse with the pre-synaptic membrane and the neurotransmitters are released. Now the gap between the two adjacent cells is called the synaptic cleft or synapse. Once the neurotransmitters are released, they diffuse down their concentration gradient to the adjacent post synaptic membrane. On this post synaptic membrane are specialised receptors that are complementary to the ligands, and so once the ligand/neurotransmitter-receptor complex is formed, the neurone's ion channels open, and if sufficient ion channels are opened, then the action potential is generated in the new neurone.

Do we need to know about specific types of regulation?

If by regulation you mean homeostatic feedbacks, then I think yes. I have completed a couple exams from 2006-2008 and I think in two of those I had to actually name a feedback mechanism, such as the regulation of glucose levels in the blood, and actually include the mechanisms involved and the regulatory steps to reduce/increase blood glucose levels.

[heids]

^ NOTE: Just because you do something in a pre-2013 exam does not mean you now have to know it.  (Though it's always great to know for funsies ).

With this example, I don't actually know, though; while I doubt this is necessary as homeostasis has more or less been taken out, I still learnt the glucose feedback mechanism.  It's a great example to help you get what's going on anyway.

[cosine]

The specific structure of a phospholipid is a glycerol backbone with two fatty acids acid attached, and in the third position there is a negatively charged phosphate group attached to the glycerol backbone. The fatty acids don't have to be the same, they can be different, in fact one could be monounsaturated and the other could be polyunsaturated, as an example.

The Endocrine system essentially is involved in the sequestration of hormones that travel far distances and act on tissue that is at distance to the secretion tissues. Conversely in the paracrine system  the molecule  travel a short distance, and in the exocrine system the molecule secreted acts on the tissue that secreted it. Usually the term "hormone" is more generally attached to the molecules that operate within the endocrine system.

Not everything in the Endocrine system is a "gland" per-say. For example, the testis, ovaries, thymus and pancreas all secrete hormones and are part of the endocrine system but they're not "glands" by their anatomical definitions.

So to define Endocrine System, would this suffice:

The endocrine system are the tissues/glands involved that produce and secrete specific hormones that travel far distances from the site of secretion, and bind upon specific receptors to initiate a specific cellular response.

Also I read on the study design that paracrine system and autocrine systems are not required for the course. But is the exocrine system required? Isn't it just the glands/tissues that produce hormones that are released as pheromones (released outside the organism, not inside).

Also also, how much about pheromones do we need to know, rather than they are hormones released mainly by insects that act as sex attractants within the same species?

Also x3, are we required to know about neurohormones? Because it's no where on the study design, but found in my book.

Thank you

[BakedDwarf]

What knowledge are we required of Action Potentials?

An action potential is initially stimulated when a stimulus is received, the action potential of the nerve cell propagates along the axon towards the axon terminals. During the propagation of the action potential, the cell membrane is polarised, and so an influx of Sodium and Potassium ions diffuse in/out along the concentration gradient as there is a higher concentration of potassium inside the cell, and a higher concentration of sodium outside the cell. Once the action potential moves along, the membranes is said to become 'depolarised' and returns to it's normal state (resting potential) and so sodium ions diffuse back out and potassium ions diffuse back in. When the action potential reaches the axon terminals, there is also an influx of Calcium ions present and this causes neurotransmitters, enclosed in vesicles, to fuse with the pre-synaptic membrane and the neurotransmitters are released. Now the gap between the two adjacent cells is called the synaptic cleft or synapse. Once the neurotransmitters are released, they diffuse down their concentration gradient to the adjacent post synaptic membrane. On this post synaptic membrane are specialised receptors that are complementary to the ligands, and so once the ligand/neurotransmitter-receptor complex is formed, the neurone's ion channels open, and if sufficient ion channels are opened, then the action potential is generated in the new neurone.

Isn't an action potential just the change in electrical potential (depolarisation) along a neurone?

Yes specific types such as blood glucose, osmoregulation.

I asked my teacher that question a while ago and she said it is not required to actually know how homeostatic mechanisms work because they will just provide the necessary information in the exam. However, I still believe it is beneficial to understand glucose, temperature, water and oxygen/carbon dioxide regulation since it will also enhance your understanding of homeostasis.

[heids]

So to define Endocrine System, would this suffice:

The endocrine system are the tissues/glands involved that produce and secrete specific hormones that travel far distances from the site of secretion, and bind upon specific receptors to initiate a specific cellular response.

Also I read on the study design that paracrine system and autocrine systems are not required for the course. But is the exocrine system required? Isn't it just the glands/tissues that produce hormones that are released as pheromones (released outside the organism, not inside).

Also also, how much about pheromones do we need to know, rather than they are hormones released mainly by insects that act as sex attractants within the same species?

Also x3, are we required to know about neurohormones? Because it's no where on the study design, but found in my book.

Thank you

1.  You don't have to know a definition of the endocrine system - the point is how the stimulus-response model works, so while you do have to vaguely know what it's all about, they won't expect specifics (I hope).

2.  No, you don't have to know anything about exocrine/paracrine/autocrine stuff - just have to know that a hormone can travel to the same cell, cells in nearby tissues, and/or distant cells through the bloodstream.

3.  Pheromones are signalling molecules released by animals into their environment, enabling them to communicate with members of their own species.  (VCAA definition I think?)  They can attract mates, induce mating activity, mark territories, signal alarm, and make food trails.  That's it.

4.  Neurohormones - nah, just briefly know what they are, no need for any detail.

P.S.  As always, please correct me anyone if I'm wrong - judging what the evil VCAA needs and doesn't need is extremely difficult.

[cosine]

1.  You don't have to know a definition of the endocrine system - the point is how the stimulus-response model works, so while you do have to vaguely know what it's all about, they won't expect specifics (I hope).

2.  No, you don't have to know anything about exocrine/paracrine/autocrine stuff - just have to know that a hormone can travel to the same cell, cells in nearby tissues, and/or distant cells through the bloodstream.

3.  Pheromones are signalling molecules released by animals into their environment, enabling them to communicate with members of their own species.  (VCAA definition I think?)  They can attract mates, induce mating activity, mark territories, signal alarm, and make food trails.  That's it.

4.  Neurohormones - nah, just briefly know what they are, no need for any detail.

P.S.  As always, please correct me anyone if I'm wrong - judging what the evil VCAA needs and doesn't need is extremely difficult.

Thank you Bangali_lok xD

Also is the feedback loops (drawing them) required for the exams?

So pheromones are not just sex attractants? o.O

Also what exactly are neurohormones?

[pi]

Also what exactly are neurohormones?

Pretty much any hormone secreted by a neuroendocrine cell For example cells in the hypothalamus secrete neurohormones such as oxytocin and vasopressin.

In all honesty, I haven't seen the term being widely used. Most people use "hormone" or "neurotransmitter" depending on the situation.

Also is the feedback loops (drawing them) required for the exams?

I'd imagine if they did ask, they'd give you the information required to construct it. But I doubt it.

[cosine]

Pretty much any hormone secreted by a neuroendocrine cell For example cells in the hypothalamus secrete neurohormones such as oxytocin and vasopressin.

In all honesty, I haven't seen the term being widely used. Most people use "hormone" or "neurotransmitter" depending on the situation.

I'd imagine if they did ask, they'd give you the information required to construct it. But I doubt it.

Cheers pi

Haha you have two identities, in math and inorganic phosphate in bio xD

[cosine]

Question 10:
How can I go about doing this question? I know that lymph nodes are the sites where the antigens/pathogens are introduced to the lymphocytes, so if these lymph nodes are removed, I would expect to see either: infections in the site of removal as there is a deficiency of lymphocytes but still have no idea how to tackle it

Question  24:
Obviously either neurotransmitters or neurohormones. But as Pi said above, neurohormones are signalling molecules secreted by neuroendocrine cell (neuro = brain right?) so why is the answer neurotransmitters, and not neurohormones?

EDIT: for question 24, I have a breakthrough. Is the correct answer neurotransmitters, because the question says what type of molecule is released between two neurones, meaning that the molecule would be neurotransmitters, and not neurohormones because neurohormones are hormones produced by neuroendocrine cells, and so although the question is tricking us and talking about the brain, the signalling molecules between two adjacent neurones are NOT hormones (learnt this the hard way )

Is that true for q24? Thank you

[pi]

Q10 - Essentially the lymph can't drain (eventually they drain into the subclavian veins, not that you need to know this specific detail!) because of the dissection of the axillary lymph nodes. Hence, there is a build up of lymphatic fluid more distal to that removal (ie. in the arm), and that fluid (as the name suggests), would contain lymphocytes.

Q24 - Essentially what you have said. Best to keep things simple, neurotransmitters are the communication between two neurons. While the molecules may also be neurohormones in other situations around the body, in this instance, neurotransmitters is the best answer.

edit: "neuro" doesn't mean "brain", it means "nerve" I like to think of a neurohormone as a substance released from a nerve that acts on a cell that isn't a nerve. Whether that's correct or not, I'm not 100% sure, as I don't personally use the term at all. I'm sure someone who does biomed/science and some hardcore biochem can clarify the definition for you though.

[thushan]

Pi - you practically got it right; it's a signalling molecule that goes from receptor to effector via the circulation, that happens to be secreted by a neuron. The main examples are oxytocin and ADH.

[EspoirTron]

So to define Endocrine System, would this suffice:

The endocrine system are the tissues/glands involved that produce and secrete specific hormones that travel far distances from the site of secretion, and bind upon specific receptors to initiate a specific cellular response.

Also I read on the study design that paracrine system and autocrine systems are not required for the course. But is the exocrine system required? Isn't it just the glands/tissues that produce hormones that are released as pheromones (released outside the organism, not inside).

Also also, how much about pheromones do we need to know, rather than they are hormones released mainly by insects that act as sex attractants within the same species?

Also x3, are we required to know about neurohormones? Because it's no where on the study design, but found in my book.

Thank you

Sorry got my terms a bit wrong. It shouldn't be exocrine, autocrine molecules are secreted from a cell and bind to autocrine receptors on the same cell and exert an effect.

[cosine]

Which of the following are products of BOTH aerobic and anaerobic cellular respiration in humans?
A. ATP and carbon dioxide
B. Pyruvate and ATP
C. Pyruvate and lactate
D. Lactate and carbon dioxide

Answer: A

I think the wording on this one is weird, because it says products of both, so what comes out of anaerobic respiration AND aerobic respiration. During glycolysis pyruvate is produced, and then if no oxygen is present then the pathway is anaerobic. So pyruvate is a product of anaerobic respiration. But how is it also a product of aerobic respiration? When we talk about aerobic respiration, do we consider all three steps (glycolysis, krebs cycle and ETC) as one, but in anaerobic respiration we only consider glycolysis by itself?