HSC Biology Question Thread

[vox nihili]

That's correct I forgot to add that in, didn't know about the dendritic cells however

Given that you don't know it, I'm going to presume it's probably not part of the course, so don't worry about dendritic cells. For your interest though:




Dendritic cells pretty much just chill out in the lymph nodes, sampling the environment. So antigens drain from tissues into the lymph nodes, where they're taken up by dendritic cells and presented on MHC class II molecules. These cells are actually the most important when it comes to activating T-helper cells. The role of MHC class II molecules on macrophages and B-cells, although important, is fairly minor compared to dendritic cells.

They're not really covered on the VCE course either and ever since learning about them I've always felt a bit ripped off about that hahah

[Skidous]

So basically they're like B-Cells and Macrophages, but in the lumph and are the most important part of the specific immune response, right?

[vox nihili]

So basically they're like B-Cells and Macrophages, but in the lumph and are the most important part of the specific immune response, right?

Hmmmm, kind of. B-cells, macrophages and dendritic cells are all called antigen-presenting cells, because they can present antigen on MHC class II molecules.
The role of the dendritic cell is to sit in the lymph and activate T-cells. They really are the cell responsible for activation of T-cells.

Macrophages and B-cells present antigen not so much to activate T-cells, but rather, to get help from them.

[studybuddy7777]

Hmmmm, kind of. B-cells, macrophages and dendritic cells are all called antigen-presenting cells, because they can present antigen on MHC class II molecules.
The role of the dendritic cell is to sit in the lymph and activate T-cells. They really are the cell responsible for activation of T-cells.

Macrophages and B-cells present antigen not so much to activate T-cells, but rather, to get help from them.

Hence why they are referred to in some textbook as Helper T Cells (my teacher says this)

(Soz about that stuff up I meant to write T cells not B cells)

[anotherworld2b]

I have a few questions. For our investigation we were testing the rate of human urine production.
Our hypothesis was that the consumption of caffeine increases the rate of human urine production.
Our experimental group was caffeine (ice tea) and control group was cordial.
In our results the graph of the cordial spiked in the amount of urine produced before the graph of peach ice tea.
Why would this happen? Errors could have occurred? I though caffeine would increase the rate of human urine production?
I also wanted to ask for the discussion would be appropriate to explain what should have happened?
Eg ADH is involved in fluid, in the body; it causes the kidneys to reabsorb water. When ADH is not present there is decreased water reabsorption in the kidneys, which, in turn increases the need to urinate?

Could I have a answer as soon as possible? I have to finish writing my report to hand in tomorrow

[Skidous]

Hello Anotherworld2b, glad to see you here on this thread over the other one.

For the hypothesis, you need it to be longer using IF...THEN...BECAUSE
As for the experimental group, the control should've have been a plain substance such as regular water and then the variables should be something like a diuretic (like coffee) and an anti-diuretic/substance that is not as diuretic as water.
This is probably the error you are concerned about, there also may be issues with the experimental group having full bladders BEFORE consuming coffee or cordial which may have affected the results.
Caffeine IS a Diuretic so it does increase urine production (to remove the toxin from the body), as for cordial, I'm not sure of the diuretic properties so I cannot say for sure whether it is or not, but it would be safe to assume it's not a diuretic and it was an error with the experimental group when the experiment was conducted.

Your discussion should explain the validity, reliability and accuracy, indicating how you can improve upon all 3 of them, and you should DEFINITELY explain what should have happened so you acknowledge that the experiment was flawed, what the expected result was, why you didn't achieve that and how it can be improved in the future.

Hope this helps, Skidous

[anotherworld2b]

thank you for your help skidous
Would this be a better hypothesis?

If the concentration of caffeine consumed increases then the rate of human urine production will increase over the duration of two hours.

-2 hours is the period in which this experiment was conducted

[Skidous]

that is better but you need the reason why, so BECAUSE caffeine is a diuretic that will increase urine production to remove toxins from the body

Note: You should also name the toxin/s being removed

[anotherworld2b]

If the concentration of the diuretic caffeine consumed increases then the rate of human urine production will increase over the duration of two hours to remove toxins such as urea, creatinine and uric acid to maintain the concentration of material in the body's fluids.

For the introduction of the report what information would be required? I have info about the kidney, permeability of the tubules changing due to the different compositions of material in each respective liquid.

Would this be right for the discussion?
I wrote that
Caffeine is a diuretic that inhibits reabsorption of sodium ions and the antidiuretic hormone(ADH) causing urination. ADH is involved in selective reabsorption by acting on the permeability of the distal convoluted tubule and collecting duct preventing the production  of concentrated urine. This causes dehydration because it inhibits the antidiuretic hormone(ADH).ADH is involved in fluid storage in the body; it causes the kidneys to reabsorb water. When ADH is not present there is decreased water reabsorption in the kidneys, which, in turn increases the need to urinate?

[Skidous]

The introduction should contain any information that can be used for the experiment, so the information about caffeine, diuretics and the other stuff you mentioned should go in there.

As for the discussion you need to talk about
Validity: Variables (Independent, Dependent, Control) and assess whether it was a valid experiment and how it can be more valid
Reliability: Repetition (Number of trials to calculate an average in order to produce consistent results) and assess the reliability of the experiment
Accuracy: Errors (Error margins of measurement tool [such as +/- 0.5ml in a measuring cylinder or +/- 0.5ms on a stopwatch] and experimental errors or issues that may have occurred) and assess the accuracy of the experiment and how to improve that accuracy
Then you need to discuss the results of the experiment and if they showed the expected result to confirm or disprove the hypothesis. This needs to be explained and why it was confirmed/disproved.
The discussion you wrote would be better for the introduction rather than the discussion.

Hope this helps

[Bparker]

Hey guys!
Two quick questions:
1. Could someone very simply explain what form lipids are transported in the body, and also
2. In an exam, if asked about justifying the appropriateness of an experiment - how would you go about answering that?
Thanks!

[Skidous]

Hey Bparker

1: Lipids are transported in the body in the form of Glucose, Amino acids, Fatty Acids and Glycerol, Nucleotides.. Glucose and Amino Acids enters the bloodstream through water (water soluble) and then dissolves in the plasma.
Lipids (Fatty Acids and Glycerols) Only some enter the bloodstream directly, whilst most need to be packaged into small droplets which pass the lymphatic system into the bloodstream.

2: When justifying whether an experiment is appropriate you need to consider what is being tested by the question and whether the experiment actually is trying to test the same thing. IF that is the case then you need to go into the validity, reliability and accuracy of the experiment. These points also have to be explained (using cause and effect language)

[Bparker]

Hey Bparker

1: Lipids are transported in the body in the form of Glucose, Amino acids, Fatty Acids and Glycerol, Nucleotides.. Glucose and Amino Acids enters the bloodstream through water (water soluble) and then dissolves in the plasma.
Lipids (Fatty Acids and Glycerols) Only some enter the bloodstream directly, whilst most need to be packaged into small droplets which pass the lymphatic system into the bloodstream.

2: When justifying whether an experiment is appropriate you need to consider what is being tested by the question and whether the experiment actually is trying to test the same thing. IF that is the case then you need to go into the validity, reliability and accuracy of the experiment. These points also have to be explained (using cause and effect language)

Very clear response! Thankyou Skidous!!

[Skidous]

No problem man

[vox nihili]

Hey Bparker

1: Lipids are transported in the body in the form of Glucose, Amino acids, Fatty Acids and Glycerol, Nucleotides.. Glucose and Amino Acids enters the bloodstream through water (water soluble) and then dissolves in the plasma.
Lipids (Fatty Acids and Glycerols) Only some enter the bloodstream directly, whilst most need to be packaged into small droplets which pass the lymphatic system into the bloodstream.

2: When justifying whether an experiment is appropriate you need to consider what is being tested by the question and whether the experiment actually is trying to test the same thing. IF that is the case then you need to go into the validity, reliability and accuracy of the experiment. These points also have to be explained (using cause and effect language)

As usual, thanks for doing such a good job on this forum Skidous!

Just going to jump in on this one though. Lipid≠glucose≠amino acid≠nucleotide.

Lipids include things like sterols (including cholesterol), triglycerides and phospholipids. Glucose is a carbohydrate, amino acids are the building blocks of proteins and nucleotides the building blocks of nucleic acids. If you mean to say that lipids are used as substrates in the synthesis of these things, of course you would be exactly right; however, once they are turned into these things they cease to be lipids.

You did correctly identify how lipids are transported around the blood stream. They are packaged into small droplets, with proteins to hold them in together. They can, however, be directly placed into the bloodstream without having to worry about the lymph (only when lipids are absorbed do they travel in the lymph).