VCE Biology Question Thread

[DJA]

Thank you so much! Doing AOS 1 study atm and just consolidating the holes in my knowledge when I can't find the answers elsewhere. Cheers!

Question 1: Do lysosomes die in the process whereby they digest unwanted cell parts/damaged molecules/foreign molecules? (In essence, by digestion, do they self-destruct in the process or are they 're-usable' and can perform their processes multiple times?)

Question 2: Should we know the function of Peroxisomes and Endosomes for the VCE course?

[Yacoubb]

Thank you so much! Doing AOS 1 study atm and just consolidating the holes in my knowledge when I can't find the answers elsewhere. Cheers!

Question 1: Do lysosomes die in the process whereby they digest unwanted cell parts/damaged molecules/foreign molecules? (In essence, by digestion, do they self-destruct in the process or are they 're-usable' and can perform their processes multiple times?)

Question 2: Should we know the function of Peroxisomes and Endosomes for the VCE course?

(1.) Lysosomes are basically membrane-bound sacs that contain digestive enzymes called lysosymes. These lysozymes are secreted, the lysozymes break down the matter taken up by the cell, and the lysozyme, an enzyme, is neither used up nor consumed by this catabolic reaction. So essentially, no, the lysosomes are not destroyed in this instant.

2. You don't need to know much. I'd just remember that catalase, the enzyme that catalyses the breakdown of hydrogen peroxide, is contained in peroxisomes. Also, endosomes are just vesicles thar transport materials that enter the cell, to lysosomes, to undergo cellular digestion.

[Stick]

Thank you so much! Doing AOS 1 study atm and just consolidating the holes in my knowledge when I can't find the answers elsewhere. Cheers!

Question 1: Do lysosomes die in the process whereby they digest unwanted cell parts/damaged molecules/foreign molecules? (In essence, by digestion, do they self-destruct in the process or are they 're-usable' and can perform their processes multiple times?)

Question 2: Should we know the function of Peroxisomes and Endosomes for the VCE course?

Just making a big point of this. Do not say that non-living material (e.g. enzymes) die. This is a one way trip to getting zero marks for a short answer question, even if the other parts of your response are correct.

[DJA]

Just making a big point of this. Do not say that non-living material (e.g. enzymes) die. This is a one way trip to getting zero marks for a short answer question, even if the other parts of your response are correct.

Got it. Thanks for the heads up.

Are there any cells in the body that 'self-destruct' in order to consume/breakdown foreign material/invading antigens? (I'm thinking of phagocytes and lymphocytes here but I am really NOT sure.

If there are, would it be correct to say that these kinds of cells die in the process as these cells are living?

[alondouek]

Got it. Thanks for the heads up.

Are there any cells in the body that 'self-destruct' in order to consume/breakdown foreign material/invading antigens? (I'm thinking of phagocytes and lymphocytes here but I am really NOT sure.

If there are, would it be correct to say that these kinds of cells die in the process as these cells are living?

I'm not aware of any cells that specifically self-destruct to destroy foreign bodies, but all cells will trigger apoptosis as a mode of damage control. As these are regular cells, they definitely are living!

[MM1]

Why are proteins not preferred energy sources whilst carbohydrates are? What are the reasons?

[DJA]

Why are proteins not preferred energy sources whilst carbohydrates are? What are the reasons?

My understanding of this is because carbohydrates (I'm thinking more specifically of glucose here which is the monosaccharide which comprises a lot of polysaccharides and disaccharides such as maltose, starch and glycogen) are used in aerobic cell respiration which is the primary mode for cells to create energy to allow it to function.

Cellular respiration is the process whereby living cells get their energy to function and this process requires glucose (C6H12O6) as a critical part of the equation
C6H12O6 + O2 ---> CO2 + H2O (+ Energy)
Thus carbohydrates are the preferred energy source.

Whereas proteins function primarily in structural roles (collagen and keratin), contractile roles (myosin and actin found in muscle tissue) and catalytic/regulartory roles etc. Note that amino acids are the basic subunits of proteins. While certain amino acids can aid energy productions, they are not directly part of any biological process to produce energy as far as I know.

[DJA]

My question is what is the difference between the 5' and 3' ends of a DNA strand and more importantly, is this knowledge required for the VCE course?

Thanks in advance.

[vox nihili]

My question is what is the difference between the 5' and 3' ends of a DNA strand and more importantly, is this knowledge required for the VCE course?

Thanks in advance.

The 3' is the -OH end and the 5' is the phosphate end. Yes this knowledge is required for the VCE course. You will have to know the direction of replication and transcription of DNA with respects to this configuration.

[Stick]

The 3' is the -OH end and the 5' is the phosphate end. Yes this knowledge is required for the VCE course. You will have to know the direction of replication and transcription of DNA with respects to this configuration.

Here's a good way to remember:

Five - Phosphate (same sound)
Three - Free (no phosphate) (similar word)

[DJA]

Thanks both of you!

I'm assuming that the way the nucleotides bond together to form long chains (DNA and RNA) is through a condensation reaction between the -phosphate group and the -OH group of two nucleotides?

[alondouek]

Thanks both of you!

I'm assuming that the way the nucleotides bond together to form long chains (DNA and RNA) is through a condensation reaction between the -phosphate group and the -OH group of two nucleotides?

DNA and RNA polymerise by connecting part of the phosphate group to one of the deoxyribose/ribose carbons (5' if I recall correctly). Here's a really good link that explain DNA polymerisation: http://www.chem.wisc.edu/deptfiles/genchem/netorial/modules/biomolecules/modules/dna1/dna13.htm

[DJA]

What is the point of the DNA strands found in chloroplasts?

[alondouek]

ctDNA has a number of purposes, for example protein production (as with many other types of DNA) for photosynthetic processes.

[Yacoubb]

What is the point of the DNA strands found in chloroplasts?

For the purposes of VCE Biology, it would be sufficient to know 2 things:
~ ctDNA provides the set of genetic instructions required to synthesise specific proteins required for photosynthesis (e.g. the enzyme RuBisCO).
~ ctDNA provides evidence for the endosymbiotic theory of evolution (which you'll cover more in unit 4).