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March 28, 2024, 07:26:29 pm

Author Topic: VCE Biology Question Thread  (Read 3570286 times)  Share 

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-Lilac-

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Re: VCE Biology Question Thread
« Reply #13500 on: June 12, 2021, 04:05:50 pm »
+1
Hi,
In humoral immunity, it starts off with a B cell receptor recognising the foreign antigen that's on a pathogen, with a helper t cell stimulating the B cell and then differentiation occurring. But where does the B cell get this receptor to recognise a specific foreign antigen in the first place? Would it have something to do with the APCs from the second line of defence? If so, how exactly would that be?
Thanks in advance!

This is not VCE knowledge, but APCs are really only involved in the negative selection of B cells during development. The actual B cell receptors are formed by what is called somatic recombination during B cell development in the bone marrow. This is where different gene segments come together and form the gene for the B cell receptor. Many different recombination events are possible (as each segment has many options to 'choose' from) and during this recombination, there is also random addition of nucleotides in the gene which also increases the diversity. As a result each B cell will have a unique receptor and at least one B cell should be able to recognize any one specific foreign antigen. 
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biology1234

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Re: VCE Biology Question Thread
« Reply #13501 on: June 15, 2021, 02:52:28 pm »
0
The bromide atom gains an electron to form the bromide ion Br -. How many electrons does bromide have in its outer shell.
a) 1  b) 3  c) 8  d) 7

I am thinking the answer is either 1 or 8, if someone could help explain would appreciated

caffinatedloz

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Re: VCE Biology Question Thread
« Reply #13502 on: June 15, 2021, 03:02:17 pm »
+3
The bromide atom gains an electron to form the bromide ion Br -. How many electrons does bromide have in its outer shell.
a) 1  b) 3  c) 8  d) 7

I am thinking the answer is either 1 or 8, if someone could help explain would appreciated

Not really a bio question but I’ll give it a go.

The sub-shell notation for bromine is:  1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p5

As the 3d sub-shell is full it will be the 4p sub-shell that gains an electron. That gives it 8 total electrons in the valence shell. The answer (I think) is C.

Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #13503 on: June 17, 2021, 03:00:03 pm »
0
For this question would it be a

Which of the following properties prevents the ligands of cell-surface receptors from entering the cell?
A. The molecules are hydrophilic and cannot diffuse through the hydrophobic interior of the plasma membrane
B. The molecules are hydrophobic and cannot diffuse through the hydrophilic interior of the plasma membrane
C. The molecules are attached to transport proteins that deliver them through the bloodstream to target cells
D. The ligands are able to diffuse through the membrane directly influencing gene expression upon receptor binding

caffinatedloz

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Re: VCE Biology Question Thread
« Reply #13504 on: June 17, 2021, 07:46:36 pm »
+5
Which of the following properties prevents the ligands of cell-surface receptors from entering the cell?
I agree with you.

We know that the fatty acid tails that make up the interior of the plasma membrane are hydrophobic. Therefore, A makes sense and we can rule out B.

The transport proteins mentioned in option C would allow the receptors to enter the cell, as transport proteins are transmembrane stuctures. That means C is also incorrect.

As the question states the ligands interact with cell-surface receptors, we know that they cannot enter the cell and influence gene expression, meaning D is also incorrect.

As such, A is the only possible correct answer.

Corey King

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Re: VCE Biology Question Thread
« Reply #13505 on: June 19, 2021, 02:55:09 pm »
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^Just fyi we can't provide any specific information on what to do for your sac, it's against vcaa rules. I'll try to come back later and post some more general advice when I get a minute but just wanted to pop in and say be careful because they can come after you for breaching academic integrity by collaborating for that.

Oh I see, thanks for letting me know!

Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #13506 on: June 19, 2021, 05:18:45 pm »
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A substitution mutation changes a codon (TTC) to TCC. TTC codes for lysine, TCC codes for arginine. How will this mutation affect the resultant protein?
A lysine replaces arginine at one position in the protein
B arginine replaces lysine at one position in the protein
C lysine replaces arginine throughout the protein
D arginine replaces lysine throughout the protein

Would this be b or would it be throughout the protein

Sine

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Re: VCE Biology Question Thread
« Reply #13507 on: June 19, 2021, 06:59:35 pm »
+5
A substitution mutation changes a codon (TTC) to TCC. TTC codes for lysine, TCC codes for arginine. How will this mutation affect the resultant protein?
A lysine replaces arginine at one position in the protein
B arginine replaces lysine at one position in the protein
C lysine replaces arginine throughout the protein
D arginine replaces lysine throughout the protein

Would this be b or would it be throughout the protein
only a single codon in the polypeptide would be changed with a single substitution mutation

Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #13508 on: June 20, 2021, 11:35:46 am »
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Would it be wrong If you said Down syndrome was caused by a mutation

Is the allele for blood group O I^i I^i or just ii or are both fine

Sine

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Re: VCE Biology Question Thread
« Reply #13509 on: June 20, 2021, 01:24:37 pm »
+5
Would it be wrong If you said Down syndrome was caused by a mutation

Is the allele for blood group O I^i I^i or just ii or are both fine
For your first question yes i think that would be wrong since it is an entire chromosomal abnormality not specific nucleotide base changes. Also the primary cause is usually abnormal cell division.

For your second question the O blood group ii is usually fine for the genotype

emonerd

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Re: VCE Biology Question Thread
« Reply #13510 on: June 20, 2021, 02:49:33 pm »
0
Hi! Just wondering if anyone knows regarding this study design dot point:
 - significant changes in life forms in Earth’s geological history including the rise of multicellular organisms, animals
on land, the first flowering plants and mammals
How much detail do students have to go into with memorising the different periods and eras? Is it just to know which ones correspond to the first flower plants and mammals?
Thanks!
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Owlbird83

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Re: VCE Biology Question Thread
« Reply #13511 on: June 20, 2021, 04:14:57 pm »
+6
Hi! Just wondering if anyone knows regarding this study design dot point:
 - significant changes in life forms in Earth’s geological history including the rise of multicellular organisms, animals
on land, the first flowering plants and mammals
How much detail do students have to go into with memorising the different periods and eras? Is it just to know which ones correspond to the first flower plants and mammals?
Thanks!

Hi emonerd!

I found this in VCAA's biology FAQs that might help answer your question:
Quote
Question: Are students required to know dates for the changes in life forms in Earth’s geological history, and which specific life forms should be considered?
Answer: No, although specific dates are not required students should understand geological
time is divided into sections, for example eras and periods.
Students should understand that Earth’s history can be represented on a geological time scale
as a ‘calendar’ of chronological events: different kinds of organisms do not appear randomly but appear in a constant order as the law of fossil succession. The fossil record shows the changes that have occurred in the types of organisms living over time.
Question: Are students required to understand why biodiversity has changed over time?
Answer: Yes, students should have a general understanding that major changes in Earth’s conditions such as available land masses (plate tectonics), atmospheric composition, temperature, climate and biodiversity have consequences. For example, the appearance of multicellular animals in the fossil record can be related to build up of oxygen in the atmosphere derived from photosynthetic cyanobacteria. As another example, flowering plants (angiosperms), birds, and mammals rapidly radiated into niches left vacant by the extinction of the dinosaurs.
I think it's more important to know the order major organisms mentioned in the dot point evolved than the specific times/names of periods.
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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #13512 on: June 21, 2021, 08:05:06 pm »
0
Antidiuretic hormone (ADH) affects only a small number of cells in the body because:
A only it’s target cells are exposed to ADH.
B only it’s target cells contain ADH receptors
C it is unable to enter non target cells
D non target cells hydrolyse ADH

Would this be b

Billuminati

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Re: VCE Biology Question Thread
« Reply #13513 on: June 21, 2021, 08:12:47 pm »
+4
Antidiuretic hormone (ADH) affects only a small number of cells in the body because:
A only it’s target cells are exposed to ADH.
B only it’s target cells contain ADH receptors
C it is unable to enter non target cells
D non target cells hydrolyse ADH

Would this be b

Yep, only distal renal tubule and collecting duct epithelial cells express vasopressin receptors.
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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #13514 on: June 22, 2021, 06:30:57 pm »
0
In a chemical reaction, 1,3-bisphosphoglycerate + ADP yields 3-phosphoglycerate plus ATP. What is the delta G for this reaction?
A greater than zero
B equal to zero
C less than zero
D cannot be determined

Why is this c can someone explain