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March 29, 2024, 02:04:14 am

Author Topic: VCE Biology Question Thread  (Read 3570623 times)  Share 

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eagles

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Re: VCE Biology Question Thread
« Reply #225 on: January 14, 2014, 11:24:47 am »
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"C3 plants cannot grow in hot areas because RuBisCO incorporates more oxygen into RuBP as temperatures increase. This leads to photorespiration, which leads to a net loss of carbon and nitrogen from the plant and can, therefore, limit growth. In dry areas, C3 plants shut their stomata to reduce water loss, but this stops CO2 from entering the leaves and, therefore, reduces the concentration of CO2 in the leaves. This lowers the CO2:O2 ratio and, therefore, also increases photorespiration. "

RazzMeTazz

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Re: VCE Biology Question Thread
« Reply #226 on: January 14, 2014, 11:34:45 am »
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"C3 plants cannot grow in hot areas because RuBisCO incorporates more oxygen into RuBP as temperatures increase. This leads to photorespiration, which leads to a net loss of carbon and nitrogen from the plant and can, therefore, limit growth. In dry areas, C3 plants shut their stomata to reduce water loss, but this stops CO2 from entering the leaves and, therefore, reduces the concentration of CO2 in the leaves. This lowers the CO2:O2 ratio and, therefore, also increases photorespiration. "

Thanks a ton! :)

Stick

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Re: VCE Biology Question Thread
« Reply #227 on: January 14, 2014, 11:48:15 am »
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Hi, I was wondering why does the rate of photorespiration in C3 plants increase at a higher temperature?
Is it because there is more light energy, so more ATP molecules and NADPH molecules are being formed in the light-dependent stage of photosynthesis, but in the Calvin-Benson cycle there is not enough carbon-dioxide molecules for them to 'fix' so once the carbon dioxide molecules run out, Rubisco starts to fix oxygen instead?

Thanks!

This is beyond the scope of the VCE Biology course.
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RazzMeTazz

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Re: VCE Biology Question Thread
« Reply #228 on: January 16, 2014, 01:19:30 am »
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This is beyond the scope of the VCE Biology course.

oh okay thanks for letting me know! :)

RazzMeTazz

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Re: VCE Biology Question Thread
« Reply #229 on: January 16, 2014, 01:20:58 am »
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Hi is the inner membrane of the chloroplasts what makes up the thylakoid membrane?
Or is the thylakoid membrane a third membrane of itself?
Because I read two different pieces of information from two different sources and so I was confused!
Thanks :)

Scooby

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Re: VCE Biology Question Thread
« Reply #230 on: January 16, 2014, 02:19:26 am »
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Hi is the inner membrane of the chloroplasts what makes up the thylakoid membrane?
Or is the thylakoid membrane a third membrane of itself?
Because I read two different pieces of information from two different sources and so I was confused!
Thanks :)



A chloroplast has an inner and outer membrane. The space within the inner membrane is referred to as the lumen of the chlorplast and is filled with a fluid called stroma. Within this lumen there are grana, which are stacks of these membrane-bound structures called thylakoids. The membranes of these thylakoids are called the thylakoid membranes (which makes sense :P). Thylakoids are hollow, and that hollow space within them is called the thylakoid lumen

The light-dependent stage of photosynthesis occurs on the thylakoid membranes

« Last Edit: January 16, 2014, 02:21:28 am by Scooby »
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RazzMeTazz

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Re: VCE Biology Question Thread
« Reply #231 on: January 16, 2014, 09:25:57 am »
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(Image removed from quote.)

A chloroplast has an inner and outer membrane. The space within the inner membrane is referred to as the lumen of the chlorplast and is filled with a fluid called stroma. Within this lumen there are grana, which are stacks of these membrane-bound structures called thylakoids. The membranes of these thylakoids are called the thylakoid membranes (which makes sense :P). Thylakoids are hollow, and that hollow space within them is called the thylakoid lumen

The light-dependent stage of photosynthesis occurs on the thylakoid membranes

That makes alot of sense now! Thanks for including the diagram as well, I was able to visualise it better!

:)

grannysmith

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Re: VCE Biology Question Thread
« Reply #232 on: January 16, 2014, 11:20:10 am »
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With regards to the reactants of photosynthesis, is it more correct to say that there are 12 molecules of H20 as opposed to 6 (considering both equations are balanced)?

Yacoubb

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Re: VCE Biology Question Thread
« Reply #233 on: January 16, 2014, 11:23:33 am »
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With regards to the reactants of photosynthesis, is it more correct to say that there are 12 molecules of H20 as opposed to 6 (considering both equations are balanced)?

You can use either! I personally opted for the 12 H2Os

Scooby

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Re: VCE Biology Question Thread
« Reply #234 on: January 16, 2014, 11:50:04 am »
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With regards to the reactants of photosynthesis, is it more correct to say that there are 12 molecules of H20 as opposed to 6 (considering both equations are balanced)?

If they ask for the net input per glucose molecule I'd say six
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Stick

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Re: VCE Biology Question Thread
« Reply #235 on: January 16, 2014, 11:54:56 am »
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With regards to the reactants of photosynthesis, is it more correct to say that there are 12 molecules of H20 as opposed to 6 (considering both equations are balanced)?

I always got told to put 12 on the left hand side and 6 on the right hand side, due to the fact that two separate stages are occurring in which 12 water molecules do react and 6 are produced per glucose molecule.
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vella97

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Re: VCE Biology Question Thread
« Reply #236 on: January 16, 2014, 03:52:37 pm »
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In reference to pages 29 & 185 of Cambridge checkpoints 2013:

Q: In fibrous proteins, the polypeptide chains are arranged in parallel to form long fibres or sheets. In globular proteins, the polypeptide chains are folded into compact spherical or globular shapes. Describe a distinctive property of a fibrous protein and explain how this property is due to the arrangement of its polypeptides?

The answer says that one of the properties is its elasticity. But I'm confused because silk is an example of a fibrous protein and I know that silk does NOT stretch due its tightly constructed beta pleats secondary structure.

Could someone please explain this to me??

Thanks!

MM1

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Re: VCE Biology Question Thread
« Reply #237 on: January 16, 2014, 04:38:20 pm »
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What type of proteins do 'free' ribosomes in the cytosol manufacture? I know ribosomes studded on the Rough E.R manufacture tertiary level proteins?
Also, does the E.R secrete its contents for the cell or for external cells? Can someone clarify this please? Thanks!

nerdmmb

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Re: VCE Biology Question Thread
« Reply #238 on: January 16, 2014, 04:45:29 pm »
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What type of proteins do 'free' ribosomes in the cytosol manufacture? I know ribosomes studded on the Rough E.R manufacture tertiary level proteins?
Also, does the E.R secrete its contents for the cell or for external cells? Can someone clarify this please? Thanks!

Both free ribosomes and ribosomes on the rough ER synthesis tertiary level proteins. The only difference is that proteins synthesised by the ribosomes on the Rough ER are packaged into vesicles and sent to the Golgi for further modification before being released via exocytosis.

Yacoubb

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Re: VCE Biology Question Thread
« Reply #239 on: January 16, 2014, 05:26:52 pm »
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What type of proteins do 'free' ribosomes in the cytosol manufacture? I know ribosomes studded on the Rough E.R manufacture tertiary level proteins?
Also, does the E.R secrete its contents for the cell or for external cells? Can someone clarify this please? Thanks!

Free ribosomes are the site of protein synthesis, for proteins that carry out their biological function within the cells they are produced. Ribosomes studded on the endoplasmic reticulum, which forms the rough endoplasmic reticulum organelle, synthesise proteins that carry out their biological function outside the cell in which they are produced.

The endoplasmic reticulum is an organelle made up of a network of membranous sacs, transporting substances within the cell and also partially modify the substances transported within the cell. It is the golgi apparatus that packages synthesised materials into vesicles that bud off the golgi body, and transport the synthesised materials out of the cell by exocytosis.