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March 29, 2024, 04:43:15 am

Author Topic: VCE Biology Question Thread  (Read 3570775 times)  Share 

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Tyleralp1

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Re: VCE Biology Question Thread
« Reply #990 on: March 05, 2014, 08:29:23 pm »
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Yeah, when temperatures become too low, the movement of substrates + enzymes is incredibly slow. From my reading, the enzyme simply becomes inactive, or catalyzes at low rates. It is a reversible thing, and the structure doesn't change.
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Re: VCE Biology Question Thread
« Reply #991 on: March 05, 2014, 08:34:58 pm »
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I've heard that at extremely low temperatures, the enzyme actually denatures. Is this true??
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alchemy

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Re: VCE Biology Question Thread
« Reply #992 on: March 05, 2014, 08:36:16 pm »
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I've heard that at extremely low temperatures, the enzyme actually denatures. Is this true??

At extremely low temperatures, the enzymes can become inactivated but not denatured.

howlingwisdom

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Re: VCE Biology Question Thread
« Reply #993 on: March 05, 2014, 09:34:38 pm »
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When an enzyme is inactive, molecular movement is so slow that the substrate barely makes contact with the active site (hence on temperature  enzyme activity graphs, it starts at 0)

EDIT: spelling, wrote this too fast :P
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vox nihili

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Re: VCE Biology Question Thread
« Reply #994 on: March 05, 2014, 10:33:05 pm »
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When an enzyme is inactive, molecular movement is so slow that the substrate barely makes contact with the active site (hence on temperature  enzyme activity graphs, it starts at 0)

EDIT: spelling, wrote this too fast :P

This is part of it, but not all of it. It means that the proportion of molecules that have activation energy sufficient enough to cause the reaction is lower, because that's what temperature is a record of, the kinetic energy of a system. So it's not that they're not making contact, they are, that contact just isn't forceful enough to supply the energy needed to start the reaction.
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RazzMeTazz

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Re: VCE Biology Question Thread
« Reply #995 on: March 06, 2014, 10:57:45 am »
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In the light dependent reactions of photosynthesis, when the energy provided by the excited electrons is used to pump hydrogen ions into the lumen, where are these hydrogen ions coming from? Is it from the water molecules that are split up?

And when they say that NADP+ becomes reduced into NADPH, when it combines with a hydrogen ion, how is this so?
I thought when something is reduced it gains electrons, not protons?

So confused :/

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Re: VCE Biology Question Thread
« Reply #996 on: March 06, 2014, 11:25:42 am »
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In the light dependent reactions of photosynthesis, when the energy provided by the excited electrons is used to pump hydrogen ions into the lumen, where are these hydrogen ions coming from? Is it from the water molecules that are split up?

The H+ ions came from the break down of water.
2H20 ---> 2H+ + O2 + 2e-
 
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alchemy

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Re: VCE Biology Question Thread
« Reply #997 on: March 06, 2014, 06:49:26 pm »
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And when they say that NADP+ becomes reduced into NADPH, when it combines with a hydrogen ion, how is this so?
I thought when something is reduced it gains electrons, not protons?

Yes, when something is reduced it gains electrons but, Hydrogen has one electron, remember? Therefore, in this context, it can reduce NADP+ to NADPH. However, the idea of hydrogen having electrons, or otherwise, is interchangeable. For bio, you just need to know that it reduces NADP+.

RazzMeTazz

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Re: VCE Biology Question Thread
« Reply #998 on: March 08, 2014, 01:27:04 am »
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Oh so it combines with hydrogens, not hydrogen ions?

Because hydrogen ions are just protons right?

Thanks!

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Re: VCE Biology Question Thread
« Reply #999 on: March 08, 2014, 10:45:19 am »
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Re: VCE Biology Question Thread
« Reply #1000 on: March 08, 2014, 11:37:34 am »
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SAC 2: an investigation of enzyme action

TITLE: Estimating relative levels of catalase from a variety of sources.
 
AIM: To test for the relative amounts of Catalase enzyme in a variety of organic sources

Does anyone know what the dependent variable will be in this experiment?

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Re: VCE Biology Question Thread
« Reply #1001 on: March 08, 2014, 12:10:39 pm »
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SAC 2: an investigation of enzyme action

TITLE: Estimating relative levels of catalase from a variety of sources.
 
AIM: To test for the relative amounts of Catalase enzyme in a variety of organic sources

Does anyone know what the dependent variable will be in this experiment?

Rate of reaction of the enzyme catalase
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RazzMeTazz

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Re: VCE Biology Question Thread
« Reply #1002 on: March 08, 2014, 06:17:54 pm »
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Hi I just wanted to explain what happens in the light dependent aof photosynthesis, so that someone could correct me if I'm wrong and tell me if my explanation needs to be changed :)

Light dependent reactions:
Photons from the sun are absorbed by chlorophyll molecules in Photosystem 2 and this excites the electrons of the chlorophyll molecules, thus they move to excited states. These electrons then travel through the electron transport chain, releasing their energy in a series of stops, through a range of molecules. The chlorophyll molecules of photosystem 2 however, now have a lack of electrons and so they split water into oxygen, electrons and protons (H+). This oxygen gas is released as a by product and Photosystem 2 takes these electrons, so that it has electrons once again. The energy released by the electrons travelling in the electron transport chain is then used to pump the protons (H+) produced through the photolysis of water, into the thylakoid lumen. This creates a concentration gradient of charge, and the positive charge is greater in the interior of the thylakoid lumen. Therefore the hydrogen ions move through ATP synthase in order to return to regions of low concentration, and the movement of the hydrogen ions through ATP synthase, provides energy for the phosphorylation of ADP to form ATP.

The spent electrons at the end of the electron transport chain get accepted by the carrier molecule NADP+ and so do the hydrogen ions that moved through ATP synthase. Thus NADP+ forms into NADPH.

The energy contained within the NADPH and ATP molecules produced in the light dependent reactions are then used in the Calvin cycle.

Is this correct? Thanks  :)

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Re: VCE Biology Question Thread
« Reply #1003 on: March 09, 2014, 12:45:11 am »
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is osmosis the net movement of water molecules from a region of high to low water concentration or low to high?
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Re: VCE Biology Question Thread
« Reply #1004 on: March 09, 2014, 12:46:53 am »
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 After my first 3/4 bio sac- I seem to still always make simple mistakes/ errors which cost me a couple of marks which I shouldn't have lost. Do you people have any tips in how I could reduce it, and hopefully until I make no mistakes in my sacs, so I can start getting 100%