VCE Biology Question Thread

[Sup]

Could someone please give me a detailed explanation on what happens in the light dependent stage in photosynthesis?

Especially how NADP+ becomes NADPH.

Thanks a lot.

[nhmn0301]

Could someone please give me a detailed explanation on what happens in the light dependent stage in photosynthesis?

Especially how NADP+ becomes NADPH.

Thanks a lot.

at light dependent stage, sunlight will emit photon, electrons in chlorophyll will absorb these energy and become excited. What happens next is these electrons undergo an Electron transport chain which occurs on the membrane of the grana . Protein channels will absorb some energy from these electrons and use this energy to actively pump the H+ ions into the outer membrane space.Until there is a high concentration of H+ ion in the outer membrane space, these H+ ions will rush back into the ATP synthase, which is an enzyme that is responsible for the production of ATP. NADP+ is an electron carrier that are able to shuttle the electrons from the grana into the stroma for the production of glucose during Calvin cycle. Hence, when NADP+ carries the electrons, it will become NADPH.

[RazzMeTazz]

What is a 'controlled' experiment?

How would you define a non-biological catalyst?

[RazzMeTazz]

Students wished to investigate the effect of temperature on the enzyme catalase (from humans), which breaks down hydrogen peroxide into water and oxygen gas. A measuring cylinder containing water was connected to the test tubes and the volume of oxygen produced was determined by observing the volume of water that was displaced.

They designed their experiment as follows:
- 11 test tubes were set up at room temperature each containing 5ml of peroxide solution
- The test tubes were labelled from 0degrees, to 100degrees  in 10degree increments (all measurements in Celsius)
- Temperature in each test tube was monitored via a satalogger
- The solutions in the test tubes were then treated in the following manner.
- Each of the test tubes then had 2ml of catalase solution added to them and the volume of oxygen produced was recorded.


Q1.) Their teacher commented that, while their experiment was well constructed, there needed to be some fine-tuning before the experiment would be more scientifically sound.
Identify one possible change that needs to occur:





What would this change be?

[eagles]

The students can possibly indicate a control group.

In that, they use a test tube filled with 5mL of distilled water, and treated to the same conditions.

Then, such a control can act as a mode of comparison and verification for the action of catalase on the hydrogen peroxide.

[alchemy]

How would you define a non-biological catalyst?

Something, such as a chemical agent, that catalyses reactions outside of the body.

[RazzMeTazz]

Are all enzymes biological (only occur in living things?)

Is catalase a quaternary protein?

[RazzMeTazz]

Something, such as a chemical agent, that catalyses reactions outside of the body.

Thanks

[RazzMeTazz]

The students can possibly indicate a control group.

In that, they use a test tube filled with 5mL of distilled water, and treated to the same conditions.

Then, such a control can act as a mode of comparison and verification for the action of catalase on the hydrogen peroxide.

Thanks!

[alchemy]

Are all enzymes biological (only occur in living things?)
Is catalase a quaternary protein?

There

All enzymes are biological catalysts.
Catalase does have a quatenary structure but you probably won't need to know this specifically.

[slothpomba]

Are all enzymes biological (only occur in living things?)

Is catalase a quaternary protein?

Enzymes only naturally occured or are naturally produced by biological things. A rock for instance doesn't make its own enzymes, a tub of water doesn't make its own enzymes. A tree does, a moth does. An enzyme is really a subclass of catalysts. You can have many kinds of catalysts, enzymes are one kind of catalyst that are specific to living things. Platinum is used as a catalyst in car exhausts for instance, it's just a raw metal, it's not a protein or anything but it does act as a catalyst, speeding the reaction.

[vox nihili]

Are all enzymes biological (only occur in living things?)

Is catalase a quaternary protein?

An enzyme, by definition, is a biological catalyst.

[Tyleralp1]

Few quick questions:

1. Is this right..Anaerobic respiration involves glycolysis and fermentation, producing 2ATP molecules.

2. How do prokaryotes respire? Since they dont contain mitochondria, is it only anaerobically, and thus a net output of 2 ATP molecules? I'm confused as I read in Neap that they produce 38 (2 more than normal) as they dont need to use 2ATP going to mitochondria.

[Scooby]

Few quick questions:

1. Is this right..Anaerobic respiration involves glycolysis and fermentation, producing 2ATP molecules.

2. How do prokaryotes respire? Since they dont contain mitochondria, is it only anaerobically, and thus a net output of 2 ATP molecules? I'm confused as I read in Neap that they produce 38 (2 more than normal) as they dont need to use 2ATP going to mitochondria.

1. If we're being technical, anaerobic respiration is just respiration without using oxygen as an electron acceptor. All the stages of aerobic respiration still occur but instead of oxygen, something else (eg. sulfate or nitrate) acts as the final electron acceptor in the electron transport chain stage. Anaerobic respiration doesn't occur in humans - it's pretty much exclusive to prokaryotes that live in very oxygen-poor environments. Humans use lactic acid fermentation (which is just glycolysis, then after that pyruvate is converted to lactate). Some bacteria and yeast species use ethanol fermentation (whereby pyruvate is converted to ethanol and carbon dioxide). This isn't anaerobic respiration - it's fermentation.

2. Prokaryotes can respire aerobically or anaerobically, depending on the environment that they usually live in. Some can do both (these organisms are called facultative anaerobes); others are exclusively aerobic (obligate aerobes) or anaerobic (obligate anaerobes). Instead of using the mitochondrial membranes to generate a proton gradient (which is what happens during the electron transport chain stage of aerobic respiration in humans), prokaryotes use their cell membrane (ie. a difference in H+ concentration is established between the interior and exterior of the cell). Don't bother trying to figure out how many ATP molecules are produced per glucose molecule for prokaryotic aerobic respiration - the amount described varies depending on what you're reading (there's some debate about how many ATP molecules it takes to transport pyruvate into the mitochondria in eukaryotic aerobic respiration). Just stick with the usual 36 ATP molecules per glucose molecule (not that they'll ask you about prokaryotic respiration anyway).

Hope that helps

[tanaconda]

hi, just a quick question... or two
I did a biology sac today on photosynthesis and respiration
for part A we had to pour pond water in 4 tests tubes and two containing elodea
which then we had to add drops of phenol red indicator
then bubble CO2 gas through the solution which changed the colour to more of a yellow
we then had to add ammonia and leave 2 test tubes in light, two in dark.
questions I have are:
Complete the following table
Indictor colour                               PINK                     Yellow
Name of process                              ?                             ?
what is the purpose of the tubes with no elodea?
and predict what would happen if you moved the tube in the dark containing elodea into light for two days?
it would be wonderful if anyone could help clarify these questions