VCE Biology Question Thread

[Mr West]

Thankyou^

just another question, do plants undergo alcoholic fermentation just as yeast do?

cheers

[DBA-144]

Yeah I am quite sure that plants undergo alcoholic fermentation. However, if this continues for a extended period of time, then the plant can actually die. This is because alcohol is toxic to plants, and they must remove alcohol from their cells. This is why we use yeast for brewing alcohol and not plants! Also, by using yeast for cakes, the co2 can give the bubbles that make them rise!

[vox nihili]

Yeah I am quite sure that plants undergo alcoholic fermentation. However, if this continues for a extended period of time, then the plant can actually die. This is because alcohol is toxic to plants, and they must remove alcohol from their cells. This is why we use yeast for brewing alcohol and not plants! Also, by using yeast for cakes, the co2 can give the bubbles that make them rise!

Yeasts also die at certain levels of alcohol. That's why you can only get to a certain level of alcohol in alcoholic beverages before they need to be distilled

While I'm not sure 100% if or not water is produced in glycolysis maybe in one of the 10 steps, however, I know that for a VCE standard, we don't need to say that water is an output of glycolysis. The only outputs we really need to know are the pyruvates, NADH and ATP

Second this. Water as an output doesn't really matter because the reactions happen in a watery environment.

[PopcornTime]

Is the inhibition non-competitive or competitive: experimental design.
IV: Increasing concentrations of substrate (%)
DV: amount/volume of product produced
CV: all other factors, including:
- same volume and concentration of enzyme
- same volume of substrate
- same volume concentration of inhibitor
- temperature (ºC): 30ºC incubated

Set up 2 groups:
- control group: 5 test tubes set up, each with an increasing concentration of substrate and same enzyme concentration in each tube
- treatment group: 5 test tubes set up: each with an increasing concentration of substrate and same enzyme concentration in each tube, as well as same concentration of inhibitor

Expected results:
- if the volume of product produced increases as substrate concentration increases, then the inhibitor is competitive, as competitive inhibition is reduced by increasing substrate concentration
- if volume of product produced is less than saturation point of control group, then inhibitor is competitive

[Mr West]

sorry with the spam of questions

this ones regarding glycolysis

so 1 glucose molecule goes in (has 12 hydrogens) and 2 pyruvates come out (each has 3 hydrogens, so 3x2=6 hydrogens in total)

correct me if I'm wrong, but then 4 hydrogens are used to convert NAD+ into NADH (2 hydrogens for each), as each NAD+ molecules requires one hydrogen and two electrons to form NADH (therefore two hydrogens used up for each)

so 6+4=10 hydrogens used up so far, but since glucose had 12 hydrogens, where does the remaining two go?

I asked previously whether water was an output, and this would explain the remaining two leaving, but then where does the oxygen come from as the two pyruvate molecules use all of the glucose molecule's water.

plz help 

[PopcornTime]

An experiment investigating pH and enzyme activity has a control group with a test tube at each pH but does not contain any enzyme. Why? What does this show?

[PhoenixxFire]

Is the inhibition non-competitive or competitive: experimental design.
IV: Increasing concentrations of substrate (%)
DV: amount/volume of product produced
CV: all other factors, including:
- same volume and concentration of enzyme
- same volume of substrate
- same volume concentration of inhibitor
- temperature (ºC): 30ºC incubated

Set up 2 groups:
- control group: 5 test tubes set up, each with an increasing concentration of substrate and same enzyme concentration in each tube
- treatment group: 5 test tubes set up: each with an increasing concentration of substrate and same enzyme concentration in each tube, as well as same concentration of inhibitor

Expected results:
- if the volume of product produced increases as substrate concentration increases, then the inhibitor is competitive, as competitive inhibition is reduced by increasing substrate concentration
- if volume of product produced is less than saturation point of control group, then inhibitor is competitive

What's the question? If you just wanted it checked then it looks good to me.

sorry with the spam of questions

this ones regarding glycolysis

so 1 glucose molecule goes in (has 12 hydrogens) and 2 pyruvates come out (each has 3 hydrogens, so 3x2=6 hydrogens in total)

correct me if I'm wrong, but then 4 hydrogens are used to convert NAD+ into NADH (2 hydrogens for each), as each NAD+ molecules requires one hydrogen and two electrons to form NADH (therefore two hydrogens used up for each)

so 6+4=10 hydrogens used up so far, but since glucose had 12 hydrogens, where does the remaining two go?

I asked previously whether water was an output, and this would explain the remaining two leaving, but then where does the oxygen come from as the two pyruvate molecules use all of the glucose molecule's water.

plz help 

Sorry I don't know, but you definitely don't need to know for VCE. If I had to guess maybe there's just a random oxygen molecule in the cell that we don't include in the reaction. This is way beyond my chemistry knowledge but it may make sense to you.

An experiment investigating pH and enzyme activity has a control group with a test tube at each pH but does not contain any enzyme. Why? What does this show?

In this experiment your IV is Enzyme activity at different pH levels, not the effect of the pH level itself. This shows that the results are caused by the enzyme not by any other variable.

[vox nihili]

sorry with the spam of questions

this ones regarding glycolysis

so 1 glucose molecule goes in (has 12 hydrogens) and 2 pyruvates come out (each has 3 hydrogens, so 3x2=6 hydrogens in total)

correct me if I'm wrong, but then 4 hydrogens are used to convert NAD+ into NADH (2 hydrogens for each), as each NAD+ molecules requires one hydrogen and two electrons to form NADH (therefore two hydrogens used up for each)

so 6+4=10 hydrogens used up so far, but since glucose had 12 hydrogens, where does the remaining two go?

I asked previously whether water was an output, and this would explain the remaining two leaving, but then where does the oxygen come from as the two pyruvate molecules use all of the glucose molecule's water.

plz help 

It's a good question this one, although PF is absolutely right that it's well beyond the course. Your logic is a little bit flawed, insofar as you claim that NADH requires 2 hydrogens to go from NAD+ to NADH. It only requires one.

Let's count our 12:

In glycolysis two come out as 2NADH (total 2).

In Krebs, we get an additional 6NADH for six more hydrogens (total . You may have learned that we get 8NADH, but this is done for simplicity's sake. There's actually another molecule in Krebs that collects hydrogens, called FAD. It becomes FADH2; therefore, requiring two hydrogens per molecule. We get two of these out of Krebs for four hydrogens...therefore 8+4=12.

[randomnobody69420]

Is more carbon dioxide absorbed in photosynthesis than is released in cellular respiration? And if so, why?

[PhoenixxFire]

Is more carbon dioxide absorbed in photosynthesis than is released in cellular respiration? And if so, why?

Both are 6 carbon dioxide.

[darkz]

Is more carbon dioxide absorbed in photosynthesis than is released in cellular respiration? And if so, why?

Well this would ultimately depend on the rate of photosynthesis vs rate of respiration, so at times, it can indeed be a greater intake of CO2, while at other times there is an equal uptake or lower uptake. There would be a greater intake when the rate of photosynthesis exceeds the rate of respiration. There would be an equal uptake when the rate of photosynthesis equals the rate of respiration - this is also known as the compensation point. And when the rate of respiration exceeds the rate of photosynthesis, then there would be a lower uptake. The lower uptake may be due to other limiting factors e.g. light intensity etc affecting the rate of photosynthesis

[peachxmh]

What is the difference between the axon terminal and the synaptic terminal, or are they the same? Google seems to provide me with conflicting answers, some label the rounded end of the neuron (the synaptic knob) as the synaptic terminal, while others label it as axon terminal. Other diagrams label the branches leading to the synaptic knob as the axon terminal.

Also, where are neurotransmitters produced and where are they stored?

P.S. Examples of mentioned conflicting diagrams have been attached to this post As usual, thank you heaps in advance, much appreciated!

Soz for edit, wanted to add something else. If we were asked to draw a diagram of the reflex arc would that be this?: stimulus -> receptor -> control centre (CNS) -> effector -> response

[darkz]

What is the difference between the axon terminal and the synaptic terminal, or are they the same? Google seems to provide me with conflicting answers, some label the rounded end of the neuron (the synaptic knob) as the synaptic terminal, while others label it as axon terminal. Other diagrams label the branches leading to the synaptic knob as the axon terminal.

Also, where are neurotransmitters produced and where are they stored?

P.S. Examples of mentioned conflicting diagrams have been attached to this post As usual, thank you heaps in advance, much appreciated!

Soz for edit, wanted to add something else. If we were asked to draw a diagram of the reflex arc would that be this?: stimulus -> receptor -> control centre (CNS) -> effector -> response

Well from what we've been told in class, the synaptic knob = axon terminal = synaptic terminal so I don't think that there are any significant differences between them. As for the location of the neurotransmitters, you can just say that they are produced and found in the axon terminal.

As for the reflex arc, I'm not too sure about it, is it still in the study design? Because our teacher didn't really mention it

[PhoenixxFire]

As for the reflex arc, I'm not too sure about it, is it still in the study design? Because our teacher didn't really mention it

Definitely not in the study design.

There may be a difference between synaptic terminal and axon terminal (I don’t know) but even if there is just call it the axon terminal for biology.

[Mr West]

in my textbook certain words are used interchangeably:

- "lactate" and "lactic Acid"
- "Pyruvate" and "Pyruvic Acid"

my teacher says that lactate and lactic acid is the same thing, as with pyruvate and pyruvic acid.

is this true?

I'm asking this because during anaerobic respiration in mammals, the textbook says the output is lactate

cheers