VCE Biology Question Thread

[cosine]

What could be some photosynthesis topic-pracs? Would it be over a period of time as photosynthesis is a relatively slow process? Anyone already done it and can give me insight, thanks

[sunshine98]

Hey guys two questions. 
1. What is the relation of light intensity to carbon use during photosynthesis? Would that be carbon use would rise as light intensity gets stronger?
2. What is the interrelationship between photosynthesis and respiration?

1. We know that as light intensity increases, the rate of photosynthesis also increases. Photosynthesis requires Carbon dioxide, so  yes as light intensity increases the amount of carbon needed would increase
2. Photosynthesis and Cellular Respiration are essentially said to be opposites. Photosynthesis is  , basically the making of glucose (anabolic) whilst , respiration is the breaking of glucose to release energy (catabolic). Photosynthesis requires energy (endergonic), cellular respiration releases energy(exergonic).
Photosynthesis requires carbon dioxide , respiration releases Carbon dioxide(my teacher said this is important relationship , apparently some exam q had something like this)
hope this helped 

[Jay.C]

Hey guys!

I've just had the practical part of my photosynthesis sac. The sac was we had to extract O2 from leaves so they would sink when put into a bicarbonate solution. Then we put one solution in the dark and one in the light and observed if any leaves floated. If the leaves floated this was an indication that photosynthesis had occurred due to CO2 being taken up? Has any one done this sac and if so could they give me an idea of the questions I am likely to receive, even if you haven't I would really appreciate some questions you think I could get. Thanks!

[StupidProdigy]

Where is the site of anaerobic respiration? I realize that the mitochondria is the site of aerobic but I'm not sure if it is the site for both? Thankyouthankyou
Also how is chlorophyll a related to photo-systems one and two?

[grannysmith]

Where is the site of anaerobic respiration? I realize that the mitochondria is the site of aerobic but I'm not sure if it is the site for both? Thankyouthankyou
Also how is chlorophyll a related to photo-systems one and two?

Mitochondria is the site of aerobic respiration. Anaerobic respiration, which includes glycolysis, occurs in the cytoplasm/cytosol.

[wobblywobbly]

Also how is chlorophyll a related to photo-systems one and two?

It's not necessary (i.e. not part of the study design) to know what happens in the photosystems, but just that chlorophyll is the main site of light absorption.

(If you are really hungry for more details, I suggest you check out Bioninja/Crash Course for more details about what actually happens but I reiterate that you only need to know inputs/outputs/location of each stage of photosynthesis, and don't need to know all the details)

[StupidProdigy]

Mitochondria is the site of aerobic respiration. Anaerobic respiration, which includes glycolysis, occurs in the cytoplasm/cytosol.

It's not necessary (i.e. not part of the study design) to know what happens in the photosystems, but just that chlorophyll is the main site of light absorption.

(If you are really hungry for more details, I suggest you check out Bioninja/Crash Course for more details about what actually happens but I reiterate that you only need to know inputs/outputs/location of each stage of photosynthesis, and don't need to know all the details)

Thankyou both for the help, really appreciate it! That bioninja site looks interesting, I'm basically trying to self-teach at the moment so that's really helpful having another good resource, already loving Bozeman and crash course. Thanks again guys

[paper-back]

Do all plants aerobically respire?

[grannysmith]

Do all plants aerobically respire?

Yes. There may be exceptions that I don't know of but essentially, the answer is yes. Plants cannot anaerobically respire indefinitely as it produces ethanol as a by-product, which is toxic to plant cells at high concentrations. Hence, plants need to be able to aerobically respire, as plants require energy to survive.

[vanessa14]

On monday I had my sac on enzymes, and was wondering if anyone has done it and what type of questions do I prepare myself for?  I don't particularly understand why liver was used? We cooked one to test the rate of reactions? But we also recorded the different colours we saw after we mixed amylase with iodine, at different temperatures?
Can someone kindly give me a run down of the things I should study, and the things I should know?  thank you for anyones help!

[Jay.C]

Why are carbohydrates so good in terms of providing energy?

[cosine]

On monday I had my sac on enzymes, and was wondering if anyone has done it and what type of questions do I prepare myself for?  I don't particularly understand why liver was used? We cooked one to test the rate of reactions? But we also recorded the different colours we saw after we mixed amylase with iodine, at different temperatures?
Can someone kindly give me a run down of the things I should study, and the things I should know?  thank you for anyones help!

I am not so sure about the liver. But the temperature one and amylase was identical to mine.

We had to test 4 tests in differing temperatures where we observed the performance of amylase under those conditions. Basically, if there was no starch digestion (break down), it meant the the amylase had completely denatured when it was exposed to the extreme temperature. The other one was freezing temp, where the digestion of starch was there, but it was at a slow rate, meaning that the enzyme was exposed to low temperatures but was still able to function. The final test was at normal room temperature. The enzyme worked at it's optimal, as the starch was digested relatively faster.

Some questions on the SAC included:
1. Enzymes are biological catalysts, explain
2. What is the independent variable of the experiment?
3. What is the dependent variable of the experiment?
4. Explain the experimental results and what is the enzyme's optimum temperature?
5. What was expected (in terms of enzymatic activity) when amylase was placed in : 0-10C, 20-30C and 80-100C?

[KingDrogba]

Hey Biolads,

Few Questions in regards to photosynthesis:

1. Why in the presence of white light is the rate of photosynthesis the greatest?
2. What is the role of NADPH in the process of photosynthesis?
3. When using leaf discs to measure photosynthetic rate (Practical activity) half of the leaves were infiltrated with water through a vacuum process, after all gases were sucked out and replaced with liquid they sunk. We then placed these in a beaker of water and placed a light source over it so they would photosynthesis. However, in 15 minutes none of the leaf discs floated up (a sign of photosynthesis), can anyone explain to me why this occurred?

All hail drogba

[wobblywobbly]

Hey Biolads,

Few Questions in regards to photosynthesis:

1. Why in the presence of white light is the rate of photosynthesis the greatest?
2. What is the role of NADPH in the process of photosynthesis?
3. When using leaf discs to measure photosynthetic rate (Practical activity) half of the leaves were infiltrated with water through a vacuum process, after all gases were sucked out and replaced with liquid they sunk. We then placed these in a beaker of water and placed a light source over it so they would photosynthesis. However, in 15 minutes none of the leaf discs floated up (a sign of photosynthesis), can anyone explain to me why this occurred?

All hail drogba

1. White light consists of the whole spectrum of light, meaning that chlorophyll is able to absorb more light, especially at the wavelengths that it particularly absorbs.

2. Carries hydrogen ions from the light dependent reactions to light independent reactions

3. (A guess) Was carbon dioxide sucked up? Maybe the plant was incapable of absorbing the CO2 from the water, or not enough time elapsed for it (the plant to absorb carbon dioxide from the water) to start photosynthesis again (As CO2 is an input of photosynthesis).

[mahler004]

2. Carries hydrogen ions from the light dependent reactions to light independent reactions

Actually electrons.