VCE Biology Question Thread

[nerdmmb]

URGENT!!
Can someone please help me:
In an enzyme sac where the effect of hydrogen peroxide is observed on sand, liver and liver & sand, is the dependent variable the temperature change and rate of reaction?
Is the controlled variable the amount of hydrogen peroxide which is constant in all of the test tubes?

If so, then is the independent variable the substances (1. sand, 2. Liver, 3. Sand and Liver) that the hydrogen peroxide acts on?

What is the function of catalase? And would it be correct to say that catalase acts on hydrogen peroxide therefore bubbles are formed and there is an increase in temperature?

Also wondering, for the question 'what two factors affect the active site of an enzyme', can I say any of the following factors?
-Temperature
-pH
-Chemical inhibitors?

Thank-you so much.

[FarAwaySS2]

URGENT!!
Can someone please help me:
In an enzyme sac where the effect of hydrogen peroxide is observed on sand, liver and liver & sand, is the dependent variable the temperature change and rate of reaction?
Is the controlled variable the amount of hydrogen peroxide which is constant in all of the test tubes?

If so, then is the independent variable the substances (1. sand, 2. Liver, 3. Sand and Liver) that the hydrogen peroxide acts on?

What is the function of catalase? And would it be correct to say that catalase acts on hydrogen peroxide therefore bubbles are formed and there is an increase in temperature?

Also wondering, for the question 'what two factors affect the active site of an enzyme', can I say any of the following factors?
-Temperature
-pH
-Chemical inhibitors?

Thank-you so much.

You seem right about the variables. The function of catalase in the human body is simple to perform the decomposition of the highly corrosive/dangerous hydrogen peroxide into gaseous oxygen and water molecules that can actually be usable for cells. I'm not sure about that question though.
Yup those three are fine.

[nerdmmb]

Thanks FarAwaySS2

Also, what are the types of errors in an experiment?

Is it just technical and human errors?

[FarAwaySS2]

Yeah, simple human errors e.g. Reading errors, timing error, etc.

[vox nihili]

Thanks FarAwaySS2

Also, what are the types of errors in an experiment?

Is it just technical and human errors?

Contamination, natural variation in biological material etc etc

[nerdmmb]

Why does liver have more catalase?

How does pH affect enzyme activity?

In the liver/hydrogen peroxide experiment, can there be two dependent variables --> Temperature change and rate of reaction?

Thanks!

[vox nihili]

Why does liver have more catalase?

How does pH affect enzyme activity?

In the liver/hydrogen peroxide experiment, can there be two dependent variables --> Temperature change and rate of reaction?

Thanks!

The liver detoxifies the blood, hydrogen peroxide is a toxin.

[katiesaliba]

How can glycolysis be said to occur in the cytoplasm if the cytoplasm includes all organelles inside the cellular membrane (excluding the nucleus)? Doesn't it occur in the cytosol?

[grannysmith]

How can glycolysis be said to occur in the cytoplasm if the cytoplasm includes all organelles inside the cellular membrane (excluding the nucleus)? Doesn't it occur in the cytosol?

It's still essentially in the cytoplasm even though it really occurs in the cytosol; does not occur within organelles but amidst them in the cytosol if that makes sense

[vox nihili]

How can glycolysis be said to occur in the cytoplasm if the cytoplasm includes all organelles inside the cellular membrane (excluding the nucleus)? Doesn't it occur in the cytosol?

You do make a true point, though if it occurred in any one of those organelles you'd assume that that would be explicitly said.

It definitely can't occur in the cytosol. Nothing is really in the cyotosol at all, it's just a liquid, it describes all of the liquid contents. So any process that occurs "in" the cytosol is actually part of the cytosol.

[katiesaliba]

Thanks everyone!

Also, is my understanding of light dependent photosynthesis correct:

When photons hit photosystem II and I, their electrons become excited. This excitement 'reaches' the chlorophyll inside the photosystems which excites a chlorophyll electron. The excited chlorophyll electron is lost to an electron acceptor in the ETC, leaving the photosystems with a positive charge. The electrons lost from photosystem I combine with H+ from the stroma to form NADPH. Acting as a means of replenishment, the electrons lost from photosystem II move along the ETC to photosystem I. As they do this, H+ ions move against their concentration gradients into the lumen of the thylakoid. The electrons provide the energy for this to occur, as it is an active form of transport. H2O is split to form H+, O2 and e- (electrons). The electrons (e-) from the catabolism of water are used to replenish those that were lost from photosystem II. Oxygen is released from the exergonic reaction as a by-product. The H+ ions (or protons) released add to the H+ concentration forming in the lumen. These H+ then travel through ATP synthase, creating a concentration gradient which releases energy. I'm pretty sure that free electrons are also used in this process. ATP is formed as a result of this process.

[grannysmith]

Thanks everyone!

Also, is my understanding of light dependent photosynthesis correct:

When photons hit photosystem II and I, their electrons become excited. This excitement 'reaches' the chlorophyll inside the photosystems which excites a chlorophyll electron. The excited chlorophyll electron is lost to an electron acceptor in the ETC, leaving the photosystems with a positive charge. The electrons lost from photosystem I combine with H+ from the stroma to form NADPH. Acting as a means of replenishment, the electrons lost from photosystem II move along the ETC to photosystem I. As they do this, H+ ions move against their concentration gradients into the lumen of the thylakoid. The electrons provide the energy for this to occur, as it is an active form of transport. H2O is split to form H+, O2 and e- (electrons). The electrons (e-) from the catabolism of water are used to replenish those that were lost from photosystem II. Oxygen is released from the exergonic reaction as a by-product. The H+ ions (or protons) released add to the H+ concentration forming in the lumen. These H+ then travel through ATP synthase, creating a concentration gradient which releases energy. I'm pretty sure that free electrons are also used in this process. ATP is formed as a result of this process.

Haha, that's very detailed and I think a little extraneous for the purpose of VCE Biology. That being said, Khan Academy IS awesome

[grannysmith]

You do make a true point, though if it occurred in any one of those organelles you'd assume that that would be explicitly said.

It definitely can't occur in the cytosol. Nothing is really in the cyotosol at all, it's just a liquid, it describes all of the liquid contents. So any process that occurs "in" the cytosol is actually part of the cytosol.

I had always thought it occurred in the cytosol :/

[rhinwarr]

What happens to enzymes at very cold temperatures? I know their ability to catalyse reactions is reduced but is it because they do not have enough energy to faciliate the reactions or because their shape is changed temporarily (or neither)?

[Seige]

What happens to enzymes at very cold temperatures? I know their ability to catalyse reactions is reduced but is it because they do not have enough energy to faciliate the reactions or because their shape is changed temporarily (or neither)?

Its because at low temperatures the kinetic energy is greatly decreased so therefore reactions will occur really slowly.