VCE Biology Question Thread

[rhinwarr]

Yes, but the electrons it gives off are at a lower energy level so contribute to less ATP production

[nerdmmb]

What role do cytochrome molecules play in aerobic respiration and in the ETC?

Thanks!

[RazzMeTazz]

Why are enzymes so important in biochemical pathways?

Why are cofactors important in biochemical pathways?

What is an allosteric site?

[katiesaliba]

Isn't water technically an input and output of the Kreb's cycle?

[RazzMeTazz]

Is the optimum range of an enzyme the range within which it can function in, or the range within it functions best in?

[RazzMeTazz]

What does the addition of
a.)lead, mercury, cadimum,
b.)H+ ions,
c. OH- ions

do for an enzyme mediated reaction, in terms of product formation?

[nerdmmb]

Is the optimum range of an enzyme the range within which it can function in, or the range within it functions best in?

Enzymes can function at any range up to the critical temperature range whereby enzymes begin to denature.

The optimum range is the range at which an enzyme works best.

[Scooby]

Isn't water technically an input and output of the Kreb's cycle?

Yes, but don't ever write that on a VCE exam. For VCE Bio, water is only an output of the electron transport chain

[nerdmmb]

What does the addition of
a.)lead, mercury, cadimum,
b.)H+ ions,
c. OH- ions

do for an enzyme mediated reaction, in terms of product formation?

Lead mercury and cadmium are simply cofactors if I'm not wrong - they aid the enzyme's function
H+ ions increase the acidity of the solution in which the enzyme is in - this reduces the pH and can alter the optimum pH of an enzyme so rate of reaction may decrease/increase
OH- ions increase alkalinity which also affects the pH of the solution in which the enzyme is in and therefore alter the rate of reaction by reducing/increasing it.

[Scooby]

What does the addition of
a.)lead, mercury, cadimum,
b.)H+ ions,
c. OH- ions

do for an enzyme mediated reaction, in terms of product formation?

Well there isn't really enough information to answer the question, but I'll just assume before any of those things were added that the enzyme was functioning in its optimum environment

Adding lead, mercury or cadmium will all most likely denature the enzyme molecules (they're all heavy metals, which are known to denature enzymes). That'll reduce the rate at which this enzyme-catalysed reaction is occurring and therefore the rate of product formation will also decrease

Adding H+ or OH- will change the pH of the solution. Assuming the pH is at the optimum, making it more acidic or more basic will  result in enzyme denaturation (with the extent of denaturation dependent on how far away from the optimum the pH gets) and the rate of product formation will decrease

[nerdmmb]

How does light intensity, chlorophyll concentration and oxygen concentration affect photosynthesis?

[Scooby]

How does light intensity, chlorophyll concentration and oxygen concentration affect photosynthesis?

Increasing light intensity = more light available to the plant (more electrons in chlorophyll molecules can be excited at any point in time) = greater rate of photosynthesis. Eventually you'll reach a point though were increasing light intensity further has no effect on the rate of photosynthesis (if you've got a graph of the rate of photosynthesis this corresponds to a plateau)

Greater chlorophyll concentration = more chlorophyll molecules available to absorb light at any point in time = greater rate of photosynthesis

Increasing oxygen concentration may increase the rate of photosynthesis slightly, but probably only if the plant was in an environment depleted of carbon dioxide. Increasing O₂ concentration would increase the rate of aerobic respiration in the plant, increasing the rate at which CO₂ is produced by aerobic respiration. If we increase this rate of CO₂ output the plant is more rapidly able to use that CO₂ for photosynthesis (as part of the light-independent stage). Most likely though the plant will have a plentiful supply of CO₂ from the atmosphere, so this increase in CO₂ output from aerobic respiration will have only a negligible effect on the rate of photosynthesis

[lzxnl]

Is the optimum range of an enzyme the range within which it can function in, or the range within it functions best in?

Chemically, low temperatures would imply slowing down of reaction rates so the enzymes may not be as active. Then, changing temperatures has an effect on the acid base equilibria in the aqueous environment which may result in pH changes. For VCE chemistry students, this arises as acidity constants are temperature dependent. However if you cool the enzymes too much, the rearranging of the equilibrium may just be very slow.

How does light intensity, chlorophyll concentration and oxygen concentration affect photosynthesis?

I'm tempted to say that an increase in the concentration of oxygen would increase the rate of the reverse reaction, I.e. respiration and thus reduce the overall rate of photosynthesis. Someone correct me if I'm wrong.

What does the addition of
a.)lead, mercury, cadimum,
b.)H+ ions,
c. OH- ions

do for an enzyme mediated reaction, in terms of product formation?

Metal cations are often used in enzymes as they can form coordinate bonds to particular atoms to stabilise the molecule as a whole and restrain its relative freedom of movement. Chlorophyll is an example. Therefore, heavy metals may also form such bonds to atoms in enzymes and denature them.

Do correct me if I'm wrong; my biology knowledge is limited at best.

[alt-x]

Why are enzymes so important in biochemical pathways?

Why are cofactors important in biochemical pathways?

What is an allosteric site?

Enzymes are required to lower the activation energy of metabolic reactions/processes, hence speeding up the reaction process - without enzymes an organism's metabolism would be too slow.

Cofactors are required for some metabolic reactions as the enzyme alone will not catalyse the reaction. In many cases the addition of a cofactor forms the shape of the active site for substrates to bind to.

An allosteric site is a site on an enzyme other than it's active site. In some cases the binding to an allosteric site can activate the enzyme while in other scenarios the function can be inhibited.

[alt-x]

Are activation of DNA and increase in cell permeability two examples of responses a cell may have to a hormone signal?