Cell Respiration (//unit 2)

Question 0

The link reaction

Answer 0

Pyruvate** is converted into **acetyl coenzyme A.

The first step, occurs after the pyruvate, which has been produced in the cytoplasm, is shuttled into the mitochondrial matrix. Once there, the pyruvate is decarboxylated and oxidized to form an acetyl group. Two high energy electrons are removed from pyruvate. These react with NAD2 to produce reduced NAD.

This is called the link reaction, because it links glycolysis with the cycle of reactions that follow.

Question 1

Phosphorylation

Answer 1

For many reactions, the purpose of phosphorylation is to make the phosphorylated molecule more unstable; i.e., more likely to react. Phosphorylation can be said to activate the molecule.

Question 2

What is Chemiosmosis

Answer 2

In Chemiosmosis protons defuse through ATP synthase to generate ATP.

Question 3

The role of oxygen in chemiosmosis

Answer 3

Oxygen is needed to bind with the free protons to form water to maintain the hydrogen gradient (final electron acceptor) between the intermembrane space and the mitochondrial matrix.

Question 4

cell respiration

Answer 4

Energy must be continues in organisms to main vital process like active transport and protgein synthesis. Most need ATP.

Cell respiration = controlled release of energy from organic compounds to produce ATP

Carbon compounds (aka. organic compounds) such as glucose or fat are broken down to release energy.

Question 5

benefits of ATP

Answer 5

• immediately avaible as an energy source in the cell
• can diffuse to any part of the cell

Question 6

comparing aerobic and anaerobic cell respiration

Answer 6

Question 7

Which kind of cell respiration is used in vigorious exercise and why?

Answer 7

Although anaerobic cell respiration produces fwer molecules of ATP per glucose, it can supply ATP at a more rapid overall rate for a short time, because it is not limited by how fast oxygen can be supplied.

Anaerobic cell respiration is therefore used in muscles carrying out vigorous exercise, such as sprinting or weight lifting. Anaerobic cell respiration maximises the power of muscle contractions.

Lactate (lactic acid) and hydrogen ions are produced by this process and therefore only be used for about two minutes, beyond which the blood concentration of ions would make the pH of blood too low.

Question 8

using yeast in brewing and baking

Answer 8

Both products of anearobic respiration in yeast are used in industries.

Carbon dioxide and the baking industry

Yeast is mixed into the dough before baking. The yeast rapidly uses up all oxygen present in the dough and then produces ethanol and carbon dioxide by anearobic cell respiration. The carbon dioxide forms bubbles making the dough rise - it increases in volume. This makes the dough less dense - it is leavended. When the dough is baked, most of the ethanol evaporates and the carbon dioxide bubbles give the bread a light texture, which makes it more appetizing.

Ethanol and the brewing and biofuel industries

Yeast is cultured in a liquid containing sugar and other nutrients, but not oxygen so it respries anaerobically. The ethanol concentration of the fluid around the yeast cells can rise to approximately 15% by volume, before it becomes toxic to the yeast and the fermentation ends. Most of the carbon dioxide bubbles out into the atmosphere. Beer, wine and other alcoholic drinks are brewed this way. Ethanol is also produced by fermentation for use as a fuel.

Question 9

respirometers and respiration rates

Answer 9

One possible design of measuring respiration rates is:

1. A sealed glass or plastic container in which the organism or tissue is placed.
2. An alkali, such as potassium hydroxide, which absorbs carbon dioxide produced by cell respiration. The volume of air inside the respirometer should therefore reduce as a result of oxygen being used.
3. A capillary tube containing fluid, connected to the container, which allows the volume of air inside the respirometer to be monitored.

Question 10

ethical implications of using the respirometer

Answer 10

Fly larvae or other ivertebrates are sometimes placed in respirometers.

1. Will the animal suffer pain or harm?
2. Are there unacceptable risks?
3. Can the organism successfully return to its natural habitat?
4. Can better alternatives be used?

Question 11

Plotting graphs: axis, range- and error bars

Answer 11

A graph should be plotted of the mean results, with the independent variable on the x-axis and the dependent variable on the y-axis.

The lines extending from the mean show the range from the lowest to the highest results - range bars.

Error bars show one standard deviation above and below the mean.