Jennifer Nechamen
2/12/08 Mod 3
IB Biology HL Essay 9
Mitochondria is crucial to multicellular organisms because of its ability to produce energy. Its unique structure allows for this ability, which is known as cellular respiration.
1) Mitochondria are found in all eukaryotic cells, with very few exceptions such as the protist Chaos (Pelomyxa) carolinensis..
2) Mitochondria are commonly concentrated around the base of the flagella.
3) Mitochondria make use of nutrient molecules through oxidative phosphoryation.
4) The fact that mitochondria use oxygen for cellular respiration is the reason that we need oxygen at all.
5) Mitochondria contain a double membrane.
6) The double membrane creates distinct compartments within the mitochondria.
7) The outer membrane is composed of a phospholipids bilayer which allows small molecules to pass through. These molecules include ions, nutrient molecules, ADP, and ATP.
8) The inner membrane allows only oxygen, carbon dioxide, and water to pass through.
9) The composition of the inner membrane is very complex, as it includes the electron transport system, the ATP synthetase complex, and transport proteins.
10) The folds in the inner membrane are organized into lamillae called cristae.
11) The cristae increase the surface area of the inner membrane significantly, making more room for the necessary structures.
12) Two compartments are created by the double membrane. The intermembrane space is the space between the inner and outer membrane.
13) A very important function carried out within the mitochondria is the Citric Acid Cycle, or Krebs Cycle. This is the heart of cellular respiration.
14) The Citric Acid Cycle takes place in the matrix of the mitochondria.
15) Glycolysis precedes the Kreb’s Cycle. It takes place in the cytoplasm.
16) Glycolysis takes glucose, and converts it in a ten-step process into energy.
17) In glycolysis, two ATP are used to create an end product of 4 ATP. Pyruvate is also produced, which is used in the Citric Acid Cycle.
18) Glycolysis is anaerobic, as it does not require oxygen. The Citric Acid Cycle, on the other hand, is aerobic and does require oxygen.
19) Glycolysis is not very efficient. Cells that do not contain mitochondria do not get past this pathway, but the Citric Acid Cycle is very important to cells that do have mitochondria.
20) The Citric Acid Cycle begins with the pyruvate which was the end product of glycolysis. In the Citric Acid Cycle, one ATP is generated from each pyruvate, and there were two pyruvates generated in glycolisis. Thus, one molecule of glucose which goes through each cycle produces a net gain of 4 ATP.
21) Glycolysis produces NADH, and the Citric Acid Cycle does as well but in greater amounts. The NADH is used in the electron transport chain to produce a greater amount of ATP.
22) The electron transport chain is located within the inner membrane. This chain is one of the reasons that the cristae which increase the surface area exist.
23) The electron transport chain takes energy from carriers within the matrix and stores it to a form that can be used to phosphorylate ADP.
24 and 25) Diagram
Extra Fact: During intense exercise, one gets tired because not enough oxygen gets to the cells. The cells do not receive enough oxygen for the Kreb’s Cycle to keep up with the demands. As a result, the cells rely predominantly on glycolysis for energy as it does not require oxygen. This does not produce nearly as much ATP as the Citric Acid Cycle, and we feel fatigued.
In conclusion, it is clear that a complex system exists within the mitochondria that is necessary for cellular respiration. Without mitochondria, a cell relies on glycolysis, which is not always sufficient. The structure of mitochondria, noting the folds in the inner membrane in particular, allow for its complex functions.