Cellular Respiration or

WOW do I Need Energy

ATP

All cells need energy. The most common form of cellular energy is ATP. Below is ATP

It is the negative phosphate groups that give this molecule energy as it becomes unstable. When the phosphate is transferred to other molecules, those molecules have energy because they become unstable.

ATP___> ADP + P is an exergonic reaction that releases energy.

Below is an example of a cell using ATP in the active transport of material across the membrane.

This is the potassium/sodium pump that uses ATP to pump across the ions.

This is a muscle fiber and it shows how ATP is needed to cause the muscle to contract.

A cell must be able to put the phosphate back on the ADP in order to keep living as all cells need energy. This is an endergonic reaction and requires an energy input. The source of energy needed to put the phosphate back on is food such as glucose. Just like a car uses gasoline for energy, cells use glucose as energy source to put the phosphate back on ADP.

Just like the gasoline a car uses for fuel, the energy used by cells, comes from stripping the hydrogens from the glucose molecule. The difference that this must be on in step-wise fashion. This is an oxidizing reaction. Quite often when a molecule has hydrogen, it has increased energy.

The energy produced from the "burning" of glucose is used to make ATP. In chemistry this process is called the oxidation of glucose.

The energy in glucose must be released in steps instead of releasing it all at once. It would be like putting a match in gas can to release it all at once. Cellular respiration has three major parts with many steps in each part.

3 Part of Respiration

I. Glycolysis

II. Kreb's Cycle

III. Electron Transport Chain

Overview of Glycolysis

I. Glycolysis-cytoplasm-

Glucose----> 2 pyruvic acid

2NAD + 2H---->2NADH

2ATP---->2ADP + 2P

4ADP + 4P----> 4ATP

NET 2 ATP for cell use

Glycolysis is does not need oxygen. This process occurs in the cytoplasm. Two net molecules of ATP are made for cell use. It involves glucose being converted to two molecules of pyruvic acid.

Glycolysis involves glucose being converted to two molecules of pyruvic acid. This process is not very efficient at converting the energy of glucose into ATP as only 2 ADP are phosphorylated instead of 32 as in Krebs and chemiosmosis.

Glycolysis is does not need oxygen. This process occurs in the cytoplasm. Two net molecules of ATP are made for cell use. It involves glucose being converted to two molecules of pyruvic acid.

Glycolysis involves glucose being converted to two molecules of pyruvic acid. This process is not very efficient at converting the energy of glucose into ATP as only 2 ADP are phosphorylated instead of 32 as in Krebs and chemiosmosis.

The first four steps of glycolysis is called the investment phase because energy is put into the system instead being made.

2 ATP consumed rather than made.

In the last 6 steps of glycolysis energy is harvested. 4 ATP are made and two NAD are reduced to form NADH. In the end, the glucose molecule is converted to 2 molecules

of pyruvic acid or pyruvate. This will be shuttled to the mitochondrion where the last hydrogens will be stripped off to reduce more molecules of NAD and FAD.

Step 1 _____________

Glucose becomes glucose-6-phosphate. This requires the use of ATP. Glucose-6- phosphate is more unstable and has more energy than regular glucose.

Energy is put into the system

Step 2________________

Glucose-6-phosphate is turned into fructose-6-phosphate. Both of these molecules are hexose and have the same molecular formula. This is called isomerization.

Step 3_______________

Fructose-6-phosphate becomes 1,6 fructose biphosphate. This requires another ATP to be used. This new molecule is more unstable and has more energy than the old one.

Step 4_______________

This hexose is unstable, and will split to produce two trioses, dihydroxy acetone and PGAL. Dihydroxy acetone will turn into PGAL. From this point on, everything is multiplied by two.

Step 5________________

The PGAL will be turned into diphosphoglyceric acid. The molecule will lose hydrogen and gain inorganic phosphate. The hydrogen will be transferred to NAD to become NADH. NADH has more energy than NAD.

Step 6_________________

One of the phosphates from the molecule is transferred to ADP to make or phosphorylate ATP. The new molecule left is phosphoglyceric acid.

Step 7

This is a step that involves moving the phosphate group from the end carbon to the middle carbon. This increases the energy of the molecule. This makes it more unstable.

Step 8

This is a step that involves removing a molecule of water or dehydration.

Step 9_________________

This is a step that involves removing a phosphate and putting it on ADP or phosphorylating ADP to make another ATP. Now 4 molecules of ATP been made.

Summary of Glycolysis

I. Glycolysis-cytoplasm-

Glucose----> 2 pyruvic acid

2NAD + 2H---->2NADH

2ATP---->2ADP + 2P

4ADP + 4P----> 4ATP

NET 2 ATP for cell use

After glycolysis, the pyruvic acid will go into the mitochondria, so that the rest of energy stored in the hydrogen can be extracted. If no there is no oxygen, then the Kreb's cycle can not completed. A cell can continue doing glycolysis in the absence of oxygen BUT it must regenerate NAD to keep going. This step of regenerating NAD from NADH is called fermentation. Anaerobic respiration = fermentation + glycolysis.

The next step in the absence of oxygen, pyruvate will form either lactic acid (muscles) or ethanol (bacteria, yeast or plants). In either case NAD is regenerated so that glycolysis can continue. This is called anaerobic respiration. If oxygen is available, then the pyruvic acid will be shuttled to the mitochondria so that Kreb's cycle will take place.

After glycolysis, the pyruvic acid will go into the mitochondria, so that the rest of energy stored in the hydrogen can be extracted. If no there is no oxygen, then the Kreb's cycle can not completed. A cell can continue doing glycolysis in the absence of oxygen BUT it must regenerate NAD to keep going.