Cellular Energy

OOO-WEE-ATP

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All cells need energy. Energy is the ability to do work. The most common type of energy that a cell uses is ATP or adenosine triphosphate.

ATP contains the pentose sugar, ribose.

ATP also contain the nitrogenous base, adenine.

This is the same base found in DNA and RNA.

Also attached to the ribose are three phosphate groups. Notice the negative charges.

When objects have the same charge, they repel one another. This makes the bond between the phosphates very weak. The bonds are unstable. They are called high energy bonds. Seldom is ATP shown with all the atoms quite often is symbolized as shown below.

OR

These phosphates can be used to do work. When a phosphate is put on to another molecule, it destablilizes that molecule in other words, it gives that molecule energy. It increases the energy content of the molecule.

When ATP loses a phosphate, it become ADP or adenosine diphosphate.

ATP ->ADP + P

ATP is needed to make muscles move. Below is a muscle protein and how ATP is used to make it contract.

Which of the following will have the greatest amount of energy?

A) ATP B) ADP C) NaCl D) GDP

A

ATP has more energy than any of the other molecules listed. The energy is found in the phosphate-to-phosphate bonds. These are weak bonds. ATP has two of these bonds and ADP and GDP has only one of these bonds.

Examples of how ATP is used in the cell.

Another way a cell uses energy is by moving hydrogen, and electrons around. Giving a molecule hydrogen, increases the energy content of that molecule .

For example compare gasoline with carbon dioxide. Which has more energy? Now look at their molecular structure

Which of the following is true?

A) Adding ribose to another molecule is a common way to transfer energy in a cell.

B) Removing adenine from another molecule is a way to decreas energy in a cell

C) Adding phosphate to another molecule is a common way to transfer energy in a cell.

D) Removing guanine from another molecule is a way to decreas energy in a cell

C

Transferring phosphate to another molecule is a common way to move energy in a cell. ATP and GTP are common phosphate carriers.

Gasoline has more energy because it has more hydrogen. In the cell there are hydrogen carriers. These are molecules that transfer hydrogen from one molecule to another.

The process of moving hydrogen and electrons from one molecule to another is called oxidation-reduction reactions or redox reactions. When hydrogen or electrons are removed from one molecules another molecule must receive them.

Which of the following has more energy and why?

A) Gasoline because it has more hydrogen and less oxygen than carbon dioxide

B) Gasoline because it has more carbons than carbon dioxide

C) Carbon dioxide because it has more oxygen than gasoline D) Carbon dioxide because it has double bonds and gasoline does not.

A

Gasoline because it has more hydrogen and less oxygen than carbon dioxide. The more hydrogen a molecule has the more energy it has and the more oxygen a molecule has the less energy it has.

Gasoline has more energy because it has more hydrogen. The more hydrogen a molecule has, the MORE energy it has. The more oxygen a molecule has, the LESS energy it has. Moving hydrogen from one molecule to another is another way to move energy around in the cell.

In the cell there are hydrogen carriers. These are molecules that transfer hydrogen from one molecule to another.

The process of moving hydrogen and electrons from one molecule to another is called oxidation-reduction reactions or redox reactions. When hydrogen or electrons are removed from one molecules another molecule must receive them.

Which of the following is an example of molecular reduction?

A) Adding oxygen to the molecule

B) Adding carbon to the molecule

C) Removing oxygen from the molecule

D) Removing hydrogen from the molecule

C

The list below summarizes the rules for oxidation reduction.

Oxidized Reduce

1. Remove H 1. Add H

2. Remove e- 2. Add e-

3. Add oxygen 3.Remove oxygen

Oxidizing a molecule, decreases the energy content of that molecule and reducing a molecule increases the energy content of that molecule.

Oxidized Reduce

1. Remove H 1. Add H

2. Remove e- 2. Add e-

3. Add oxygen 3.Remove oxygen

The molecule that receives the electrons or hydrogen are said to be reduced and the molecule that loses them are said to be oxidized. In the formation of sodium chloride, NaCl, Na becomes oxidized Na+ and Cl- becomes reduced.

Also note that because Na is an electron donor, it is called reducing agent and because Cl is an electron acceptor, it is called an oxidizing agent. Chlorine is such an excellent oxidizing agent that it readily remove e- from stains and bacteria making a great laundry whitener and water purifier.

The ability of a substance to pass on its electrons is called its reducing power. Different hydrogen carriers will have varying reducing power.

Three important hydrogen carriers are NAD+ (nicotinamide adenine dinucleotide), NADP+ (nicotinamide adenine dinucleotide phosphate), and FAD (flavin adenine dinucleotide). These molecules have the ability to gain or lose hydrogens and electrons.

These molecules are also coenzymes which means that they work together with enzymes-

Which of the following is not a hydrogen carrier?

A) NAD B) ATP C) NADP D) FAD

B

ATP is not a hydrogen carrier.

When NAD+ gains 2 electrons and hydrogen it is called NADH and when NADP+ gains 2 electrons and hydrogen it is called NADPH. Look at NAD+ and NADH and see where the extra hydrogen is

Compare NADPH and NADP+ and determine what is the difference between these two hydrogen carriers.

Compare FAD and FADH2 and determine what is the difference between these two hydrogen carriers.

Here is an example of how NAD moves hydrogen around in the cell. PGAL will be oxidized and NAD+ will be reduced. Hydrogen from PGAL has been transferred to NAD+. PGAL, a triose, has more energy than DPGA, an acid. NADH has more energy than NAD+.

Which of the following is true of the chemical reaction above?

A) PGAL is oxidized

B) DPGA is reduced

C) NAD is reduced

D) Phosphate is oxidized

C

NAD picks up hydrogens so therefore it is reduced.

Quite often, there are hydrogen pumps that pump H+ ions across a membrane. If the concentration of ions is greater than the other side of the membrane, this causes one side of the membrane to have a different charge than the opposite side of the membrane. This is similar to a battery. These ions can move across the membrane and as the ions move across the membrane, it can do work. Usually these ions are H+ ions. These ions flow across the membrane due to differences in concentration and charge. This process is called chemiosmosis.