ATP and Cellular Respiration Review

Chemical Reactions -Millions of chemical reactions are continuously carried out in our cells, some releasing and others consuming energy. We need energy to power our metabolic reactions.

Adenosine Triphosphate (ATP) -One of the most important compounds that cells use to store and release energy is adenosine triphosphate (ATP)

ATP -ATP can easily release and store energy by breaking and forming bonds between its phosphate groups. -An efficient way to continuously store energy and then release it when needed by one reaction.

Adenosine Triphosphate (ATP)

How is ATP used? -Energy is stored in the bonds between the phosphate groups in ATP -A phosphate group bond can be broken, releasing useable energy for the cell. What happens to ATP now that a phosphate group has been removed?

ADP

Converting between ATP and ADP

Building or breaking -When your body needs to use energy, you break down ATP to ADP. -When your body is storing energy, you are building up ADP to ATP.

ATP & Long-Term Storage ATP is not a good for storing large amounts of energy over the long term. It is more efficient for cells to regenerate ATP from ADP as needed by using the energy in foods like glucose as a single molecule of glucose stores more than 90 times the chemical energy recharge ATP.

The need for ATP -How can our cells continuously reassemble ATP? Where does the energy come from?

Cellular Respiration -Process by which the chemical energy of “food” molecules is released & partially captured in the form of ATP

Cellular Respiration can be divided into 3 processes 1. Glycolysis 2. Krebs Cycle 3. Electron Transport Chain -Each step releases more and more of the energy stored in glucose.

Stages of Cellular Respiration

Where does this happen? 1. Glycolysis 2. Krebs Cycle in the cytoplasm 2. Krebs Cycle in the mitochondrial matrix 3. Electron Transport Chain (Oxidative phosphorylation) at the surface of the inner mitochondrial membrane

ATP production -Each molecule of glucose can generate a total of 36 ATP molecules during the 3 steps of cellular respiration.

Glycolysis -Breakdown of glucose inside the cell; “sugar breaking”

Gylcolysis Products -Net gain of 2ATP molecules and 2 NADH as glucose is converted to pyruvic acid -Glycolysis does not require oxygen; it is an anaerobic process.

Glycolysis

A long way to go…. -Most of glucose’s energy (90%) remains locked in chemical bonds at the end of glycolysis.

If oxygen is not present after glycolysis: -If oxygen is not present (anaerobic respiration), then fermentation.

Fermentation -Fermentation is a process by which energy can be released from food molecules in the absence of oxygen. Fermentation occurs in the cytoplasm of cells.

If oxygen is present after glycolysis: Krebs cycle (aerobic respiration)

The Krebs Cycle -In the second stage of cellular respiration, pyruvic acid produced in glycolysis is broken down into carbon dioxide in a series of energy-extracting reactions.

Krebs Cycle -enzymes break down pyruvate to carbon dioxide and generate a pool of energy (ATP, NADH, FADH2) through oxidation -CO2 is released in this process; this is why we exhale CO2

Kreb’s Cycle Products Per Glucose Molecule -For each glucose molecule, 6 CO2 molecules, 2 ATP molecules, 8 NADH molecules, and 2 FADH2 molecules are produced. -NADH and FADH2 are molecules formed by electron addition. They accept electrons from NAD+ and FAD.

ETC -The electron transport chain produces the bulk of the energy in cellular respiration by using oxygen, a powerful electron acceptor.

Electron Transport Chain ETC -The electron transport chain uses high-energy electrons to convert ADP into ATP; it allows the release of the large amount of chemical energy stored in NADH and FADH2

Total Breakdown of Glucose Glycolysis  2 ATP Kreb’s Cycle  2 ATP ETC  32 ATP Total 36 ATP from aerobic cellular respiration

Energy Totals -This represents about 36 percent of the total energy of glucose. The remaining 64 percent is released as heat.

Overall equation for Cellular Respiration