Cellular Respiration

You feel weak when you are hungry because food serves as a source of energy. How does the food you eat get converted into a usable form of energy for your cells?

Chemical Energy and Food Calorie – amount of energy needed to raise a

temperature of 1 gram of water by 1 degree Celsius

Cells use all sorts of molecules for food, including fats, proteins, and carbohydrates. The energy stored in each of these molecules varies because their chemical structures, and therefore their energy-storing bonds, differ.

Cells break down food molecules gradually and use the energy stored in the chemical bonds to produce compounds such as ATP that power the activities of the cell.

Where do organisms get energy?

Food = chemical energy It provides living

organisms with chemical building blocks they need to grow and reproduce

ATP = organic molecule containing high energy bonds -powers most cell activities (cell energy)

Cellular Respiration Overview Transformation of chemical energy in food into

chemical energy cells can use: ATP cellular respiration

Overall Reaction: C6H12O6 + 6O2 → 6CO2 + 6H2O

Glucose + Oxygen Carbon dioxide + Water + Energy

Stages of Cellular Respiration1) Glycolysis2) Krebs cycle3) Electron transport chain

Stages of Cellular Respiration1) Glycolysis – produces small amount energy Glucose is broken down to

pyruvate acid during glycolysis making some ATP

Most of the glucose’s energy (90%) remains locked in the chemical bonds of pyruvic acid at the end of glycolysis

Stages of Cellular Respiration2) Krebs Cycle – little more energy is generated from pyruvic acid

Stages of Cellular Respiration3) Electron transport chain–produces a bulk of the energy in cellular respiration by using oxygen, a powerful electron acceptor

Oxygen and Energy Aerobic- process that

requires oxygen Krebs cycle and electron

transport chain are aerobic Both take place in

mitochondria

Anaerobic- process that does not require oxygen Glycolysis is anaerobic Takes place in cytoplasm

Photosynthesis vs. Cellular Respiration

The reactants of cellular respiration are the products of photosynthesis and vice versa.

The release of energy by cellular respiration takes place in plants, animals, fungi, protists, and most bacteria.

Energy capture by photosynthesis occurs only in plants, algae, and some bacteria.

Fermentation

We are air-breathing organisms, and we use oxygen to release chemical energy from the food we eat. But what if oxygen isn’t around? What happens when you hold your breath and dive under water, or use

up oxygen so quickly that you cannot replace it fast enough?

Fermentation Fermentation - in the absence

of oxygen, fermentation releases energy from food molecules by producing ATP

Electron transport chain doesn’t run WHY?

Alcoholic Fermentation –yeasts are other organisms use alcoholic fermentation produces ethyl alcohol and carbon dioxide

Lactic Fermentation – MOST organisms carry out fermentation using a chemical reaction that converts pyruvic acid to lactic acid

Energy and Exercise Quick bursts of energy body uses

ATP present in muscles and ATP made by lactic acid fermentation

Exercise longer than 90 seconds cellular respiration is the only way to continue generating a supply of ATP

Lactic acid fermentation can supply enough ATP to last about 90 seconds. However, extra oxygen is required to get rid of the lactic acid produced. Following intense exercise, a person will huff and puff for several minutes in order to pay back the built-up “oxygen debt” and clear the lactic acid from the body.