Cellular Respiration

Cellular Respiration Energy in food is stored as carbohydrates, proteins & fats. Before you can use that energy, it must be released and transferred to ATP.

Cellular respiration is the process that releases energy by breaking down food molecules in the presence of oxygen. Formula: C6H12O6 + 6O2 6CO2 + 6H2O + 34 ATP Glucose+ Oxygen CO2 + H2O + Energy

3 Steps of Cellular Respiration If cellular respiration took place in just one step, all energy would be released at once and our cells need to control this.

Glycolysis – The process in which one molecule of glucose is broken in half, producing 2 molecules of pyruvic acid (a 3 carbon compound) Glucose C6 Pyruvate Pyruvate C3 C3 2 ADP + 2NAP+ 2 ATP + 2NADH

Glycolysis… Takes place in the cytoplasm Net gain of 2 ATP Takes place without oxygen (anaerobic) NADH is formed (electron carrier) Interesting Fact: Since bacteria don’t have any membrane-bound organelles such as mitochondrion, they can only produce ATP by glycolysis!

Two Things Can Happen: (in Eukaryotic Cells) 1. Anaerobic Respiration - If no oxygen is present, pyruvate goes through a process called “fermentation.” 2. Aerobic Respiration – If oxygen is present, pyruvate enters the mitochondria and enters the “Kreb’s Cycle.”

Two Pathways Anaerobic Or: Aerobic What’s the difference? C6 Glycolysis C3

Fermentation – Recycles the NAD+ that is needed to make ATP in the absence of oxygen. Pyruvate Alcohol Lactic Acid (plants) (animals) 2 ATP CO2 ~ Takes place in the cytoplasm

Lactic acid is produced in your muscles during rapid exercise when the body cannot supply enough oxygen to the tissues. The buildup of lactic acid causes a painfull burning sensation.

2. Krebs Cycle – A stage of aerobic (requires oxygen) respiration in which pyruvate is converted into CO2, water and ATP. ~ Takes place in the mitochondria

What happens to all of the high energy electrons??? The Kreb’s Cycle is a continuous cycle of electrons transferred to energy carriers. Citric acid is broken down, CO2 is released (you exhale it out), and ATP is released to be used in cellular activities. What happens to all of the high energy electrons??? Citric Acid

3. Electron Transport Chain – Takes place along the inner membrane of the mitochondria. A protein in the membrane called ATP synthase. These enzymes convert ADP to ATP. 34 ATP are produced (Lots of energy!)

Electron Transport Chain

ATP Synthase

The Totals In the absence of oxygen, glycolysis produces just 2 ATP molecules per glucose.

In the presence of oxygen, everything changes. The Kreb’s Cycle & electron transport chain allow the cell to produce 34 more ATP molecules. 36 total ATP!

18 times as much can be generated from glucose in the presence of oxygen. The final waste products are water and carbon dioxide.

So….Why do we breathe?

38% of the energy in glucose is used to make ATP 38% of the energy in glucose is used to make ATP. 62% is released as heat. (This is why you become warm when you exercise).

Comparing Photosynthesis & Cellular Respiration Function Location Reactants Products Equation

Photosynthesis & Cellular Respiration are almost opposite processes. Photosynthesis “stores” energy Cellular Respiration “releases” energy What do you notice about the equations????