Cellular Respiration

I. Laws of Thermodynamics

• A. Energy can never be created or destroyed. The sum of energy in the universe is constant.– 1. 1st law of thermodynamics – cells cannot take energy

out of thin air it must harvest it somewhere– 2. 2nd law of thermodynamics – energy transfer leads to

less organization or increase in entropy

II. Chemical Energy & Food

• A. One gram of sugar can release 3811 calories of heat (1 kilocalorie found on food labels is 1000 calories)

• B. Cells do not “burn” glucose, instead, they gradually release energy by breaking down the molecular bonds

III. Cellular Respiration• A. Cellular Respiration is the process that releases

energy by breaking down glucose and other food molecules in the presence of oxygen.

6O2 + C6H12O6 6CO2 + 6H2O + EnergyOxygen + Glucose Carbon dioxide + Water + Energy

• B. Cellular Respiration does not release the energy at once instead it occurs in steps releasing energy little by little

III. Cellular Respiration• C. Steps of Cellular Respiration:– 1. Glycolysis (substrate phosphorylation)• Formation of acetyl CoA

– 2. Krebs Cycle – 3. Oxidative phosphorylation/Electron Transport

Chain (ETC)• D. Each step captures some of the chemical

energy available in food molecules and uses it to produce ATP.

What is ATP?????

IV. ATP

• A. Adenosine triphosphate (ATP) – is a molecule of adenosine bonded to three phosphates. – 1. An enormous amount of

energy is packed in between the phosphate bonds, specifically the 3rd one.

ATP ADP + Pi + energy

Steps of Cellular Respiration

– 1. Glycolysis (substrate phosphorylation)• Formation of acetyl CoA

– 2. Krebs Cycle – 3. Oxidative phosphorylation/Electron Transport

Chain (ETC)

V. Glycolysis• A. Glycolysis is the process in which

one molecule of glucose is broken in half, producing 2 molecules of pyruvic acid, a 3-carbon compound.

• B. Glycolysis releases energy(4) but needs a little bit of energy(2) to begin the process.

• C. During glycolysis 4 high-energy electrons are removed and carried by NAD+ converting it into 4 NADH

Formula for glycolysis (glucose breaking)Occurs in the cytoplasmGlucose + 2ATP+2NAD+2Pyruvic acid+4ATP+ 2NADH

Several smallEnzyme rxn.s

VI. Glycolysis Without Oxygen

• A. If oxygen is not present during glycolysis it follows a slightly different path known as fermentation.

• B. Because fermentation does not require oxygen it is said to be anaerobic. There are 2 types of fermentation– 1. Alcoholic fermentation– 2. Acid fermentation

VI. Glycolysis Without Oxygen• a. Yeast and other microorganisms use alcoholic

fermentation, transforming pyruvic acid into ethyl alcohol and carbon dioxide waste

• b. Lactic acid is produced during rapid exercise when your muscles aren’t supplied with plenty of oxygen. (muscle cramps)

VII. Where are we in the cell?

• Structure of a mitochondria

IIX. Formation of Acetyl CoA

• A. When oxygen is present pyruvic acid is transported to the mitochondion.

• B. Each pyruvic acid (3-carbon molecule) is converted into acetyl coenzyme A (2-carbon molecule) and CO2 is released.

Equation: 2 Pyruvic acid + 2 Coenzyme A + 2 NAD+

2 Acetyl CoA + 2 CO2 + 2 NADH

IX. Krebs Cycle (Citric acid)• A. In order for the Krebs cycle to follow glycolysis

you need oxygen to be present this process is said to be aerobic. (cellular respiration)

• B. During Krebs cycle acetyl coenzymes are broken down into carbon dioxide in a series of energy-extracting reactions in the mitochondria matrix. – 1. During the Krebs cycle oxaloacetate combines with

acetyl CoA to create citric acid (6-carbon molecule)– 2. The electron carriers accepting the e- (NAD+ &

FAD)will generate huge amounts of ATP

2 pyruvic acid + 8NAD+ + 2FAD + 2ADP 6CO2 + 8NADH + 2FADH2 + 2ATP

X. Electron Transport “Pay off”

• A. ETC uses the high-energy electrons to convert ADP to ATP– 1. e- come from NADH and FADH2

• B. The electron transport chain is located along the mitochondria inner membrane (cristae)

• C. Oxygen is the final accepter of these high-energy electrons, creating water (waste product) at the end of the reactions. This is called oxidative phosphorylation

• All together we created 12 high energy carries2 NADH glycolysis, 2NADH Acetyl CoA, 6 NADH

Krebs, 2 FADH2 Krebs

X. Electron Transport “Pay off”

• D. NADH & FADH2 shuttle electrons to the ETC and the hydrogen atoms are split.

H2 2H+ + 2e-• E. The e- are passed down protein carries

(cytochromes); while the hydrogen ions are pumped using some the energy across the inner membrane into the intermembrane space creating a pH gradient/proton gradient. – H ions only diffuse back through ATP synthase

XI. The Totals

• Glycolysis: ____

• Krebs Cycle: ___

• ETC:____For every 1 NADH 3 ATP madeFor every 1 FADH2 2 ATP made

Photosynthesis vs. Cellular Respiration

FunctionLocation (organelle)ReactantsProductsEquation