Chapter 9: “Cellular Respiration”

Think of Photosynthesis like baking a cake.

The plant takes the raw materials (CO2 & H2O), puts them together using energy (heat), & synthesize the cake.

In order to get the energy out of the cake, the plant & us must ingest it (eat), digest it (break it down into its monomers) & then we must “burn it” to release the energy stored in the bonds of the cake.

THIS IS RESPIRATION

How do we get the energy out of the food that we have consumed?

Cellular Respiration

• Is the process by which organisms obtain the energy they need by releasing the chemical energy stored in nutrients and transferring that energy into ATP

•Nutrient = Glucose•Chemical Energy = ATP

Occurs in the Mitochondria

of Eukaryotic organismsRespiration occurs on the cristae

Does this sound familiar?

Two Types of Respiration

• Aerobic Respiration – needs oxygen to release the energy in food

C6H12O6  +  6O2    6CO2  +  6 H2O  + 36 ATP

• Anaerobic Respiration – can release the energy from food without the need of oxygen. (Some bacteria & yeast)

C6H12O6    2 CO2  +  2 Ethanol  +  2 ATP = alcoholic fermentation

C6H12O6    2 Lactic Acid  +  2 ATP = lactic acid fermentation

Anaerobic Respiration

• Also known as fermentation• Occurs in the cytoplasm of yeast, some bacterial cells

• Since the organisms are very small and their needs are simple, they do not need much ATP

Anaerobic Respiration occurs in two steps

1. Glycolysis

Glucose (6 Carbons) is broken down into 2 Pyruvic (3 Carbons each) acid molecules + 2 ATP (activation energy)

Produces 4 ATP, netting 2 ATP

2 ATP

Fermentation

• The 2 Pyruvic Acids will break down into:

1. Alcohol + CO2 (yeast and some bacteria)

2. Lactic Acid (bacteria, us – more later)

Both forms will not produce any more ATP molecules

Uses for Fermentation

• Yeast & some bacteria

Used in baking, wine making and brewing industry

• Bacteria

Lactic acid production is used in cheese processing, buttermilk, sour cream, yogurt, sauerkraut, pickles. The souring of dairy products is actually the production of lactic acid by anaerobic bacteria

Aerobic Respiration•Occurs in the mitochondria

•Yields more ATP per molecule of glucose (36 – 38 molecules) of ATP/Glucose

•Occurs in 3 basic steps

1. Glycolysis

Using 2 ATP as activation energy, a glucose molecule is broken down into 2 Pyruvic Acid molecules. 4 ATP are produced, leaving 2 ATP netted. Occurs in cytoplasm.

2. Krebs Cycle – in the Mitochondria, the 2 Pyruvic acids are broken down, releasing CO2 & producing 2 ATP

3. Electron Transport Chain – Oxygen combines with hydrogen

32 ATP are produced

Krebs Cycle

Pyruvic Acid

2 Carbon Dioxides

Carbon Dioxide

How much more efficient is Aerobic Respiration than

Anaerobic Respiration at releasing ATP from one molecule of glucose?

Aerobic respiration yields 2 + 2 + 3236 ATP

Anaerobic respiration yields 2 ATP 2 ATP _______

36: 2

Bottom Line: Aerobic Respiration is 18x more efficient!!!

Muscle Fatigue

• You are a large organism and need a lot of ATP to keep you fueled.

• At times though, you may not be breathing correctly & therefore, are not taking in enough O2 to remain an aerobic organism.

• During this time, your body (muscle cells) converts to anaerobic respiration to give you some ATP. Hey, 2 ATP are better than none!

• Lactic acid accumulates in your muscle cells, acid burns the cells, causing you to cramp up & thus slowing down your activity

• When you begin to breathe normally again, the lactic acid breaks down and the “O2 debt” is paid