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 organisms
Respiration
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
Carbon Dioxide
2 Carbon Dioxides
How much more efficient is Aerobic
Respiration than Anaerobic Respiration at
releasing ATP from one molecule of glucose?
Aerobic respiration yields 2 + 2 + 3236 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