1. Cellular Respiration
Chapter 8.3

2. Discussion Question #5 What is the equation for photosynthesis?
What is the equation for cellular respiration?
What is the purpose of photosynthesis?
What is the purpose of cellular respiration?

3. What is ATP? ATP (Adenosine Triphosphate)
Consists of an adenine, ribose and triphosphate tail
ATP are little packets of energy that cells can use as energy to do the functions necessary for life
Remember energy is created by bonds breaking
When the bonds between the phosphate molecules are broken it releases energy that the cell can use
When a bond of an ATP molecule is broken you get: ADP, phosphorus and energy

4. Respiration vs Cellular Respiration
Aerobic vs Anaerobic
Aerobic means it requires oxygen
Anaerobic means it does not require oxygen
Respiration vs Cellular Respiration
When we think of respiration we think of breathing
Breathe in oxygen breathe out carbon dioxide
Cellular respiration is similar except instead of an organism breathing, it is only the cell that is “breathing” and instead of just breathing in oxygen it is also using sugar(glucose)
Glucose is the fuel that give cells energy
The purpose of cellular respiration is to MAKE ATP!!!!!!!!!!

5. Cellular Respiration
Cells can use carbohydrates, proteins or fats to do cellular respiration and create ATP but cells prefer to use carbohydrates and that is what we will use to show the steps of cellular respiration.
The diagram above shows the basic idea of cellular respiration
Where does cellular respiration occur?
It occurs in the mitochondria (power houses)
of the cell along the folds
The sum of chemical reactions that create
energy for the cell is called metabolism
There are 3 stages in cellular respiration
Glycolysis- breaking down 1 glucose into 2 molecules of pyruvate
Krebs Cycle- loads the electron carriers like NADH with electrons & H+ ions for final step
Electron Transport Chain- the payoff that creates most of the ATP, 34 actually

6. Cellular Respiration Overall Process

7. Stage 1: Glycolysis
Glycolysis- the process of breaking a 6 carbon glucose molecule into two 3 carbon pyruvate molecules
This occurs in the cytoplasm, outside of the mitochondria and does not require any oxygen ……Remember “lyse” means to dissolve, explode, break apart
Steps (uses 2 ATP to create 4 ATP = net gain of 2 ATP)
One 6 carbon glucose molecule uses 2 ATP to split glucose and create 2 G3P
The G3P molecules break their phosphate bonds which produces 2 ATP each. The resulting molecules are 2 pyruvate molecules which will get moved inside the mitochondria and enter the Krebs Cycle
The creating of ATP also fills NAD+ with electrons and H+ to make NADH
NADH will carry those electrons & H+ ions to the 3rd stage

8. Stage 2: Krebs Cycle (Citric Acid Cycle)
The 2 pyruvate molecules created in glycolysis are moved inside the mitochondria
Once inside the mitochondria each 3 carbon pyruvate loses a carbon and becomes a carbon acetyl CoA molecule (with the help of water)
The carbons that are lost combine with oxygen in the mitochondria to create CO2 which are then released out of the mitochondria, H+ & e- are released and attached to NAD+ NADH
Each acetyl CoA molecule then enters the Krebs Cycle and combines with an oxaloacetate to create a 6 carbon Citric Acid molecule
The citric acid molecule breaks off 2 of its carbons which become 2CO2 & also creates 1 ATP
FAD and NAD+ molecules are found in the Krebs Cycle and during the cycle they gain electrons and H+ ions and become FADH2 and NADH. Those electrons and H+ ions will be used to create energy in step 3.
Each full cycle produces 3 CO2, 1 ATP, 4 NADH, and 1 FADH2 (NADH = 3ATP/H FADH2 = 1ATP/H)
This whole process happens twice, once for each of the Acetyl CoA molecules that go in
Citric Acid
Pyruvate
oxaloacetate

9. Stage 3: Electron Transport Chain
In the electron transport chain NADH that was produced in glycolysis and the NADH and FADH2 that were produced in the Krebs Cycle dump their electrons into the electron transport chain located on the mitochondria membrane
When NADH and FADH2 dump their electrons and H+ ions which build up on the outside of the membrane, these NAD+ & FAD will be reused again
After the electrons have gone through the ETC they are snatched up by oxygen (the final electron acceptor) that was brought into the cell when you took a breath
The buildup of H+ ions on the outside of the membrane gets moved through a protein called ATP synthase which works like a turbine and creates ATP by converting ADP back into ATP by attaching a phosphate to ADP and this creates 34 ATP to be used by the cell for energy
As each H+ ion moves through the ATP synthase protein it combines with an oxygen molecule to create H2O

10. Summary of Cellular Respiration
Don’t forget- the purpose of cellular respiration is to make ATP!!!
1 glucose molecule yields 38 ATP
Glycolysis
Turns 1 glucose molecule into 2 pyruvate molecules and yields 2 net ATP
Krebs Cycle
Turns pyruvate into  Acetyl CoA  enters Krebs Cycle gets turned into citric acid releases those carbons creating CO2 and creating electron carriers that will transport electrons to the last stage, each cycle turn creates 1 ATP and you go through 2 cycles
ETC
The electrons created in steps 1&2 go down a chain which releases some energy and causes H+ ion to go through ATP synthase and create 34 ATP
The process then starts again
with a new glucose molecule
Think about how much work
is required to break down 1
glucose molecule for energy

11. Fermentation This is the reaction for cellular respiration
What happens if there is no oxygen present during cellular respiration???
The cell can still make ATP through a process called fermentation
Fermentation- the process of creating ATP in the absence of oxygen
Also called anaerobic respiration because it does not require oxygen
In fermentation the only part of cellular respiration that is done is glycolysis. Fermentation skips the Krebs Cycle and Electron Transport Chain
Muscle Cell Fermentation
Microbe Fermentation

12. Lactic Acid Fermentation
Normally the final electron acceptor oxygen takes the electrons and H+ ions from NADH to convert it back to NAD+ at the end of the ETC and the NAD+ gets reused in glycolysis
But if there is not oxygen in the cell to turn the NADH back into NAD+ to get reused the cell begins the fermentation process because the cell runs out of NAD+
To reuse the NAD+: when the NAD+ gets converted into NADH the cell takes the extra H+ ions and electron from NADH and attaches it to the pyruvate molecules
When the cell attaches the H+ ions and electrons to the pyruvate it creates lactic acid and allows the NAD+ to get reused
Glucose still gets broken up into 2 pyruvate molecules which produces ATP…but it also produces 2 new molecules called lactic acid
Our muscles need oxygen. If you are sprinting or lifting weights your muscles can’t get the oxygen they need fast enough to make the energy your body is needing so it starts fermentation which causes your cells to produce lactic acid which burns
When you get oxygen back to your muscles the lactic acid goes away

13. Ethanol/Alcohol Fermentation
Single celled microorganisms can also do fermentation (anaerobic respiration) if there is no oxygen available…and actually some organisms prefer it
When yeast are given glucose to eat without any oxygen they start glycolysis and utilize fermentation
Remember fermentation occurs because we need to be able to convert the NADH back into NAD+ and the only way to do that is to take the H+ ions and electrons from NADH and add them to pyruvate which will produce ethanol in this process
They still break glucose down into 2 pyruvates which produces 2 ATP
But instead of those 2 pyruvate molecules getting turned into lactic acid they get turned into 2 molecules of ethyl alcohol and in the process produce CO2
Yeast can do this in bread dough to make bread or yeast can be added to sugary drinks to create alcohol
Some yeast can also utilize lactic acid fermentation and turn milk into cheese