Turning Sugar into ATP

Cellular Respiration
• The overall equation for cellular respiration can be misleading if you consider its true purpose:
▫ To release stored for cells to use

Cellular Respiration
• A more accurate representation would be something like this

Cellular Respiration
• Remember that Photosynthesis and Cellular
Respiration are opposites

Cellular Respiration
• The energy that comes out of cellular respiration is in the form of ATP
▫ Remember ATP? The small form of energy that our cells can use for…
 everything
 Active transport, cell movement, cell processes like building molecules & breaking molecules, muscle contraction, etc.
 ATP keeps your cells (you) alive

Cellular Respiration
• There are two types of Cellular Respiration
▫ Aerobic Cellular Respiration
 Your cells do this when they have oxygen
▫ Anaerobic Cellular Respiration
 Your cells do this when they don’t have enough oxygen
▫ All cells do cellular respiration to keep alive.
 Animal cells can do anaerobic but not enough to sustain life
 Some bacteria and fungi can do either one and stay alive
(facultative anaerobes)but there are some who can not live with oxygen (obligate anaerobes)

Aerobic Cellular Respiration
• There are 4 steps to Aerobic Cellular Respiration and they all contribute in 1 or 2 ways to making
ATP
• By the end, we should have a total of approximately 36 ATP!
▫ Sometimes you will see 38 ATP or even strange numbers like 25 ATP, but 36 is the total we will use in this class

Aerobic Cellular Respiration
• Steps and their location within the cell
▫ Step 1: Glycolysis (Cytoplasm)
▫ Step 2: Pyruvate Oxidation (Mitochondrial matrix)
▫ Step 3: Krebs Cycle (Mitochondrial Matrix)
▫ Step 4: Electron Transport Chain (Inner mitochondrial membrane)

Aerobic Cellular Respiration
• Parts of the Mitochondria (Mt)
▫ You might remember that it is the “Powerhouse” of the cell, so most of the ATP is made within it.

Mitochondrion

Aerobic Cellular Respiration
• For each step we learn, our focus is “How is it making ATP?”
• There are two ways that Aerobic Cellular
Respiration produces ATP
▫ Chemiosmosis
 Which you already saw in Photosynthesis
▫ Substrate-Level Phosphorylation
 Which is new but you don’t need to know in detail

Aerobic Cellular Respiration
• Chemiosmosis will take place in the Electron
Transport Chain step (just like with photosynthesis)
• The energized electrons will create a H + concentration gradient which will lead to diffusion of H + through the ATP Synthase
Complex
• This will produce 32 out of our total 36 ATP

Aerobic Cellular Respiration
• Substrate-Level Phosphorylation means taking a phosphate from the “substrate” and adding it to
ADP to make ATP
▫ A substrate is the molecule we are breaking down
 In the beginning, this molecule is glucose
• This will happen in the Glycolysis and Krebs Cycle steps
• There is some chemistry magic involved in this
(unstable bonds and such) that we won’t be learning in Bio
20
• This will produce 4 (2 each) out of our total 36 ATP

Step 1: Glycolysis
literally means “sugar splitting”
Sugar Splitting
• This is where the Glucose (from photosynthesis) begins to break down
• This step takes place in the cytoplasm of the cell

Step 1: Glycolysis
• The glucose is split into two molecules called
Pyruvates, or pyruvic acids (same thing)
• When glucose
(C
6
H
12
O
6
) is split into 2 pyruvates, some products are made:
▫ The glucose is oxidized by 2NAD + making 2NADH
 NAD + is similar to NADP + from photosynthesis; it is an electron carrier and therefore another form of stored energy
 These 2NADH will be important for making ATP through chemiosmosis in the last step

Step 1: Glycolysis
• The glucose is split into two molecules called
Pyruvates, or pyruvic acids (same thing)
• When glucose
(C
6
H
12
O
6
) products are made is split into 2 pyruvates some
▫ The glucose is oxidized by 2NAD + making 2NADH
▫ 4 ADP molecules are phosphorylated by the glucose to make 4 ATP molecules
 ADP and P are floating around the cell just waiting to be joined together
 Energy from the glucose is used to bond them together
without the ATP synthase complex
 This is called Substrate-Level Phosphorylation (SLP)

Step 1: Glycolysis
• The glucose is split into two molecules called
Pyruvates, or pyruvic acids (same thing)
• When glucose
(C
6
H
12
O
6
) is split into 2 pyruvates some products are made
▫ The glucose is oxidized by 2NAD + making 2NADH
▫ 4 ADP molecules are phosphorylated by the glucose to make 4 ATP molecules
• This breakup of glucose will also require some energy (ATP) to get started

Step 1: Glycolysis
• Although Glycolysis will produce 4 ATP, it also requires 2 ATP that will be used up
• This is why we say there is a net (overall/total) gain of 2 ATP from this step
-2ATP

cytoplasm
Step 1: Glycolysis
Carbon

Step 1: Glycolysis
• Remember the purpose is to release the energy stored in the glucose, so let’s see where it is now
▫ Some left with the e- and H + into 2NADH
 This will be used in the ETC to make more ATP
▫ Some left with the bonding of 2ADP and 2P into
2ATP
▫ The rest is still stored within the bonds of the 2 pyruvate molecules

Step 2: Pyruvate Oxidation
• The 2 pyruvate molecules go into mitochondria in order to be further broken down
• Sometimes this step is combined with the next step (Krebs Cycle) and you will see Cellular
Respiration described as a 3 step process
• We will consider it a separate step

Step 2: Pyruvate Oxidation
• The pyruvate is split into two molecules called acetyl CoA
• When pyruvates are split into Acetyl CoA, some products are made:
▫ The pyruvate is oxidized by NAD + to make NADH
 2 pyruvates = 2 NADH made
▫ A carbon (and oxygens) leave making CO
2
 2 pyruvates = 2 CO
2
▫ Coenzyme A attaches making the compound into
Acetyl CoA

Step 2: Pyruvate Oxidation cytoplasm

Step 2: Pyruvate Oxidation
• Remember the purpose is to release the energy stored in the glucose, so let’s see where it is now
▫ Some left with the e- and H + into 2NADH
 This will be used in the ETC to makes more ATP
▫ Some is still stored within the bonds of the 2CO
2
 Wasted energy
▫ The rest is still stored within the bonds of the 2
Acetyl CoA molecules
▫ No ATP is directly made at this step

Step 3: Krebs Cycle
• The Acetyl CoA enters the cycle and is completely broken apart
• When Acetyl CoA breaks down, some products are made:
▫ 6 NADH are produced (3 from each cycle)
 6 NAD + are reduced by gaining e- and H + from
Acetyl CoA
▫ 2 FADH
2 are produced (1 from each cycle)
 Also an e- carrier like NADH
 2 FAD are reduced by gaining e- and H + from Acetyl
CoA

Step 3: Krebs Cycle
• The Acetyl CoA enters the cycle and is completely broken apart
• When Acetyl CoA breaks down, some products are made
▫ 6 NADH are produced (3 from each cycle)
▫ 2 FADH
▫ 4 CO
2
 The Carbons and Oxygens are from the original glucose
2 are produced (1 from each cycle) are produced (2 from each cycle)
 The compound is unstable after losing the e- and H + so it also loses some C and O (chemistry magic)

Step 3: Krebs Cycle
• The Acetyl CoA enters the cycle and is completely broken apart
• When Acetyl CoA breaks down, some products are made
▫ 6 NADH are produced (3 from each cycle)
▫ 2 FADH
▫ 4 CO
2
2 are produced (1 from each cycle) are produced (2 from each cycle)
▫ 2 ATP are produced (1 from each cycle)
 Substrate-Level Phosphorylation
 The energy from breaking down Acetyl CoA is used to bond more free floating ADP and P together to form ATP.
 Again this happens without the use of the ATP Synthase
Complex

Step 3: Krebs Cycle
• The Acetyl CoA enters the cycle and is completely broken apart
• When Acetyl CoA breaks down, some products are made
▫ 6 NADH are produced (3 from each cycle)
 This will be used in the ETC to makes more ATP
▫ 2 FADH
▫ This will be used in the ETC to makes more ATP
 This will be used in the ETC to makes more ATP
▫ 4 CO
2
2 are produced (1 from each cycle) are produced (2 from each cycle)
 Wasted energy
▫ 2 ATP are produced (1 from each cycle)
• All of the glucose energy has been transferred into smaller chunks at this point

Pyruvate
Oxidation

Step 3: Krebs Cycle
• Remember the purpose is to release the energy stored in the glucose, so let’s see where it is now
▫ Some left with the e- and H + into 6NADH
▫ Some left with the e- and H + into 2 FADH
2
▫ Some left with the bonding of 2ADP and 2P into
2ATP
▫ Some is still stored in the bonds of the 4 CO2
• But we’ve only made 4 ATP total so far…not very many for 1 glucose molecule

Step 4: ETC
• The NADH and FADH2 bring the e- and H + to the Electron Transport Chain
• When e- go through the ETC, some products are made:
▫ 32 ATP
 Through chemiosmosis
 The electron carriers drop off the e- and H + , turning back into NAD + and FAD
 These now go back to the other 3 steps to pick up more e- and H + and keep the process going

Step 4: ETC
▫ 32 ATP
 Through chemiosmosis
 The electron carriers drop off the e- and H + , turning back into NAD + and FAD
 These now go back to the other 3 steps to pick up more e- and H + and keep the process going
 The e- go into the ETC and the H + are immediately sent to the intermembrane space
▫ Space between the inner and outer membrane
 The e- energy (originally from glucose) is used to pump more free floating H + into the intermembrane space creating a concentration gradient

Step 4: ETC
▫ 32 ATP
 Through chemiosmosis
 The electron carriers drop off the e- and H + , turning back into NAD + and FAD
 The e- go into the ETC and the H + are immediately sent to the intermembrane space
 The e- energy (originally from glucose) is used to pump more free floating H + into the intermembrane space creating a concentration gradient
 The H + diffuse into the matrix through the ATP
Synthase Complex
▫ Making 32 ATP per one molecule of glucose

Step 4: ETC
• The NADH and FADH2 bring the e- and H + to the Electron Transport Chain
• When e- go through the ETC, some products are made
▫ 32 ATP
▫ 6 water molecules
 After the e- lose all their energy in the ETC they join up with free floating H + and O
2 to make H
2
O
▫ The oxygen comes into the Mitochondria from the air you breathe

Step 4: ETC
• This is it! This is why you need Oxygen to live!
▫ The oxygen is required in your body so that it can act as a final electron acceptor at the end of the ETC and make water
 Without O
2 there to take the e-, the ETC can’t run
▫ It’s like you’re an electron waiting in line to get on the roller coaster at Disneyland (ETC) and the other people aren’t getting off of it.
▫ Even worse, more kids can’t even come stand in line because you
(and everyone else) is taking up all of the room at the roller coaster.
▫ So those other kids that want to be in line have to wait at their previous rides (Steps 2 and 3)
▫ And the whole thing shuts down from step 1
▫ And you run out of ATP (because there are no carriers taking the eto the ETC) and your cells die.

Animation

Aerobic Cellular Respiration
• Recap of the steps and their products (all you really need to know)
• Step 1 Glycolysis (cytoplasm)
▫ 2 NADH, 2 ATP
• Step 2 Pyruvate Oxidation (Mt matrix)
▫ 2 NADH, 2 CO
2
• Step 3 Krebs Cycle (Mt matrix)
▫ 6 NADH, 2 FADH
2
, 4 CO
2
, 2 ATP
• Step 4 ETC (inner Mt membrane)
▫ 32 ATP, 6 H
2
O

Aerobic Cellular Respiration
• How does this compare to our equation?

C
6
H
12
O
6
+ 6O
2
6CO
2
+ 6H
2
0+ ATP
• Step 1 Glycolysis (cytoplasm)
▫ 2 NADH, 2 ATP
• Step 2 Pyruvate Oxidation (Mt matrix)
▫ 2 NADH, 2 CO
2
• Step 3 Krebs Cycle (Mt matrix)
Why aren’t the electron carriers in the equation?
▫ 6 NADH, 2 FADH
2
, 4 CO
2
, 2 ATP
• Step 4 ETC (inner Mt membrane)
▫ 32 ATP
▫ 6 H
2
O

C
6
H
12
O
6
+ 6O
2
• Step 1 Glycolysis (cytoplasm)
▫ 2 NADH, 2 ATP
• Step 2 Pyruvate Oxidation (Mt matrix)
▫ 2 NADH, 2 CO
2
• Step 3 Krebs Cycle (Mt matrix)
▫ 6 NADH, 2 FADH
2
, 4 CO
2
, 2 ATP
• Step 4 ETC (inner Mt membrane)
▫ 32 ATP
▫ 6 H
2
O
6CO
2
+ 6H
2
0+ ATP
• The electron carriers are not final products in the reaction.
• They are just temporary products
• The NAD + changes back and forth from NADH
(ditto for
FADH
2
) as it gains electrons in one step and then loses them in another step. Then it goes back and gains them again in the first step. Its job is never finished.

Aerobic Cellular Respiration Review
Pyruvate
Oxidation
Krebs Cycle

Aerobic Cellular Respiration Review cytoplasm
Chemiosmosis

Aerobic Cellular Respiration Review
• Some good animations and videos for review:
• This video is great, but very detailed so there is some information you don’t need to know
(the different intermediary compounds formed in glycolysis and Krebs cycle)
• Crash course video – it goes into anaerobic cellular respiration a little too. It also talks about ATP use in the body

Anaerobic Cellular Respiration
• We already looked at what happens when our cells don’t get enough O at the ETC) shortage?
2
(they die because of the build up but what if there is a temporary
• Even under limited oxygen availability, cells will do Glycolysis
▫ Producing pyruvates, 2 ATP, and 2 NADH
 The pyruvates are poison to the cells 
 Yay ATP! 
 The NADH can’t be used in the ETC 

Anaerobic Cellular Respiration
• The poison pyruvates can’t stay there, so they undergo a process called fermentation.
• Many types of cells do fermentation so there are different kinds.
• Animal cells perform lactic acid fermentation
▫ This takes the pyruvate and NADH and turns them into lactic acid
 This does not give our cells extra energy

Anaerobic Cellular Respiration
• The poison pyruvates can’t stay there, so they undergo a process called fermentation.
• Many types of cells do fermentation so there are different kinds.
• Animal cells perform lactic acid fermentation
• Yeast (a fungus) and some bacteria do alcohol fermentation
▫ This takes the pyruvate and NADH and turns them into ethanol and CO
2
 This does not give cells extra energy but can be useful in other ways

Lactic Acid Fermentation
• The two steps of Lactic Acid Fermentation take place within the cytoplasm of the cell and produce very little ATP
▫ Glycolysis
 2 ATP
▫ Fermentation
 0 ATP
• Overall Anaerobic cellular respiration supplies our cells with very little energy (2 ATP) vs.
Aerobic cellular respiration (36 ATP).

Alcohol Fermentation
• The products of alcohol fermentation are much more useful to us than the lactic acid that our own cells make.
• We can use the ethanol part to make alcoholic beverages (fermentation of a plant product like grapes or corn, is how wine, beer, whisky, vodka, etc. are made).
• We can use the CO
2 part to make dough rise. That’s why yeast is added to bread; it ferments the sugar making alcohol and CO
2 makes it light and fluffy.
. The alcohol evaporates right away as its cooked and the CO
2

Fermentation
• Other everyday products are also the result of fermentation
▫ Yogurt (bacteria ferment milk)
▫ Cheese (different bacteria ferment milk)
▫ Pickles (fermented cucumbers)
▫ Chocolate (fermented cacao fruits)
▫ Vinegar (fermented wine)
▫ Sauerkraut (fermented cabbage)