CELLULAR RESPIRATION

Photosynthesis: REVIEW Previously, we learned that photosynthesis takes place in the chloroplasts In the ‘light reactions’, solar energy is captured by photosystems on the thylakoid membrane and used to attach phosphate groups to energy-carrying molecules like ATP.

This completes the equation for photosynthesis: Photosynthesis: REVIEW This completes the equation for photosynthesis: 6 CO2 + 6 H20 C6H12O6 + 6 O2 In the CALVIN CYCLE, the ATP and NADPH made in the light reactions are used to power the assembly of sugars in the stroma, the fluid-filled interior of the chloroplasts.

Photosynthesis: REVIEW This completes the equation for photosynthesis: 6 CO2 + 6 H20 C6H12O6 + 6 O2 So now we have energy stored in the form of sugars. Very nice, but what if plants (or, for that matter, people) want to release that energy? THEY MUST USE A DIFFERENT PATH…..!

CELLULAR RESPIRATION ! Next, we’ll need another organelle to do these FIRST, WE REVERSE THE EQUATION: 6 CO2 + 6 H20 C6H12O6 + 6 O2 Next, we’ll need another organelle to do these reactions in! Not chloroplasts this time, but instead another organelle with its own DNA….

Mitochondria:

Mitochondria:

Mitochondria: have complex folded inner membranes (cristae), increasing their surface area

Mitochondria: have complex folded inner membranes (cristae), increasing their surface area have a fluid-filled interior (the matrix)

Mitochondria: have complex folded inner membranes (cristae), increasing their surface area have a fluid-filled interior (the matrix) act like combustion chambers in an engine, a ‘safe’ place to ‘burn’ fuel with oxygen

A Combustion Chamber?

A Combustion Chamber? LET’S COMPARE! A gasoline engine . . . . and a mitochondria, in cross-section.

Before combustion can occur, however, we have to get some “fuel” !

For that, we will need to break down glucose (or other sugars) OUTSIDE the mitochondria, in a process called . . . .

G L Y C O L Y S I S

G L Y C O L Y S I S:

G L Y C O L Y S I S: is the breakdown of glucose (or other sugars)

G L Y C O L Y S I S: is the breakdown of glucose (or other sugars) requires an activation energy

G L Y C O L Y S I S: is the breakdown of glucose (or other sugars) requires an activation energy occurs in the cytoplasm

Polymers of glucose, like starch, are first broken into individual sugars through hydrolysis

The single sugars produced contain stored energy in their chemical bonds, but they are still too big to pass through the mitochondrial membrane.

ATP provides the initial activation energy. The 6-carbon sugar will be broken down in a series of steps that do not involve oxygen.

C3H3O3 There will be a net gain of 2 ATP. The final products of glycolysis are two 3-carbon molecules of pyruvate (pyruvic acid)

C3H3O3 Pyruvate is small enough to be easily transported through the mitochondrial membrane, where a new series of chemical reactions take place. . .

The Krebs Cycle

The Krebs Cycle: takes place in the matrix

The Krebs Cycle: C3H3O3 takes place in the matrix “acetyl CoA” begins by converting each of the 3-carbon pyruvates into a special complex called acetyl CoA . . Co-enzyme A is added C3H3O3 “acetyl CoA” Pyruvate enters the matrix. . . . . .a waste product , CO2 , is released . . .

The Krebs Cycle: Acetyl CoA begins the cycle Acetyl CoA

As the cycle proceeds, CO2 The Krebs Cycle: Acetyl CoA begins the cycle As the cycle proceeds, CO2 are removed CO2 CO2

. . .an electron transport chain is charged! The Krebs Cycle: There is a net gain in ATP, and . . . . . .an electron transport chain is charged! e- CO2 e- CO2 ATP

Electron Transport: takes place in the cristae

Electron Transport: takes place in the cristae

Electron Transport: Electron Transport: takes place in the cristae will draw in H+, creating a high concentration which can be used to drive a proton pump

Proton Pumping: powers the enzyme, ATP synthase

Proton Pumping: powers the enzyme, ATP synthase …which is then used to make ATP

DOING THE MATH: Glycolysis, in cytoplasm, no O2 4 ATP

DOING THE MATH: Glycolysis, in cytoplasm, no O2 4 ATP Krebs Cycle, in matrix, no O2 2 ATP

DOING THE MATH: Glycolysis, in cytoplasm, no O2 4 ATP Krebs Cycle, in matrix, no O2 2 ATP Electron transport chains, with O2 32 ATP

DOING THE MATH: Glycolysis, in cytoplasm, no O2 4 ATP Krebs Cycle, in matrix, no O2 2 ATP Electron transport chains, with O2 32 ATP TOTAL: 38 ATP

DOING THE MATH: Glycolysis, in cytoplasm, no O2 4 ATP* Krebs Cycle, in matrix, no O2 2 ATP Electron transport chains, with O2 32 ATP TOTAL: 38 ATP (-2 ATP)* --------------- (*minus 2 ATP used for activation energy in glycolysis)

DOING THE MATH: Glycolysis, in cytoplasm, no O2 4 ATP* Krebs Cycle, in matrix, no O2 2 ATP Electron transport chains, with O2 32 ATP TOTAL: 38 ATP (-2 ATP)* --------------- NET YIELD, 1 glucose: 36 net ATP (*minus 2 ATP used for activation energy in glycolysis)