Bi 102 (Winter 2008) Harvesting Energy: Glycolysis and Cellular Respiration Dr. Dutton

Chapter 8

I. How is Glucose metabolized?

Our bodies metabolize a variety of organic molecules

We’ll focus on ____________________ because:

1. All cells use glucose at least sometimes

2. Glucose metabolism is less complex

3. Other molecules may use the glucose metabolism pathway »

Figure E8-4

The reaction:

C₆H₁₂O₆ + 6O₂ --> 6CO₂ + 6H₂O + Chemical & Heat Energy

Is essentially symmetrical with Photosynthesis reaction:

6CO₂ + 6H₂O + Light Energy --> C₆H₁₂O₆ + 6O₂

Is the conversion of Light Energy to Chemical Energy completely efficient?

The reaction:

C₆H₁₂O₆ + 6O₂ --> 6CO₂ + 6H₂O + Chemical & Heat Energy

Heat Energy

II. How is the energy in glucose captured during glycolysis?

____________________ = “ to break apart a sweet”

Used by every living creature on the planet

Occurs in Cytoplasm

Two Steps:

A) Glucose Activation

Requires a small bit of Energy:

B) Energy Harvest:

(Glycolysis produces a small amount of Energy)

Glycolysis = “ to break apart a sweet”

Used by every living creature on the planet

Occurs in Cytoplasm

Two Steps:

What happens next??

Depends on whether there are Aerobic or Anaerobic conditions

1) Anaerobic Conditions à ____________________

• Microorganisms thrive without oxygen

• Deep in soil sediments and oceans

• Our muscles sometimes also go “anaerobic”

2) Aerobic Conditionsà ____________________ ____________________

• Use Pyruvate and NADH to generate lots more ATP

III. How does Cellular Respiration capture additional energy from glucose

• Under aerobic conditions only

• Series of enzyme catalyzed reactions

• Occur in mitochondria

Figure 8.6

1) Each pyruvate transported into matrix

2) Split into CO2 and Acetyl

• Acetyl+ coenzyme A= acetyl CoA

3) Enters Krebs cycle

• Produces (per original pyruvate):

• 2 CO2

• 1 ATP

• 3 NADH & 1 FADH2} Electron Carriers

4) “energized” electron carriers go to Electron Transport System

• in inner membrane

5) Use ____________________ to make ATP

• Energy of electrons is used to create H+ gradient

• same process as in photosynthesis

6) ATP transported out to cytoplasm

Figure 8.8

A closer look at Fermentation - in Anaerobic conditions

Releases much less energy: tiny fraction of potential energy in Glucose

• Only ATP generated is in glycolysis step.

• NADH is not used for energy capture

• used to transfer H+ and e- (byproducts) from glycolysis

• fermentation simply keeps glycolysis running

Lactate (lactic acid) is produced during strenuous exercise

• when body has insufficient oxygen

• can only convert glucose to 2 ATP , and eventually lactate

b) Some cells ferment pyruvate to ethanol and CO2

(also in the cytoplasm)

Used to keep glycolysis running