1. Biology 102
Cellular respiration

2. Lecture Outline Glucose metabolism: Overview
Glycolysis: The first step in capturing energy in glucose
Cellular respiration: How additional energy is generated from glucose
Kreb’s cycle
Electron transport system

3. 1. Glucose metabolism: Overview
Why focus on glucose?
All cells do it!
Relatively simple
Most other compounds enter the glucose metabolism pathway when being broken down
Pathways go both ways
Example: fat from sugar

4. 1. Glucose metabolism: Overview
The formula! (You know this!)
The major reactions
Glycolysis
No oxygen needed
Generates 2 net ATP and 2 NADH per glucose molecule
3-C molecule, pyruvate, formed that enters other reactions depending upon presence/absence of O2
Cellular respiration
requires O2
Includes two parts
Kreb’s cycle
Electron transport

5. Location of different reactions
Glycolysis: cytoplasm of cell
Kreb’s cycle: matrix of mitochondrion
Electron transport: inner membrane of mitochondrion

6. 2. Glycolysis
Two steps
Activation (This gets the reaction over that activation energy hump! 2 ATP used.)
Energy harvest (4 ATP and 2 NADH produced)
Electrons and protons (H+) also “harvested”!
NET result: 2 ATP, 2 NADH and 2 pyruvate molecules (3-carbon chain) per glucose molecule

7. It is actually a bit more complicated, but you don’t need to memorize these details…

8. SIDE NOTE: G3P is the same high-energy 3-carbon compound that directly builds the glucose molecule in the Calvin-Benson cycle!

9. What happens to the pyruvate formed during glycolysis?
Used in fermentation (if oxygen absent)
Lactic acid (lactate) formed OR
Alcohol (ethanol) formed
In both cases, electrons and H+ from NADH are given to the pyruvate so NAD+ can be “recycled” and continue to carry out its function in glycolysis

10. What happens to the pyruvate formed during glycolysis?
Used in cellular respiration (if oxygen present)
Oxygen is the final acceptor for the electrons and H+ stripped from the glucose!
Water is formed!
Think back to photosynthesis, where water was the source for electrons and H+, and O2 was formed!

11. 3. Cellular respiration The net result:
LOTS of ATP generated (34-36 ATP)
CO2 is formed as C-C bonds are broken
Organic back to inorganic
Water is formed when oxygen serves as an electron (and H+) acceptor
Remember how it serves as a donor for these things in photosynthesis?

12. Focus: Kreb’s cycle Transition from Glycolysis Kreb’s cycle
Pyruvate transported to mitochondrial matrix
One CO2 breaks off
NADH formed
2-C molecule (acetyl Co A) enters..
Kreb’s cycle
Small amount of ATP generated
C-C bonds are broken, releasing 2 CO2
Electrons and H+ to NAD+ and FAD to form NADH and FADH2.
Remember that electrons carry their energy with them.

13. Focus: Electron transport/ chemiosmosis
NADH and FADH2 carry the electrons, H+ (and associated energy) to an electron transport system on the inner membrane of the mitochondria
Electron transport from high to low energy carriers is coupled to the synthesis of ATP
Creates and utilizes H+ gradients to do this.
Oxygen serves as the final electron and H+ acceptor, so that water is formed

14. Membrane proteins involved in electron transport
ATP synthesizing enzyme
H+ ion channel is key part…
Electron transport system
Series of specific proteins imbedded in membrane

15. Electron transport
Electrons from NADH and FADH2 deposit electrons to the system
Electrons move from high to low energy compounds
The energy released is used to transport H+ ions from the matrix to the intermembrane compartment

16. Formation of ATP
The H+ gradient drives the production of ATP

17. Summary: Energy harvested from glucose