Biology Chap 9

Chapter 9- Cellular Respiration & Metabolism

Life is Work!
Living Cells- we all require transfusion of energy from the outside
For us- it comes from food
Plant Friends- sun (light)
Most ecosystems- flows in as sunlight & out as heat
Panda- obtains energy from eating plants
Catabolic Pathways
Yield energy by oxidizing food
Exergonic reaction- gives up energy
Ex. Cellular Respiration
Most efficient
Take in food, break it down, yields energy
Yield energy by transferring electrons
Redox Reaction
Oxidation
More positive than it was at the start
Gives up electrons
OIL- oxidation is loss
Reduction
Substance gains electrons, or is reduced
End more negative
RIG- Reduction is gaining
This results in a more stable arrangement of electrons
Electrons are transferred to more electronegative atoms
***Some redox reactions do not completely exchange electrons***
Figure 9.3
Cellular Respiration
Glucose is oxidized and oxygen is reduced
Respiration happens in steps
Glucose is oxidized in a bunch of steps
Electrons from organic compounds-are usually transferred to NAD+, a coenzyme
NAD+ is reduced to NADH (add H take away plus sign)
NAD carries the electrons to the electron transport chain uses energy from the ETC to make ATP
Steps of Cellular Respiration
Glycolysis
Breaks down glucose
6-carbon sugar into 2 molecules of pyruvate (3 carbon compound) & releases 2 ATP
The Citric Acid Cycle (Krebs Cycle)
Completes the breakdown of glucose
Oxidative Phosphorylation
Driven by the ETC
All electrons from glycolysis and CAC get dumped onto ETC and help generate of ATP
Figure 9.6-commit to memory
Substrate-Level Phosphorylation
Glycolysis & Citric Acid Cycle
Substrate with Phosphate on it, and ADP go into the enzyme and releases product and ATP releases one at a time
Glycolysis
Splitting of sugar
2 ATP & 2 Pyruvates in the cytoplasm
2 phases
Investment
Use two ATP
Phosphofructokinase
Kinase  think phosphorylation
Get G3P out of this phase
Payoff
Substrate Level Phosphorylation
Taking a P off of the molecule & make 2 ATP
2NADH, 2H+, 4ATP,
Give a little to get more
Krebs’s Cycle
Inside the mitochondrial martix
Main function of CAC is to complete the breakdown of glucose
Mitochondria
Outer membrane
Inner Membrane
Cristae (folds)
Matrix is inside of the fold
Must get pyruvate from cytoplasm into the matrix (through2 sets of membrane)
This happens thru active transport
When it is brought in, one carbon is cut off and it brings in a two carbon compound
Take some electrons by using NAD
CoA is attached to Carbon group, and makes Acetyl CoA
The remained two carbon are oxidized to two CO2 molecules, further oxidize them by using NAD
Now we make ATP by phosphorylation
FAD also picks up electrons, but takes in lower energy electrons
Every time this cycle goes around
3 NADH
1 FADH2
1ATP
2 CO2
All the glucose ha been transferred to NADH & FADH2
Electron Transport Chain
The electrons are then donated from NADH, FADH2 to electron transport chain
Oxygen is the final goal
First Complex (Step)
NADH drops its high energy electrons
FADH drops its electrons off a little farther down the chain
The electrons fall from one purple bead to the next, & in each step we utilize a little bit of energy and eventually end up with oxygen
The transfer of electrons causes the complexes to pump H+ from the matrix to the intermembrane space thru active transport
This results in a H+ gradient, which means its higher in the intermembrane space than the matrix
H+ in the intermembrane are stored energy
This is referred to as Proton-Motive Force
The difference between intermembrane space & matrix, and this drives ATP synthesis
Chemiosmosis- doesn’t move water, it moves H+
Energy coupling mechanism that uses energy in the form of a H+ gradient
The lake of hydrogen ions flow through the ATP funnel
It has moving parts
H+ ions come down and bind to the rotor, which causes the sub unit to change its shape, and causes it to turn one unit & so on and so forth causing it to spin and release the H+ ions to release on the other side
Transfers a phosphate to ADP, creating ATP
How fast does it move?  100/s
2.7 protons to make 1 ATP
GlucoseNADHETCProton-Motive ForceATP
Use 40% of the energy found in the glucose molecule
Fermentation
Catabolic Process
Make some ATP without oxygen
Glycolysis can make ATP w/ or w/o Oxygen
Couple glycolysis with fermentation to regenerate NAD+
Alcoholic Fermentation
Take pyruvate and make it ethanol
Pyruvate  Acetylaldehyde w release of CO2 Ethanol w release of NAD+
Only get 2 ATP, so not efficient
Lactic Acid Fermentation
Pyruvate is reduced directly to form lactate as a waste product
Pyruvateintermediate compoundLactate w release of NAD+
How Does it Work?
Both use glycolysis to oxidate glucose
Cellular Respiration & Fermentation
Both use pyruvate
Lots o f other pathways connect into glycolysis and CAC to catabolize many different types of food molecules
Figure 9.19
All end up in Oxidative phosphorylation
How do we control respiration?
Phosphofructokinase
This enzyme is key to controlling cellular respiration
Inhibited by high levels of ADP causes the cycle to back off a little
Review Slides & Study Guide