Chapter 9 (Pages )

The Powerhouse

Copyright Pearson Prentice Hall Overview of Cellular Respiration Cytoplasm Pyruvic acid Mitochondrion Electrons carried in NADH Electrons carried in NADH and FADH 2 Glucose Glycolysis

The equation… OMG! It’s flipped!

2 NAD+ glucose C CC C CCCC CCCC P P P P 2 ADP 4 ADP 2 ATP 4 ATP 2 NADH PYRUVATE (pyruvic acid)

 Krebs Cycle (Citric Acid Cycle) Glycolysis Without O 2 Fermentation ETC (Where most ATP is made) With O 2 Two options – all depends on presence O2!

 Anaerobic – follows Glycolysis when oxygen is not present  Not how the normal process of CR is supposed to go! Back-up plan!  Fermentation releases energy from food molecules by producing ATP in absence of O2  The electrons stored in NADH are returned to Pyruvic Acid, letting the NAD+ go back to glycolysis and keep making ATP Alcoholic fermentation Lactic acid fermentation

 Used by yeasts, bacteria  why bread rises  Converts sugar into ethyl alcohol and CO 2

 In many cells, the pyruvic acid that accumulates from glycolysis can be converted into lactic acid  Produced in your body during rapid exercise  Causes muscle soreness

 The equation for lactic acid fermentation after glycolysis is: Pyruvic acid + NADH → lactic acid + NAD +

 In the presence of oxygen, cellular respiration proceeds from glycolysis to the Krebs Cycle  Breaks down pyruvic acid into carbon dioxide  Occurs in mitochondri al matrix

 Discovered in 1937 by Hans Krebs - biochemist  The basic definition of Krebs Cycle: The breaking down of pyruvic acid into CO2 in a series of energy- extracting reactions

Before the cycle starts “turning”  Step 1  pyruvic acid enters the mitochondria  Step 2  one carbon molecule from pyruvic acid breaks off to form CO2  Step 3  other two carbon atoms tack onto coenzyme A – this molecule becomes acetyl coenzyme A  Step 4  Acetyl CoA adds the two carbon acetyl group to a 4 carbon molecule… THIS 6 CARBON MOLECULE IS CITRIC ACID!

 Step 1  citric acid loses a carbon That carbon becomes a CO2 molecule NAD+ picks up 2 electrons and H+

 Step 2  the 5- carbon molecule loses a carbon That carbon becomes a CO2 molecule NAD+ picks up 2 electrons and a H+ ATP formed (only 1)

 Step 3  the 4- carbon molecule is ready to start the cycle again! FAD picks up 4 electrons and 2 H+ NAD picks up one last set of electrons and H+

One turn of the Krebs Cycle gives you these products:

 The ETC uses high-energy electrons from the Krebs cycle to convert ADP into ATP  In eukaryotes, the ETC is a series of carrier proteins located in the inner membrane of the mitochondria  In prokaryotes, the ETC is in the cell membrane

 2 high energy electrons are transported through the ETC  Their energy helps transport H+ through the membrane

 At the end of the ETC an enzyme (named Complex IV) is waiting patiently to snatch up the electrons and a couple H+  The enzyme combines the electrons, H+, and O2   H+ escape to intermembrane space THEY BUILDIN UP OVER THERE!!!!!

 H+ builds up in the intermembrane space, making it positively charged  The H+ rush back to the negative membrane side  As they pass, they cause ATP synthase to spin and make ATP

 In the presence of oxygen – 36 total ATP molecules produced 38% of the total energy of glucose What happened to the remaining 62%?  What can stop this process? Carbon monoxide disables Complex IV Electron carriers are not recycled Cellular respiration cannot continue ATP Synthase not as efficient Your body turns to fermentation

 When you need quick energy, how does your body produce it? Lactic Acid Fermentation Quick and easy  When you need long term energy (longer than 90 seconds), where do you retrieve the ATP? Cellular Respiration Slowwwwwww, but higher amounts ○ Not really, it happens a ton of times every second. Muscle stores (carbohydrates), fats