Cellular Respiration → breaking down food (chemical energy) to get ATP

CH 9 – Cellular Respiration

MITOCHONDRIA

Intermembrane Space

• Powerhouse of the cell!• The organelle responsible for cellular respiration

• The Krebs Cycle and ETC take place here ATP is produced here!

• It is a double membrane with the inner membrane highly folded (to increase the surface area and make the mitochondria more efficient).

CELLULAR RESPIRATION – BACKGROUND INFO

Equation – C6H12O6  +  6O2  →  6CO2  +  6 H2O  + 

36 or 38 ATP-When food is broken down, energy is released gradually and stored in ATP.

-Respiration is done by BOTH plants and animals

GENERAL OVERVIEW – CELLULAR RESPIRATIONGlycolysis:• In the cytosol• Anaerobic• Turns glucose to 2 pyruvate net gain of 2 ATP and 2 NADH

Krebs:• In the mitochondrial matrix • Makes little ATP, NADH, and FADH2 (electron taxis) • Passes e- to ETC

ETC → uses chemiosmosis to make LOTS of ATP

GLYCOLYSISMain Goal of Glycolysis is to turn glucose into two pyruvate: - Series of 10 steps - Produces a net gain of 2 ATP and 2 NADH (e- carriers) - From here it can go to the Krebs cycle (aerobic respiration) or to Fermentation (anaerobic) - Glycolysis is anaerobic - Occurs in the cytosol

Overall: Glucose → 2 Pyruvate; net gain 2 ATP and 2 NADH

INTERMEDIATE STEP

Pyruvate (made in the cytosol via glycolysis) diffuses into the mitochondria. As it diffuses is, it loses a carbon (goes from 3C to 2C) when it produces one molecule of CO2. This new 2C molecule is acetyl CoA. Acetyl CoA is what goes into the Krebs cycle.

KREBS/ CITRIC ACID CYCLEMain Function of the Krebs → to make electron carriers (NADH and FADH2) to send to the ETC Series of 8 steps; Occurs in the mitochondrial matrixSo…1 glucose produces:

2 ATP6 NADH2 FADH2

(remember: 1 glucose = 2 pyruvates)Acetyl CoA (2C) enters the Krebs and combines with another molecule (4C) to form citric acid (hence citric acid cycle)

Electron Carriers

Krebs →Makes 1 ATP, 3 NADH, and 1 FADH2 per turnYou do NOT need to memorize this!

ELECTRON TRANSPORT CHAIN (ETC)Occurs on the inner membrane of the mitochondria; Energy from NADH and FADH2 power ATP synthesisThe ETC is a series of proteins throughout the membrane; the electrons lose energy every time they get passed down the chainOXYGEN IS THE FINAL ELECTRON ACCEPTOR!!! → oxygen combines with the electrons and H+ to make WATER

Main Goal of the ETC → it’s a stepwise free energy drop from food to oxygen; it creates a proton gradient that powers chemiosmosis to create ATP via ATP Synthase

The ETC uses energy from the electrons and pumps the protons OUT of the matrix into the intermembrane space; it then diffuses back in via ATP synthase.

-NADH and FADH2 drop off e- to the ETC-As the e- get passed down the chain, they lose energy; that energy is used to pump H+ OUT of the matrix into the intermembrane space-This creates a concentration gradient-The protons then diffuse back INTO the matrix via the ATP synthase (chemiosmosis); this creates ATP -Makes a TON of ATP!!!

Final e- acceptor after they go down the ETC is OXYGEN (from the atmosphere) …it combines with e- and H+ to make WATER

CELLULAR RESPIRATION OVERVIEW

ATP Summary →Glycolysis – 2Krebs – 2ETC – 32/34

CELLULAR RESPIRATION VS. FERMENTATION

Oxygen Present → Aerobic Respiration (efficient!)

Oxygen NOT Present → Fermentation (not efficient)Respiration = 66%

efficientFermentation = 3.5% efficient

FERMENTATION If there is no oxygen present

(anaerobic) the pyruvate (from glycolysis) goes to fermentation

The main goal of fermentation is to make NAD+ to put back into glycolysis; it makes NO ATP on its own (it just keeps glycolysis going so that it can make 2 ATP at a time)

Occurs in cytosol 2 types of fermentation: alcohol

and lactic acid

- Pyruvate is turned into ethanol- CO2 is released (bubbles!)- Done by yeast for brewing

3C Pyruvate → 2C Ethanol

Remember: Goal is to produce NAD+ to send back to glycolysis so it can keep going and produce more ATP

Alcoholic Fermentation

LACTIC ACID FERMENTATION

- Pyruvate is turned into Lactate (or lactic acid)- Lactate is eventually

carried away by the blood to the liver where it gets converted back into pyruvate

- Example: Muscle Cells!!

- The lactic acid is what makes your muscles sore after lifting or intensive exercise- No CO2 is released3C Pyruvate → 3C

Lactate

Remember: Goal is to produce NAD+ to send back to glycolysis so it can keep going and produce more ATP

LACTIC ACID VS. ALCOHOL

FERMENTATION Both start with pyruvate from glycolysis

Alcohol makes ethanol and gives off CO2

Lactic acid makes Lactic acid and does NOT give off CO2

Both create NAD+ to be sent back to glycolysis

Neither make any ATP on their own

FERMENTATION - OVERVIEW Obligate Aerobes → needs oxygen; can do respiration only

Obligate Anaerobes → can’t have oxygen; fermentation only

Facultative Anaerobes → can live with or without oxygen; prefer oxygen b/c more efficient

Respiration is 19 times more efficient than fermentation (38 ATP vs. 2 ATP)