Chap 9.Cell Respiration

Why is cell respiration

so necessary? Living cells need a constant

supply of energy

• Examples: heart cells beating,muscle cells contracting, cells being made and repaired, etc.

• Organisms take food & break it down

into glucose (mostly in the small intestine)• cell respiration – process of

breaking down glucose in the presence of O2 to release energy

- Done by eukaryotes!

Equation for Cell Resp.

6O2 + C6H12O6 → 6CO2 + 6H2O + energy

• The energy that isreleased is usedto make ATP

How Does It Happen?

• Glucose – simple sugar (C6H12O6) • Glucose is present in food• Food is broken down by our digestive

systems • The chemical bonds in food are broken & the

energy is released (Exergonic!)• 2 major types of organisms getting energy:

1. aerobic respiration. – with O2

2. anaerobic fermentation – without O2

Review of

ATP-ADP Cycle

Cell Respiration

• Step 1 – Glycolysis: Takes place in Cytoplasm• A. Process of 1 molecule of glucose broken in

half • B. Two 3-carbon compounds produced; each

called pyruvic acid• C. 4 ATP molecules are produced• D. 2 ATP molecules are used for the reaction

to occur• E. Net gain of ATP molecules = 2

Glycolysis – Cont.

• Each electron carrier (NAD+ or uncharged battery) accepts high- energy electrons from H & carries them to the next reaction

• NADH is now the charged battery

Review of Glycolysis

Glycolysis • Converts 1 glucose (C6) to 2 pyruvic acids (C3)• Produces :  

2 pyruvic acids 2 NADH

 2 ATP (net)• Occurs in

cytoplasm  [anaerobic] –all organisms do glycolosis

  

Aerobic Respiration Needs Mitochondria!

• The Krebs Cycle and Electron Transport chain take place here!

Cell RespirationAEROBIC!

• Step 2 – Krebs Cycle (Citric Acid Cycle)• A. Pyruvic acid is broken down in a series of

reactions• B. Also called the citric acid cycle b/c citric

acid is the 1st compound produced

• C. CO2, 8NADH, 2FADH2 & 2 ATPs are produced

• Takes place in the mitochondria matrix• The matrix is inside the inner membrane• http://highered.mheducation.com/sites/0072507470/student_view0/

chapter25/animation__how_the_krebs_cycle_works__quiz_1_.html

Cell RespirationAEROBIC!

• Step 3 – Electron Transport Chain• Takes place in the mitochondria inner

membrane• Uses high-energy electrons carried from

NADH + FADH2 in the Krebs Cycle• The ETC produces 32 ATP molecules,

H2O, and un-charges electron carriers

Electron Transport Chain (ETC)

- Uses high-energy electrons from the Krebs cycle to convert ADP into ATP.

- Occurs along the inner membrane of the mitochondria.

- The electrons from NADH & FADH2 are passed along a series of proteins.

- This movement of electrons pumps H+ ions into the inner membrane space.

- The H+ ions will move from high to low concentration through the enzyme

ATP Synthase.

- This movement causes the enzyme to move like a turbine and bind ADP to P forming ATP.

http://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::Electron%20Transport%20System%20and%20ATP%20Synthesis

Why does it need oxygen?

Oxygen is the final electron acceptor!

Electron Transport Chain

Electron Transport Chain• Where are the electrons moving?__________________• Where are the H+ ions in a high concentration?_______• When the electrons are finished going through the chain,

what is the final electron acceptor?________, with H+ ions, it turns into ________.

• The enzyme that make ATP is _________________.

Totals of Aerobic Respiration- With aerobic respiration, a total of 36 ATPs are produced per glucose.

Comparing Photo & Cell Respiration

Photosynthesis Cell Respiration

Energy goes in and is stored

Energy comes out

Occurs in chloroplasts Occurs in mitochondria

Raw materials – CO2 & H2O

Raw materials – glucose & O2

Products – glucose & O2 Products – ATP, CO2 & H2O

Review of Glycolysis

Glycolysis • Converts 1 glucose (C6) to 2 pyruvic acids (C3)• Produces :  

2 pyruvic acids 2 NADH

 2 ATP (net)• Occurs in

cytoplasm  [anaerobic]  

Cell Respiration

When O2 is not present gylcolysis is followed by a different path

• A. Fermentation The release of energy from food in the absence of O2 – It allows the cells to continue glycolysis because it frees up NAD+

(NADH -> NAD+)

• B. Two types: • C. alcoholic fermentation• D. lactic acid fermentation

Types of Fermentation

1. Alcoholic Fermentation

• A. NADH is converted back to NAD+ and energy

• B. Occurs in yeast cells; used in baking bread (CO2 makes bread rise) & in making alcohol

• equation:

pyruvic acid + NADH → alcohol + CO2 + NAD+

Types of Fermentation

2. Lactic Acid Fermentation – • A.Occurs in muscle cells when they

run out of O2

• B.Causes pain & soreness

• equation: • pyruvic acid + NADH → lactic acid +NAD+

Also occurs in bacteria cells, we use it to make yogurt, sauerkraut, and kimchi

One more thing!

• The only way to get rid of your lactic acid after a hard workout is through a pathway that requires extra oxygen.

• That is why you breathe heavy after working out – to repay the oxygen debt.