cellular respiration. cellular respiration – process in which mitochondria break down food...

Cellular Respiration

Cellular respiration – process in which mitochondria break down food molecules to produce ATP in plants & animals; occurs in the presence of oxygen

Nutrients + oxygen water+ ATP+ CO2

The equation for cellular respiration is:6O2 + C6H12O6 → 6CO2 + 6H2O + Energyoxygen + glucose → carbon dioxide + water +

energy

Process changes organic chemical energy (glucose) into inorganic chemical energy ATP

Overview of Cellular Respiration3 Stages:1. Glycolysis – anaerobic process; does not

require oxygen - cytoplasm2. Citric Acid (Krebs) Cycle – aerobic;

does require oxygen – mitochondria3. Electron Transport Chain – aerobic;

does require oxygen - mitochondria

GlycolysisGlycolysis – breaks down glucose into two

molecules of pyruvic acid (colorless acid)This reaction uses enzymes and takes place in

the cytoplasm of the cell (anaerobic reaction)Produces:- 2 Pyruvic acid molecules (used in Step 2 of

cellular respiration)- 2 ATP molecules (energy cell can use)- 2 NADH molecules (electron carrier)

2 ATP2 ADP

4 ADP 4 ATP

2 Pyruvicacid

At the beginning of glycolysis, the cell uses up 2 molecules of ATP to start the reaction.

2 ATP

2NAD+2

To the electrontransport chain

FermentationFermentation releases energy from food

molecules by producing ATP in the absence of oxygen; anaerobic process

During fermentation, cells convert NADH to NAD+ by passing high-energy electrons back to pyruvic acid.

This action converts NADH back into NAD+, and allows glycolysis to continue producing a steady supply of ATP.

2 Types of Fermentation1. Lactic acid fermentation – process that

supplies energy when O2 is scarceEx.) released during vigorous exercise; “feel the

burn”

2. Alcoholic fermentation – used to produce CO2 and ethyl alcoholEx.) Yeast Cells

The Krebs CycleNamed after Hans Krebs – British biochemist;

won Nobel Prize in 1953 for discovery of this cycle

Aerobic processPyruvic acid produced from glycolysis along

w/O2 start the 2nd stage of cellular respiration

Pyruvic acid is broken down into CO2 in a series of endergonic reactions

2 Parts of the Krebs Cycle

Part A Step 1: Cycle begins when pyruvic acid enters

the mitochondrion

The Krebs Cycle

2. Carbon molecule is removed, forming CO2, & electrons are removed, changing NAD+ to NADH.

3. Coenzyme A joins the 2-carbon molecule, forming acetyl-CoA.

The Krebs Cycle

Citric acid

4. Acetyl-CoA then adds the 2-carbon acetyl group to a 4-carbon compound, forming citric acid.

The Krebs Cycle

Part BStep 1: Citric acid is broken down into a 5-carbon compound,

then into a 4-carbon compound.

The Krebs Cycle

Step 2: Two more molecules of CO2 are released and electrons join NAD+ and FAD, forming NADH and FADH2.

The Krebs Cycle

Result: 1 molecule of ATP is produced

Energy totals from 1 molecule of pyruvic acid is : 4 NADH 1 FADH2

1 ATP

Electron Transport Chain = 3rd step in cellular respiration, aerobic process, uses the high-energy electron carriers from the Krebs Cycle to convert ADP into ATP.

Carrier molecules produced are used to generate ATP via the Electron Transport Chain

Electron Transport Chain High-energy electrons from NADH and FADH2 are passed

along the electron transport chain from one carrier protein to the next.

The Totals Glycolysis produces just 2 ATP

molecules per molecule of glucose. The complete breakdown of glucose

through cellular respiration, including glycolysis, results in the production of 36 molecules of ATP.

The Totals: Overview

Comparing Photosynthesis and Cellular Respiration Comparing Photosynthesis and Cellular

Respiration The energy flows in photosynthesis and cellular respiration

take place in opposite directions.

On a global level, photosynthesis and cellular respiration are also opposites.

•Photosynthesis removes carbon dioxide from the atmosphere and cellular respiration puts it back.•Photosynthesis releases oxygen into the atmosphere and cellular respiration uses that oxygen to release energy from food.