Cellular Respiration

Cellular respiration is the controlled release of energy from organic

compounds (lipids, carbohydrates and proteins) in cells to produce ATP.

OBJECTIVES

Define ‘Cellular Respiration. State that, in cell respiration, glucose in the

cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP.

Explain that, during anaerobic cell respiration, pyruvate

be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP. 3.7.4 Explain that, during aerobic cell respiration,

pyruvate can be broken down in the mitochondrion into carbon dioxide & water with a large yield of ATP.

SOME GUIDING PRINCIPLES

The Laws of Thermodynamics

First Law: Energy can be converted from one form to another, but it cannot be created nor destroyed.

Second Law: Energy cannot be converted from one form to another without some loss of usable energy.

Energy is the ability to do work.

Cellular Respiration (The Basics)

Cellular respiration is the controlled release of energy from organic compounds (lipids,

carbohydrates and protein) in cells to form ATP.

Occurs in ALL ORGANISMS (even those organisms like prokaryotes w/out mitochondria) because all living cells need a continual supply of energy.

Cellular respiration is considered a catabolic reaction and involves a series of very complex metabolic reactions involving numerous enzymes.

ATP: THE UNIT OF CELLULAR ENERGY

ATP (adenosine triphosphate) releases energy when the bond between the 2nd and 3rd phosphate group is broken, forming a molecule called adenosine diphosphate (ADP) and a free phosphate group.

Cellular Respiration Involves a Transformation of Energy.

The Balanced Equation for Cellular Respiration

Can You Interpret the Equation?

Organisms obtain energy in this process.

Cellular Respiration and Breathing (Respiration)

Cellular Respiration occurs at the cellular level and is NOT the same thing as

breathing.Cellular Respiration occurs at the cellular

level (cytoplasm and mitochondrion in eukaryotes) and inner cell membrane (prokaryotes).

Breathing delivers a reactant (oxygen gas) for cell respiration and removes a waste product (carbon dioxide).

Where Does Cellular Respiration Occur?

In prokaryotes, however, cellRespiration occurs in the folds of theCell membrane.

Cellular Respiration Occurs in 2 Steps: Glycolysis and Aerobic Respiration

In aerobic cell respiration, approx.36-38 ATP are produced per glucoseMolecule.

Glycolysis (The 1st Step)

Glucose is often, but not always, the organic compound used in cell respiration. Chemical reactions in the cytoplasm break down glucose into a simpler organic compound called pyruvate. A small amount of ATP is released.

NET YIELD

2 Molecules of ATP are formed (net gain).

2 Molecules of NADH are formed.

2 Pyruvate Molecules

THE KREBS CYCLE (2nd STEP)

If oxygen is available, the two pyruvate molecules enter the mitochondrion (matrix). Most of the energy from glucose is still contained in pyruvate at this point.

Net Yield 6CO2 molecules 2 ATP molecules 8 NADH molecules 2 FADH2 molecules

THE ELECTRON TRANSPORT CHAIN

The final step in the breakdown of glucose. Oxygen is the terminal electron acceptor.Occurs in the inner membrane folds

(cristae)A large amount of ATP (36-38 ATP

molecules) is produced from one glucose molecule.

The Electron Transport Chain

Anaerobic Cell Respiration

If no oxygen is available, the pyruvate remains in the cytoplasm and is converted into a waste product that can be removed from the cell. No ATP is produced in these reaction. In humans, the waste product lactate (lactic acid) is produced. In yeast, the products are ethanol (alcohol) and carbon dioxide.

SUMMARY