Cellular RespirationCellular RespirationMrs. Schenfield’sMrs. Schenfield’s

Life ScienceLife Science

Cellular Respiration Overview

Transformation of chemical energy in food into chemical energy cells can use: ATP

These reactions proceed the same way in plants and animals. Process is called cellular respiration

Overall Reaction:– C6H12O6 + 6O2 → 6CO2 + 6H2O

Anaerobes Anaerobes are organisms that

use the Anaerobic Respiration pathway

Most anaerobes are bacteria (not all).

Anaerobes do NOT require oxygen.

Aerobes

Aerobes are organisms that use the Aerobic Respiration pathway.

Aerobes require oxygen.

Cellular Respiration Overview

Breakdown of glucose begins in the cytoplasm: the liquid part called cytosol

Sugar is the most common energy source (some cells use fats and proteins)

Requires many enzymes The enzymes “disassembly line” takes the sugar

apart, periodically releasing small amounts of energy that fuel the cell

Types of Cellular Respiration

At this point life diverges into two forms and two pathways

– Anaerobic cellular respiration (fermentation)

– Aerobic cellular respiration

Cellular Respiration Reactions

Glycolysis– Series of reactions which break the 6-carbon glucose

molecule down into two 3-carbon molecules called pyruvate

-all organisms from simple bacteria to humans perform it the same way

– Yields 2 ATP molecules for every one glucose molecule broken down

Glycolysisglyco means “glucose/sugar”, and lysis means “to split”. Therefore, glycolysis means “to split glucose”

This process was likely used to supply energy for the ancient forms of bacteria.

Anaerobic Cellular Respiration

Some organisms thrive in environments with little or no oxygen

– Marshes, bogs, gut of animals, sewage treatment ponds

No oxygen used= ‘an’aerobic Results in no more ATP, final steps in these pathways

serve ONLY to regenerate NAD+ so it can return to pick up more electrons and hydrogens in glycolysis.

End products such as ethanol and CO2 (single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells)

Anaerobic Cellular Respiration

Alcoholic Fermentation-some bacteria and fungi use this as their only source of energy.

Yeast in bread dough uses this and produces carbon dioxide that gets trapped in the dough and causes bread to rise.

Yeast is a leavening agent and is mentioned in the Bible.

(enzymes)

Sugar carbon dioxide + 2 ATP

Alcoholic Fermentation

Uses only Glycolysis. Does NOT require O2

Produces ATP when O2 is not available.

Alcoholic Fermentation

C6H12O6 2 C2H5OH + 2 CO2

(Ethyl Alcohol or Ethanol)

As a result of Alcoholic Fermentation,

Glucose is converted into 2 molecules of Ethyl Alcohol and 2 Molecules of Carbon

Dioxide.

Anaerobic Cellular Respiration

Lactic Acid Fermentation-produced and released by bacteria in yogurt, buttermilk, and sauerkraut.

If, when you exercise, you are not able to supply enough oxygen to muscle cells they will switch to anaerobic respiration which produces lactic acid.

The build up of lactic acid causes soreness in muscles.

Not as efficient as aerobic cellular respiration

Lactic Acid Fermentation

Uses only Glycolysis.Does NOT require O2

Produces ATP when O2 is not available.

Aerobic Cellular Respiration

Oxygen required=aerobic Mitochondria perform the “recharging” of ATP molecules

by transferring energy from the sugar molecules to ATP.(enzymes)

Sugar + oxygen carbon dioxide + water + 36 ATP

The cells of many organisms and your body perform this type of cellular respiration.

In order for Aerobic Respiration to continue the Pyruvic acid is first converted to Acetic Acid by losing a carbon atom and 2 oxygens as CO2.

The Acetic acid then must enter the matrix region of the mitochondria. The CO2 produced is the CO2 animals exhale when they breathe.

Phase Two: The Krebs Cycle(AKA the Citric Acid Cycle)

Sir Hans Adolf Krebs

Once the Acetic Acid enters the Matrix it combines with Coenzyme A to form a new molecule called Acetyl-CoA. The

Acetyl-CoA then enters the Krebs Cycle.

CoA breaks off to gather more acetic acid. The Acetic acid is

broken down.

3 NADH

+ 3H

Produces most of the cell's energy in the form of NADH and FADH2… not ATP

Does NOT require O2

Energy Tally

36 ATP for aerobic vs. 2 ATP for anaerobic

– Glycolysis 2 ATP

– Kreb’s (citric acid cycle) 2 ATP

– Electron Transport 32 ATP 36 ATP

Anaerobic organisms can’t be too energetic but are important for global recycling of carbon