Unit Two “Energy Acquisition” “How Cells Harvest Energy from Food”

Unit TwoUnit Two“Energy Acquisition”“Energy Acquisition”

““How Cells Harvest Energy How Cells Harvest Energy from Food”from Food”

Energy in FoodEnergy in Food Energy is obtained from Glucose for use Energy is obtained from Glucose for use

in building ATP via the removal of in building ATP via the removal of electrons from the Glucose moleculeelectrons from the Glucose molecule

““Cellular Respiration” is defined as the Cellular Respiration” is defined as the oxidation (loss of electrons) of food to oxidation (loss of electrons) of food to obtain energyobtain energy

Cellular Respiration is quite different Cellular Respiration is quite different from “Respiration” (breathing), from “Respiration” (breathing), however, the two are related in that however, the two are related in that “Respiration” supplies Oxygen to the “Respiration” supplies Oxygen to the cells so they can carry out “Cellular cells so they can carry out “Cellular Respiration”Respiration”

Energy in FoodEnergy in Food It is important to note that both plants and It is important to note that both plants and

animals participate in Cellular Respiration, animals participate in Cellular Respiration, and therefore, both have Mitochondria, the and therefore, both have Mitochondria, the organelle where ATP production occursorganelle where ATP production occurs

The main difference between plants and The main difference between plants and animals is that plants synthesize Glucose animals is that plants synthesize Glucose from smaller molecules ,whereas animals from smaller molecules ,whereas animals need to consume food matter in order to need to consume food matter in order to obtain Glucoseobtain Glucose

The above is why plants are called The above is why plants are called “Producers” and animals are called “Producers” and animals are called “Consumers”“Consumers”

Cellular Respiration and its Cellular Respiration and its StagesStages

Cellular Respiration is accomplished in three stages:Cellular Respiration is accomplished in three stages:– A) Glycolysis: production of ATP that takes place in the A) Glycolysis: production of ATP that takes place in the

cytoplasm of cells, and does not require Oxygen cytoplasm of cells, and does not require Oxygen (occurs in the Cytoplasm)(occurs in the Cytoplasm)

– B) Acetyl-CoA formation and Krebs Cycle: production B) Acetyl-CoA formation and Krebs Cycle: production of large amounts of ATP that takes place in the of large amounts of ATP that takes place in the Mitochondria, and does require Oxygen (occurs in the Mitochondria, and does require Oxygen (occurs in the Mitochondria) Mitochondria)

– C) Electron Transport Chain: NADH and FADHC) Electron Transport Chain: NADH and FADH22 release release electrons that fuel the movement of protons across electrons that fuel the movement of protons across inner mitochondrial membrane; result in the addition inner mitochondrial membrane; result in the addition of phosphate to ADP to generate lots of ATP (occurs in of phosphate to ADP to generate lots of ATP (occurs in the Mitochondria)the Mitochondria)

Chemical Reaction for Cellular Chemical Reaction for Cellular RespirationRespiration

Glucose + Oxygen Glucose + Oxygen Carbon Carbon Dioxide + Water + EnergyDioxide + Water + Energy

CC66HH1212OO66 + 6O + 6O22 6CO 6CO22 + 6H + 6H22O + O + energyenergy

Stage 1 of Cellular Stage 1 of Cellular RespirationRespiration

– A) Glycolysis: production of ATP that takes place A) Glycolysis: production of ATP that takes place in the cytoplasm of cells, and does not require in the cytoplasm of cells, and does not require OxygenOxygen

1. 2 Phosphates from 2 ATP’s are added to 1. 2 Phosphates from 2 ATP’s are added to GlucoseGlucose2. The “Phosphorylated” Glucose is split in 2. The “Phosphorylated” Glucose is split in

two, two, forming 2 three-carbon sugar phosphatesforming 2 three-carbon sugar phosphates3. In a series of reactions, both three-3. In a series of reactions, both three-

carbon carbon sugars phosphate groups are sugars phosphate groups are converted to converted to “Pyruvate”“Pyruvate”

4. The above Pyruvate forming process 4. The above Pyruvate forming process liberates liberates Hydrogen so it can bond with NAD+ Hydrogen so it can bond with NAD+ to form to form NADH, and 2 ATP’s are formed from NADH, and 2 ATP’s are formed from each each PyruvatePyruvate

GlycolysisGlycolysis

Stage 2 of Cellular Stage 2 of Cellular RespirationRespiration

– B) Acetyl-CoA formation and Krebs Cycle: B) Acetyl-CoA formation and Krebs Cycle: production of approximately 4 ATP’s that production of approximately 4 ATP’s that occurs in the Mitochondria and does require occurs in the Mitochondria and does require OxygenOxygen

1. A Carbon is removed from Pyruvate and 1. A Carbon is removed from Pyruvate and departs as a carbon dioxide moleculedeparts as a carbon dioxide molecule

2. The 2 carbon fragment that remains after 2. The 2 carbon fragment that remains after the removal of one Carbon joins to a structure the removal of one Carbon joins to a structure called “Coenzyme A” (CoA) forming a called “Coenzyme A” (CoA) forming a compound known as “Acetyl-CoA”compound known as “Acetyl-CoA”

Stage 2 of Cellular Stage 2 of Cellular RespirationRespiration

3. If the cell has ample amounts of ATP, then 3. If the cell has ample amounts of ATP, then Acetyl-CoA is funneled into fat synthesis; if Acetyl-CoA is funneled into fat synthesis; if the cell does not have ample amounts of the cell does not have ample amounts of ATP, then Acetyl-CoA is directed toward ATP, then Acetyl-CoA is directed toward ATP production via the Krebs CycleATP production via the Krebs Cycle

4. The Krebs Cycle begins when a 2 Carbon 4. The Krebs Cycle begins when a 2 Carbon fragment is transferred from Acetyl-CoA to fragment is transferred from Acetyl-CoA to a 4 Carbon molecule to form a 6 Carbon a 4 Carbon molecule to form a 6 Carbon moleculemolecule

5. The 6 carbon molecule has Carbon and 5. The 6 carbon molecule has Carbon and Hydrogen removed twice to form NADH Hydrogen removed twice to form NADH from NAD+, while the removed Carbons from NAD+, while the removed Carbons bond with Oxygen to form Carbon Dioxide bond with Oxygen to form Carbon Dioxide (byproduct)(byproduct)

Stage 2 of Cellular Stage 2 of Cellular RespirationRespiration

6. Finally, the resulting 4 Carbon 6. Finally, the resulting 4 Carbon molecule loses more Hydrogens via molecule loses more Hydrogens via oxidation to form FADHoxidation to form FADH22 and NADH and NADH

7. This final 4 Carbon molecule is the 7. This final 4 Carbon molecule is the starting material needed to begin starting material needed to begin Cellular Respiration again Cellular Respiration again

Krebs CycleKrebs Cycle

Step 3 of Cellular Step 3 of Cellular RespirationRespiration

C) Electron Transport Chain: formation of C) Electron Transport Chain: formation of approximately 30 ATP’s that occurs in the approximately 30 ATP’s that occurs in the Mitochondria in the presence of oxygenMitochondria in the presence of oxygen

1. NADH and FADH1. NADH and FADH22 transfer high energy transfer high energy electrons to molecules embedded in inner electrons to molecules embedded in inner mitochondrial membranemitochondrial membrane

2. Once they’ve donated electrons, NAD+ and 2. Once they’ve donated electrons, NAD+ and FAD FAD move back to Krebs Cyclemove back to Krebs Cycle

3. Electrons fuel a proton pump that results in the 3. Electrons fuel a proton pump that results in the addition of a phosphate group to an ADP to addition of a phosphate group to an ADP to

form form ATP; this happens approximately 30 times!ATP; this happens approximately 30 times!

Electron Transport ChainElectron Transport Chain

Cellular Respiration Cellular Respiration SummarySummary

3 Main stages3 Main stages– Glycolysis: occurs in Cytoplasm, can be Glycolysis: occurs in Cytoplasm, can be

aerobic or anaerobic and generates a net of aerobic or anaerobic and generates a net of 2 ATP’s2 ATP’s

– Formation of Acetyl-CoA and Krebs(Citric Formation of Acetyl-CoA and Krebs(Citric Acid) Cycle: occurs in Mitochondria, must be Acid) Cycle: occurs in Mitochondria, must be aerobic and generates approximately 4 ATP’saerobic and generates approximately 4 ATP’s

– Electron Transport Chain: occurs in Electron Transport Chain: occurs in Mitochondria, must be aerobic and generates Mitochondria, must be aerobic and generates approximately 30 ATP’sapproximately 30 ATP’s

Other Cellular FoodOther Cellular Food The focus to now has been the conversion The focus to now has been the conversion

of Carbohydrates (Glucose) into other of Carbohydrates (Glucose) into other molecules thereby liberating energy for use molecules thereby liberating energy for use by cellsby cells

There are other categories of There are other categories of macromolecules that can serve as the “Raw macromolecules that can serve as the “Raw Materials” for subsequent energy Materials” for subsequent energy production (Chapter 4)production (Chapter 4)

Proteins (Amino Acids) and Lipids (Fatty Proteins (Amino Acids) and Lipids (Fatty Acids) undergo chemical changes to Acids) undergo chemical changes to convert them into molecules that can be convert them into molecules that can be inserted into either stage of Cellular inserted into either stage of Cellular RespirationRespiration

Cellular Respiration Cellular Respiration OverviewOverview

http://www.phschool.com/science/http://www.phschool.com/science/biology_place/biocoach/cellresp/biology_place/biocoach/cellresp/intro.htmlintro.html

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