A&P II- Cellular Respiration

Metabolism and Nutrition

Metabolic reactions: consumed nutrients ->chemical energy and raw materials -> body’s growth, repair, and normal functioning

Metabolism: sum of all body chemical reactions

Catabolism:

• breaking down larger molecules into smaller molecules.

• Exergonic: provide more energy than they consume

• Provides energy and raw materials for

Anabolism :

• building up smaller molecules into larger molecules.

• Endergonic; consume more energy than they produce

• Growth and Repair

A nutrient is a “food or liquid that supplies the body’s metabolic needs".

Nutrients include:

Necessary chemical

• Water, Minerals(inorganic), Vitamins (organic)

Fuel for energy

• Carbohydrates, Lipids, (Proteins)

Building block or raw material

• Carbohydrates, Lipids, (Proteins)

ATP

• Cellular reactions create/use energy in the “high-energy” phosphate bonds of ATP, where it can be released quickly and easily

• ATP temporarily stores and transfers energy given off in catabolic reactions and transfers it to anabolic reactions that require energy

Redox reactions

REDOX reactions

Chemical reactions in which a pair of electrons are exchanged

 Oxidation: removal (Loss) of electrons

 Reduction: addition (Gain) of electrons

• Oxygen REALLY attracts electrons

• Reducing oxygen (and oxidizing something else) gives energy

Biological REDOX reactions often move hydrogen ions along with the electrons and so are called dehydrogenation (REDOX ) reaction

• The electrons/hydrogen are transferred to intermediaries NAD, or FAD (B vitamins)

Carbohydrate Metabolism

• Glucose is the body’s preferred source of fuel

• The oxidation of glucose to form ATP...

Glucose (C6H12O6) + O2  CO2 + H2O + ATP

... is known as “Cellular Respiration” and occurs in 4

• Glycolysis : Glucose -> 2 Pyruvic Acid +2[H2] +2 ATP

• Formation of Acetyl CoA: 2{Pyruvic Acid->Acetyl + CO2+[H2]}

• Krebs/Citric Acid Cycle : 2{Acetyl->2 CO2+ATP+4[H2]}

• Electron Transport Chain: 6{O2+2[H2]->2 H2O+~5 ATP}

Glycolysis

• 1st step in cellular respiration

• one 6-carbon molecule of glucose into two 3-carbon molecules of pyruvate (pyruvic acid) in a series of steps

• It occurs in the cytoplasm/cytosol

• It does not require oxygen

Glucose is

• Phosphorylated with ATP

• Oxidized

Phosphorylates ATP

• Broken down to pyruvate

• Produces

  • 2 net ATP

  • 2 NADH

  • 2 pyruvate

Pyruvate->AcetylCoA OR Lactic acid

2nd step in cellular respiration

Possibility - depends on the availability of enough oxygen!

 Aerobic (oxygen is present) the cell will form acetyl-CoA and continue cellular respiration

 Anaerobic the cell will form lactic acid to remove the Hydrogen generated by glycolysis (removing NADH and restoring NAD+)

Formation of Lactic Acid takes place in the cytoplasm/cytosol

• Pyruvate + NADH-> Lactic Acid + NAD+

Formation of Acetyl-CoA takes place in the mitochondria

• Pyruvate + CoA+NAD+ -> Acetyl-CoA+ NADH + CO2

Krebs/ Citric Acid Cycle

• In the matrix of the mitochondria

• Acetyl-CoA "drops off" the 2-carbon Acetyl fragments, the CoA diffuses back to “reload”

• Each turn of the cycle, completely oxidizes an Acetyl

Yields:

• 2 CO2, 1 ATP, 1 FADH2, and 3 NADH

Electron Transport Chain

Electron transport chain – (ETC) takes the electrons through a series of redox reactions until they reach oxygen

 series of cytochromes: electron carriers embedded within the inner membrane of the mitochondrium (folded into cristae)

Cellular Respiration

• Transferred electrons passed frome one cytochrome to another, from high energy level to a lower energy level

• This siphons-off the energy from passing the electrons to oxygen

• 'Electron transfer energy' captured by pumping H+ ions into the inner mitochondrial space.

• Creating a proton motive force

• Concentration gradient and an Electrical gradient

H+ ions flow back across the membrane. The channels through which the H+ ions flow (in the inner mitochondrial membrane) are tied to an ATP synthase that generates ATP from ADP and P

Oxygen becomes the final electron acceptor

• The oxygen forms H2O (metabolic water – about 200 ml/day)

The other product is

• 3 ATP per NADH

• 1-2 ATP per FADH2

• For a total of 32-34 ATP

Summary of Cellular Respiration

Total oxidation of 1 molecule of glucose:36-38 molecules of ATPs

• 4 ATP: substrate level phosphorylation (directly transferring a high energy phosphate from one organic molecule to another) in glycolysis and the Krebs cycle

• either 32 or 34 ATP: oxidative phosphorylation using the cytochromes of the electron transport chain