Chapter 22 – pp Unit III: Lively Molecules Cellular Respiration

1.Foods (Big Molecules) are broken down (digested) to form… 2.Smaller Molecules that can diffuse into the blood and be carried to the tissues… 3.In the cells, the small molecules are used to either release energy or to build new big molecules. The Big Picture

Energy must be released: Slowly Continuously And in a usable form The Problem

Cellular processes that release energy stored in chemical bonds in a series of small steps. The energy is then: Usable Continuous High temperatures are not required The Answer

Glucose + O 2  CO 2 + H 2 O + Energy C 6 H 12 O O 2  6 CO H 2 O + Energy OR Cellular Respiration! The Reaction:

Function: Release energy stored in the chemical bonds of food molecules in a controlled way. Adenosine Triphosphaten (ATP) Cellular Respiration

ATP (Adenosine Triphosphate) Adenosine triphosphate (ATP) Adenosine diphosphate (ADP) Adenosine monophosphate (AMP) Adenosine Adenine Ribose Phosphate groups High-energy bonds

Holds energy in covalent bonds –2nd and 3rd phosphate groups have high energy bonds ATPases hydrolyze the 3 rd high energy phosphate bond ATP  ADP + P + energy orADP + P + energy  ATP ATP is a way for a cell to transport energy to where it is needed. Coenzymes are vital for cellular respiration –NAD + (niacin) and FAD (riboflavin) ATP

Overview Occurs in cytoplasm Anaerobic phase Glucose (6C) split into 2 pyruvic acid molecules (3C) yields 2 ATP Three Major Pathways Glycolysis

Three Major Pathways Glycolysis 1.Phosphorylation –glucose enters cell has phosphate added - ATP used –maintains favorable concentration gradient, prevents glucose from leaving cell 2.Priming –isomerization occurs –phosphorylation further activates molecule - ATP used 3.Cleavage –molecule split into 2 three-carbon molecules

Three Major Pathways Glycolysis 4. Oxidation –removes H + and H - –NAD + + H -  NADH –Inorganic phosphate 5. Dephosphorylation –transfers phosphate groups to ADP to form (4) ATP –produces pyruvic acid 4 ATP produced total End Products 2 pyruvic acid + 2 NADH + 2 H ATP

Demand for ATP > oxygen supply ATP produced by glycolysis –glycolysis can not continue without supply of NAD + –NADH reduces pyruvic acid to lactic acid, regenerating NAD + Three Major Pathways Anaerobic Fermentation

Three Major Pathways Anaerobic Fermentation Lactic acid travels to liver –stored as glycogen or released as glucose –Oxygen debt Fermentation is inefficient

Require oxygen as final electron acceptor Most ATP generated in mitochondria Three Major Pathways Aerobic Respiration CO 2 H2OH2O O2O2 ATP Citric acid cycle Coenzymes Electron transport system MITOCHONDRIA Two-carbon chains Three-carbon chains Fatty acids Glucose Amino acids Proteins Glycogen Triglycerides Nutrient pool Structural, functional, and storage components

Three Major Pathways Aerobic Respiration Matrix Reaction – “Link Reaction” Three steps prepare pyruvic acid to enter Krebs (citric acid) cycle 1.Decarboxylation - 3-C becomes a 2-C compound 2.Convert that to an acetyl group (remove H) 3.Bind it to coenzyme A Known as formation of acetyl-coenzyme A

Three Major Pathways Aerobic Respiration Matrix Reaction - Krebs (Citric Acid) Cycle Acetyl-Co A + 4-C = 6-C compound (citric acid)-- start of cycle Series of enzyme-catalyzed reactions to release: –NADH & FADH 2 –carbon atoms – makes CO 2 –Synthesize ATP

Three Major Pathways Aerobic Respiration Membrane Reaction – Electron Transport Chain Purpose: –to oxidize NADH and FADH 2 –transfer their energy to ATP –regenerate NADH and FADH Reactions carried out by series of carrier molecules and enzymes As electrons are transferred along transport chain, their potential orbital energy is released Final electron acceptor is Oxygen Result is a molecule of water and 30 ATP

Three Major Pathways Aerobic Respiration Draws from nutrient pool: Glucose is primary source Fats and proteins are more important as structural components. Converted to pyruvic acid or acetyl-coenzyme A Proteins produce ammonia (very toxic)  urea (less toxic). Nutrients obtained through digestion and absorption Nutrients in the blood Cells in most tissues continuously use glucose. Neural tissue requires glucose. During starvation, other tissues shift to fatty acid or amino acid use. Liver cells store triglycerides & glycogen. Released as fatty acids and glucose. Skeletal muscles build glycogen reserves. Amino acids released. Adipocytes convert excess fatty acids to triglycerides for storage.

Cellular Respiration Aerobic Respiration vs. Anaerobic Fermentation

Releases energy in chemical bonds of food. Products: Synthesizes ATP Waste products: –water –CO 2 –energy dissipated as heat Each step along the way is catalyzed by enzymes Cellular Respiration Summary