CELL RESPIRATION & METABOLISM Dr. Perkins

PURPOSE OF CELL RESPIRATION TO MAKE ATP Adenosine triphosphate Metabolism is actually the sum total of all the chemical reactions in the body that break down molecules and rebuild them. To make ATP, or to consume energy Catabolism is all the chemical reactions in the body that break down molecules to make ATP  Anabolism is all the chemical reactions in the body that build molecules into new body structures

What is ATP? It’s the universal energy carrier Phosphate groups ATP Energy P Hydrolysis Adenine Ribose H2O Adenosine diphosphate Adenosine Triphosphate + ADP This reaction represents the hydrolysis of ATP, which releases energy.

Anabolism + Catabolism = Metabolism Your “Metabolism” Food breakdown leads to: Release of energetic electrons Capture of electrons by NAD+ to make NADH This drives the synthesis of ATP Metabolism = all reactions in the body that involve energy transformation Anabolism + Catabolism = Metabolism

Cellular Respiration “Anaerobic” = “without oxygen” “Aerobic” means “with oxygen.” Aerobic respiration produces about 20 times more ATP than Anaerobic respiration. But anaerobic respiration provides the ATP we need if we need short bursts of energy.

A Metabolic Pathway is… Cellular Respiration consists of metabolic pathways.. A Metabolic Pathway is… series of enzyme-controlled reactions leading to a product each new substrate is the product of the previous reaction SOME REACTIONS ARE ENDERGONIC; OTHERS ARE EXERGONIC

OVERVIEW

GLYCOLYSIS STARTS WITH GLUCOSE GLUCOSE IS A simple sugar (C6H12O6) Atoms held together by covalent bonds Glucose

Electrons transfer energy between molecules. GLYCOLYSIS One 6-carbon glucose is “oxidized” to form two 3-carbon PYRUVATE molecules Electrons transfer energy between molecules. Molecule “A” gives up electrons, and is oxidized. Molecule “B” receives electrons is reduced. NAD NADH

Glycolysis Occurs in Two Stages 2. Energy is released as ATP or electrons 1. ATP Energy is added to Glucose

fructose1,6-bisphosphate 1. ENERGY-REQUIRING STEPS OF GLYCOLYSIS IN THE CYTOSOL GLUCOSE ADP P ATP glucose-6-phosphate 2 ATP are required for glycolysis. fructose-6-phosphate P ATP fructose1,6-bisphosphate P ADP PGAL P

Energy-Releasing Steps 2. ENERGY-RELEASING STEPS OF GLYCOLYSIS P P PGAL PGAL NAD+ NAD+ IN THE CYTOSOL Pi NADH Pi NADH P P P P 1,3-bisphosphoglycerate 1,3-bisphosphoglycerate ADP ADP ATP ATP P P 3-phosphoglycerate 3-phosphoglycerate 4 ATP and 2 NADH are produced in glycolysis. P P Energy-Releasing Steps 2-phosphoglycerate 2-phosphoglycerate H2O H2O P P PEP PEP ADP ADP ATP ATP pyruvate pyruvate

Q: WHAT IS THE PURPOSE OF NADH? REVIEW A: NADH RECEIVES ELECTRONS IN A REDOX REACTION FADH is also an electron carrier and it works just like NADH

LACTIC ACID FERMENTATION Pyruvate is converted to LACTIC ACID Benefit: NAD+ is produced, which can be used for glycolysis to help make 2 ATP (just a little). LACTIC ACID causes soreness in skeletal muscle Note: the heart only respires aerobically. RBCs only use lactic acid fermentation because they lack mitochondria.

Cori Cycle: Lactic Acid is Converted Back to Pyruvate in the Liver -- the amount of oxygen you need to convert lactic acid to pyruvate is called “oxygen debt.” Lactic acid dehydrogenase The liver can convert pyruvate to G-6-P  glucose  release to blood

Not Enough Oxygen to the Heart: CLINICAL APPLICATION: Not Enough Oxygen to the Heart: Myocaridal ischemia refers to inadequate blood flow to heart muscle. Sometimes called coronary heart disease because of inadequate blood flow in coronary arteries. atherosclerotic heart disease Prolonged ischemia can cause death of heart cells, which leads to myocardial infarction (heart attack). When lactic acid builds up in heart muscle, chest pain (angina pectoris) results. TREATMENT: nitroglycerin, which improves blood flow.