Cellular Respiration

 Breaking down carbohydrates (glucose or glycogen (stored glucose)) into energy  All living organisms must carry out cellular respiration to survive

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: C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O

Glycolysis:  The first step in the breakdown of glucose (Oxidation of glucose)  Occurs in the cytoplasm  Produces 2 pyruvates which then go to the Kreb’s cycle (aerobic) or lactate which enters into anaerobic respiration  Produces a net gain of 2 ATP (energy)

C.R. Reactions  Glycolysis Series of reactions which break the 6- carbon glucose molecule down into two 3-carbon molecules called pyruvate Series of reactions which break the 6- carbon glucose molecule down into two 3-carbon molecules called pyruvate Process is an ancient one-all organisms from simple bacteria to humans perform it the same way Process is an ancient one-all organisms from simple bacteria to humans perform it the same way Yields 2 ATP molecules for every one glucose molecule broken down Yields 2 ATP molecules for every one glucose molecule broken down Yields 2 NADH per glucose molecule Yields 2 NADH per glucose molecule

Cellular Respiration Overview  Breakdown of glucose begins in the cytoplasm: the liquid matrix inside the cell  At this point life diverges into two forms and two pathways Anaerobic cellular respiration (aka fermentation) Anaerobic cellular respiration (aka fermentation) Aerobic cellular respiration Aerobic cellular respiration

Anaerobic Respiration:  In the absence of oxygen  The second step in the break down of glucose  Occurs in the cytoplasm  Primary process in skeletal muscle cells  Produces 0 net ATP but lots of NAD + and lactate  Allows glycolysis to continue  Runs 100X faster than aerobic respiration  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 Respiration  Some organisms thrive in environments with little or no oxygen Marshes, bogs, gut of animals, sewage treatment ponds 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 CO 2 (single cell fungi (yeast) in beer/bread) or lactic acid (muscle cells)

Oxidative (Aerobic) Respiration:  In the presence of oxygen  Also a second step in the break down of glucose  Occurs in mitochondria  Includes the Kreb’s cycle (2 ATP) and oxidative phosphorylation (32 ATP)  Produces a net of 34 ATP

Aerobic Cellular Respiration  Oxygen required=aerobic  2 more sets of reactions which occur in a specialized structure within the cell called the mitochondria 1. Kreb’s Cycle 1. Kreb’s Cycle 2. Electron Transport Chain 2. Electron Transport Chain

Kreb’s Cycle  Completes the breakdown of glucose Takes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen atoms end up in CO 2 and H 2 O Takes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen atoms end up in CO 2 and H 2 O Hydrogens and electrons are stripped and loaded onto NAD + and FAD to produce NADH and FADH2 Hydrogens and electrons are stripped and loaded onto NAD + and FAD to produce NADH and FADH2  Production of only 2 more ATP but loads up the coenzymes with H + and electrons which move to the 3 rd stage

Electron Transport Chain  Electron carriers loaded with electrons and protons from the Kreb’s cycle move to this chain-like a series of steps (staircase).  As electrons drop down stairs, energy released to form a total of 32 ATP  Oxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water

Energy Tally  36 ATP for aerobic vs. 2 ATP for anaerobic Glycolysis 2 ATP Glycolysis 2 ATP Kreb’s 2 ATP Kreb’s 2 ATP Electron Transport32 ATP Electron Transport32 ATP 36 ATP 36 ATP  Anaerobic organisms can’t be too energetic but are important for global recycling of carbon

Reaction: (Aerobic Glycolysis & Oxidative Phosphorylation) C 6 H 12 O O 2 6 CO H 2 O + 36 ATP Enzymes Glucose Oxygen Carbon Dioxide WaterEnergy

Cellular Respiration Glycolysis Anaerobic Respiration Anaerobic (without O 2 ) Aerobic (with O 2 ) Aerobic Respiration

Anaerobic Respiration Lactic Acid Fermentation Alcohol & CO 2 Fermentation Ex: Muscles Ex: Bacteria & Yeast Cellular Respiration

Energy Comparison: Glycolysis Fermentation Total Anaerobic Aerobic 36 2 Kreb’s Cycle & Oxidative Phosphorylation 34

Process: Photosynthesis Organism: Plant Place Occurs: Chloroplast Glucose and O 2 Process: Respiration Organism: ALL Place occurs: Mitochondria/ Cytoplasm CO 2 and H 2 O ATP Cycle of Energy in Life