2. Cellular Respiration A series of metabolic pathways involving 3 separate phases: Krebs cycle electron transport system oxidative phosphorylation Oxidizes pyruvate to ATP & CO 2 Text pg 117 So why is ATP so important? But, in the presence of Oxygen….

ATP Energy released by the oxidation (controlled burning) of carbohydrates and fats, and energy harvested by photosynthesis in green plants, are channeled into making the molecule adenosine triphosphate (ATP). ATP is a high energy compound considered to be the universal currency of biological energy. On reaction of ATP with water under closely controlled conditions, a high energy bond is ruptured releasing energy, and producing adenosine diphosphate (ADP) and phosphate. This release of energy is usually coupled to other biological processes, to do work, for example, in the contraction of muscle and in the synthesis of the essential macromolecules of life, nucleic acids and proteins. The ATP molecule is then remade from the ADP and phosphate with further input of energy. The synthesis of ATP is a central process in human nutrition. The energy in the food we ingest is converted into ATP. Each day every one of us of makes, breaks down and remakes in the mitochondria in our bodies an amount of ATP that is about the same as our body weights. The energy in the ATP molecule powers all biological processes. Thus, the synthesis of ATP is essential for life.

Where in the cell does this occur? Mitochondria double membrane bound organelle site of aerobic cellular respiration source of cellular energy

Mitochondria: Structure Outer membrane Intermembrane space Inner membrane (with folds called cristae) Matrix Text Pg. 68

The Mitochondrion Outer Membrane Inner Membrane Cristae Intermembrane space Matrix

Outer Membrane (& Intermembrane space) permeable to small molecules (to ~10,000 MW) contains transmembrane pores (porins) which allow these molecules to pass composition of intermembrane space closely matches cytoplasm

Inner Membrane highly folded into “cristae” folds greatly increase surface area relatively impermeable to solutes surface facing matrix lined with small lollipop-like particles (F1 particles)

F1 Particles about 9 nm in diameter 10,000 to 100,000 per mitochondria face matrix side of inner membrane contain ATP synthase enzyme couples oxidation reactions with phosphorylation to produce ATP Plant chloroplast F1 particles (ATP synthase) visualized at room temperature using atomic force microscopy

F1 Particles = ATP Synthase Protein particles which embed in inner mitochondrial membrane and face matrix Actual site of ATP production in mitochondria F0F0 F1F1

Matrix inner space of mitochondria rich in proteins contains ribosomes (70S) and DNA derived from endosymbiotic prokaryote?? site of oxidative metabolism (Krebs cycle)

KK ATP NADH ETC Krebs Cycle Krebs Cycle KK

ATP NADH Krebs Cycle KK

10 enzymes act in sequence to: Convert 1 Glucose (6C) --> 2 Pyruvate (3C) 2 ATP’s produced 2 NADH produced Reactions occur in cytoplasm Next…

KK Krebs Cycle KK

Pyruvate moves to Mitochondria and is oxidized to Acetyl-CoA

glucose 6C pyruvate 3C Glycolysis & A-CoA Production 2 NADH 2 ATP In MitochondriaNADH CO2 Acetyl CoA 2C In Cytoplasm

Next, Acetyl- CoA enters the Krebs Cycle

Text pg 123

NADH CO2 citric acid 6C a-Ketoglutarate 5C Succinyl CoA 4C NADH CO2 Fumarate 4C Malate 4C ATP FADH 2 NADH acetyl CoA 2C Succinate 4C Oxaloacetate 4C

Krebs Cycle Acetyl CoA from pyruvate oxidation is the main input to cycle A-CoA combines with 4C oxalo-acetate to form 6C citrate subsequent reactions produce molecules with 5C and 4C… causing the release of CO 2 molecules each time Additionally, these reactions produce NADH, FADH 2 and ATP

Krebs Cycle For each A-CoA going into Krebs… 3 NADH, 1 FADH 2, 1 ATP & 2 CO 2 are produced The 2 CO 2 molecules released in the cycle convert 6C citrate back to 4C molecules and result in 4C oxaloacetate to renew the cycle Note: 2 A-CoA are produced for each glucose consumed!

Respiration and ATP How many ATPs have we produced so far from 1 glucose molecule? 2 ATP from glycolysis 2 ATP from Krebs Cycle Both termed substrate-level phosphorylation Krebs, so far, has doubled ATPs from Glycolysis But, not over yet..…

Remember the NADH & FADH 2 Produced? And, the 2 NADH from Glycolysis

NADH, FADH 2 Production in Mitochondria Each Pyruvate to Acetyl-CoA = 1 NADH 2 Pyruvates (from glucose) = 2NADH Each Acetyl-CoA in Krebs = 3 NADH & 1 FADH 2 2 Acetyl-CoA = 6 NADH & 2 FADH 2

Total NADH & FADH 2 2 NADH from Glycolysis 2 NADH from Pyr oxidation 6 NADH from Krebs Plus: 2 FADH 2 from Krebs Cycle

These Energy-Rich Molecules pass on e- to an Electron Transport Chain Along this ETC, new ATP is synthesized from the energy-rich NADH and FADH 2 molecules…