How Cells Harvest Chemical Energy Chapter 9
Cellular Respiration Releasing energy (ATP) from glucose (chemical energy) in the presence of O 2
Energy flows Matter cycles
True or False Plants only perform photosynthesis and animals only perform cellular respiration.
Respiration vs. Cellular Respiration
Cellular respiration Goal: produce ATP What type of reaction?
2 nd Law of Thermodynamics 1 glucose= up to 38 ATP 40% energy in glucose 60% lost as heat
Energy needs: Muscle cell 10 million ATP per second Exercise -> more ATP (more heat)
FYI: Energy just to maintain body 75% of energy from food each day Heart pumping blood Breathing Maintain body temperature Digest food
Oxidation-Reduction reaction AKA: Redox reaction Movement of electrons between molecules
Oxidation-Reduction reaction Oxidation: loss of electrons Reduction: gain of electrons LEO the lion says GER
Electrons transferred as H atoms Glucose is oxidized Oxygen is reduced
Help with Oxidizing Glucose Carbon Enzyme
Help with Oxidizing Glucose Coenzyme (niacin)
3 stages of Cellular Respiration 1. Glycolysis 2. Citric Acid Cycle (Kreb s cycle) 3. Oxidative Phosphorylation Electron transport chain (ETC) Chemiosmosis
Cellular Respiration Overview
GlycolysisOverview
Glycolysis Energy extracted from glucose -> ATP and NADH Cell can use immediately Needs to pass electrons to ETC Leftover energy from glucose is in pyruvate
Substrate Level Phosphorylation How ATP is made in glycolysis and citric acid cycle Enzyme transfers a phosphate from a substrate to ADP
Glycolysis Universal energy harvesting process No O 2 needed Occurs in cytoplasm
Glycolysis 9 chemical reactions Different enzyme for each Many intermediate compounds
2 phases of Glycolysis Phase 1 (steps 1-4): consume energy ATP energizes glucose in order to split it
2 ATPs used
G3P
2 phases of Glycolysis Phase 2 (steps 5-9): energy pay off 2 NADH and 4 ATP made
Glycolysis net energy yield 2 ATP used and 4 made Net gain of 2 ATP per glucose Some organisms can survive on this small energy yield
Glycolysis
Pyruvate Transported into mitochondria Must be prepped before it can enter citric acid cycle
Pyruvate Prep (x2)
Citric Acid Cycle overview AKA: Kreb s Cycle x2 per glucose
Each step catalyzed by different enzyme
Citric Acid Cycle
Structure of Mitochondria Intermembrane space
Proteins embedded in inner membrane Cytochrome
Oxidative Phosphorylation Electrons brought to ETC by NADH and FADH 2
*NADH is a higher energy molecule than FADH2
Oxidative Phosphorylation Carrier proteins bind and release e-by redox reactions (energy released) Energy used to actively transport H + across inner membrane
Oxidative Phosphorylation H + gradient stores potential energy Like water being held in a dam H + run down their concentration gradient through ATP synthase (can t cross membrane) Like water from dam rushes downhill ATP synthase activated to catalyze attachment of phosphate to ADP Like water spinning turbine to generate electricity
Oxidative Phosphorylation Oxygen is what pulls e-down the ETC ½ O 2 + 2e-+ 2H + = H 2 O Exergonic or endergonic? Electron transport ATP synthesis
Cellular Respiration Overview 2 H 2 O 2 CO 2 4 CO 2 4 H 2 O
How many e-does it take Each NADH with a pair of electrons produces enough of a H + gradient to make 3 ATP Each FADH 2 yields 2 ATP (starts ETC later)
Electron Transport Chain http://youtu.be/xbj0nbzt5kw http:// youtu.be/3y1do4nnaky
What would happen without oxygen?
Aerobic vs. Anaerobic Respiration Aerobic (Cellular) requires oxygen Anaerobic (fermentation) takes place in absence of oxygen
Anaerobic Respiration Glycolysis occurs 2 ATP 2 pyruvate 2 NADH NADH needs to be recycled back to NAD +
Lactic Acid Fermentation Occurs in muscle cells and some bacteria
Lactic Acid uses
Alcoholic Fermentation Occurs in yeast and some bacteria
Alcoholic Fermentation uses Is yeast found in alcoholic beverages?
Facultative Anaerobes Can use aerobic or anaerobic respiration Ex: Yeast, muscle cells, some bacteria
Obligate Anaerobes Require anaerobic conditions Ex: Bacteria living in stagnant ponds or deep in soil
Is aerobic or anaerobic respiration more efficient at converting glucose to energy?