Honors Biology Chapter 6 Cellular Respiration How Cells Harvest Chemical Energy

Mitochondria – “power house” Compartments - for different stages Matrix –Space enclosed by inner membrane Inner membrane –Deeply folded, more surface –Many reactions at the same time Cristae - folds in membrane Intermembrane space –Between inner and outer membrane

Honors Bio Ch. 6:Cell Respiration All life activities need energy a. Maintain homeostasis; do life functions breathe, circulate blood active transport, biosynthesis regulate temperature, etc. b. Physical and mental activity c. Cells use energy in ATP molecules

Food energy is measured in calories Food labels: Calorie (Kcal) = 1000 calories calorie = energy needed to raise the temperature of one mL water 1 degree Celsius 1 gram carb = 4 cal 1 gram fat = 9 cal 1 gram protein = 4 cal

Photosynthesis – makes food Light energy  chemical energy in food –Plants, algae, cyanobacteria 6 H 2 O + 6 CO 2  C 6 H 12 O O 2 Respiration – breaks down food for enery C 6 H 12 O O 2  6 H 2 O + 6 CO 2 Energy in food  energy in ATP All living things Aerobic and anaerobic Energy flow is one-way Chemicals recycle 6.1 Photosynthesis and cellular respiration - energy for life

Oxygen and Energy Aerobic respiration harvests the most ATP from glucose Aerobic Anaerobic Glucose completely broken down Glucose partly broken down Yields max amount of ATP Yields 2 ATP/glucose Most organisms Only a few microorganisms Products: CO 2 and H 2 O Products: depends on organism 3 stages of breakdown 2 stages of breakdown 1. Glycolysis 2. Kreb’s cycle 2. Fermentation 3. Electron Transport Chain

Breathing supplies oxygen to cells 1) Breathing brings oxygen into the body 2) Oxygen in lungs diffuses into blood 3) Blood delivers oxygen to all body cells 4) Oxygen is used in cell respiration. 5) CO 2 diffuses out of cells into blood 6) Blood carries CO 2 back to lungs - exhaled

Gas exchange is by diffusion In the lungs: Air inhaled, fills alveoli - O 2 diffuses into blood CO 2 diffuses from blood - into alveoli - is exhaled

Cells use oxygen for respiration In cells: O 2 goes IN - CO 2 goes OUT

Basics of Cellular Respiration Breaks down glucose in many small steps a biochemical pathway Energy released is stored in molecules of ATP –Each ATP has enough energy for one cell task One glucose molecule yields 36 ATP

Redox reactions in cellular respiration Overview: Glucose loses energy – oxidized Oxygen gains energy – reduced Glucose breakdown is a series of redox reactions -electron energy is used to make ATP

Electron/H+ Acceptors Help in reaction pathway, re-used 2 in respiration: NAD and FAD Accept hydrogen ions and electrons from glucose as it breaks down Transfer them to another molecule later in pathway –makes ATP

Oxidation dehydrogenase NAD  2H2H 2 e   2H  Reduction NADH HH 2e- Enzymes and coenzymes in cellular respiration Dehydrogenase enzyme - removes H Hydrogen/Electron Acceptors (coenzymes) NAD+ + 2 H  NADH + H+ (reduced) FAD + 2 H  FADH 2 (reduced) NAD = nicotinamide adenine dinucleotide FAD = flavin adenine dinucleotide

LE 6-6 NADH High-energy electrons carried by NADH GLYCOLYSIS GlucosePyruvate Cytoplasm ATP Substrate-level phosphorylation Substrate-level phosphorylation CITRIC ACID CYCLE CO 2 ATP NADH FADH 2 and ATP Mitochondrion Oxidative phosphorylation OXIDATIVE PHOSPHORYLATION ( Electron Transport and Chemiosmosis) Cellular respiration occurs in three main stages Chemiosmosis makes ATP Begins glucose breakdown Removes CO 2 Harvests H+ and e-

1 st stage – Glycolysis (in cytoplasm) Glycolysis - “sugar splits” - forms two smaller molecules Energy invested a. 2 ATP phosphorylate glucose b. glucose splits in two c. 3-carbon intermediate forms (PGAL, G3P)

2 ATP invested Energized glucose splits Hydrogen ions and electrons removed 4 ATP made Net yield 2 Final carbon compound

Glycolysis breakdown 1)Each G3P (PGAL) loses hydrogen to NAD+ a) makes NADH b) G3P changes to pyruvic acid 2) 4 ATP are produced, but net yield is 2 Products of glycolysis: 1) 2 ATP 2) 2 NADH 3) 2 pyruvic acid (3 carbons)

All organisms do glycolysis Need no oxygen or special organelles Probably evolved very early in history of life Can meet energy needs of some simple organisms

6.8 IF oxygen is present, pyruvate moves into mitochondrion One carbon is removed  CO 2 More hydrogens to NAD  NADH Coenzyme A bonds to 2-carbon acetyl  acetyl CoA

Sir Hans Krebs German chemist, 1930s Described the cycle of reactions that make energy in cells Received Nobel in 1953 “Krebs Cycle” or “Citric Acid Cycle”

Krebs Citric Acid Cycle Stage 2 in aerobic respiration In matrix Completes breakdown of glucose to carbon dioxide Makes many molecules of NADH and FADH 2 (make energy later)

Krebs Cycle 1) START – acetyl CoA 2) 4-C oxaloacetate in matrix 3)acetyl + oxalo  6 C citric acid 4) 2 carbons removed  CO 2 5) one ATP forms 7) END:oxaloacetate recycled 6) hydrogens removed, NADH, FADH2 form

LE 6-9b Acetyl CoA CoA Oxaloacetate C ITRIC A CID C YCLE Citrate 2 carbons enter cycle leaves cycle Alpha-ketoglutarate leaves cycle CO 2 NAD  NADH  H  ADP ATP P  CO 2 NADH  H  NAD  NADH NAD   H  Malate FADH 2 FAD Succinate

Products of Krebs Cycle 1.2 ATP/glucose molecule (one each “turn”) 2. Several molecules of NADH and FADH 2 – These will yield energy in stage 3 3. Last carbons in glucose form CO 2 and diffuse out of cell

Review: Krebs Cycle 1.START – acetyl CoA (2C) 2.Joins 4C compound in matrix (oxaloacetate) 3. Forms 6C citric acid  2 CO 2 4. Carriers NAD+, FAD reduced 5. Each cycle makes 1 ATP (2 ATP/glucose) 6. 4C compound returned 7. END: CO 2, NADH, FADH 2, ATP

Most ATP is made in Stage 3 Electron Transport Chain (in cristae) –H ions power ATP synthesis

Electron transport chain Electrons pass from one acceptor molecule to the next The energy released is used to make ATP NAD+ and FAD can now be reused NADH and FADH 2 give up their electrons and H+

Chemiosmosis Only proceeds if oxygen is available to take electrons at end of chain  makes water O + 2H e -  H 2 O

1) Starting molecules NADH, FADH 2 release their electrons and H+ 2) Electrons pass from one protein in transport chain to next 3) Electron energy used to pump H+ into intermembrane space 4) H+ diffuse through ATP synthase (chemiosmosis) 5) ADP + P  ATP 6) Final electron acceptor is oxygen

Electrons power ATP synthase enzyme makes ATP Total ATP yield per glucose: Glycolysis – 2 ATP Krebs – 2 ATP ETC - 32 ATP Total = 36 ATP OXIDATIVE PHOSPHORYLATION - Inorganic PO 4 added to ADP - ADP + P  ATP

Cytochromes Transfer electrons in cell respiration

Cytochromes show evolutionary relationships amino acids # of differences shows evolution between species

Summary of Aerobic Respiration PathwayReactantsProducts# ATPLocation GlycolysisGlucose + O 2 Pyruvic Acid NADH 2cytoplasm Krebs Cycle Acetyl CoACO 2 NADH FADH 2 2 Mitochondrial matrix Electron Transport Chain NADH FADH O 2 H 2 O32 Mitochondrial cristae Total ATP36

CYTOCHROMES in transport chain ( used to find evolutionary relationships)

LE 6-12 Cytoplasm Electron shuttle across membrane 2 G LYCOLYSIS NADH (or 2 FADH 2 ) 2 Acetyl CoA Maximum per glucose: 2 Pyruvate C ITRIC A CID C YCLE Mitochondrion FADH 2 2 O XIDATIVE P HOSPHORYLATION (Electron Transport and Chemiosmosis)  about 34 ATP  2 ATP by oxidative phosphorylation by substrate-level phosphorylation About 38 ATP  2 ATP by substrate-level phosphorylation Glucose Review Aerobic Respiration – 3 stages

Needs no oxygen Makes no additional ATP after glycolysis Hydrogen on NADH returns to pyruvic acid –Pyruvate is the “final electron acceptor” NAD+ can be reused Pyruvate is rearranged into a final product Fermentation anaerobic respiration

Lactic Acid Fermentation Many anaerobic bacteria make lactic (and other) acids Commercial uses: cheese, yogurt, soy products, sauerkraut Muscle cells – can do fermentation temporarily lactic acids builds up  “oxygen debt” Muscles fatigue, cramp With fresh oxygen: Lactic acid converted back to pyruvate  Kreb’s

Lactic acid Fermentation Pyruvic Acid (3 carbons)  Lactic acid (3 carbons) No more ATP made No further glucose breakdown NAD+ returned for reuse

Alcohol Fermentation Some yeasts Pyruvic acid (3C)  CO 2 + ethyl alcohol (2C) Baking, brewing beer and wine CO 2 gas makes bread dough rise, bubbles in beer and champagne NAD+ returned for reuse No more ATP made

LE 6-14 Food, such as peanuts Sugars Glycerol Fatty acids Amino acids Amino groups Proteins Fats Carbohydrates Glucose Pyruvate G3P GLYCOLYSIS Acetyl CoA CITRIC ACID CYCLE OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis ) ATP Other foods can be broken down for energy Entry point in pathway depends on fragment size Proteins: CHON nitrogen wastes

Biosynthesis – cells make all the molecules they need ATP CITRIC ACID CYCLE Acetyl CoA Amino groups Proteins Amino acidsFatty acidsGlycerol Fats Cells, tissues, organisms Carbohydrates Sugars GLUCOSE SYNTHESIS PyruvateG3PGlucose Use raw materials in food

Cells make all the molecules they need using raw materials in food - biosynthesis 1. Not all food is used for energy 2. Cells can use monomers in food to make new molecules Also use intermediate compounds in glycolysis and Kreb’s 3. can make molecules not found in food Ex. Human protein from plant or animal protein 4. Biosynthesis uses ATP

Some Poisons Block ETC and Stop Chemiosmosis

How Poisons Kill STOP H+ flow through ATP synthase a) Some block electron transfer b)Some don’t concentrate H+  no H+ gradient, no ATP