Cellular RespirationCh. 8

How we get Energy from Light• Cellular respiration is just a

series of steps where energy is transfer between different molecules through a flow of electrons

• The ultimate goal is to produce ATP

• The initial start of the process is light during photosynthesis

• What is the final acceptor of the electrons used to make ATP?– Oxygen– Combines with H+ to make

water

OIL RIG• OIL Oxidized if lose (electrons)

– Electron donor– Decrease in positive electric charge

• RIG Reduced if gain (electrons)– Electron acceptor– Increase in positive electric charge

• What types of reactions have this occur?– Redox reaction

• Not all redox have complete exchange of electrons– Figure 8.2– Moving electrons closer or further

from the central atom shows change in energy

– Carbon partially lost electrons– Oxygen partially gained

Steps of Cellular Respiration

• 3 steps:1) Glycolysis

– Glucose is broken into 2 pyruvate molecules

2) Pyruvate Oxidation and Citric Acid Cycle– Pyruvate is made into Acetyl-

CoA and enters a reaction cycle

3) Oxidative Phosphorylation– Electron transporter

molecules move to the inner mitochondria membrane and generate ATP

C6H12O6+ 6O2+ 32ADP+ 32Pi 6H2O+ 6CO2+ 32 ATP

Glycolysis• 10 enzymes are required• Steps 1 and 3 hydrolysis ATP to

build instability and power breaking of glucose to G3P (glyceraldehyde-3-phosphate)

• Electron carrier NAD+ (nicotinamide adenine dinucleotide) is reduced to NADH

• Step 7 dephosphorylates C-1 to make ATP (2x)

• Step 9 releases H2O• Step 10 dephosphorylates C-3

producing ATP and Pyruvate (2x)• What produce to respiration do we

not see yet?– CO2

Glucose+ 2ADP+ 2Pi + 2 NAD+ 2Pyruvate+ 2NADH+ 2H++ 4ATP

Regulation of Glycolysis• What molecule would best regulate

glycolysis?– ATP levels

• If ATP levels are high, phosphofructokinase in step 3

• What else could regulate it?– NADH levels

• Why does alcohol make you fat?– Breaking down alcohol boosts NADH

levels in liver cells– NADH stops glycolysis so sugars are

converted to glycogen– Alcohol enters Citric acid cycle as acetyl-

CoA– Prolonged high NADH levels and extra

acetyl-CoA create fatty acids which get stored in adipose cells (fat cells)

Pyruvate Oxidation

• Active transport pulls pyruvate into the mitochondrial matrix

• -COO- is removed as CO2

• 2-C acetyl binds to coenzyme A to make acetyl-CoA; which can enter the citric acid cycle

• 2 electrons are also passed on to NADH

2Pyruvate+ 2CoA+ 2NAD+ 2acetyl-CoA+ 2NADH+ 2H++ 2CO2

Citric Acid Cycle (Krebs Cycle)

• 8 reactions in a cycle convert acetyl-CoA into CO2 and recycle the CoA

• Steps 1 and 7 need H2O

• Steps 3 and 4 release CO2

• Steps 3, 4, and 8 release NADH

• Step 6 releases FADH2 (flavin adenine dinuclotide)

• Cycle runs twice for each glucose used

• What can inhibit the cycle?– ATP levels

1Acetyl-CoA+ 3NAD++ 1FAD+ 1ADP+ 1Pi+ 2H2O 2CO2+ 3NADH+ 1FADH2+ 1ATP+ 3H++ 1CoA

Alternative Energy Sources• Triglycerides (fats) are

hydrolyzed into glycerol and then G3P (step 6 in glycolysis)

• Triglycerides (fats) are broken into 2-C units and bind with CoA

• Fats are great source of energy but take longer to breakdown

• Proteins are broken into AA and then change into pyruvate or an intermediate step in the citric acid cycle

Oxidative Phosphorylation• Electron Transport Chain• All NADH/FADH2 bring

collected electrons/protons to the inner mitochondrial membrane

• Protein complexes I-IV use Cytochrome C and Ubiquinone to transfer electrons through the system

• The energy released actively pumps H+ outside of the matrix

• Concentration gradient powers ATP synthase like water powers a turbine to make ATP

The Complexes• Complexes I, III, and IV use

cytochrome c and coenzyme Q (ubiquinone) to move electrons

• Cytochromes have a Fe2+ to act as the electron acceptor/donor

• Complex IV is the irreversible binding site of cyanide and is inhibited by CO too

• Complex II contains the enzyme succinate dehydrogenase (step 6 of the Krebs cycle) and uses FADH2

• After Complex IV, the electrons are passed on to O with two H+ to produce H2O

Chemiosmosis and ATP Synthase• Proton-motive Force

electrochemical gradient of protons used to power ATP synthase

• H+ fall down gradient through chemiosmosis and cause a conformational change in ATP synthase that forces ADP and Pi to bind together

• 1 NADH 2.5 ATP• 1 FADH21.5 ATP• Total the ATP:

– Glycolysis= 2 ATP– Krebs Cycle= 2 ATP– Oxidative Phosphorylation= 28 ATPTotal = 32 ATP

Energy Efficiency• Some cells only produce 30 ATP

– Less efficient electron transporter (FADH) is used in glycolysis

– Found in brain tissue and skeletal muscles

• What type of tissue use the more efficient 32 ATP system?– Constantly active organs like the

heart, liver and kidneys• How do muscles compensate their

ATP needs since they have a less efficient system?– Lactic acid Fermentation

• ATP 7 kcal/mol• Glucose 686 kcal/mol• How efficient is this whole process?

– 33% ((7x322)/686)x100

FADHFADH

Aerobic and Anaerobic Reactions• Organism can be:

– Strict anaerobes can’t survive in oxygen

– Strict aerobes can’t survive without oxygen

– Facultative aerobes can survive with or without oxygen

• What parts of cellular respiration are aerobic/anaerobic?– Aerobic Krebs cycle/Oxidative

Phosphorylation– Anaerobic Glycolysis

• Anaerobic Organism can still do glycolysis, but what is left at the end?– pyruvate

• Breaking down pyruvate after glycolysis creates different kinds of fermentation

Fermentation• Alcoholic pyruvate is

converted into ethanol (alcohol and fuel) and released from the cell

• Also releases CO2; used to make bread/cakes raise

• Lactic Acid pyruvate is converted into lactate

• Used to flavor yogurt• Energy supply in muscles when

oxygen runs low• Why is it dangerous to us?

– Builds up in cells and lowers pH (acidic)

– Causes muscle crams and soreness after working out

– Must be removed from the cells and broken down in the liver

Homework• Read Ch. 9 and do Ch. 9

vocab• Ch. 8 vocab due Tuesday• Ch 8. “Test Your Knowledge”

and “Interpret the Data” p.175 for Tuesday

• Ch. 7 “Test Your Knowledge” on p. 153-154 and “Design the Experiment” on p. 154 due Tuesday

• Test on Ch. 6, 7, and 8 on Wednesday

• Lab on photosynthesis on Wednesday

• Ch. 9, 10 and 11 still to cover!