Chapter 6 Cellular Respiration
Chapter 6 Cellular Respiration
C6H12O6 + 6O2 6CO2 + 6H2O + 36 ATP
glucose + oxygen ( carbon dioxide + water + energy
• Living things need energy to carry on life activities
o making complex compounds from simpler ones.
o moving some materials across membranes
o cells need energy just to stay alive.
• chemical energy is stored in food
• carbohydrates most commonly broken down for energy
• some energy is released as heat
• rest of energy from food stored in chemical form
• cellular respiration is an energy releasing process which takes place in all living things.
o both autotrophic and heterotrophic organisms
• ATP and ADP
• Adenosine triphosphate – high energy
• adenosine diphosphate – low energy
• structure of ATP
• Energy cycle of the cell
• ATP supplies the cell with the energy needed for cell work
• glucose is broken down
• energy is released
• energy used to attach a third phosphate to ADP
• energy is released when the third phosphate is detached from ATP
• ADP is regenerated for reuse.[pic]
ENERGY:
• A continuous supply is needed for cells to stay alive
• carbohydrates – glucose- foods most commonly broken down for energy
• energy is released when food(fuel) is burned
• energy is released by chemical changes
• energy is released partially as heat – maintains body temperature
• energy releasing process is called cellular respiration
• energy is used by cells in the form of ATP
• ATP is packaged for slow gradual use
• ATP is adenosine triphosphate
• high energy bonds link phosphates to each other
• energy is transferred to another compound when the last phosphate group is removed and bonds to another compound
• Phosphorylation = transfer of energy from one compound to another – it is how energy is transferred in living cells
• when ATP is hydrolyzed (broken down ) – energy is released
• ADP has less energy than ATP
• Cellular respiration is a biochemical pathway
o a biochemical pathway is a sequence of chemical reactions that leads to a particular result in a living cell.
• Chemical reactions of cellular respiration require specific enzymes
• each enzyme requires the action of a COENZYME.
• the coenzyme acts as a hydrogen acceptor
• the coenzyme gains energy because it is carrying an extra hydrogen and electrons.
• Coenzymes of cellular respiration are:
o NAD+ nicotinamide adenine dinucleotide
o FAD flavin adenine dinucleotide
o each accepts hydrogen atoms
o in cellular respiration glucose is oxidized (loses electrons)
• Stages of cellular respiration
o glycolysis – does not require the presence of oxygen ever!
▪ takes place in the cytoplasm in ALL living things
▪ requires an investment of 2 ATP
▪ glucose is split into 2 three carbon sugars called PGAL (phosphoglyceraldehyde)
▪ through a series of enzyme catalyzed reactions, PGAL is converted to pyruvic acid and generates NADH and ATP during these reactions.
▪ produces as end products
• 2NADH ( hydrogen acceptors – coenzymes – energy carriers to the electron transport chain in the mitochondria)
• 2ATP (net gain)
• 2 pyruvic acid molecules
IF OXYGEN IS PRESENT PYRUVIC ACID ALONG WITH OXYGEN GOES TO THE MITOCHONDRIA FOR THE COMPLETION OF AEROBIC RESPIRATION:
• Aerobic cellular respiration
o oxygen present
▪ pyruvic acid along with oxygen enter the mitochondria
▪ pyruvic acid molecules are broken down to yield CO2, and acetyl coenzyme A (acetyl CoA)
▪ Acetly Co A enters the Krebs cycle reacting with oxaloacetate in the matrix of the mitochondria.
KREBS CYCLE: takes place in the mitochondrial matrix.
▪ each turn of krebs needs 1 molecule of aceyl Co A and yields 2 molecules of CO2 and 4 pair of H+ atoms
▪ H+ atoms are picked up by NAD+ and another energy carrier (hydrogen acceptor) FAD.
▪ NAD+ ( NADH
▪ FAD ( FADH2
▪ both of these hydrogen acceptors carry energy to the electron transport chain.
▪ Yields: 2 turns (one for each pyruvic acid)
• 2 ATP
• NADH
• FADH2
• CO2
ELECTRON TRANSPORT CHAIN: takes place in the inner membrane of the mitochondria.
• energy releasing reactions
• organized system of enzymes and coenzymes in the inner mitochondrial membrane are involved
• NADH and FADH2 carry H+ into the ETC
• electrons from H+ are passed from one compound to another
• hydrogens give up electrons along the chain and molecules of ATP are formed from the energy released.
• H+ gradient formed and as they fall through ATP ase , an enzyme complex in the mitochondrial inner membrane, down the concentration gradient – the energy is used to convert ADP to ATP.
• oxygen is the final hydrogen acceptor at the end of the chain forming water. This is the “water of metabolism”.
• net result is a total gain of 32 molecules of ATP
o 32 ATP from electron transport
o 2 from Krebs
o 2 from glycolysis
o total = 36 molecules from aerobic cellular respiration
IF OXYGEN IS ABSENT AND NO MITOCHONDRIA ARE PRESENT :
Pyruvic acid undergoes fermentation.
• Anaeorbic respiration – fermentation
• fermentation is the process where is no further release of energy after glycolysis.
• takes place in the absence of oxygen
• bacteria, yeast and muscle cells depleted of oxygen
o Two Types of anaerobic respiration/ fermentation:
▪ lactic acid fermentation – pyruvic acid in the absence of oxygen is converted to lactic acid.
• bacteria – yogurt
• muscle cells - cramps
▪ ethyl alcohol fermentation – pyruvic acid in the absence of oxygen is converted to ethyl alcohol and carbon dioxide.
• yeast – beer and wine
• yeast – bread
• does not involve oxygen
• only ATP produced is the result of glycolysis
Tremendous amount of stored potential energy still locked up in the products of fermentation. Not as efficient as aerobic respiration.
[pic]
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breakdown of glucose
ADP + P
ATP
Cell Activities
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