* Respiration (Ch 21) Flashcards
Burning vs respiration
Similarities
- Oxygen is needed in burning and aerobic respiration, anaerobic respiration can take place in absence of oxygen
- Both produces carbon dioxide and water
- Both releases energy
Differences
Burning:
- a single step
- occurs everywhere
- no need enzymes
- energy released rapidly and uncontrolledly
- energy released in forms of light and heat
Respiration
- a series of chemical reactions
- occurs in living cells only
- need many enzymes
- energy released slowly, gradually in stepwise manner
- energy released in forms of ATP and heat
Mitochondria
Cristae membranes
- folding of inner membrane forms cristae
- membranous features increase surface area for holding electron transport chains and enzymes for ATP synthesis within limited amount of space
Circular DNA
- shows evidence of prokaryotic origin
- contains genes that code for some enzymes needed by mitochondria for energy transformation process
Cells having a lot of mitochondria to support their activities
- liver cells: provide large amount of energy to support numerous metabolic activities
- epithelial cells of small intestine: support active absorption of digested food
- rod cells of retina: provide energy to support regeneration of visual pigment
- sperm: supply energy for sperm to swim towards the egg
- muscle fibres: provide large amount of energy to support muscle contraction
- nerve fibres: resynthesis of neurotransmitter
Glycolysis
- In cytoplasm
- Glucose is stable that has to be activated by adding 2 ATP
- Glucose splits into two molecules of triose phosphate
- Each triose phosphate is oxidized to a pyruvate by losing hydrogen atoms
- The hydrogen atoms are accepted by hydrogen carrier NAD to from NADH
- Energy released in each oxidation process is used to form 2 ATP from 2 ADP and 2 phosphate groups
Krebs cycle
- In matrix of mitochondria
Link reaction
- Pyruvate loses a molecule of carbon dioxide, loses hydrogen atoms which are accepted by NAD to form NADH
- The remaining acetyl group temporarily combines with coenzyme A to from acetyl coenzyme A
Krebs cycle
- Acetyl-coA combines with 4-C compound to form a 6-C compound, coenzyme A is regenerated to accept other acetyl groups
- 6-C compound is oxidized in a step wise manner to regenerate 4-C compound which allows the cycle to sustain
- 2 molecules of carbon dioxide are released
- 4 pairs of hydrogen atoms are accepted by 3 molecules of NAD and 1 molecule of FAD to from 3 NADH and 1 FADH respectively
- 1 ATP is directly produced
Oxidative phosphorylation
- In inner membrane of mitochondrion
- When the electrons carried by NADH and FADH pass along the carriers of electron transport chain, a series of redox reactions occur
- The electron transport chain involves oxidation in removal of hydrogen atom and phosphorylation in formation of phosphate bonds in ATP
- Electrons are passed downhill to oxygen, energy released is used to form ATP from ADP and P
Role of oxygen in respiration
- The electrons and hydrogen atoms are accepted by oxygen to form water
- Oxygen is the final hydrogen acceptor, which accepts hydrogen atoms from NADH and FADH, regenerated NAD and FAD, which can be used as hydrogen carriers in glycolysis and Krebs cycle, sustaining glycolysis and Krebs cycle
Alcoholic fermentation
- Carried by yeasts and plants
- In absence of oxygen, pyruvate is reduced by NADH to form ethanol and carbon dioxide
- Pyruvate loses a molecule of carbon dioxide to form ethanal, which acts as final hydrogen acceptor to receive hydrogen atoms from NADH formed in glycolysis, regenrates NAD, glycolysis can sustain and produce ATP
- Product is ethanol
Lactic acid fermentation
- Pyruvate acts as final hydrogen acceptor that receives the hydrogen atoms from NADH formed in glycolysis, regenrates NAD, glycolysis can sustain to produce ATP
- Product is lactic acid
Lactic acid fermentation in skeletal muscle in human
- During vigorous exercises, though the human body increases rate and depth of breathing, oxygen delivered to muscles is still insufficient to support aerobic respiration fast enough to produce enough energy aerobically to meet all energy needed
- Skeletal muscles carry out anaerobic respiration to provide extra amount of energy within a short period of time to support more vigorous muscular contraction
- Lactic acid formed accumulates, causing muscle fatigue, muscles feel tired and fail to contract any more
Repaying oxygen debt
- After exercise, the rate and depth of breathing is still higher than normal
- Extra oxygen is taken in to break down lactic acid to provide additional amount of energy to convert lactic acid to glycogen for storage in liver
- Restore blood pH to normal
Aerobic respiration vs anaerobic respiration
Similarities
- Fate of pyruvate molecules generated in glycolysis
- Oxygen requirement
- End products
- Energy yield
Aerobic respiration vs alcohol fermentation
- Similarities
- Products
- Final hydrogen acceptor
- Krebs cycle
- Electron transport chain
- Oxidative phosphorylation
- Completion of oxidation of sugar
- Energy production
Interrelationship between photosynthesis and respiration
Flow of energy:
- During photosynthesis, producers captures solar energy and converts it to chemical energy, which is stored in form of complex organic matter
- Chemical energy is passed to consumers through feeding
- In respiration, organic compounds formed in photosynthesis will be broken down by oxidation to release energy in form of ATP to support energy-requiring activities
Compare and contrast: photosynthesis and respiration
- Energy transformation
- Reactions involved in energy transformation: activation process and products formed, electron transport system and ATP synthesis, further transformation of energy from ATP and NADPH in photosynthesis
