Energy and Respiration Flashcards
Outline the need of energy in living organisms:
1) ATP is the universal energy currency
2) Anabolic reactions: protein synthesis, triglyceride formation
3) Transport of substances across membranes: Active transport, exocytosis
4) Movement: muscle contraction, microtubules moving vesicles
5) Regulation of body temperature
6) Light energy for photosynthesis
7) Metabolism
Outline the structure of ATP:
- Adenosine triphosphate
- Three phosphate groups
- a ribose sugar (pentose)
- an adenine base
- Adenine + ribose = adenosine
What are the features of ATP?
1) Only releases a small amount of energy when hydrolysed: prevents waste
2) Quick hydrolysis: good for random demands for energy
3) Soluble: can be transported around body and cells
4) Stable molecule: can withstand range of pH’s
5) recyclable: reversible reaction of ATP —> ADP + Pi
How is ATP made? (2 ways)
1) Substrate-linked phosphorylation:
- direct formation of ATP from ADP + Pi, using energy from another chemical reaction
- occurs in cytosol/mitochondrial matrix
- in glycolysis and krebs cycle
- 4/6 ATP produced per glucose molecule
2) Chemiosmosis:
- ATP synthesis using energy released by movement of H+ ions down conc. gradient via ATP synthase
- occurs in inner membrane of mitochondria
- in oxidative phosphorylation
- 32/34 ATP produced per glucose molecule
What are the four stages of aerobic respiration and where do they occur?
1) Glycolysis: cell cytoplasm
2) Link Reaction: Mitochondrial matrix
3) Krebs cycle: Mitochondrial matrix
4) Oxidative phosphorylation: Inner membrane of mitochondria
Outline the process of glycolysis:
1) splitting of glucose AND phosphorylation:
- glucose (6C) —> fructose phosphate (6C) —> fructose 1,6 bisphosphate
- 2x ATP USED in this process
2) two molecules of triose phosphate (3C) ———> 2 molecules of Pyruvate (3C)
- 4x ATP PRODUCED in this process
- 2 molecules of NAD reduced (2NAD+ —> 2NADH + 2H)
Outline the process of Link Reaction:
- Pyruvate (3C) + CoA + NAD ————> Acetyl Coenzyme A (2C) + CO2 + reduced NAD
- Decarboxylation: 1x CO2 removed
- CoA (coenzyme A) added, which supples acetyl group
- Dehydrogenation: 1x NAD reduced
Outline the process of Krebs Cycle:
- Acetyl CoA (2C) combines with oxaloacetate (4C)
- forming citrate (6C)
- which is decarboxylated TWICE/CO2 released x2
- and dehydrogenated
- 3x NAD reduced
- 1x FAD reduced
- intermediates are produced (5C)
- 1x ATP produced by substrate level phosphorylation
- oxaloacetate regenerated
- enzyme catalysed reaction
Outline the process of oxidative phosphorylation:
- reduced NAD and FAD are transported to the ETC
- move from the mitochondrial matrix to inner membrane
- hydrogen removed from NAD and FAD (oxidized)
- Hydrogen atoms split into protons + electrons
- electrons pass along electron carriers of the ETC, energy is released every time
- energy released pumps protons into IMS
- this creates a proton gradient
- protons pass through protein channels back to matrix
- Chemiosmosis
- ATP synthase catalyses reaction of ADP + Pi —> ATP
- oxygen is final electron acceptor
- joins with H+ to form water/ O2 + 4H+ + 4e- —> 2H2O
Outline the role of the electron carrier NAD in aerobic respiration:
- NAD is a coenzyme for dehydrogenase
- it gets reduced
- carries electrons and protons/hydrogens
- from Krebs cycle, glycolysis and link reaction
- to the ETC at oxidative phosphorylation
- where NAD is reoxidised
- this process produces ATP
What is the net gain of ATP in each step of aerobic respiration? (per glucose molecule)
- Glycolysis: 2 (only reaction where 2x ATP is used)
- Link reaction: 0
- Krebs Cycle: 2
- Oxidative phosphorylation: 28
Outline the structure and function of a mitochondrion:
- 0.5-1.0 micrometers in diameter
- function is to make ATP
Outer membrane:
- permeable to pyruvate, reduced NAD and O2
Inner membrane:
- folded/cristae increases SA
- has ATP synthase
- has ETC
- site of oxidative phosphorylation
- impermeable to protons
Intermembrane space
- low pH
- protons pumped into IMS
- has proton gradient between IMS and matrix
Matrix
- contains (co)enzymes for link reaction and Krebs cycle
Outline the process of anaerobic respiration in mammals:
Glycolysis:
- glucose is converted to pyruvate (1x ATP produced)
Lactate fermentation:
- pyruvate is reduced (gains hydrogen from NADH) and converted to lactate
- so reduced NAD is reoxidised into NAD
Location: cytoplasm
Outline the process of anaerobic respiration in yeast:
Glycolysis
- glucose converted to pyruvate
Ethanol fermentation (2 steps)
- pyruvate decarboxylated to ethanal and one CO2 molecule released
- ethanal reduced to ethanol by ethanol dehydrogenase
- so reduced NAD reoxidised to NAD
What are the anaerobic adaptions of rice plants?
Rapid shoot growth
- leaves and flowers grow above water level
- quick access to oxygen
- growth regulated by gibberellin
Aerenchyma
- in stem and roots
- helps oxygen to diffuse to roots/submerged parts for aerobic respiration
Shallow roots
- air trapped on underwater leaves
tolerant to high ethanol concentrations
- so can respire anaerobically
high levels of ethanol dehydrogenase
- breakdown ethanol from anaerobic respiration
