Biology 2581B Chapter 9: Chapter 9 Energy source
20 May 2020
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Chapter 9
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1. What is the structure of ATP (adenosine triphosphate)?
- Cell does 3 kinds of work
o Chemical work - pushing of endergonic reactions that would not occur spontaneously
e.g. synthesis of polymers from monomers
o Transport work - pumping of substances across membranes against
direction of spontaneous movement – ATP hydro leads to protein shape
change so it can bind substance
o Mechanical work e.g. beating of cilia, contraction of muscle cells &
movement of chromosomes during cellular reproduction – ATP
noncovalently binds to motor protein, hydrolysed, walks protein forward
- Energy coupling - use of exergonic process to drive an endergonic one
→ mostly mediated by ATP – mostly acts as immediate source of E
- ATP – ribose, nitrogenous base adenine & triphosphate group
- Hydrolysis can break bonds betw phosphate groups – addition of water, inorganic phosphate
leaves, creating adenosine (ribose + adenine) diphosphate → exergonic – E released comes
from chemical change of system to state of lower free E NOT phosphate bonds (high potential
E in bonds BUT they are not strong)
- ATP releases more E than other molecules could – all P groups neg charged → like charges
grouped together & repulsion creates instability
- ATP hydrolysis = exergonic – E can be used to perform endergonic reactions (if ΔG of
endergonic reaction < E ATP hydro – can be coupled to be overall exergonic) –
phosphorylation = transfer of P group from ATP to some other molecule e.g. reactant –
phosphorylated intermediate = recipient molecule w/ P covalently
bonded to it (more reactive (less stable, more free energy) than
original unphosphorylated molecule) – p.152
- ATP cycle - couples cell’s exergonic processes to endergonic
ones – regeneration ATP form ADP & Pi is endergonic & needs E from
body’s exergonic processes e.g. cellular respiration
2. What is energy? Types, laws, …
3. How do animal cells produce ATP? – look at bigger picture
- Each glucose – around 32 ATP produced
a. Glycolysis = sugar splitting – cytosol – occurs whether or not O2 is present
- begins degradation process by oxidising 1 glucose (6C) → 2 pyruvate (3C)
- E investment phase - transfer of Pi group of ATP to C3 intermediates
- E harvesting phase - ATP formed by substrate-level phosphorylation = enzyme transfers
phosphate from substrate (organic intermediate) to ADP rather than adding Pi
- 2 phases – E investment & E payoff = ATP produced by substrate-level phosphorylation &
NAD+ reduced to NADH by e- released from glucose oxidation
Chapter 9
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b. Pyruvate oxidation – mitochondria (cytosol for prokaryotes)
- Oxidation of pyruvate → acetyl CoA for Krebs cycle → further oxidation of acetyl CoA
c. Krebs/citric acid cycle – produces CO2 + ATP
- acetyl CoA→ CO2
d. Electron transport chain (ETC) – produces H2O
- accepts e-s transported from NADH or FADH2 generated during first 2 stages & passes them
down the chain - combined w/ molecular oxygen & hydrogen ions (H+ ) to form H2O – E stored
in form mitochondrion can make ATP from ADP from = oxidative phosphorylation (powered
by ETC redox reactions) – accounts for 90% ATP from cellular respiration
- e- move down the chain → losing E in several energy-releasing steps → e- passed to O2
reducing it to H2O
- Along ETC – e- transfer causes protein complexes to move H+ from mitochondrial matrix (in
eukaryotes) to intermembrane space → storing E as a proton-motive force (H+ gradient) - as
H+ diffuses back into matrix through ATP synthase, passage drives phosphorylation of ADP
to form ATP = chemiosmosis
- 34% of E stored in glucose molecule = transferred to ATP during cellular respiration →
producing maximum of about 32 ATP
Document Summary
Cell does 3 kinds of work: chemical work - pushing of endergonic reactions that would not occur spontaneously e. g. synthesis of polymers from monomers. Mostly mediated by atp mostly acts as immediate source of e. Atp ribose, nitrogenous base adenine & triphosphate group. Energy coupling - use of exergonic process to drive an endergonic one. E in bonds but they are not strong) Atp releases more e than other molecules could all p groups neg charged like charges grouped together & repulsion creates instability. Each glucose around 32 atp produced: glycolysis = sugar splitting cytosol occurs whether or not o2 is present. Begins degradation process by oxidising 1 glucose (6c) 2 pyruvate (3c) E investment phase - transfer of pi group of atp to c3 intermediates. E harvesting phase - atp formed by substrate-level phosphorylation = enzyme transfers phosphate from substrate (organic intermediate) to adp rather than adding pi.
