Alberts • Bray • Hopkin • Johnson • Lewis • Raff • Roberts • Walter
Essential
Cell Biology
FOURTH EDITION
Chapter 13
How Cells Obtain Energy From Food
Copyright © Garland Science 2014
Catabolism Occurs
in Three Stages
Fig. 13-3
Enzymes Allow Energy to be Extracted
from Food in Discrete Steps and Stored
in Activated Carrier Molecules
ATP
NADH
Fig. 13-1
Overview of Glycolysis
substrate level
phosphorylation
OxPhos
Fig. 13-4
Step 7
ATP production through
transfer of phosphate
from molecule with higher
energy phosphate bond
Step 10
Substrate Level Phosphorylation:
Glycolysis
Intermediates
energy investment: step 1
Fig. 13-8
Oxidative Phosphorylation: ATP production
powered by electron transfer in mitochondria
O2 final
e- acceptor
H+
H+
ATP
Fig. 13-2
NADH
NAD+
A little more detail….
Glucose Oxidized
NAD+ Reduced
ATP consumed
Set up for
ATP production
NADH production
(NAD+ regenerated by
ETC of mitochondria
in aerobic cells)
ATP production
exceeding
ATP consumption
Fig. 13-5
NAD+ regenerated by
fermentation in anaerobic cells
Can only produce ATP
by substrate level
phosphorylation
Fig. 13-6
Skeletal muscles contain both aerobic slow twitch
and anaerobic fast twitch muscle fibers.
fast
slow
Karp,CMB7
slow twitch: long duration, low intensity contractions (+ mitochondria)
fast twitch: short duration, high intensity contractions (- mitochondria)
Substrate Level Phosphorylation:
ATP production through
transfer of phosphate
from molecule with higher
energy phosphate bond
creatine phosphate
(~10.0)
stored in muscle
Fig. 13-8
Steps 6 & 7 Combined Generate Products for
ATP Synthesis by Both Mechanisms
OxPhos
Fig-139b
substrate level
Step 6 product can be used in substrate-level
phosphorylation in Step 7
Combined DG = - 3.0
DG = +1.5
DG = - 4.5
Panel 13-1
High-Energy Bond Created in Step 6 Provides
Energy for ATP Synthesis in Step 7
substrate level
phosphorylation
oxidized
in
OxPhos
Fig. 13-7
Details of High
Energy Bond
Set-up
Step 6:
-short-lived high energy
thioester bond formed between
Cys of enzyme and substrate
-electrons transferred from
substrate to NAD+
-high energy Pi bond replaces
high energy thioester bond
linking substrate to enzyme
Step 7:
-high energy Pi transferred
to ADP in ATP synthesis by
substrate-level phosphorylation
Fig. 13-9a
Step 10 Also Involves
Substrate-Level Phosphorylation
Panel 13-1
Pyruvate actively transported across inner mitochondrial
membrane (energy provided by H+ gradient across IMM, Ch 14)
Pyruvate Converted to Acetyl CoA and CO2 by
Pyruvate Dehydrogenase in Mitochondria
Fig. 13-10
large complex contains multiple
copies of enzymatic subunits
1 and 3 tethered to core subunit 2
Acetyl CoA is another activated energy carrier
that is derived from a ribonucleotide.
Allows acetyl group to be transferred
to other molecules in exergonic reaction
Fig. 3-36
Fats also enter
cycle as acetyl-CoA.
Citric Acid Cycle
acetyl group transferred
to oxaloacetate
NADH used in
ATP synthesis
by OxPhos
Fig. 13-12
Electron transport from NADH generates
H+ gradient during Oxidative Phosphorylation
ATP and NADH
activated carriers
produced
matrix
IMM
OMM
Fig. 13-19
Two Other Activated Carriers
Produced in Citric Acid Cycle
produced by SDH
embedded in IMM
GTP (ATP equivalent)
Fig. 13-13
FADH2 e- carrier
Krebs Used SDH Inhibitor to
Show Pathway is Cyclical
SDH
x
Malonate Inhibits
SDH Step
inhibitor type?
Fig. 13-15
Addition of either A-D or F-H caused accumulation
of E (Succinate) during inhibition.
Fig. 13-17
Hans Kreb proposed cyclical pathway
to explain both results (1953 Nobel Prize)
Fig. 13-18
O2 uptake increased
Glycolysis and Citric Acid Cycle Also
Provide Entry Points to Anabolic Pathways
also provide
entry points
for other C
sources for
catabolism
Fig. 13-14
Big Picture of
Metabolic Pathways
in Cells
Glycolysis and Citric
Acid Cycle in Red
Fig. 13-20
Regulating Catabolism vs. Anabolism:
allosteric modulation of key enzymes by ATP & AMP
Catabolism
starvation stimulates
Fig. 13-21
Anabolism
starvation inhibits
Gluconeogenesis-specific enzymes by-pass
irreversible reactions of glycolysis (steps 1, 3, & 10)
Excess Glucose Stored in Form
of Glycogen and Triacylglycerol
Acetyl-CoA
Fig. 13-22
Fig. 13-11