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How Cells Release Stored Energy
Chapter 7
“Killer” Bees- Aggressive descendents of African honeybees that were imported to Brazil in the 1950s
– Africanized bee’s muscle cells have
enlarged __________________
•Photosynthesizers get energy from the ___•Animals get energy second- or third-hand
from ____ or other ____________•Regardless, the energy is converted to the
chemical bond energy of ____
ATP Is ____________ Energy Source
Making ATP• All organisms- breakdown of
carbohydrates, fats, and protein
– Plants only - during photosynthesis
O2 required?
Process
Location
____________________________
_____________________,__________
Aerobic Anaerobic
___ ___
Two pathways
Aerobic Respiration
C6H1206 + 6O2 6CO2 + 6H20 ________ ______ ______
______
________Glucose (C6H12O6)
a simple sugar
2 Pyruvate (three carbons)
6CO2
Glucose 2 Pyruvate 6 CO2
2 ADP 2 ____ 2 ADP 2 _____
8 NADH2 NAD+ 2 ______ 8 NAD+
2 FAD+ 2 FADH2
_______6 ADP 28 ADP _______
1. ________ 2. _______
3. _______ ________
Add up total ATP generated : 2+2+6+28=____
Aerobic Respiration
Overview of Aerobic RespirationCYTOPLASM
MITOCHONDRION
GLYCOLYSIS
ELECTRON TRANSPORT
PHOSPHORYLATION
KREBS CYCLE ATP
ATP
energy input to start reactions
2 CO2
4 CO2
2
32
water
2 NADH
8 NADH
2 FADH2
2 NADH 2 pyruvate
e- + H+
e- + oxygen
(2 ATP net)
glucose
TYPICAL ENERGY YIELD: 36 ATP
e-
e- + H+
e- + H+
ATP
H+
e- + H+
1. ________(In cytoplasm)
2. ____________(in mitochondrial matrix)
3. ______________ (In inner
mitochondrial membrane)
End result: ATP is generated
_________
___________
Each of _____ steps in glycolysis is catalyzed by a specific _______.
Divided into two phases: 1. an _____________
phase• 2 ATP used
2. an _____________ phase.• 4 ATP + 2 NADH
produced
Net yield in glycolysis= __ATP + __NADH
1. Glycolysis
The Role of Coenzymes
• ____ and ______ accept electrons and hydrogen …then deliver them to the ______
_________ system
Glucose 2 Pyruvate 6 CO2
2 ADP 2 ATP 2 ADP 2 ATP
8 NADH2 NAD+ 2 NADH 8 NAD+
2 FAD+ 2 FADH2
2. Krebs cycle
______________
• If __________ is present, pyruvate enters the _____________ where enzymes of the Krebs cycle complete the _________ of the organic fuel to carbon dioxide.
Glucose 2 Pyruvate 6 CO2
2 ADP 2 ATP 2 ADP 2 ATP
These are generated by ____________________________
Enzyme•An ______ transfers a phosphate group from an organic molecule (the substrate) to ____, forming ____-.
What is substrate level phosphorylation?
• The Krebs cycle consists of ____ steps.
Fig. 9.11
• Each cycle produces
• one ATP by ________________ ______________• three _________• and one _______
Named after Hans Kreb – 1930s
2. Krebs cycle
• The conversion of pyruvate and the Krebs cycle produces large quantities of _____________.
Fig. 9.12
2 carbon atoms enter
2 carbon atoms released as CO2
Note the Krebs cycle is never depleted of ______: 2 in, 2 out
8 NADH2 NAD+ ___________ 8 NAD+
2 FAD+ 2 FADH2
__________6 ADP 28 ADP __________
___________ ____________
Electron transport
Add up total ATP generated : 2+2+6+28=_____
3. Electron transport
Coenzymes deliver electrons to electron transport systems
in-text, p. 116
ELECTRON TRANSPORT PHOSPHORYLATION
glucose
pyruvate
KREBS CYCLE
GLYCOLYSIS
Electron transport
Mitochondria
• Coenzymes deliver _________ to ET chain• H+ ions are delivered to ______ compartment• H+ _________ is created• ___ is final _____________
NADH
OUTER COMPARTMENT
Inner compartment
O2H20
ET chain
4 important facts:
Making ATP: __________________ Model
ATP
ADP+Pi
INNER COMPARTMENT
• H+ ions going back to _______ compartment generates _______
Fig. 7.5b, p. 114
Krebs Cycle
NADH
NADH
NADH
ATP ATP
ATP
ATP
ADP + Pi
INNER COMPARTMENT
OUTER COMPARTMENT
acetyl-CoA
free oxygen
6 Following its gradients, H+ flows back into inner compartment, through ATP synthases. The flow drives ATP formation.
1 Pyruvate from cytoplasm enters inner mitochondrial compartment.
3 NADH and FADH2 give up electrons and H+ to membrane-bound electron transport systems.
2 Krebs cycle and preparatory steps: NAD+ and FADH2
accept electrons and hydrogen stripped from the pyruvate. ATP forms. Carbon dioxide forms.
5 Oxygen accepts electrons, joins with H+ to form water.
4 As electrons move through the transport system, H+ is pumped to outer compartment.
Overview of respiration
• How efficient is respiration in generating ATP?– Complete oxidation of glucose = ____
kcal/mole.– Formation of each ATP requires = _____
kcal/mole.– Efficiency of respiration is
– __ kcal/mole x -_ ATP/glucose = __%. 686 kcal/mole glucose
• The other approximately 60% is lost as ______.
• Cellular respiration is remarkably ________ in energy conversion.
• Glycolysis generates ______ whether oxygen is present (aerobic) or not (anaerobic).
____________ enables some cells to produce ATP without the use of _________
Fig. 9.17a
Problem- Fermentation (anaerobic catabolism) still requires NAD+ to accept electrons.
Solution-In __________________, NAD+ comes from the conversion of pyruvate to ______________
Ethanol
• A second solution to the NAD+ problem: – ___________________________
• ( pyruvate is reduced directly by NADH to form ___________)
– Muscle cells switch from ______ respiration to lactic acid f____________ to generate ATP when -____ is scarce.• The waste product,
lactate causes muscle fatigue but ultimately it is converted back to pyruvate in the liver.
Lactate
A third solution to the NAD+ problem
• Certain anaerobic bacteria solve NAD+ problem by using compounds from environment (such as nitrate), NOT oxygen
• ATP yield is low
Compare respiration and fermentation
Respiration Fermentation
•Both use glycolysis to generate __________•Both use NAD+ as an _________________.
Similarities
Aerobic AnaerobicType
NAD+ regeneration
Organic molecules___
Energy yield
___ ATP___ATP
• At a cellular level, human ______ cells can behave as facultative anaerobes, but __________ cells cannot.
Fig. 9.18
•For facultative ________________, pyruvate is a fork in the metabolic road that leads to two alternative routes. Ethanol or
lactate
7. How do other ________________ fit into glycolysis and the Kreb cycle??
Answer- _________,______________________________ can all enter the pathway.
•_____ are degraded to amino acids, then deaminated (nitrogen secreted as urea, ammonia)
•______ must be digested to glycerol and fatty acids.
•________ are broken down to glucose.
• Glucose absorbed by blood
• Pancreas releases insulin
• Insulin stimulates glucose uptake by cells
• Cells convert glucose to __________________
• This traps glucose in cytoplasm where it can be used for glycolysis
• If ATP _____, glucose stored as _________ in muscle and liver
If glucose is the key to ATP production, then how do we store glucose??
Answer- ___________ (in animals)_______ and _______ (in plants)
Animals
Using Glycogen• When blood glucose low, pancreas
releases _____________
• Glucagon stimulates liver cells to convert
glycogen back to glucose and to release it
to the blood
• (Muscle cells do not _____________ their
stored glycogen)
Energy Reserves• Glycogen- ___%
• Proteins- ___ %
• Fat – ____%
in-text, p. 122
sunlight energy
water+
carbondioxide
PHOTOSYNTHESIS
AEROBICRESPIRATION
sugarmolecules
oxygen
Linking photosynthesis and respiration