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AP Biology
Cellular Respiration Harvesting Chemical Energy
ATP
AP Biology
What’s the point?
The point is to make
ATP!
ATP
AP Biology
Chemical Energy: Food is to a cell (plant or animal), what gas is to a car.
AP Biology
Which Smiley Face has the most potential energy? Kinetic energy?
AP Biology
An overview of Cellular Respiration
2 ATP
34 ATP
AP Biology
B. Aerobically; efficient. Occurs in the mitochondria. ( used in Kreb’s & ETC)
AP Biology
Aerobic or anaerobic pathways? How do you know?
AP Biology
AP Biology
Where in a chemical bond is the potential energy? A) protons
B) neutrons C) electrons
*most biological redox rxns. have to do w/ the loss or gain of Hydrogen atoms and their electrons (e-); Potential Energy! *redox rxns. are always coupled; that is, when one molecule is oxidized, the other is reduced. “hand & glove”
AP Biology
*Liberated H atoms are transferred to other molecules by coenzymes " electron shuttle busses" 2 coenzymes commonly used by the cell: * NAD+ … derived from vitamin B niacin * FAD2+ ....derived from B2 riboflavin
AP Biology
H atom from chemical bonds. Have much Potential energy to
do WORK!
Oxidation - Reduction Rxn.
Remember:
AP Biology
Redox Football
Electron (H atom)
Which molecule is oxidized? Which is Reduced?
Where does the potential energy carried by NADH end up?
AP Biology
Where does the potential energy carried by NADH end up?
AP Biology
Energy Extraction Pathways
AP Biology
Coenzymes (vitamins) - are electron shuttle busses -
they lose & gain H(e-) atoms which are stripped from bonds of food molecules.
AP Biology
AP Biology
Conversions of the Metabolic Pathways- all foods have the
same fate…. The metabolic Mill!
proteins carbos fats
AP Biology
Energy is stored in organic molecules carbohydrates, fats, proteins
Heterotrophs eat these organic molecules → food digest organic molecules to get…
raw materials for synthesis fuels for energy
controlled release of energy “burning” fuels in a series of
step-by-step enzyme-controlled reactions
Harvesting stored energy:
AP Biology
AP Biology
Glucose is the model catabolism of glucose to produce ATP
fuel (carbohydrates)
COMBUSTION = making a lot of heat energy by burning fuels in one step
C6H12O6 6O2 ATP 6H2O 6CO2 → + + +
glucose + oxygen → energy + water + carbon dioxide
resp
iratio
n
+ heat
CO2 + H2O + heat
RESPIRATION = making ATP (& some heat) by burning fuels in many small steps
CO2 + H2O + ATP (+ heat)
ATP glucose
O2
O2
enzymes ATP
Harvesting stored energy:
AP Biology
How do we harvest energy from fuels? Digest large molecules into smaller ones
break bonds & move electrons from one molecule to another as electrons move they “carry energy” with them that energy is stored in another bond,
released as heat or harvested to make ATP
e-
+ + e-
+ – loses e- gains e- oxidized reduced
oxidation reduction
redox
e-
AP Biology
How do we move electrons in biology? Moving electrons in living systems
electrons cannot move alone in cells electrons move as part of H atom move H = move electrons
p e
+
H
+ H
+ – loses e- gains e- oxidized reduced
oxidation reduction
C6H12O6 6O2 6CO2 6H2O ATP → + + + oxidation
reduction H e-
AP Biology
Coupling oxidation & reduction: REDOX reactions in respiration
release energy as breakdown organic molecules break C-C bonds strip off electrons from C-H bonds by removing H atoms
C6H12O6 → CO2 = the fuel has been oxidized electrons attracted to more electronegative atoms
in biology, the most electronegative atom? O2 → H2O = oxygen has been reduced
couple REDOX reactions & use the released energy to synthesize ATP
C6H12O6 6O2 6CO2 6H2O ATP → + + + oxidation
reduction
O2
AP Biology
Oxidation & reduction: Oxidation
adding O removing H loss of electrons releases energy exergonic
Reduction removing O adding H gain of electrons stores energy endergonic
C6H12O6 6O2 6CO2 6H2O ATP → + + + oxidation
reduction
AP Biology
Moving electrons in respiration: Electron carriers move electrons by
shuttling H atoms around NAD+ → NADH (reduced) FAD+2 → FADH2 (reduced)
reducing power!
+ H reduction
oxidation
P O–
O–
O –O
P O–
O–
O –O
C C
O
NH2 N+
H
adenine
ribose sugar
phosphates
NAD+ nicotinamide Vitamin B3 niacin
P O–
O–
O –O
P O–
O–
O –O
C C
O
NH2 N+
H NADH
carries electrons as a reduced molecule
H
like $$ in the bank
AP Biology
NAD+ as an electron shuttle bus: NAD+
2 e− + 2 H+
2[H] (from food)
Nicotinamide (oxidized form)
Reduction of NAD+
2 e− + H+
NADH
Nicotinamide (reduced form)
Oxidation of NADH H+
H+
Dehydrogenase
H+
H+ H+
H+
H+ H+ H+ H+
H+
ATP
To mitochondrial
membranes (Proton Motive
Force)
AP Biology
Electron carriers move electrons by shuttling H atoms around NAD+ → NADH (reduced); Count the e- + proton(H+) = 1 H atom
✔
✔
✔
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Overview of cellular respiration: 4 metabolic stages
Anaerobic respiration 1. Glycolysis
respiration without O2 in cytosol
Aerobic respiration respiration using O2
in mitochondria 2. Pyruvate oxidation 3. Krebs cycle 4. Oxidative phosphorylation & ETC
C6H12O6 6O2 ATP 6H2O 6CO2 → + + + (+ heat)
Substrate-level Phosphorylation
Substrate-level Phosphorylation
Oxidative Phosphorylation
~90% of ATP
AP Biology
An overview of cellular respiration:
Electrons via NADH
Electrons via NADH and FADH2
ATP ATP ATP
CYTOSOL MITOCHONDRION
Substrate-level Substrate-level Oxidative (Powered by redox)
GLYCOLYSIS PYRUVATE OXIDATION CITRIC
ACID CYCLE
OXIDATIVE PHOSPHORYLATION
(Electron transport and chemiosmosis)
Acetyl CoA Glucose Pyruvate
Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration!
AP Biology
A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation.
Enzyme Enzyme
Substrate
Product
ATP
ADP
P
Substrate-level Phosphorylation
Substrate-level Phosphorylation
AP Biology
Example: Substrate-level phosphorylation during Glycolysis
GLYCOLYSIS: Energy Payoff Phase
Glycer- aldehyde
3-phosphate (G3P)
Triose phosphate
dehydrogenase
6 1,3-Bisphospho- glycerate
3-Phospho- glycerate
2-Phospho- glycerate
Phosphoenol- pyruvate (PEP)
Pyruvate
Phospho- glycerokinase
Phospho- glyceromutase
Enolase Pyruvate kinase
2 NAD+
7 8 9 10
2 NADH + 2 H+
2
2
2 2
2 2 2 2
2
2 2 H2O ATP ATP ADP ADP
Which step #(s) is ATP made by Substrate-level phosphorylation?
AP Biology
What’s the point?
The point is to make
ATP!
ATP
AP Biology
ATP synthase enzyme H+ flows through it
conformational changes
bond Pi to ADP to make ATP
set up a H+ gradient allow the H+ to flow
down concentration gradient through ATP synthase
ADP + Pi → ATP H+
H+ H+
H+
H+ H+ H+ H+
H+
ATP ADP P +
But… How is the proton (H+) gradient formed?
And how do we do that?
AP Biology 2006-2007 H+
H+ H+
H+
H+ H+ H+ H+
H+
ATP
Got to wait until the sequel!
Got the Energy? Ask Questions!
ADP P +