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AP Biology 2005-2006
The Point is to Make ATP!
ATP
Making energy!
AP Biology
Chapter 9 Warm-Up Define:
Glycolysis Respiration Chemiosmosis Phosphorylation Fermentation Electrochemical
gradient FAD FADH2
NAD+ NADH
Explain “glycolysis”. Where does it occur? How does it “work”?
AP Biology
Chapter 9 Warm-up What is the chemical equation for
cellular respiration? Remember OILRIG
In the conversion of glucose and oxygen to CO2 and H2O, which molecule is reduced?
Which is oxidized? What happens to the energy that is
released in this redox reaction?
NAD+ is called a(n) ________________.
Its reduced form is _________.
AP Biology
Chapter 9 Warm-Up Why is glycolysis considered an
ancient metabolic process? Where in the cell does glycolysis
occur? What are the reactants and products of
glycolysis? Which has more energy available:
ADP or ATP? NAD+ or NADH? FAD+ or FADH2?
AP Biology
Chapter 9 Warm-Up Where does the Citric Acid Cycle occur in
the cell? What are the main products of the CAC? How is the proton gradient generated? What is the purpose? Describe how ATP synthase works. In cellular respiration, how many ATP are
generated through Substrate-level phosphorylation? Oxidative phosphorylation?
AP Biology
Chapter 9 Warm-Up In fermentation, how is NAD+ recycled?
AP Biology
What you need to know:
The summary equation of cellular respiration. The difference between fermentation and cellular
respiration. The role of glycolysis in oxidizing glucose to two
molecules of pyruvate. The process that brings pyruvate from the
cytosol into the mitochondria and introduces it into the citric acid cycle.
How the process of chemiosmosis utilizes the electrons from NADH and FADH2 to produce ATP.
AP Biology
Chapter 9.Cellular Respiration and
Fermentation
AP Biology
The Point is to Make ATP!
ATP
What’s the point?
AP Biology 2005-2006
Harvesting stored energy Energy is stored in organic molecules
heterotrophs eat food (organic molecules) digest organic molecules
serve as raw materials for building & fuels for energy
controlled release of energy series of step-by-step enzyme-controlled reactions
“burning” fuels carbohydrates, lipids, proteins, nucleic acids
AP Biology 2005-2006
Harvesting energy stored in glucose Glucose is the model
catabolism of glucose to produce ATP
glucose + oxygen carbon + water + energydioxide
C6H12O6 6O26CO2 6H2O ATP+ + + + heat
CO2 + H2O + heatfuel
(carbohydrates)
combustion = making heat energy by burning fuels in one step
respiration = making ATP (& less heat)by burning fuels in many small steps
ATP
CO2 + H2O + ATP (+ heat)
res
pir
ati
on
AP Biology 2005-2006
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
AP Biology 2005-2006
How do we move electrons in biology? Moving electrons
in living systems, electrons do not move alone electrons move as part of H atom
+
H
+H
+ –loses e- gains e- oxidized reduced
oxidation reduction
C6H12O6 6O2 6CO2 6H2O ATP+ + +
oxidation
reductionH
AP Biology 2005-2006
Coupling oxidation & reduction Redox reactions in respiration
release energy as breakdown molecules break C-C bonds strip off electrons from C-H bonds by removing H atoms
C6H12O6 CO2 = fuel has been oxidized
electrons attracted to more electronegative atoms
in biology, the most electronegative atom? O2 H2O = oxygen has been reduced
release energy to synthesize ATP
C6H12O6 6O2 6CO2 6H2O ATP+ + +
oxidation
reduction
O2
AP Biology
Oxidation & reduction Oxidation
removing H loss of electrons releases energy exergonic
Reduction adding H gain of electrons stores energy endergonic
C6H12O6 6O2 6CO2 6H2O ATP+ + +
oxidation
reduction
AP Biology 2005-2006
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. Kreb’s cycle 4. Electron transport chain
C6H12O6 6O2 6CO2 6H2O ATP+ + + (+ heat)
AP Biology
The Point is to Make ATP!
ATP
What’s the point?
AP Biology
Glycolysis “sugar splitting” Believed to be ancient (early
prokaryotes- no O2 available)
Occurs in cytosol Partially oxidizes glucose (6C) to 2
pyruvates (3C) Net gain: 2 ATP and 2 NADH
Also makes 2H2O
No O2 required
AP Biology
Glycolysis Breaking down glucose
“glyco – lysis” (splitting sugar)
most ancient form of energy capture starting point for all cellular respiration
inefficient generate only 2 ATP for every 1 glucose
in cytosol why does that make evolutionary sense?
glucose pyruvate2x6C 3C
AP Biology 2005-2006
Evolutionary perspective Life on Earth first evolved without
free oxygen (O2) in atmosphere energy had to be captured from
organic molecules in absence of O2
Organisms that evolved glycolysis are ancestors of all modern life all organisms still utilize
glycolysis
You mean, I’m related to them?!
AP Biology
Glycolysis Stage 1: Energy Investment Stage
Cell uses ATP to phosphorylate compounds of glucose
Stage 2: Energy Payoff Stage Two 3-C compounds oxidized For each glucose molecule:
2 Net ATP produced by substrate-level phosphorylation
2 molecules of NAD+ NADH
AP Biology 2005-2006
glucoseC-C-C-C-C-C
fructose-6PP-C-C-C-C-C-C-P
DHAPP-C-C-C
PGALC-C-C-P
pyruvateC-C-C
2 ATP2 ADP
2 NAD+
2 NADH4 ADP4 ATP
Overview10 reactions
convert 6C glucose to two 3C pyruvate
produce 2 ATP & 2 NADH
activationenergy
Substrate level phosphorylation
AP Biology
Glycolysis summary
endergonicinvest some ATP
exergonicharvest a little more ATP& a little NADH
AP Biology 2005-2006
Substrate-level Phosphorylation In the last step of glycolysis, where
did the P come from to make ATP?
P is transferred from PEP to ADP kinase enzyme ADP ATP
I get it!The P came
directly from the
substrate!
AP Biology
Energy accounting of glycolysis
Net gain = 2 ATP some energy investment (2 ATP) small energy return (4 ATP)
1 6C sugar 2 3C sugars
2 ATP 2 ADP
4 ADP 4 ATP
glucose pyruvate2x6C 3C
All that work! And that’s all I
get?
AP Biology
Is that all there is? Not a lot of energy…
for 1 billon years+ this is how life on Earth survived only harvest 3.5% of energy stored in glucose slow growth, slow reproduction
Heck of a way to make a living!
AP Biology 2005-2006
We can’t stop there….
Going to run out of NAD+
How is NADH recycled to NAD+? without regenerating NAD+,
energy production would stop another molecule must
accept H from NADH
glucose + 2ADP + 2Pi + 2 NAD+ 2 pyruvate + 2ATP + 2NADH
Glycolysis
NADH
AP Biology
How is NADH recycled to NAD+? Another molecule must accept H from NADH
anaerobic respiration ethanol fermentation lactic acid fermentation
aerobic respiration
NADH
AP Biology 2005-2006
Anaerobic ethanol fermentation Bacteria, yeast
1C3C 2Cpyruvate ethanol + CO2
Animals, some fungi
pyruvate lactic acid3C 3C
beer, wine, bread at ~12% ethanol, kills yeast
cheese, yogurt, anaerobic exercise (no O2)
NADH NAD+
NADH NAD+
AP Biology
Pyruvate is a branching pointPyruvate
O2O2
Kreb’s cyclemitochondria
fermentation
AP Biology
Glycolysis (summary)
AP Biology
The Point is to Make ATP!
ATP
What’s the point?
AP Biology
Mitochondrion Structure
AP Biology
Cellular Respiration
AP Biology
Glycolysis is only the start
3C 1C
AP Biology
Oxidation of pyruvate Pyruvate enters mitochondria
3 step oxidation process releases 1 CO2 (count the carbons!) reduces NAD NADH (stores energy) produces acetyl CoA
Acetyl CoA enters Krebs cycle where does CO2 go?
Waiting to exhale?
NAD NADH
3C 2C 1C
pyruvate acetyl CoA + CO2[2x ]
AP Biology
Pyruvate oxidized to Acetyl CoA
Yield = 2C sugar + CO2 + NADH
reduction
oxidation
AP Biology
Krebs cycle
AP Biology
4C
6C
4C
4C
4C
2C
6C
5C
4C
CO2
CO2
citrate
acetyl CoACount the carbons and electron carriers!
x2
3Cpyruvate
reduction of electroncarriers and
oxidation of sugars NADH
NADH
FADH2
NADH
ATP
This happens twice for each glucose molecule
AP Biology 2005-2006
So we fully oxidized glucose
C6H12O6
CO2
& ended up with 4 ATP!
Whassup?
What’s thePoint?
AP Biology 2005-2006
Krebs cycle produces large quantities of electron carriers NADH FADH2
stored energy! go to ETC
NADH & FADH2
What’s soimportant
about NADH?
AP Biology
Citric Acid Cycle (Krebs) Occurs in mitochondrial matrix Acetyl CoA→ Citrate→
Net gain: 2 ATP, 6 NADH, 2 FADH2 (electron carrier)
ATP produced by substrate-level phosphorylation
CO2
CO2
AP Biology
So why the Krebs cycle? If the yield is only 2 ATP, then why?
value of NADH & FADH2
electron carriers reduced molecules store energy! to be used in the Electron Transport Chain
AP Biology
The Point is to Make ATP!
ATP
What’s the point?
AP Biology
Cellular respiration
AP Biology
ATP accounting so far… Glycolysis 2 ATP Kreb’s cycle 2 ATP
Life takes a lot of energy to run, need to extract more energy than 4 ATP!
There’s got to be a better way!
What’s thePoint?
AP Biology
There is a better way! Electron Transport Chain
series of molecules built into inner mitochondrial membrane mostly transport proteins
transport of electrons down ETC linked to ATP synthesis
yields ~34 ATP from 1 glucose! only in presence of O2 (aerobic)
Thatsounds more
like it!
AP Biology
Mitochondria Double membrane
outer membrane inner membrane
highly folded cristae* fluid-filled space
between membranes = intermembrane space
matrix central fluid-filled space
* form fits function!
AP Biology
Electron Transport Chain
AP Biology 2005-2006
PGAL
GlycolysisKreb’s cycle
2 NADH
8 NADH2 FADH2
Remember the NADH?
AP Biology
Electron Transport Chain NADH passes electrons to ETC
H cleaved off NADH & FADH2
electrons stripped from H atoms H+ (H ions) electrons passed from one electron carrier to next in
mitochondrial membrane (ETC) transport proteins in membrane pump H+ across inner
membrane to intermembrane space
AP Biology
But what “pulls” the electrons down the ETC?
electrons flowdownhill to
O2
AP Biology 2005-2006
Electrons flow downhill Electrons move in steps from
carrier to carrier downhill to O2
each carrier more electronegative controlled oxidation controlled release of energy
AP Biology 2005-2006
Why the build up H+? ATP synthase
enzyme in inner membrane of mitochondria
ADP + Pi ATP
only channel permeable to H+ H+ flow down concentration
gradient = provides energy for ATP synthesis
molecular power generator! flow like water over water wheel flowing H+ cause change in
shape of ATP synthase enzyme powers bonding of Pi to ADP
“proton-motive” force
AP Biology 2005-2006
Chemiosmosis couples ETC to ATP synthesis build up of H+ gradient just so H+ could flow through
ATP synthase enzyme to build ATP
ATP synthesis
So that’sthe point!
Oxidative phosphorylation
AP Biology
Summary of cellular respiration
Where did the glucose come from? Where did the O2 come from? Where did the CO2 come from? Where did the H2O come from? Where did the ATP come from? What else is produced that is not listed
in this equation? Why do we breathe?
C6H12O6 6O2 6CO2 6H2O ~36 ATP+ + +
AP Biology
Taking it beyond… What is the final electron acceptor in
electron transport chain?
O2
So what happens if O2 unavailable?
ETC backs up ATP production ceases cells run out of energy and you die!
AP Biology
The Point is to Make ATP!
ATP
What’s the point?
AP Biology
Any Questions??
AP Biology
Glycolysis
Fermentation Keep glycolysis going
by regenerating NAD+
Occurs in cytosol No oxygen needed Creates ethanol [+
CO2] or lactate
2 ATP (from glycolysis)
Respiration Release E from
breakdown of food with O2
Occurs in mitochondria
O2 required (final electron acceptor)
Produces CO2, H2O and up to 32 ATP
O2 presentWithout O2Without O2
AP Biology
Various sources of fuel
Carbohydrates, fats and proteins can ALL be used as fuel for cellular respiration
Monomers enter glycolysis or citric acid cycle at different points
AP Biology
pyruvate oxidation
ENERGY
glycolysis(cytosol)
glycolysis(cytosol)
ethanol + CO2
(yeast, some bacteria)
ethanol + CO2
(yeast, some bacteria)
anaerobic (without O2)
aerobic cellular respiration
(with O2)
lactic acid(animals)
lactic acid(animals)
ETCETC
chemiosmosischemiosmosis
oxidative phosphorylation
oxidative phosphorylation
citric acid cycle
citric acid cycle
mitochondria Fermentation(cytosol)
Fermentation(cytosol)