Download Riveting Respiration

Riveting Respiration
Chapter 9 notes
So Why do we Breathe????
Background
– Ultimate energy source for
ecosystems
 ATP – Usable cellular energy
 Chemical Energy – Energy stored in
chemical bonds
 Fermentation – Partial breakdown of sugar
WITHOUT using Oxygen
 Sun
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Cellular Respiration
 Complete
degrading (breakdown) of sugar
using Oxygen (catabolic process)
 Uses energy stored in food to make ATP

C6H12O6 + 6O2  6CO2 + 6H2O + Energy (ATP + heat)
 ΔG
= -686 kcal/mol – WOW!!!
 ATP will be used to drive other processes
that need energy through Phosphorylation
Redox Reactions
 Oxidation-Reduction
 Chemical
reaction where one or more
electrons are transferred from one
reactant to another
– loss of electron from
substance
 Reduction – Addition of electron to another
substance
 Oxidation
Redox Reactions
 Complete
transfer of electrons
 Na + Cl Na+ + Cl –
 Partial
transfer of electrons
 CH4 + 2O2 CO2 + Energy + 2H2O
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Redox Reactions
 When
an electron is transferred from a
less electronegative atom to a more
electronegative atom, energy is released
that can be used to do work
Redox Reactions
 For
respiration
 C6H12O6 + 6O2  6CO2 + 6H2O
 Glucose
is oxidized and oxygen is reduced
releasing lots of energy (remember
oxygen is VERY electronegative)
Respiration
 Performed
mainly on carbohydrates and
fats, but we will focus on GLUCOSE
 Activation energy prevents these high
energy goods from breaking down
spontaneously – so we will need
ENZYMES to make respiration happen
 Glucose is broken down in a series of
steps. Each step has its own enzyme
Respiration
 Hydrogens
are not transferred directly to
Oxygen, but are first passed to a
Coenzyme called NAD+
 NAD+ + electrons NADH
 H+ (proton) is transferred to the solution
 NADH will carry the electrons to an
Electron transport chain and will be used
to make ATP (more on this soon!!)
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Electron Flow
 Overall
flow of electrons in respiration
 FoodNADHelectron
chainOxygen
transport
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3 Main Steps to Cellular
Respiration
Glycolysis – happens in the cytosol.
Breaks glucose into smaller compound
(pyruvate)
 2. Citric Acid (Krebs) cycle – happens in
the matrix of the mitochondria. Breaks
down pyruvate to CO2
 3. Electron transport chain – happens in
the inner mitochondrial membrane.
Generates ATP using electrons from steps
1 and 2
 1.
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Glycolysis
 Splits
glucose (6 Carbons) into two
molecules of pyruvate (3 C each)
 No oxygen required (yet)
Glycolysis




Energy Investment Phase
2 ATP are USED to phosphorylate glucose and
convert it into two pyruvates
Energy Payoff Phase
After a series of enzyme catalyzed reactions: 4
ATP are produced by Substrate level
phosphorylation (using a substrate to make
ATP)
 2 NADH are produced by transferring electrons
to NAD+
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Glycolysis
 Total
Input
 Glucose, 2ATP, 2NAD+
 Total
Output
 2 Pyruvate, 4 ATP, 2NADH
 Net
ATP produced = 2
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Got Oxygen???
oxygen is present – pyruvate moves into
the mitochondria
 Pyruvate is converted to Acetyl CoA in a
series of 3 reactions (all with enzymes)
 CO2 is released
 NAD+ gains an electron NADH
 Acetyl CoA enters the Krebs cycle
 If
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Citric Acid (Kreb’s) Cycle
 Occurs
in mitochondria matrix
 Cycle has 8 total steps (each catalyzed by
different enzyme)
 Step 1 – Acetyl CoA combines with Citrate
(citric acid cycle)
 Cycle happens 2 times (one for each
Acetyl CoA)
Citric Acid Cycle
 For
Each Acetyl CoA
 3 NAD+  3 NADH + 3H+
 1 FAD  1 FADH2
 1 ATP is produced (substrate level
phosphorylation)
 2 CO2 are produced
Citric Acid Cycle
 Total
Inputs
 2 Acetyl CoA, 6 NAD+, 2 FAD, 2 ADP
 Total
Outputs
 6 NADH, 2 FADH2, 2 ATP, 4 CO2
(released when exhale)
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Electron Transport Chain
 Location Inner
Mitochondrial Membrane
 Series of molecules (mostly proteins)
embedded in this membrane
 Each part of the chain gets more and more
electronegative until the end of the chain
 OXYGEN is at the end of the
 chain (most electronegative)
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Electron Transport Chain
 NADH
and FADH2 from glycolysis and the
Citric acid cycle carry their electrons to the
electron transport chain
 NADH releases electrons at the top of the
chain. Electrons are pulled down the
chain by the increasing electronegativity of
each molecule
 As the electrons fall, ATP is made through
Chemiosmosis (more later)
Electron Transport Chain
 FADH2
carries its electrons to the chain,
but donates them a little further down the
chain (not at the top)
 These electrons are also pulled down the
chain, producing ATP as they go
FADH2
starts here
Chemiosmosis
 Process
that makes ATP
 As electrons flow down the ETC, energy is
released.
 This energy is used to pump H+ (protons)
across the membrane leaving a high
concentration of H+ outside and a low
concentration inside
Chemiosmosis





H+ wants to flow back in to the mitochondrial
matrix to reach equilibrium
The only way for the H+ to get back in is through
the enzyme ATP synthase
ATP synthase is an enzyme located in the inner
mitochondrial membrane
As H+ moves through the membrane, it allows
ADP to be phosphorylated making ATP (ADP +
Pi ATP).
This is called Oxidative phosphorylation (using a
redox rxn to make ATP)
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Electron Transport Chain
 Net
outputs
 For each NADH that enters the chain, 3
ATP are produced – Total = 30 ATP
 For each FADH2 that enters the chain, 2
ATP are produced – Total = 4 ATP
 Water is released by combination of O2
with H+ and electrons H2O
Respiration
 Total
ATP Production for Cellular
Respiration
ATP – Glycolysis
 2 ATP – Citric Acid Cycle
 34 ATP – Electron Transport
 Total = 38 ATP
2
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Fabulous Fermentation
 Allows
cells to generate ATP without
Oxygen (anaerobic). ATP is made only by
substrate level phosphorylation
 Process
involves Glycolysis + reactions to
regenerate NAD+ (in respiration NAD+ is
regenerated in the ETC)
Alcohol Fermentation
 After
glycolysis, pyruvate is converted to
ethanol in order to regenerate NAD+. This
allows glycolysis to continue again.
 Occurs in Yeast and Bacteria
 Used to make Alcohol
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Lactic Acid Fermentation

After glycolysis, pyruvate is converted to lactate
to regenerate NAD+.
 Used by Fungi and Bacteria
 Important in dairy industry to make cheese and
yogurt.
 Also occurs in Human Muscle Cells during
exercise. Muscles can’t get enough oxygen to
keep up with respiration. Lactate
builds up causing muscle cramps
and fatigue.
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Evolutionary Significance of
Glycolysis
 Glycolysis
was probably used by the
earliest prokaryotes to make ATP before
oxygen was present in the atmosphere.
 Evidence – Glycolysis occurs in the
cytoplasm (not in mitochondria) and it is
found in ALL living cells
What else can be used for
Respiration??
1. Carbohydrates – Broken down into glucose
then enter glycolysis
 2. Proteins – Broken down into amino acids
which can enter the cycle later in glycolysis or in
Citric Acid cycle (not normally used – need to
use amino acids to make protein)
 3. Fats – Glycerol enters the cycle during
glycolysis. Fatty acids are broken down into 2
Carbon fragments that enter at Kreb’s cycle
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Control of Respiration
 Cells
do not make more ATP than they
need
 Cells can switch of respiration, usually by
Feedback Inhibition of certain enzymes in
the chain.
 This prevents making unnecessary ATP
and the molecules used in respiration can
be used for other processes.
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