Download ch 9 Cellular_Respiration

Cellular
Respiration
Chapter 9
Overview
• Sunlight is the main
source of all energy for an
ecosystem
• Photosynthesis converts
sunlight to glucose
(chemical energy) in
chloroplasts
Light energy
ECOSYSTEM
Photosynthesis
in chloroplasts
CO2 + H2O
Cellular respiration
in mitochondria
– Autotrophs only
• Glucose is then converted
to ATP by the
mitochondria through
cellular respiration
– Autotrophs and
heterotrophs
ATP
powers most cellular work
Heat
energy
Organic
molecules
+ O2
ATP
• Needed by all cells to do work – energy
• Must be regenerated or recycled – 2nd law
thermodynamics
ATP
Oxidation - Reduction (Redox)
Reactions
• Oxidation – loss of electrons
from one substance
– Glucose
• Reduction – addition of
electrons to another substance
– Oxidizing agent accepts electrons
– Oxygen – as electrons are
transferred to oxygen energy is
released
• Oxygen is very electronegative
which makes it a good oxidizing
agent – electron acceptor
Cellular Respiration: An overview
C6H12O6 + 6O2  6CO2 + 6H2O + ATP
Cell Respiration Overview
The Mitochondria
• Site of ATP production
• Double Membrane
• Critsae – infoldings of
the inner membrane
– Increases surface area
• Mitochondrial Matrix
– Inside of inner
membrane containing
many enzymes
Cell Respiration Overview
• C6H12O6 + 6O2  6CO2 + 6H2O + ATP
– 3 step process
• 1. Glycolysis – glucose lysis – breakdown of glucose to
pyruvate
– cytosol
• 2. Citric Acid Cycle (Kreb’s Cycle)– pyruvate
derivative (acetyl CoA) to CO2
– Mitochondrial matrix
• 3. Electron Transport Chain and Oxidative
Phosphorylation – electrons from glycolysis + CAC +
O2 to H2O
– Inner mitochondrial membrane
What is substrate level
phosphorylation?
• A mode of ATP synthesis when an enzyme
transfers a phosphate group from a substrate
molecule to ADP.
1. Glycolysis – “sugar breakdown”
• In the cytoplasm, the bonds in glucose are
rearranged producing pyruvate and releasing a
small amount of free energy (ATP and NADH).
Pyruvate is transferred from the
cytoplasm to the mitochondria
• Pyruvate cannot enter
the Citric Acid Cycle
• 2 Pyruvate  2
Acetyl Coenzyme A
(CoA)
– 2 CO2 is released
– 2 NADH formed
2. Citric Acid Cycle – Krebs Cycle
• Occurs in the
Mitochondrial Matrix
• Substrate Level
Phosphorylation
– Small amounts of ATP are
made
• Electrons are extracted
from compounds and
captured and stored by
coenzymes
– NAD
– FAD
NAD+  NADH
• NAD+ - nicotinamide adenine dinucleotide is a
coenzyme that transports electrons from glucose to the
electron transport chain to make ATP
• NAD+ is reduced (electrons are added) to NADH + H+
using the enzyme dehydrogenase
(2 electrons and 2 protons, but one proton is released)
3. Electron Transport Chain
• Oxidative Phosphorylation
– lots of ATP
• Occurs in the inner
mitochondrial membrane
• Electrons stored in NADH
and FADH2 from
glycolysis and the CAC are
transported to the ETC
• Oxygen is the final
electron acceptor!
Chemiosmosis (Fig 9.15)
Chemiosmosis
• Proteins carry electrons
through the ETC while
proton pumps pump H+
out into the cristae
• The H+’s create a
gradient
• As H+’s pass through
the enzyme ATP
synthase, ATP is made
Oxidative Phosphorylation
• Draw the ETC & Chemiosmosis
• Summarize how chemiosmosis makes ATP.
• Refer to figure 9.15
Electron shuttles
span membrane
CYTOSOL
MITOCHONDRION
2 NADH
or
2 FADH2
2 NADH
2 NADH
Glycolysis
Glucose
2
Acetyl
CoA
2
Pyruvate
Citric
acid
cycle
+ 2 ATP
+ 2 ATP
by substrate-level
phosphorylation
by substrate-level
phosphorylation
Maximum per glucose:
Figure 9.16
6 NADH
About
36 or 38 ATP
2 FADH2
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
+ about 32 or 34 ATP
by oxidative phosphorylation, depending
on which shuttle transports electrons
from NADH in cytosol
Complete the chart:
Process
Where?
Phosphorylation
1. Glycolysis
Cytosol
Substrate Level
2. Pyruvate 
Acetyl CoA
Mitochondrial
Matrix
N/A
3. Citric Acid
Cycle (Kreb’s)
Mitochondrial
Matrix
Substrate Level
4. Electron
Transport
Chain (ETC)
Inner
Mitochondrial
Membrane
Oxidative
TOTAL
Cytosol +
Mitochondria
N/A
Input
Output
Making ATP – Energy
• Catabolic Pathways
• Aerobic Respiration – O2
available
– Exergonic – lots of energy
– Glucose  energy
– mitochondria
• Anaerobic Respiration =
Fermentation - No O2
available
– Only partially degrades
sugars
– Not a lot of energy
– cytosol
Fermentation = anaerobic respiration
Glucose
CYTOSOL
Pyruvate
No O2 present
Fermentation
O2 present
Cellular respiration
MITOCHONDRION
Ethanol
or
lactate
Acetyl CoA
Citric
acid
cycle
Fermentation = anaerobic respiration
• No O2 present (no electronegative pull exists
from oxygen – NO ETC)
• Glycolyis and NAD+ regeneration
– If NAD+ is not regenerated ATP cannot be produced
Alcoholic Fermentation
• Glycolysis – glucose  2
pyruvates
• 2 Pyruvate  Ethanol +
CO2
• Ethanol (Ethyl alcohol)
accepts electrons from
NADH therefore
regenerating NAD+
• Used by bakers and
brewers – yeast (fungal)
cells ferment
• Many bacteria ferment
Lactic Acid Fermentation
• Glycolysis – glucose  2
pyruvate
• 2 pyruvate  2 Lactate
• Lactate accepts the
electrons from NADH
regenerating NAD+
• Fungi and bacteria
• Human muscle cells
– Anaerobic exercise
Respiration vs. Fermentation
• Respiration
–
–
–
–
O2
Mitochondria
Electron Acceptor is O2
~36-38 ATP
• Fermentation (anaerobic)
– No O2
– Cytosol
– Electron Acceptors are
Ethanol or Lactate
– 2 ATP
Heterotrophs don’t eat just glucose
Proteins
• Proteins, Lipids and
Carbs may enter the
process of respiration at
various locations
• Glucose provides the
most direct ATP
Amino
acids
Carbohydrates
Sugars
Glycolysis
Glucose
Glyceraldehyde-3- P
NH3
Pyruvate
Acetyl CoA
Citric
acid
cycle
Figure 9.19
Oxidative
phosphorylation
Fats
Glycerol
Fatty
acids