Topic 3.7 – Cell Respiration
How Cells Harvest Chemical Energy
Cellular respiration is the set of the metabolic reactions and
processes that take place in the cells of organisms to convert
biochemical energy from nutrients into adenosine triphosphate
(ATP), and then release waste products
Breathing and Cell Respiration are related
HOW?
O2
BREATHING
CO2
Lungs
CO2
Bloodstream
Muscle cells
O carrying out
2
CELLULAR
RESPIRATION
Sugar + O2  ATP + CO2 + H2O
Cellular Respiration uses oxygen and glucose to produce
Carbon dioxide, water, and ATP.
Glucose
Oxygen gas
Carbon
dioxide
Water
Energy
Reduction and Oxidation
O.I.L.R.I.G.
Oxidation is losing electrons (or hydrogens) from
an element or molecule
Reduction is gaining of electrons (or hydrogens)
by an element or molecule
Loss of hydrogen atoms
Energy
Glucose
Gain of hydrogen atoms
Glucose gives off energy and is oxidized
Reduction and Oxidation
OILRIG
Gain or loss of electrons is often in the form of hydrogen.
The hydrogen is then passed to a coenzyme such as NAD+
Oxidized
Reduced
Reduction and Oxidation
These co-enzymes are very important for cell
respiration because they transfer high-energy
electrons to electron transport systems (ETS).
Reduction and Oxidation
As the electrons move from carrier to carrier,
energy is released in small quantities.
Electron transport system
(ETS)
General Outline - Initial Reactions for bot Aerobic
and Anaerobic cellular respiration are the same =
GLYCOLYSIS
Glucose
Glycolysis
Oxygen
Aerobic
Pyruvic Acid
No Oxygen
Anaerobic
Fermentation
Transition Reaction
Krebs Cycle
ETS
36 ATP
Generation of ATP – What is phosphorylation?
The transfer of a phosphate, phosphate groups to
a molecule
One type: Substrate Level Phosphorylation
Enzyme
Adenosine
substrate
Adenosine
product
Figure 6.7B
Glycolysis
Where? The cytosol
What? Breaks down glucose to pyruvic acid
How? – see following slides
Glucose
Glycolysis
Steps 1 – 3 A fuel
molecule is energized,
using ATP.
Step
1
Glucose-6-phosphate
2
Fructose-6-phosphate
3
Energy In: 2 ATP
Fructose-1,6-diphosphate
Step 4 A six-carbon
intermediate splits into
two three-carbon
intermediates.
4
Glyceraldehyde-3-phosphate
(G3P) (TRIOSE PHOSPHATE)
5
Step 5 A redox
reaction generates
NADH.
6
Energy Out: 4 ATP
Steps 6 – 9 ATP
and pyruvic acid
are produced.
1,3-Diphosphoglycerate
(2 molecules)
7
3-Phosphoglycerate
(2 molecules)
8
2-Phosphoglycerate(2
molecules)
2-Phosphoglycerate(2
molecules)
NET 2 ATP and 2 NADH
9
Pyruvic acid
(2 molecules
per glucose molecule)
What is NAD+ and NADH + H+ ?
Nicotineaminde-adenine-dinucleotide.
It is a coenzyme and an electron carrier.
Draw and label a diagram showing the structure of a
mitochondrion as seen in ELECTRON MICROGRAPHS
Explain aerobic cellular
respiration, including the link
reaction, the Krebs cycle, the
electron transport chain
Transition Reaction/Pre-Krebs/Link Reaction:
Occurs in the Matrix
Each pyruvic acid molecule is broken down to form
CO2 and a two-carbon acetyl group, which enters the
Krebs cycle. An Oxidative Decarboxylation Reaction:
Pyruvic Acid
Acetyl CoA
General Outline of Aerobic Respiration
Glycolysis
Transition Reaction
Krebs Cycle
Electron Transport System
Krebs Cycle - (also known as Citric Acid Cycle or Tricarboxylic
Acid Cycle) is a step wise cyclic process which is used to oxidize
the pyruvate formed during glycolysis into (CO2) and (H2O).
Where? In the Mitochondria
What? Uses Acetyl Co-A to generate ATP, NADH,
FADH2, and CO2.
Krebs Cycle
General Outline of Aerobic Respiration Cont’d _- ETS
A series of membrane proteins and coenzymes that
undergo a red-ox reactions that often produce a
chemical gradient that can then be used to do work
Glycolysis
Krebs Cycle
Electron Transport
System
Electron Transport System – another version
Protein
complex
Intermembrane
Electron
space
carrier
Inner
mitochondrial
membrane
Electron
flow
Mitochondrial
matrix
ELECTRON TRANSPORT CHAIN
Figure 6.12
ATP
SYNTHASE
Electron Transport System – a 3rd view
Explain oxidative phosphorylation in
terms of chemiosmosis
• The ETCs basic’s function is to ease the fall of
electrons from food to oxygen, breaking a large
energy drop into series of small steps.
• Chemiosmosis is using H+ ion in the
intermembrane space to drive ATP, through the
use of an ATP synthase (enzyme).
• Collectively ETC and chemiosmosis drive
oxidative phosphorylation
Generation of ATP
Chemiosmosis
Cells use the energy
released by “falling”
electrons in the ETS to
pump H+ ions across a
membrane
Uses the enzyme ATP
synthase.
Overview of Aerobic Respiration