How to Troubleshoot Apps for the Modern Connected Worker
Cellular respiration
1. Cellular Respiration
Dr. Mark A. McGinley
Honors College and Department of
Biological Sciences
Texas Tech University
2. Biological Work
• Most of the energy used to do biological work
comes from ATP
• ATP breaks down and releases energy that is
used to do biological work
3. Energetics in a Nutshell
• Photosynthesis converts light energy to
potential energy stored in chemical bonds of
glucose
• Cellular Respiration converts potential energy
in glucose to potential energy stored in ATP
– ATP releases energy used to do work
• Glucose links the two processes
4. Breaking Down Glucose to Release
Potential Energy
• Starts with the process of glycolysis
• Followed by either
– Fermentation (in anaerobic environments)
– Citric Acid Cycle (Krebs Cycle) + electron transport
(in aerobic environments)
5. Glycolysis
• Glucose broken down into two molecules of
pyruvate
– Occurs in the cytosol
• Breaking down ATP requires the input of
energy from 2 molecules of ATP but releases
energy in 4 molecules of ATP
• Thus, net gain of energy of 2 ATPs in glycolysis
7. Glycolysis
• Glycolysis breaks down glucose to release
energy in two ATPs
– ATPs can release energy to do biological work
8. Problem Facing the Cell
• Glucose <= => 2 pyruvate + H+
• This reaction will continue to break down
glucose to release ATP until the reaction
reaches an equilibrium
• Once equilibrium is reached, glycolysis will
stop, so no more ATP is released
9. Solution
• In order to allow glycolysis to continue cells
must maintain the concentration gradient by
removing pyruvate and H+ from the cell.
• H+ picked up by NAD+ => NADH
• Eventually NAD+ gets saturated
10. Ultimate Solution
• H+ must be removed from NADH in order to
allow glycolysis to continue
• Key Point- How this happens depends on
whether or not there is oxygen in the
environment
11. Anaerobic Environment
• When there is no oxygen in the environment
then pyruvate and H+ are removed from the
cell by fermentation
• Several patterns of fermentation including
– Alcohol fermentation
– Lactic acid fermentation
13. Advantages and Disadvantages of
Alcohol Fermentation
• Benefit
– End products of glycolysis are removed from the
cell so glycolysis can continue
• Disadvantage
– Alcohol can be poisonous to cells
– Pyruvate used to help remove H+ from the cell
• Still lots of potential energy stored in pyruvate
• Can’t break down pyruvate to release energy
15. Advantages and Disadvantages of
Lactic Acid Fermentation
• Benefit
– End products of glycolysis are removed from the
cell so glycolysis can continue
• Disadvantage
– lactate can be poisonous to cells
– Pyruvate used to help remove H+ from the cell
• Still lots of potential energy stored in pyruvate
• Can’t break down pyruvate to release energy
16. Review in Anaerobic Environments
• Glucose broken down by glycolysis and
fermentation
• For each glucose molecule broken down there
is a net gain of two ATPs
17. Aerobic Environments
• When oxygen is present
– O2 + H+ => H20
• Water becomes the ultimate hydrogen
acceptor
– Benefit
• Water is non-toxic and in fact is beneficial
• Pyruvate can be broken down to release more stored
energy
18. Energy From Pyruvate
• Glycolysis occurs in the cytosol
– NADH and pyruvate move into the mitochondria
• In the mitochondria pyruvate is broken down
to release ATP in two processes
– Citric acid cycle (Krebs Cycle)
– Electron transport
20. Citric Acid Cycle
• The details of the Citric Acid Cycle are well know
– Not super important for this course
• Key Points
– Inside of the mitochondrion pyruvate breaks down to
produce CO2 + Acetyl CoA
– Acetyl CoA enters Citric Acid Cycle
• Acetyl CoA + oxaloacetate = > citrate
– CO2 released
– 1 ATP produced for each Acetyl CoA that enters the
cycle
• Thus, 2 ATPs per glucose
21. Electron Transport
• In a process very similar to what we talked
about in cyclic electron flow in photosynthesis
– An excited electron moves down an electron
transport chain (located in inner membranes of
mitochondria)
• Energy released used to actively transport H+
• H+ concentration gradient powers Chemiosmosis
– Releases lots of ATP
– 26 or 28 ATP/glucose
23. Review in Aerobic Environments
• Glucose broken down by glycolysis, citric acid
cycle, and electron transport
• For each glucose molecule broken down there
is a net gain of 30 - 32 ATPs
– 2 per glucose from glycolysis
– 2 per glucose from citric acid cycle
– 26 – 28 per glucose from electron transport
24. Advantages of Breaking Down Glucose
in Aerobic Environments
• Benefit
– End products of glycolysis are removed from the
cell so glycolysis can continue
– Ultimate hydrogen acceptor (water) is beneficial
to cells
– Pyruvate can be broken down to release much
more energy
