1. How cells harvest chemical energy ATP Cell respiration intro video
Cellular Respiration
How cells harvest chemical energy
ATP
Cell respiration intro video

2. Introduction to Cellular Respiration
Cell respiration is how we derive energy from our food, specifically glucose
Nearly all cells in our body break down sugars for ATP production
The aerobic harvesting of energy from sugar is called cellular respiration
Glucose
Oxygen gas
Carbon dioxide
Water
Energy
38 ATPs

3. Respiration and Cellular Respiration are linked
Breathing supplies oxygen to our cells for cellular respiration, it also removes CO2 as a waste product
BREATHING
Muscle cells carrying out Cellular Respiration
Sugar + O2  ATP + CO2 + H2O

4. Respiratory System Purpose What is respiration?
The process by which oxygen and carbon dioxide are exchanged between cells, the blood, and air in the lungs
The respiratory system is where gas exchange occurs
Picks up oxygen from inhaled air
Expels carbon dioxide
lungs

5. Cellular Respiration banks energy in ATP
Cellular respiration breaks down glucose molecules and banks their energy in ATP
The process uses O2 and releases CO2 and H2O
Glucose
Oxygen gas
Carbon dioxide
Water
Energy
Introduction Animation

6. Redox Reactions Redox (oxidation-reduction) Reactions
Oxidation describes the loss of an electron by a molecule, atom or ion; loss of hydrogen (H) or gain of oxygen (O)
OIL: Oxidation Is Losing H atoms
Reduction describes the uptake of an electron by a molecule, atom or ion; loss of oxygen (O) or gain of hydrogen (H)
RIG: Reduction Is Gaining H atoms
Give an example.

7. Cellular Respiration is a redox reaction
Loss of hydrogen atoms
Energy
Glucose
Gain of hydrogen atoms
Glucose  Carbon dioxide is a oxidation reaction
OIL
Oxygen  Water is a reduction reaction
RIG

8. Once again… Cellular Respiration banks energy in ATP
Cellular respiration breaks down glucose molecules and banks their energy in ATP
The process uses O2 and releases CO2 and H2O
Glucose
Oxygen gas
Carbon dioxide
Water
Energy

9. What is ATP? ATP: adenosine triphosphate
Currency of biological energy
When ATP becomes ADP, it gives off energy
A – P – P – P + H2O  A – P – P + P + energy
Therefore, when ATP is created, energy is stored!
Adenosine is made of adenine and ribose

10. How can we generate ATP ? Two different ways:
1. Substrate-level phosphorylation
2. Chemiosmosis
An enzyme transfers a phosphate group from an organic molecule to ADP.

11. Generating ATP continued…
2. Chemiosmosis
Oxidative phosphorylation
ATP synthase (a protein) synthesizes ATP using the energy stored in concentration gradients of H+ ions across membranes
Occurs in a membrane
High H+ concentration
ATP synthase uses gradient energy to make ATP
Membrane
Electron transport chain
ATP synthase
Energy from
Low H+ concentration
ATP synthesis

12. Cell Respiration occurs in 3 stages
Glycolysis occurs in the cytoplasm of the cell
Krebs cycle occurs in the mitochondria
Electron transport chain occurs in the mitochondria
High-energy electrons carried by NADH
GLYCOLYSIS
ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS
KREBS CYCLE
Glucose
Pyruvic acid
Cytoplasm
Mitochondrion

13. Mitochondria
Purpose of Cristae: The inner membranes of mitochondria fold many, many times. These folds are called cristae. These cristae are important because they make more surface area where chemical reactions can take place. The molecules and some of the enzymes responsible for making ATP are located in and on the folds of these inner membranes (cristae)
Intermembrane space

14. Glycolysis
Breaking down of sugar
* Detailed Handout *

15. Glycolysis: breaking down of glucose
Process by which 1 glucose molecule is broken down into 2 molecules of pyruvic acid.
Does not require oxygen
Occurs in the cytoplasm
Glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound.

16. Glycolysis does release some energy
Must invest two molecules of ATP to get the reaction started.
During the reaction, 4 ATP are created =
Net gain of 2 ATP
NADH is an electron carrier
NAD+ is a molecule that helps to pass energy from glucose to other pathways
NAD+ + 2e - + H + = NADH

17. NADH, an electron carrier

18. After Glycolysis… Products of glycolysis:
2 ATP
2 NADH
2 pyruvic acid
At the end of glycolysis, 90% of chemical energy that is available in glucose is still unused and locked in pyruvic acid.
In the presence of oxygen, pyruvic acid passes to the Krebs Cycle.
Glycolysis Animation

19. Acetyl CoA (acetyl coenzyme A)
Convert pyruvic acid  Acetyl CoA Preparatory step between glycolysis and Krebs cycle
Products:
2 Acetyl CoA
2 NADH
2 CO2
Each pyruvate molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle
Acetyl CoA (acetyl coenzyme A)
pyruvate
CO2

20. TAKES PLACE IN THE MATRIX OF THE MITOCHONDRIA
Krebs Cycle
Completes the oxidation of organic fuel, Generates many nadh and fadh2 molecules
TAKES PLACE IN THE MATRIX OF THE MITOCHONDRIA

21. Krebs cycle is a series of reactions in which enzymes strip away electrons and H+ from acetyl CoA
Acetyl group (2C) combines with 4C compound = citric acid (6C)
Citric acid is broken down and electrons released into 3 NADH and FADH2
4C compound ready to restart cycle
Citric Acid
C-C-C-C-C-C
Oxaloacetic Acid
C-C-C-C
KREBS CYCLE
CO2
Acetyl group of acetyl CoA combines with a 4C molecule = 6C citric acid
Citric acid is broken down into 4C molecule, more CO2 is released and electrons transferred to energy carriers
The 4c is ready to continue in the cycle, join with another acetyl group and start the cycle over.
5 carbon
compound
C-C-C-C-C
CO2

23. Energy Tallies from Krebs Cycle
One pyruvic acid
Two pyruvic acid
1 ATP
4 NADH
One from pyruvic  acetyl CoA
3 from citric acid  4C
1 FADH2
2 ATP
8 NADH
2 from prep stage
6 from citric  4C
2 FADH2
In the presence of oxygen, these high energy electrons can be used to generate HUGE amounts of ATP
Krebs Animation

24. Electron Transport Chain
Chemiosmosis powers ATP PRODUCTION

25. Electron Transport Chain
NADH and FADH2 are passed to the electron transport chain (ETC)
ETC is located in the inner membrane of the mitochondria
ETC uses high energy electrons from these molecules to convert ADP  ATP
How?!
Pumping H+ ions! (sound familiar?)

26. What fuel do we have headed into ETC?
From glycolysis:
2 ATP (substrate-level phosphorylation)
2 NADH
From prep stage and Krebs cycle
8 NADH
2 FADH2

27. Electron Transport Chain: composed of carrier proteins located in inner membrane
High energy electrons from NADH and FADH2 travel down the electron transport chain to an oxygen atom
At the end of ETC, an enzyme combines the electrons with H+ ions and oxygen to form WATER
Oxygen is the final electron acceptor
Protein complex
Intermembrane Space
Electron carrier
High energy electrons are passed from one carrier protein to the next.
Oxygen serves as final electron acceptor of ETC.
Inner membrane
Electron flow
2e- + 2 H+ + ½ O2  H2O
Matrix

28. Electron Transport Chain: composed of carrier proteins located in inner membrane
As electrons move down the chain, H+ ions are pumped into the intermembrane space of mitochondria
(High H+ concentration)
Protein complex
Intermembrane Space
Electron carrier
High energy electrons are passed from one carrier protein to the next.
Oxygen serves as final electron acceptor of ETC.
Inner membrane
Electron flow
Matrix

29. Chemiosmosis
H+ ions go down concentration gradient (highlow) through ATP synthase forming ATP
H+ ions that have come through ATP synthase are now ready to move across the membrane again via the electron transport chain = giant circle.

30. Each glucose molecule yields up to 38 molecules of ATP
Each NADH has enough energy to create 3 ATP each
Each FADH2 has enough energy to create 2 ATP each
Total ATP count with oxygen:
Process
Initial Input
ATP output
Glycolysis
2 ATP
2 NADH
6 ATP
Krebs Cycle
8 NADH
24 ATP
2 FADH2
4 ATP
TOTAL ATP =
38 ATP
ETC animation

31. ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS
REVIEW
Cytoplasmic fluid
Mitochondrion
Electron shuttle across membranes
GLYCOLYSIS
2 Acetyl CoA
ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS
2 Pyruvic acid
KREBS CYCLE
Glucose
by substrate-level phosphorylation
used for shuttling electrons from NADH made in glycolysis
by substrate-level phosphorylation
by chemiosmotic phosphorylation
Maximum per glucose:

32. Anaerobic Respiration
Without Oxygen

33. Fermentation is an anaerobic alternative to aerobic respiration
After glycolysis, if there is no oxygen then fermentation occurs.
Fermentation releases energy from food molecules by producing small amounts of ATP in the absence of oxygen.
Glycolysis will stop when all NAD+ electron carriers are full…how can NAD + be replenished?
Pyruvic acid
Glucose

34. Converting NADH to NAD +
During fermentation, cells will convert NADH to NAD+ by passing high energy electrons back to pyruvic acid.
By converting NADH to NAD+, glycolysis can continue and small amounts of ATP are created.
Two types:
Alcoholic Fermentation
Lactic Acid Fermentation

35. Alcoholic Fermentation
In alcoholic fermentation, pyruvic acid is converted to CO2 and ethyl alcohol.
This recycles NAD+ to keep glycolysis working
Pyruvic acid + NADH  ethyl alcohol + CO2 + NAD+
GLYCOLYSIS
2 pyruvic acid
2 Ethanol
Glucose

36. Lactic Acid Fermentation
In lactic acid fermentation, pyruvic acid is converted to lactic acid
This recycles NAD+ to keep glycolysis working
Pyruvic acid + NADH  lactic acid + NAD+

37. Lactic Acid Buildup
During strenuous exercise, our cells require energy faster than our bodies can deliver oxygen
Lactic Acid Fermentation (anaerobic): Our body begins to convert pyruvic acid into lactic acid to continue glycolysis to generate ATP.
This as lactic acid builds up at high levels in our muscles
High lactic acid = high acidity = pain and burning sensation
This often painful sensation also gets us to stop overworking the body, thus forcing a recovery period in which the body clears the lactate and other metabolites. Once the body slows down, oxygen becomes available and lactate reverts back to pyruvate, allowing continued aerobic metabolism and energy for the body’s recovery from the strenuous event.

38. Exercise and ATP

39. During exercise there are 3 sources of ATP
1. Stored ATP
2. Lactic Acid Fermentation
3. Cell Respiration
During a 200m sprint:
Stored ATP is gone in a few seconds of intense activity
Lactic Acid supplies enough energy for about 90 seconds
Only way to get rid of lactic acid
Heavy breathing to increase oxygen consumption
1oom final

40. What about a longer race?
2OOOm race
Need to use cell respiration = continuing supply of ATP
Respiration releases energy slowly which is why even well-conditioned athletes pace themselves.
Where does the supply of glucose come from?
GLYCOGEN in the muscles
Glycogen stores enough glucose to last 15-20min
Then it starts using other energy such as fats.

41. One final point
All organisms have the ability to harvest energy (ATP) from organic molecules (glucose)
However, only plants can make organic molecules (glucose) from inorganic sources by the process of photosynthesis

42. Photosynthesis vs. Cell Respiration
Function
Energy Capture in Foods
Energy Release from Foods
Location
Chloroplasts
mitochondria
Reactants
Carbon dioxide, water and light energy
Glucose and oxygen
Products
Carbon dioxide, water and ATP energy
Equation
6CO2 + 6H2O + light 
C6H12O6 + 6O2
C6H12O6 + 6O2 
6CO2 + 6H2O + ATP