1. Respiration, Fermentation, and Photosynthesis

2. Free Energy Free energy is the energy needed to do work.
It takes work to keep the cell organized and functioning properly!
Ex: Active transport, muscle contractions, nerve impulses…

3. Endergonic & Exergonic Reactions
In a chemical reaction, the amount of energy in the reactants is usually different from the amount of energy in the products.
Energy is stored in the bonds between atoms within a molecule.
There are 2 type of reactions:
Endergonic – energy must be supplied
The products have more energy than the reactants
Exergonic – energy is released
The products have less energy than the reactants
Activation energy is still required!

4. Endergonic & Exergonic Reactions

5. Coupling Reactions
Endergonic and exergonic reactions are often coupled, or linked, to each other.
The energy released from the exergonic reaction is the same energy that is supplied for the endergonic reaction.

6. ATP
ATP (adenosine triphosphate) is the energy “currency” for living things
Adenine
ATP has 3 parts:
Adenine (a nitrogenous base)
Ribose (the same sugar that is found in RNA)
3 phosphate groups
*** Energy is stored in the bonds between the phosphate groups. The last bond (between the second and third phosphates) stores tons of energy!! The energy from food is not useful for the cell until it has been converted and stored in one of these high-energy bonds.

7. ATP & ADP
Energy is released when the bond between the second & third phosphate groups is broken.
This also produces ADP (adenosine diphosphate)
We need to turn ADP back into ATP to do more work!
Energy is required to reattach the 3rd phosphate group.
ATP  ADP + Pi Exergonic
ADP + Pi  ATP Endergonic
(Pi = inorganic phosphate)

8. ATP & ADP

9. ATP & ADP ATP  ADP + Pi Exergonic ADP + Pi  ATP Endergonic2.
Energy from food is then
stored as a phosphate bond
in ATP.
ATP 3.
Energy is then released when
the phosphate bond is
broken, and can be used to
fuel our everyday activities. 1.
Energy from food is
required to push a third
phosphate group onto ADP.
energy hill
energy in
energy
out P +
ADP P +
ADP
Figure 7.1

10. Aerobic Respiration (Aerobic = oxygen is required)
In aerobic respiration, glucose provides the energy to make ATP from ADP and inorganic phosphate.
The formula for cellular respiration is:
C6H12O6 + 6O ADP + 38 Pi  6CO2 + 6H2O + 38 ATP

11. 3 Stages of Aerobic Respiration:
Glycolysis
An anaerobic process that occurs in the cytosol
Uses 2 ATP but creates 4, for a net total of 2 ATP
Krebs cycle (citric acid cycle, TCA cycle)
Takes place in the mitochondria
Produces 2 ATP
Electron transport chain (ETC)
Takes place across the inner mitochondrial membrane
Produces up to 34 ATP
Oxygen is the terminal electron acceptor in the ETC.
Without oxygen, BOTH the ETC AND the Krebs cycle shut down!

12. Cellular Respiration Figure 7.4 (b) In schematic terms reactants
products
glycolysis
(a)
In metaphorical terms
2 ATP
insert 1 glucose
glucose
2 NADH
cytosol
glucose derivatives
glycolysis
2 energy
tokens
CO2
2 NADH
2 energy
tokens
CO2
6 NADH
Krebs
cycle
2 ATP
Krebs
cycle
2 FADH2
34 energy
tokens
electron
transport
chain
electron
transport
chain O2
34 ATP
mitochondrion
H2O
38 ATP maximum per glucose molecule
Figure 7.4

13. Aerobic Respiration

14. Anaerobic Respiration
Anaerobic = Oxygen is NOT required.
Anaerobic respiration is also called fermentation.
There are 2 types of fermentation:
A) Lactic acid fermentation
C6H12O6 + 4 ADP + 4 Pi 2 lactic acid + 4 ATP
This happens inside our muscles when we cannot get oxygen to them quickly enough (during strenuous exercise)
Also used by many bacteria
This is how yogurt, buttermilk, and sauerkraut are made!

15. Anaerobic Respiration
B) Alcoholic fermentation
C6H12O6 + 4 ADP + 4 Pi 2 ethanol + 2 CO2 + 4 ATP
Used by yeast and some other microorganisms
Used to produce beer, wine, and bread

16. Autotrophs vs. Heterotrophs
Autotrophs are organisms that can produce their own food (sugars) from CO2.
Turning CO2 to sugar is an endergonic process.
Photoautotrophs use energy from sunlight
Chemoautotrophs use energy from inorganic chemicals
Heterotrophs are organisms that must consume food.

17. Photosynthesis
During photosynthesis, photoautotrophic organisms like plants and cyanobacteria use energy from sunlight to convert carbon dioxide and water to glucose.
Light is a form of electromagnetic radiation.
Sunlight contains all wavelengths of the visible spectrum.

18. Electromagnetic Spectrum

19. Chloroplasts
In plants, photosynthesis takes place in the chloroplasts.
Chloroplasts contain the pigment chlorophyll, which makes them appear green.
There are 2 types of chlorophyll that absorb light in the red and blue wavelengths.
Green and yellow wavelengths are reflected, so this is what we see!
Chloroplasts also contain pigments called carotenoids that reflect orange and yellow wavelengths of light.
These become visible when chlorophyll degrades in the fall.

20. 2 Stages of Photosynthesis
The Light Reactions (Light-Dependent Reactions):
Sunlight absorbed by chlorophyll is used to activate electrons, which enter an electron transport chain, producing ATP.
The electrons come from water, forming oxygen as a by-product
Takes place across the membranes of coin-shaped thylakoids that are stacked inside the chloroplasts - a stack of thylakoids is called a granum (plural = grana)
The Calvin Cycle (Light-Independent Reactions):
Uses the ATP generated during the light reactions to produce glucose from carbon dioxide (an endergonic reaction!)
Takes place in the stroma, the liquid that fills chloroplasts.