1. Cellular Metabolism
Metabolism = all the chemical reactions of an organism
Catabolic Pathway = energy released through the breakdown of complex molecules into simple compounds
Anabolic Pathways = consume energy to build complicated molecules from simple compounds

2. Cellular Metabolism: How we get energy…
Energy is the capacity to do work. Energy is stored in the chemical bonds between atoms. When those bonds are broken, energy is released.
The cell uses some of this released energy to do work. The rest is given off as heat.

3. It could be worse…
Metabolic Pathways Chart

4. Catabolism: Two Types Fermentation- PARTIAL breakdown
of sugars, occurs in the absence of
oxygen (anaerobic respiration)
Cellular Respiration- most efficient catabolic pathway, oxygen is used as a reactant with carbs, fats and proteins all being broken down to release energy
**Glucose is the primary nutrient used in cellular respiration**

5. Many entry levels for macromolecules

6. Cellular Respiration: An overview
ATP is used to power all cellular activities

7. Cellular Respiration: Step 1 Glycolysis
“Glyco” = sugar “lysis” = breaking
Glycolysis occurs in the cytosol and it is the initial step in the breakdown of glucose.
Glucose (6C) is broken down into 2 pyruvate molecules (3C)
Glycolysis produces 4 ATP and 2NADH, but it uses 2 ATP in the process so it has a net production of 2 ATP and 2 NADH

8. Glycolysis:

9. Cellular Respiration: Part 2- Citric Acid Cycle (aka- The Krebs Cycle)
Occurs in the mitochondrial matrix
Final step in breaking down glucose
Two pyruvate molecules converted into Acetyl Co-A
Two cycles are required
Net Results:
4 CO2
2 ATP
6 NADH
2 FADH2

10. Cellular Respiration: Step 3 Electron Transport Chain (oxidative phosphorylation)
The electron transport chain produces energy that drives the synthesis (production) of ATP

11. Electron Transport Chain:
The NADH and FADH2 produced in glycolysis and the Krebs cycle are used in the electron transport chain to create ATP
Electrons from NADH and FADH are released through an oxidation reaction (lose electrons = oxidation)these electrons are passed down a chain of proteins until it reaches oxygen and then combines with hydrogen atoms to form water
Hydrogen ions (H+) are pumped through ATP synthases which in turn, combine ADP and an phosphate group into ATP (oxidative phosphorylation)
A net total of ATP produced = 32

12. Fermentation
Remember how oxygen accepted the electron in the transport chain? Well, without oxygen present, the cell has to have an alternate way of producing ATP….
Alcohol Fermentation- pyruvate is converted to ethanol, which produces CO2 and also oxidizes NADH
Lactic Acid Fermentation- pyruvate is reduced by NADH (NADH gets oxidized) and lactate is formed as a waste product
Facultative anaerobes – organisms that can make enough ATP
using fermentation or respiration

13. Lactic Acid Fermentation- Profile of a 400m Runner

14. Glycolysis and Krebs Cycle
Our food not only fuels our body but it provides materials to build macromolecules.
Glycolysis and the Krebs Cycle provide a way for compounds to enter anabolic pathways.
Ex. Amino Acids from food we eat can be incorporated into our own body proteins.

15. Overview of Cell Respiration:

16. Overview of photosynthesis

17. Photosynthesis: Conversion of light energy to chemical energy (food)
6 CO2 + 6 H2O + Light Energy C6H12O6 + 6O2
Photosynthesis occurs in the within the thylakoids of the chloroplasts
Chlorophyll is located in the thylakoid membranes and is responsible for absorbing the sunlight that drives photosynthesis
There are two main parts to photosynthesis: they are the light reactions and the Calvin cycle (dark reactions/ light-independent reactions).

18. Photosynthesis:

19. Photosynthesis: Light Reactions
Light is absorbed by chlorophyll and drives the transfer of electrons from water to form NADPH. Water is split and oxygen is released.

20. Steps of the Light Reactions:
Photosystem II absorbs light in the 680 nm wavelength range. An electron becomes excited and is passed down the electron transport chain.
Enzymes split water into two hydrogen ions and an oxygen atom.
The energy transfer of electrons down the electron transport chain is used to phosphorylate ADP to ATP (just like it did in respiration). This ATP is used during the Calvin Cycle to make carbohydrates*
The electrons that reach the end are donated to the chlorophyll in photosystem I . The electron is passed along another electron transport chain which ultimately reduces NAP+ to NADPH
* This is referred to as non-cyclic electron flow

21. Light Reactions

22. Photosynthesis: Light Reactions
An alternative to noncyclic electron flow is cyclic electron flow.
Only photosystem I is used and in this system, neither NADPH nor oxygen is produced but ATP is produced
The Calvin cycle reactions use more ATP than NADPH

23. Photosynthesis: The Calvin Cycle

24. Photosynthesis: Calvin Cycle
CO2 is converted to a carbohydrate called glyceraldehyde-3-phosphate (G3P) and ATP and NADPH are consumed
The cycle must have 3 molecules of carbon dioxide to produce 1 molecule of G3P
Nine molecules of ATP are consumed
Six molecules of NADPH are consumed
One of the six G3P molecules produced is later metabolized into larger carbohydrates

25. Overview: Photosynthesis

26. Alternatives: C4 Plants
C4 plants use a four carbon compound in the first step of the Calvin cycle instead of a 3 carbon compound
CO2 is added to phosphoenolpyruvate (PEP) to form the four carbon compound oxaoloacetate
C4 photo- synthesis
minimizes photo-respiration and enhances sugar production

27. C4 Plants

28. Alternatives: CAM plants (Crassulacean Acid Metabolism)
These plants keep their stomata closed during the day to prevent water loss.
At night, the stomata open and CO2 is taken in
Cells convert CO2 into various compounds and store it in vacuoles
In the morning the plants release the stored CO2 to run photosynthesis

29. CAM Plants