It can be said that photosynthesis is the chemical link between the inorganic & organic worlds …

Now that we’ve stored our cell’s energy in the form of glucose, we need to change this potential chemical energy into ATP: a usable energy source needed for cells to function.

Photosynthesis stored the energy in glucose: Respiration transfers the energy to ATP so it

can be released.

Cellular Respiration

• A single molecule of glucose is too much energy to be used for a single chemical reaction in a cell.

• All living organisms must break down glucose and create small packets of usable chemical energy in the form of ATP

C6H12O6 + O2 CO2 + H2O + ATP

Why do we need ATP ???? It is the most efficient “currency” of the cell

• An analogy:

One Glucose Many ATP

What is this ATP stuff anyway? ..

Adenosine Triphosphate (ATP)• Energy carrying molecule used by cells to fuel

their cellular processes• ATP is composed of three parts: an adenine base,

ribose sugar, and three phosphate groups

• When a cell needs energy, an enzyme will remove the last PO4. The breaking of this chemical bond forms ADP (adenosine diphosphate) and releases energy to be used by the cell.

• The PO4 bonds are high-energy bonds that require energy to be made and release energy when broken.

Cellular Respiration

Step 1: Glycolysis (the anaerobic stage)

• Glucose (6C sugar) is split into two pyruvic acid molecules (3C molecule)

• Occurs in the cytoplasm of the cell & no oxygen is required

• A net of 2 ATP’s are created in this step

Respiration is a controlled process. Each step in the reaction is specifically controlled by enzymes.

Glucose is the fuel most commonly used by organisms. This glucose fuel is oxidized or “burned” by the cell in two stages:

Step 2: Aerobic Respiration• Requires Oxygen• Takes place in the

mitochondria• Biochemical

pathway: Krebs Cycle/Citric Acid Cycle and electron transport chain

• Produces a net gain of 34 ATP’s

Total ATP’s = 36 (Gycolysis + Krebs + Electron Transport)

(2) (2) (32)

Krebs Cycle / Citric Acid Cycle: A Complex Biochemical Pathway (2 ATP)

The Electron Transport Chain (32 ATP)

We have seen that, through complex reactions inside living cells, each glucose molecule can generate 36 ATPs. This process however, is still only 60% efficient. Most of the remaining energy is generated as heat. In warm-blooded animals this heat keeps the body temperature constant. The remaining energy, stored in ATP, can be used for cellular activities.

It might be a good time to review the Laws of Thermodynamics.

• Takes place in the cytoplasm• Biochemical Pathway:

Fermentation• Produces a net gain of 2 ATP’s

If No Oxygen is present, aerobic respiration is replaced with anaerobic respiration / fermentation

Total ATP’s = 4 ( 2: Glycolysis + 2:Fermentation)

Types of Fermentation1) Alcohol Fermentation

2) Lactic Acid Fermentation

Alcoholic Fermentation

• Alcoholic Fermentation: produces ethyl alcohol and carbon dioxide as products

• Occurs with yeast in baking & wine industry

• Lactic Acid Fermentation: produces lactic acid as a product

• Occurs in muscle cells that are overworked

• Lactic Acid causes the “fatigue” in muscles during strenuous exercise

Lactic Acid Fermentation

Got it??

ANABOLIC Reactants

CO2 + H2O

Products: C6H12O6 Activation Energy

Stored Energy

PHOTOSYNTHESIS

CATABOLIC

Reactants

C6H12O6

Products: CO2 + H2O

Activation Energy

Released Energy

RESPIRATION