1. Cells Chapter 2 Section 2
RESPIRATION

2. RESPIRATION
Respiration is a process in which cells break down simple food substances, such as glucose, and release the energy they contain.
During respiration, glucose and oxygen are converted into carbon dioxide and water.
Photosynthesis and respiration can be thought of as opposite processes. These two processes form a cycle that keeps the levels of oxygen and carbon dioxide fairly constant in the atmosphere.
Fermentation provides energy for cells without using oxygen.

3. ENERGY We get our energy from food.
This does not mean that you get energy immediately after eating.
First, the food must pass through your digestive system, where it is broken down into small molecules.
The molecules pass out of your digestive system and into your bloodstream.
From there the molecules travel through your bloodstream to the cells of your body.
The energy is released inside your cells.

4. STORING AND RELEASING ENERGY
Cells store and use energy:
1) During photosynthesis plants capture the energy from sunlight and save it as carbohydrates, including sugars and starches.
2) When plants need energy,their cells break down the carbohydrates. This releases the stored energy.

5. THE PROCESS
The process by which cells release energy from glucose is called respiration.
During respiration, cells break down simple food molecules such as glucose and release the energy they contain.
This process goes on continuously in all living things because living things need a continuous supply of energy.
Cellular respiration does not mean breathing, but it does require oxygen.

6. TWO STAGES OF RESPIRATION Stage 1 Takes place in the cytoplasm of the cells. Glucose molecules are broken down into smaller molecules. Oxygen is not involved in this stage. Only a small amount of energy in glucose is released during this stage.

7. Stage 2 takes place in the mitochondria of the cells
Stage 2 takes place in the mitochondria of the cells. The small molecules are broken down even smaller. These chemical reactions require oxygen and a great deal of energy is released. This is why mitochondria are called the “powerhouses” of the cell.

8. ANOTHER EQUATION
The overall process of respiration can be summarized by the following equation:
C6H12O6 + 6O CO2 + 6H2O + Energy
glucose oxygen carbon dioxide water
Notice that the raw materials for respiration are glucose and oxygen, and the products are carbon dioxide, water, and energy.
Plants make their own glucose and oxygen.

9. FERMENTATION Provides energy for cells without using oxygen.
Some cells live where there is no oxygen (deep in the ocean or in mud under lakes or swamps).
The amount of energy obtained from each sugar molecule during fermentation is much less than from respiration.

10. TWO TYPES OF FERMENTATION
Alcoholic Fermentation:
Occurs in yeast and some other single celled organisms.
Alcohol, Carbon Dioxide and a small amount of energy are produced.
These products are important for bakers and brewers.
The CO2 causes dough to rise and makes the bubbles in beer and champagne.

11. Lactic Acid Fermentation:
Takes place at times in your body.
Causes your muscles to feel weak and sore after a hard workout.
Happens because no matter how hard you breathe, your muscle cells used oxygen faster than you could take it in. Without O2, fermentation occurred.
Fermentation of this kind causes lactic acid to build up in your muscles, making them feel weak & sore.