1. Photo by Thomas Dreps
Energy Conversions
Glucose
ATP

2. All cells need energy to perform chemical reaction and stay alive
All cells need energy to perform chemical reaction and stay alive. This energy comes from the food that is absorbed by the cell.

3. Carbohydrates and lipids are the main sources of energy used by cells.

4. The energy from carbohydrates and lipids is not used directly
The energy from carbohydrates and lipids is not used directly. First, it must be converted into a more useable form.
Glucose
ATP
The energy molecule that is utilized by all cells is known as ATP. Energy is taken out of the food and converted into the more useable ATP molecules.

5. But why can’t cells just use energy directly from food
But why can’t cells just use energy directly from food? Why even bother converting it into ATP?
Glucose
Glucose contains a large amount of energy. In fact, it contains too much energy to be released all at once.
If all of the energy in glucose was released at once, most of it would be wasted and simply released as heat.

6. The cell needs to place the energy into ATP so that it can be released a little bit at a time.
The energy from 1 glucose molecule is used to create up to 36 ATP molecules.
1 Glucose
36 ATP
The ATP molecules can deliver smaller amounts of energy without wasting much of it at all.

7. In order to get energy out food, cells perform a process known as
cellular respiration.
To understand this process, you need to understand how to read a chemical reaction.

8. Carbon Dioxide
Sugar
(Glucose)
Oxygen
Water
The substances on the left side are called the reactants. These are the raw materials needed for a reaction to take place.
The substances on the right side are called the products. These are the substances the are formed as a result of the reaction.

9. Carbon Dioxide
Sugar
(Glucose)
Oxygen
Water
When heat or energy appears in a chemical equation on the products’ side (right), it means it is being released!
Cellular respiration releases energy from food so that it can be used by cells!

10. Most of the process of cellular respiration takes place inside of the mitochondria.
This is why we say that the mitochondria is like a power plant. It is where energy from raw materials is converted into useable ATP!

11. During exercise your muscle cells cannot absorb oxygen fast enough to make the ATP they need. When this happens, a second process known as fermentation occurs. This less efficient process allows your body to make ATP, but it produces lactic acid which makes you sore.

12. Photo by Ildar Sagdejev
Fermentation by yeast and bacteria is used in the food industry. When yeast is used for the fermentation process, it produces alcohol instead of lactic acid as a side product. Carbon dioxide is still produced, which is why yeast makes bread rise.
Photo by Martinonline

13. All eukaryotic cells have mitochondria to convert energy from food into useable ATP. However, plants and other autotrophic organisms make their own food through a process known as photosynthesis.

14. Carbon Dioxide
Glucose
(Sugar)
Oxygen
Water
The raw materials (reactants) needed by plants to perform photosynthesis are water and carbon dioxide.
The products of photosynthesis are glucose (a sugar) and oxygen gas. Glucose is the food molecule created by photosynthesis.

15. Photosynthesis absorbs energy so that plants can make their food!
Carbon Dioxide
Glucose
(Sugar)
Oxygen
Water
When heat or energy appears in a chemical equation on the reactants’ side (left), it means it is being absorbed!
Photosynthesis absorbs energy so that plants can make their food!

16. The energy that is absorbed by plants during photosynthesis comes from the sun!
Photo- means light!

17. The energy in the sugars made by glucose is stored in the chemical bonds, so we call it chemical energy. Because of this, we say that plants and other photosynthetic organisms convert solar energy into chemical energy.

18. Chloroplasts are the organelle in plant cells which are responsible for absorbing light and performing photosynthesis.
Photo by Thomas Dreps

19. Chloroplasts are full of chlorophyll molecules
Chloroplasts are full of chlorophyll molecules. This molecule absorbs energy that will be used to make the glucose.
Chlorophyll

20. Because chloroplasts and chlorophyll make the cell green!
Based on your vocabulary reference sheet, why is the prefix chloro- used to name this important organelle and the molecule inside of it?
Because chloroplasts and chlorophyll make the cell green!
Chloro- means GREEN.

21. Seeds and very young plants need oxygen to grow and not carbon dioxide
Seeds and very young plants need oxygen to grow and not carbon dioxide. Why is this?
Seeds need oxygen to perform cellular respiration to use the food energy stored in the seeds by their parents. They can’t perform photosynthesis until they are large enough to have their own leaves!

22. Chemosynthesis
Deep in the ocean, there is no light for photosynthesis to occur. But in the 1970s, scientists found entire food webs living near underwater hydrothermal vents which spew minerals and provide heat.

23. Chemosynthesis
Scientists found bacteria that were performing chemosynthesis by obtaining energy from inorganic compounds like hydrogen sulfide (H2S) instead of light.
Photo by Adrian Hetzer
These bacteria use this energy and CO2 to produce the organic compounds needed in the ecosystem.

24. Chemosynthesis
These chemosynthetic bacteria are the producers in these deep underwater ecosystems, and they often live symbiotically inside larger animals like the tube worms shown to the right.
Photo by Adrian Hetzer
Photo by Achim Raschka