Photosynthesis
• The process by which a cell captures the energy in sunlight and uses it to make food.
•
Photo means “light”; synthesis means
“putting together”

•

Photosynthesis Equation
6CO
2
Carbon dioxide
Sunlight energy
+ 6 H
2
O C
6
H
12
O
6 water Glucose
(sugar)
(food)
+ 6O
2 oxygen
(raw ) materials (products)

Capturing the Sun’s Energy
• The green color in plants come from the main pigment which is chlorophyll. Other pigments (red, yellow, orange) are also found in the leaf, but chlorophyll masks these colors until it dissolves in the fall season.

•

•
Stomata are openings on the underside of leaves to control the movement of carbon dioxide, oxygen, and water vapor.

Guard cells
Stomata-plural
Stoma-singular

What happens to the products of photosynthesis in plants?
• Plant cells use some of the sugar for food. The cell’s mitochondria break down the sugar molecules to get energy in order to carry out all the plant’s functions for living.
• Some sugar molecules are converted into other compounds like cellulose or starch.
• Oxygen is given off and is used by organisms for respiration. (21% of Earth’s atmosphere is oxygen.)

Respiration
(Cellular Respiration)
The process in which cells break down simple food molecules
(glucose) and releases energy
.

Respiration Equation
C
6
H
12
O
6
+ 6O
2
6CO
2
+ 6H
2
O + ENERGY glucose oxygen carbon water
(sugar) dioxide
(food) raw materials products

The word “respiration” often refers to breathing. Breathing brings in oxygen which is necessary for cellular respiration to occur in most cells.
• Aerobic respiration uses oxygen.
body
• Anaerobic respiration does not use oxygen.
• Example: cells in your
• Example: yeast during fermentation

Nearly all living things obtain energy either directly or indirectly from the sun.
Directly=autotrophs
Indirectly=heterotrophs

The mitochondria or “powerhouse” of the cell is where cellular respiration takes place.

Photosynthesis and respiration can be thought of as opposite processes.

The process that provides the organism with energy without oxygen is called fermentation.
• Amount of energy released from each sugar molecule is much lower than cellular respiration.
• Yeast and some other unicellular organisms produce alcohol as a product of fermentation.
(beer, wine, bread) This is alcoholic fermentation.
• Your muscles can lack enough oxygen that lactic acid forms as a product. This is called lactic-acid fermentation .

Conservation of Mass and
Energy
• Conservation of Mass
Matter cannot be created nor destroyed in chemical reactions.
(The mass of reactants must always equal the mass of the products.
Equations must balance.)
• Conservation of Energy
Energy cannot be created nor destroyed. It only changes form. (In photosynthesis, radiant energy is changed to chemical energy in the bond of glucose. The bonds are broken in respiration to release energy for use by the cells.)

Suppose a volcano spewed so much ash into the air that it blocked most of the sunlight that usually strikes Earth. How might this affect the ability of animals to obtain the energy they need to live?
• The ash from the volcano would block the sun and prevent the plants from using energy to make food and produce oxygen.
Plants would die out when they could not produce their own food during photosynthesis. Then the heterotrophs would die from lack of food and oxygen produced by the autotrophs. Eventually the entire food web would be affected.

Explain the demonstration of diffusion using the dialysis tubing, iodine, and cornstarch. Explain what happened to the iodine molecules and the cornstarch molecules. Which molecules moved through the tubing and how could you tell?
• The process of diffusion was demonstrated using iodine, cornstarch, and dialysis tubing. A dialysis tubing was filled with cornstarch and water. It was placed into a beaker of iodine. The iodine molecules were small enough to pass through the holes of the dialysis tubing. The tubing would be a selectively permeable membrane because only the iodine passed through. The iodine moved from a high concentration to a low concentration. (Iodine molecules were higher on the outside of the bag and lower on the inside of the bag.) The cornstarch molecules were too big to pass through. This was evident when the iodine went into the bag turning the cornstarch purple. The cornstarch did not come out of the bag because the iodine in the beaker stayed the same color.