Photosynthesis: An overview Open your books to chapter 8.2 Biology Mr. Hines

The key cellular process for producing energy is called photosynthesis. Photosynthesis is the process where plants use sunlight to convert Carbon dioxide (CO 2 ) and water (H 2 O) to produce carbohydrates. Carbohydrates have many forms. Glucose, sugar, starch, are all forms of carbohydrate.

How does a plant grow? Where does it get its mass? From the soil? PLANTS DO NOT GET THEIR MASS FROM THE SOIL. The soil simply provides a place where plants grow, gives them support, and provides water and other nutrients. Plants get their mass from combining 1.water and 2.carbon dioxide to form carbohydrates.

Van Helmont’s experiment In the 1600s, Van Helmont measured the mass of the soil before he grew a tree in it. 5 years later, he measured the mass of the tree to be 75 Kilograms – the mass of the soil did not change. He concluded that the mass must have come from water.

Priestley’s experiment In the 1700s, Priestly covered a burning candle with a jar and observed that the flame went out. He concluded that there must be something in the air that the flame needed. He later grew a mint plant inside of the jar, and noticed that the candle could be relit inside the same jar. He further concluded that the plant must produce that which was needed by the flame – Oxygen

Jan Ingenhousz’s experiment Later, Jan Ingenhousz noticed that plants would not produce oxygen without sunlight.

Yeah, Yeah, Yeah, and so forth…. Through further experiments, scientists finally discovered that in the presence of light, plants transform carbon dioxide and water into carbohydrates and release oxygen This process of photosynthesis takes place inside of the chloroplasts.

Light Energy Chloroplast CO 2 + H 2 OSugars + O 2 Section 8-2 Photosynthesis: Reactants and Products

The photosynthesis Equation 6CO 2 + 6H 2 O + sunlight → C 6 H 12 O 6 + 6O 2 This shows the process of photosynthesis at the atomic level. Photosynthesis uses the energy of sunlight to convert water and carbon dioxide to produce high energy sugars and oxygen.

Give 2 reasons why plants are important to other living things.

Light and pigments To further understand photosynthesis, you must understand how plants trap light. White Light is a form of energy that can be broken into 7 component colors. Red, orange, yellow, green, blue, indigo, violet Roy G Biv

There is a molecule inside of the chloroplasts called chlorophyll. Chlorophyll molecules trap light from the sun. There are 2 kinds of chlorophyll chlorophyll a chlorophyll b Chlorophyll a and b will absorb slightly different colors from the light spectrum

Absorption of Light by Chlorophyll a and Chlorophyll b VBGYOR Chlorophyll b Chlorophyll a Section 8-2 Figure 8-5 Chlorophyll Light Absorption

Chlorophyll a mostly absorbs light in the violet and red spectrum. Chlorophyll b most absorbs light in the blue and orange spectrum. Notice that neither absorbs green light. Green light is not absorbed, but reflected. This is why plants are green.

Where did the term “carbohydrate” come from? Another term for water is “hydrate.” When you drink water, you are “hydrating” yourself. If you don’t drink water, you become “dehydrated.” Remember, carbohydrates are made with water and carbon dioxide. Guess where the “carbo” comes from?