Lesson Overview 8.2 Photosynthesis: An Overview
Chlorophyll and Chloroplasts What role do pigments play in the process of photosynthesis? Photosynthetic organisms capture energy from sunlight with pigments.
Light Energy from the sun travels to Earth in the form of light. Sunlight is a mixture of different wavelengths, many of which are visible to our eyes and make up the visible spectrum.
Light Our eyes see the different wavelengths of the visible spectrum as different colors: red, orange, yellow, green, blue, indigo, and violet.
Pigments Plants gather the sun s energy with pigments: light-absorbing molecules. The plants principal pigment is chlorophyll.
Pigments The two types of chlorophyll found in plants, chlorophyll a and chlorophyll b, absorb light very well in the blue-violet and red regions of the visible spectrum, but not in the green region, as shown in the graph. Leaves reflect green light, which is why plants look green.
Pigments Plants also contain red and orange pigments such as carotene that absorb light in other regions of the spectrum.
Pigments Most of the time, the green color of the chlorophyll overwhelms the other pigments, but as temperatures drop and chlorophyll molecules break down, the red and orange pigments may be seen.
Chloroplasts Photosynthesis takes place inside organelles called chloroplasts. Chloroplasts contain thylakoids: saclike photosynthetic membranes, which are interconnected and arranged in stacks known as grana.
Chloroplasts Pigments are located in the thylakoid membranes. The fluid portion outside of the thylakoids is known as the stroma.
An Overview of Photosynthesis What are the reactants and products of photosynthesis?
An Overview of Photosynthesis Photosynthesis uses the energy of sunlight to convert water and carbon dioxide (reactants) into high-energy sugars and oxygen (products). In words: Carbon dioxide + Water Sugars + Oxygen In symbols: 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2
An Overview of Photosynthesis Plants use photosynthesis to produce complex carbohydrates These provide energy for the synthesis of other compounds, including proteins and lipids.
Light-Dependent Reactions Photosynthesis involves two sets of reactions. The first set of reactions is known as the lightdependent reactions 1. take place within the thylakoid membranes of the chloroplast.
Light-Dependent Reactions 2. use energy from sunlight to produce ATP and NADPH.
Light-Dependent Reactions 3. Water is required as a source of electrons and hydrogen ions. 4. Oxygen is released as a byproduct.
Summary of Light-Dependent Reactions -The light-dependent reactions produce oxygen gas and convert ADP and NADP + into the energy carriers ATP and NADPH. -ATP and NADPH provide the energy needed to build high-energy sugars from low-energy carbon dioxide.
Light-Independent Reactions: THE CALVIN CYCLE During light-independent reactions, ATP and NADPH molecules produced in the lightdependent reactions are used to produce high-energy sugars from carbon dioxide.
Light-Independent Reactions No light is required to power the lightindependent reactions. The light-independent reactions take place outside the thylakoids, in the stroma.
Summary of the Light Independent Reactions/Calvin Cycle 1. The energy for the reactions comes from the product of the light-dependent reactions 2. Uses 6 molecules of carbon dioxide to produce a single 6-carbon sugar molecule.
10_05Photosynthesis.mpg -The plant uses the sugars produced by the Calvin cycle to make ATP -When other organisms eat plants, they can use sugars to also make ATP
Factors Affecting Photosynthesis What factors affect photosynthesis? Among the most important factors that affect photosynthesis are: 1. Temperature 2. Light intensity 3. Availability of water.
Temperature, Light, and Water The reactions of photosynthesis are made possible by enzymes that function best between 0 C and 35 C (32 F and 95 F). Temperatures above or below this range may affect those enzymes, slowing down the rate of photosynthesis or stopping it entirely.
Temperature, Light, and Water High light intensity increases the rate of photosynthesis. After the light intensity reaches a certain level, the plant reaches its maximum rate of photosynthesis, as is seen in the graph.