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Photosynthesis
Photosynthesis
Autotrophs & Heterotrophs
Autotrophs & Heterotrophs
Where do organisms get their energy?
Where do organisms get their energy?
Food! Originally though most food comes from the sun. Plants and some types of organisms are able to use light energy from the sun to produce food.
Food! Originally though most food comes from the sun. Plants and some types of organisms are able to use light energy from the sun to produce food.
Autotrophs
Autotrophs
Organisms that make their own energy source (food). Many of these organisms use light energy from the sun to produce food.
Organisms that make their own energy source (food). Many of these organisms use light energy from the sun to produce food.
Heterotrophs
Heterotrophs
Organisms that cannot make their own energy source (food) and must obtain energy from the foods they consume.
Organisms that cannot make their own energy source (food) and must obtain energy from the foods they consume.
Check out the picture and video below to see some example of HETEROTROPHS and AUTOTROPHS!
Check out the picture and video below to see some example of HETEROTROPHS and AUTOTROPHS!
All organisms--both heterotrophs and autotrophs--must release the energy found in sugar and other compounds in order to power the chemical reactions it needs to survive.
All organisms--both heterotrophs and autotrophs--must release the energy found in sugar and other compounds in order to power the chemical reactions it needs to survive.
PHOTOSYNTHESIS: A process in which plants use the energy sunlight to convert water and carbon dioxide into high-energy carbohydrates (sugars and starches) and oxygen, a waste product.
PHOTOSYNTHESIS: A process in which plants use the energy sunlight to convert water and carbon dioxide into high-energy carbohydrates (sugars and starches) and oxygen, a waste product.
Photosynthesis comes from the Greek words photo, meaning "light" and synthesis, meaning "putting together." Therefore photosynthesis means "using light to put something together", and in this case it's the putting together of carbohydrates.
Need a Catchy Way to Remember the formula?
Need a Catchy Way to Remember the formula?
Watch These Videos!
Watch These Videos!
Light and Pigments
Light and Pigments
Although the photosynthesis equation (seen above) tells us that water and carbon dioxide are needed for photosynthesis, it doesn't tell us how plants use these low energy materials to produce high energy sugars. To understand that, we must first learn how plants capture the energy of sunlight.
In addition to water and carbon dioxide, photosynthesis require light and chlorophyll, a molecule in chloroplasts.
Sunlight, which your eyes perceive as "white-colored" light is actually a mixture of different wavelengths of light. Many of these wavelengths are visible to your eyes and make up what is known as the visible spectrum. Your eyes see the different wavelengths of the visible spectrum as different colors.
PIGMENTS: light-absorbing molecules that allow plants to gather the sun's energy.
PIGMENTS: light-absorbing molecules that allow plants to gather the sun's energy.
CHLOROPHYLL: the principal (main) pigment found in plants.
CHLOROPHYLL: the principal (main) pigment found in plants.
There are two main types of chlorophyll: chlorophyll a and chlorophyll b.
Chlorophyll absorbs light very well in the blue-violet and red regions of the visible spectrum. However, chlorophyll does not absorb light well in the green region of the spectrum.
Green light is reflected by leaves because chlorophyll does NOT absorb light in the green region well, that's why plants look green!
Green light is reflected by leaves because chlorophyll does NOT absorb light in the green region well, that's why plants look green!
Because light is a form of energy, any compound that absorbs light also absorbs the energy from that light.
When chlorophyll absorbs light, much of the energy is transferred directly to electrons in the chlorophyll molecule, raising the energy levels of these electrons. These high-energy electrons make photosynthesis work!
Factors that Can Affect Photosynthesis
Factors that Can Affect Photosynthesis
Water Availability - Because water is one of the materials needed for photosynthesis (a reactant), a shortage of water can slow or even stop the process. Plants with water stress will close their stomata (plant pores)and slow activity.
Temperature – an increase in temperature normally increases photosynthesis up to a certain point. Photosynthesis depends on enzymes that function best between 0 degrees and 35 degrees Celsius. Temperatures above or below this range may denature the enzymes, slowing down or even completely stopping the reaction.
Light Duration – the longer the day, the more photosynthesis takes place, and the more the plant grows.
Carbon Dioxide Concentration – an increase causes a greater rate of photosynthesis.
Light Quality – chlorophyll reacts only to certain wavelengths of light. (See the picture above)
Light Intensity - Increasing light intensity increases the rate of photosynthesis up to a point. After it reaches a certain level the plant will reach a maximum rate of photosynthesis.
Photosynthesis takes place inside chloroplasts!
Photosynthesis takes place inside chloroplasts!
Chloroplasts contain saclike photosynthetic membranes called THYLAKOIDS. Thylakoids are arranged in stacks known as GRANA (singular = GRANUM). The region or space outside of the thylakoid membranes is called the STROMA.
Chloroplasts contain saclike photosynthetic membranes called THYLAKOIDS. Thylakoids are arranged in stacks known as GRANA (singular = GRANUM). The region or space outside of the thylakoid membranes is called the STROMA.
Proteins in the thylakoid membrane organize chlorophyll and other pigments into clusters known as PHOTOSYSTEMS. These photosystems are the light-collecting units of the chloroplasts.
Identify These Structures in the Chloroplasts...
Identify These Structures in the Chloroplasts...
THYLAKOIDS: saclike photosynthetic membranes.
STROMA: the space outside the thylakoid membrane.
GRANUM: stack of thylakoids.
PHOTOSYSTEMS: clusters of pigments and proteins that absorb light energy that are found in thylakoids.
REMEMBER THIS:
REMEMBER THIS:
Photosynthesis is a series of reactions that uses light energy from the sun to convert water and carbon dioxide into sugars and oxygen.
Photosynthesis involves Two Types of Reactions!
Photosynthesis involves Two Types of Reactions!
- The Light-Dependent Reactions
The Light-Dependent Reactions take place within the thylakoid membranes.
- The Calvin Cycle (Light-Independent Reactions)
The Calvin Cycle takes place in the stroma.
The Light-Dependent Reaction
The Light-Dependent Reaction
What Happens?
What Happens?
The Light-Dependent Reactions requires light. (Duh!) The light-dependent reaction uses the energy from light to convert the reactants ADP and NADP+ into the products ATP and NADPH (a special molecule that carries high-energy electrons).
This reaction also converts water into oxygen that is released into the atmosphere!
Reactants and Products
Reactants and Products
Reactants: Light, ADP, NADP+, and Water
Products: ATP, NADPH, and Oxygen
Location of Reactions:
Location of Reactions:
The light-dependent reaction takes place within the thylakoid membranes of the chloroplasts.
The Calvin Cycle
The Calvin Cycle
What Happens?
What Happens?
The ATP and NADPH made by the light-dependent reactions contain a bunch of chemical energy, but they are not stable enough to store that energy for more than a few minutes. So, during the Calvin Cycle organisms use the energy from ATP and NADPH to turn carbon dioxide into glucose (sugar) molecules that can store energy for a longer period of time.
Because the Calvin cycle does not require light, these reactions are also called the light-independent reactions.
Reactants and Products:
Reactants and Products:
Reactants: ATP, NADPH (from light-dependent reaction), & carbon dioxide
Products: ADP, NADP+, and Glucose
Location of Cycle:
Location of Cycle:
The Calvin cycle takes place in the stroma of chloroplasts.
Study Tip:
Study Tip:
Focus on the Reactants and Products of Photosynthesis and of each Reaction!
Focus on the Reactants and Products of Photosynthesis and of each Reaction!
Notice that the Reactants of one reaction are the Products of another!!!
Photosynthesis Review Game
Photosynthesis Review Game
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