General Biology Final Exam
Photosythesis
Photosynthesis is the process that converts solar (light) energy into chemical energy of food. The
light reactions convert solar energy to the chemical energy of ATP and NADPH. The calvin
cylcle uses he chemical energy of ATP and NADPH to reduce CO2 to sugar. Directly or
indirectly, photosynthesis nourishes almost the entire living world.
Photosynthesis is a complex series of reactions that can be summarized as the following
equation: 6 CO2 + 12 H2O + Light energy = C6H12O6 + 6 O2 + 6 H2O
Autotrophs are „self-feeders“ and they sustain themselves without eating anything derived from
other organisms. They produce their organic molecules from CO2 and other inorganic raw
materials obtained from the environment. Autotrophs are the producers of the biosphere. Almost
all plants are photoautotrophs, using the energy of sunlight to make organic molecules.
Photosynthesis also occurs in algae, certain other unicellular eukaryotes and some prokaryotes.
Heterotrophs obtain their organic material from other organisms, they are unable to make their
own food. Heterotrophs are the consumers of the biosphere. Almost all heterotrophs, including
humans, depend on photoautotrophs for food and O2. The Earth’s supply of fossil fuels was
formed from the remains of organisms that died hundreds of millions of years ago. In a sense,
fossil fuels represent stores of solar energy from the distant past.
Photosynthesis converts light energy to the chemical energy of food
Chloroplasts are structurally similar to and likely evolved from photosynthetic bacteria.The
structural organization of these cells allows for the chemical reactions of photosynthesis. They
are present in variety of photosythesizing organisms.
Chloroplasts: The Sites of Photosynthesis in Plants
Leaves are the major locations of photosynthesis. Their green color is from chlorophyll, the
green pigment within chloroplasts. Chloroplasts are found mainly in cells of the mesophyll, the
interior tissue of the leaf. Each mesophyll cell contains 30–40 chloroplasts. CO2 enters and O2
exits the leaf through microscopic pores called stomata. Chloroplasts also contain stroma, a
dense interior fluid. The chlorophyll is in the membranes of thylakoids which segregate the
stroma from the thylakoid space inside sacs (connected sacs in the chloroplast); thylakoids may
be stacked in columns called grana.
,The Splitting of Water
Chloroplasts split H2O into hydrogen and oxygen, incorporating the electrons of hydrogen into
sugar molecules and releasing oxygen as a by-product.
Photosynthesis as a Redox Process
Photosynthesis reverses the direction of electron flow compared to respiration. Photosynthesis is
a redox process in which H2O is oxidized and CO2 is reduced. Photosynthesis is an endergonic
process; the energy boost is provided by light.
The Two Stages of Photosynthesis: A Preview
Photosynthesis consists of the light reactions (the photo part) and Calvin cycle (the synthesis
part). The light reactions (in the thylakoids):
- Convert solar energy to chemical energy
- Split H2O
- Release O2
- Light reactions use solar energy to reduce NADP+ to NADPH
- Light reactions generate ATP from ADP by photophosphorylation
- Result is NADPH and
ATP The Calvin cycle (in the
stroma):
- Forms sugar from CO2, using ATP and NADPH
- Begins with carbon fixation, incorporating CO2 into organic molecules
- Reduces the fixed carbon to carbohydrate
- To convert CO2 to carbohydratem it needs chemical energy (ATP)
- Result is sugar
- None of the steps requires light directly
- Occurs during daylight
, The light reactions convert solar energy to the chemical energy of ATP and NADPH
Chloroplasts are solar-powered chemical factories. Their thylakoids transform light energy into
the chemical energy of ATP and NADPH, which will be used to synthesize glucose and other
molecules that can be used as energy sources.
The Nature of Sunlight
Light is a form of electromagnetic energy, also called electromagnetic radiation. Like other
electromagnetic energy, light travels in rhythmic waves. Wavelength is the distance between
crests (greben) of waves. Wavelength determines the type of electromagnetic energy. The
electromagnetic spectrum is the entire range of electromagnetic energy, or radiation.Visible light
(from 380nm to 750 nm) consists of wavelengths (including those that drive photosynthesis) that
produce colors we can see. Light also behaves as though it consists of discrete particles, called
photons.
The shorter the wavelength, the greater the energy of
each photon of that light.
Photosynthetic Pigments: The Light Receptors
Pigments are substances that absorb visible light. Different pigments absorb different
wavelengths. There are three types of pigments in chloroplast: chlorophyll a (the key light-
capturing pigment in light reactions), chlorophyll b (the accessory pigment, broaden the
spectrum used for photosythesis), and cartenoids (separate group of accessory pigments, absorb
excessive light that would damage chlorophyll). Wavelengths that are not absorbed are reflected
or transmitted. Leaves appear green because chlorophyll reflects and transmits green light.
A spectrophotometer measures a pigment’s ability to absorb various wavelengths. This machine
sends light through pigments and measures the fraction of light transmitted at each wavelength.
1. White light is separated into colors by a prism.
2. One by one, the different colors of light are passed through the sample.
3. The transmitted light strikes a photoelectric tube, which converts the light energy to electricity.
4. The electric current is measured by a galvanometer. The meter indicates the fraction of the
light transmitted thorough the sample, from which we can determine the amount of light
Photosythesis
Photosynthesis is the process that converts solar (light) energy into chemical energy of food. The
light reactions convert solar energy to the chemical energy of ATP and NADPH. The calvin
cylcle uses he chemical energy of ATP and NADPH to reduce CO2 to sugar. Directly or
indirectly, photosynthesis nourishes almost the entire living world.
Photosynthesis is a complex series of reactions that can be summarized as the following
equation: 6 CO2 + 12 H2O + Light energy = C6H12O6 + 6 O2 + 6 H2O
Autotrophs are „self-feeders“ and they sustain themselves without eating anything derived from
other organisms. They produce their organic molecules from CO2 and other inorganic raw
materials obtained from the environment. Autotrophs are the producers of the biosphere. Almost
all plants are photoautotrophs, using the energy of sunlight to make organic molecules.
Photosynthesis also occurs in algae, certain other unicellular eukaryotes and some prokaryotes.
Heterotrophs obtain their organic material from other organisms, they are unable to make their
own food. Heterotrophs are the consumers of the biosphere. Almost all heterotrophs, including
humans, depend on photoautotrophs for food and O2. The Earth’s supply of fossil fuels was
formed from the remains of organisms that died hundreds of millions of years ago. In a sense,
fossil fuels represent stores of solar energy from the distant past.
Photosynthesis converts light energy to the chemical energy of food
Chloroplasts are structurally similar to and likely evolved from photosynthetic bacteria.The
structural organization of these cells allows for the chemical reactions of photosynthesis. They
are present in variety of photosythesizing organisms.
Chloroplasts: The Sites of Photosynthesis in Plants
Leaves are the major locations of photosynthesis. Their green color is from chlorophyll, the
green pigment within chloroplasts. Chloroplasts are found mainly in cells of the mesophyll, the
interior tissue of the leaf. Each mesophyll cell contains 30–40 chloroplasts. CO2 enters and O2
exits the leaf through microscopic pores called stomata. Chloroplasts also contain stroma, a
dense interior fluid. The chlorophyll is in the membranes of thylakoids which segregate the
stroma from the thylakoid space inside sacs (connected sacs in the chloroplast); thylakoids may
be stacked in columns called grana.
,The Splitting of Water
Chloroplasts split H2O into hydrogen and oxygen, incorporating the electrons of hydrogen into
sugar molecules and releasing oxygen as a by-product.
Photosynthesis as a Redox Process
Photosynthesis reverses the direction of electron flow compared to respiration. Photosynthesis is
a redox process in which H2O is oxidized and CO2 is reduced. Photosynthesis is an endergonic
process; the energy boost is provided by light.
The Two Stages of Photosynthesis: A Preview
Photosynthesis consists of the light reactions (the photo part) and Calvin cycle (the synthesis
part). The light reactions (in the thylakoids):
- Convert solar energy to chemical energy
- Split H2O
- Release O2
- Light reactions use solar energy to reduce NADP+ to NADPH
- Light reactions generate ATP from ADP by photophosphorylation
- Result is NADPH and
ATP The Calvin cycle (in the
stroma):
- Forms sugar from CO2, using ATP and NADPH
- Begins with carbon fixation, incorporating CO2 into organic molecules
- Reduces the fixed carbon to carbohydrate
- To convert CO2 to carbohydratem it needs chemical energy (ATP)
- Result is sugar
- None of the steps requires light directly
- Occurs during daylight
, The light reactions convert solar energy to the chemical energy of ATP and NADPH
Chloroplasts are solar-powered chemical factories. Their thylakoids transform light energy into
the chemical energy of ATP and NADPH, which will be used to synthesize glucose and other
molecules that can be used as energy sources.
The Nature of Sunlight
Light is a form of electromagnetic energy, also called electromagnetic radiation. Like other
electromagnetic energy, light travels in rhythmic waves. Wavelength is the distance between
crests (greben) of waves. Wavelength determines the type of electromagnetic energy. The
electromagnetic spectrum is the entire range of electromagnetic energy, or radiation.Visible light
(from 380nm to 750 nm) consists of wavelengths (including those that drive photosynthesis) that
produce colors we can see. Light also behaves as though it consists of discrete particles, called
photons.
The shorter the wavelength, the greater the energy of
each photon of that light.
Photosynthetic Pigments: The Light Receptors
Pigments are substances that absorb visible light. Different pigments absorb different
wavelengths. There are three types of pigments in chloroplast: chlorophyll a (the key light-
capturing pigment in light reactions), chlorophyll b (the accessory pigment, broaden the
spectrum used for photosythesis), and cartenoids (separate group of accessory pigments, absorb
excessive light that would damage chlorophyll). Wavelengths that are not absorbed are reflected
or transmitted. Leaves appear green because chlorophyll reflects and transmits green light.
A spectrophotometer measures a pigment’s ability to absorb various wavelengths. This machine
sends light through pigments and measures the fraction of light transmitted at each wavelength.
1. White light is separated into colors by a prism.
2. One by one, the different colors of light are passed through the sample.
3. The transmitted light strikes a photoelectric tube, which converts the light energy to electricity.
4. The electric current is measured by a galvanometer. The meter indicates the fraction of the
light transmitted thorough the sample, from which we can determine the amount of light
