Photosynthesis Flashcards
The process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water.
Photosynthesis
Photosynthesis in plants generally involves the green pigment _______ and generates _________ as a byproduct
chlorophyll
oxygen
This process is important for the growth and survival of autotrophic organisms, as well as for providing oxygen to the atmosphere
Photosynthesis
PHOTOSYNTHESIS
• The process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water.
• Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a byproduct
• The process photosynthesis is important for the growth and survival of autotrophic organisms, as well as for providing oxygen to the atmosphere
Photosynthesis: Life from _______
Light
Ancient civilizations, such as the Greeks and Egyptians, noted that plants appeared to “eat” air and sunlight.
17th Century
(17th century) Ancient civilizations, such as the ______ and ________, noted that plants appeared to “eat” _____ and ______
Greeks and Egyptians
air and sunlight.
Jan Baptista Van Helmont conducted experiments and concluded that water was the source of a plant’s increased mass.
16th century
In the 16th century, __________ conducted experiments and concluded that ______ was the source of a plant’s increased mass.
Jan Baptista Van Helmont
water
-English chemist ________ conducted experiments with a variety of gases, including “__________” (now known as oxygen).
Joseph Priestley
dephlogisticated air
He observed that plants exposed to sunlight released a gas that could relight a burning candle, which we now recognize as _________.
Joseph Priestley
oxygen
HETEROTROPHS
• get their energy from eating “others”
• consumers of other organisms
• consume organic molecules
• consumers
• animals
• fungi
• most bacteria
AUTOTROPHS
• get their energy from “self”
• get energy from sunlight
• use light energy to synthesize organic molecules
• producers
• plants
• photosynthetic bacteria (blue-green algae)
This obtains raw materials in plants
(Plants structure)
Sunlight
Carbon dioxide
Water
Nutrients
PLANT STRUCTURE
• Obtaining raw materials
◆ sunlight
_______=_______
◆ CO2
_________ = _________
◆ H2O
___________
◆ nutrients
___________
◆ sunlight
sunlight = solar collectors
◆ CO2
stomates = gas exchange
◆ H2O
uptake from roots
◆ nutrients
uptake from roots
What does it mean to be a plant?
■Need to…
◆ collect light energy
transform it into chemical energy
◆ store light energy
in a stable form to be moved around the plant & also saved for a rainy day
◆ need to get building block atoms from the environment
C,H,O,N,P,S
◆ produce all organic molecules needed for growth
carbohydrates, proteins, lipids, nucleic acids
Plant structure
■ Chloroplasts
◆
◆
◆
◆
■ Chlorophyll & ETC in thylakoid membrane
◆
■ Chloroplasts
◆ double membrane
◆ stroma
◆ thylakoid sacs
◆ grana stacks
■ Chlorophyll & ETC in thylakoid membrane
◆ H+ gradient built up within thylakoid sac
They are photosynthetic machines that maximize the absorption of light
Leaves
The leaf is sheathed with an ________ and ________. The exposed surfaces of the epidermal cells are coated with a ________.
• upper and lower epidermis
• cuticle
The photosynthetic tissues are located between the two epidermal layers and are consequently identified as _________.
(meso, ______; phyll, _____)
mesophyll tissues
(meso, middle; phyll, leaf)
The ___________ generally consists of one to three layers of ___________.
• upper photosynthetic tissue
• palisade mesophyll cells
_________ are elongated, cylindrical cells with the long axis perpendicular to the surface of the leaf.
Palisade cells
Below is the ________, so named because of the prominent air spaces between the cells.
spongy mesophyll
•The energy for photosynthesis comes from the ______.
•Sunlight has both ______ and _______.
•Particles are called _______–are the smallest unit of light.
• sun
• wave and particle nature
• photons
The light emitted from the sun contains photons in a wide spectrum of wavelengths, called the __________
electromagnetic spectrum
Photosynthetic organisms use only a short portion of the electromagnetic spectrum called ________.
visible light
Contains pigment that facilitate the capture of wavelength from light in the visible light range.
Photosynthetic organisms
Photosynthetic organisms contains ________ that facilitate the capture of ________ from light in the _________.
pigment
wavelength
visible light range
•The color of the pigment comes from the ________ of __________.
•Plants appear green because they reflect __________ wavelengths of light.
•__________ wavelengths are absorbed and provide the energy needed that is used for photosynthesis.
wavelengths
light reflected
yellow and green
Red and blue
Chloroplast are green because they absorb ___________ in red & blue and reflect green back out
light wavelengths
Photosynthesis performs work only with __________
◆ ____________ - the dominant pigment- absorbs best in ____& _____ wavelengths & least in ______
◆ other pigments with different structures have different absorption spectra
• absorbed wavelengths of light
• chlorophyll a
• red & blue wavelengths & least in green
• Carbon dioxide and water are converted into ______ and _______, driven by the energy of sunlight captured by chlorophyll and other pigments.
• This process is essential for the production of _______ and ________ that sustain life on Earth.
• glucose and oxygen
• energy and organic compounds
CHEMICAL FORMULA (Photosynthesis)
6CO2 + 6H2O
C6 H12 O6 + 6O2
This molecules are taken in from the surrounding environment.
Carbon dioxide (6CO2)
This is absorbed by chlorophyll and other pigments in the chloroplasts.
Water 6H2O
• It is the primary product of photosynthesis and serves as an energy-rich molecule for the cell.
• It is a simple sugar
Glucose (C6 H12 O6)
________ is released as a byproduct of photosynthesis and is released into the atmosphere.
Oxygen (6O2)
The reactions that synthesize glucose occurs in the _______
stroma
The light dependent reactions occurs in the ________.
thylakoids
Convert solar energy to chemical energy (NADPH & ATP)
Light reactions
Uses chemical energy (NADPH & ATP) to reduce CO2 to C6 H12 O6 (sugars)
Calvin cycle
Collects chlorophyll molecules
Photosystems
Act as light gathering “anthena complex”
2 photosystems of thylakoid membrane (Photosystems l & ll)
• Chlorophyll a
• P680 = absorbs 680 nm wavelength red light
Photosystem ll
• Chlorophyll b
• P700 = absorbs 700nm wavelength red light
Photosystem l
The key to the photosynthetic electron transport chain is the presence of two large, multimolecular, pigment-protein complexes known as _________ and ________
photosystem I (PSI) and photosystem II (PSII).
Photosystems l and ll operate in series linked by a third multiprotein aggregate called the _________.
cytochrome complex
The effect of the chain is to extract low-energy electrons from water and, using light energy trapped by chlorophyll, raise the energy level of those electrons to produce a strong reductant _______.
NADPH
Fractionation studies have revealed that PSI and PSII each contain several different proteins together with a collection of _________ and __________ that absorb photons.
chlorophyll and carotenoid molecules
The bulk of the chlorophyll in the photosystem functions as ________.
antenna chlorophyll
The association of chlorophyll with specific proteins forms a number of different _______________
chlorophyll-protein (CP) complexes
Photosystems (process)
• The photosystems of the thylakoid consist of _________ and ______ - the molecules that absorb the photons of light.
• Within the pigment molecules, the absorbed ______ excites ________ to a higher state.
• Photosystems will channel the excitation energy gathered by the pigment molecules to a reaction _________ which will then pass the electrons to a series of proteins located at the thylakoid membrane.
-Photons of light strike Photosystems I and II simultaneously.
• accessory pigment molecule and chlorophyll
• light energy
• electrons
• centerchlorophyll molecule
PHOTOSYSTEM ll
• The core antenna for photosystem II consists of two chlorophyll-proteins (CP) known as ______ and _____.
• These two CP complexes each contain _____ to _____ of chlorophyll a.
• The ______________ absorb light but do not participate directly in photochemical reaction
• CP43 and CP47
• 20 to 25 molecules
• core antenna chlorophyll a
REACTION CENTER CHLOROPHYLL
• The reaction center chlorophyll plus associated proteins are directly involved in _____________.
• It is an ________—it is the longest-wavelength, thus the lowest-energy-absorbing chlorophyll in the complex.
• Because the _____________ is the site of the primary photochemical redox reaction, it is here that light energy is actually converted to chemical energy.
• The reaction center chlorophyll a of PSI and PSII are designated as ______ and ______, respectively. These designations identify the reaction center chlorophyll a, or pigment (P), with an absorbance maximum at either 700 nm (PSI) or 680 nm (PSII).
• lightdriven redox reactions
• energy sink
• reaction center chlorophyll a
• P700 and P680
PHOTOSYSTEM II OXIDIZES WATER TO PRODUCE OXYGEN
• Electron transport actually begins with the arrival of _______ at the photosystem II reaction center chlorophyll, P680, which is located near the ________ of the reaction center.
- _______ is required to change the redox potential of P680 from +0.8 eV to about −0.4 eV for P680, the excited form of P680. As a consequence of this initial endergonic excitation process, P680 can rapidly (within picoseconds, 10−12 s) transfer electrons exergonically to _______ (Pheo).
• excitation energy
• lumenalside
• excitation energy
• pheophytin
PHOTOSYSTEMII OXIDIZES WATER TO PRODUCE OXYGEN
• Since this initial oxidation of P680 is light dependent, this is called a ___________, which results in the formation of P680+ and Pheo−, a charge separation. This charge separation effectively stores light energy as redox potential energy and represents the actual conversion of light energy to chemical energy.
• The role of the reaction proteins, D1 and D2, is to bind and to orient specific redox carriers of the PSII reaction center in such a way as to decrease the probability of charge recombination between P680+ and Pheo−.
• photooxidation event
Z-SCHEME FOR PHOTOSYNTHETIC ETC
• The redox components are arranged according to their approximate __________. The vertical direction indicates a change in ______’’ .
• The horizontal direction indicates electron flow. The net effect of the process is to use the energy of light to generate a strong reductant, reduced ferredoxin (fd) from the low-energy electrons of water.
• The downhill transfer of electrons between P680* and P700 represents a negative free energy change. Some of this energy is used to establish a proton gradient, which in turn drives ________. Indicated redox potentials are only approximate
• midpoint redox potentials.
• energy level
• ATP synthesis
_____________ absorb in- coming photons and transfer the excitation energy to the reaction center where the photochemical oxida- tion-reduction reactions occur.
Antenna chlorophyll molecules
