Photosynthesis Flashcards by Haru Haru

The process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water.

Photosynthesis

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Photosynthesis in plants generally involves the green pigment _______ and generates _________ as a byproduct

chlorophyll
oxygen

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This process is important for the growth and survival of autotrophic organisms, as well as for providing oxygen to the atmosphere

Photosynthesis

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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

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Photosynthesis: Life from _______

Light

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Ancient civilizations, such as the Greeks and Egyptians, noted that plants appeared to “eat” air and sunlight.

17th Century

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(17th century) Ancient civilizations, such as the ______ and ________, noted that plants appeared to “eat” _____ and ______

Greeks and Egyptians
air and sunlight.

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Jan Baptista Van Helmont conducted experiments and concluded that water was the source of a plant’s increased mass.

16th century

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In the 16th century, __________ conducted experiments and concluded that ______ was the source of a plant’s increased mass.

Jan Baptista Van Helmont
water

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-English chemist ________ conducted experiments with a variety of gases, including “__________” (now known as oxygen).

Joseph Priestley
dephlogisticated air

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He observed that plants exposed to sunlight released a gas that could relight a burning candle, which we now recognize as _________.

Joseph Priestley
oxygen

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HETEROTROPHS

• get their energy from eating “others”
• consumers of other organisms
• consume organic molecules

• consumers
• animals
• fungi
• most bacteria

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AUTOTROPHS

• get their energy from “self”
• get energy from sunlight
• use light energy to synthesize organic molecules

• producers
• plants
• photosynthetic bacteria (blue-green algae)

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This obtains raw materials in plants

(Plants structure)
Sunlight
Carbon dioxide
Water
Nutrients

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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

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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

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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

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They are photosynthetic machines that maximize the absorption of light

Leaves

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The leaf is sheathed with an ________ and ________. The exposed surfaces of the epidermal cells are coated with a ________.

• upper and lower epidermis
• cuticle

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The photosynthetic tissues are located between the two epidermal layers and are consequently identified as _________.

(meso, ______; phyll, _____)

mesophyll tissues

(meso, middle; phyll, leaf)

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The ___________ generally consists of one to three layers of ___________.

• upper photosynthetic tissue
• palisade mesophyll cells

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_________ are elongated, cylindrical cells with the long axis perpendicular to the surface of the leaf.

Palisade cells

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Below is the ________, so named because of the prominent air spaces between the cells.

spongy mesophyll

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•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