Photosynthesis Overview Quiz

Capturing Solar Energy

• Photosynthesis is the process by which photosynthetic organisms capture sunlight to make food
• Sunlight provides the energy for photosynthesis
• Photosynthetic organisms are the ultimate source of food for all life
• Photosynthesis is an endergonic process capturing light energy converting into chemical energy in glucose molecules.
• Photosynthesis is an anabolic process

Where Does Photosynthesis Take Place?

• Photosynthesis occurs in the chloroplasts of plant cells
• Chloroplasts are found in leaf cells, specifically in mesophyll cells.
• Each cell in a leaf has 40-100 chloroplasts
• Chloroplasts have an outer membrane, inner membrane, stroma and thylakoids

Photosynthesis Background Information

• Solar radiation is measured by its wavelength
• Photons are discrete packets of radiant energy that travel in waves
• Visible light is a portion of the electromagnetic spectrum, and it's the PAR (photosynthetically active radiation) region.
• Only 42% of solar radiation that hits Earth's atmosphere reaches the surface, mostly as visible light
• Higher energy wavelengths, like gamma rays, are screened out by the ozone layer in the upper atmosphere
• Lower energy wavelengths, like radio waves, are screened out by water vapor and carbon dioxide
• The energy content of photons is inversely proportional to their wavelength

Light Properties

• Light can be transmitted, reflected, or absorbed
• Pigments absorb specific wavelengths of light and reflect others
• Chlorophyll is a pigment that absorbs red and blue-violet light, reflecting green light and giving plants their green color.
• Chlorophyll b absorbs wavelengths in the blue and red-orange regions, also reflecting green light

Chlorophyll Structure

• Chlorophyll consists of a porphyrin ring and a phytol tail
• The tails are non-polar, and the heads are polar, which accounts for their positioning in the thylakoid membrane
• There is a magnesium atom in the center of the molecule

Photosynthetic Pigments

• Photosynthetic pigments include chlorophylls and carotenoids
• Chlorophyll a is the main pigment involved in photosynthesis
• Chlorophyll b and carotenoids are accessory pigments.
• Accessory pigments capture light energy and transfer energy to chlorophyll to support photosynthesis
• Pigments absorb light energy and transfer it to chlorophyll a to initiate photosynthesis
• Different types of accessory pigments are used depending upon the environment where the organism needs to exist

Photo-excitation and Photo-oxidation

• When chlorophyll absorbs a photon, one of its electrons is boosted to a higher energy state.
• Photo-excitation is when the electrons are excited, but return to their ground state
• Photo-oxidation is when the excited electrons are removed by a primary electron acceptor (PEA).

Photosystem I and Photosystem II

• Photosystem I (P700) absorbs light best at 700nm
• Photosystem II (P680) absorbs light best at 680nm
• Chlorophyll b and carotenoids act as antennae to help collect light energy and transfer energy to chlorophyll a, which is used to begin photosynthesis

Light-Dependent Reactions Summary

• A photon strikes a pigment molecule in photosystems I and II
• Energy is instantly converted from light energy into chemical energy as electrons are lost from chlorophyll.
• A series of redox reactions on an electron transport chain (ETC) package the energy as ATP and NADPH (electron carrier).

Chemiosmosis

• Energy released from passing electrons causes the pumping of protons (H+) against their concentration gradient from the stroma into the thylakoid
• As protons build up, a strong electrochemical gradient is created
• The protons flow through ATP synthase, producing ATP through facilitated diffusion
• The energy released from the movement of protons helps generate ATP

Light Stage/Dark Stage Requirements

• Light Stage Requirements: sunlight, water, chlorophyll, NADP+, ADP+P
• Light Stage Products: oxygen, NADPH, ATP
• Dark Stage Requirements: NADPH from light, ATP, CO2
• Dark Stage Products: ADP + Pi, NADP+, and PGAL (glucose)

Test your knowledge on the process of photosynthesis with this quiz. Explore the roles of chlorophyll, light interactions, and the reactions involved. Perfect for students studying plant biology and ecology!