Biology Chapter 8: Photosynthesis

Vocabulary flashcards covering the process of photosynthesis, light properties, photosynthetic pigments, the light-dependent reactions, and the Calvin Cycle based on lecture notes.

Photosynthesis

A process that converts light energy to chemical energy in food, nourishing almost the entire living world through an endergonic reaction.

Photoautotrophs

Organisms that require only water, $CO_2$, minerals, and light to synthesise organic molecules, including plants, algae, certain protists like euglena, and bacteria like cyanobacteria.

Photosynthesis Equation

The chemical equation represented as $6CO_2 + 6H_2O + \text{sunlight} \rightarrow C_6H_{12}O_6 + O_2$.

Chloroplasts

Organelles that serve as the site of photosynthesis, found in unripened fruit, stems, and leaves, containing the pigment chlorophyll.

Endergonic

A type of reaction that uses energy, such as sunlight in photosynthesis, to build molecules.

Wavelength

The distance between two wave crests of electromagnetic energy which determines the color of the light.

Electromagnetic spectrum

The full range of all wavelengths of electromagnetic energy.

Visible light

The form of electromagnetic energy that can be detected by the human eye.

Photons

Particles or packets of light with a fixed quantity of energy that is inversely proportional to its wavelength.

Pigments

Substances that absorb certain wavelengths of visible light and reflect others; they appear the color that they reflect.

Thylakoid membrane

The specific location within the chloroplast where photosynthetic pigments are located.

Chlorophyll A

The most important photosynthetic pigment that participates directly in light dependent reactions, appearing blue-green and effectively absorbing red and violet-blue light.

Chlorophyll B

An olive green accessory pigment that helps to extend the range of wavelengths able to be used in photosynthesis.

Carotenoids

Yellow-orange accessory pigments whose main role is protecting the chloroplasts from excessively strong light.

Excited state

A state in which electrons of chlorophyll have absorbed energy and jumped to a higher energy level.

Ground state

The normal energy level an electron returns to after releasing absorbed energy as heat and light (fluorescence).

Photosystems

Functional units composed of a reaction center complex surrounded by light harvesting complexes that utilize various pigments to absorb electromagnetic spectrum energy.

Photosystem II (PSII)

The first of two photosystems in the light reactions, containing chlorophyll a molecules known as $P680$ which best absorb light at $680\,nm$.

P680

The specific chlorophyll a molecules in Photosystem II best able to absorb red light of the $680\,nm$ wavelength.

Photosystem I (PSI)

The second photosystem in the sequence of light reactions, containing chlorophyll a molecules known as $P700$ (far red).

Light Dependent Reactions

The phase of photosynthesis that harnesses sunlight to regenerate $ATP$ and $NADPH$, utilizing an electron transport chain and the splitting of water.

ATP synthase

The enzyme that generates $ATP$ using an $H^+$ gradient created by the electron transport chain during light reactions.

The Calvin Cycle

An anabolic, light-independent reaction taking place in the stroma that builds carbohydrates from smaller molecules while consuming $ATP$ and $NADPH$.

Stroma

The fluid-filled space within the chloroplast where the Calvin Cycle occurs.

Carbon Fixation

Phase 1 of the Calvin Cycle involving the initial incorporation of $CO_2$ into organic material.

Reduction (Calvin Cycle)

Phase 2 of the Calvin Cycle where $NADPH$ provides electrons for the reduction of carbon-containing compounds to produce $G3P$.

Regeneration (Calvin Cycle)

Phase 3 of the Calvin Cycle where the carbon-acceptor ($RuBP$) is produced from $G3P$ to begin the cycle again.

RUBISCO

Also known as RuBP Carboxylase, the enzyme that catalyzes the first step of the Calvin Cycle.

RuBP

A 5-carbon molecule that acts as the carbon-acceptor in the Calvin Cycle and is regenerated at the end of the cycle.

G3P

A 3-carbon sugar produced in the Calvin Cycle; one molecule leaves the cycle as sugar while others are used for regeneration.

Oxidation (Photosynthesis)

Specifically, the part of the redox reaction in photosynthesis where $6H_2O$ is converted into $O_2$.

Reduction (Photosynthesis)

Specifically, the part of the redox reaction in photosynthesis where $6CO_2$ is converted into $C_6H_{12}O_6$.