Biology 1414 Lecture 10: Photosynthesis and the Energy Cycle

A complete set of vocabulary flashcards covering the core concepts, structures, and chemical processes of photosynthesis from Lecture 10.

Photosynthesis

The only biological process that can capture sunlight and convert it into chemical compounds; vital to nearly all life on Earth.

Autotroph

An organism capable of making its own food.

Photoautotroph

Organisms such as plants, algae, and cyanobacteria that use light to manufacture their own food.

Chemoautotrophs

A small group of bacteria that obtain energy by extracting it from inorganic chemical compounds.

Heterotrophs

Organisms such as animals, fungi, and most bacteria that rely on sugars produced by other organisms for energy.

Mixotrophs

Organisms that use both autotrophy and heterotrophy, such as the Solar Powered Sea Slug.

Mesophyll

The middle most layer of a leaf where photosynthesis occurs.

Stomata (Stoma)

Small regulated pores, usually located on the lower surface of the leaf, that regulate gas exchange and water balance.

Guard cells

Cells that surround the stoma and swell or shrink based on osmotic pressure to regulate the opening and closing of the pore.

Chloroplasts

Organelles in all autotrophic eukaryotes where photosynthesis occurs, featuring a double membrane derived from ancient free-living cyanobacteria.

Thylakoids

Disc-shaped structures inside chloroplasts that contain chlorophyll and proteins making up the electron transport chain.

Chlorophyll

A pigment molecule responsible for the initial interaction of light and the plant.

Thylakoid lumen

The internal space of a thylakoid defined by the thylakoid membrane.

Granum

A stack of thylakoids.

Stroma

The liquid surrounding the granum inside the chloroplast where the light-independent reactions occur.

Light-dependent reaction

The stage of photosynthesis where energy is absorbed by chlorophyll and converted into stored chemical energy.

Light-independent reaction

The stage of photosynthesis, also called the Calvin Cycle, where stored energy drives the assembly of sugar molecules from $CO_2$.

Wavelength

The distance between consecutive crest points of a wave; shorter wavelengths correspond to more energy.

Electromagnetic spectrum

The range of all possible frequencies or wavelengths of radiation.

Photosynthetically Active Radiation (PAR)

The range of wavelengths between $400-700\,nm$ that plants are able to absorb to power photosynthesis.

Carotenoids

A class of photosynthetic pigments that supply bright colors and function to dispose of excess energy as heat to prevent damage in full sun.

Absorption spectrum

The specific wavelengths of visible light a pigment absorbs; used to identify the pigment.

Photosystem

A multiprotein complex found in the thylakoid membrane that converts light energy into chemical energy.

Antenna proteins

Proteins within the light harvesting complex where $300-400$ chlorophyll a and b molecules bind.

Reaction centers

The specific part of the photosystem where photochemistry takes place.

Photon

A distinct quantity or packet of light energy.

Photoact

The process where special chlorophyll a molecules in the reaction center give up an electron during an excited state.

Carbon fixation

The process of converting $CO_2$ from inorganic to organic molecules during the first stage of the Calvin cycle.

RuBisCO

An enzyme that catalyzes the reaction between $CO_2$ and RuBP.

RuBP (Ribulose bisphosphate)

The molecule that reacts with $CO_2$ to initiate the light-independent reaction.

3-PGA

The carbon molecule formed after RuBisCO catalyzes the reaction between $CO_2$ and RuBP.

G3P (glyceraldehyde-3-phosphate)

A simple carbohydrate molecule produced in the Calvin Cycle that can be converted into glucose, sucrose, or other sugar molecules.

C3 plants

Plants that keep stomata open during the day and are more efficient under cool, moist conditions because they require less machinery.

C4 plants

Plants that photosynthesize faster under high light and temperature and have better water use efficiency by closing stomata when $CO_2$ levels are high.

CAM plants

Succulent plants adapted to arid conditions that open stomata at night and keep them closed during the day to minimize evapotranspiration.