Biology » Photosynthesis » Overview of Photosynthesis

Summarizing the Photosynthesis Overview

Summary

The process of photosynthesis transformed life on Earth. By harnessing energy from the sun, photosynthesis evolved to allow living things access to enormous amounts of energy. Because of photosynthesis, living things gained access to sufficient energy that allowed them to build new structures and achieve the biodiversity evident today.

Only certain organisms, called photoautotrophs, can perform photosynthesis; they require the presence of chlorophyll, a specialized pigment that absorbs certain portions of the visible spectrum and can capture energy from sunlight.

Photosynthesis uses carbon dioxide and water to assemble carbohydrate molecules and release oxygen as a waste product into the atmosphere.

Eukaryotic autotrophs, such as plants and algae, have organelles called chloroplasts in which photosynthesis takes place, and starch accumulates.

In prokaryotes, such as cyanobacteria, the process is less localized and occurs within folded membranes, extensions of the plasma membrane, and in the cytoplasm.

Glossary

chemoautotroph

organism that can build organic molecules using energy derived from inorganic chemicals instead of sunlight

chloroplast

organelle in which photosynthesis takes place

granum

stack of thylakoids located inside a chloroplast

heterotroph

organism that consumes organic substances or other organisms for food

light-dependent reaction

first stage of photosynthesis where certain wavelengths of the visible light are absorbed to form two energy-carrying molecules (ATP and NADPH)

light-independent reaction

second stage of photosynthesis, though which carbon dioxide is used to build carbohydrate molecules using energy from ATP and NADPH

mesophyll

middle layer of chlorophyll-rich cells in a leaf

photoautotroph

organism capable of producing its own organic compounds from sunlight

pigment

molecule that is capable of absorbing certain wavelengths of light and reflecting others (which accounts for its color)

stoma

opening that regulates gas exchange and water evaporation between leaves and the environment, typically situated on the underside of leaves

stroma

fluid-filled space surrounding the grana inside a chloroplast where the light-independent reactions of photosynthesis take place

thylakoid

disc-shaped, membrane-bound structure inside a chloroplast where the light-dependent reactions of photosynthesis take place; stacks of thylakoids are called grana

thylakoid lumen

aqueous space bound by a thylakoid membrane where protons accumulate during light-driven electron transport

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