3D ATLAS / LIVING SYSTEMS / INNER WORLD 05

Where sunlight
becomes chemistry.

Pass through the translucent envelope of a representative plant chloroplast. Open the stacks that collect light, trace the membrane gradient, and follow carbon into the stroma.

ENVELOPE / STROMA

Choose a research file. Drag to rotate; pinch or use the zoom buttons.

FILE 01 / CHLOROPLAST

The Envelope

Two membranes / a space inside

What makes this a compartment inside a cell?

A chloroplast in a typical plant cell is bounded by outer and inner envelope membranes. Inside the inner membrane lies the stroma, a fluid compartment containing enzymes, DNA, and the separate thylakoid membrane system. The translucent shell in this cutaway makes hidden structures visible; its open face is an artistic window, not a hole in a living chloroplast.

Compare a eukaryotic cell model OpenStax: Eukaryotic cells

FILE 02 / CHLOROPLAST

Thylakoid Stacks

Grana / connecting lamellae

Why are there stacks of green discs?

Thylakoids are flattened membrane sacs; stacks of them are called grana. Other thylakoid membranes connect regions of the system. Their membrane houses the light reactions, while each disc encloses a lumen. The evenly spaced glowing stacks here are schematic and enlarged, not a count or measured arrangement from a particular species.

Read the flower that abandoned sunlight OpenStax: Overview of photosynthesis

FILE 03 / CHLOROPLAST

Light and Water

Photosystem II / oxygen release

Where does the oxygen released by photosynthesis come from?

At photosystem II, light-driven chemistry extracts electrons from water, releasing oxygen and hydrogen ions. Electrons pass through a chain toward photosystem I and ultimately contribute to NADPH production. The amber glow marks a location on a thylakoid membrane. It does not track photons or electrons, and this simplified scene does not resolve the proteins or their sequence in space.

Explore the Sun, the light source OpenStax: Light-dependent reactions

FILE 04 / CHLOROPLAST

The Proton Gradient

Thylakoid lumen / ATP synthase

How does captured light help make ATP?

Light-driven electron transport contributes to a higher concentration of hydrogen ions inside the thylakoid lumen. Their return to the stroma through ATP synthase helps make ATP. The dots in one illustrated disc mark a compartment, not measured ion positions or movement. Chloroplast ATP supports photosynthetic reactions; the mitochondrion uses a different membrane gradient for cellular respiration.

Compare the mitochondrion’s gradient NCBI Bookshelf: Chloroplast electron transport

FILE 05 / CHLOROPLAST

Carbon in the Stroma

Calvin cycle / carbon fixation

Where does carbon dioxide enter the story?

In the stroma, the Calvin cycle uses ATP and NADPH from the light reactions to incorporate carbon dioxide into organic molecules. G3P is one product that can feed later carbohydrate synthesis. This scene marks the stroma as a location; it does not animate a real cycle, portray a complete sugar molecule emerging, or imply that every step happens inside a thylakoid.

Read the illustrated nonphotosynthetic flower article OpenStax: Carbon fixation

FILE 06 / CHLOROPLAST

An Older Partnership

Chloroplast DNA / cyanobacterial ancestry

Why does this organelle carry its own DNA?

Chloroplasts retain a genome and bacterial-like machinery because their lineage descends from an ancient cyanobacterial endosymbiont. Many chloroplast proteins are now encoded by the host cell nucleus. The tiny loop here symbolizes DNA without showing a real genome arrangement. Chloroplast origins and mitochondrial origins are distinct evolutionary episodes; the bacterial example in this Atlas is a modern cell, not the ancestor itself.

Compare a modern bacterium OpenStax: Eukaryotic origins

ABOUT THIS MODEL

This is a generalized plant chloroplast cutaway, not microscopy, an anatomical reconstruction of a species, or a simulation of photons, electrons, protons, or sugar synthesis. The two envelope membranes are partially transparent so the thylakoid system is visible. Stack number, disc size, connections, colors, DNA shape, and the glowing reaction markers are editorial simplifications. Proton dots mark a lumen compartment and do not show concentration or motion. Chloroplast types and thylakoid arrangements differ across photosynthetic lineages.

Sources: OpenStax on photosynthesis and chloroplast compartments, light reactions and ATP synthase, carbon fixation in the stroma, and chloroplast ancestry.

CHANGE SCALE / RELATED ATLAS VIEWS

Look at the question from another angle.

3D ATLAS / L-01From one chloroplast to a living forest

Move outward from the leaf’s energy machinery to an illustrated forest canopy. Open a light gap and follow a selected route of water through a tree.

Explore Rainforest: The Hidden Engine

SCIENTIFIC INQUIRY / APPLIED HERE

Explore all twelve principles

05 Correlation and causation

Follow energy and matter along separate routes.

The teaching view connects light capture, a proton gradient, and carbon fixation. Ask what experimental evidence links the steps and which material is transformed at each one. A moving dot is a visual guide, not a tracked molecule from a laboratory recording.

Ask yourself What evidence connects the proposed cause to the effect beyond their appearing together?