chloroplast

Award-winning Game: Meta!Blast: The Leaf is a game that immerses the player in the action on and in a leaf. Intended as a supplement to in-class instruction for high school students, it lets users pilot a miniature bioship across a strange landscape, which features nematodes and a lumbering tardigrade.

Keep reading

ATP synthesis. The chemiosmotic hypothesis by Peter Mitchell had four postulates. Here, we explore them all.

Electrons lose some redox potential as they are transported through an ETC. Some of that energy can be reclaimed in establishing an electrochemical gradient. The Q cycle is one way - see my sheet on this for a fuller explanation - and conformational changes in proton pumps like in Complex I is another, although this is less well understood.

The membrane is fairly impermeable to protons. Using an proton ionophore uncouples the proton gradient from ATP synthesis. These act as uniports of protons back into the matrix/stroma. The example used here is 2,4-dinitrophenol (DNP), which is attracted to the positive face of the membrane when unprotonated and to the less negative face when protonated.

The proton gradient drives ATP synthase. Protons return to the matrix/stroma via c subunits in the F0 subunit of ATP synthase. This turns the γδε rotor relative to three dimeric αβ subunits, which are held still by a stator, in the F1 subunit. Rotation causes conformational changes in the αβ subunits, which cycles them through loose, tight, and open conformations, which makes ATP. ATP synthase working in reverse is an ATPase, and mammalian IF1 protein jams this function.

And finally, translocators feed ADP and Pi into the system.


ATP synthesis by Ayraethazide is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
youtube

cytoplasm streaming (movement of cytosol) carrying chloroplasts around the edges of the plant cells.

Chloroplast. Coloured scanning electron micrograph (SEM) of a section through a plant cell, showing a fractured chloroplast (dark green). Chloroplasts are the site of photosynthesis, the process that synthesises carbohydrates from carbon dioxide and water using sunlight. The pigment responsible for photosynthesis, chlorophyll, is found on stacks of parallel thylakoids (membranes, dark green) called grana.

Credit: DR DAVID FURNESS, KEELE UNIVERSITY/SCIENCE PHOTO LIBRARY

That natural glow By Fernán Federici and Jim Haseloff , University of Cambridge Perhaps the most famous of the plant organelles, the chloroplast is the site of photosynthesis, and as such, is the energy workhouse of the plant cell, similar to our mitochondria. The natural autofluorescence of chlorophyll allows researchers to use fluorescence analysis techniques to ask questions about the efficiency of photosynthesis. Image: 3D projection of a Z-stack of confocal images of fluorescent Arabidopsis thaliana leaf cells. A green fluorescent marker is used to mark cells in blue and autofluorescence from chloroplasts is shown in red.