Mitochondria (video) | Structure of a cell | Khan Academy
explained the relationship between the two processes. He published a book " .. Secondary Biology. Outer layer. Inner layer. Stroma. Lamellum. Granum. Matrix. In this lesson, we'll explore the parts of the chloroplast, such as the thylakoids and stroma, that make a chloroplast the perfect place for conducting photosynthesis in plant cells. Plant Cells Contain Chloroplasts. Inside of each of these tiny plant cells are one to hundreds of. Components of a typical chloroplast. 1 Granum 2 Chloroplast envelope. Outer membrane Grana are connected by intergranal or stroma thylakoids, which join granum stacks together as a single .. "Vipp1 deletion mutant of Synechocystis: A connection between bacterial phage shock and thylakoid biogenesis?".
Proteins are inserted into the membrane via the SRP-dependent pathway 1the Tat-dependent pathway 2or spontaneously via their transmembrane domains not shown in figure. Lumenal proteins are exported across the thylakoid membrane into the lumen by either the Tat-dependent pathway 2 or the Sec-dependent pathway 3 and released by cleavage from the thylakoid targeting signal.
The different pathways utilize different signals and energy sources. The Sec secretory pathway requires ATP as energy source and consists of SecA, which binds to the imported protein and a Sec membrane complex to shuttle the protein across.
Proteins with a twin arginine motif in their thylakoid signal peptide are shuttled through the Tat twin arginine translocation pathway, which requires a membrane-bound Tat complex and the pH gradient as an energy source. Some other proteins are inserted into the membrane via the SRP signal recognition particle pathway.
Difference Between Grana and Stroma
The chloroplast SRP can interact with its target proteins either post-translationally or co-translationally, thus transporting imported proteins as well as those that are translated inside the chloroplast. Some transmembrane proteins may also spontaneously insert into the membrane from the stromal side without energy requirement.
These include light-driven water oxidation and oxygen evolutionthe pumping of protons across the thylakoid membranes coupled with the electron transport chain of the photosystems and cytochrome complex, and ATP synthesis by the ATP synthase utilizing the generated proton gradient. The water-splitting reaction occurs on the lumenal side of the thylakoid membrane and is driven by the light energy captured by the photosystems.
This oxidation of water conveniently produces the waste product O2 that is vital for cellular respiration. The molecular oxygen formed by the reaction is released into the atmosphere. Electron transport chains[ edit ] Two different variations of electron transport are used during photosynthesis: Cyclic electron transport or Cyclic photophosphorylation produces only ATP.
The noncyclic variety involves the participation of both photosystems, while the cyclic electron flow is dependent on only photosystem I. In cyclic mode, the energized electron is passed down a chain that ultimately returns it in its base state to the chlorophyll that energized it.
The carriers in the electron transport chain use some of the electron's energy to actively transport protons from the stroma to the lumen.
Thylakoid - Wikipedia
During photosynthesis, the lumen becomes acidicas low as pH 4, compared to pH 8 in the stroma. Source of proton gradient[ edit ] The protons in the lumen come from three primary sources. Photolysis by photosystem II oxidises water to oxygenprotons and electrons in the lumen. The transfer of electrons from photosystem II to plastoquinone during non-cyclic electron transport consumes two protons from the stroma.
These are released in the lumen when the reduced plastoquinol is oxidized by the cytochrome b6f protein complex on the lumen side of the thylakoid membrane. A-T-P factories and if you watched the videos on ATP or cellular respiration or other videos, I'd repeatedly talk about how ATP is really the currency for energy in the cell that when it's in its ATP form you have adenosine triphosphate.
If you pop one of the phosphate groups off, you pop one of the P's off, it release energy and that's what your body uses to do all sort of things from movement to thinking to all sorts of things that actually go on in your bodies, so you can imagine mitochondria are really important for energy, for when the cell has to do things.
And that's why you'll find more mitochondria in things like muscle cells, things that have to use a lot of energy. Now before I get into the structure of mitochondria, I wanna talk a little bit about its fascinating past because we think of cells as the most basic unit of life and that is true, that comes straight out of cell theory, but it turns out the most prevalent theory of how mitochondria got into our cells is that at one time the predecessors, the ancestors to our mitochondria, were free, independent organisms, microorganisms.
So they're descendent from bacterial-like microorganisms that might have been living on their own and they were maybe really good at processing energy or maybe they were even good at other things, but at some point in the evolutionary past, they got ingested by what the ancestors of our cells and instead of just being engulfed and being torn to shreds and kind of being digested and eaten, it was like, "Hey, wait, if these things stick around, "those cells are more likely to survive "because they're able to help process glucose "or help generate more energy out of things.
And I'll first draw kind of a simplified drawing of a mitochondion and I'll draw a cross section.
So, I'm gonna draw a cross section. So if we were to kind of cut it in half. So what I've drawn right over here this would be its outer membrane.
This is the outer membrane right over here and we label that. And all of these membranes that I'm gonna draw, they're all going to be phospholipid bilayers. So if I were to zoom in right over here, so let me, if I were to zoom in, we would see a bilayer of phospholipids. So you have your hydrophilic heads facing outwards, hydrophilic heads facing outwards and your hydrophobic tails facing inwards.
You see something just like that, so they're all phospholipid bilayers. But they aren't just phospholipids.
All of these membranes have all sorts of proteins imbedded, I mean cells are incredibly complex structures, but even organelles like mitochondria have a fascinating, I guess you would say sub-structure to them. They themselves have all sorts of interesting proteins, enzymes imbedded in their membranes and are able to help regulate what's going on inside and outside of these organelles. And one of the proteins that you have in the outer membrane of mitochondria, they're called porins and porins aren't found only in mitochondria, but they're kind of tunnel proteins, they're structured so they kind of form a hole in the outer membrane.
So I'm drawing them the best that I can. These are porins and what's interesting about porins is they don't allow large molecules to pass through passively, but small molecules like sugars or ions can pass passively through the porins. And so, because of that, your ion concentration and well, I should actually say, your small molecule concentrations tend to be similar on either side of this membrane, on either side of this outer membrane.
But that's not the only membrane involved in a mitochondrion. We also have a inner membrane.
What is the relationship between the granum and the stroma?
I'll do that in yellow. What is Stroma Stroma refers to a colorless jell-like matrix of the chloroplast in which the dark reaction of photosynthesis takes place.
Enzymes required for the dark reaction are embedded in the stroma. Stroma surrounds the grana.Thylakoid Meaning
In the stroma, carbon dioxide and water are used in the production of simple carbohydrates by using the light energy trapped by light reaction. Stroma and grana of a chloroplast are shown in figure 2. Structure of a Chloroplast Dark reaction of photosynthesis is also called the Calvin cycle. The three stages of the Calvin cycle are carbon fixation, reduction reactions, and RuBP regeneration.
Similarities Between Grana and Stroma Both grana and stroma are two structures of the chloroplast. Reactions of photosynthesis occur in both grana and stroma.
Grana refers to the stacks of thylakoids embedded in the stroma of a chloroplast. Grana are the disk-like plates in the stroma.