Chloroplast | BioNinja
A chloroplast is a basic organelle that in a sense is one of the most important organelles to us, and we don't even have them! In this lesson, we. Explain the relationship between the structure of the chloroplast and its function -The chloroplast contains thylakoids which have chlorophyll embedded in the thylakoid inter-membrane in clusters that absorb Isn't this diagram mafiathegame.info%mafiathegame.info very clear and concise?. Chloroplasts are organelles present in plant cells and some eukaryotic organisms. Chloroplasts are the most important plastids found in plant cells. It is the structure in a green plant cell in which photosynthesis occurs. Chloroplast Diagram.
They are enclosed in a chloroplast envelope, which consists of a double membrane with outer and inner layers, between which is a gap called the intermembrane space.
Mitochondria and chloroplasts (article) | Khan Academy
A third, internal membrane, extensively folded and characterized by the presence of closed disks or thylakoidsis known as the thylakoid membrane. In most higher plants, the thylakoids are arranged in tight stacks called grana singular granum. Grana are connected by stromal lamellae, extensions that run from one granum, through the stroma, into a neighbouring granum. The thylakoid membrane envelops a central aqueous region known as the thylakoid lumen.
- Chloroplasts - Show Me the Green
- 826 Explain the relationship between the structure of the chloroplast and its function
The space between the inner membrane and the thylakoid membrane is filled with stromaa matrix containing dissolved enzymesstarch granules, and copies of the chloroplast genome. Chloroplasts circulate within plant cells. The green coloration comes from chlorophyll concentrated in the grana of chloroplasts.
The photosynthetic machinery The thylakoid membrane houses chlorophylls and different protein complexes, including photosystem I, photosystem II, and ATP adenosine triphosphate synthase, which are specialized for light-dependent photosynthesis.
When sunlight strikes the thylakoids, the light energy excites chlorophyll pigments, causing them to give up electrons. The electrons then enter the electron transport chain, a series of reactions that ultimately drives the phosphorylation of adenosine diphosphate ADP to the energy-rich storage compound ATP.
Electron transport also results in the production of the reducing agent nicotinamide adenine dinucleotide phosphate NADPH. ATP and NADPH are used in the light-independent reactions dark reactions of photosynthesis, in which carbon dioxide and water are assimilated into organic compounds.
Rubisco catalyzes the first step of carbon fixation in the Calvin cycle also called Calvin-Benson cyclethe primary pathway of carbon transport in plants.
Among so-called C4 plants, the initial carbon fixation step and the Calvin cycle are separated spatially—carbon fixation occurs via phosphoenolpyruvate PEP carboxylation in chloroplasts located in the mesophyll, while malate, the four-carbon product of that process, is transported to chloroplasts in bundle-sheath cells, where the Calvin cycle is carried out.
Between the outer and inner membrane is a thin intermembrane space about nanometers wide. The space within the inner membrane is called the stroma. While the inner membranes of mitochondria have many folds called cristae to absorb surface area, the inner membranes of chloroplasts are smooth.
Instead, chloroplasts have many small disc-shaped sacs called thylakoids within their stroma. In vascular plants and green algae, the thylakoids are stacked on top of one another, and a stack of thylakoids is called a granum plural: The thylakoids contain chlorophylls and carotenoids, and these pigments absorb light during the process of photosynthesis.
Mitochondria and chloroplasts
Light-absorbing pigments are grouped with other molecules such as proteins to form complexes known as photosystems. The two different kinds of photosystems are photosystems I and II, and they have roles in different parts of the light-dependent reactions. In the stroma, enzymes make complex organic molecules that are used to store energy, such as carbohydrates.
The stroma also contains its own DNA and ribosomes that are similar to those found in photosynthetic bacteria. For this reason, chloroplasts are thought to have evolved in eukaryotic cells from free-living bacteria, just as mitochondria did.
This diagram shows the parts of a chloroplast.
Chloroplast: Structure and Function
Evolution of Chloroplasts Chloroplasts are thought to have become a part of certain eukaryotic cells in much the same way as mitochondria were incorporated into all eukaryotic cells: This is called the endosymbiotic theory. The evidence that chloroplasts evolved from bacteria is very similar to the evidence that mitochondria evolved from bacteria. Chloroplasts have their own, separate DNA that is circular, like that of a bacterial cell, and inherited maternally only from the mother plant alga.
New chloroplasts are formed through binary fissionor splitting, which is how bacteria reproduce. These forms of evidence are also found in mitochondria. The one difference is that chloroplasts are believed to have evolved from cyanobacteria, while mitochondria evolved from aerobic bacteria.
Mitochondria cannot photosynthesize; the process of cellular respiration occurs there instead. The structure of chloroplasts is similar to that of cyanobacteria; both have double membranes, circular DNA, ribosomes, and thylakoids. Most chloroplasts are believed to have come from one common ancestor that engulfed a cyanobacteria between million years ago. Related Biology Terms Thylakoid — Flattened disks within the stroma of the chloroplast that contain chlorophyll and carotenoids, and perform photosynthesis.
Photosynthesis — The conversion of light energy into chemical energy in the form of organic molecules. Symbiotic relationship — A close biological interaction between two different species.