Ponitillism from Birth to Adul essays

Ponitillism from Birth to Adul essays Pointillism has truly been the beginning of a new error within time itself. Its creation came from an offshoot of Impressionism, and is usually classified as a form of Post-Impressionism. It is very similar to Divisionism, but where Divisionism is concerned with the color theory, Pointillism is focused more so on the specific style of the brushwork in which was used to apply the paint. While being A style of painting in which non-primary colors are generated, not by mixing of pigments in the palette nor by using pigments directly, but by the visual mixing of points from primary colors placed in close proximity to each other. (Wikipedia.org) While George Seurat was credited for the birth of Pointillism, he used a normal scientific approach to his paintings abstruse color theories recedes somewhat. Seurat seemed to accept being known as a technician of art, and in doing so he borrowed from science the signs of its authority, including regularity and clarity of pattern. In doing so Seurat began to paint with a technique in which dots of unmixed color are juxtaposed onto the canvas. In doing this the dots blended together and created tones from when you would look at it from a distance. This means that with the same set of primaries, pointillist generated a different range of colors... (Wikipedia.org) Seurat also found that certain color combinations produced certain feelings, bright, warm colors made the viewers happy. While dark, cool colors can cause feelings of depression. In The Slid Show, Seurat used colors to create a melancholy, detached mood. The painting is brownish monochrome made up of green, yellow, orange, a nd blue dots and simplified, stylized shapes. Those shapes that can be read as figures are flat, vertical, two dimensional silhouettes. Seurats simplified, minimal forms can be seen as setting the stage for much of the twentieth centurys abstract art. Because of this the individual o...

Thylakoid Definition and Function

Thylakoid Definition and Function A thylakoid is a sheet-like membrane-bound structure that is the site of the light-dependent photosynthesis reactions in chloroplasts and cyanobacteria. It is the site that contains the chlorophyll used to absorb light and use it for biochemical reactions. The word thylakoid is from the Green word thylakos, which means pouch or sac. With the -oid ending, thylakoid means pouch-like. Thylakoids may also be called lamellae, although this term may be used to refer to the portion of a thylakoid that connects  grana. Thylakoid Structure In chloroplasts, thylakoids are embedded in the stroma (interior portion of a chloroplast). The stroma contains ribosomes, enzymes, and chloroplast DNA. The thylakoid consists of the thylakoid membrane and the enclosed region called the thylakoid lumen. A stack of thylakoids forms a group of coin-like structures called a granum. A chloroplast contains several of these structures, collectively known as grana. Higher plants have specially organized thylakoids in which each chloroplast has 10–100 grana that are connected to each other by stroma thylakoids. The stroma thylakoids may be thought of as tunnels that connect the grana. The grana thylakoids and stroma thylakoids contain different proteins. Role of the Thylakoid in Photosynthesis Reactions performed in the thylakoid include water photolysis, the electron transport chain, and ATP synthesis. Photosynthetic pigments (e.g., chlorophyll) are embedded into the thylakoid membrane, making it the site of the light-dependent reactions in photosynthesis. The stacked coil shape of the grana gives the chloroplast a high surface area to volume ratio, aiding the efficiency of photosynthesis. The thylakoid lumen is used for photophosphorylation during photosynthesis. The light-dependent reactions in the membrane pump protons into the lumen, lowering its pH to 4. In contrast, the pH of the stroma is 8.   Water Photolysis The first step is water photolysis, which occurs on the lumen site of the thylakoid membrane. Energy from light is used to reduce or split water. This reaction produces electrons that are needed for the electron transport chains, protons that are pumped into the lumen to produce a proton gradient, and oxygen. Although oxygen is needed for cellular respiration, the gas produced by this reaction is returned to the atmosphere. Electron Transport Chain The electrons from photolysis go to the photosystems of the electron transport chains. The photosystems contain an antenna complex that uses chlorophyll and related pigments to collect light at various wavelengths. Photosystem I uses light to reduce NADP to produce NADPH and H. Photosystem II uses light to oxidize water to produce molecular oxygen (O2), electrons (e-), and protons (H). The electrons reduce NADP to NADPH in both systems. ATP Synthesis ATP is produced from both Photosystem I and Photosystem II. Thylakoids synthesize ATP using an  ATP synthase enzyme that is similar to mitochondrial ATPase. The enzyme is integrated into the thylakoid membrane. The CF1-portion of the synthase molecule extended into the stroma, where ATP supports the light-independent photosynthesis reactions. The lumen of the thylakoid contains proteins used for protein processing, photosynthesis, metabolism, redox reactions, and defense. The protein plastocyanin is an electron transport protein that transports electrons from the cytochrome proteins to Photosystem I. Cytochrome b6f complex is a portion of the electron transport chain that couples proton pumping into the thylakoid lumen with electron transfer. The cytochrome complex is located between Photosystem I and Photosystem II. Thylakoids in Algae and Cyanobacteria While thylakoids in plant cells form stacks of grana in plants, they may be unstacked in some types of algae. While algae and plants are eukaryotes, cyanobacteria are photosynthetic prokaryotes. They do not contain chloroplasts. Instead, the entire cell acts as a sort of thylakoid. The cyanobacterium has an outer cell wall, cell membrane, and thylakoid membrane. Inside this membrane is the bacterial DNA, cytoplasm, and carboxysomes. The thylakoid membrane has functional electron transfer chains that support photosynthesis and cellular respiration. Cyanobacteria thylakoid membranes dont form grana and stroma. Instead, the membrane forms parallel sheets near the cytoplasmic membrane, with enough space between each sheet for phycobilisomes, the light harvesting structures.