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What organelle is responsible for packaging proteins?
The high oxygen levels may have turned pyrite on the continents into acid, which increased erosion, flooded essential nutrients, particularly phosphorus, into the oceans, and would have facilitated a huge bloom in the oceans. But this also happened in the midst of Earth's first ice age, so increased glacial erosion may have been primarily responsible, as we will see with a . The two largest carbon-isotope excursions () in Earth's history are related to ice ages. The first was a positive excursion (more carbon-13 than expected), and the second was negative. Scientists are still trying to determine what caused them. Beginning a little less than 2.3 bya and lasting for more than 200 million years is the Lomagundi excursion, in which there was great carbon burial. When the Lomagundi excursion finished, oxygen levels seem to have crashed back down to almost nothing and may have stayed that way for 200 million years, before rebounding to a few percent, at most, of Earth's atmosphere, and it stayed around that low level for more than a billion years.
Two important structures which are not considered organelles are the ribosomes and the cytoskeleton. Both of these are found in plant and animal cells. Ribosomes are responsible for the production of polypeptides which eventually become proteins. The cytoskeleton is important for maintaining the overall shape and organization of the cell and facilitates the movement of the cell’s internal structures from one place to another.
photosynthesis Study Sets and Flashcards | Quizlet
Although photosynthesis is performed differently by different species, the process always begins when energy from light is absorbed by proteins called reaction centres that contain green chlorophyll pigments. In plants, these proteins are held inside organelles called chloroplasts, which are most abundant in leaf cells, while in bacteria they are embedded in the plasma membrane. In these light-dependent reactions, some energy is used to stripelectrons from suitable substances such as water, producing oxygen gas.
In plants and algae, photosynthesis takes place in organelles called chloroplasts. A typical plant cell contains about 10 to 100 chloroplasts. The chloroplast is enclosed by a membrane. This membrane is composed of a phospholipid inner membrane, a phospholipid outer membrane, and an intermembrane space between them. Within the membrane is an aqueous fluid called the stroma. The stroma contains stacks (grana) of thylakoids, which are the site of photosynthesis. The thylakoids are flattened disks, bounded by a membrane with a lumen or thylakoid space within it. The site of photosynthesis is the thylakoid membrane, which contains integral and peripheral membrane protein complexes, including the pigments that absorb light energy, which form the photosystems.
Organelle Structure and Function
used the energy of captured photons to strip electrons from various chemicals. Hydrogen sulfide was an early electron donor. In the early days of photosynthetic life, there was no atmospheric oxygen. Oxygen, as reactive as it is, was deadly to those early bacteria and archaea, damaging their molecules through oxidization. , or the stripping of electrons from life’s molecules, has been a problem since the early days of life on Earth. Oxidative stress is partly responsible for how organisms age, but it can also be beneficial, as organisms use oxidative stress in various ways.
Some bacteria use Photosystem I and some use Photosystem II. More than two bya, and maybe more than three bya, cyanobacteria used both, and a miraculous instance of innovation tied them together. were then used to strip electrons from water. Although the issue is still controversial regarding when it happened and how, that instance of cyanobacteria's using manganese to strip electrons from water is responsible for oxygenic photosynthesis. It seems that some enzymes that use manganese may have been "drafted" into forming the manganese cluster responsible for splitting water in oxygenic photosynthesis. Water is not an easy molecule to strip an electron from, a single cyanobacterium seems to have “stumbled” into it, and it probably happened only . Once an electron was stripped away from water in Photosystem I, then stripping away a proton (a hydrogen nucleus) essentially removed one hydrogen atom from the water molecule. That proton was then used to drive a “turbine” that manufactures ATP, and wonderful show how those protons drive that enzyme turbine (). Oxygen is a waste product of that innovative ATP factory.
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chloroplast | Function, Location, & Diagram | …
Other than humans, rhesus macaques are Earth’s most widespread primates, and both species are generalists whose ability to adapt has been responsible for their success. Rhesus macaques are , about twice that of dogs and cats, and nearly as much as chimpanzees. Rhesus macaques have what is called Machiavellian social organization, in which everybody is continually vying for rank and power is everything. Those with rhesus power get the most and best food, the best and safest sleeping places, mating privileges, the nicest environments to live in, and endless grooming by subordinates, whom the dominants can beat and harass whenever they want, while those low in the hierarchies get the scraps and are usually the first to succumb to the vagaries of rhesus life, including predation. It is the . But even the lowliest macaque will become patriotic cannon fodder if his society faces an external threat, as even a macaque knows that a miserable life is better than no life at all. The violence inflicted seems economically optimized; within a society the violence is mostly harassment, but when rival societies first come in contact, the violence is often lethal, as the initially established dominance can last for lifetimes. Within a society, killing a subordinate does not make economic sense, as that subordinate supports the hierarchy. Potentates rely on slaves. The human smile evolved from the teeth-baring display of monkeys that connotes fear or submission.
Cell Organelles - Biology Facts
Anthropologists and primate researchers , but relatively recent scientific findings have disproven that notion. , and it is more sophisticated with great apes. It took a few million years after the human/chimp split for our ancestors to learn to , and that culture then spread widely in Africa. The , , and were probably all closely related and at least partly interdependent, but little seemed to change . Then the and possessed a larger brain, and new tools and behaviors are evident . The timeframes continually shrank between major events in the human journey. Only 200 thousand years later, and , and new behaviors are in evidence. Only 100 thousand years after that, anatomically modern humans appeared. Only 30 thousand years after that, about 170 kya, , probably due to necessity, where life once again was eked out on the margins, and those humans may have decorated their bodies. About 100 kya, innovation seems to have accelerated again, and by 75-60 kya there is evidence of . Needles and perhaps even arrowheads first appeared about 60 kya. There is no doubt among scientists that members of made those advances, and their artifacts provided evidence of increasing cultural and technical sophistication, which soon left Neanderthals and all other land animals far behind. About 75-70 kya, a , and there is controversy today whether that eruption was partly responsible for the that passed through not long afterward. What became today’s humanity seems to have nearly gone extinct at that bottleneck.
Plant Energy Transformations-Photosynthesis - …
The Iberian Peninsula had been the site of wars for several centuries by the , and the Christian/Islamic animosity there was pronounced; enslaving captured opponents was standard practice. Portugal began the maritime innovations that would see them seize the spice trade from their Islamic rivals. is closely associated with the rise of Portuguese maritime knowledge and practice. How responsible Henry was for Portugal’s maritime prowess has long been debated, but what is not debatable is that Portugal began developing the necessary knowledge and skills for accomplishing an unprecedented feat: sailing the world’s oceans. Until that time, only the Indian Ocean was regularly traveled because of its relatively gentle and predictable nature. Not until Europe’s rise were the Pacific, Atlantic, Arctic, and Antarctic oceans regularly traveled. sailors , unsuccessfully, and even settled some Atlantic islands, but Portugal was humanity’s first successful practitioner of transoceanic navigation. Many , and sailed down the Atlantic Coast of Africa and across the Atlantic. The Portuguese began , , and in 1434, Portugal became the first European power to on the African coast.
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