Coenzyme Transporting Electrons to ETC

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Chemiosmotic phosphorylation

Chemiosmotic phosphorylation is the third pathway that produces ATP from inorganic phosphate and an ADP molecule. This process is part of oxidative phosphorylation.

The complete breakdown of glucose in the presence of oxygen is called cellular respiration. The last steps of this process occur in mitochondria. The reduced molecules NADH and FADH2 are generated by the Krebs cycle and glycolysis. These molecules pass electrons to an electron transport chain, which uses the energy released to create a proton gradient across the inner mitochondrial membrane. ATP synthase then uses the energy stored in this gradient to make ATP. This process is called oxidative phosphorylation because oxygen is the final electron acceptor and the energy released by reducing oxygen to water is used to phosphorylate ADP and generate ATP.

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Non-Cyclic Photophosphorylation

Non-cyclic photo- phosphorylation,cytochrome b6f uses the energy of electrons from PSII to pump protons from the stoma to the lumen. The proton gradient across the thylakoid membrane creates a proton-motive force, used by ATP synthase to form AT

 Non-cyclic photophosphorylation Process

• Non-cyclic photophosphorylation takes place inside a chloroplast, on or in a thylakoid membrane.
• A photon of light energy strikes the leaf and hits photosystem 2. The energy will pass from one antenna pigment molecule to another until it reaches a reaction center molecule (p680). The light energy will then energize 2 electrons.
• The energized electrons now pass to an electron acceptor this creates an electron "hole" within PS2.
• Water is split inside the thylakoid, providing the electrons to fill the "hole" for photosystem 2. The hydrogen ions, that for the moment are inside the thylakoid, and oxygen which will diffuse out of the chloroplast and the cell.
• From the electron acceptor the electrons pass to plastoquinone (PQ).
• From plastoquinone (PQ) the electrons pass on to a complex of cytochromes.
• As the electrons move from PQ to the cytochrome complex they release enough energy to power the active transport of hydrogen ions from the stroma into the thylakoid space. This generates a large hydrogen ion gradient.
• From the cytochrome complex the electrons pass on to Photosystem 1 to fill an electron "hole" in PS1.
• A photon of light energy strikes the leaf and hits photosystem 1. The energy will pass from one antenna pigment molecule to another until it reaches a reaction center molecule (p700). The light energy will then energize 2 electrons.
• The energized electrons now pass to an electron acceptor this creates the electron "hole" within PS1.
• From the electron acceptor the electrons pass to ferredoxin (Fd).
• From ferredoxin (Fd) the electrons and 2 hydrogen ions are used to reduce NADP+ to NADPH + H+. The NADPH + H+ is going to be utlized in the Calvin Cycle (dark reactions).
• The hydrogen ions that have been pumped into the thylakoid space pass down a concentration gradient through the ATP synthetase complexes. As the ions pass through the synthetase complex their chemiosmotic energy is released.
• The energy released by the hydrogen ions is used to help convert ADP and a phosphate group into ATP. Some of this ATP is going to be utlized in the Calvin Cycle (dark reactions).

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Constitutive Secretion

In constitutive secretion Proteins are continuously secreted from the cell regardless of environmental factors. No external signals are needed to initiate this process. Proteins are packaged in vesicles in the Golgi apparatus and are secreted via exocytosis, all around the cell. Cells that secrete constitutively have many Golgi apparatus scattered throughout the cytoplasm. Fibroblasts, osteoblasts and chondrocytes are some of the many cells that perform constitutive secretion.

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Opening the Mind’s Eye- Learning to See

About the Lecture

It’s rare to find research that simultaneously advances basic science and brings good into people’s lives, but Pawan Sinha’s Project Prakash does precisely that. An investigator of human visual processing, Sinha is interested in how these brain mechanisms develop. For his work, Sinha realized the ideal subjects would be individuals who developed sight after blindness. Since he could not ethically create such an experimental population, he had to “rely on natural experiments” -- children born blind, but who recovered their vision.

Sinha found these subjects in his native India, which has the world’s highest number of blind children -- more than one million. They are victims of Vitamin A deficiency, congenital cataracts, and absent or atrocious medical care. But salient to Sinha’s research, many of these blind children could be treated. He glimpsed a humanitarian and scientific opportunity, and Project Prakash (Sanskrit for light) was born.

Starting a few years ago, Sinha and his team began screening blind children in a few villages to identify cases of treatable blindness, and remedy their disorders. More recently, he’s gained support from hospitals and schools for the blind, reaching many more children. He began to establish a test population. Research on this unique group has yielded many original insights into the development of vision, and shaken some major scientific dogmas. Sinha found that after years without visual stimuli, the brains of these children could process new information flooding in -- challenging the notion of early critical periods in brain development. He discovered that patients who once learned about objects simply via touch could, once they gained sight, identify the same objects simply by looking at them.

Sinha has also delved into the mechanisms of visual integration -- how our brains make sense of visual cues containing diverse colors, illumination, and patterns. He’s learned that newly sighted patients have difficulty parsing overlapping images (such as triangles, squares, circles), but moving these images around magically sparks recognition. Research results are consistent across all ages, and show that early stages of sight acquisition involve seeing the world in a fragmented way, compromising recognition, and that motion cues are critical for putting pictures together meaningfully, serving “a critical bootstrapping function for visual learning.”

The kinds of integrative difficulties experienced by Project Prakesh children bring to mind similar difficulties in autistic children, for whom motion processing also seems to be deficient, and Sinha is now seeking a possible “causal chain in autism” that leads to the disorder’s devastating social impairments -- a research path that might someday yield new therapies.

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TamiFlu

Tamiflu (oseltamivir phosphate) is an antiviral drug marketed by the Swiss pharmaceutical company Roche. It belongs to a group of drugs called neuraminidase inhibitors and can shorten the duration and lessen the severity of the type A and B strains of the flu, as well as bird flu.

How neuraminidase inhibitors works

Tamiflu targets a protein called neuraminidase that lives on the flu virus cells. This protein helps the flu virus break through the cell walls so it can move on to other cells and replicate itself. Tamiflu inhibits the neuraminidase protein, so that the virus can't leave the cell to infect other cells. Eventually, the virus dies.

How Tamiflu kills the virus

Tamiflu can't stop the flu entirely. However, studies have shown that if you take it within 48 hours of showing symptoms, it can shorten the duration of the flu (strains A and B). Patients with the flu who took it felt better 30 percent (or 1.3 days) faster than people who didn't take it . The drug also can help protect you from getting the flu if you're exposed to someone who has it. But Tamiflu can't prevent the spread of the disease, and it won't stop illnesses (like the common cold) that resemble the flu.

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Regulated Secretion

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Disulfide Bonds

Disulfide bonds play an important role in the folding and stability of some proteins, usually proteins secreted to the extracellular medium. Since most cellular compartments are reducing environments, disulfide bonds are generally unstable in the cytosol with some exceptions as noted below.

Disulfide bonds in proteins are formed between the thiol groups of cysteine residues. The other sulfur-containing amino acid, methionine, cannot form disulfide bonds. A disulfide bond is typically denoted by hyphenating the abbreviations for cysteine, e.g., the "Cys26-Cys84 disulfide bond", or the "26-84 disulfide bond", or most simply as "C26-C84" where the disulfide bond is understood and does not need to be mentioned. The prototype of a protein disulfide bond is the two-amino-acid peptide, cystine, which is composed of two cysteine amino acids joined by a disulfide bond (shown in Figure 2 in its unionized form). The structure of a disulfide bond can be described by its χss dihedral angle between the Cβ − Sγ − Sγ − Cβ atoms, which is usually close to ±90°.

The disulfide bond stabilizes the folded form of a protein in several ways: 1) It holds two portions of the protein together, biasing the protein towards the folded topology. Stated differently, the disulfide bond destabilizes the unfolded form of the protein by lowering its entropy. 2) The disulfide bond may form the nucleus of a hydrophobic core of the folded protein, i.e., local hydrophobic residues may condense around the disulfide bond and onto each other through hydrophobic interactions. 3) Related to #1 and #2, the disulfide bond link two segments of the protein chain, the disulfide bond increases the effective local concentration of protein residues and lowers the effective local concentration of water molecules. Since water molecules attack amide-amide hydrogen bonds and break up secondary structure, a disulfide bond stabilizes secondary structure in its vicinity. For example, researchers have identified several pairs of peptides that are unstructured in isolation, but adopt stable secondary and tertiary structure upon forming a disulfide bond between them.

"Disulfide bond." Wikipedia, The Free Encyclopedia. 20 Jul 2009, 07:46 UTC. 20 Jul 2009 <http://en.wikipedia.org/w/index.php?title=Disulfide_bond&oldid=303092230>.

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