Answer:
Starch is a indicator in the iodometric titration and it turns deep dark blue when iodine is present in a solution. The starch under warming condition forms amylose and amyl pectin's which combine with iodine to produce dark blue color. In absence of iodide ion starch indicator is colorless.
Explanation:
Starch is a viable indicator in the titration process because it turns deep dark blue when iodine is present in a solution. When starch is heated in water, decomposition occurs and beta-amylose is produced. Beta-amylose combines with iodine, resulting in a dark blue color change. The iodine-starch test is a chemical reaction that is used to test for the presence of starch or for iodine. The combination of starch and iodine is intensely "blue-black". The interaction between starch and triiodide is the basis for iodometry. In an iodometric titration, a starch solution is used as an indicator since it can absorb the I2 that is released. This absorption will cause the solution to change its color from deep blue to light yellow when titrated with standardized thiosulfate solution. This indicates the end point of the titration. Aside from their basic nutritional uses, starches are used in brewing and as thickening agents in baked goods and confections. Starch is used in paper manufacturing to increase the strength of paper and is also used in the surface sizing of paper. When starch is heated in water, various decomposition products are formed, among which is beta-amylose which forms a deep blue-black complex with iodine. The starch indicator solution must be freshly prepared since it will decompose and its sensitivity is decreased.
Answer:
1. nerve stimulus
4. calcium channels open
10. acetylcholine vesicles move to endplate
7. exocytosis occurs releasing acetylcholine into synaptic cleft
3. acetylcholine binds to receptor
6. impulse rides along sarcolemma
9. impulse enters the cells via the t-tubule
5. sarcoplasmic reticulum releases calcium
8. calcium binds to troponin moving tropomyosin out of the way
2. myosin attaches to actin causing a twitch
Explanation:
The central nervous system generates an action potential (<u>1</u>) that travels to the muscle fiber activating the calcium channels (<u>4</u>). Calcium triggers vesicles fusion to the presynaptic membrane (<u>10)</u> releasing acetylcholine (Ach) into the synaptic space (<u>7</u>). Once there, Ach binds to its receptors (<u>3</u>) on the postsynaptic membrane of the skeletal muscle fiber, causing ion channels to open. Positively charged sodium ions cross the membrane to get into the muscle fiber (sarcoplasm) and potassium leaves the cell. The difference in charges caused by these ions transport charges positively the muscle fiber membrane (<u>6</u>). It depolarizes. The action potential enters the t-tubules (<u>9</u>) depolarizing the inner portion of the muscle fiber.
Contraction initiates when the action potential depolarizes the inner portion of the muscle fiber. Calcium channels activate in the T tubules membrane, releasing calcium into the sarcolemma (<u>5</u>). At this point, the muscle is at rest, and the tropomyosin is inhibiting the attraction strengths between myosin and actin filaments. <em>Tropomyosin is obstructing binding sites for myosin on the thin filament</em>. When calcium binds to troponin C, troponin T alters the tropomyosin position by moving it and unblocking the binding sites (<u>8)</u>. Myosin heads join to the uncovered actin-binding points forming cross-bridges <u>(2</u>), and while doing so, ATP turns into ADP and inorganic phosphate, which is released. Myofilaments slide impulsed by chemical energy collected in myosin heads, producing a power stroke. The power stroke initiates when the myosin cross-bridge binds to actin (<u>2</u>). As they slide, ADP molecules are released. A new ATP links to myosin heads and breaks the bindings to the actin filament. Then ATP splits into ADP and phosphate, and the energy produced is accumulated in the myosin heads, which starts a new binding cycle to actin. Finally, Z-bands are pulled toward each other, shortening the sarcomere and the I-band, producing muscle fiber contraction.
The currently most accepted hypothesis is the Nebular Hypothesis in which a gravitational collapse formed the solar system.
Answer:
inclusive fitness, parental investment, eugenics
Explanation:
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Answer:
Epidermis.
It is composed of keratinized, stratified squamous epithelium and is made up of 4 layers of epithelial cells depending on its location in the body. From deeper to superficial these layers are stratum Basale, stratum spinosum, stratum granulosum, and stratum corneum. The cells in all the layers except for stratum besele are called keratinocytes which is a cell that manufactures and stores the protein keratin.
Stratum Basale.
It is a cuboid-shaped stem cell that is a precursor of the keratinocytes of the epidermis. Two other cell types found in this basal cell are Merkel cells which function as a receptor and are responsible for stimulating sensory nerves that the brain perceives as touch. The second is melanocyte that produces melanin pigment which gives the skin its color.
Stratum spinosum.
It is spiny in appearance due to the protruding cell processes that join the cells via a structure called desmosome. The desmosome cell interlock with each other to strengthen the bond between the cell. Keratinocytes in the stratum spinosum stats synthesizing keratin and release water-repelling glycolipid that helps to prevent water losses from the body.
Stratum granulosum.
They are grainy in appearance due to further change in keratinocytes as they are pushes from the stratum spinosum. The cells become flat as their membrane thickens to allow the production of protein keratin which accolades as lamellar granules within the cells.
Stratum Lucidum.
It is a smooth and translucent layer of the epidermis situated above the stratum granulosum. Keratinocytes containing these cells are dead and flat. Stratum lucidum cells are packs with eleiden derived from keratohyalin which give these cells their transparency and provide a barrier to water.
Stratum corneum.
This is the most superficial layer in the epidermis and it prevents penetration of microbes and dehydration of underlying tissues.
Dermis.-This is the inner layer of the skin and has the following functions.
Reticular layer
Just below the papillary layer, we have a much thicker layer called the reticular layer composing of dense connective tissue. It contains elastin fibers providing elasticity to the skin enabling movement.
Hypodermis
Explanation:
