When two atoms react, they form either of two kinds of bond, ionic bonds or covalent bonds.
Ionic bonds are the type of bonds where there is transfer of electrons from one atom to another. The electrons are removed and from one atom and attached to another. A good example is salt which is composed of sodium and chlorine. Sodium readily loses one of its electrons and chlorine readily accepts it. Before losing the electron, sodium has a positive charge, but then becomes negatively charged after giving up the electron. Chlorine has a positive charge before gaining the electron but becomes negatively charged after gaining the electron. These opposite charges between sodium and chlorine attract the two elements together to form the ionic bond.
Covalent bonds are the kind of bonds formed when two atoms share electrons. Here there is sharing, none of the atoms loses an electron and none gains. A good example is water which is formed when oxygen shares two electrons, each with an atom of hydrogen.
The Oxygen atom forms two covalent bonds with the pair of hydrogen atoms.
<span>The answer is a. carbohydrates. The amount of potential energy in the molecule depends on the number of C-H bonds in the molecule. Carbohydrates have more C-H bonds. Thus, they can serve as energy storage. Other macromolecules have less C-H bonds. Thus, when energy is needed immediately, complex carbohydrates break down to simple carbohydrates and the energy is released.</span>
Answer:
the first trophic level shows a primary producer
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.
