Relative Clauses of time

In many cases, cells must move materials from an area of lower concentration to an area of higher concentration, or “up” their concentration gradient. Such movement of materials is known as active transport. Unlike passive transport, active transport requires a cell to expend energy. CELL MEMBRANE PUMPS Ion channels and carrier proteins not only assist in passive trans- port but also help with some types of active transport. The car- rier proteins that serve in active transport are often called cell membrane “pumps” because they move substances from lower to higher concentrations. Carrier proteins involved in facilitated diffusion and those involved in active transport are very similar. In both, the molecule first binds to a specific kind of carrier protein on one side of the cell membrane. Once it is bound to the molecule, the protein changes shape, shielding the molecule from the hydrophobic interior of the phospholipid bilayer. The protein then transports the molecule through the membrane and releases it on the other side. However, cell membrane pumps require energy. Most often the energy needed for active transport is supplied directly or indirectly by ATP. Sodium-Potassium Pump One example of active transport in animal cells involves a carrier protein known as the sodium-potassium pump. As its name sug- gests, this protein transports Na ions and K ions up their con- centration gradients. To function normally, some animal cells must have a higher concentration of Na ions outside the cell and a higher concentration of K ions inside the cell. The sodium- potassium pump maintains these concentration differences. Follow the steps in Figure 5-6 on the next page to see how the sodium-potassium pump operates. First, three Na ions bind to the carrier protein on the cytosol side of the membrane, as shown in step . At the same time, the carrier protein removes a phosphate group from a molecule of ATP. As you can see in step , the phos- phate group from the ATP molecule binds to the carrier protein. Step shows how the removal of the phosphate group from ATP supplies the energy needed to change the shape of the carrier pro- tein. With its new shape, the protein carries the three Na ions through the membrane and then forces the Na ions outside the cell where the Na concentration must remain high. 3 2 1 SECTION 2 OBJECTIVES ● Distinguish between passive transport and active transport. ● Explain how the sodium-potassium pump operates. ● Compare endocytosis and exocytosis. VOCABULARY active transport sodium-potassium pump endocytosis vesicle pinocytosis phagocytosis phagocyte exocytosis www.scilinks.org Topic: Active Transport Keyword: HM60018 mb06se_homs02.qxd 5/18/07 11:02 AM Page 103 104 CHAPTER 5 K+ K+ K+ K+ K+ K+ INSIDE OF CELL OUTSIDE OF CELL Carrier protein Cell membrane P P P P Na+ Na+ Na+ ATP ADP Na+ Na+ Na+ Na+ Na+ Na+ 1 2 3 4 5 6 At this point, the carrier protein has the shape it needs to bind two K ions outside the cell, as step shows. When the K ions bind, the phosphate group is released, as indicated in step , and the carrier protein restores its original shape. As shown in step this time, the change in shape causes the carrier protein to release the two K ions inside the cell. At this point the carrier protein is ready to begin the process again. Thus, a complete cycle of the sodium-potassium pump transports three Na ions out of the cell and two K ions into the cell. At top speed, the sodium-potassium pump can transport about 450 Na ions and 300 K ions per second. The exchange of three Na ions for two K ions creates an electrical gradient across the cell membrane. That is, the outside of the membrane becomes positively charged relative to the inside of the membrane, which becomes relatively negative. In this way, the two sides of the cell membrane are like the positive and nega- tive terminals of a battery. This difference in charge is important for the conduction of electrical impulses along nerve cells. The sodium-potassium pump is only one example of a cell membrane pump. Other pumps work in similar ways to transport important metabolic materials across cell membranes.

Relative clauses & use of accusative or dative after a preposition

Modals of deduction and relative clauses

Extradition (International law), Political Offence Exception, The Political Offense Exception (POE) serves as a critical safeguard in international extradition law, allowing a requested state to refuse the surrender of a fugitive if their alleged crime is of a "political character." These offenses are categorized into two types: **pure political offenses**, such as treason or espionage, which target the state's political organization without harming individuals; and **relative political offenses**, which are common crimes like robbery committed with a political motive. To distinguish between these, courts apply various judicial tests. For instance, the **Political Incidence Test** (established in *In re Castioni*) focuses on whether the act was incidental to a political disturbance, while the **Swiss Proportionality Test** weighs the political end against the criminal means used, denying the exception if the harm caused is disproportionate. In the context of **state succession**, the application of extradition treaties depends largely on the underlying legal theory adopted by the new sovereign. Under **Universal Succession**, the new state inherits all prior treaties and obligations, ensuring legal continuity. Conversely, the **Clean Slate (Tabula Rasa) Theory**, often seen in decolonization, suggests that new states are not bound by the predecessor’s treaties, potentially creating "safe havens" for fugitives until new agreements are reached. Practical examples include the **Dissolution of the USSR**, where Russia acted as the "continuator" state inheriting treaties, and the **Partition of India and Pakistan**, where a devolution agreement ensured that colonial-era treaties remained in effect. Despite its protective intent, the POE faces **modern erosion** to ensure that heinous acts do not go unpunished. Specific limitations, such as the **Attentat Clause**, explicitly exclude the assassination of a head of state from being considered a political offense. Similarly, modern treaties and conventions (like the *Meunier* ruling) exclude **terrorism**, hijacking, and crimes against humanity from the exception, viewing these acts as attacks on the general social order rather than legitimate political dissent. This evolution reflects a growing international consensus that the gravity of certain crimes—such as those seen in the **Rainbow Warrior case study**—far outweighs any claimed political motivation, shifting the legal focus toward human rights and the prevention of torture.

Relative Clauses

110.31.b.17.C

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