MAINTENANCE Of WORKSTATION ANO TOOLS: Replace all panels. on the system is you are instructed. Return all tools, equipment, and materials to their respective places. SUMMARY STATEMENT: Explain what the symptoms would be if the four-way valve were leaking across the various ports. What temperature difference should be expected between the indoor line and the permanent suction-line ports on the reversing valve during the cooling cycle? What temperature difference should he expected between the outdoor line and permanent suction-line ports on the reversing valve during the heating cycle? If the permanent suction line were 10 degree F warmer than the indoor coil line at the four-way valve while the system is operating in the cooling mode, where could the heat come from? Why should you place the thermometer sensor at least 4\" from the four-way valve when checking the refrigerant-line temperature? What cautions should be taken when soldering a new four way valve into the line? What force actually changes the four way valve over from one position to another? What would the symptoms be of a four-wav valve that is stuck in the exact midposition? What terminal on the thermostat typically energizes the four-way valve coil? Solution THE FOUR-WAY VALVE •Allows the heat pump to pump heat in two directions •Diverts the discharge gas to either heat or cool the conditioned space •Refrigerant is directed from the compressor to the indoor coil in the heating mode •Refrigerant is directed from the compressor to the outdoor unit in the cooling mode •Controlled by the space temperature thermostat •Pilot-operated valve •Four piping connections on the valve BAD COMPRESSOR SUCTION AND DISCHARGE VALVES If a bad suction valve is suspected (higher than expected suction pressure), connect your gauge manifold hoses to the connection port on each valve (suction and discharge). Ensure both the suction and discharge valves are open. Close the suction valve only, while the compressor is on. The compressor should pull down to a vacuum of at least 28 inHg within 2 minutes. If this does not happen, turn the compressor off for about 3 minutes. Then energize the compressor and wait for a vacuum of at least 28 inHg within 2 minutes. If the 28 inHg is not reached, the suction valve needs to be replaced. If a bad discharge valve is suspected (lower than expected discharge pressure), connect your gauge manifold hoses to the connection port on each valve (suction and discharge). Ensure both the suction and discharge valves are open. Close the suction valve only and start the compressor. Pump the compressor into as deep of a vacuum as possible. Shut off the compressor and watch for the pressure to rise (on the compound gauge closest to the suction connection port). If it rises, pump the compressor into a vacuum again, shut of the compressor, and watch for another rise in pressure. If after continually repeating this process, the compound gauge stops rising in pressure, the discharge va.

1. Membranes are important structural features of cells. Describe the role of membranes in the
synthesis of ATP in cellular respiration.
Solution
Answer:
Membranes play a crucial role in the synthesis of ATP in the mitochondria, the power house of
the cell. Mitochondria are composed of two separate membranes, an outer and an inner
membrane. The structure of the inner membrane is organized iton repeated folds known as
cristae, which greatly increase surface area and therefore increase efficiency of an event known
as electron transport.
The electron transport chain utilizes electrons from NADH and FADH2 molecules, which are
transported along a nine-step chemical reaction chain. The electron transport chain does not
make ATP directly, but uses the energy released during redox reactions taking place in the
mitochondrial membranes to transport H+ through the membrane.
ATP production occurs because of chemiosmosis, the pumping of H+ across the membrane
using the ATP synthase (a transport protein). This protein uses the power of H+ sandwiched
between the inner and outer membranes, as a result of the electron transport chain, of the
mitochondria to drive ATP synthesis. The mechanism of action of ATP synthase resembles a
spinning rotor that uses hydrogen to generate ATP.
Thus, it can be concluded that membranes play a major role in ATP synthesis in both the election
transport chain and chemiosmosis, two events that are absolutely critical for aerobic respiration
in cells.