Plant water potential

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Bohr SHift- In the cytoplasm of red blood cells there is an enzyme, carbonic anhydrase, that catalyzes the following reaction:   CO2 + H2O(2 arrow)H2CO3 carbonic acid The carbonic acid dissociates: H2CO3(2 arrow)H+HCO3. Hemoglobin readily combines with the hydrogen ions, forming haemoglobinic acid, HHb. In so doing, it releases the oxygen which it is carrying. Cardiac cycle-1 Atrial systole. Both atria contract. Pressure still forces Atrioventricular valves open. Blood flows from the atria into the ventricles. 2 Ventricular systole. Ventricles contract. Atrio ventricular valves pulled shut due to the pressure in the ventricles exceeding the atria. Semi lunar valves forced open. Blood rushes into the arteries. 3 Ventricular diastole. The whole heart muscle relaxes. Semilunar valve shuts. Blood from veins flow into the atria Pacemaker-Each cardiac cycle begins in the right atrium. There is a small patch of muscle tissue in the right atrium wall, called the sinoatrial node (SAN), which automatically contracts and relaxes all the time. As the muscle in the SAN contracts, it produces an electrical excitation wave makes the muscle in the atrial walls contract. The excitation wave sweeps onwards and reaches another patch of cells, called the atrioventricular node (AVN) who delays the impulse for a fraction of a second, before it travels down into the ventricles. The excitation wave moves swiftly down through the septum of the heart, along fibres known as Purkyne tissue. Once the excitation wave arrives at the base of the ventricles, the ventricles contract. The ventricles then relax. Then the muscle in the SAN contracts again, and the whole sequence runs through once more Water movemnt thru leaf-Water vapour diffuses from an air space through an open stoma, a pro cess called transpiration. It is carried away from the leaf surface by air movements. This reduces water potential inside the leaf. Water evaporates from a mesophyll cell wall into the air space. Water moves through the mesophyll cell wall or out of the mesophyll cytoplasm into the cell wall. Water leaves a xylem vessel through a non-lignified area such as a pit. It may enter the cytoplasm or cell wall of a mesophyll cell. Water moves up the xylem vessels to replace the water lost from the leaf Cohesion Adhesion-The movement of water up through xylem vessels is by mass flow. This means that all the water molecules (and any dissolved solutes) move together. This is helped by the fact that water molecules are attracted to each other by hydrogen bonding ,this attraction is called cohesion. They are also attracted to the cellulose and lignin in the walls of the xylem vessels, and this attraction is called adhesion. Cohesion and adhesion help to keep the water in a xylem vessel moving as a continuous column. Symplastic 1 Water enters the cell wall. 2 Water moves through the cell wall. 3 Water may move from cell wall to cell wall through the intercellular spaces. 4 Water may move directly from cell wall to cell wall .Apoplastic-1 Water enters the cytoplasm by osmosis through the partially permeable cell surface membrane. 2 Water moves into the sap in the vacuole, through the tonoplast by osmosis. 3 Water may move from cell to cell through the plasmodesmata. 4 Water may move from cell to cell through adjacent cell surface membranes and cell walls.



Blood pressure drops in arterioles from 120 to 85 as arteries branch outbut as it leaves and flows into a capillary, the pressure will have dropped to about 35 mm Hg.In capillary, blood pressure drops (35 to 10 mmHg) enough for slower flow with exchange of thing.

Blood Composition-5 dm3 blood = 5 kg, 2.5 x 1013 Red Blood Cells/ Erythrocytes, 6 x 1012 Platelets/Thrombocytes,5 x 1011 White Blood Cells/ Leukocytes

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