The cell membrane's main trait is its selective permeability, which means that it allows some substances to cross it easily, but not others. Small molecules that are nonpolar (have no charge) can cross the membrane easily through diffusion, but ions (charged molecules) and larger molecules typically cannot.
Charged Ions
An ion is a molecule that is charged because it has lost or gained an electron. The cell membrane is made of a bilayer of phospholipids, with an inner and outer layer of charged,hydrophilic "heads" and a middle layer of fatty acid chains, which are hydrophobic, or uncharged. Charged ions cannot permeate the cell membrane for the same reason that oil and water don't mix: uncharged molecules repel charged molecules. Even the smallest of ions -- hydrogen ions -- are unable to permeate through the fatty acids that make up the membrane. If ions "want" to enter the cell due to a high concentration of that type of ion on one side of the cell, they can do so by entering through the protein channels that are embedded between the lipids.
Large Polar Molecules
Large uncharged molecules, such as glucose, also cannot easily permeate the cell membrane. Although they do sometimes manage to slip across the membrane through diffusion, the process is extremely slow due to the size of the molecules. In order for these molecules to cross the membrane at a normal rate of speed, they need to resort to ion channels and specific transporters, which require energy output from the cell.
The terminal conducting elements in the ventricular myocardium are The Purkinje fibres.
The Purkinje fibers are specialised conducting fibres which are composed of electrically excitable cells and those fibers are located in the inner ventricular walls of the heart.e Purkinje fibres conduct cardiac action potentials and allow the heart to create synchronized contractions of its ventricles.
The choices for this question are:
<span>(1) Medial rotation of an extended knee
(2) Lateral rotation of an extended knee
(3) Forward sliding of the tibia on the femur
(4) Forward sliding of the femur
The correct answer is "forward sliding of the tibia on the femur". This is in all due respect to the anatomy of the anterior cruciate ligament wherein it is attached to (1) the anterior intercondylar notch of the femur and (2) anterior intercondylar eminence of the tibia. If this ligament if torn, the tibia will be pushed more anteriorly than normal in relation to the femur, leading to pain and difficulty ambulating.</span>
Wind erosion is a slow process.
Answer:
(d) The Tropic of Capricorn passes through India.
Explanation:
The tropic of cancer is the southernmost latitude that is parallel to the tropic of cancer (Tropic of Cancer- North / Tropic of Capricorn – South). It is the tropic that is the nearest to the Antarctica. The Tropic of Capricorn passes through: Namibia, Botswana, South Africa, Mozambique, Madagascar, Australia, Chile, Argentina, Paraguay, Brazil, the Atlantic Ocean, the Indian Ocean and the Pacific Ocean.
