<em>G1, S and G2 phases are all cumulatively referred to as interphase involving the growth of a cell and the replication of its DNA. Initially in G1 phase, the cell grows physically and increases the volume of both protein and organelles. In S phase, the cell copies its DNA to produce two sister chromatids and replicates its nucleosomes. Finally, G2 phase involves further cell growth and organisation of cellular contents. The S phase of a cell cycle occurs during interphase, before mitosis or meiosis, and is responsible for the synthesis or replication of DNA. In this way, the genetic material of a cell is doubled before it enters mitosis or meiosis, allowing there to be enough DNA to be split into daughter cells. The S phase only begins when the cell has passed the G1 checkpoint and has grown enough to contain double the DNA. S phase is halted by a protein called p16 until this happens.</em>
<span>As blood moves away from the heart toward the tissues, the relative size of blood vessels decreases, the blood pressure drops, and the velocity of blood flow slows.
The size of the arteries progressively decreases as they branch out from the major arteries of the body. Once the arteries are the size of the arterioles, the resistance to blood flow increases and velocity of blood flow slows then blood pressure drops.
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The gas state. When water boils, it releases a gas we know as steam.
The primary energy system to fuel cycling for 15 minutes is THE AEROBIC GLYCOLYSIS SYSTEM.
There are different energy systems for fueling different types of physical exercise, the type of system that is used depend on the duration of the physical exercise. The energy system that exist are anaerobic glycolysis, aerobic glycolysis, phosphagem system and fatty acid oxidation. The aerobic glycolysis energy system relies on the complete breakdown of glucose. The pyruvate which is the end product of glucose oxidation is further broken down to acetyl coA, which then enters into the citric acid cycle. The aerobic glycolysis energy system is used for physical exercises that last between three to twenty minutes.
