University:
High School
Course:
High School Biology
Academic year:

2023
Views:

500

Pages:

2
Author:

Hayley D.

Similarly most of the cells that make up our tissues and organs must be constantly replaced and renewed. These cells are called somatic cells For example, the cells that make up the lining of the small intestine are completely renewed every 2-4 days The cell cycle is an ordered sequence of events that occur in a cell as it prepares for cell division and duplication There are 2 main stages in the cell cycle. These are interphase and the mitosis phase. The cell spends the majority of its time in interphase. Interphase can be further divided into 3 subphases. The first growth phase is called the G1 phase. During this time, the cell carries out its functional role. Once a cell has replicated it organelles, it needs to replicate its DNA. This is the second growth phase (G2) The cell synthesises the necessary proteins, and replicates, more organelles in preparation for the mitosis phase. The mitosis phase results in the division of the cell. At the end of the phase, the cell has divided to form two new cells, and the cell cycle will start again. The duration of the cell cycle varies with different types of cells. For example, the cells lining the small intestine have a lifespan of 2-4 days, whereas red blood cells renew every 3-4 months. Cells are reliant on molecules going in and going out, in order to conduct their cellular processes. For example, to carry out cellular respiration, cells require glucose and oxygen to enter the cell and carbon dioxide and water to leave the cells In order to conduct these processes, the cells rely on diffusion and active transport across the cell membrane. The ideal conditions for high efficiency of these processes such as diffusion, active transport and osmosis is for each cell to have a large surface area and a small volume. This is called the surface area to volume ratio (SA:V). A cell is a its optimal efficiency at hight surface area and low volume. During interphase, the cell is increasing its internal organelle content. This means that there will be more organelles such as mitochondria, ribosomes and Golgi bodies To accommodate all this, the cell will also grow in volume through the cell cycle This make the cell less efficient as the SA;V ratio decreases. The decreasing surface area to volume ratio signals to the cell that ir must replicate its DNA and prepare for cell division. By dividing, it will be able to split this large cells into 2 smaller cells which are more efficient at carrying out their cellular processes. A replicated chromosome contains 2 identical sister chromatids. These gets split during mitosis, and each resulting contains 1 copy of each unreplicated chromosome.