Chapter 2 1 Basic Cell Structure There are two types of cells Eukaryotic cells which contain a nucleus and complex organelles and Prokaryotic cells that lack a nucleus and organelles Examples for Prokaryotic cells are bacteria and archeabacteria There are over 260 cell types and they fall into four categories Epithelial form in sheets such as blood vessels Muscle contract together Nerve together create neurons Connective cells around bones muscles and nerves The cell membrane or cell plasma contains the organelles and surrounds the cell Inside there are compartments that separate different molecules in a cell these are important in cell functioning The cell membrane is made up of phospholipids which have a head and a tail The head is hydrophobic because it does not like water therefore it is protected by the tails The tails are hydrophilic because they love water The Nucleus contains DNA The nucleus surface is also known as the nuclear envelope that allows substances in and out Closest to the nucleus is the Endoplasmic Reticulum There is a rough ER which contains ribosomes and there is a smooth ER that does not have ribosomes but is responsible for lipid molecule production Ribosomes are protein factories The Mitochondria is the powerhouse of the cell that creates ATP or energy Mitochondria have folds in the membrane where ATP is held The Golgi Apparatus is used for waste disposal It holds waste and uses enzymes to break down the waste from the cell The Cytoskeleton anchors the cell frames the cell and is made of proteins Chapter 2 2 The Cell Cycle The cell cycle begins in stage 1 or the G1 phase In the G1 phase the cell prepares for DNA replication by producing proteins Next is the G0 phase where the cell has one of three choices The cell can either die remain specialized or proceed to division If the cell remains specialized that means the cell will either drop out of the cycle or stay the same and never continue on in the cycle depending on the cell type If the cell continues on it will go to phase 3 or the S phase then phase four which is the G2 phase All of these phases are a part of Interphase Phase 5 is Mitosis of the cell where cell division occurs Prophase Metaphase Anaphase and Telophase occur and finally Cytokinesis in which two cells are formed into one cell Chapter 2 3 Mitosis 1 Prophase condensed chromosomes make up the cell and the spindle assembles Centrioles appear in the cell and the nuclear envelope breaks down 2 Metaphase Chromosomes align and the mitotic spindles are attached by the centromere which is in the middle of the cell 3 Anaphase Centromeres part and chromatids separate 4 Telophase The spindle disassembles and the nuclear envelope re forms 5 Cytokinesis 2 nuclei begin to form and the cytoskeleton splits cells in half causing 2 identical copies Within the cell cycle there are many check points that the cell must go through in order to continue forming The first checkpoint is after the G1 phase where the cell is stopped and has the option of dying continuing on or staying the same and not moving discussed earlier in notes The next checkpoint is in the S phase where the DNA is checked for damage The cell cycle is inhibited until the DNA can be repaired if it is damaged The next checkpoint is in the G2 phase where again the cell has three options The Apoptosis checkpoint monitors all cell steps along the cycle The cell is monitored to see if it okay if not Apoptosis will happen Apoptosis is programmed cell death Cells will be killed at checkpoints if they are not being copied correctly Chapter 2 4 Apoptosis and Stem Cells Apoptosis is programmed cell death that is part of normal development Death receptors respond from signals to kill certain cells The death receptors on the cell bind to signal molecules and Caspases are activated within Phagocytes then attack and engulf the cell remains and the cell compartments are degraded