BIOL 1103 1st Edition Exam 3 Study Guide Reading Summaries Membranes The Cell s plasma membrane outlines the border of the cell and determines what materials it comes in contact with The plasma membrane is flexible and carries receptors Receptors are sites of attachment for specific particles that interact with the cell They are very specific The fluid mosaic model shows the structure and function of the plasma membrane o The components of the plasma membrane are carbohydrates cholesterol phospholipids and proteins o The first chemical component of the plasma membrane is a bilayer of phospholipids The hydrophilic water loving polar heads of the phospholipid is in contact with the fluid outside of the cell and the fluid inside cell The inside of the membrane between the two hydrophilic layers are the hydrophobic water fearing non polar tails of the phospholipids These do not come in contact with the inside or the outside of the cell o The second chemical component of the plasma membrane is protein They serve as pumps or channels to move materials out of or into the cell They may also serve as enzymes structural attachments or receptors o The third chemical component of the plasma membrane is carbohydrates They are always found on the outside surface of the cell They bind to proteins glycoproteins or lipids glycolipids They help receptors Passive Transport o The movement of molecules across the cell that does not require ATP energy o Hydrophilic polar have trouble passing through the lipid bilayer o Hydrophobic non polar do not have trouble passing through the lipid bilayer Simple diffusion o The movement of molecules from an area of high concentration to low concentration o The concentration gradient refers to the density of one chemical substance versus another o Diffusion depends on steepness of the concentration gradient temperature charge and diameter of molecule o Diffusion stops when there is equilibrium Facilitated diffusion o The passive transport of a molecule down its concentration gradient with the help of a transport protein o The protein undergoes a conformational change so that the molecule can pass through Osmosis o The passage of water across a membrane from an area of high concentration to an area of low concentration o Hypotonic solution with lesser concentration o Hypertonic solution with greater concentration o This continues until equilibrium has been reached o Even though water is polar it is small enough to pass through the membrane Active transport o The pumping of molecules against the concentration gradient with expenditure of ATP energy o This is required to obtain scares molecules around the cell Ion Pumps o Are special proteins which actively transport ions resulting in an ionic and voltage gradient o Proteins are channels used to pump the ions in or out of the cell Co transport o The coupled passage of two materials across a membrane o Hydrogen is pumped out of the cell moves down the concentration gradient and as it re enters the cell it brings another molecule like sucrose who is unable to enter by itself in with it Endocytosis o The import of materials to the cell by infoldings of the plasma membrane o Three types Phagocytosis cell eating engulfs food particles outside the cell by forming a vesicle Pinocytosis cell drinking fluid is engulfed by the cell membrane and breaks off Receptor mediated endocytosis coated pits in the cell membrane are lined with receptor proteins that bind with specific material Once the binding has occurred the cell membrane pinches off Structure of DNA DNA s building blocks are nucleotides that are made up of three parts o Deoxyriboes phosphate group and nitrogenous base o There are four types of nitrogenous bases Adenine A and Guanine G which are double ringed and Cytosine C and Thymine T which are single ringed o The phosphate groups bond covalently to form a long chain of monomers Watson and Crick thought that DNA is made up of two strands that are twisted to form a double helix The nitrogenous bases bond with each other in a specific pattern A and T and then G and C In eukaryotes DNA is packaged in chromosomes and the DNA helix forms nucleosomes Estrogen Estrogen is a hormone that influences development growth behavior reproductive cycles sex characteristics and other body systems more effect in females than in males It has been linked to higher risks of cancer It produces its effects by binding to receptors on the cell s plasma membrane signaling systems to preform actions Estrogen disrupters are things that mimic or block the normal function of estrogen How Genes are Regulated ALL cells contain the same DNA but all cells do NOT produce the same protein Gene expression is the process of turning on a gene to manufacture RNA and protein Cells turn on or turn off different genes in response to changes in their environment Each cell is specialized and the differences help each cell perform basic functions specific to its needs DNA is located in the nucleus of the cell where it remains In order to obtain the genetic code mRNA is transcribed and transported from the nucleus to the cytoplasm where ribosomes translate it into protein Microarrays Genomics is a way to study many genes at once by using a microarray Depending on the cell type certain genes can be turned on or off When a gene is turned on it will produce strands of mRNA This process leads to the gene being expressed Microarrays allow scientists to see the differences in gene expression between two different cell types Each spot on the microarray has many copies of individual DNA sequences for a single gene Cancer cells are ones where a gene has been mutated broken or altered When the gene stops working like it should cell growth can increase rapidly leading to a tumor The microarray has six steps 1 Collect tissue a sample of healthy cells and a sample of cancer cells 2 Isolate RNA separate the RNA from protein DNA and other components 3 Isolate the mRNA since there are different types of RNA so scientist separate them to have mRNA by itself 4 Make labeled DNA copy give the DNA color so the different types of DNA mRNA can be differentiated The healthy cells receive green florescent color and the cancer cells receive red florescent color 5 Apply DNA when the cDNA copy DNA is applied to the microarray the cDNA strands attach to the specific complimentary DNA strand on the microarray Red spots mean that the cancer cDNA hybridized to the spot green means that the