Cell Growth Cell cycle and Mitosis Why are cells small? Surface area to volume ratio As a cell grows bigger, its internal volume enlarges and the cell membrane expands. The volume increases more rapidly than does the surface area this causes a problem. Cell size and material exchange The larger a cell grows the more trouble it has moving enough nutrients in Moving all the waste materials out DNA Overload Checkpoint!!!! What are two problems that cell growth causes for cells? The larger a cell becomes, the more demands the cell places on its _____ and the more trouble the cell has moving enough _________and _________ across the cell membrane. What is viable solution for cells solve these problems? Cell Division A larger cell splits into two smaller daughter cells. The Cell Cycle and Mitosis Make diagram cell of cycle page 245 of text The Cell Cycle - series of events that cells go through as they grow and divide The cell cycle is divided into two halfs Interphase - period of the cell cycle between cell divisions M phase period of time when mitosis and cell division occurs Parts of Interphase G 1 Phase Growing S Phase Chromosomes(DNA) are replicated G 2 Phase Organelles and molecules for cell division are produced (centrioles) Chromatin and Chromosomes Chromatin - A complex of DNA and proteins in the cell nucleus that condenses to form chromosomes during cell division. Chromosomes Condensed Chromatin They are the same stuff, just in different forms Chromatin condenses in chomosomes before mitosis begins Chromatin Chromosomes Different organisms have different #s of chromosomes Humans cells 46 Fruit Fly cells 8 Carrot cells 18 King Crab cells - 208 Chromosomes Replication During the cell cycle (before cell division can take place) chromosomes are replicated to form an identical copy of itself. Two identical copies of a chromosome are called sister chromatids (one of two identical sister parts of a duplicated chromosome) Centromere - area where the chromatids of a chromosome are attached M Phase, Cell Division and Mitosis Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis - Cytoplasmic division and other changes exclusive of nuclear division that are a part of mitosis or meiosis. In plant cells, a cell plate forms. The cell plate is synthesized by the fusion of multiple membrane- bounded vesicles. Their fusion supplies new plasma membrane for each of the two daughter cells. Synthesis of a new cell wall between the daughter cells then occurs at the cell plate.cell wall 10-3 cell cycle regulation Homework 10-3 guided reading workbook Checkpoint 1. The break down of a cells entire life is the _______ ________. 2. The phase of the cell cycle when the cell is growing, replicating DNA and getting ready for mitosis is _____________ What are the four phases of Mitosis? 7. The process of a cell actually splitting in two is called _______________. Controls on Cell Division How do cells know when to divide and when not to? Internal regulators are proteins that respond to events inside the cell. Some proteins make sure cells do not enter mitosis until all of the chromosomes have been replicated. What stage of the cell cycle do you think these proteins work? G 2 phase Cyclins (internal regulator) one of a family of closely related proteins that regulate the cell cycle in eukaryotic cells Cyclins Protein that periodically rises and falls in concentration in step with the eukaryotic cell cycle. Cyclins activate crucial protein kinases (called cyclin-dependent protein kinases, or CDK) and thereby help control the progression from one stage of the cell cycle to the next. Cascade of events!! Cyclins External Regulators External regulators - Proteins that respond to events outside the cell are called external regulators. External regulators direct cells to speed up or slow down the cell cycle. Growth factors are among the most important external regulators, which tell cells to speed up division. When is this important? Molecules found on the surfaces of neighboring cells often have an opposite effect, causing cells to slow down or stop their cell cycles. Uncontrolled Cell Growth Cancer cell Various forms of cancer have many causes Smoking Radiation Viral infections The common thread in all cancers is that control over the cell cycle has broken down. Over 50% of cancer cells have a defect in the p53 gene. Quiz on Thursday HO due wednesday p53 antioncogene p53 is a tumor suppressor gene found mutated in about half of human cancers. It encodes a gene regulatory protein that is activated by damaged DNA and is involved in blocking further progression of the cell cycle. Oncogenes SRC, proto-oncogene tyrosine-protein kinase