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Download Notes – Limits to Cell Growth and the Cell Cycle There are two main
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Notes – Limits to Cell Growth and the Cell Cycle There are two main reasons why cells divide instead of continue to grow: 1. The larger a cell becomes, the more demands the cell places on its _________. 2. The cell has more trouble moving enough _____________________ and ___________________ across the cell membrane. DNA “Overload” - Information that controls a cell’s function is stored in a molecule known as ___________. In eukaryotic cells, DNA is found in the _______________. When a cell is_____________, the information stored in DNA is able to meet all of the cell’s needs. If a cell was too _________ an “information crisis” would occur and the cell would not function properly. EXAMPLE: Small library in a big town. Exchanging Materials - Food, water, and nutrients enter a cell through its _______ __________________ ___________ products leave in the same way The relationship between a cell’s ______________ and its _________________ _______ is the key to understanding why cells must divide as they grow! Cell Division In eukaryotes, cell division occurs in ________ major stages: 1. The division of the cell nucleus is called _________. 2. The division of the cell cytoplasm is called ___________. I. Chromosomes Genetic information is passed from one _________________ to the next on chromosomes. Before cell division, each chromosome is ____________ or copied. Chromosomes are made up of ________molecules. Each chromosome consists of 2 identical _________ chromatids. Each pair is attached at an area called the ________________. When the cell divides, the chromatids ____________ and each new cell gets one chromatid. II.The Cell Cycle A series of events that cells go through as they _______ & __________. Interphase-period of ___________ that occurs between cell divisions. Key Concepts: During the cell cycle……. -a cell ________ -prepares for ______________ -divides to form ____ daughter cells III. Phases of the cell cycle: 1. 2. 3. 4. 5. G1 (first gap phase) S phase G2 (second gap phase) M phase G0 (resting phase) G1 Phase- the cell _________ in size and synthesizes new ________ and ________________. S Phase- chromosomes are _____________ and DNA synthesis takes place; the rest of the cell cycle is usually completed G2 Phase- organelles and molecules _________ for cell division are produced. The cell is ready to start ____ phase. Mitosis (occurs in 4 phases) 1. Prophase- It is the first and ____________ phase of mitosis. The _____________ separate and take up position on opposite sides of the nucleus. The __________ is forming and the paired chromosomes are visible. * the centrosome helps to organize the spindle which is a fanlike microtubule that helps separate the chromosomes. *Chromatin ___________ into chromosomes *Nuclear envelope _________ down. 2. Metaphase- The chromosomes line up across the _________ of the cell. Microtubules _________ the centromere of the each chromosome to the poles of the spindle. 3. Anaphase- The sister chromatids _________ into individual chromosomes and they continue to move until they have separated into _______ groups. 4. Telophase- Chromosomes gather at ___________ ends of the cell and lose their distinct shape. A new ________ envelope forms around each cluster of chromosomes. Cytokinesis The cytoplasm _________ in half and each daughter cell has an identical set of duplicate chromosomes. In plants, a structure known as the ______ ______ forms midway between the individual nuclei G0 Phase- the cell leaves the cell cycle and quits ___________. This may be a temporary _________ period or more permanent. Ex: _________ cells and heart ___________ cells no longer divide after reaching maturity.