Presentation on theme: "Cellular Reproduction. Cellular Growth Cells grow until they reach their size limit, then they either stop growing or divide. A cells size is limited."— Presentation transcript:
Cellular Growth Cells grow until they reach their size limit, then they either stop growing or divide. A cells size is limited by the surface area-to-volume ratio
As cell size INCREASES, its volume INCREASES much faster than its surface area Two Formulas -Surface Area (SA) & Volume (V) SA = length+ width+ # of sides V = length x width x height Cellular Growth
The cell might have difficulty supplying nutrients and expelling enough waste products if its surface area is too small compared to its volume. surface volume The need for a surface sufficiently large to accommodate the volume explains the microscopic size of most cells. Importance of Surface Area
Substances move by diffusion or by motor proteins. Diffusion over large distances is slow and inefficient. Small cells maintain more efficient transport systems. Cell size affects the ability of the cell to communicate instructions for cellular functions. Importance of Surface Area
Cells must reproduce themselves at some point in their life. They do this by dividing in half to produce two new cells. Our entire body is made of cells-these are called body cells (somatic cells) Cellular Growth
Cell division prevents the cell from becoming too large. It is also the way the cell reproduces so that you grow and heal certain injuries. Cells reproduce by a cycle of growing and dividing called the cell cycle. The Cell Cycle
Cellular Organization of Genetic Material Chromatin- Found in nucleus of cell Made up of DNA & proteins Between cell divisions the chromatin strands are loosely coiled in the nucleus
Cellular Organization of Genetic Material Chromatin strands become tightly coiled during cell division and are then called chromosomes The DNA in cells wraps tightly around proteins to maintain shape of a chromosome
Chromosomes The number of chromosomes in different species may be the same or significantly different How many chromosomes are there in humans? In a plant? In a carrot?In a dog? ,262
Interphase is the stage during which the cell grows, carries out cellular functions, and replicates. Mitosis is the stage of the cell cycle during which the cells nucleus and nuclear material divide. Cytokinesis is the method by which a cells cytoplasm divides, creating a new cell. The Cell Cycle
The first stage of interphase, G 1 The cell is growing, carrying out normal cell functions, and preparing to replicate DNA. Cells are performing their assigned tasks, metabolizing, synthesizing, etc. The Stages of Interphase
The second stage of interphase, S The cell copies its DNA in preparation for cell division. (DNA synthesizes) DNA goes from 2 arms to 4 arms The Stages of Interphase
The third stage of interphase, G 2 2 nd growth stage The cell prepares for the division of its nucleus. The Stages of Interphase
Mitosis Body cell reproduction A cell divides into 2 new daughter cells and the cell cycle starts over Four Stages of Mitosis = PMAT Mitosis and Cytokinesis
Prophase Chromatin shortens and coils into chromosomes Nuclear membrane breaks down Centrioles appear & begin to move to opposite ends Spindle fibers form Stages of Mitosis
Metaphase Sister chromatids attach to spindle fibers Chromatids pulled to the middle of the cell
Stages of Mitosis Anaphase The microtubules of the spindle apparatus begin to shorten. Chromatids of each chromosome separate at centromere Chromatids move toward opposite poles of cell, centromere first
Stages of Mitosis Telophase Once chromosomes reach the poles, spindle fibers disassemble Chromosomes return to chromatin Two new nuclear membranes begin to form and the nucleoli reappear.
Cytokinesis- process where cytoplasm of cell begins dividing, this occurs during telophase stage Cell membrane moves inward to create TWO daughter cells- each with its own nucleus and identical chromosomes In humans each cell would have 46 chromosomes (diploid amount) Cytokinesis
Cleavage furrow- area of cell membrane that pinches in and divides animal cell Cell plate- midline of dividing plant cell, eventually forms into a cell wall Cytokinesis
Cell Cycle Regulation Normal Cell Cycle Proteins called cyclins bind to enzymes called cyclin- dependent kinases(CDK) in stages of interphase and mitosis to start various activities in the cell cycle. Quality Control Checkpoints The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong.
S G1G1 M checkpoint G2G2 M Control system G 1 checkpoint G 2 checkpoint Signals DNA replication Drives protein synthesis Starts mitosis Signals preparation for cell cycle
Cell Cycle Regulation Abnormal Cell Cycle: Cancer Cancer is the uncontrolled growth and division of cells. Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function.
Cell Cycle Regulation Causes of Cancer The changes that occur in the regulation of cell growth and division of cancer cells are due to mutations. Various environmental factors can affect the occurrence of cancer cells. Substances and agents known to cause cancer are called carcinogens.
Cell Cycle Regulation Apoptosis Programmed cell death Cells going through apoptosis actually shrink and shrivel in a controlled process Apoptosis can help to protect organisms from developing cancerous growths.
Cell Cycle Regulation Stem Cells Unspecialized cells that can develop into specialized cells when under the right conditions
Cell Cycle Regulation Embryonic Stem Cells An embryo is an organisms early prebirth stage of development After fertilization, the resulting mass of cells divides repeatedly until there are about 100–150 cells. These cells have not become specialized. If separated, cells can develop into specialized cells. If left alone, embryo will continue to develop.
Cell Cycle Regulation Adult Stem Cells Found in various tissues in the body and might be used to maintain and repair the same kind of tissue Less controversial because the adult stem cells can be obtained with the consent of their donor
Importance of Stem Cells Stem cells are not locked into being one type of cell, they might be the key to curing medical conditions and genetic defects if they can be developed into specific cells that are needed.