2Cellular GrowthCells 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
3Cellular Growth SA = length+ width+ # of sides As cell size INCREASES, its volumeINCREASES much faster than its surface areaTwo Formulas-Surface Area (SA) & Volume (V)SA = length+ width+ # of sidesV = length x width x height
5Importance of Surface Area The cell might have difficulty supplying nutrients and expelling enough waste products if its surface area is too small compared to its volume.The need for a surface sufficiently large to accommodate the volume explains the microscopic size of most cells.
6Importance 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.
7Cellular GrowthCells 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)
8The Cell CycleCell 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.
9Cellular Organization of Genetic Material Chromatin-Found in nucleus of cellMade up of DNA & proteinsBetween cell divisions the chromatin strands are loosely coiled in the nucleus
10Cellular Organization of Genetic Material Chromatin strands become tightly coiled during cell division and are then called chromosomesThe DNA in cells wraps tightly around proteins to maintain shape of a chromosome
11How many chromosomes are there in humans? The number of chromosomes in different species may be the same or significantly differentHow many chromosomes are there in humans?In a carrot?In a dog?18In a plant?78461,262
12The Cell CycleInterphase 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 cell’s nucleus and nuclear material divide.Cytokinesis is the method by which a cell’s cytoplasm divides, creating a new cell.
13The Stages of Interphase The first stage of interphase, G1The cell is growing, carrying out normal cell functions, and preparing to replicate DNA.Cells are performing their assigned tasks, metabolizing, synthesizing, etc.
14The Stages of Interphase The second stage of interphase, SThe cell copies its DNA in preparation for cell division. (DNA synthesizes)DNA goes from 2 arms to 4 arms
15The Stages of Interphase The third stage of interphase, G22nd growth stageThe cell prepares for the division of its nucleus.
17Mitosis and Cytokinesis Body cell reproductionA cell divides into 2 new “daughter” cells and the cell cycle starts overFour Stages of Mitosis = PMAT
18Stages of Mitosis Prophase Chromatin shortens and coils into chromosomesNuclear membrane breaks downCentrioles appear & begin to move to opposite endsSpindle fibers form
19Stages of Mitosis Metaphase Sister chromatids attach to spindle fibers Chromatids pulled to the middle of the cell
20Stages of Mitosis Anaphase The microtubules of the spindle apparatus begin to shorten.Chromatids of each chromosome separate at centromereChromatids move toward opposite poles of cell, centromere first
21Stages of Mitosis Telophase Once chromosomes reach the poles, spindle fibers disassembleChromosomes return to chromatinTwo new nuclear membranes begin to form and the nucleoli reappear.
23CytokinesisCytokinesis- process where cytoplasm of cell begins dividing, this occurs during telophase stageCell membrane moves inward to create TWO daughter cells- each with its own nucleus and identical chromosomesIn humans each cell would have 46 chromosomes (diploid amount)
24CytokinesisCleavage 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
26Cell Cycle Regulation Normal Cell Cycle Quality Control Checkpoints 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 CheckpointsThe cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong.
27Control system S G1 G2 M G1 checkpoint Signals DNA replication Signals M checkpointG2MControlsystemG1 checkpointG2 checkpointSignals DNA replicationSignalspreparation forcell cycleFigure Mechanical analogy for the cell cycle control systemDrives protein synthesisStarts mitosis
28Cell 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.
31Cell 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.
32Cell Cycle Regulation Apoptosis Programmed cell death Cells going through apoptosis actually shrink and shrivel in a controlled processApoptosis can help to protect organisms from developing cancerous growths.
33Cell Cycle Regulation Stem Cells Unspecialized cells that can develop into specialized cells when under the right conditions
34Cell Cycle Regulation Embryonic Stem Cells An embryo is an organism’s early prebirth stage of developmentAfter 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.
35Cell Cycle Regulation Adult Stem Cells Found in various tissues in the body and might be used to maintain and repair the same kind of tissueLess controversial because the adult stem cells can be obtained with the consent of their donor
36Importance 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.