Chapter 1 Notes Cells A Review MIL.docx - Chapter 1: Cells-...

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Chapter 1: Cells- A ReviewRelevant Study Design Key KnowledgeCells: The basic units of lifeCells are the basic structural and functional units of life: all organisms are built of one or more cells.Refresher: The wacky history of cell theory Ted-ed (6 minutes)Cells: how big?Typically, cells are microscopic. There are a few single cells that can be seen with the unaided eye.*You fill these some examples hereTypical cell sizesCellSize rangePlant10 – 100 µmAnimal10 – 40 µmMicrobial cells0.4 -0.2 µmViruses are non-living; they cannot self-replicate without a living cell. They do not have a cellularstructure and cannot carry out metabolic activities by themselves. They range in size from 20-300nm.Remember: 1 µm = 10-6m1nm = 10-9m*You do some converting:a) 1mm =µmb) 1 µm =nmc) 1mm =nm
Cells: all sorts of shapesCells vary in shape, and this generally reflects their function*How does a motor neuron’s shape assist its function?*How do proteins in smooth muscle cells assist their functionBacterial cells also come in a variety of shapes.Not all cells have a fixed shape. If cells move (self-propelled), they need to be able to change shape.Examples of cells that can change shape include: cancer cells, white blood cells, amoebaSome cells have a fixed shape due to a rigid cell wall, but can still move using cilia or flagella.Also look at the examples in your textFig 1.4
Cells: why so small?Refresher on surface area to volume ratios!If you need it, a similar experiment to the one we did last year (2 mins 44)Cells must maintain their environment within narrow limits: pH, ion concentration, chemicalcompound etc. must be at certain levels. Because of a cell’s functions, materials are constantly beingrequired or being produced. So a cell is continually exchanging materials with its externalenvironment.Materials are exchanged across the plasma membrane, and the rate of exchange must occur at a ratethat allows the cell to maintain its activities.Surface area is the outside of the cell, volume the inside. SA:V is a comparison of the outside to theinside. The bigger the ratio, the quicker materials can cross from the exterior of the cell to theinterior). The smaller the organism or cell, the larger SA:V.When you increase cell size, both surface area and volume increases, but not at the same rate. Theratio (comparison between them) decreases.If cells were to grow too big, their SA:V would decrease and they could not exchange materialsquickly enough to maintain their functions- leading to cell death.Some cells increase their surface area by folding the plasma membrane e.g. microvilli in the digestivesystem.Interactive to see how SA:V changes with size and shape; please note, only works on Internetexplorer, not ChromeSizes of cells quiz (4MC) Your Score:Prokaryotes: No nuclear envelope

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