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Cell Structure & Function
Chapter 7 Miss Colabelli
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The Discovery of Cells All living things are made up of one or more cells A cell is the smallest unit that can carry out life processes
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The Discovery of Cells The Cell Theory
A composition of understandings from different scientists that all cells must go by All living things are composed of one or more cells Cells are the basic unit of structure and function in an organism Cells come only from the reproduction of pre-existing cells
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Cell Size Cell Size Cells are limited by the relationship of their
outer surface area to its volume As a cell grows, its volume increases much faster than the surface area Important to know because nutrients and wastes need to move though the cell efficiently A cell too large would take too long to diffuse these materials and it can harm the cell Most cells are better off being smaller and keeping their surface area to volume ratio bigger
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Inner life of the cell
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Plasma Membrane Cytoplasm Nucleus Cell’s outer boundary
Covers the cell’s surface and acts as a barrier between inside and outside of the cell Cytoplasm Area within the cell that contains the fluid, cytoskelelton, and the organelles Nucleus Membrane-bound area of the cell that contains genetic information Controls the function of the cell
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Two Basic Types of Cells
Prokaryote Eukaryote Organisms that lack a membrane-bound nucleus and membrane-bound organelles General area of cell where genetic information is located is called the nucleoid Usually bacteria and archaea Contain a membrane- bound nucleus and organelles with membranes Organelles carry out functions for the cell Usually plant and animal cells
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Tools & Techniques Tools are objects to improve the performance of a task. Microscopes are tools that extend human vision by enlarging images of specimens
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Light Microscope Compound light microscope
Shines light through a specimen Two lenses to enlarge image Specimen need to be thin and on a glass slide
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Light Microscope Staining slides of cells
Light passes through specimen and use lens to magnify the cells Viewing cells 1 mm to 1 micron in length
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Light Microscope Simplest parts of the microscope Eyepiece/Ocular lens
Objective lenses Stage Light source
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Magnification Increase of an object’s apparent size
Objective lenses on light microscope determine the magnification Usually have objectives 4X, 10X, & 40X Eyepiece = 10X Magnification = eyepiece X objective
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ELECTRON MICROSCOPE Uses beams of electrons that are focused by magnetic fields Higher resolution than light microscopes Can view cells 50 microns to < 1 nanometer
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Transmission Electron Microscope
Uses electrons through slices of specimens Gives a 2D view Samples must be thin
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Scanning Electron Microscope
Gives a 3D images of cells Beams of electrons to the specimen
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Microscopes!
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Questions How do microscopes work?
What does it mean if a micrograph is “false-colored?”
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Questions What adjustment knob is used once in high power?
When would a scientist use SEM over TEM?
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http://www.wisc- online.com/objects/ViewObject.aspx?ID=BIO905
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http://micro. magnet. fsu
opy/magnify1/index.html
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Plasma Membrane Membrane Lipids Membrane Proteins
Made of two layers of phospholipids (phospholipid bilayer) Membrane Proteins Specific proteins embedded in the lipid bilayer These proteins help with transporting molecules across the membrane and act as receptors Send messages to the rest of the cell
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Nucleus Houses and protects the cell’s genetic information
Contains instructions for the structure and function of the organism Before a cell divides, the DNA condenses to form chromosomes Nuclear envelope Double membrane that surrounds the nucleus Made of two phospholipid bilayers Contains pores (holes) called nuclear pores for RNA and other materials to enter and leave the nucleus Nucleolus Dense area in the nucleus where DNA is concentrated Where ribosomes are produced
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Mitochondria Organelles that transfer energy from organic matter (foods) to ATP ATP powers most of the cell’s chemical reactions Highly active organelles Two layer of membrane Outer membrane holds cytosol Inner membrane has folds called cristae where energy- harvesting chemical reactions take place
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Mitochondria Mitochondrial DNA
Have their own DNA and reproduce on their own Scientists think mitochondria originated from prokaryotic cells and were incorporated into eukaryotic cells Called the endosymbiotic theory
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Ribosomes Small, spherical organelles that are responsible for synthesizing proteins Do not have a membrane Made of protein and RNA molecules Synthesized in the nucleus Made of two subunits Some are free in the cytoplasm and some are attached to another organelle called the endoplasmic reticulum
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Endoplasmic Reticulum (ER)
System of membranous tubes Functions as a highway for molecules to move throughout the cell Two types of ER Rough ER Smooth ER
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Rough Endoplasmic Reticulum
System of interconnected tubes covered with ribosomes Ribosomes make it look “rough” Area where some proteins are made
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Smooth Endoplasmic Reticulum
Lacks ribosomes and looks smooth Builds lipids like cholesterol and hormones for the body Helps detoxify drugs and poisons Liver cells contain a high amount or smooth ER cells Long-term drug and alcohol users also increase their smooth ER organelles in their cells
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Golgi Apparatus System of flattened sacs
Sacs near the nucleus receive vesicles from the ER that contain newly made proteins and lipids Vesicles travels through the Golgi Golgi apparatus “stamps” the vesicles to where they need to travel to in the cell Like address labels
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Vesicles Small sphere like sacs that are surrounded by a single membrane Lysosomes Vesicles that bud from the Golgi and contain enzymes that break down large molecules Also help break down cells when it is time for the cell to die Peroxisomes Similar to lysosomes except contain different enzymes Neutralize radicals and detoxify alcohol and drugs Produce hydrogen peroxide as a product in their chemical reactions
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Cytoskeleton Network of thin tubes and filaments that crisscross the cytosol Give the cell its shape Like poles in a tent Internal tracks where items in the cell move around the cell Three different types of tubes found in the cytoskeleton Microtubules Microfilaments Intermediate filaments
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Microtubules Hollow tubes made of protein called tubulin
Radiate outward from the center called centrosome near the nucleus Hold organelles in place Maintain cell shape Act as tracks to guide organelles and molecules as they move within the cell
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Microfilaments Smaller than microtubules
Long threads of bead like protein called actin Contribute to cell movement Crawling white blood cells Muscle contraction
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Intermediate Filaments
Rods that anchor the nucleus and organelles in place Maintain internal shape of the nucleus Make up most of the hair shaft
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Cilia and Flagella Hair like structures that extend from the surface of the cell Assist in movement Cilia Short and present in large numbers Flagella Long extensions of the cell, usually one that helps with the cell moving
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Centrioles Two short cylinders of microtubules at right angles to each other Near the nuclear envelope Occur only in animal cells Organize microtubules of cytoskeleton during cell division
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Plant Cells Most of the organelles and parts of the cell are in all eukaryotic cells Plants have three additional structures Cell wall Central vacuole Plastids
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Cell Wall Rigid layer that lies outside the cell’s plasma membrane
This cell wall is composed of the polysaccharide cellulose Primary cell wall On top of the plasma membrane Can grow in one direction Secondary cell wall Between the plasma membrane and the primary cell wall Does not grow
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Central Vacuole Reservoir that stores large amounts of water, enzymes, wastes, and other materials Large, fluid filled organelle May take up 90% of the cell’s volume When there is a lot of water the vacuole fills up When there is little water the vacuole deflates
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Plastids Double membrane organelles and contain their own DNA
Chloroplasts Use light energy and water to make food and oxygen Used in photosynthesis
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Comparing cells Prokaryote Eukaryote Lack a nucleus
No membrane-bound organelles Region called nucleoid Bacteria and archaea Have a nucleus Membrane-bound organelles Plant and animal cells
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Comparing Cells Plant cell Animal Cell Cell wall Large central vacuole
Contain plastids No cell wall No vacuole Contain centrioles
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