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Cells

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All living organisms are made of

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Hm-m-m-m Should I ask a question?

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Many life forms consist of only one cell. unicellular

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Others consist of many cells multicellular

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Brachiating Gibbon Brachiating Gibbon

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Viewing and Studying Cells Microscopes Microscopes First developed in 1600s First developed in 1600s Advances in technology have advanced knowledge Advances in technology have advanced knowledge Von Leewenhoeks microscope and drawings

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Produced early micrographs

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Todays microscopes

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Transmission Electron Microscopes Use a beam of electrons instead of light Use a beam of electrons instead of light Very large & expensive Very large & expensive Can not be used on living specimens Can not be used on living specimens

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Scanning Electron Microscope (SEM) Uses a beam of electrons Uses a beam of electrons Cannot be used on living organisms Cannot be used on living organisms 3-D photographs 3-D photographs

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A cell is the smallest unit that can carry out all the activities necessary for life. How Big is a... ?

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Cell sizes vary from the ostrich eggthe largest of cells

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To minute bacteria

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Most cells are microscopic

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Some might say that a cell is like a submarine

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A submarine is protected by a tough hull

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And a cell is protected by a cell membrane

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However.. A cell membrane is far more complex than a submarine hull

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It has to allow.. food to enter the cell waste to leave the cell

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The cell membrane helps maintain homeostasis in the cell.

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When cells are small, they work efficiently Their inner structures are close to the membrane

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When cells are LARGE Their inner structures are further from the membrane

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waste Large cells need more food and produce more waste food waste This is difficult!

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As cells grow, their outer surface area is not large enough to provide for enough food uptake and waste disposal

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So cells can not grow indefinitely

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so getting back to the idea of a submarine..

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All cells are surrounded by water

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Water is also present inside the cell H2OH2O H2OH2O H2OH2OH2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O

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Lets look closely at water. Water H 2 O is 2 H atoms covalently bonded with 1 oxygen atom

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Water is a polar molecule

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The charged ends of water molecules, attract other water molecules

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These attractions are known as Hydrogen Bonds.

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Hydrogen bonds are important in nature. They cause water molecules to stick together.

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Thats one reason why some insects can walk on water

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And some lizards can run on it

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So lets put all this together and see how water shapes the cell membrane In a test tube, pour a layer of oil on top of some water

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Even if you shake and mix it thoroughly, the water and oil eventually return to two separate layers

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Hydrogen bonds cause the polar water molecules to cluster together

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But lipids are nonpolar Not attracted to water Pushed away and separated from the water

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The force of water pushing on the lipid layer is what shapes the membrane

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3.2 Membrane Architecture

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Cell membranes act like a giant security system for a cell

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To understand how membranes work, you have to understand how they are formed.

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Phospholipids are the basic building blocks of membranes.

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They form phospholipid bilayers Polar heads point toward water inside and outside of the cell. Nonpolar tails are inside the membrane away from the water.

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Lipid bilayers are fluid, not rigid Cells can exist in a variety of shapes. Cells can be flexible.

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That leads to an important question How do necessary molecules such as glucose get into the cell? How do necessary molecules such as glucose get into the cell? Feed me !

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Membranes have protein gates which regulate the flow of substances in and out of the cell.

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Membrane proteins have several functions

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Channel Proteins Allow the transport of substances into and out of the cell Allow the transport of substances into and out of the cell..like kidney cells that remove wastes Myocyte: Ion Channels

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Receptor Proteins Transfer information from the outside environment into the cell Transfer information from the outside environment into the cell like brain cells..when you learn

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Surface Marker Proteins name tags AB +

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Membrane proteins often work together Marker proteins direct cells in their development Channel proteins aid in cell functions Channel and receptor proteins also allow communication between cells!

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OK..so heres more questions How can proteins perform such different tasks?

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How do the proteins fit into the lipid bilayer membrane?

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The answer lies in the structure of the protein

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Lets Review Proteins are made of long chains of amino acids Proteins are made of long chains of amino acids Each of the 20 amino acids are different from each other Each of the 20 amino acids are different from each other The arrangement of a.a. ultimately determines protein structure The arrangement of a.a. ultimately determines protein structure

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Charges on the protein chains cause them to bend, fold and twist

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A proteins complicated structure determines its function.

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Membrane proteins have 3 basic sections. 2 Polar ends Hydrophillic Form hydrogen bonds with water

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Middle. nonpolar coil Fits into nonpolar center of membrane Can float and move within the membrane

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Congratulations! You passed through the cell membrane You passed through the cell membrane You are now ready to dive into cells You are now ready to dive into cells

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Inside the Cell Inside the Cell Chapter 3.3

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Two Types of Cells Prokaryotic Prokaryotic Prokaryotes Prokaryotes Eukaryotic Eukaryotic Eukaryotes Eukaryotes

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Eukaryotic Cells vs. Prokaryotic Cells Eukaryotes Eukaryotes Contain a nucleus Contain a nucleus Have double stranded DNA Have double stranded DNA DNA forms chromosomes DNA forms chromosomes Plants and Animals Plants and Animals Prokaryotes Prokaryotes Lack a nucleus Lack a nucleus Have a single, circular strand of DNA Have a single, circular strand of DNA DNA is not surrounded by a membrane DNA is not surrounded by a membrane Bacteria Bacteria

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Lets Compare ProkaryotesEukaryotes No nucleus Nucleus No membrane bound organelles Many organelles Most 1 -10 microns Many 2 -1,000 microns Evolved 3.5 billion years ago Evolved 1.5 billion years ago Only bacteria Plants, animals, protists

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Like Characteristics ProkaryotesEukaryotes Cell membrane Cytoplasm An internal fluid environment Cytoplasm Ribosomes Location of protein synthesis Ribosomes

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Eukaryotes vs. Prokaryotes Complex vs. simple structure Complex vs. simple structure Organelles

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Think of a cell as a factory..

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Each organelle is a separate department Each department has a separate job Each department has a separate job

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Nucleus Control center of the cell Control center of the cell Contains DNA Contains DNA Complete genetic set of instructions Complete genetic set of instructions Humans = 23 chromosomes Humans = 23 chromosomes Surrounded by a membrane Surrounded by a membrane Has pores to allow movement in and out of membrane Has pores to allow movement in and out of membrane Nuclear pores Nuclear pores

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Nuclear Membrane

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Cells Manufacture and Release Energy Mitochondria Mitochondria Animals and plants Animals and plants Chloroplasts Chloroplasts Plants only Plants only

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Mitochondria Powerhouse of the cell Powerhouse of the cell Convert energy stored in food to ATP Convert energy stored in food to ATP Bound by a double membrane Bound by a double membrane Outer membrane is smooth Outer membrane is smooth Inner membrane is highly folded Inner membrane is highly folded

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Chloroplasts Plants use chloroplasts to make food from CO 2, H 2 O and solar energy Plants use chloroplasts to make food from CO 2, H 2 O and solar energy They contain the green pigment, chlorophyll. They contain the green pigment, chlorophyll. Photosynthesis Photosynthesis Found ONLY in plants Found ONLY in plants

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Cells Maintain Homeostasis Endoplasmic reticulum Endoplasmic reticulum Eukaryotes Eukaryotes Transport network Transport network Golgi Apparatus Golgi Apparatus Packaging and distribution center Packaging and distribution center

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Endoplasmic Reticulum (ER) A membrane system that is continuous with the nuclear envelope A membrane system that is continuous with the nuclear envelope Many different activities Some ribosomes are attached to some parts of the ER Some ribosomes are attached to some parts of the ER Appears rough rough ER If ribosomes are not attached If ribosomes are not attached Appears smooth smooth ER

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Endoplasmic reticulum

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Endoplasmic reticulum (ER) Transport system for many molecules Transport system for many molecules Major manufacturing center of the cell Major manufacturing center of the cell Proteins Proteins Lipids Lipids Membranes for other organelles Membranes for other organelles Packages some molecules for transport to Golgi bodies Packages some molecules for transport to Golgi bodies

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Golgi Apparatus Packaging, Labeling and Shipping Center Packaging, Labeling and Shipping Center Membrane system of vesicles Membrane system of vesicles Assembly point for items to be exported from the cell Assembly point for items to be exported from the cell Packages and sorts proteins and polysaccharides Packages and sorts proteins and polysaccharides Move through vesicles To plasma membrane To other organelles Outside the cell The Post Office

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Golgi Apparatus

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Vacuoles Storerooms Storerooms Storage vesicles Storage vesicles Food & water Food & water Digestion Digestion Digestive Enzymes Digestive Enzymes Support Support Water Regulation Water Regulation Contractile vacuoles Contractile vacuoles

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Vacuoles

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Lysosomes special digestive vacuoles Where did the tail go?

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Centrioles Found in pairs Found in pairs Help in cell division Help in cell division Animal cells only Animal cells only

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Plant Cells

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Cell Wall Plant cells Plant cells Contains cellulose and protein Contains cellulose and protein Provides strength Provides strength Provides rigidity Provides rigidity

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Large Central Vacuole Nutrient, water and waste storage Nutrient, water and waste storage May occupy 30*90% of cell volume May occupy 30*90% of cell volume Helps plant stand upright Helps plant stand upright

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Lets Compare

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Animal Cell vs. Plant Cell

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Theory of Endosymbiosis

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Evidence for Endosymbiosis Many bacteria and mitochondria are the same size and have a set of double membranes Many bacteria and mitochondria are the same size and have a set of double membranes Mitochondria have their own ribosomes and DNA Mitochondria have their own ribosomes and DNA Their ribosomes are structurally similar to prokaryote ribosomes Their ribosomes are structurally similar to prokaryote ribosomes Some organelles divide in a manner similar to bacteria Some organelles divide in a manner similar to bacteria