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Cell Structure & Function
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Definition of Cell A cell is the smallest unit that is capable of performing life functions.
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Examples of Cells Muscle Cell Skin Cell Bacteria Red Blood Cell
Nerve Cell
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Prokaryotic Eukaryotic
Two Types of Cells Prokaryotic Eukaryotic
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Prokaryotic Do not have structures surrounded by membranes
Few internal structures One-celled organisms, Bacteria
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Prokaryotic Cell
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Eukaryotic Contain organelles surrounded by membranes
Most living organisms Plant Animal
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Eukaryotic Cells Eukaryotic cells -possess a membrane-bound nucleus -are more complex than prokaryotic cells -compartmentalize many cellular functions within organelles and the endomembrane system -possess a cytoskeleton for support and to maintain cellular structure
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“Typical” Animal Cell
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Eukaryotic Cells
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Eukaryotic Cells Nucleus
-stores the genetic material of the cell in the form of multiple, linear chromosomes -surrounded by a nuclear envelope composed of 2 phospholipid bilayers -in chromosomes – DNA is organized with proteins to form chromatin
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Eukaryotic Cells
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Cell Parts Organelles
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Surrounding the Cell
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Cell Membrane Outer membrane of cell that controls movement in and out of the cell Phospholipid bilayer Composed of multiple types of proteins
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Function of Cell Membrane
Cell membrane provides gateway to most of the body’s metabolic reactions Major Processes: Passive and Active Transport Passive Diffusion: Diffusion and Filtration Diffusion: process by which molecules move away from region of high concentration to low concentration (concentration gradient) Simple Diffusion: Molecules can move freely through the membrane (osmosis: diffusion of water) Facilitated Diffusion: Provides passage of larger molecules too big to move through membrane
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Function of Cell Membrane
Active Transport: requires ATP to move molecules across membrane Molecules can move across gradient Sodium-Potassium Pump: carries ions into nerve cells via ATP Exocytosis: moves substances out of the cell Endocytosis: moves substances in the cell
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Inside the Cell
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Nucleus Directs cell activities
Separated from cytoplasm by nuclear membrane Contains genetic material - DNA
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Nuclear Membrane Surrounds nucleus Made of two layers
Phospholipid bilayer Openings allow material to enter and leave nucleus
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Nucleolus Inside nucleus Site of ribosome production
Contains RNA to build proteins Site of translation
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Cytoplasm Gel-like mixture (cytosol) Surrounded by cell membrane
Mostly composed of water Anchors organelles within the cell Surrounded by cell membrane Where most of the human body’s metabolic reactions occur
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Mitochondria Produces energy through chemical reactions – breaking down fats & carbohydrates Controls level of water and other materials in cell Found in higher concentrations in higher energy organs (i.e. liver, muscle)
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Mitochondria
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Endoplasmic Reticulum
Moves materials around in cell Smooth type: lacks ribosomes; involved in lipid metabolism Rough type (pictured): ribosomes embedded in surface Functions to fold and transport proteins across the cell
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Ribosomes Each cell contains thousands of ribosomes
Site of protein synthesis Found on ribosomes & floating throughout the cell
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Golgi Bodies Protein 'packaging plant' Move materials within the cell
Move materials out of the cell
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Lysosome Digestive 'plant' for proteins, fats, and carbohydrates
Transports undigested material to cell membrane for removal Cell breaks down if lysosome structure is disrupted.
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Peroxisomes Membranous sacs that contain oxidase enzymes
Work to detoxify harmful substances Most numerous in liver and kidney cells
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Endomembrane System (4.6 – 4.9)
Series of organelles responsible for: Modifying protein chains into their final form Synthesizing of lipids Packaging of fully modified proteins and lipids into vesicles for export or use in the cell And more that we will not cover!
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Cell Structure All Cells have: an outermost plasma membrane
genetic material in the form of DNA cytoplasm with ribosomes
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Why Are Cells So Small? (4.2)
Cells need sufficient surface area to allow adequate transport of nutrients in and wastes out. As cell volume increases, so does the need for the transporting of nutrients and wastes.
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Why Are Cells So Small? However, as cell volume increases the surface area of the cell does not expand as quickly. If the cell’s volume gets too large it cannot transport enough wastes out or nutrients in. Thus, surface area limits cell volume/size.
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Why Are Cells So Small? Strategies for increasing surface area, so cell can be larger: “Frilly” edged……. Long and narrow….. Round cells will always be small.
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