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Cell Structure & Function
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Cell Theory Definition of Cell All living things are made up of cells.
Cells are the smallest working units of all living things. All cells come from preexisting cells through cell division. Definition of Cell A cell is the smallest unit that is capable of performing life functions.
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Prokaryotic Do not have structures surrounded by membranes
Few internal structures One-celled organisms, Bacteria
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Eukaryotic Plant Animal Contain organelles surrounded by membranes
Most living organisms Plant Animal
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Parts of the Cell Mitochondria Vacules Cytoplasm Nucleus Rough ER Plasma membrane Lysosomes Smooth ER Golgi Bodies Ribosomes All working together so that the cell can grow, work, repair, and reproduce
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Surrounding the Cell Plasma Membrane
Outer membrane of cell that controls movement in and out of the cell Double layer
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Functions of Plasma Membrane
The Plasma Membrane 4/26/2017 Functions of Plasma Membrane Protective barrier Regulate transport in & out of cell Allow cell recognition Receptor proteins function in cell communication Contains the cytoplasm (fluid in cell) Provide a binding site for enzymes G. Podgorski, Biol. 1010
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Homeostasis Cells must keep the proper concentration of nutrients and water and eliminate wastes. The plasma membrane is selectively permeable – it will allow some things to pass through, while blocking other things.
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Structure of the Plasma Membrane
Lipid bilayer – two sheets of phospholipids. Found around the cell, the nucleus, vacuoles, mitochondria, and chloroplasts. Embedded with proteins and strengthened with cholesterol molecules.
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What is a Phospholipid? It’s a pair of fatty acid chains and a phosphate group attached to a glycerol backbone. Polar (hydrophilic) phosphate heads face out & the nonpolar (hydrophobic) fatty acids hang inside.
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Membrane Proteins Determine what particles can pass through the membrane. Serve as enzymes (may speed reactions). Act as markers that are recognized by chemicals and molecules from the inside and the outside of the cell (the immune system).
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Receptors, enzymes, crossing
Phosphate Polar Cholesterol structure & support Fatty acid nonpolar Carbohydrate chains identification Membrane proteins Receptors, enzymes, crossing FLUID- because individual phospholipids and proteins can move around freely within the layer, like it’s a liquid. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above. Extracellular (outside the cell) Intracellular (inside the cell)
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Nucleus Directs cell activities Contains genetic material - DNA
Separated from cytoplasm by nuclear membrane Surrounds nucleus Made of two layers Openings allow material to enter and leave nucleus
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Inside the nucleus Chromosomes Nucleolus Made of DNA
Contain instructions for traits & characteristics Nucleolus Contains RNA to build proteins
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Endoplasmic Reticulum
Moves materials around cell Smooth type: cholesterol & fat synthesis & breakdown (lipid metabolism); lacks ribosomes Rough type: the cell’s membrane factory; ribosomes embedded in surface
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Ribosomes Make proteins Each cell contains thousands
Found on ribosomes & floating throughout the cell
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Mitochondria Produces energy
Cellular respiration - chemical reactions breaking down fats & carbohydrates Controls level of water and other materials in cell Recycles and decomposes proteins, fats, and carbohydrates
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Golgi Bodies Protein packaging
Proof reads proteins & makes minor corrections Move materials within the cell Move materials out of the cell
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Lysosomes Breaks down molecules
‘Digests’proteins, fats, and carbohydrates Transports undigested material to cell membrane for removal Cell breaks down if lysosome explodes Hydrolytic enzymes
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Vacuoles sacs for storage Also used for digestion, and waste removal
Contains water solution Help plants maintain shape
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Cytoplasm Fills cell & holds organelles
Gel-like mixture - mostly water Protects & stabilizes organelles Surrounded by cell membrane
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Cellular Respiration Cells break down food sources i.e. glucose, fats, and protein &release their stored energy. Produce energy storage molecules called ATP – adenosine triphosphate.
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Anaerobic Processes No oxygen is required for these processes.
Includes glycolysis, the breakdown of glucose, and fermentation. Some bacteria and yeast are examples of anaerobes.
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Glycolysis Occurs in the cytoplasm. Breaks down glucose
2 molecules of pyruvate (3- carbon structures) 2 ATP molecules are formed. 2 NADH energy shuttles are also formed.
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Fermentation Pyruvate can be metabolized by: Alcoholic fermentation or Lactic acid fermentation Alcoholic Fermentation produces ethyl alcohol and CO2 Lactic acid fermentation produces lactic acid.
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Aerobic Processes C6H12O6 + 6O2 6CO2 + 6H2O + Energy
Requires oxygen. Most organisms are aerobes. Equation for Aerobic respiration: C6H12O6 + 6O2 6CO H2O + Energy
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The Mitochondria If O2 is present following glycolysis, pyruvate is modified and enters the mitochondria. Here food is broken down completely into CO2. Energy storage molecules like NADH and ATP are produced.
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The Role of Oxygen Energy carriers like NADH drop off electrons
ATP Energy from electrons O2 Energy carriers like NADH drop off electrons As the electrons “fall” to oxygen energy is stored in a payload of ATP. Oxygen picks up electrons and hydrogen ions to form water. H2O
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ATP: Adenosine Triphosphate
ATP is the cells energy currency. Cellular work such as metabolism, transport, and movement is powered by the breakdown of ATP. ATP Structure Ribose – a 5-carbon sugar Adenine – a N-base 3 phosphate groups
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ATP / ADP Cycle ATP is constantly being used and remade in the cell.
Energy is released or stored by breaking or making a phosphate bond.
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Summary of Cellular Respiration
Process Where Process Occurs Net Gain of ATP Per Glucose Anaerobic Glycolysis & Fermentation Cytoplasm 2 ATP Aerobic Krebs Cycle and Electron Transport Mitochondrion 36 ATP
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Selectively Permeable
Phospholipid Bilayer Active & Passive transport mechanisms move molecules across the membrane
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Transport Across the Membrane
Passive Active
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Simple Diffusion Requires NO energy
Molecules move from area of HIGH to LOW concentration The solute moves down the concentration gradient – from an area of high concentration of solute to an area of low concentration of solute until equilibrium is reached then simple diffusion stops
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Simple Diffusion Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY Example: Oxygen or water diffusing into a cell and carbon dioxide diffusing out.
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Facilitated Diffusion
Molecules will randomly move through the pores in Transport Proteins. Uses transport proteins to move high to low concentration Examples: Glucose or amino acids moving from blood into a cell. High concentration of solute Low concentration of solute
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Facilitated Diffusion
Some Carrier proteins do not extend through the membrane. They bond and drag molecules through the lipid bilayer and release them on the opposite side.
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Facilitated Diffusion
Other carrier proteins change shape to move materials across the cell membrane Along the concentration gradient
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Osmosis Diffusion of water across a membrane
High water potential Diffusion of water across a membrane Moves from HIGH water potential (low solute) to LOW water potential (high solute) Low water potential
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Cells in Solutions
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NO NET MOVEMENT OF H2O (equal amounts entering & leaving)
Isotonic Solution Hypotonic Solution Hypertonic Solution NO NET MOVEMENT OF H2O (equal amounts entering & leaving) CYTOLYSIS PLASMOLYSIS
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Active Transport Requires energy or ATP
Moves materials from LOW to HIGH concentration Examples: Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients. The sodium potassium pump important in nerve impulses AGAINST concentration gradient
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Exocytosis- moving things out.
Molecules are moved out of the cell by vesicles that fuse with the plasma membrane. Active Transport This is how many hormones are secreted.
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Endocytosis- moving things in
Pinocytosis Phagocytosis Most common form of endocytosis. Ingestion of solid particles by endocytosis Takes in molecules dissolved in H2O. Fuses with lysosomes and the material is degraded
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