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Chapter 4 Notes

by: Michela Spicer

Chapter 4 Notes BSC 108

Michela Spicer

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These notes cover everything discussed in class regarding chapter 4.
Intro to Biology Non-Maj
Dr. Yates
Class Notes
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This 6 page Class Notes was uploaded by Michela Spicer on Sunday September 18, 2016. The Class Notes belongs to BSC 108 at University of Alabama - Tuscaloosa taught by Dr. Yates in Fall 2016. Since its upload, it has received 3 views. For similar materials see Intro to Biology Non-Maj in Biology at University of Alabama - Tuscaloosa.


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Date Created: 09/18/16
Drugs that target bacterial cells  Antibiotics were first isolated from mold in 1928  The widespread use of antibiotics drastically decreased deaths from bacterial infections  Most antibiotics kill bacteria while minimally harming the human host by binding to structures found only on bacterial cells  Some antibiotics bind to the bacterial ribosome, leaving human ribosomes unaffected  Other antibiotics target enzyme found only in the cells Microscopes as windows on the world of cells  Light microscopes can be used to explore the structures and functions of cells  When scientists examine a specimen on a microscope slide oLight passes through the specimen oLenses enlarge, or magnify, the image  Two factors that determine the quality of microscopy oMagnification is an increase in the specimen’s apparent size o Resolving power is the ability of an optical instrument to show two objects as separate Microscopes  Cells were first described in 1665 by Robert Hooke  The accumulation of scientific evidence led to the cell theory oAll living things are composed of cells oAll cells come from other cells  The light microscope is used by many scientists oLight passes through the specimen oLenses enlarge, or magnify, the image  The electron microscope (EM) uses a beam of electrons oResults in better resolving power than the light microscope  Two kinds of electron microscopes reveal different parts of cells oScanning electron microscopes examine cell surfaces o Transmission electron microscopes (TEM) are useful for internal details of cells Features common to all cells  All cells have a plasma membrane oPhospholipid bilayer, selective barrier  All cells have a cytosol or cytoplasm oThe area within the membrane not including organelles  All cells have at least one chromosome oContaining DNA  All cells have ribosomes oSites of protein synthesis The two major categories of cells  The countless cells on Earth fall into two categories oProkaryotic cells  Bacteria and Archaea  Smaller than eukaryotic cells  Lack internal structures surrounded by membranes  Lack a nucleus  Have a rigid cell wall  Prokaryotes have cell walls that are unique  Bacterial walls are made of peptidoglycan  A target for antibiotics oEukaryotic cells  Plants, fungi, and animals  All cells have several basic features oThey are all bound by a thin plasma membrane oAll cells have DNA and ribosomes, tiny structures that build proteins  Prokaryotic and eukaryotic cells have important differences oProkaryotic cells are older than eukaryotic cells  Prokaryotes appeared about 3.5 billion years ago; eukaryotes about 2.1 billion years ago Membrane structure  The plasma membrane separates the living cell from its nonliving surroundings  The membranes of a cell are composed mostly of oLipids oProteins  The lipids belong to a special category called phospholipids  Phospholipids form a two-layered membrane, the phospholipid bilayer  Membranes are not static sheets of molecules locked rigidly in place  Membrane phospholipids and proteins can drift about in the plane of the membrane  This behavior leads to the description of a membrane as a fluid mosaic oA high diversity of proteins exists within the membrane oThe proteins can move freely within the membranes Cell surfaces  Most cells secrete materials that coat their outside surfaces oExternal to the plasma membrane oHelps protect and support cells  Many cells also have structures that facilitate interactions with their neighbors oCell junctions: very important in communication between cells  Adhesion: between your skin, cell to cell  Tight: bladder  Gap: only in your heart  Plant cells have cell walls outside of their membranes oProtect the cells oMaintain their shape oKeeps the cells from absorbing too much water oMade mostly of cellulose- a carbohydrate  Animal cells have an extracellular matrix oHelps hold cells together in tissues and protects and supports them Structure and function of the Nucleus  The nucleus is bordered by a double membrane called the nuclear envelope  Pores in the envelope allow materials to move between the nucleus and cytoplasm  The nucleus contains a nucleolus where ribosomes are made  Stored in the nucleus are long DNA molecules and associated proteins that form fibers called chromatin  Each long chromatin fiber constitutes one chromosome  The number of chromosomes in a cell depends on the species Ribosomes  Ribosomes are responsible for protein synthesis  Ribosome components are made in the nucleolus  Ribosomes may assemble proteins oSuspended in the fluid of the cytoplasm o Attached to the outside of an organelle called the endoplasmic reticulum  DNA directs protein production by transferring its coded information into messenger RNA (mRNA) o Messenger RNA exits the nucleus through pores in the nuclear envelope o A ribosome moves along the mRNA translating the genetic message into a protein with a specific amino acid sequence  DNA  RNA  Protein The Endomembrane system: manufacturing and distributing cellular products  Several membranous organelles belong to the endomembrane system oEndoplasmic Reticulum  Modifies an enormous variety of proteins that are first made on ribosomes  Is compose of smooth and rough ER  Rough ER  The rough appearance of parts of the ER is due to ribosomes that stud the outside of the ER membrane  The functions of the rough ER include the modification of  Membrane proteins  Secretory proteins  And the production of new membrane  After the rough ER synthesizes a molecule, it packages the molecule into transport vesicles  Smooth ER  The smooth ER lacks surface ribosomes  It produces lipids, including steroids  It also is home to enzymes that detoxify foreign molecules Ex: Drugs  As liver cells are exposed to a drug the amounts of smooth ER increases  Means the body will require more amounts of that drug to achieve the same effect oGolgi Apparatus  Works in partnership with the ER  Refines, stores, and distributes the chemical products of cells oLysosomes  A lysosome is a sac of digestive enzymes found in animal cells  Enzymes in a lysosome can break down large molecules such as  Proteins  Polysaccharides  Fats  Nucleic Acids  Lysosomes have several types of digestive functions  Many cells engulf nutrients in tiny cytoplasmic sacs called food vacuoles  These food vacuoles fuse with lysosomes, exposing food to enzymes to digest the food  Small molecules from digestion leave the lysosome and nourish the cell  Lysosomes can also  Destroy harmful bacteria  Break down damaged organelles  Lysosomes and Disease  Several serious inherited disorders are the result of malfunctioning lysosomes Lysosomal storage diseases The lysosomes lack functioning enzymes  Undigested molecules accumulate  Ex: Tay-Sachs Disease- lipids build up in the brain oVacuoles  Vacuoles are membranous sacs that bud from the  ER  Golgi  Plasma membrane  Contractile vacuoles of protists pump out excess water in the cell  Central vacuoles of plants  Store nutrients  Absorb water  May contain pigments or poisons oNuclear envelope Chloroplasts and Mitochondria: Energy conversion  Cells require a constant energy supply to perform the work of life  Chloroplasts o Most of the living world runs on the energy provided by photosynthesis o Photosynthesis is the conversion of light energy from the sun to the chemical energy of sugar o Chloroplasts are the organelles that perform photosynthesis o Chloroplasts have three major compartments  The space between the two membranes  The stroma, a thick fluid within the chloroplast  The space within grana, the structures that trap light energy and convert it to chemical energy  Mitochondria o Mitochondria are the sites of cellular respiration, which produce ATP from the energy of food molecules o Mitochondria are found in almost all eukaryotic cells o An envelope of two membranes encloses the mitochondrion. These consist of  An outer smooth membrane  An inner membrane that has numerous infoldings called cristae  Mitochondria and chloroplasts contain their own DNA, which encodes some of their proteins  This DNA is evidence that mitochondria and chloroplasts evolved from free-living prokaryotes in the distant past The Cytoskeleton: cell shape and movement  The cytoskeleton is a network of fibers extending throughout the cytoplasm  The cytoskeleton oProvides mechanical support to the cell oMaintains its shape  The cytoskeleton contains several types of fibers made from different proteins oMicrotubules  Are straight and hollow  Guide the movement of organelles and chromosomes oIntermediate filaments and microfilaments are thinner and solid oThe cytoskeleton is dynamic Cilia and Flagella  Motile appendages  Flagella propels the cell in a whip like motion  Cilia moves in a coordinated back and forth motion


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