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209 Cards in this Set
- Front
- Back
What is the fundamental unit of all living things?
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The cell
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When was the cell discovered or studied in detail?
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In the 17th century
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Why did it occur then?
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Because of the invention of the microscope
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What is the Cell Theory?
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It is the unifying theory of what a cell is
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What are the four parts of the Cell Theory?
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All living things are composed of cells. The cell is the basic functional unit of life. Cells arise only from pre-existing cells. Cells carry genetic information in the form of DNA. This genetic material is passed from parent cell to daughter cell
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What are three tools available to study the cell and its structures?
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Microscopy, autoradiography, and centrifugation
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What is the most basic tool that scientists use?
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The microscope
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What is magnification?
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An increase in apparent size of an object
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What is resolution?
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The differentiation of two closely situated objects
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What is a compound light microscope?
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It is one that uses two lenses or lens systems to magnify an object
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What is the total magnification equal to?
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It is equal to the product of the eyepiece magnification (usually 10x) and the magnification of the selected objective lens (usually 4x, 10x, 20x, or 100x)
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What are the 3 chief components of the microscope?
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The diaphragm, the course adjustment knob, and the fine adjustment knob
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What does the diaphragm do?
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It controls the amount of light passing through the specimen
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What does the course adjustment knob do?
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It roughly focuses the image
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What does the fine adjustment knob do?
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It sharply focuses the image
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What is the compound light microscope generally used to observe?
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Nonliving specimens
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What does light microscopy require that results in cell death?
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It requires contrast between cells and cell structures
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How is this contrast obtained?
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Through staining techniques
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What is an example of this?
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The dye hematoxylin reveals the distribution of DNA and RNA within a cell due to its affinity for negatively charged molecules
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What is a phase contrast microscope?
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It is a special type of light microscope that permits the study of living cells
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What is used to produce the contrast between cellular structures?
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Differences in refractive index
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What benefit does this provide to the scientist?
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It does not kill the specimen
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How does an electron microscope work?
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It uses a beam of electrons to allow a thousand fold higher magnification than is possible with light microscopy
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Why is the examination of living specimens not possible with electron microscopy?
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Tissues must be fixed and sectioned, and sometimes stained with solutions of heavy metals
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What is autoradiography?
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It is a technique that uses radioactive molecules to trace and identify cell structures and biochemical activity
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How does this work?
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Cells are exposed to a radioactive compound for a brief, measured period of time
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Then what happens to the cells?
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They are incubated, fixed at various intervals and processed for microscopy
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What is each preparation covered with?
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A film of photographic emulsion
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What are environmental requirements for autoradiography?
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The preparations must be kept in the dark for several days while the radioactive compound decays
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What happens then?
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The emulsion is developed; dark silver grains reveal the distribution of radioactivity within the specimen
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What can autoradiography be used for?
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It can be used to study protein synthesis; labeling amino acids with radioactive isotopes allows the pathways of protein synthesis to be examined
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What is differential centrifugation?
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It is the type used to separate cells or mixtures of cells without destroying them in the process
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What happens to them at lower speeds?
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The mixtures separate into layers on the basis of cell type
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What do spinning fragmented cells at high speeds do?
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It causes their components to sediment at different levels in the test tube based upon their respective densities
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What happens to ribosomes when this occurs?
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They go to the bottom of the test tube
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What happens to mitochondria?
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They go to the top
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What happens to lysosomes?
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They go to the top
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What are the two groups of cells?
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Prokaryotic and eukaryotic
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What are viruses?
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They are a unique category all their own
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Are they considered cells?
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No
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Why not?
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They are not capable of living independently
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What are some types of prokaryotes?
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Bacteria and cyanobacteria
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Are they unicellular or multicellular?
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They are unicellular organisms
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Do they have simple or complex structures?
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Simple structures
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Do prokaryotic cells have an outer cell membrane?
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Yes
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Do they have membrane bound organelles?
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They do not contain any membrane bound organelles
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Do they have a nucleus?
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They do not have a nucleus
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Where is their genetic material then?
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It consists of a singular circular molecule of DNA concentrated in an area of the cell called the nucleoid region
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What else may there be dealing with genetic material?
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There may be smaller rings of DNA called plasmids
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How many genes do plasmids have?
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Just a few genes
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How do plasmids replicate?
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They replicate independently of the main chromosomes
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What kinds of genes do they often contain?
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Genes that allow the prokaryote to survive adverse conditions
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Do bacteria have a cell wall?
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Yes
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Do they have a cell membrane?
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Yes
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Do they have cytoplasm?
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Yes
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Where does respiration occur for bacteria?
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At the cell membrane
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All multicellular organisms and all nonbacterial unicellular organisms are composed of what?
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Eukaryotic cells
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What is a typical eukaryotic cell bound by?
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A cell membrane and contains cytoplasm
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What does cytoplasm contain?
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Organelles
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What are organelles suspended in?
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A semi fluid medium called the cytosol
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Where is the genetic material in all this?
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The material consists of linear strands of DNA organized into chromosomes and located within a membrane-enclosed organelle called the nucleus
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What do plants have that animal cells don’t?
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They have a cell wall and chloroplasts
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What do animal cells that plant cells don’t?
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They have centrioles
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Where are centrioles located?
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In the chromosome area
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What is cytosol?
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The fluid component of the cytoplasm
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What does it consist of?
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An aqueous solution containing free proteins, nutrients, and other solutes
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What is the cytoskeleton?
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It is composed of microtubules, microfilaments, and intermediate fibers, and other accessory proteins, is also found in the cytosol
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What do these proteinaceous filaments do?
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They give the cell its shape and anchor the organelles
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What else do they do?
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They function in cell maintenance and aid in intracellular transport
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What does the cell membrane do?
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It surrounds the cell and regulates the passage of materials in both directions
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What does the cell membrane exhibit that deals with the movement of things into and out of the cell?
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It exhibits selective permeability
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What is the fluid mosaic model?
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It is the generally accepted model of what the cell membrane is.
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What does it say?
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It says that the cell membrane consists of a phospholipids bilayer with proteins embedded throughout
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What are phospholipids?
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They have a hydrophilic or polar phosphoric acid region and a hydrophobic nonpolar fatty acid region
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In a lipid bilayer, where is the hydrophilic region found?
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It is found on the exterior surfaces of the membrane
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Where are the hydrophobic regions found?
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They are found in the interior of the membrane
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Where are cholesterol molecules in this?
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They are embedded in the hydrophobic interior
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What do they do?
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They contribute to the membrane’s fluidity
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Where are proteins in this?
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They are interspaced throughout the membrane and may be partially or completely embedded in the bilayer
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What are transport proteins?
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They are membrane spanning molecules that allow certain ions and polar molecules to pass through the lipid bilayer
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What are cell adhesion molecules?
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CAMs are proteins that contribute to cell recognition and adhesion, and are particularly important during development
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What are receptors?
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They are complex proteins or glycoproteins generally imbedded in the membrane with sites that bind to specific molecules in the cell’s external environment
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What is pinocytosis?
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It is how the cell may carry the molecule into the cell
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What is the alternative way the receptor helps out?
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It may signal across the membrane and into the cell via a second messenger
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Is the plasma membrane readily permeable?
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Yes
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What can go through?
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Small nonpolar molecules such as oxygen and small polar molecules such as water
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How can small charged molecules cross?
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They are usually able to cross the plasma membranes through protein channels in the membrane
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How do larger charged molecules cross the membrane?
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They cross with the assistance of carrier proteins
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What is the nucleus?
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It controls the activities of the cell, including cell division
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What is it surrounded by?
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A nuclear membrane or envelope
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Is it double or single layered?
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It is a double membrane that maintains a nuclear environment distinct from that of the cytoplasm
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What are interspersed throughout the nuclear membrane?
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Nuclear pores
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What do they do?
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They allow selective two-way exchange of materials between the nucleus and the cytoplasm
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What does the nucleus contain?
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It contains the DNA
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What is the DNA complexed with?
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Structural proteins called histones
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What do they form together?
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Together they form chromosomes
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What is the nucleolus?
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It is the dense structure in the nucleus where ribosomal RNA synthesis occurs
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What are ribosomes?
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They are sites if protein production and are synthesized by the nucleolus
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What do ribosomes consist of?
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They consist of two subunits, one large and one small
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What is each subunit composed of?
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It is composed of rRNA and proteins
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What are free ribosomes?
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They are ribosomes found in the cytoplasm
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What are bound ribosomes?
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They line the outer membrane of the endoplasmic reticulum
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What is the endoplasmic reticulum?
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It is a network of membrane-enclosed spaced connected at points with the nuclear membrane
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What are ER with ribosomes lining its outer surface known as?
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They are known as rough ER
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What are ER without ribosomes known as?
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They are known as smooth ER
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What is ER involved with generally?
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Generally, ER is involved with the transport of materials throughout the cell
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What types of materials are really used by the ER?
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Materials destined to be secreted from the cell
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What is smooth ER involved in?
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They are involved with lipid synthesis and the detoxification of drugs and poisons
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What is rough ER involved in?
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It is involved in protein synthesis
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Proteins synthesized by the bound ribosomes do what?
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They cross into the cisternae of the RER
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What happens there?
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They undergo chemical modification
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What happens to them then?
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Then they cross into the smooth ER, where they are secreted into cytoplasmic vesicles and are transported to the Golgi apparatus
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What is the Golgi apparatus?
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It consists of a stack of membrane-enclosed sacs
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What does it do?
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It receives vesicles and their contents from smooth ER, modifies them through glycosylation, repackages them into vesicles, and distributes them
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What is the Golgi active in the distribution of?
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Newly synthesized materials to the cell surface
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What are secretory vesicles?
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They are produced by the Golgi, and they release their contents to the cell’s exterior by the process of exocytosis
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What are vesicles and vacuoles?
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They are membrane-bound sacs involved in the transport and storage of materials that are ingested, secreted, processed, or digested by the cell
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Which of the two are bigger?
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Vacuoles are bigger than vesicles
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Which are more likely to be found in plant cells?
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Vacuoles
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What are lysosomes?
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They are membrane-bound vesicles that contain hydrolytic enzymes involved in intracellular digestion
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What is the effective pH level?
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5
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What does this imply?
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It implies they have to be enclosed within the lysosome
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What is the lysosome?
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It is an acidic environment distinct from the neutral pH of the cytosol
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What do they do?
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They fuse with endocytotic vacuoles, thereby breaking down the material ingested by the cell
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What else do lysosomes do?
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They aid in renewing a cell’s own components by breaking down the old ones and releasing their molecular building blocks into the cytosol for reuse
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How can a cell commit suicide?
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It can rupture its lysosome membrane and release its hydrolytic enzymes
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What is this referred to as?
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Autolysis
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What are microbodies?
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They are membrane-bound organelles specialized as containers for metabolic reactions
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What are two important types of microbodies?
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Peroxisomes and glyoxysomes
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What do peroxisomes do?
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They contain oxidative enzymes that catalyze a class of reactions in which hydrogen peroxide is produced by the transfer of hydrogen from a substrate to oxygen.
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What do peroxisomes do to fats?
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They break them down into smaller molecules that can be used for fuel
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What else?
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They can be used in the liver to detoxify compounds harmful to the body, such as alcohol
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What are they used for in seedlings?
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They convert fats into sugars until it is mature enough to produce its own sugars through photosynthesis
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What are mitochondria?
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They are the sites of aerobic respiration within the cell and hence are the suppliers of energy
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What is each mitochondrion bound by?
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They all have an outer and inner phospholipids bilayer membrane
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What does the outer membrane do?
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It is smooth and acts as a sieve, allowing molecules through on the basis of size
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What is the area between the inner and outer membrane known as?
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It is known as the intermembrane space
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What does the inner membrane have inside it?
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It has many convolutions called cristae and a high protein content that includes the proteins of the electron transport chain
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What is the area bounded by the inner membrane?
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It is known as the mitochondrial matrix
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What is the site of?
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It is the site of many of the reactions in cell respiration
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How are mitochondria different from other organelles?
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They are semiautonomous, which means they contain their own DNA which is circular and ribosomes
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What does this enable them to do?
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This enables them to self-replicate by binary fission and produce some of their own proteins
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What were mitochondria believed to be a long time ago?
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They were believed to have been early prokaryotic cells that evolved a symbiotic relationship with the ancestors of eukaryotic cells
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What are chloroplasts?
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They are plastid found only in algal and plant cells
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What do they contain?
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They contain chlorophyll
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What are they the site of?
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Photosynthesis
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What do chloroplasts contain, and what are they similar to?
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They contain their own DNA and ribosomes, and exhibit the same semi autonomy as mitochondria
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What is a cell wall?
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A tough outer cell wall that protects the cell from external stimuli and desiccation
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What has cell walls?
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Plant cells have a cell wall composed of cellulose
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What else has them?
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Fungi have a cell wall composed of chitin and other materials
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Do animals have a cell wall?
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No they do not
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What are centrioles?
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They are a specialized type of microtubule involved in spindle organization during cell division
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What is different about them than other organelles?
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They are not membrane bound
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How many centrioles do animal cells have?
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They usually have a pair of centrioles that are oriented at right angles to each other
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Where do they lie?
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In a region called the centrosome
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Do plant cells have centrioles?
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They do not contain centrioles
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What does the cytoskeleton do?
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It gives the cell mechanical support, maintains its shape, and functions in cell motility
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What is it composed of?
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Microtubules, microfilaments, and intermediate filaments
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What are microtubules?
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They are hollow rods made up of polymerized tubulins that radiate throughout the cell
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What do they do?
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They provide support. They provide a framework for organelle movement within the cell
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What is composed of microtubules?
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Examples are centrioles, which direct the separation of chromosomes during cell division
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What are cilia and flagella?
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They are specialized arrangements of microtubules that extend from certain cells and are involved in cell motility
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What are microfilaments?
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They are solid rods of actin
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What do they do?
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They are involved in cell movement as well as support
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What uses microfilaments?
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Muscle contraction does
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What else do microfilaments do?
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They move materials across the plasma membrane, and in amoeboid movement
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What are intermediate filaments?
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They are a collection of fibers involved in maintenance of cytoskeletal integrity
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How thick are they?
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Their diameters fall between those of microtubules and microfilaments
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What is simple diffusion?
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It is the net movement of dissolved particles down their concentration gradients
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Which direction does it go?
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From a region of higher concentration to a region of lower concentration
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Is this an active or passive process?
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It is a passive process
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What is osmosis?
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It is the simple diffusion of water from a region of lower solute concentration to a region of higher solute concentration
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What happens when the cytoplasm of the cell has a lower solute concentration than that of the extracellular medium?
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The medium is said to be hypertonic to the cell and water will flow out, causing the cell to shrink
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What happens when the cytoplasm of a cell has a higher solute concentration than the extracellular medium?
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The medium is said to be hypotonic to the cell and water will flow in
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What does this cause the cell to do?
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It causes it to swell
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What happens if too much water flows in?
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It causes it to lyse
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What is it called when the solute concentrations inside and outside the cell are equal?
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The cell and medium are said to be isotonic
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What is facilitated diffusion?
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It is the passive transport of dissolved particles down their concentration gradient with the help of carrier molecules
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Does it require energy?
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No
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What is active transport?
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It is the net movement of dissolved particles against their concentration gradient with the help of transport proteins
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Does this require energy?
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Yes
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What is active transport needed for?
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It is required to maintain membrane potentials in specialized cells such as neurons
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What is endocytosis?
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It is a process in which the cell membrane invaginates
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What does this form?
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It forms a vesicle that contain extracellular medium
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What is pinocytosis?
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It is the ingestion of fluids or small particles
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What is phagocytosis?
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It is the engulfing of large particles
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What is exocytosis?
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In exocytosis, a vesicle within the cell fuses with the cell membrane and releases its contents to the outside
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What is an important thing to note about these two things pertaining to the membrane?
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In neither of these does the transported material actually cross the membrane
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What are the four types of tissue?
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Epithelial, connective, nervous, and muscle
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What is epithelial tissue?
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It covers the surfaces of the body and lines the cavities, protecting them against injury, invasion, and desiccation
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What is epithelium involved with?
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Absorption, secretion, and sensation
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What is connective tissue?
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It is involved with body support and other functions
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What are some specialized connective tissues?
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Bone, cartilage, tendons, ligaments, adipose tissue, and blood
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What is nervous tissue?
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It is composed of specialized cells called neurons that are involved with perception, processing, and storage of information concerning internal and external environments
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What is muscle tissue?
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It has great contractile capability and is involved in body movement
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What are the three types of vertebrate muscle?
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Cardiac muscle, skeletal muscle, and smooth muscle
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What are viruses?
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They are unique a cellular structures composed of a nucleic acid enclosed by a protein coat
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What are the sizes of viruses?
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They range from 20 nanometers to 300 nanometers
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How big are prokaryotes?
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1 micrometer to 10 micrometer
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How big are eukaryotic cells?
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They are 10 micrometers to 100 micrometers
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How is viral DNA?
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Either linear or circular, and has been found in four-varieties
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What are the four types?
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Single-stranded DNA, double-stranded DNA, single-stranded RNA, and double-stranded RNA
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What is the protein coat also known as?
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The capsid
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What is it comprised of?
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Many protein subunits and may be enclosed by a membranous envelope
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What are viruses?
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They are obligate intracellular parasites
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What does this mean?
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It means they can express their genes and reproduce only within a living host cell
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Why is that?
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Because they lack the structures necessary for independent activity and reproduction
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What are viruses called that exclusively infect bacteria?
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Bacteriophages
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Does the phage capsid enter the cell?
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No
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