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78 terms

ch 6 - a tour of the cell

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light microscope
visible light is passed through the specimen and then through glass lenses which light is refracted in such a way that the image of the specimen is magnified as it is projected; types: bright field, phase-contrast, fluorescence, confocal
organelles
membrane-enclosed structures within eukaryotic cells
electron microscope
focuses a beam of electrons through the specimen or onto its surface; hundredfold improvement over standard light microscope; SEM and TEM
scanning electron microscope (SEM)
used for detailed study of the topography of a specimen; creates 3D image of cells
transmission electron microscope (TEM)
used to study the internal structure of cells; specimen stained;
cell fractionation
a centrifuge is used to take cells apart and separate major organelles and other sub cellular structures from one another; process is by spinning the test tubes at high speeds
prokaryotic cells
lack a true nucleus and other membrane-enclosed organelles of the eukaryotic cell; much simpler in structure; include bacteria and archaea;
eukaryotic cells
protists, fungi, animals and plants are composed of eukaryotic cells; most DNA is contained in the double membrane bound nucleus
cell components
all cells are bounded by the plasma membrane, have cytosol, chromosomes, and ribosomes
cytosol
inside all cells there is a semifluid, jellylike substance called cytosol in which subcelluar components are suspended
cytoplasm
in eukaryotic cells, this term refers only to the region between the nucleus and the plasma membrane
plasma membrane
selective barrier that allows passage of enough oxygen, nutrients and wastes to service the entire cell
cytoskeleton
reinforces cells shape; functions in cell movement; components are made of protein. includes microfilaments, intermediate filaments, microtubules
ribosomes
complexes that make proteins; free in cytosol or bound to rough ER or nuclear envelope
golgi apparatus
organelle active in synthesis, modification, sorting, and secretion of cell products
peroxisome
organelle with various specialized metabolic functions; produces hydrogen peroxide as a by-product, then converts it to water
mitochondrion
organelle where cellular respiration occurs and most ATP is generated
centrosome
region located near the nucleus where the cells microtubules are initiated; contains a pair of centrioles
flagellum
motility structure present in some animal cells, composed of a cluster of microtubules within an extension of the plasma membrane
endoplasmic reticulum
network of membranous sacs and tubes; active in membrane synthesis and other synthetic and metabolic processes; composed of rough er and smooth er
nucleus
composed of: nuclear envelope, nucleolus and chromatin; contain most of genes(DNA) in eukaryotic cell
nuclear envelope
double membrane enclosing the nucleus; perforated by pores; continuous with ER
nuclear lamina
a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope
nucleolus
nonmembranous structure involved in production of ribosomes; a nucleus has one or more nucleoli; synthesizes rRNA from instructions in DNA
chromosome
structures of DNA that carry the genetic information
chromatin
material consisting of DNA and proteins; visible in a dividing cell as individual condensed chromosomes
in animal but not plant cells
lysosomes, centrosomes with centrioles, and flagella
in plant but not animal cells
chloroplasts, central vacuole, cell wall and plasmodesmata
cell wall
outer layer that maintains cells shape and protects cell from mechanical damage; made of cellulose, other polysaccharides and protein
plasmodesmata
cytoplasmic channels through cell walls that connect the cytoplasms of adjacent cells
chloroplast
photosynthetic organelle; converts energy of sunlight to chemical energy stored in sugar molecules
endomembrane system
composed of: nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, various kinds of vesicles and vacuoles and plasma membrane; membranes of this system are related either through direct physical continuity or by the transfer of membrane segments as tiny vesicles
functions of endomembrane system
synthesis of proteins, transport of proteins into membranes and organelles or out of the cell, metabolism and movement of lipids, and detoxification of poisons
smooth ER
enzymes of smooth ER are important in the synthesis of lipids, detoxify drugs and poisons(esp. in liver cells), stores calcium ions
rough ER
studded with ribosomes; membrane factory for the cell; makes membrane phospholipids
glycoproteins
proteins that have carbohydrates covalently bonded to them
transport vesicles
vesicles in transit from one part of the cell to another
golgi apparatus
"warehouse" for receiving, sorting, shipping, and even some manufacturing; consist of stacks of flattened sacs (cisternae) not physically connected
"cis" face of golgi apparatus
"receiving department" of golgi. located near ER
"trans" face of golgi apparatus
"dispatches vesicles"; gives rise to vesicles that pinch off and travel to other sites
lysosome
digestive organelle where macromolecules are hydrolyzed; digest materials taken into the cell
phagocytosis
carried out by lysosomes: engulfing smaller organisms or food particles; macrophages (white blood cells that engulfs and destroy bacteria)
food vacuoles
formed by phagocytosis
contractile vacuoles
pump excess water out of the cell, thereby maintaining a suitable concentration of ions and molecules inside the cell
central vacuole
develops by the coalescence of smaller vacuoles; plays a major role in growth of cells by enabling the cell to become larger with a minimal investment in new cytoplasm
mitochondria
sites of cellular respiration, the metabolic process that uses oxygen to generate ATP by extracting energy from sugars, fats, and other fuels
chloroplasts
membranes divide space into 3 compartments: inter membrane space, stroma and thylakoid space. found in plants and algae; sites of photosynthesis; convert solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from carbon dioxide and water
endosymbiont theory
theory states that an early ancestor of eukaryotic cells engulfed an oxygen-using non photosynthetic prokaryotic cell. eventually, the engulfed cell formed a relationship with the host cell in which it was enclosed, becoming an endosymbiont; over the course of evolution, the host cell and its endosymbiont merged into a single organism, a eukaryotic cell with a mitochondrion
cristae
foldings in mitochondrion
mitrochrondrial matrix
enclosed by the inner membrane
thylakoids
in chloroplasts; membranous system in the form of flattened, interconnected sacs
granum
stacks of thylakoids
stroma
fluid outside the thylakoids that contains the chloroplast DNA and ribosomes as well as many enzymes
plastids
family of closely related plant organelles; amyloplast: a colorless organelle that stores starch(amylose), particularly in roots and tubers; another is the chromoplast, which has pigments that give fruits and flowers their orange and yellow hues
peroxisome
a specialized metabolic compartment bounded by a single membrane; contain enzymes that removes hydrogen atoms from various substrates and transfer them to oxygen producing hydrogen peroxide as a by-product.
cytoskeleton
network of fibers extending throughout the cytoplasm; composed of 3 types of molecular structures: microtubules, microfilaments, and intermediate filaments
microtubules
hollow tubes; functions: maintenance of cell shape, guide organelle movement, and separate chromosomes in dividing cells
microfilaments
two intertwined strands of actin; functions: maintenance of cell shape, changes in cell shape, muscle contraction, cytoplasmic streaming, cell motility, and cell division
intermediate filaments
fibrous proteins supercoiled into thicker cables; functions: maintenance of cell shape, anchorage of nucleus and certain other organelles, and formation of nuclear lamina
centrioles
9 sets of pairs of centrioles located within centrosome
basal body
structurally similar to a centriole; anchors a microtubule assembly of a cilium or flagellum
dyneins
In cilia and flagella, a large motor protein extending from one microtubule doublet to the adjacent doublet. ATP hydrolysis drives changes in dynein shape that lead to bending of cilia and flagella.
actin
a globular protein
cortex
outer cytoplasmic layer of a cell semisolid consistency
myosin
A type of motor protein that associates into filaments that interact with actin filaments to cause cell contraction.
cytoplasmic streaming
a circular flow of cytoplasm within cells that speeds the distribution of materials within the cell
primary cell well
a young plant first secretes a realtively thin and flexible wall
middle lamella
a thin layer rich in sticky polysaccharides called pectins
secondary cell wall
between plasma membrane and primary cell wall; has a strong and durable matrix that affords the cell protection and support
extracellular matrix (ECM)
The meshwork surrounding animal cells, consisting of glycoproteins, polysaccharides, and proteoglycans synthesized and secreted by the cells.
collagen
forms strong fibers outside cells; accounts for 40% of total protein in human body
proteoglycans
A large molecule consisting of a small core protein with many carbohydrate chains attached, found in the extracellular matrix of animal cells. A proteoglycan may consist of up to 95% carbohydrate.
fibronectin
An extracellular glycoprotein secreted by animal cells that helps them attach to the extracellular matrix.
integrins
In animal cells, a transmembrane receptor protein with two subunits that interconnects the extracellular matrix and the cytoskeleton.
plasmodesmata
An open channel through the cell wall that connects the cytoplasm of adjacent plant cells, allowing water, small solutes, and some larger molecules to pass between the cells.
tight junctions
prevent fluid from moving across a layer of cells
desmosomes
"anchoring junctions" function like rivets, fastening ells together in strong sheets. attach muscle cells to each other in a muscle.
gap junctions
"communicating junctions" provide cytoplasmic channels from one cell to an adjacent cell; necessary for cell communication