prokaryotic cell
a cell with no nucleus or other internal membranes. prokaryotes have just ribosomes, cytoplasm, etc. all bacteria are prokaryotes. 1.Organelles: cytoplasm, ribosomes, plasma membrane, capsule, cell wall, pili, nucleoid2.no internal membranes3.circular, naked DNA4.ribosomes are very small5.metabolism is anaerobic or aerobic6.cytoskeleton absent7.mainly unicellular8.cells are very small (1-10 micrometers)
theory of endosymbosis
theory that eakaryotic cells emerged when mitochondria and chloroplasts, once free-living prokaryotes, took up permanent residence inside other larger cells, about one and a half billion years ago.
eukaryotic cell
a cell with internal membranes that compartmentalized the cell and led to the evolution of multicelled organisms1.Organelles (see plant and animal cells)2.contain distinct organelles3.DNA wrapped with histone proteins into chromosomes4.ribosomes are larger than in prokaryotes5.metabolism is aerobic6.cytoskeleton present7.mainly multicellular with differentiation of cell types8.cells 10-100 micrometers
schleiden and schwann
determined that all organisms are composed of cells in 1838
virchow
determined that all cells arise from preexisting cells in 1855
average cell diameter
between 8 and 100 micrometers
cell theory
1.all living things are composed of cells2.cells are the basic unit of all organisms3.all cells arise from preexisting cells
microscope
a tool for study cells by magnifying images
resolution
a microscope term that refers to the clarity of the image produced
high magnification
the ability to magnify something to a large percent of its actual size
high resolution
the ability to magnify something into a very clear image
antoine van leeuwenhoek
the man who developed the first microscope in the 1600s
robert hooke
the man who developed a microscope that enabled him to study and name cells in cork
light microscope
micrscopes that use light passing through a living or dead specimen to form an image.
electron microscopes
use electrons passing through a specimen to form an image. these have superior resolving and magnifying power, but can only view dead things
transmission electron microscopes
a type of electron microscope that is usually used for studying the interior of cells. images taken with the T.E.M. appear flat and 2D. To prepare tissue, it must first be cut into very small pieces, then exposed to a fixative like gluteraldehyde, which stops all biochemical activity. The tissue is then dehydrated, embedded in a polymer, cured overnight, and sliced on an ultramicrotome. The process can take several days
scanning electron microscopes
a type of electron microscope that is usually used for studying the surface of cells and the images have a 3D appearance. specimens are coated with a heavy metal and placed directly in the microscope for observing. the process takes hours, but specimens are not alive.
phase-contrast microscopes
microscopes used to examine unstained, living cells, such as cells growing in a tissue culture
cell fractioning
a non-microscopic way to study cells that uses an ultra centrifuge to spin liquid samples at high speed, separating them into layers based on differences in density. tissue or cells are first mashed up in a blender to form a homogenate and then spun in a centrifuge. the densest particles settle to the bottom of the centrifuge tube. the supernantant, which is the liquid layer above the pellet, can be poured off and respun. This is repeated until the desired layer is isolated, and the layer is all one organelle
free fracture and freeze-etching
A technique for studying cells that involves multistep techniques used to prepare a detailed cast of the membrane. The tissue is then digested away, leaving only the cast of the tissue. This cast is then examined under an electron microscope.
tissue culture
a technique used to study the properties of specific cells in the laboratory. Cell lines can be grown in culture for years, provided great care is taken with them. While the cells are growing, they can be studied under the phase-contrast microscope without staining.
different types of cells and their shapes
nerve cell-long and spindlycolumnar epithelial cell with microvilli-shaped like a footwhite blood cell-circular with open interioradipose (fat) cell-circular with full interiorsmooth muscle cell-long and flexible
organelles in a plant cell
chloroplast, vacuole, plasma membrane, cell wall, cytoplasm, nucleoli, nucleus, nuclear membrane, nucleolus, plasmodesma, plastids, leucoplast, golgi body, ribosomes, rough and smooth ER, mitochondria, cytoskeleton, peroxisomes
organelles in an animal cell
cytoplasm, golgi body, rough ER, smooth ER, ribosomes, vacuole, mitochondria, centrioles, nuclear membrane, nucleus, nucleolus, lysosome, cell membrane, peroxisomes
nucleus
a membrane-bound eukaryotic organelle that contains chromosomes wrapped with special proteis into a chromatin network. it is surrounded by a selectively permeable nuclear membrane/envelope that contains pores to allow for the transport of molecules, like mRNA, which are too large to diffuse directly through the envelope
nucleolos
the organelle located inside the nucleus that synthesize ribosomes and are a tangle of chromatin andn unfinished ribosome precursors.
ribsomes
these are the site of protein synthesis, and are found free in the cytoplasm or in the rough ER
rough endoplasmic reticulum
a membranous system of channels and flattened sacs that traverse the cytoplasm. It is the site of protein synthesis (with its ribosomes)
smooth endoplasmic reticulum
a membranous system of channels and flattened sacs that traverse the cytoplasm. it1 assists in the synthesis of steroid hormones and other lipids2 connects rough ER to the Golgi body3 carries out various detoxification processes
golgi apparatus
this lies near the nucleus and consists of flattened membranous sacs stacked next to one another and surrounded by vesicles. They package substances produced in the rough ER and secrrete them to other cell parts or to the cell surface for export
lysosomes
these are sacs of hydrolytic (digestive) enzymes surrounded bya single membrane. They are the principal site of intracellular digestion. The cell uses the lysosome to recycle cell parts. lysosomes can also asist in apoptosis, particularly in developing organisms with toes, fingers, etc.
apoptosis
programmed destruction of cells
peroxisomes
organelles that contain catalase. they also detoxify alcohol in liver cells
catalase
an enzyme that converts hydrogen peroxide, a wate product of respiration in the cell, into water with the release of oxygen atoms
mitochondria
these are the sites of cellular respiration. a very active cell could have up to 2500 of them. mitochondria have an outer double membrane and an inner series of membranes called cristae. They contain their own DNA
vacuoles
single, membrane-bound structures for storage
vesicles
tiny vacuoles usually found in plants
contractile vacuoles
storage organelles that pump out excess water
plastides
these have a double membrane and are found in plant and algae. there are 3 types:1.chloroplasts2.leucoplasts3.chromoplasts
chloroplasts
the sites of photosynthesis. The have a double outer membrane as well as an inner one that forms a series of strucutres called grana (stacks of thylakoids) in a sea of stroma. chloroplasts contain their own DNA
leucoplasts
these organelles store starch and are found in roots like turnips or in tubers like the potato.
chromoplasts
these organelles store carotenoid pigments and are responsible for the red-orange-yellow color of carrots, tomatoes and daffodils
cytoskeleton
an organelle that is a complex network of protein filaments that extends throughout the cytoplams and gives the cell its shape, enables it to move, and anchors the organelles to the plasma membrane. the cytoskeleton includes microtubules and microfilaments
microtubules
hollow tubes made of the protein tubulin that make up the cilia, flagella, and spindle fibers
cilia and flagella
help the cell move and have 9 microtubules centered around 2 microtubules
spindle fibers
components of the cytoskeleton that help separate chromosomes durign mitosis and meiosis and consist of microtubules organized into 9 triplets with no microtubules in the center
microfilaments (actin filaments)
help support the shape of the cell they enable:1. animal cells to form a cleavage furrow durign cell division2.ameobas to move by sending out pseudopods3, skeletal muscle to contract as they slide along myosin filaments
pseudopods
temporary bulges of the cell
cetrioles
nonmembranous structures that lie outside the nuclear membranes. they organize spindle fibers and give rise to the spindle apparatus required for cell division. 2 centrioles oriented at right angles to each other make up one centrosome and consist of 9 triplet microtubules (like spindle fibures)
centrosomes (in animals)
nonmembranous structures that lie outside the nuclear membranes. they organize spindle fibers and give rise to the spindle apparatus required for cell division.
microtubule organizing centers (in plants)
nonmembranous structures that lie outside the nuclear membranes. they organize spindle fibers and give rise to the spindle apparatus required for cell division.
cell wall
made of cellulose in plant and algae. made of chitin in fungi. made of poymers in prokaryotes. it protects the cell and provides structure and function, allowing for turgid pressure in plants and algae.
primary cell wall
is immediately outside the plasma membrane
secondary cell well
produced by some cells and placed outside of the primary cell wall
middle lamella
a thin gluey layer formed between 2 new cells when a plant cell devides
cell/plasma membrane
a selectively permeable membrane that regulates the steady traffic that enters and leaves the cell
S.J. Singer
developed the fluid mosaic model in 1972 to eplain the cell membrane as a collage of phospholipids, proteins, and steroids
phospholipid bilayer
a layer of phospholipids that make up the cell membrane and consist of hydrophyllic and phobic areas. it has embedded proteins throughout its layers. the hydrophobic lipids face inwards and the hydrophilic phosphate faces outwards.
amphipathic
adj. having both a hydrophobic and hydrophilic region
integral proteins
components of the plasma membrane that have nonpolar regions that completely span the hydrophobic interior of the membrane, allowing for facilitated diffusion
peripheral proteins
are loosely bound to the surface of the membrane
cholosterole molecules
are embedded in the interior of the bilayer to stabilize the membrane. the average membrane has the consistency of olive oil and is about 40% lipid and 60% protein.
glococalyx
carbohydrates that hang off the cell membrane and assist in cell-to-cell reconition
protein functions in the plasma membrane
1.transport: act as cannels, pumps, carriers, and electron transport chains2.enzymes3. receptors-for hormones, neurotransmiters, receptor-mediated endocytosis, and for cells of the immune system4.cell to cell attachments
adenylate cyclase
a membrane-bound enzyme located within the cell membrane that synthesizes cyclic AMP from ATP
desmosomes
proteins that serve as anchors for filaments and rivet cells together
transport
the movement of substances into and out of a cecll
passive transport
the movement of molecules down a concentration gradient from a region of high concentration to a region of low concentration until equilibrium is reached
active transport
the movement of substances into and out of a cell through the use of energy (ATP)
simple diffusion
the dispersal of particles without the use of protein channels, etc.
facilitated diffusion
diffusion that requires protein channels to passively transport specific substances across the membrane
hydrophilic protein channel
a protein that assists with facilitated diffusion by provided a tunnel through the hydrophobic portion of the cell membrane and allowing polar things like water to flow into and out of the cell.
countercurrent exchange
a special case of simple diffusion in which the flow of adjacent fluids in opposite directions maximizes the rate of simple diffusion. ex. fish gills
solvent
the substance that does the dissolving
solute
the substance that dissolves
hypertonic
having a greater concentration of solute than another solution
hypotonic
having lesser concentration of solute that another solution
isotonic
2 solutions containing equal concentration of solutes
osmotic potential
the tendency of water to move across a permeable membrane into a solution
water potential
a combination of solute concentration and pressure that measures the tendency of water to move away. it can be negative.
turgor pressure
the pressure that a vacuole filled with water exerts on the cell wall that keeps the plants crisp
plasmolysis
when a plant is dehydrated and not turgid
aquaporins
special water channel proteins that facilitate the diffusion of massive amounts of water across a cell membrane. The channels do not affect the water potential gradient or the direction of water flow, but rather the rate at which water diffuses down its natural gradient. Aquaporins can also function as gated channels
gated channels
A protein channel in a cell membrane that opens or closes in response to a particular stimulus (such as turgor pressure)
pumps/carriers
carry particles across the membrane by active transport
plastoquinone
a type of pump in the thylakoid membrane of chloroplasts that is a mobile electron carrier
sodium-potassium pump
a pump that pumps Na+ and K+ ions across a nerve membrane against their gradients to return the nerve to its resting state.
electron transport chain
a carrier located in the mitochondria that consists of proteins that pump protons across the cristae membrane
exocytosis
a process of expelling things from inside the cell by forming a vesicle around the substance and releasing it from the cell. it occurs in nerve cells as vesicles release neurotransmitters into a synapse
pinocytosis
cell drinking, encloses liquids in a vesicle that then fuses with the cell
phagocytosis
the engulfing of large particles of small cells by pseudopods. The cell membrane wraps around the particle and encloses it into a vacuole. This is the way human white blood cells engulf bacteria and the way amoebas gain nutrition
receptor-mediated endocytosis
enables the cell to take up large quantities of very specific substances. It is a process by which extracellular substances bind to receptors on the cell membrane. Once the ligand binds to the receptors, endocytosis begins. The receptors carry the ligand migrate and cluster along the membrane, turn inward, and become a coated vesicle that enters the cell. This is the way cells take in cholesterol from the blood.
bulk flow
a general term for the overall movement of a fluid in one direction in an organism. ex. blood (due to blood pressure of pumping heart) and sap (due to active transport in phloem)
source
where a substance originates during bulk flow
sink
where the substance moved using bulk flow is used
cell communication
cells communicate using cell junctions, signal transduction pathways, and cell-to-cell recognition
cell junction types
1.tight2.desmosomes3.gap4.plasmodesmata
tight junctions
belts around the epithelial cells that line organs and serve as a barrier to prevent leakage into or out of those organs. example: in the urinary bladder, they prevent urine from leaking out of the bladder into the surrounding body cavity
desmosomes
these are found in many tissues and have been compared to spot welds that rivet cells together. they consist of clusters of cytoskeletal filaments from adjacent cells that are looped together. they occur in tissues that are subjected to severe mechanical stress, such as skin epithelium or the neck of the uterus.
gap junctions
these permit the passage of materials directly from the cytoplasm of one cell to the cytoplasm of an adjacent cell. ex. in the heart, the flow of ions through the gap junctions coordinates the contractions of the cardiac cells. (think pacemaker) these are in animals
plasmodesmata
like gap junctions but for plants
signal transduction pathway
these rely on plasma membrane proteins in a multi step process in which a small number of extracellular molecules produce a major cellular response. includes 3 stages.1.reception-the signal molecuel (commonly a protein that does not enter the cell) binds to a specific receptor on the cell surface, causing the receptor molecule to undergo a change in conformation.2.transduction-a change in the signal form, where the receptor relays a message to a secondary messenger.3.response-an action within the cell triggered by a secondary messenger such as cAMP
cell-to-cell recognition
the cell's ability to distinguish one type of neighboring cell from another
contact inhibition
the normal trait of cells to stop dividing when they become too crowded