Chapter 3 Cells the Living Units

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4 concepts of cell theory
1. cells are the basic structural and functional units of life
2. the activity of an organism depends on the activites of its cells
3. the biochemical activities of a cell are dictated by their organelles
4. the continuity of life has a cellular basis
4 characteristics of cells
1. cells vary greatly in their size, shape, and function.
2. all cells are composed primarily of carbon, hydrogen, nitrogen and oxygen.
3. all cells ahve the same basic parts and some common functions.
4. a generalized human cell contains the plasma membrane , the cytoplasm and the nucleus.
why is the plasma membrane said to have a mosaic structure
composed of a double layer of phospho lipids embedded with a mosaic of small amounts of cholesterol and proteins.
describe the phospholipid bilayer
two layers of phospholipids lying tail to tail with their polar heads exposed to water inside and outside of the cell
head of a phospholipid composed of
phosphate group and is hydrophilic
tail is made up of
fatty acids and is hydrophobig
are the molecules moving?
yes
what are the two types of lipids in the plasma membrane
glycolipids and lipid rafts
glycolipids
phospholipids with attached sugar groups are found only in the outer membrane. Membrane carbohydrates are usually short, branched chains of fewer than 15 sugar units.
lipid rafts
cholesterol-enriched region in cell membranes. found only in the outer membrane, and are assemblies of saturated phopholipids associated with ceratin other lipids and lots of cholesterol. they are assumed to function in cell signaling
integral proteins
firmly inserted into plasma membrane. most are transmembrane proteins that span the entire width of the membrane and are involved with transport as channels or carriers.
peripheral prtoeins
not embedded in the plasma membrane, but attach tto integral proteins or to phospholipids. peripheral proteins may function as enzymes or in mechanical functions of the cell.
glycocalyx
fuzzy, sticky, carbohydate-rich area surrounding the cell. glycoproteins and glycolipids are a part of the glycocalyx
microvilli
fingerlike extensions of the plasma membrane that increase the surface area of the cell- found in the cells involved in secretion/absorption
membrane junctions
tight junctions, desmosomes, gap junctions
tight junctions
membranes of neighboring cells are very tightly pressed against each other, bound together by specific proteins. forming continuous seals around the cells.
example of tight junction
in the small intestine, these junctions prevent digestive inzymbes from seeping into the bloddstream
desmosomes
anchoring junctions that prevent cells subjected to mechanical stress from being pulled apart. structurally these junction are plaques inside the cells to the plaques on the cells; opposite sides, thus forming an internal system of strong wires
gap junctions
communication junction between cells that allows the passage of water and small molecules between adjacent cells. chemical molecules, such as nutrients or ions can pass directly form one cell to another through them
where are gap junctions commonly seen
heart and between embryonic cells
what do gap junctions mainly consist of
special membrane protins that surround a pore through which ions sugars amnino acids and other small molecules may pass.
the plasma membrane= (blank) membrane
[selectively] it regulates how substances pass into and out of the cell
passive processes
membrane transport that do no tuse energy and move substances down a concentration gradient
diffusion
process in which substances move directly through plasma membrane from area of higher concentration to lower concentration, in attempt to reach equilibrium
what happens after equilibrium is reached
molecules still move after equilibrium
facilitated diffusion
substances are moved through the plasma membrane by binding to proteins carriers in the membrane or by moving through channels using channel proteins
example of facilitated difffusion
aquaporins are channel proteins that allow the passage of water molecules
osmosis
diffusion of water through a selectively permeable membrane, water moves towards higher concentration
filtration
pressure driven process that forces water and solutes though a membrane or capillary wall
active transport uses what
solute pumps to move substances against a concentration gradient
two kinds of active transport?
primary and secondary active transport
primary active transport
hydrolysis of ATP results in the phosphorylation of the transport protein, a step that causes the protein to change ints conformation in such a manner that it "pumps" the bound solute across the membrane
example of primary active tran.
sodium potassium pump
secondary active transport
singly ATP-power pump such as the Na-K pump can indirectly drive the secondary active transport of several other solutes.
in secondary act. trans. why is sodium moved across the membrane
pump stores energy in ion gradient. as sodium moves back into the cell with the help of a carrier protein (facilitated diffusion), othe rsubstances are dragged along or co transported by a common carrier protein
example of secondary transport
some sugars, amino acids, and ions are co transported in this way into cells lining the small intestine
vesicular transport
means by which large particles, macromolecules and fluids are transported across the plasma membrane or within the cell
exocytosis
process used to move substances from inside the cell to the extra cellular environment
endocytosis
process used to move substances form the extra cellular environment to the inside of the cell.
phagocytosis
cell engulfs a particle by wrapping pseudopodia around it and packageing it within a membrane-enclosedd sac large enough to be classified as a vacuole. the particle is digested after vacuol fusies with a lysosome containing hydrolytic enzymes
pinocytosis
cell "gulps" droplets of extracellular fluid into tiny vesicle. it is not hte fluid itself that is needed by the cell, but the molecules dissolved in the droplet. because and and all included solutes are taken into the cell, pinocytosis is nonspecific in the substances it transports.
receptor mediated endocytosis
enables the cell to acquire bulk quantities of specific substances even though those substances may not be very concentrated in the extracellular fluid. embedded in the membrane are proteins with specific receptor sites exposed to the exracellular fluid. the receptor proteins are usually already clustered in regions of the membrane called coated pits which are lined on their cytoplasimic side by a fuzzy layer of coat proteins. when binding occurs, the coated pit forms a vesicle containing the ligand molecules. after the ingested vesicle is liberated from the vesicle, the receptors are recycled to the plasma membrane by the same vesicle.
ligand
extracellular substances
coated pit/pt/pl (couldnt read the small print)
receptor proteins that are usually already clustered in regions of this membrane
cytoplasm
cellular material between cell membrane and nucleus. site of most cellular activity
what are the 3 major elements of the cytoplasm
cytosol, organelles, inclusions
cytosol
unstructured gel like part of cytoplasm that contains biological molecules in solution
organelles
highly structured functional structures within cell
inclusions
stored nutrients, crystals of various types, sececretory granules, and waste products in the cell
the cytoplasmic organelles
mitochondria, ribosomes, endoplasmic reticulum, golgi apparatus, lysosomes, endomembrane system, peroxisomes, cytoskeleton, centrosome and centrioles, cellular extensions, nucleus, nuclear envelope, nucleoli, chromatin
mitochondria
sausage shpaed membranous organelle that are power plants of the cell. they are the sites of cellular respiration producing most of its ATP
4 major sections of mitochondria
outer memrane, intermembrane space, inner membrane, matrix
outer membrane
smooth membrane
intermembrane space
space between inner and outer membrane
inner membane
compartmentalized into numerous cristae, chich expand the surface area of the inner mitochondrial membrane enhancing its ability to generate ATP
Matrix
enclosed by inner membrane and contains the mitochondrial DNA and ribosomes
ribosomes
small staining granules consisting of protein and ribosomal RNA
site of proteins synthesis
may be bound to ER or float freely
examples of cells with high number of ribosomes
human pancreatic cell
ER
extensive system of tubules and cisternae that extend through out the cytosol. 2 types that are somehow connected but different functions
cisternae
flattened fluid filled sacs that are part of ER
rough ER
produces membranes requires by cells, has ribosomes that manufacture proteins
smooth ER
stores calcium ions
detoxifies drugs and poisons
catalyses many reactions
golgi apparatus
series of stacked, flattened membranous sacs associated with groups of membranous vesicles.
modify, concentrate and packages proteins and lipids made in rough ER
lysosmes
roughly spherical bodies bounded by a single membrane
made by golgi, but with digestive enzymes
function best in acidic environments (pH=5)
contain digestive enzymes and can digest almost any kind of biological molecules.
endomembrane system
functions together to produce, store, and export biological molecules as well as degrade potentially harmful substances.
components of endomembrane system
plasma membrane, ER, peroxisomes, golgi, secretory vesicles, lysosomes, nuclear membrane
peroxisomes compare and contrast
same shape and single membraned like lysosomes also resemble lysosomes by its enzyme filling
difference: bud off ER not Golgi
peroxisomes
membranous sacs containing enzymes such as oxidases and catalases which are used to detoxify harmful substancs such as alcohol, formaldehyde, and free radicals
cytoskeleton
consists of a series of fibers/rods running through cytosol and responsible for th maintenance of cell shape, cell locomotion, movemnt of various elements in cytoplasm, integration of major cytoplasmic organization and movement, and adhesion of a cell to a surface or to other cells.
3 main types of cytoskeleton
microtubules, microfilaments, intermediate filiaments
centrosome
region near the nucleus in which a group of microtubules are anchored. there are a pair of centrioles
microtubule organizing center and forms mitotic spindle during cell division
centrioles
about 250 nm in diameter
barrel shaped
composed of 9 sets of 3 microtubules arraged in a ring. form the cilia and flagella
cellular extensions
have a core of microtubules enclosed in an extension of the plasma membrane. have a circular arrangement of 9 doublets of microtubules attached to a central pair. referred to as the 9+2 pattern. found in eukaryotic flagella and cilia
cilia
whiplike, motile cellular extensions on the exposed surfaces of some cells
flagella
long cellular projections that move the cell through the environment
differences between cilia and flagella (size, number, occurrence)
flagella are long in length
cilia occur in large numbers on surface, flagella are one or two
cilia are found IN THE LINING OF THE WINDPIPE nad it sweeps mucus containing trapped depbris out. in lining of OVIDUCTS, it helps move an egg toward the uterus
flagella found in the sperms of animals
nucleus
control center of the cell and contains the cellular DNA. usually occurs as one per cell. present in all cells but red blood cells. is larger than the cytoplasmic organelles; has three regions and protein containing subcompartments
nuclear envelope
double membrane barrier around nucleus.
outer membrane is continuous with RER and has ribosomes.
inner membrane lined with shape maintaining protein filaments (nuclear lamina)
nuclear pores penetrate areas where the membranes of the nuclear enveope fuse
pore complex lines each nuclear pore and regulates passage of large particles
nucleoli
dark staining spherical bodies within nucleus
typically 1 or 2 per nucleus
sites of assembly of ribosomal subunits
chromatin
roughly half DNA and half histone proteins. nucleosomes are te fundamental unit of chromatic, consisting of cluster sof 8 histone proteins connected by a DNA molecule. during cell division, condenses into chromatids
3 classes of extracellular fluids
body fluids, cellular secretions, extracellular matrix
body fluids
consist of mainly of interstitial fluid, blood plasma, cerebrospinal fluid and are important to transport and solute dissolution
cellular secretions
include substancs aiding in digestion (gastric or intestinal) or functioning as lubrication ( saliva and mucus)
extracellular Matrix
jellylike substance consisting of proteins and polysaccharides. abundant in connective tissue
2 main periods of cell cycle
interphase and cell division
interphase
period from cell formation cell division
3 subphases of interphase
g1, s, and g2
g1 phase
synthesizing proteins and actively growing
s phase
dna is replicated
g2 phase
enzymes and other proteins are synthesized and distributed throughout the cell. DNA replication takes place when DNA helix uncoils.
KNOW DNA REPLICATION
KNOW DNA REPLICATION
mitosis
process of nuclear divion in which cells contain all genes
meiosis
process of nuclear division found only in egg and sperm cells in which the cells have half the genes found in other body cells
cytokinesis
process of dividing the cytoplasm
KNOW MITOSIS PHASES
KNOW MITOSIS PHASES
each gene is a segment that carries info for how many polypeptide chains
1
KNOW PROTEIN SYNTHESIS
KNOW PROTEIN SYNTHESIS