Chap 6-7
Studying cells
Microscopy
Light microscope
Phase contrast
Differential interference constrast
Fluorescence
confocal- best resolution of these
Electron Microscope
scanning electron microscope- sees in 3D
transmission electron microscopy-2D-see a cross section
Brightfield (stained and unstained)-what we have in lab
cell fractionation
takes cells apart and separates organelles and other subcellular structures
equipment used--centrifuge
bigger things centrifuge out first 1-nuclei and cellular debris 2 mitochondria and chloroplasts 3 microsomes (pieces of plasma membranes and internal membranes) 4 ribosomes
kills the specimen
does not always kill the specimen
Prokaryotic cell
all have
nucleoid
NOT membrane bound
where DNA is located
ribosomes- synthesize protein
cytoplasm
some have
fimbriae- short hairlike appendage that helps to adhere to a substrate
generally smaller than eukaryotic cells
plasma membrane-
cell wall- rigid structure outside the plasma membrane
glycocalyx- outer coating consisting of a capsule or slime layer
flagella- locomotion
Eukaryotic cell
Size
theoretical upper limit to size of cell
high surface to volume ratio facilitates exchange of materials between cell and the environment
more cells as opposed to bigger cells
Nucleus
contains most of the genes
nuclear envelope
encloses the nuclues
double membrane
perforated by pore structures
nuclear lamina
lines the inside of the nuclear envelope
made of an array of protein filaments (intermediate filaments in animal cells)
DNA
chromosomes- tightly wound DNA- formed during mitosis
chromatin- normal state of DNA-- unraveled
chromatid- sister chromatids are the duplicated DNA
outer layer is connected to the rough ER
Ribosomes
not technically an organelle-no membrane
made of RNA
carry out protein synthesis
can be bound or free
bound- attached to rough ER-make proteins headed for insertion into membranes
nucleolus- ribosomes and ribosomal RNA are made
free- loose in the cytosol- makes proteins that function in the cytosol ie enzymes
Large and small subunit
Endomembrane system
nuclear envelope--see nucleus
Endoplasmic reticulum
Golgi apparatus
lysosomes
vesicles
plasma membrane
Functions-- synthesis of proteins, transport of proteins, metabolism and movement of lipids, detoxification of poisons
vacuoles
smooth ER
no bound ribosomes
makes lipids- oils, steriods, phospholipids etc
detoxify drugs and poisons
membranous system of tubuoles and sacs called cisternae--cisternal space or ER lumen is the space inside the membrane
rough ER
has bound ribosomes and is connected to the nuclear envelope
bound ribosomes synthesize proteins
can attach carbohydrates to proteins to make glycoproteins
makes membrane and membrane proteins
vesicles bud off of the transitional er
transport vesicles
can bud off the transitional ER and fuse with the Golgi
Receiving and shipping center! Sorts the proteins that a cell makes
especially extensive in cells that specialize in secretion
looks like a stack of pancakes
cis face--receiving trans face--shipping
does some finishing touches on some products
golgi receives and sends off vesicles containing products destined for all parts of cell
sac of hydrolytic enzymes used to digest macromolecules
carry out intracellular digestion
breaks down food (good or bad) or intracellular materials and recycles what can be recycled
food vacuole
formed by phagocytosis
small and found mostly in animals
contractile
found in unicellular eukaryotes
pumps excess water out of the cell to maintain the correct concentration of ions in and out of the cell
central vacuole
found in plants
collects water
trash can or recycling bin of the cell
Energy organelles
Mitochondria
has double membrane
outer membrane is smooth
inner membrane has lots of infoldings called cristae--lots of surface area
matrix is inside the inner membrane--plasmids and ribosomes found here
where cellular respiration takes place
chloroplast
found in plants
structure
double membrane
stack of discs called granum
each disk is a thylakoid
stroma- fluid outside the thylakoids-- contains ribosomes and DNA (plasmids)
convert light energy to chemical energy
Peroxisome
single membrane- no phospholipid bilayer
break down lipids
detoxifies
Cytoskeleton-mostly support and motility
Microtubules
hollow tube made of dimers
largest of the fibers
in all eukaryotic cells
functions
cell shape and support (girders)
cell motility
grow out from a centrosome
compression resisting
Microfilaments
Intertwined strands of actin (actin is a spherical protein)
thinnest
in all eukaryotic cells
functions
cell shape- tension bearing
muscle contraction
cytoplasmic streaming
cell motility (amoeboid movement)
the cleavage furrow in animal cell division
Intermediate Filaments
long fibrous proteins coiled into cables (keratin)
only in some animals
functions
maintenance of cell shape (tension bearing)
anchors the nucleus and some other organelles
make up the nuclear lamina
serve as tracks for organelles to move on
centrosomes has 2 centrioles
centriole is composed of 9 sets of triplet microtubules arranged in a ring
sacs made of membrane
cilia and flagella
lots and lots of cilia usually only one or a small number of flagella
cilia moves with a power and recovery stroke--flagella moves with undulating motion like the tail of a fish
a group of microtubules sheathed in an extension of the plasma membrane
9 doublets of microtubules in a ring with 2 microtubules in the center (9+2)---non motile have a 9+0
dyenin proteins connect the microtubules in the outer ring and are responsible for the movement--have "feet" that "walk" along the microtubule
Extracellular components
cell wall
found in plant cells
maintains shape
protection
prevents excess water uptake
thicker than the plasma membrane
made of cellulose--the fiber in our diet
may have multiple layers
primary cell wall-relatively thin and flexible--outermost
middle lamella-like a glue in the middle
secondary cell wall--strong and durable--may be several layers--in between plasma membrane and primary wall
extracellular matrix (ECM)
made up of
collagen-accounts for 40% of the protein in a body!-strong fibers outside the cell
fibronectin-what connects the collagen and proteoglycan to the integrins
proteoglycan complex-web of tiny fibers
ECM connects to integrins (membrane proteins that connect to ECM on outside and microfilaments on the inside)
Cell Junctions
plasmodesmata
perforates the cell wall in plant cells
cytosol passes through to connect the internal chemical environments of neighboring cells
Tight junctions
plasma membranes are pressed tightly against each other
makes skin water tight
bound by proteins
Desmosomes
function like rivets
intermediate filaments anchor the desmosomes
attach muscle cells
Gap junctions
provide cytoplasmic channels between cells
allow for communication between cells
lots in heart muscle
Membranes
Membrane proteins
integral proteins
peripheral proteins
penetrate into the hydrophobic interior of the membrane
some are transmembrane (all the way through)
not embedded in the bilayer
usually loosely bound to the surface of the membrane (often to the surfaces of the integral proteins)
Functions
1-transport
2.Enzymatic activity- the protein itself may be an enzyme
3.Signal transduction-it may be the transmitter for a message from outside the cell to inside if a molecule cannot go inside itself
4.Cell to cell recognition- glycoproteins can act as id tags- if they bind it is a short binding time as opposed to #5
- Intercellular joining- proteins may hook together (junctions) more long lasting than cell to cell recognition
- attachment to the extracellular matrix and cytoskeleton--helps maintain cell shape can send messages ECM to microfilaments and vice versa
Transport across a membrane
membrane is semi permeable
passive transport- diffusion across a biological membrane without the use of energy
diffusion-movement of particles of any substance so that they spread out into the available space
always diffuses down the concentration gradient
osmosis- diffusion of water- water always goes from the hypo to the hyper solution
simple diffusion- no assistance needed-- ideal molecule to cross the bilayer would be very small and nonpolar
facilitative diffusion- needs assistance across the membrane
tonicity- has to do with the concentration of solutes
isotonic- solute concentration is the same
hypertonic- solute concentration is higher
hypotonic- solute concentration is lower
channel protein- tunnel across the membrane that always stays open
carrier protein- changes it's shape to help a molecule across
ie aquaporin--facilitates the diffusion of water
ie ion channels- allows ions to pass through--many are gated and open or close in response to a stimulus
active transport- uses energy-moving against the concentration gradient
Electrogenic Pump ie- sodium potassium pump-body needs high Na out and high K in the cells
driven by the membrane potential- difference in net charge from in and out of cell--cell is negative compared to the outside of the cell
cotransport-active transport of one molecule makes another passively follow
symport-both molecules go in the same direction
antiport- one goes in one direction and makes the other go in the opposite direction
bulk transport
exocytosis-exits the cell
endocytosis-bringing in to the cell
phagocytosis-cellular eating- larger molecules are 'grabbed'
pinocytosis- cellular drinking- a pit is made in the membrane- smaller molecules
receptor mediated endocytosis- only specific things are brought in. The 'pit' is covered in receptors
cell knows where to perform endocytosis due to a coat protein