basic features that all cells share
- plasma membrane (selective barrier that bounds the cell)
- cytosol (semifluid jellylike substance)
- chromosomes (carry genes in the form of DNA)
- ribosomes (tiny complexes that make proteins according to instructions from the genes)
prokaryotic cells
- lack nuclei and other membrane-enclosed organelles
- small
"before nucleus"
eukaryotic cells
- membrane-enclosed nucleus, contains cell's linear chromosomes
- membrane bound organelles in cytoplasm
- larger (cell-wise)
"true nucleus"
what do prokaryotic and eukaryotic cells have in common?
- plasma membrane
- ribosomes
cytoplasm
- the interior of the cell that contains, within the cytosol, organelles
- in eukaryotic cells - refers to the region between nucleus and the plasma membrane
organelle
- a subcellular structure that have specialized forms and functions
plasma membrane
- forms a boundary for the cell
- selectively permeable
- permits the passage of selected materials into and out of the cell
what is the plasma membrane made up of?
- phospholipids
- proteins
- associated carbohydrates
(these molecules determine the function of the membrane)
what is going on inside the eukaryotic cell?
- extensive, elaborately arranged internal membranes divide cell into compartments (organelles)
- compartments provide different local environments that support specific metabolic functions
- this allows incompatible processes to occur simultaneously in a single cell
how do the plasma membrane and organelle membranes participate in the cell's metabolism?
- many enzymes are built right into the membranes
what is the basic fabric of most biological membranes?
- a double layer of phospholipids and other lipids
- embedded in bilayer/attached to surface are diverse proteins
membrane and composition
- each type of membrane has a unique composition of lipids and proteins suited to that membrane's specific functions
example: enzymes in mitochondria membranes function in cellular respiration
cell wall (prokaryotic cell & plant cell)
- rigid structure outside of the plasma membrane
- in plants, protects and helps maintain their shape
- provides a barrier for some substances to enter the plant cell
- primary component: cellulose
bacterial chromosome (prokaryotic cell)
- carries genes in the form of DNA
nucleoid (prokaryotic cell)
- region where the cell's DNA is located (not membrane bound)
endoplasmic reticulum
- network of membranous sacs and tubes
- active in membrane synthesis and other synthetic + metabolic processes
- has rough and smooth regions
plasmodesmata (plant cell)
- perforate the cell wall
- channels that connect plant cells
- allow communication and movement of materials between cells
which two cellular components are involved in the genetic control of the cell?
- nucleus
- ribosomes
nucleus
- houses most of the cell's DNA
- template to make messenger RNA (mRNA), which contains the code to produce protein
- most noticeable organelle in cell due to large relative size
nuclear envelope
- a double membrane that surrounds the nucleus
- continuous with the rough ER
- has pore structures that regulate what may enter or leave the nucleus
chromatin
- complex of DNA and protein housed in the nucleus that forms chromosomes
- diffuse threads of this condense into visible chromosomes as cell gets ready to divide
nucleolus
- region of the nucleus where ribosomal RNA (rRNA) is synthesized and complexes with proteins to form ribosomal subunits
ribosomes
- complexes that synthesize protein
- composed of rRNA and protein
- sites of protein synthesis within the cell
- consist of a large and small subunit
free ribosomes
- float in cytosol
- produce proteins that are used within the cell
bound ribosomes
- attached to the ER
- make proteins destined for export from the cell
endoplasmic reticulum (ER)
- network of membranes and sacs
- makes up more than half the total membrane structure in many cells
- two types of ER: smooth and rough
cisternal space
- internal area of the ER
smooth ER
- synthesis of lipids
- detoxification of drugs and poisons
- metabolism of carbohydrates
- storage of calcium ions
rough ER
- aids in synthesis of secretory and other proteins on bound ribosomes
- adds carbohydrates to proteins to make glycoproteins
- produces new membrane
what does the endomembrane system consist of?
ER (rough and smooth), golgi apparatus, lysosome, vacuole
golgi apparatus
- stacks of flattened membranous sacs
- has polarity (cis and trans faces)
- modifies proteins, carbohydrates on proteins, and phospholipids
- synthesizes polysaccharides
- sorting of "golgi" products - released into vesicles
lysosomes
- membranous sac of hydrolytic enzymes
- breakdown ingested substances, cell macromolecules, and damaged organelles for recycling
vacuole
- large membrane-bound vesicle
- assist in digestion, storage, waste disposal, water balance, cell growth, and protection
what does the endomembrane system do?
- organelles that work together to modify, package, and transport lipids and proteins
mitochondrion
- bounded by double membrane
- inner membrane has infoldings
- function: cellular respiration
chloroplast
- two fluid membranes around fluid stomata (contains thylakoids stacked into grana)
- function: photosynthesis
peroxisome
- specialized metabolic compartment bounded by a single membrane
- contains enzymes that transfer H atoms from substrates to oxygen, producing hydrogen peroxide, which is converted to H2O
cytoskeleton
- functions in structural support for the cell and in mobility and signal transmission
microtubules
- shape the cell
- guide organelle movement
- separate chromosomes in dividing cells
cilia and flagella
- motile appendages containing microtubules
- primary cilia play sensory and signaling roles
microfilaments
- thin rods that function in muscle contraction, amoeboid movement, cytoplasmic streaming, and support of microvilli
intermediate filaments
- support cell shape
- fix organelles in place
what are plant cell walls made of?
- cellulose fibers imbedded in other polysaccharides and proteins
extracellular matrix
- animal cells secrete glycoproteins and proteoglycans that form this
- functions in support, adhesion, movement, and regulation
cell junctions
- connect neighboring cells
how do plant cells connect?
- plasmodesmata
how do animal cells connect?
- tight junctions
- desmosomes
- gap junctions
the cell is...
- a living unit greater than the sum of its parts
endosymbiotic theory
- mitochondria and chloroplasts descended from prokaryotic cells once engulfed by ancestors of eukaryotic cells
EVIDENCE: double membrane structure, own ribosomes and circular DNA molecules, reproduce independently within the cell