ch 5 eukaryotic cell structure Flashcards
common features of eukaryotic cells
morphologically diverse to adapt to environments
typically larger than bacterial and archaeal cells
common features of eukaryotic cell organization
membrane delimited nuclei
membranes play important role in the structure of organelles
intracytoplasmic membrane complex serves as transport system to move material throughout the cell
eukaryotic cell envelope
consists of the plasma membrane and external coverings
plasma membrane is a lipid bilayer
lipids include sphingolipids, sterols, and phospholipids
microdomains made of different lipid and proteins participate in variety of cellular processes
photosynthetic algae cell wall components
cellulose
pectin
silica
calcium carbonate
fungal cell wall components
chitin
glucan
actin filaments
small protein filaments, 4-7 nm in diameter
composed of actin protein
functions: moving cellular structures, help cells change shape, endocytosis, cytokinesis
intermediate filaments
flexible but strong
10 nm in diameter
made of keratin and vimentin proteins
functions: structure, form nuclear lamina - supporting the nuclear envelope, help link cells together to form tissues
microtubules
shaped like thin cylinders approx 25nm in diameter
two protein subunits - alpha and beta tubulin in helical cylinder
functions: form spindle that separates chromosomes during mitosis and meiosis, cell movement, maintain cell shape and support
ER
irregular network of branching and fusing membranous tubules and flattened sacs (cisternae)
function: hub for molecular synthesis and transport, cell membrane synthesis
golgi apparatus
made of flattened saclike cisternae stacked on each other
function: packages materials and prepares them for secretion
vacuoles
roughly spherical organelle, enclosed in a single membrane
involved in digestion of nutrients - lysosomes
contain digestion enzymes - hydrolases - enzymes that hydrolyze molecules and function best under slightly acidic conditions
maintain an acidic environment by pumping protons in to their interior
transport and secretory pathway for proteins
- ribosome synthesizes an amino acid that targets them to the lumen of ER
- released from lumen in a small vesicle budding from ER
- vesicle moves to golgi
- proteins modified target them to final location
- transport vesicles released from golgi and move to final location
two secretory pathways at plasma membrane: - constitutive deliver to membrane, unregulated
- regulated secretory pathway, requires a signal
degradation of proteins
quality assurance mechanism
- unfolded or misfolded proteins and secreted into cytosol, targeted for destruction by ubiquitin polypeptides
- proteasomes destroy targeted proteins
endocytic pathway
used by all eukaryotic cells to bring materials into the cell
vesicles pinched off from the plasma membrane
mechanism for recycling molecules in the membrane
endocytosed material is delivered to lysosomes
receptor-mediated endocytosis
binding of a ligand to a receptor triggers endocytosis
types of endocytosis
phagocytosis - use of cell surface protrusions to surround and engulf particles
clathrin-dependent - clathrin protein-coated pits used to internalize hormones, growth factors, iron, and cholesterol
caveolin-dependent - caveolin coated vesicles involved in signal transduction and transport of small molecules
autophagy
delivery of materials to be digested by a route that does not involve endocytosis
macroautophagy
non selectively digests and recycles cytoplasmic components
extracellular vesicles
can contain proteins, lipids, and nucleic acids
formed by pinching off membrane that then surrounds their molecular cargo
nucleus
presence of a nucleus for DNA storage is the most profound difference btw eukaryotes and bacterial and archaeal cells
membrane bound spherical structure that houses chromosomes, that contain genetic info
contain chromatin, a complex of DNA and proteins (histones)
nuclear envelope
two lipid bilayer membrane that surrounds the nucleus
continuous with ER
outer membrane is covered with ribosomes
nuclear pore complex
proteins that make pores that penetrate the envelope
pores allow materials to be transported into or out of nucleus
nucleolus
site of rRNA synthesis
organelle that is not membrane enclosed
directs assembly of rRNA that combines with proteins to form partial ribosomal subunits
these partial ribosomes leave nucleus and mature in cytoplasm
ribosomes
80S in size (60S + 40S)
rough ER ribosomes: synthesize integral membrane or secreted proteins
free ribosomes: synthesize non-secretory or nonmembrane proteins
endosymbiotic hypothesis
mitochondria, hydrogenosomes, and chloroplasts are all though to have evolved from bacterial cells that invaded or were ingested by early ancestors of eukaryotic cells
mitochondria
site where ATP is generated by electron transport and oxidative phosphorylation
site of tricarboxylic acid cycle
outer membrane: contains porin proteins similar to gram-negative bacteria
inner membrane: contains cristae, infoldings that increase surface area
matrix: enclosed by inner membrane, contains ribosomes, mitochondrial DNA, and large phosphate granules
hydrogenosomes
small energy capture organelles in some anaerobic protists
double membrane, no cristae, usually lack DNA
ATP is generated by fermentation process rather than respiration
chloroplasts
type of plastid - cytoplasmic organelles found in algae and plants that contain pigments
site of photosynthetic reactions
surrounded by double membrane
stroma
a matrix surround by the inner membrane
site of dark reactions of photosynthesis (formation of carbs from water and CO2)
contains DNA, ribosomes, lipid droplets, starch granules, and thylakoids
thylakoids
site of light reactions of photosynthesis (ATP and NADPH production)
flagella
long whiplike filaments
move in undulating fashion
cilia
short hairlike structures
beat with two phases, working like oars/rowing
axoneme
central filament consists of a set of microtubules in a 9 + 2 arrangement for support and structure
basal body
at base of flagellum or cilium in cytoplasm
directs synthesis of flagella and cilia
