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