ch 5 eukaryotic cell structure

Question 1

common features of eukaryotic cells

Answer 1

morphologically diverse to adapt to environments
typically larger than bacterial and archaeal cells

Question 2

common features of eukaryotic cell organization

Answer 2

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

Question 3

eukaryotic cell envelope

Answer 3

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

Question 4

photosynthetic algae cell wall components

Answer 4

cellulose
pectin
silica
calcium carbonate

Question 5

fungal cell wall components

Answer 5

chitin
glucan

Question 6

actin filaments

Answer 6

small protein filaments, 4-7 nm in diameter
composed of actin protein
functions: moving cellular structures, help cells change shape, endocytosis, cytokinesis

Question 7

intermediate filaments

Answer 7

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

Question 8

microtubules

Answer 8

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

Question 9

ER

Answer 9

irregular network of branching and fusing membranous tubules and flattened sacs (cisternae)
function: hub for molecular synthesis and transport, cell membrane synthesis

Question 10

golgi apparatus

Answer 10

made of flattened saclike cisternae stacked on each other
function: packages materials and prepares them for secretion

Question 11

vacuoles

Answer 11

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

Question 12

transport and secretory pathway for proteins

Answer 12

• 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

Question 13

degradation of proteins

Answer 13

quality assurance mechanism
- unfolded or misfolded proteins and secreted into cytosol, targeted for destruction by ubiquitin polypeptides
- proteasomes destroy targeted proteins

Question 14

endocytic pathway

Answer 14

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

Question 15

receptor-mediated endocytosis

Answer 15

binding of a ligand to a receptor triggers endocytosis

Question 16

types of endocytosis

Answer 16

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

Question 17

autophagy

Answer 17

delivery of materials to be digested by a route that does not involve endocytosis

Question 18

macroautophagy

Answer 18

non selectively digests and recycles cytoplasmic components

Question 19

extracellular vesicles

Answer 19

can contain proteins, lipids, and nucleic acids
formed by pinching off membrane that then surrounds their molecular cargo

Question 20

nucleus

Answer 20

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)

Question 21

nuclear envelope

Answer 21

two lipid bilayer membrane that surrounds the nucleus
continuous with ER
outer membrane is covered with ribosomes

Question 22

nuclear pore complex

Answer 22

proteins that make pores that penetrate the envelope
pores allow materials to be transported into or out of nucleus

Question 23

nucleolus

Answer 23

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

Question 24

ribosomes

Answer 24

80S in size (60S + 40S)
rough ER ribosomes: synthesize integral membrane or secreted proteins
free ribosomes: synthesize non-secretory or nonmembrane proteins

Question 25

endosymbiotic hypothesis

Answer 25

mitochondria, hydrogenosomes, and chloroplasts are all though to have evolved from bacterial cells that invaded or were ingested by early ancestors of eukaryotic cells

Question 26

mitochondria

Answer 26

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

Question 27

hydrogenosomes

Answer 27

small energy capture organelles in some anaerobic protists double membrane, no cristae, usually lack DNA ATP is generated by fermentation process rather than respiration

Question 28

chloroplasts

Answer 28

type of plastid - cytoplasmic organelles found in algae and plants that contain pigments site of photosynthetic reactions surrounded by double membrane

Question 29

stroma

Answer 29

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

Question 30

thylakoids

Answer 30

site of light reactions of photosynthesis (ATP and NADPH production)

Question 31

flagella

Answer 31

long whiplike filaments move in undulating fashion

Question 32

cilia

Answer 32

short hairlike structures beat with two phases, working like oars/rowing

Question 33

axoneme

Answer 33

central filament consists of a set of microtubules in a 9 + 2 arrangement for support and structure

Question 34

basal body

Answer 34

at base of flagellum or cilium in cytoplasm directs synthesis of flagella and cilia