Quiz #3 Flashcards
What is bulk transport?
big molecules (polysaccharides) must be transported using a bulk transport mechanism
involves formation of vesicles
membrane is flexible and can bend into different shapes including pinching off into vesicles
this requires energy
What are the three types of endocytosis?
phagocytosis
pinocytosis
receptor-mediated
What is phagocytosis?
cell “eating”
uses a food vacuole
What is pinocytosis?
cell “drinking”
uses a vesicle
What is receptor-mediated endocytosis?
mechanism involved receptors to import specific things
each receptor only binds to ligands of a particular structure
clathrin binds to these receptors on the inside of the cell, gathering them and the membrane into a “pit” shape that eventually forms a vesicle
What is clathrin?
a coat protein that helps facilitate vesicle formation
What are lipoproteins?
transport fats to cells via the blood stream
What is a low density lipoprotein (LDL)?
low in density, but highest in cholesterol
often referred to as the “bad” cholesterol
What is a high density lipoprotein (HDL)?
highest density due to high protein/lipid ratio
these particles remove excess cholesterol from blood vessels
referred to as the “good” cholesterol
What is primary active transport?
systems that perform active transport using ATP directly
What is secondary active transport?
systems that use carrier proteins driven by ion gradients
What are uniporters?
carrier or transport proteins that transport only one type of molecule
What are symporters?
carrier or transport proteins that transport two different molecules in the same direction
What are antiporters?
carrier or transport proteins that transport two different molecules in opposite directions
What are bacterial cell walls?
provide shape and protection from bursting in hypotonic environments
almost all bacterial cell walls contain peptidoglycan
What are gram-positive bacteria?
simple cell wall structure
thick peptidoglycan
single plasma membrane
What are gram-negative bacteria?
complex cell wall structure
thinner peptidoglycan
have two plasma membranes
What is peptidoglycan?
a thin sheet composed of: chains of repeating disaccharide unit composed of two monosaccharides and small peptides
synthesized only in growing cells
It contains a glucose derivative that is also found in chitin
What is transpeptidation?
two peptide side chains attach to each other via covalent bonds, this cross-linking reaction is called transpeptidation, and it adds strength to the layer
What are antibodies?
there are many naturally occurring antibodies
some are specific to certain types of bacteria, based on their ability to target prokaryotic-specific structures
What are some common targets of antibodies?
prokaryotic ribosomes (responsible for protein synthesis) prokaryotic cell wall
What is lysozyme?
antimicrobial present in our bodily fluids
enzyme that catalyzes hydrolysis of beta 1-4 linkages between NAG and NAM
peptidoglycan falls apart, cells lyse
What is penicillin?
as bacterial cell grows, it synthesizes more peptidoglycan
transpeptidation reaction is catalyzed by a specific enzyme
the enzyme is inhibited by penicillin
inhibition leads to a weakened peptidoglycan
works best on gram positive cells
as the cell grows, new peptidoglycan is not formed, eventually the cell bursts
What is a capsule?
mostly polysaccharides
further protects cell from environment
can be used to stick bacteria to surface
capsule is very rare in archaea
What are the two types of pili?
fimbriae
sex pilus
What is fimbriae?
attach to surfaces or host cells
What is sex pilus?
for transfer of DNA between bacteria cells
DNA is transferred to another bacteria (bacterial conjugation)
plasmids (small circular DNA) can be transferred
What is taxis?
the ability to move toward or away from stimulus
What is chemotaxis?
is the movement toward or away from a chemical stimulus
How do bacteria move?
motile bacteria move in a series of “runs” and “tumbles”
duration of the run is longer if the concentration of the “attractant” increases during the run
What are flagella?
for movement
flagella of bacteria, archaea, and eukaryotes are composed of different proteins and likely evolved independently
rotation can be clockwise or counterclockwise
CCW = run
CW = tumble
What are plant cell walls?
young plant cell secretes a thin cell wall outside the plasma membrane, the primary cell wall
as cell matures, cell wall is strengthened
some secrete hardening substances into the primary cell wall, while some add a secondary cell wall
a cell may have many layers
What is the middle lamella?
between primary cell walls of adjacent plant cells
composed of sticky polysaccharides called pectin
What is plasmodesmata?
because of the thick cell wall and middle lamella, plant cells are isolated from each other
to allow communication between cells, plant cell walls contain pores (tunnels) between cells
allows passage of H2O and small solutes between cells
these pores can open and close depending on the environmental conditions or age of the plant
What do animal cells have instead of a cell wall?
no cell wall, but they secrete proteins and polysaccharides = extra cellular matrix (ECM)
ECM consists mostly of glycoproteins and protein fibres
What are the different ways adjacent animal cells can be attached?
Tight junctions
Desmosomes
Gap junctions
How do tight junctions connect adjacent animal cells?
membranes of neighboring cells are essentially fused
tight seals are formed
How do desmosomes connect adjacent animal cells?
tightly fasten cells together at certain points
made of strong protein filaments that cross the intercellular space
can withstand mechanical forces
How do gap junctions connect adjacent animal cells?
multi-subunit structures that form a channel between adjacent cells
allow free exchange of small molecules
this allows tissues to coordinate responses to stimuli
2 connexons form a gap junction
What is cytoplasm?
interior of a prokaryotic or eukaryotic cell
What is cytosol?
the fluid portion of the cytoplasm (without structures or membrane)
What is the endosymbiont hypothesis?
mitochondria and chloroplasts arose by endosymbiosis
a mutually beneficial relationship derived from a cell living inside another cell
What does the endosymbiont hypothesis say about mitochondria?
mitochondria: are descended from an ancient bacterium
most closely-related extant bacteria are the alpha-proteobacteria
What does the endosymbiont hypothesis say about chloroplasts?
are descended from an ancient cyanobacterium (photosynthetic bacterium)
What is the evidence for endosymbiosis?
mitochondria and chloroplasts have their own DNA (circular), genes are organized like prokaryotic genome, and they have their own ribosomes (similar to prokaryotic ribosomes)
