1.19 - 6.3 Flashcards
ex. of positional information
- Barr bodies next to nuclear envelope
- rRNA genes in nucleolus
- Golgi bodies adjacent to RER
- centrioles templating perpendicularly
- dorsal-ventral gradients of proteins
- cytoskeleton
what do the nurse cells of a fruit fly egg tell us
positional distinction may start in egg, needed to direct positional information in next generation
what does it mean for a cell to be polarized
having distinct basal and apical region, specific functions carried out in each region
enzymes are usually _______
proteins
biological catalysts
speed up reaction without being consumed, lower activation energy
how do enzymes usually work
usually organized in pathways, work toward goal in stepwise fashion
true or false: enzymes aren’t very specific
false - highly specific
what are essential to maintain homeostasis?
feedback mechanisms
ex. of receptor-mediated communication/feedback mechanisms
hormones: act at distance, slow, low concentration
nerves: neurotransmitters, rapid, high concentration
signal transduction pathway
allows event on external side of membrane to trigger response in cell
results of signal transduction
- amplification of signal
- response
what are examples of a response of signal transduction
regulation of gene expression in nucleus or structural change
many enzymes and signaling pathways are organized as what?
multiprotein complexes that are physical associated
all organisms have cells that can what?
grow and divide
how do bacteria and archaea divide
binary fission
binary fission
- first ensure one copy of each daughter chromosome is in opp. ends of cell
- growing of membrane/wall across center
what division protein is commonly used in binary fission
Ftsz
how do yeast and some other fungi divide
by budding
how do eukaryotes usually divide
mitosis and meiosis
binary fission, budding, and mitosis/meiosis depend upon a mechanism to ensure what?
each cell obtains equal sets of genetic information
differentiation
cell acquires new phenotype or produces progeny with dif phenotype
somatic cells
specialized for special function in organism, diploid
germ cells
sperm and oocytes, haploid
fertilized zygote is ______potent
toti
stem cells are _____potent
both multi and pluri
ex. of pluripotent stem cells
embryonic stem cells
pluripotent
gives rise to most cells
totipotent
gives rise to all cells
multipotent
gives rise to some cells, more specific and less options
ex. of multipoint stem cells
adult stem cells: neural, mesenchymal, hematopoietic
all stem cells have what ability?
to self-renew
terminally differentiated cells
have lost the capacity to divide
compartments in a cell differ in composition of what?
membrane and internal milieus
how do membranes enable cells to maintain homeostasis?
- control solute concentrations across membranes
- adapt to altered metabolic situations
- process information
- transport nutrients in and waste product out
membranes (other than nuclear envelope) require membrane proteins to transport what?
polar molecules, hydrophilic, large biologic molecules
why can’t polar molecules pass freely through membrane?
because of hydrophobic interior
membrane proteins maintain ion concentration __________
differences
what do ion concentration differences create?
electrochemical gradients
what do electrochemical gradients do
store potential energy and process electrical signals
what ion concentrations are higher outside of the cell
Na+, Ca2+, Cl-
what ion concentrations are higher in the cell
K+
the inside of a resting animal cells is slightly ________ charged compared to the outside
negatively
2 main types of ion transport
- channels
- carriers
channel proteins
contain pore region through which solutes pass at HIGH flux rates when the channel is open
what are channel proteins composed of
1+ alpha subunits
channel proteins have:
- solute selectivity
- rapid rate of solute permeation
- gating mechanism
ex. of channels
- ion channels
- aquaporins
- porins (proks, mito)
- gap junctions
- nuclear pore complexes
- ER protein translocaters
channel pore
inner part of channel protein
channel configuration
vary from a single with pore to several to form 1 pore or several with several pores
true or false: most channels aren’t selective for a particular solute
false
when some channels aren’t selective for a particular solute, what are they?
general cationic or anionic channels
channel proteins are regulated by what?
gating
gating
undergoing conformational changes to open and close in response to specific stimuli
ex. of types of gating:
- ligand
- voltage
- temperature
- stretch
true or false: gates can only be activated one time
false - thing of neuronal signaling
what does electrochemical gradient dictate?
the direction of movement
- energetically favorable direction
speed of channels
fast, 10^8 per second, close of maximal rate of diffusion of ions in water
carrier proteins
bind solutes on one side of the membrane, undergo allosteric change, and release them on the other side of the membrane
are channel or carrier proteins faster
channel
speed of carrier proteins
10^3 per second
where do carrier proteins transduce energy from
- electrochemical gradients
- ATP
- other sources
why are carrier proteins involved with active transport
use energy to transport substances against concentration gradient
2 main types of carrier proteins
- transporters
- pumps
transporters
usually couple energy from electrochemical membrane gradients to facilitate movement of substrate across the membrane
3 types of transporters
- uniporters
- symporters (cotransporters)
- antiporters (exchangers)
pumps
use energy from ATP hydrolysis and light directly to drive energetically less favorable substrate accumulation of efflux
2 categories of active transport
- primary
- secondary
primary active transport (pumps)
use ATP as the energy source to drive transport of solutes against electrochemical gradients
ex. of primary active transport
- Ca2+-ATPase
- Na+/K+-ATPase
secondary active transport (transporters)
don’t use ATP directly, use free energy stored in gradients
ions in a solution are ________
hydrated
what does it mean when ions are hydrated
surrounded by water molecules attracted by dipolar partial negative/positive charges
what is formed around each ion
hydration shell
is the hydration shell energetically favorable or expensive
favorable
what does the size of the hydration shell depend on
charge density and size of ion
do smaller ions have a higher or lower charge density?
higher
how do ion channels enable the partial dehydration of ions as they travel through?
ion forms weak bonds with amino acid residues, which mimics hydration shell and makes transport process energetically favorable/selective
