Cell Biology Flashcards
what are cells? how many? what type?
smallest functional unit of organization 35-40 trillion on average human cells are eukaryotic each suited for specific purpose many types, combine to form tissues structure & organelle composition suit cell function
eukaryotic
organized nucleus with membrane surrounding it along with several other membrane-bound organelles
plasma membrane function
separates inside from outside of cell
what is most abundant molecule in body?
water
most of water in cell membrane 2/3, 1/3 is extracelullar
amount of body water in intracellular compartment
inside plasma membrane
2/3
amount of body water in extracellular compartment, breakdown of two sections
extracellular compartment 1/3 body water
tissue fluid- interstitial fluid ISF, blood plasma
out of tissue fluid, 3/4 is ISF, 1/4 is in blood vessels
difference in ICF and ECF
ICF-higher in proteins, lower in sodium, higher in potassium
ECF-lower proteins, higher sodium, lower potassium
what is ISF similar to? why?
plasma
boundary between two spaces is not very selective
nucleus
stores cell’s DNA
controls cell growth and reproduction
mitochondria
perform cellular respiration
“powerhouse of cell”
ribosomes
produce proteins
endoplasmic reticulum
synthesis, folding, modification, transport of proteins
golgi apparatus
process and package macromolecules (proteins, lipids)
transport lipids
create lysosomes
lysosomes
stomach of cell
contain digestive enzymes and digest worn out organelles, food particles, engulfed viruses or bacteria
peroxisomes
break down fatty acids
transfer hydrogen
proteasomes
digest proteins by proteolysis
cytoskeleton
gives a cell its shape, offers support, and facilitates movement through three main components: microfilaments, intermediate filaments, and microtubules
three compartments of cytoskeleton
microfilaments
intermediate filaments
microtubules
what is plasma membrane made of
phosopholipid bilayer with integral and peripheral proteins
what is plasma membrane barrier to? type of permeability?
water soluble molecules
selectively permeable
functions of proteins in plasma membrane
receptors-ligands to attach to channels/carriers-allow for water soluble molecules to move inside cell enzymes-catabolize chemical reactions anchors-for cytoskeleton recognition (antigens)-markers
function of cholesterol in plasma membrane
provides fluidity for proteins
structure of phospholipids in PM
glycerol head-hydrophilic
fatty acid tails-hydrophobic
functions of plasma membrane receptors
bind specific extracellular molecules
elicit changes in cell activity via signal transduction pathways
types of plasma membrane receptors that bind specific extracellular molecules
first messengers:
hormones
growth factors
neurotransmitters
these are signaling molecules that tells a cell to do something (speed up, slow down)
types of plasma membrane receptors that elicit changes in cell activity via signal transduction pathways
g-proteins
enzymes
ion channels
signal transduction pathway
extracellular messenger binds
intracellular machinery process started
extracellular message transduced inside cell
how does a water soluble signal exert its effects when it cannot get into cell?
signal transduction pathways
g-protein linked receptors
receptor binds to g protein that is linked to a guanine based nucleotide
g protein changes and becomes activated, leads to increase in second messenger-cAMP
second messenger leads to cell response (cAMP activates enzyme through kinases)
opens ion channels
target cell response
what is the most common signal transduction pathway?
g protein linked receptors
g protein linked receptors
what causes the g protein to become activated?
first messenger
g protein linked receptors
what happens when the g protein is activated?
enzyme catalyzes ATP to cAMP
g protein linked receptors
what is the second messenger?
cAMP
kinases
add phosphate group on
phosphorylate proteins and change their activity
enzyme-linked receptors
receptor has intrinsic activity or linked to enzyme
what do enzyme-linked receptors do?
convert extracellular signal to internal response
enzyme-linked receptors
most frequent enzyme
tyrosine kinase
phosphorylates intracellular proteins
what utilizes enzyme-linked receptors?
growth factors
enzyme-linked receptors important in what type of mechanism?
tumorigenesis
multiple myeloma-mutation in enzyme constitutively turned on, tyrosine kinase still active, overgrowth of B cells
enzyme-linked receptors
nerve growth factor
receptor intrinsically has kinase activity
gh binds, starts pathway
tyrosine phosphorylation changes activity of protein
ion-channel-linked receptors
receptor acts as a gated channel for ion flow across membrane
ion-channel-linked receptors
what happens with ligand binds?
channel is transiently opened, allowing ion flow
ion-channel-linked receptors
mechanism
convert extracellular signal to internal response
ion-channel-linked receptors what is this involved in?
neuron conduction & muscle contraction
ion
atom that has gained or lost electrons, take on electrical charge as a result
what can freely pass through plasma membrane?
lipid-soluble molecules
two types of transport-how do water soluble molecules get inside cell?
passive
active
passive transport
rely on gradients, don’t require energy
active transport
transport molecules against gradients, require energy
examples of passive transport
diffusion
osmosis
facilitated diffusion
examples of vesicular transport
endocytosis
exocytosis
charges of cell
inside more negatively charged
outside more positively charged
gradient for sodium in cell
outside higher
inside lower
gradient for potassium in cell
inside higher
outside lower
diffusion
movement of molecules across membrane from high to low concentration
when does diffusion stop?
when concentration on both sides is equal
no net movement
what utilizes diffusion?
lipid soluble molecules
steroids, thyroid hormones, gases, alcohol
what molecules use diffusion through nonspecific protein channels?
uncharged small water-soluble molecules
what accelerates diffusion?
larger gradients
heat
osmosis
diffusion of water towards higher solute concentration
what binds water in the body?
sodium glucose urea proteins bc of negative charge
wherever _______ goes, water always follows
sodium
glucose
urea
proteins
isotonic
does not cause osmotic flow of water into or out of a cell
hypotonic
less solutes causes osmotic flow of water into cell
hypertonic
more solutes causes osmotic flow of water out of cell, crenation
facilitated diffusion
carrier proteins transport molecules too large to fit through channel proteins (glucose, amino acids)
does not require output of energy
steps for facilitated diffusion
molecule binds to receptor site on carrier protein
carrier protein changes shape, molecule passes through
facilitated diffusion
receptor sites
highly specific to certain molecules
only facilitate movement of one particular molecule or a very closely related group of molecule
carrier-mediated transport
transport ions & organic substances
facilitated diffusion
active transport
characteristics of carrier-mediated transport
specific-single or similar substrates
saturable-rate of transport depends on number of transport proteins
regulated (sometimes)-cofactors such as hormones
types of gradients in active transport
electrical
chemical
electrochemical
active transport
carriers require energy to move substrates against a gradient
primary active transport
energy is used to move substrate against gradient
Na/K ATPase
Ca ATPase
H/K ATPase