Week 2 Flashcards
endomembrane system components consists of a network of internal membranes made up of ___
lipid bilayers
endomembrane system components:
include what structures?
endoplasmic reticulum (ER)
- smooth (SER) –> no ribosomes
- rough (RER) –> has ribosomes on its surface
Golgi complex
vesicles
describe endoplasmic reticulum structure:
network of ___
wall of tubules composed of a ___
the space inside the tubes is called the ___
the smooth and rough ER are…
network of interconnected tubules
wall of tubules composed of a lipid bilayer
the space inside the tubes is called the lumen
the smooth and rough ER are interconnected with each other and the outer bilayer of the nuclear envelope
specialized functions of the SER:
site of ___
site of ___
site of ___
lipid synthesis
cholesterol and steroid synthesis
fatty acid desaturation
specialized functions of the RER:
site for ___
these ___ are used for…
synthesis of proteins bound for export from the cell, or for use in the endomembrane system
structure of Golgi apparatus:
series of ___
wall of tubes are a ___
cis face:
trans face:
flattened tubes (sacs)
lipid bilayer
cis face: receives transport vesicles from ER
trans face: sends secretory vesicles away from the Golgi
3 function of Golgi apparatus:
(1) proteins and other molecules may be modified
(2) molecules are sorted by eventual destination
(3) molecules are released in vesicles
describe the Rough ER
has ribosomes on its surface, primarily manufactures proteins
describe the smooth ER
no ribosomes, manufactures other macromolecules
describe vesicles
transport of molecules to and from the Golgi Complex
describe the Golgi complex
modifies, sorts, packages, and distributes macromolecules
journey through the endomembrane network
(1) proteins made in the RER
(2) transport vesicle: contains products
(3) Golgi apparatus –> chemical modifications
(4) secretory vesicles
(5) exocytosis
exocytosis (definition)
process by which material is exported out of the cell
a ___ fuses with the plasma membrane to release its contents out of the cell
example:
secretory vesicle
ex. insulin secretion
material can enter the cell by ___
endocytosis
the plasma membrane surrounds contents from outside the cell, trapping it in an ___
endocytic vesicle
the ___ surrounds contents from outside the cell, trapping it in an endocytic vesicle
plasma membrane
endocytosis can be a ___ process (using receptors), or ___ (taking up of water and nutrients)
specific == using receptors
passive == taking up water and nutrients
endocytosis can be a specific process (___), or passive (___)
specific == using receptors
passive == taking up water and nutrients
the endocytic vesicle will then fuse with another type of vesicle, a ___
lysosome
lysosomes are…
specialized vesicles that digest:
- material from outside the cell
- or material from inside the cell (“worn out” organelles)
primary lysosome (comes from the Golgi) contains ___
digestive enzymes
lysosomes fuse with ___ or other cellular organelles, to form a ___
endocytic vesicles
secondary lysosome
tuberculosis bacterium:
TB kills about ___ annually
2 million
TB bacteria are able to prevent…
Thus…
phagosome/lysosome fusion
thus, TB survives and has a place to live in the cell
TB bacteria multiples…
___ and ___ it
spreads to…
multiplies inside the macrophage
kills and devours it
spreads to infect more cells
mitochondria:
describe structure of:
membrane
outer membrane
inner membrane
center
double lipid bilayer
outer membrane covers entire organelle
inner membrane is extensively infolded
- folds are called cristae
liquid center –> the matrix
what is the endosymbiotic theory?
mitochondria only arise from pre-existing mitochondria –> reproductive themselves
what is function of mitochondria?
energy metabolism –> ATP production
chloroplast (structure)
membrane
center
double lipid bilayer
outer and inner envelope membranes cover the entire organelle
inside center:
- internal membranes organized into stacked disks
- thylakoid – single disk
- granum – stack of thylakoids
- stroma – soluble material around grana
chloroplast (function)
site of photosynthesis in plant cells
light energy is converted into usable chemical energy
cytoskeleton:
cells need ___
internal structural support
the cytoskeleton is made up of…
some ___ are purely for…
some ___ play a role in…
some ___ help…
multiple types of protein fibers
- structural support
- transport within the cell
- help the cell move
extracellular matrix is made of…
secreted molecules from cells
3 functions of extracellular matrix:
(1) hold cells together in tissues (glue)
(2) strengthens and cushions tissues like cartilage and bone
(3) can filter material b/n cells (ex. kidneys)
where is the extracellular matrix and cytoskeleton located in the cell?
extracellular matrix – outside cell
cytoskeleton – inside cell
what is the extracellular matrix made of?
extracellular fluid
collagen
fibronectin
proteoglycans
integrins (in the plasma membrane)
what is the cytoskeleton made of?
microfilaments
plasma membrane defines…
it’s a ___
defines the inside and outside of a cell
it’s a barrier
PMs are ___ barriers because they regulate…
selective barriers
regulate transport into/out of cells
the PM is ___ and cells can adjust…
the PM is dynamic and cells can adjust
- the chemistry of the PM
- the molecules that associate with it
who discovered that the plasma membrane is a phospholipid bilayer?
what did he use?
evert gorter
red blood cells
why did evert porter use RBCs to study the phospholipid membrane?
(1) easy to obtain
(2) easy to count
(3) are of uniform size
what was the result of evert gorter’s experiments?
surface area (SA) of the monolayer is double the surface area of the cells (2:1) ratio
cell membranes are a phospholipid bilayer
what would the ratio have been if he had used nuclear envelope membranes?
4:1 ratio
nucleus has a double bilayer membrane
plasma membranes are ___ than just a phospholipid bilayer
much more
other parts of the plasma membrane:
polysaccharides
peripheral proteins
integral (transmembrane) proteins
cholesterol
what is the fluid mosaic model of membranes?
PMs are fluid structures
phospholipid bilayer is like a “lake”. Molecules are “floating” around in it
how did we come up with the fluid mosaic model of membranes?
what did this experiment entail? and show?
cell fusion experiment – mix a mouse cell (green membrane proteins) with human cell (red membrane proteins)
over time, the hybrid cells show increasingly intermixed proteins
proteins are laterally diffusing around the membrane –> the membrane is fluid
what is the other experiment that shows the cell membrane is fluid?
what did this experiment show?
photo-bleaching experiments
label membrane proteins with a fluorescent dye –> bleach and area of the cell surface with a laser –> slowly, the bleached spot disappears because other dyed membrane proteins flow into the area –> demonstrates the cell membrane is fluid
why is it important to maintain fluidity level?
if too fluid –> will not serve as a boundary and will fall apart
if too solid –> will not permit integral proteins to flex (change shape) and carry out their functions
- ex. integral transport or signaling proteins
how do cells regulate membrane fluidity by changing ___ in ___ ways
changing fatty acid chains of phospholipids
2 ways
what are the 2 ways cells change membrane fluidity by changing fatty acid chains of phospholipids?
change % of phospholipids with saturated/unsaturated FA chains
change % of phospholipids with long or short FA chains
how do cells change % phospholipids with saturated/unsaturated FA chains?
higher concentration of phospholipids w/ unsaturated FAs –> pack less tightly == more fluid
higher concentration of phospholipids w/ saturated FAs –> pack more tightly == less fluid
how do cells change % of phospholipids with long or short FA chains?
higher concentration of phospholipids w/ short FAs –> pack less tightly == more fluid
higher concentration of phospholipids w/ long FAs –> pack more tightly == less fluid
changes in ___ affect membrane fluidity and cells need to respond
external temperature
cells are at a lower temp –> how does PM change?
cold temp makes PM less fluid
PM needs to become more fluid == pack less tightly
make phospholipids with FA chains that are:
- shorter
- more unsaturated
cells are at a higher temp –> how does the PM change?
warm temp makes PM more fluid
PM needs to become less fluid == pack more tightly
make phospholipids with FA chains that are:
- longer
- more saturated
a major barrier for molecules crossing a plasma membrane is the ___
hydrophobic interior
why is the hydrophobic interior a major barrier for molecules crossing a plasma membrane?
permeable to non polar molecules
less permeable to small polar molecules
no permeability for larger polar molecules or ions
what are the types of membrane transport?
diffusion
active transport (anti-diffusion)
what is diffusion?
the movement of molecules across the membrane from high concentration to low concentration
does not require use of cellular energy
what is active transport (anti-diffusion)?
movement of molecules across the membrane from low concentration to high concentration
requires use of cellular energy
what is necessary for simple diffusion to occur?
1) PM must be permeable to particular molecule
2) must be a different in [ ] of that molecule across the membrane
the diffusion of molecules that can cross the membrane on their own must be ___
facilitated
FD is carried out by ___, including ___ and ___
transmembrane proteins
channel proteins
carrier proteins
transmembrane proteins are ___ and…
selective
only transport certain molecules
facilitated diffusion is movement driven by diffusion. Is energy required?
no
cells can regulate FD by regulating:
presence or absence of specific carrier or channel proteins
regulating the function of specific carrier or channels
how are channel proteins and carrier proteins different?
channel proteins:
- like tunnels
- don’t bind to the molecules they transport
- can be always open or gated (opened or closed)
- direction of movement depends on concentration
- movement does not require energy input
carrier proteins:
- must bind to the molecules that they transport
- direction of movement depends on concentration
- movement does not require cellular energy input
- 3 basic types of carrier proteins
what are the 3 basic types of carrier proteins and what do they do?
uniporters –> transport a single type of molecular species
symporters –> transport 2 molecular species in the same direction, at the same time
antiporters –> transport 2 molecular species in opposite directions, at the same time
how can we distinguish b/n carriers and channels?
by looking at their kinetics (rates) of transport
channels show linear kinetics
carriers show saturation kinetics
channels show ___ kinetics
linear
carriers show ___ kinetics
saturation
active transport (anti-diffusion) is used by cells to…
build up a concentration gradient of a molecule across a plasma membrane
in active transport, moving molecules against a concentration gradient requires ___ and requires ___
carrier proteins
energy (usually ATP)
in active transport, concentration gradients are critical for some ___
biological processes (cellular respiration)
what are the 2 ways solutes can be transported across plasma membranes?
diffusion
active transport
what are the 2 types of diffusion and what do they do/require?
simple and facilitated –> neither require energy
simple:
- no proteins required
- no energy input
facilitated:
- channel or carrier
- movement driven by diffusion
- no energy input
what does active transport require?
carrier
energy input
what is a selective (semi-permeable) barrier?
a barrier that allows water molecules to pass through, but not most of the molecules dissolved in the water
ex. plasma membrane
___ is a measure of the concentration of solutes dissolved in water
solute potential (Psi s)
pure water has no solutes: it’s psi s = ___ and what is the significance of its value?
psi s = 0
highest value
water molecules are most concentrated at psi s = ___
0
adding solutes ___ psi s
psi s…
lowers
psi s < 0
negative value
as solute concentration increases, water concentration ___, psi s ___
decreases
decreases
as solute concentration ___, water concentration decreases, psi s ___
increases
decreases
water moves from areas of ___ psi s to areas of ___ psi s
higher psi s to lower psi s
if the psi s inside and outside of cell are equal…
water is entering and leaving the cell in equal amounts
if psi s is higher outside of a cell than inside:
greater water concentration outside the cell
cell is hypertonic
solution is hypotonic
water will rush into the cell
cell will swell
cell could burst
if psi s is higher inside of a cell than outside:
greater water concentration inside of cell
cell is hypotonic
solution is hypertonic
water will rush out of cell
cell will shrink, could dehydrate and die
brain capillaries are…
fine blood vessels that feed brain tissue
molecules must exit a brain capillary by moving…
molecules cannot pass…
this strict control is known as the ___
through the plasma membrane of a capillary wall cell
b/n the cells thru the intercellular junction
blood-brain barrier
can medicines enter the brain easily?
no; because blood brain barrier keeps most medicines from entering the brain
how to breach the blood-brain barrier?
lower the psi s of blood (inject a solute)
water moves out of capillary wall cells
capillary wall cells shrink slightly and create an opening b/n cells
medicine can pass into the brain
Wwhat does mannitol do?
lowers the psi s of blood
water moves out of capillary wall cells into the blood
capillary wall cells shrink slightly and create an opening b/n cells
medicine can pass into the brain
first law of thermodynamics is also known as the…
it states that…
conservation law
energy cannot be created or destroyed
energy can only change from one form of energy to another
total amount of energy in the universe remains constant
2nd law of thermodynamics states…
no energy transfer is 100% efficient
some energy is always lost to universe and becomes unusable
entropy is…
it is continuously ___ in the universe
unusable energy
it is continuously increasing
usable energy (free energy) in the universe is ___
continuously decreasing
free energy is known by the letter
G
what is the formula for free energy (G)?
G = H - TS
G = energy available to do work
H = enthalpy (energy in a molecule’s chemical bonds)
TS = amount of disorder in a molecule
T = absolute temperature
S = entropy, unavailable energy
-(delta) G:
___ reaction
which has more free energy, products or reactants?
spontaneous or non-spontaneous?
exergonic
reactants have more free energy than products
spontaneous
+(delta) G:
___ reaction
which has more free energy, products or reactants?
spontaneous or non-spontaneous?
endergonic
products have more free energy than reactants
non-spontaneous
free energy is referred to as ‘G’ = the energy…
the energy in the chemical bonds of a molecule that’s available to do work
describe reaction coupling
energy to drive endergonic reactions comes from exergonic reactions
ATP hydrolysis is endergonic/exergonic
exergonic –> the energy is used to power many endergonic reactions
ATP + H2O –> ADP
