patho/phys exam 1 Flashcards
FUNCTIONS OF CELL MEMBRANE
what does it maintain and what does it coordinate
what kind of barrier is it
does it adhere to each other? If so, what does it form from the adhering
what 3 things does it exchange
what does it respond to changes in
what gradient does it maintain for nerves and muscles and for what kind of actvity
Homeostasis & cell survival: maintain intracellular contents of cells & coordinate activity with others - organelles should be close together
– Mechanical barrier
– Adhere together to form tissues
– Exchange nutrients (intake), wastes (CO2) & secretions
– Respond to changes in environment or signals – Maintain ionic gradient for electrical activity of… nerves & muscles have electrical activity which the ionic gradient is used for stimulation and contraction
COMPONENTS OF CELL MEMBRANE
what are the 2 kinds of lipids of the cell membrane
for the first kind of lipid, what barrier does it set and to what kind of substances
for the second kind of lipid, what 2 things does it provide to the membran e
for the first kind of lipid, what is the charge, polarity and philicity of the head and the tail
Lipids: phospholipids and cholesterol
– Barrier to passage of water-soluble substances – Provides fluidity & stability to the membrane
head (negatively charged, polar, hydrophilic)
tails (uncharged, nonpolar, hydrophobic)
COMPONENTS OF CELL MEMBRANE
what two kinds of proteins are present
- Proteins: transmembrane or one surface only
integral vs extrinsic proteins
COMPONENTS OF CELL MEMBRANE
what are the 7 functions that the proteins have
aquaporins:
– Ion ____:
– ______ molecules:
– Membrane ____: drug, NT, hormones
– _____-marker _____: Identify the specific place where the drug binds
– Membrane-____ enzymes: AchE
– Cell _____ ____ (CAMs): cell to cell adhesion, cadherins and integrins
Proteins: several types for specific functions
– Aquaporins: transport water molecules
– Ion channels:
– Carrier molecules:
– Membrane receptors: drug, NT, hormones
– Docking-marker acceptors: Identify the specific place where the drug binds
– Membrane-bound enzymes: AchE
– Cell adhesion molecules (CAMs): cell to cell adhesion, cadherins and integrins
COMPONENTS OF CELL MEMBRANE
where are carbohydrates present
what are the 2 types/what other substance can it be attached to
what is the function of carbohydrates
Carbohydrates: present on outer surface only
– Glycolipids:
– Glycoproteins:
– Function: self-identity markers
STRUCTURE OF CELL MEMBRANE
for the flud mosaic model, what is the dark and light regions
- The fluid mosaic (has other things) model: Tri-laminar structure
dark line: head
light space: tails
CELL-CELL ADHESIONS
what is the hieracrchy order from cell to organism
what is the ECM and what is it secreted by
what are the 3 specialized cell junctions
cell adhesion occurs when cells are what kind of distance away from each other
for cell adhesion, what type of system do the proteins use to adhere together
cells to tissues to organs to the system to organism
Extracellular matrix (biological glue secreted by cells)
- Specialized cell junctions:
– Desmosomes
– Tight junctions
– Gap junctions - Cell adhesion molecules:
– Occurs between cells in close proximity
– Loop and hook-shaped proteins that “velcro” together
EXTRACELLULAR MATRIX
what is it also known as and where is it present in
what is it a meshwork of
what are the 3 kinds of substances that are found
for collagen, what is it similar to, what does it provide, how much of the ECM consists of it
for elastin, what is it similar to and what can be an example of it
for fibronectin, what does it promote
AKA Interstitial fluid, present in intercellular space
Meshwork of fibrous proteins in a watery gel
– Collagen: cable-like, provides tensile strength (pulled apart w/o breaking) - makes up 50% of ECM
– Elastin: rubber-like protein, ex: lungs expand then contract
– Fibronectin: promotes cell adhesion
the cell membrane has 3 components, what are they
lipids
proteins
carbohydrates
what are the 3 kinds of lipids of the cell membrane
sphingolipids
phospholipids
cholesterol
phospholipids of the cell membrane
what are the two parts of it
what is the charge of the head group and why is it that charge
what is the charge of the tails
in H2O, how do phospholipids arrange, are there strong bonds why or why not, what does that allow for, and for what kind of cells
what is the fluid in the bilayer called
what is the fluid out of the bilayer called
can lipid soluble substances pass through
can H2O pass through the bilaer easily
phospholipid head, hydrocarbon tail
head group is charged due to the phosphate (PO4) molecule so it is negatively charged - it is hydrophilic or lipophobic
tails: uncharged so electrically neutral - it is hydrophobic or lipophilic
the phospholipid in H2O aligns into a bilayer-lipid bilayer (2 layers). It has no strong bonds which allows it to be fluid (provides fluidity) like RBCs or muscle cells that change shape which the bilayer makes possible
in the bilayer = intracellular fluid (ICF)
out of the bilayer = extracellular fluid (ECF)
lipid soluble can pass through easily
H2O soluble cannot pass through easily (hinder or inhibit)
cholesterol of the cell membrane
is the head group polar or nonpolar, what about the tail
where does it orient
what does it prevent of the phospholipids and thus prevents what from happening. What else does it provide
where do we get cholesterol from, if we not get from there where can out body synthesize it
where is cholesterol only found in and not some where else
head group - polar so water-loving or hydrophilic or lipophobic
tail - nonpolar, lipophilic or hydrophobic
orients between phospholipids
prevents tight packing of phospholipids and thus prevents crystallization and increases fluidity. Also provides stability to the membrane
gets cholesterol from diet. If you do not get it from the diet, the liver will synthesize it
cholesterol is only in animal cells and not in plant cells
sphingolipids of the cell membrane
how are they different from phospholipids and thus what can they form, what is contained there
where can this be found
similar to phospholipids but have longer fatty acid tails so they form lipid rafts that contain receptors for cell signaling
found in a cave-like structure of cell membrane
proteins of the cell membrane
where in the cell membrane do transmembrane proteins pass through and thus what kind of regions does it have, what is another name for transmembrane proteins
what is the name of the proteins located on one side of the membrane, what kind of regions does it have
what is another kind of integral or intrinsic proteins, how do they look
Transmembrane proteins: pass directly through the membrane - and have polar and non-polar regions. AKA integral or intrinsic proteins
extrinsic or peripheral proteins: have mostly polar regions - located on one side of the membrane
another kind of integral or intrinsic protein are on one side of the membrane connected by a strong bond indicated by a squiggly line
transmembrane proteins have both hydrophilic and hydrophobic regions
true
false
true
aquaporins
what are they
what are they made of and what do they allow the movement of from where
water pores
composed of proteins and allow movement of H2O through membrane from outside to inside and vice versa
channels
what are they for
what do they only allow the movement for
what must the size of the ion be
what are leak channels and do they close
what are gated channels and are they regulated, if so by what kind of molecule and what kind of drug
can they be open or closed to let what kind of molecules through
what are they specific for
for ions
allow movement of ions only
ion size: <0.8 nm diameter
leak channels: always open so ions can move freely
gated channels: regulated by neurotransmitters and drugs like CCB
- can be open or closed only to let certain ions through
specific for certain ions: Na, K, Cl, Ca
- Na cannot go through K channels and etc
carriers
what does it transport
what can it transport and at what size
is it specific or nonspecific
- can the amino acid transporter transport both glycine and glucose
what ions do thyroid cells use
transports proteins
glucose, amino acids
transport H2O soluble substances >0.8 nm diameter
specific - transport 1 substance at a time or a closely regulated substance
- ex: amino acid carrier can transport glycine, alanine but not glucose
thyroid cells use iodine
carbohydrates
what kind of molecules are they
what can they be attached to and what would those molecules be called
what is markers identification needed for
if this goes wrong what does it lead to
sugar molecules
can be proteins or lipids
attached to protein: glycoprotein
attached to lipid: glycolipid
markers identification - needed for embryonic development
if wrong then leads to cancer
EXTRACELLULAR MATRIX
Secreted by cells, important for their functioning
- Pathway for the diffusion of water-soluble substances
- Regulates behavior and functions of the cells:
– Amount & composition of ECM varies with cell type - Can become highly specialized for specific functions:
– Examples: cartilage, tendons, hardness of bones & teeth etc. - all of these are ECM that are specialized
DESMOSOMES/ADHERING JUNCTIONS
cells are connected by “Spot rivets” which are composed of:
* Plaque
* Glycoprotein filaments
* Keratin filaments
* Present in skin, heart, uterus and any other organ that needs to stretch
TIGHT/IMPERMEABLE JUNCTIONS
Cells adhere firmly, seals formed at kiss sites by junctional proteins
- Found b/w epithelial cells, separate 2 compartments of diverse chemical compositions e.g., intestines, kidneys
- Passage of materials takes place through cells, not between cells, via channels and carriers
GAP/COMMUNICATING JUNCTIONS
Gaps/tunnels between cells
- Connexons: six subunits in a hollow tube-like structure, 2 connexons join together
- Only small particles pass, like ions!
- Present in electrically active
cardiac/smooth muscle - Enables synchronized action
- Metabolic/communication link
MEMBRANE TRANSPORT
Essential for homeostasis: nutrients in, wastes out
- Plasma membrane is selectively permeable
- Factors affecting membrane permeability:
– Lipid solubility: can cross through the membrane
– Particle size: < 0.8 nm - can cross membrane thru channels, > 0.8 nm will use carriers - Forces are required for membrane transport
– Passive force: no energy expenditure by cells for transport, no energy required
– Active force: energy (ATP) expenditure by cells for transport
permeable: substance can cross
impermeable: substance cannot cross
water solubility is also needed because
1- The phospholipid head is polar
2- blood is aqueous and will transport water soluble substance
MEMBRANE TRANSPORT
unassisted: no channels or carriers involved
- diffusion
- osmosis
- movement along an electrical gradient
assisted
- vesicular transport
- carrier mediated
vesicular transport
- endocytosis
- exocytosis
carrier mediated
- facilitated diffusion
- active transport
active transport
- primary active transport
- secondary active transport
caveolae: membrane transport and signal transduction - sphingolipids rafts found in caveolae
diffusion
occurs from side A to B until there is equal concentrations on both side and reaches equilibrium
no net diffusion
if a substance can permeate the membrane
if the membrane is impermeable to a substance
diffusion continues until sides A & B have the same concentrations
this process is dynamic so if 1 molecule moves from A to B, one molecule moves from B to A
DIFFUSION
how does each factor affect the rate of net diffusion:
increase in:
- concentration gradient of substance
- surface area of membrane
- lipid solubility
- molecular weight of the substance
- distance (thickness)
Rules/Properties of Diffusion
– Occurs only if substances can cross the membrane
– Always occurs from the area of high to low concentration
– No energy required, a passive mechanism, e.g.O2-CO2
- concentration gradient of substance: increase rate
- surface area of membrane: increase
- lipid solubility: increase rate
- molecular weight of substance: decreased rate
- distance (thickness): decrease rate
ELECTRICAL GRADIENT
EG: charge difference between adjacent areas
- Promotes movement towards the opposite charge
- Electrical and concentration gradient = electrochemical gradient
Opposite charges attract
OSMOSIS
Net diffusion of water down its own concentration gradient separated by the semi-permeable membrane
pure water: 100% water concentration, 0% solute concentration
solution: 90% water concentration, 10% solute concentration
area with higher H2O concentration lower solute concentration flows to area with lower H2O concentration higher solute concentration
similar to diffusion but now movement of H2O
OSMOSIS
Q on hydrostatic pressure description
Membrane (permeable to both water and solute)
- Water concentrations equal
* Solute concentrations equal
* No further net diffusion
* Steady-state exists
Membrane (permeable to H2O but impermeable to solute)
- Water concentrations equal
* Solute concentrations equal
* No further net diffusion
* Steady-state exists
- there was more solute on one side so water moved to make both sides equal but the solute did not move!
Membrane (permeable to H2O but impermeable to solute)
- Water concentration not equal
* Solute concentration not equal
* Osmosis ceases when osmotic
pressure is exactly balanced by opposing hydrostatic pressure
OSMOSIS
Important for water movement in/out of cells
– Intravenous administration, eye drops, etc.
* Tonicity: conc. of non-penetrating solutes
* Osmolarity: concentration of non-penetrating and penetrating solutes
normal cell conditions:
300 mOsm
0.9% NaCl
hypotonic solution
<300 mOsm
<0.9% NaCl
hypertonic solution
>300 mOsm
>0.9% NaCl
tonicity is much higher
CARRIER-MEDIATED TRANSPORT
Utilize carriers: membrane-spanning proteins - so these are integral proteins not extrinsic proteins
Able to flip-flop, a reversible change in shape
Binding sites of substance on carriers exposed alternatively to either side of the membrane
on binding with molecules to be transported, the carrier changes its conformation
what are the 3 types of specialized cell junctions and their alternative names
desmosomes aka adhering junctions
tight jxns aka impermeable junctions
gap jxn aka communicating junction
desmosomes
aka adhering junctions
each cell has a plaque and the cells connect by glycoprotein filaments that are attached to the plaque of each cell
these form spot rivets
rivets mean joining sheets together
desmosomes form spot rivets and hold cells together
keratin is also within the cells and is attached to the plaques on the edges of the cells
you will find desmosomes in tissues that have to stretch like the heart and uterus. Desmosomes make sure that the cells will not rupture and make sure that the cells split apart
tight junctions
aka impermeable junctions
these are found in epithelial cells to prevent substances from the blood from moving directly to the ECM rather than going into the cells and being absorbed which is what we want!
they are made of claudins
claudins mean to close
the tight function fuse together at the kiss sites of the cell
gap junctions
needed for cell-to-cell communication
these proteins are connexons
connexons have 6 sections and have a small diameter
2 connexons link together two cells
ions flow thru this due to speed and efficiency
gap jxns allow all the cells to be stimulated simultaneously when is needed for uterus contraction for example
the strongest junction between cells is via
A. desmosomes
B. tight junctions
C. gap junctions
A. desmosomes
- these prevent cells from coming apart so they are the strongest kind of specialized cell junction
- adhering junctions
which of the following transport mechanism(s) occur from higher conc. to lower conc.
A. simple diffusion
B. facilitated diffusion
C. primary active transport
D. secondary active transport
A. simple diffusion
B. facilitated diffusion
which of the following processes required energy directly
A. simple diffusion
B. facilitated diffusion
C. primary active transport
D. secondary active transport
C. primary active transport
when 2 substances move across the PM in opposite directions, it is called
symport
antiport
uniport
primary active transport
secondary active transport
antiport
a carrier molecule is not needed for which of the following
A. simple diffusion
B. facilitated diffusion
C. primary active transport
D. secondary active transport
A. simple diffusion
the movement of water across the membrane depends on the
osmotic pressure
hydrostatic pressure
electrical gradient
osmotic pressure
movement of ions across the cell membrane along the electrical gradient is a/an ____ process
passive
active
passive because opposite charges attract
carrier-mediated transport
types:
uniport
symport
antiport
transported molecule
cotransported ion
uniport: transport 1 substance
symport: transport 2 substances in the same direction
antiport: transport 2 substances in opposite directions
CARRIER-MEDIATED TRANSPORT
Specificity and selectivity:
– One carrier for one (or closely related) substance
– Different cells may have different carriers. if can transport glycine the can transport alanine but not glucose. iodine is in thyroid gland
– Dysfunction leads to diseases: such as cystinuria which is cysteine in urine and can lead to urinary stones
- Saturation:
– Finite number of carriers, affinity/number can be regulated – Tm = transport maximum (rate-limiting factor in transport) - as [ ] increases, once all the carriers are saturated then Tm is reached. This determines how much substance gets transported with time -> rate limiting step
insulin can affect amount of glucose in cell - Competition:
– Occurs when carrier transfers closely related substances
– Reduces the rate of transfer of each substance transported
– Does not affect the total amount of transfer, so no matter what the total number transported is the same!
facilitated diffusion
uses the carrier to transport H2O soluble or large or charge molecules
while simple diffusion has no carriers needed cause it transports lipid soluble
1 - carrier protein takes conformation in which solute binding site is exposed to region of higher concentration
2 - solute molecules bind to a carrier protein
3 - carrier protein changes conformation so that the binding site is exposed to regions of lower concentration
4 - transported solute is released and carrier protein returns to conformations in step 1
molecules go from an area of high concentration to an area of low concentration
this continues until the [ ] gradient is at equilibrium
FACILITATED DIFFUSION - no energy needed
Example: transport of glucose into the cell
- Movement of a substance from high to low concentration
- Does not require energy
graph:
line A: steadily increases - this is simple diffusion, transport will occur as long there is a [ ] gradient
line B: steadily increases, then plateaus: this is facilitated diffusion, increases then reaches saturation which happens when a finite number of carriers is reached
ACTIVE TRANSPORT
Movement of a substance from low to high concentration – Example: uptake of iodine in thyroid gland cells
Two types:
– Primary active transport:
* ATP required directly; carrier splits ATP (has ATPase activity)
* Requires energy (ATP) to change the shape of the carrier
* AKA “pumps” (hydrogen ion pump, Na-K-ATPase pump)
– Secondary active transport:
* ATP not required directly; carrier lacks ATPase activity
ATPase splits ATP into ADP, Pi and energy
PRIMARY ACTIVE TRANSPORT
1 - pump has 3 high-affinity sites for Na+ and 2 low-affinity sites for K+ when exposed to ICF
- normal Na+ concentration gradient: out to in
- normal K+ concentration gradient: in to out
2 - when 2 Na+ from ICF (where Na+ concentration is low) binds to the pump, it splits ATP into ADP plus phosphate; the phosphate group binds to the pump
3 - phosphorylation causes the pump to change conformation so that Na+ binding sites are exposed to the opposite sides of the membrane and 3 Na+ are released to ECF (where Na+ concentration is high) as the affinity of Na+ binding sites greatly decreases
4 - The change in shape also exposes the pump’s binding sites for K+ to ECF and greatly increases the affinity of K+ sites
5 - when 2 K+. from ECF (where K+ concentration is low) binds to the pump, it releases the phosphate group. Dephosphorylation causes the pump to revert to its original conformation
6 - 2 K+ are released to ICF (where K+ concentration is high) as the affinity of K+ binding sites markedly decreases during a change in shape. At the same time, the affinity of Na+ binding sites greatly increases, returning the process to step 1
uses carrier molecule to transport from low [ ] to high [ ]
normal conditions:
[Na+] higher outside, lower inside
[K] higher inside, lower outside
but now:
we want as few Na+ inside as possible so Na+ is pumped from [low] which is inside the cell to [high] which is outside the cell
and now we also want to pump the K+ inside the cell
Na+ K+ ATPase PUMP
Establishes Na+ and K+ concentration gradients: electrical signals
- Regulates cell volume by controlling tonicity - if it stops then the Na+ will build up in cell and draw H2O in and cause cell to burst
- Energy (ATP) used also serves as secondary active transport of the Na+/Glucose symporter
secondary active transport
primary active transport:
- establishes Na+ concentration gradient from lumen to cell which drives the….
secondary active transport
- creating glucose concentration gradient from cell to blood used for facilitated diffusion. Increase affinity fro glucose
in detail:
lumen of the intestine:
- Na+ is high on the outiside
- [Na+] is low on the inside
- the Na+/K+ ATPase moves Na+ outside from the area of low [ ] to high
- SGLT moves glucose and Na+ from outside of the cell to inside in the same direction (symporter). This is the secondary active transport
- then glucose moves from inside the cell to the outside the cell when glucose is low in the blood
SECONDARY ACTIVE TRANSPORT
Co-transport of glucose and amino acids
- found in Intestinal and kidney cells, against concentration gradients
- Energy not expended directly, mediated by co-transport carriers
- Contain two binding sites, one for Na other for nutrient molecule
- Na binding affinity for glucose binding
- Transported out in blood by facilitated diffusion
SGLT2 - absorbs sugar from the urine so some diabetic drugs inhibits this carrier
VESICULAR TRANSPORT
Large polar molecules (hormones) and multi-molecular materials (bacteria) - cannot fit carrier protein
- Wrapped up in a membrane-enclosed vesicle
- Requires energy - active process
- Materials inside do not mix with cytosol, fuse with target membrane for transfer
*Two types: endocytosis and exocytosis
VESICULAR TRANSPORT
Endocytosis: substances transported into the cell, can fuse with lysosome or be released on the other side of the cell
– Pinocytosis (non-selective uptake of ECF)
– Receptor-mediated endocytosis (selective uptake of large
molecule)
– Phagocytosis (selective uptake of multimolecular particle)
- Exocytosis: substances transported out of the cell, accomplish two major purposes
– Provides a mechanism for secreting hormones/enzymes (large polar molecules)
– Enables cell to add specific membrane components: carriers, channels, receptors - Rate of endocytosis = rate of exocytosis
VESICULAR TRANSPORT
exocytosis: a secretory vesicle fuses with the plasma membrane, releasing the vesicle contents to the cell exterior. The vesicle membrane becomes part of the plasma membrane
endocytosis: materials from the cell exterior are enclosed in a segment of the plasma membrane that pockets inward and pinches off as an endocytic vesicle
TYPES OF ENDOCYTOSIS
pinocytosis
1 - solute molecules and water molecules are outside the plasma membrane
2 - membrane pockets inward enclosing solute molecules and water molecules
3 - pocket pinches off as endocytic vesicle containing a sample of ECF
receptor-mediated endocytosis
1 - substances attach to membrane receptors
2 - membrane pockets inward
3 - pocket pinches off as endocytic vesicle containing the target molecule
phagocytosis
1 - pseudopods begin to surround prey
2 - pseudopods close around prey
3 - prey is enclosed in an endocytic vesicle (phagosome) that sinks into the cytoplasm
4 - lysosome fuses with vesicle, releasing enzymes that attack material inside the vesicle
carriers always transport a substance into the cell
true
false
false
membrane transport Is faster by
ion channels
carrier proteins
ion channels
carriers can transport ions]
true
false
true - the Na+/K+ pump
drugs can also be transported across the cell membrane via carrier proteins
true
false
true
carrier mediated transport can be active or passive
true
false
true - facilitate diffusion and 1 or 2 active transport
Na-K-ATPase pump:
I: is an example of primary active transport
II: is an example of antiport transfer
III: can help in the movement of glucose across into the intestinal membrane
I
III
I & II
II & III
I, II & III
I, II, III
if the transport of a substance across the cell membrane does not require energy, the transport must be occurring via unassisted means
true
false
false - you can have facilitated diffusion which is via assistance from carrier proteins
