Cell Membranes

Front 1

what is the fluid-mosaic model?

Back 1

that membrane is considered a mosaic of lipid, protein, and carbohydrate molecules

Front 2

Why does a membrane properties that resemble a fluid?

Back 2

because lipids and proteins can move relative to each other within the membrane

Front 3

what are the main lipids in the lipid bilayer

Back 3

phospoglycerides, spingolipds, cholesterol

Front 4

What is an amphipathic molecule

Back 4

Has hydrophobic water fearing regions (facing in) and hydrophilic water loving region facing out

Front 5

where is there a high concentration of shpingolipds

Back 5

in the heart and brain. It is made up of spingosine, and amino alcohol

Front 6

what sterols are common for animals, fungases, plants?

Back 6

cholesterol (animal) Ergosterol (fungal) and stigmasterol (plant)

Front 7

what's the difference between exoplasmic face and cytosolic face of a membrane

Back 7

the cytosolic face faces the cytosol, the extoplasmic face faces away (towards an organelle or the outside of the cell)

Front 8

what persentage of genes encode membrane proteins

Back 8

25%

Front 9

What are two types of proteins bound to membranes

Back 9

Integral membrane proteins and peripheral membrane proteins

Front 10

What are two types of integral membrane proteins

Back 10

transmembrane proteins, one or more regions that are physically embedded in the hydrophobic region of the phoshpolipid bilayer

Lipid anchors: covalent attachment of a lipid to an amino acid side chain within a protein

Front 11

What are peripheral membrane proteins

Back 11

noncovalently bound to regions of integral membrane proteins that project out from the membrane, or they are bound to the polar head groups of phospholipids

Front 12

what is required to have a lipid move from one leaflet to the opposite leaflet?

Back 12

Flippase is required, and it requires ATP

Front 13

True/Falce: Most transmembrane proteins have membrane-spanning alpha helices.

Back 13

True, example is GlycophorinA, Bacteriorhodopsin, glycerol channel Glpf, also Aquaporins.

Front 14

how are porins constructed

Back 14

multiple beta strands in porins form membrane spanning barrels with hydrophilic interior and hydrophobic exterior

Front 15

what kind of attachments anchore some proteins to membranes?

Back 15

Covalent HC attachments. this can be on either the exoplamic side or cytasolic side

Front 16

what is glycosylation

Back 16

the process of covalently attaching a carbohydrate to a protein or a lipid.

Front 17

what two types of carbohydrates attached to lipids or proteins can serve as recognition signals for other cellular proteins

Back 17

glycolipid -- carboyhydrate to lipid
glycoprotein -- cargbohydrate to protein

Front 18

what rolls do glcolipds and glycoproteins serve

Back 18

can serve as recognition signals for other cellular proteins, and often playa role in cell surface recognition.
Protective effects as well, consisting of cell coat or glycocalyx, carbohydrate -rich zone on the cell surface shielding cell

Front 19

All transmembrane proteins and glycolipids are ____________ oriented in the bilayer

Back 19

assymetrically

Front 20

what are the Antigens on RBCs, Serum Antibodies, and what blood groups can blood group A receive?

Back 20

Blood group A has A antigens on RBCs has serum antiboldies Anti-B and can receive Blood types A and O

Front 21

what are the Antigens on RBCs, Serum Antibodies, and what blood groups can blood group B receive?

Back 21

Blood group B has B antigens on RBCs has serum antiboldies Anti-A and can receive Blood types B and O

Front 22

what are the Antigens on RBCs, Serum Antibodies, and what blood groups can blood group AB receive?

Back 22

Blood group AB have AB antigens on RBCs, has no serum antiboldies and can receive all Blood types

Front 23

what are the Antigens on RBCs, Serum Antibodies, and what blood groups can blood group o receive?

Back 23

Blood group o has o antigens on RBCs has serum antiboldies Anti-A and anti-b and can receive Blood types O

Front 24

How can Proteins be removed from membranes

Back 24

by detergents or high salt sol

Front 25

What are two examples of ionic detergents

Back 25

Sodium deoxycholate and sodium dodecylsulfate (SDS)

Front 26

What are two examples of nonionic detergents?

Back 26

Triton X-100 *polyoxyethylene(9.5)p-t-octylpheonol) and Octylglucoside (octyl-beta-b-glucopyranoside

Front 27

what is CMC?

Back 27

whena detergent is added micelles are formed if the concentration of detergent is above CMC, if the concentration of detergent is below CMC the proteins are dissolved but micelles are not formed

Front 28

What are four factors affecting membrane fluidity?

Back 28

Lipid composition
Length of fatty acyl tails
Presence of double bonds in the acyl tails
Presence of cholesterol

Front 29

How does lipid composition affect membrane fluidity?

Back 29

Influence of ER/Golgi on membrane composition.
Spingomyelin thicker/more gel-like vs. PL
Curvature of membrane

Front 30

How does the length of fatty acyl tails affect membrane fluidity?

Back 30

shorter acyl tails are less likely to interact, which makes the membrane more fluid

Front 31

How does the presence of double bonds in the acyl tails affect membrane fluidity?

Back 31

Double bond creates a kink in the fatty acyl tail, maing it more difficult for neighboring tails to interact and making the bilayer more fluid

Front 32

How does the presence of cholesterol affect the fulidity of membranes?

Back 32

Cholesterol tends to stabilize membranes
the effects depend on temperature
At warm temperatures (such as 37°C),
cholesterol restrains movement of
phospholipids
 At cool temperatures, it maintains
fluidity by preventing tight packing

Front 33

how did Larry Frye and Michael Edidin's experiment on lateral transport work?

Back 33

Larry Frye and Michael
Edidin conducted an
experiment that verified
the lateral movement of
membrane proteins
 Mouse and human cells
were fused
 Temperature treatment-
0°C or 37°C
 Mouse membrane protein
H-2 fluorescently labeled
 0°C cells- label stays on
mouse side
 37°C cells- label moves
over entire cell

1. add agents that cause mouse cell and human cell to fuse
2. lower the temperature to 0 and add a flourescently labeled antibody that recognizes the mouse H-2 protein in the plasma membrane. Observe with a flourescence microscope, H-2 protein is unable to move laterally and remains on one side of the fused cell,
Incubate cell at 37C then cool to O C and add a flourescently labeled antibody that recognizes the mouse H-2 protein in the plasma membrane. Observe with a flourescence microscope. due to lateral movement at 37C the mouse H-2 protein is on both sides of the fused cell

Front 34

What is FRAP

Back 34

Flourescens Recovery After Photo Bleaching.

Front 35

How does FRAP work?

Back 35

Proteins on the surface of a cell were covalently labeled with a flourescent chemical, a small area of cell photobleached leafing a white spot. Over time, bleached molecules within the white spot spread outward, and the white region filled in with red flourescent molecules. It indicates that proteins can laterally move in the membrane. 50% found mobile 50% immobile

Front 36

Why can't all integral membrane roteins move?

Back 36

10-70% of membrane proteins restricted by binding to components of the cytoskeleton, which restricts the proteins form moving laterally.
Also, membrane proteins may be attached to molecules that are outside of the cell, such as the interconnected network of proteins that forms the extracellular matrix

Front 37

What are six major functions of membrane proteins?

Back 37

Transport
Enzymatic activity
Signal transduction
Cell-cell recognition
Intercellular joining
Attachement to the cytoskeleton and extracellular matrix (ECM)

Front 38

Are plasma membranes asymmetrical or symmetrical? where is this determined?

Back 38

Asymmmetrical distribution of proteins, lipids, and associated carbohydrates in the plasma membrane is determined when the membrane is built by the ER and Golgi apparatus

Front 39

how is lipid conposition different in Exoplasmic and cytoplasmic leaflets?

Back 39

Spingomyelin, PC (dec fluidity) EXO
PE, PS, PI (inc fluidity) CYTO
Cholesterol equally distributed in both leaflets
Cholesterol/ Spingolipids cluster with sp. protein
in membrane microdomain: LIPID RAFTS
Phospholipases may influence
39

Front 40

is a transport protein needed for passive diffusion?

Back 40

no

Front 41

is energy used to move substances down the concentration gradient?

Back 41

no

Front 42

are gases permeable or impermeable

Back 42

permeable. CO2 N2 O2

Front 43

are small uncharged polar molecules permeable or impermeable

Back 43

Ethanol is permeable H20 is slightly permeable

Front 44

Large uncharged polar molecules, permeable or impermeable

Back 44

Glucose, fructose, impermeable

Front 45

ions -- permeable or impermeable

Back 45

K+Mg2+ Ca2+ Cl- HCO3_ HPO4 2-
Impermeable

Front 46

Charged polar molecules permeable or impermeable?

Back 46

Amino acids, ATP, glucose 6-phosphate, Proteins, nucleic acids, Impermeable

Front 47

what are three examples / types of membrane proteins that mediate transport of most molecules and all ions across biomembranes

Back 47

Na+/K+ Pump
K+ channel
Na+/lysine symporter

Front 48

Ion channels and transporters are examples of _____________ allowing membranes to be selectively ________

Back 48

transport proteins
selectively permeable

Front 49

Channels mediate __________ transport

Back 49

facilitated

Front 50

Channels may be gated or non gated, examples of gated channels are:

Back 50

– Ligand-gated
– Intracellular
regulatory proteins
– Phosphorylation
– Voltage-gated
– Mechanosensitive
channels

Front 51

How do transporters work?

Back 51

They are carriers, where the conformational change transports solute.

They are the principal pathway for the uptake of organic molecules, such as sugars, amino acids, and nucleotides,
transporters play a key role in export

Front 52

Transporters are the princapal pathway for the uptake of organic molecules such as:

Back 52

sugars, amino acids, and nucleotides

Front 53

what are three transporter types?

Back 53

Uniporter
symporter/cotransporter
Antiporter

Front 54

What is a uniporter

Back 54

a transporter type that has a single solute moving in one direction

Front 55

what is a symporter/cotransporter

Back 55

2 or more ions or molecules transported in same direction.

Front 56

what is an antiporter

Back 56

2 or more ions or molecules transported in opposite directions

Front 57

Channels generally allow transmembrane movement at rates greater or less than those typical of carriers

Back 57

orders of magnitude greater

Front 58

Do channels typically show more or less stereopecificity than carriers

Back 58

less

Front 59

how do pumps work?

Back 59

pumps couple conformationsal changes to an energy source, such as ATP-driven pumps,

Front 60

How do ATP-driven pumps work?

Back 60

ATP hydrolysis, a Ca2+ pump uses ATP to transport CA2+ from the cytosol to the ER lumen against a gradient.

ATP driven pumps can be uniporters, symporters, or antiporters.

They are active transport

Front 61

What is Active Transport?

Back 61

the movement of a solute across a membrane against its gradient from a region of low concentration to higher concentration

Front 62

Is active transport energetically unfavorable or favorable?

Back 62

unfavorable and requires the input of energy

Front 63

What is the difference between primary active transport and secondary active transport?

Back 63

Primary active transport
 Directly use energy to transport solute
 Secondary active transport
 Use pre-existing gradient to drive transport of solute

Front 64

What is co-transport?

Back 64

If one of the ions is going up its gradient and the other down, this is co-transport or inderect active transport

Front 65

transporters consist of carriers and channels, what types of carriers are there?

Back 65

Primary active transporters, secondary active transporters and passive transporters

Front 66

in simple diffusion are the following properties present or not:
-Requires specific protein
-Solute transported against its gradient
- Coupled to ATP hydrolysis
-Driven by movement of a cotranported ion down its gradient

What are examples of molecules transported through simple diffusion?

Back 66

simple diffusion does not require specific proteins,
solute is not transported against its gradient, is not coupled to ATP hydrolysis, is not driven by movement of a cotransprted ion down its gradient.

O2, CO2, Steroid hormones, many drugs

Front 67

in Facilitated Transport are the following properties present or not:
-Requires specific protein
-Solute transported against its gradient
- Coupled to ATP hydrolysis
-Driven by movement of a cotranported ion down its gradient

What are examples of molecules transported through facilitated transport?

Back 67

Facilitated transport requires specific proteins,
solute is not transported against its gradient, is not coupled to ATP hydrolysis, is not driven by movement of a cotransprted ion down its gradient.

Glucose and amino acids (uniporters): ions and water (channels)

Front 68

in Active Transport are the following properties present or not:
-Requires specific protein
-Solute transported against its gradient
- Coupled to ATP hydrolysis
-Driven by movement of a cotranported ion down its gradient

What are examples of molecules transported through active transport?

Back 68

Active transport requires specific proteins,
solute is transported against its gradient, it is coupled to ATP hydrolysis, is not driven by movement of a cotransprted ion down its gradient.

Ions, small hydrophilic molecules, lipids (ATP-powered pumps)

Front 69

in Cotransport are the following properties present or not:
-Requires specific protein
-Solute transported against its gradient
- Coupled to ATP hydrolysis
-Driven by movement of a cotranported ion down its gradient

What are examples of molecules transported through cotransport?

Back 69

Cotransport requires specific proteins,
solute is transported against its gradient, it is not coupled to ATP hydrolysis, it is driven by movement of a cotransprted ion down its gradient.

Glucose and amino acids (symporters); various ions and sucrose(antiporters)

Front 70

What do ion channels consist of?

Back 70

The channel consists of eight transmembrane helices (two from each of four identical subunits), forming a cone with its wide end toward the extracellular space. The inner helices of the cone line the
transmembrane channel, and the outer helices interact with the lipid bilayer. Short segments of each subunit converge in the open end of the cone to make a selectivity filter.

Front 71

How does the ion channel work?

Back 71

The ion path through the membrane begins (on the inner surface) as a wide, water-filled channel in which the ion can retain its hydration sphere.
About two-thirds of the way through the membrane, this channel narrows in the region of the selectivity filter, forcing the ion to give up its hydrating water molecules. Carbonyl oxygen atoms in the backbone of the selectivity filter replace the water molecules in the hydration sphere, forming a series of perfect coordination shells through which the K+ moves.

Front 72

which has a better fit in the potassium channel, K+or Na+?

Back 72

K+ does, the carbonyl oxygens are placed to bond with k_

Front 73

GLUT proteins 1-12 are transferred in Passive transport. is the channel hydrophilic or hydrophobic?

Back 73

hydrophillic.

Front 74

what are the Km difference between Glut 1, Glut 2, and Glut 3

Back 74

GLUT3 in neuronal cell- low Km like GLUT 1
GLUT2 in liver and pancreas Km 13x more, so their rate of glucose uptake changes after meals
 physiologically significant

Front 75

Uniport transport vs. simple diffusion

Back 75

Rate of facilitated diffusion is higher
Partition coefficient is irrelevant
Transporter are specific
# of transporters; kinetics

Front 76

when a carboyhydrate rich meal is injested what happens to the blood glucose level?

Back 76

it exceeds the usual conc between meals (about 5 mM),

Front 77

what happens to the excess glucose in the blood after a carbohydrate rich meal?

Back 77

excess glucose is taken up by the myocytes of cardiac and skeletal muscle (which store it as glycogen) and by adipocytes (which convert it to tryacyglycerols)

Front 78

what mediates the glucose uptake into myocytes and adipocytes?

Back 78

glucose updtake into myocytes and adipocytes is mediated by the glucose transporter GLUT4.

Front 79

What happens to GLUT4 between meals?

Back 79

between meals, some GLUT4 is present in the plasma membrane, but most is sequestered in the membranes of small intracellular vesicles.

Front 80

What triggers the movement of intracellular vesicles containing GLUT4 to the plasma membrane?

Back 80

Insulin released from the pancreas in response to high blood glucose triggers the movement of these intracellular vesicles to the plasma membrane

Front 81

define Tonicity

Back 81

tonicity is the ability of a solution to cause a cell to gain or lose water

Front 82

Define Iso tonic solution

Back 82

solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

Front 83

define hypertonic solution;

Back 83

solute concentration is greater than that inside the cell; cell loses water

Front 84

define hypotonic solution

Back 84

solute concentration is less than that inside the cell; cell gains water

Front 85

Peter Agre and his colleagues first identified a protein that was abundant in red blood cells and kidney cells, but not found in many other cell types.
Agre also discovered that osmosis Occurs More Quickly in Cells with Transport Proteins That Allow the Facilitated Diffusion of Water. What is the name of the protein that he discovered?

Back 85

CHIP28, a water channel.

Front 86

What was the experiment to test if CHIP28 is a water channel protein

Back 86

RNA polymerase and nucleotides in a test tube containing many copies of the chip28 gene, results in the synthesis of many copies of CHIP28 mRNA.
Inject the CHIP28 mRNA into frog oocytes. Wait several hours to allow time for the mRNA to be translated into CHIP28 protein, which is inserted into the plasma membrane.
Place oocytes into a hypotonic medium and observe under a light microscope, control with oocytes that have not been injected.
The oocytes with chip28 rupture in a hypotonic solution

Front 87

water crosses cell membranes by what two routes?

Back 87

simple diffusion through the lipid bilayer and through water channels called aquaporins

Front 88

are aquaporins bi directional? what directs the flow?

Back 88

bidirectional, in accordance with the prevailing osmotic gradient

Front 89

11 different members of aquaporins have been discovered in humans, what is Aquaporin-1?

Back 89

Aquaporin-1 is from human red bloood cells, it was the first to be discovered and is the best studied.

Front 90

Where is aquaporin 2 located? what regulates it?

Back 90

in the kidney, it is regulated by vasopresin levles.
When vasopressin levels are up the vesicles containing aquaporin fuse with the membrane, increasing water absorption.

Front 91

what is a mutation of the aquaporin cause?

Back 91

diabetes insipidus

Front 92

what is the structure of an aquaporin?

Back 92

each monomer has six transmembrane helical segments and two shorter helices, both contain the sequence Asn-Pro-Ala (NPA) .
The six transmembrane helices form the pore through the monomer, and the two short loops containing the NPA sequences extend toward the middle of the bilayer from opposite sides.
Thier NPA regions overlap in the middle of the membrane to form part of the specificity filter-- the structure that allows only water to pass.

Front 93

what is the mechanism for Aquaporins specificity?

Back 93

Conserved Asn form H-bond with transported water molecules. Hydrogen bonding + .28nm pore size prevent passage of ions.

Front 94

How are ATP-dependent ion pumps grouped into classes?

Back 94

based on transport mechanism, as well as genetic and structural homology

Front 95

Examples of ATP-dependent ion pumps

Back 95

P-class pumps
F-class (eg. F1F0-ATPase) and related V-class pumps.

Front 96

What are ABC transporters?

Back 96

ATP binding cassette transporters, which catalyze transmembrane movements of various organic compounds including amphipathic lipids and drugs

Front 97

of the following ions, which ones have a higher concentration in the cell than in the blood? K+, Na+, CL-, HCO3-, X-, Mg2+, Ca2+

Back 97

K+
X-

Front 98

What p-class ion pumps are found in plasma membranes of most animal cells? what kind of pump is it and what does it do?

Back 98

Na+,K+-ATPase is an antiport pump.
It catalyzies ATP-dependent transport of Na+ out of a cell in exchange for K+ entering

Front 99

What p-class antiport pump is found in the stomach and what and how does it do what it does?

Back 99

(H+, K+)-ATPase, involved in acid secretion in
the stomach is an antiport pump.
It catalyzes transport of H+ out of the gastric
parietal cell (toward the stomach lumen) in
exchange for K+ entering the cell.

Front 100

What p-class antiport pump is found in the endoplasmic reticulum and plasma membranes?

Back 100

Ca++-ATPases, catalyze ATP dependent transport of Ca++ away from the cytosol, into the ER lumen or out of the cell. antiporters transport protons in the opposite direction.

Ca++-ATPase pumps function to keep cytosolic Ca++ low, allowing Ca++ to serve as a signal

Front 101

what are the seven steps in how a Na/K pump functions?

Back 101

E1: Na+ enters E1 from interior and ATP binding from interior --> Phosphorylation of aspartate --> conformational change of E1 to E2, 2 K+ ions enter from exterior of cell --> Na+ is released to exterior as K+ binds --> dephosphorylation and conformational change --> K+ is release into the cytosol

and then the cycle repeats itslef.

digitalis works by inhibiting dephosphorylation of Na/K pump

Front 102

within the intestine glucose is transported from the extracellular fluid through the intestinal epithelium, microvillus in apical domain and into the intestinal lumin. How is this accomplished?

Back 102

Glucose and sodium are coupled, with a Na+ driven glucose symport, out of the intestinal lumin across the Apical membrane, and into the intestinal epithelium cytosol, where Glucose crosses the basal domain through a carrier protein GLUT2 mediating passive transport of glucose out of the intestinal epithelium through the Basolateral membrane into the blood. Sodium is being pumped out of the intestinal epithelium into the extracellular fluid/ blood by a Na+ k+ pump

Front 103

the blood has a pH of 7.2, and the Stomach Lumen has a pH of 1.0
How is the stomach Lumen's pH maintained?

Back 103

Parital cells acidify stomach contents while maintaining neutral cytosolic pH through a Cl-/HCO3 antiporter wwhich removes HCO3- from the cytosol and pushes Cl- from the blood into cytosol. A Cl- channel moves Cl- ions out of the cytosol into the stomach lumen. CO2 is brought in from the blood and with carbonic anhydrase the CO2 takes an OH- from H20, forming the HCO3_ for the Cl antiporter, and the H+ ion from H20 is pumped out with an H+/K+ ATPase into the stomach lumin. A K+ Channel moves K+ out of the cytosol into the Stomach Lumen where it is used in the H+/K=ATPase (which is powered with ATP