Chapter 10 pt 2

Question 1

Transbilayer Movement of Lipids Requires _____________

Answer 1

Catalysis

Question 2

Proteins called _________ , floppases, and scramblases facilitate the transbilayer movement (translocation) of individual lipid molecules, providing a path that is energetically more favorable and much faster than the uncatalyzed movement

Answer 2

flippases

Question 3

________________ moves PE & PS from outer membrane to to interior cytosolic leaflet (interior membrane)

Answer 3

Flippase

Question 4

__________ moves phospholipids from cytosolic to outer leaflet

Answer 4

Floppase

Question 5

___________ moves lipids in either direction toward equilibrium

Answer 5

Scramblase

Question 6

______________ movement from one leaflet to the other is very slow, but (b) lateral diffusion
within the leaflet is very rapid, requiring no catalysis. (c) Three types of phospholipid translocators in the plasma membrane. PE is
phosphatidylethanolamine; PS is phosphatidylserine.

Answer 6

Uncatalyzed

Question 7

_____________ and Cholesterol Cluster Together in
Membrane Rafts

Answer 7

Sphingolipids

Question 8

Membrane microdomains

Answer 8

Stable associations of sphingolipids and cholesterol in the outer leaflet produce a microdomain, slightly thicker than other membrane regions, that is enriched with specific types of membrane proteins.

Question 9

__________ proteins are prominent in the outer leaflet of these rafts, and proteins with one or several covalently attached long-chain acyl groups are common in the inner leaflet. Inwardly curved rafts called caveolae are especially enriched in proteins called caveolins

Answer 9

GPI-anchored

Question 10

Proteins with attached ___________ groups tend to be
excluded from rafts.

Answer 10

prenyl

Question 11

__________________ moves substances across the semi- permeable barrier down or up the electrochemical gradient

Answer 11

Membrane Transport

Question 12

Summary of transporter types

Answer 12

Some types (ionophores, ion channels, and passive transporters) simply speed transmembrane movement of solutes down their electrochemical gradients, whereas others (active transporters) can pump solutes against a gradient, using ATP or a gradient of a second solute to provide the energy.

Question 13

Transport May Be __________or Active

Answer 13

Passive

Question 14

Simple diffusion

Answer 14

Solutes moving from a region of higher concentration to a region of lower concentration

Question 15

Transporters

Answer 15

Membrane proteins that act by increasing the rate of solute movement across membranes

Question 16

Passive transporter

Answer 16

Simply facilitate movement down a
concentration gradient, increasing the transport rate. This process is called passive transport or facilitated diffusion

Question 17

Active transporters (pumps)

Answer 17

Move substrates across a membrane against a
concentration gradient or an electrical potential, a process called active transport

Question 18

Primary active transporters

Answer 18

Use energy provided directly by a chemical reaction

Question 19

Secondary active transporter

Answer 19

Couple uphill transport of
one substrate with downhill transport of another

Question 20

Ion channel

Answer 20

Speed the passage of inorganic ions across membranes by a mechanism different from that of transporters. They provide an aqueous path
across the membrane through which inorganic ions can diffuse at very high rates. Most ion channels have a “gate” regulated by a biological signal. When the gate is open, ions move across the membrane, through the channel, in the direction dictated by the ion’s charge and the electrochemical gradient. (Transporter have alternating gates)

Question 21

Describe the energy changes accompanying the passage of a hydrophilic solute through the lipid bilayer of a biological membrane

Answer 21

1. In simple diffusion, the removal of the hydration shell is highly endergonic, and the energy
   of activation (ΔG‡) for diffusion through the bilayer is very high.
2. A transporter protein reduces the ΔG‡
   for transmembrane diffusion of the solute.
   It does this by forming noncovalent interactions with the dehydrated solute to replace the hydrogen bonding with water and by providing a hydrophilic transmembrane pathway.

Question 22

Spontaneous movement across the lipid membrane requires _______

Answer 22

Delta G

Question 23

_______________ provides transmembrane passage for ions and polar molecules

Answer 23

Facilitated Diffusion

Question 24

Pore/Channel & Transporters

Answer 24

1. No additional energy - Solutes diffuse
   down their electrochemical gradient

• Selectivity and transport rate mediated by
  protein structural properties or charge
• Pores & channels often non-saturable
• Transporters bind ligands and change
  shape; can be saturated like enzymes
• Can be gated or voltage dependent
• Ion-channel defects cause diseases
  (Cystic fibrosis (box 11-2), CTFR – Cl- channel)

Question 25

Transporters may be __________or active based on solute concentration and energy usage

Answer 25

passive (May be bidirectional and transport multiple ligands per cycle, Classified by mechanism of operation: uniport, symport or antiport)

Question 26

_________ uses concentration gradient and equilibrates solute in/out(related to transporters)

Answer 26

Passive

Question 27

____________requires energy to move against concentration gradient or charge (related to transporters)

Answer 27

Active

Question 28

Describe glucse transport into erythrocytes by GLUT1

Answer 28

1. Glucose in blood plasma binds to a stereospecific site on T1
   this lowers the activation energy for
2. A conformational change from glucose out?
   T1 to glucose in T2 effecting the transmembrane passage of the glucose.
3. Glucose is released from T2
   into the cytoplasm, and
   4 . the transporter returns
   to the T1 conformation, ready to transport another glucose molecule. Between
   the forms T1 and T2there is an intermediate form (not shown here) in which glucose is sequestered within the transporter, with access to neither side

Question 29

The amount of energy needed for the transport of a solute against a gradient can be calculated from the initial concentration gradient can be found with what formula?

Answer 29

Delta G= delta G’ + RT ln ([P]/[S]) (S is substrate & P is product, R is 8.315J/mol *K)

Question 30

When the “reaction” is simply transport of a solute from a region where its concentration is C1
to a region where its concentration is C2, no bonds are made or broken and ΔG′°
is zero. The free-energy change for transport, ΔGt, is then what?

Answer 30

Delta G (subscript t) = RT ln (C2/C1)

Question 31

When the solute is an ion, its movement without an accompanying counterion results in the endergonic separation of positive and negative
charges, producing an electrical potential; such a transport process is said to be ___________

Answer 31

electrogenic

Question 32

The energetic cost of moving an ion depends on the electrochemical potential, the sum of the chemical and electrical gradients:

Answer 32

Delta G (subscript t)= RN ln (C2/C1) + ZF delta phi (Z is the charge on the ion, F is the constant 96,480 J/V *mol), delta phi is the transmembrane potential (in volts)

Question 33

Spontaneous movement across the lipid membrane depends on what?

Answer 33

Depends on solute concentration & charge: Electrochemical gradient

• Chemical Potential: movement from high to low concentration
• Electrical Gradient: ions move to opposite charge; negative cell interior (-40 to -
  80 mV) add term for charged molecules (zFdelta phi)

(-z = ionic charge (+1 for Na+, -1 for Cl-, +2 for Ca2+
– F = Faraday constant (charge on mole of electrons) = 96,485 C/mol)
– D = membrane potential in V (Range up to -100 mV) 1 V = 1 J/C)

Question 34

______________ moves substances against the electrochemical gradient

Answer 34

Active transport

Question 35

Active transport

Answer 35

Substances transported against a concentration gradient – Endergonic

Question 36

What are the two types of active transport?

Answer 36

1. Primary active transport
2. Secondary active transport

Question 37

Primary active transport

Answer 37

ATP hydrolysis creates ion or molecule concentration gradient

Question 38

Secondary active transport

Answer 38

Existing electrochemical gradient powers a transport process

Question 39

What are some examples of cellular transport scheme?

Answer 39

1. Na+ out using ATP (primary active transport)
2. Na+ returns through transporter down conc. gradient
3. Glucose transport powered symport by Na+ traveling down its conc. gradient back
   into cell (Secondary Active Transport)

Question 40

__________ transport via symport with Na+ (secondary active) Driven by primary active transport of sodium & potassium
Na+-K+ pump maintains a low cellular [Na+]

Answer 40

Glucose

Question 41

Eicosanoids

Answer 41

Derived from arachidonic acid; oxygenated variations

Question 42

Isoprenoids

Answer 42

non-steroid derivatives; several vitamins A,K, E, retinoL

Question 43

______________ often derived from arachidonic acid (C20)

Answer 43

Eicosanoids (Signal molecules: bind to enzymes or proteins for response)

Question 44

__________ inhibits enyzme for prostaglandin synthesis: Analgesic and antipyretic

Answer 44

Aspirin

Question 45

Steroids are derived from____________

Answer 45

isoprene: isoprenoids (Four fused ring system: rigid and near planar3-six-membered rings (A,B,C) + 5-carbon D ring Squalene precursor)

Question 46

____________ is a precursor of steroid
hormone and bile salts (lipid digestion)

Answer 46

Cholesterol

Question 47

__________ has cellular membrane component & precursor

Answer 47

Cholesterol

Question 48

______________ link fatty acid to the hydroxyl group for transport/ storage & binding
to lipoproteins

Answer 48

Cholesterol Esters (Excess nonpolar cholesterol accumulates on blood vessel walls)