Chapter 6.3-6.4

Question 1

what are the 3 types of membrane proteins?

Answer 1

1. membrane-bound receptors
2. membrane-bound metabolic enzymes
3. membrane transport proteins

Question 2

what do membrane transport proteins do?

Answer 2

move polar molecules across the hydrophobic membrane

Question 3

list and describe the 2 ways that membrane transport molecules move molecules across hydrophobic membranes and the energy dependence of each

Answer 3

1. passive: down concentration gradient; energy independent
2. active: up concentration gradient; energy dependent

Question 4

give 2 example of passive membrane transporters

Answer 4

1. gramicidin A; an antibiotic polypeptide
2. porins; ion channels made of beta barrel proteins

Question 5

describe the structure of porin passive transport proteins

Answer 5

alternating hydrophobic and hydrophilic residues

Question 6

describe how the structure of membrane transport enables their function and give an example

Answer 6

helices form substrate-selective channels; like the K+ channel protein,which allows for passive transport of K+ and excludes other ions like Na+

Question 7

what do aquaporins allow for?

Answer 7

passive transport of water

Question 8

what are the 3 types of active transporters? and what are the 2 main categories of the 3 types?

Answer 8

either primary or secondary
1. primary active transporter
2. secondary active antiporter
3. secondary active symporter

Question 9

describe how primary active transporters work

Answer 9

ATP turnover drives the movement of molecules up their concentration gradient

Question 10

describe how secondary active antiporters work

Answer 10

molecules moving down their concentration gradients drive other molecules up their concentration gradients (opposite directions)

Question 11

describe how secondary active symporters work

Answer 11

molecules moving down their concentration gradient drive other molecules moving up their concentration gradients (in same direction)

Question 12

what does the Na+/K+ ATPase membrane protein do? generally and specifically

Answer 12

creates membrane potential important for neurons by pumping 3 Na+ out of the cell and bringing 2 K+ into the cell (both against concentration gradients)

Question 13

what drives the conformational shift of the Na+/K+ ATPase membrane protein?

Answer 13

ATP hydrolysis

Question 14

what is the Na+/I- secondary symporter essential for? generally then specific ion movement

Answer 14

essential for thyroid hormone biosynthesis by bring one I- and 2 Na+ into the cell

Question 15

what is the Na+/I- secondary symporter coupled to?

Answer 15

coupled to the Na+/Kt ATPase transporter

Question 16

what does SERCA stand for?

Answer 16

sarco/endoplasmic reticulum Ca2+ ATPase

Question 17

what is SERCA responsible for?

Answer 17

uptake of Ca2+ from cytosol into sarcoplasmic reticulum lumen

Question 18

where is SERCA abundant and as what?

Answer 18

abundant in animal muscle cells as a Ca2+ transporter

Question 19

what kind of transporter is SERCA?

Answer 19

a primary active transporter

Question 20

what does SERCA promote?

Answer 20

muscle relaxation

Question 21

what is phospholamban?

Answer 21

a protein that attaches to SERCA when dephosphorylated, preventing SERCA from working

Question 22

what deactivates phospholamban and what is the result?

Answer 22

phosporylation deactivates phospholamban, causing it to dissociate from SERCA and allow muscle contraction to begin

Question 23

what 2 things phosphorylate phospholamban and where?

Answer 23

1. adrenaline phosohorylates Ser16 by protein kinase A
2. high Ca2+ phosphorylates Thr17 by Ca2+/calmodulin kinase II

Question 24

give the 4 steps of the SERCA mechanism

Answer 24

1. ATP hydrolysis and phosphorylation of Asp351 releases H+ and binds Ca2+ in the transmembrane helices, causing a conromfationa change
2. ADP dissociated, casuing M2 to open toward the luminal side and release Ca2+
3. ATP binding repositions M2 to trap H+
4. Asp351 dephosphorylates

Question 25

draw a muscle fiber, label all 4 parts

Answer 25

parts are 1. actin filament 2. myosin filament 3. titin 4. z disk go draw this!!

Question 26

what does titin function as?

Answer 26

a spring

Question 27

give an analogy for contraction as ,yosin heads pull actin

Answer 27

actin is like a rope; it does not change length when pulled but moves relative to myosin

Question 28

what changes length during muscle contraction?

Answer 28

titin only! is like a spring that can compress and decompress

Question 29

what are myoblasts?

Answer 29

large fused muscle cells/super cells

Question 30

what do myoblasts contain? (3)

Answer 30

1. many nuc;ei 2. share sarcolemma (plama membrane) 3. share bundle of small fibers (myofibrils)

Question 31

what are myofibrils composed of and what are they organized into?

Answer 31

composed of nyosin and actin; organized into thin and thick filaments

Question 32

describe myosin (3)

Answer 32

1. make up thick filaments 2. arranged so fibrous tails are in the middle and 3. gloubular heads are at the ends and grab the thin filament

Question 33

describe actin (2)

Answer 33

1. make up thin filaments 2. bound to troponin and tropomyosin

Question 34

what are the 2 kinds of bands in the sliding filament muscle model? describe

Answer 34

1. A band: stretches from myosinhead to myosin head; does NOT change in length during contraction 2. 2 I bands shorten as muscles contract as titin tightens

Question 35

what is troponin? describe the 3 binding sites

Answer 35

a complex of 3 domains 1. TnT: binds troponin 2. TnI: inhibits myosin from binding to actin 3. TnC: binds Ca2+

Question 36

describe the mechanism of muscle contraction (3)

Answer 36

1. in relaxed muscle, myosin binding sites on actin are blocked by tropomyosin 2. Ca2+ binding to TnC inudces a conformational change in troponin and tropomyosin that unvocers the myosin binding site on actin 3. myosin heads bind to actin and initiate muscle contraction

Question 37

describe calcium control of muscle contraction and relaxation (5)

Answer 37

1. Ca2+ binding to troponin (TnC) uncovers myosin binding sites on actin thin filaments 2. Pi release induces the power stroke, which pulls the actin filament toward the center 3. ADP release empties the nucleotide binding site in myosin 4. ATP binding causes myosin to dissociate from actin 5. ATP hydrolysis induces the recovery conformation

Question 38

what causes muscle contraction?

Answer 38

the relative movement of filaments

Question 39

how does the power stroke occur?

Answer 39

ADP and Pi are both negatively charged, the release of Pi releases energy = power stroke

Question 40

what is need to initiate and continue muscle contraction and why?

Answer 40

1. Ca2+ needed to start contraction 2. ATP needed to provide energy to continue contraction

Question 41

what does SERCA do? generally

Answer 41

pumps Ca2_ out of sarcoplasm into sarcoplasmic reticulum lumen to keep Ca2+ away from troponin to prevent contraction and allow for relaxation