document_title: List of longest rivers of the United States (by main stem)

question_text: what is the biggest river in the usa

question_tokens: what is the biggest river in the usa

text: Table[edit]

text: The primary source for watershed and discharge data in the table below is Rivers of North America. Conflicting data from other sources, if the difference is greater than 10 percent, is reported in the notes. Discharge refers to the flow at the mouth.[n 1] In the "States, provinces, and image" column, the superscripts "s" and "m" indicate "source" and "mouth". Non-U.S. states appear in italics. Except in the "States, provinces, and image" column, abbreviations are as follows: "km" for "kilometer", "mi" for "mile", "s" for "second", "m" for "meter", and "ft" for "foot".

text:
Key

 River is not entirely within the United States.

 Watershed is not entirely within the United States.

text:
Longest main-stem rivers of the United States

#
Name
Mouth[5]
Length
Source
coordinates[11]
Mouth
coordinates[11]
Watershed
area[12]
Discharge[12]
States, provinces, and image[5][11]

1
Missouri River
Mississippi River
7003234100000000000♠2,341 mi
3,768 km[13]
45°55′39″N 111°30′29″W / 45.92750°N 111.50806°W / 45.92750; -111.50806 (Missouri River (source))[14]
38°48′49″N 90°07′11″W / 38.81361°N 90.11972°W / 38.81361; -90.11972 (Missouri River (mouth))
7005529353000000000♠529,353 mi2
1,371,017 km2[15]
[n 2]
7004691000000000000♠69,100 ft3/s
1,956 m3/s
[n 3]
Montanas, North Dakota, South Dakota, Nebraska, Iowa, Kansas, Missourim

2
Mississippi River
Gulf of Mexico
7003220200000000000♠2,202 mi
3,544 km[17]
[n 4]
47°14′22″N 95°12′29″W / 47.23944°N 95.20806°W / 47.23944; -95.20806 (Mississippi River (source))[18]
29°09′04″N 89°15′12″W / 29.15111°N 89.25333°W / 29.15111; -89.25333 (Mississippi River (mouth))
7006126000000000000♠1,260,000 mi2
3,270,000 km2[19]
[n 5]
7005650000000000000♠650,000 ft3/s
18,400 m3/s
Minnesotas, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, Louisianam

3
Yukon River
Bering Sea
7003197900000000000♠1,979 mi
3,185 km[6]
[n 6]
59°35′00″N 133°47′00″W / 59.58333°N 133.78333°W / 59.58333; -133.78333 (Yukon River (source))[20]
62°35′55″N 164°48′00″W / 62.59861°N 164.80000°W / 62.59861; -164.80000 (Yukon River (mouth))[21]
7005324000000000000♠324,000 mi2
839,200 km2[22]
[n 7]
7005224000000000000♠224,000 ft3/s
6,340 m3/s
British Columbias, Yukon Territory, Alaskam

4
Rio Grande
Gulf of Mexico
7003175900000000000♠1,759 mi
2,830 km[23]
[n 8]
37°47′52″N 107°32′18″W / 37.79778°N 107.53833°W / 37.79778; -107.53833 (Rio Grande (source))[25]
25°57′22″N 97°08′43″W / 25.95611°N 97.14528°W / 25.95611; -97.14528 (Rio Grande (mouth))
7005340000000000000♠340,000 mi2
870,000 km2[26]
[n 9]
7003130000000000000♠1,300 ft3/s
37 m3/s
Colorados, New Mexico, Texasm, Chihuahua, Coahuila, Nuevo León, Tamaulipasm

5
Colorado River
Gulf of California
7003145000000000000♠1,450 mi
2,330 km[16]
[n 10]
40°28′20″N 105°49′34″W / 40.47222°N 105.82611°W / 40.47222; -105.82611 (Colorado River (source))[29]
31°48′57″N 114°48′22″W / 31.81583°N 114.80611°W / 31.81583; -114.80611 (Colorado River (mouth))[30]
7005248000000000000♠248,000 mi2
642,000 km2[10]
[n 11]
7003140000000000000♠1,400 ft3/s
40 m3/s
Colorados, Utah, Arizona, Nevada, California, Sonoram, Baja Californiam

6
Arkansas River
Mississippi River
7003144300000000000♠1,443 mi
2,322 km
[n 12]
39°15′30″N 106°20′38″W / 39.25833°N 106.34389°W / 39.25833; -106.34389 (Arkansas River (source))[32]
33°46′30″N 91°04′15″W / 33.77500°N 91.07083°W / 33.77500; -91.07083 (Arkansas River (mouth))
7005160200000000000♠160,200 mi2
414,910 km2[33]
7004355000000000000♠35,500 ft3/s
1,004 m3/s
Colorados, Kansas, Oklahoma, Arkansasm

7
Columbia River
Pacific Ocean
7003124300000000000♠1,243 mi[6]
2,000 km
[n 13]
50°13′00″N 115°51′00″W / 50.21667°N 115.85000°W / 50.21667; -115.85000 (Columbia River (source))[34]
46°14′39″N 124°03′29″W / 46.24417°N 124.05806°W / 46.24417; -124.05806 (Columbia River (mouth))[35]
7005279548000000000♠279,548 mi2
724,024 km2[36]
[n 14]
7005273000000000000♠273,000 ft3/s
7,730 m3/s
British Columbias, Washingtonm, Oregonm

8
Red River
Atchafalaya and Mississippi rivers
7003112500000000000♠1,125 mi
1,811 km
[n 15]
34°34′35″N 99°57′54″W / 34.57639°N 99.96500°W / 34.57639; -99.96500 (Red River (source))[40]
31°01′10″N 91°44′52″W / 31.01944°N 91.74778°W / 31.01944; -91.74778 (Red River (mouth))
7004655900000000000♠65,590 mi2
169,890 km2[41]
[n 16]
7004301000000000000♠30,100 ft3/s
852 m3/s
[n 17]
Oklahomas, Texas, Arkansas, Louisianam

9
Snake River
Columbia River
7003104000000000000♠1,040 mi
1,674 km[16]
44°07′49″N 110°13′10″W / 44.13028°N 110.21944°W / 44.13028; -110.21944 (Snake River (source))[42]
46°11′10″N 119°01′43″W / 46.18611°N 119.02861°W / 46.18611; -119.02861 (Snake River (mouth))
7005108000000000000♠108,000 mi2
281,000 km2[43]
7004553000000000000♠55,300 ft3/s
1,565 m3/s
Wyomings, Idaho, Oregon, Washingtonm

10
Ohio River
Mississippi River
7002979000000000000♠979 mi
1,575 km[44]
40°26′34″N 80°01′02″W / 40.44278°N 80.01722°W / 40.44278; -80.01722 (Ohio River (source))[45]
36°59′12″N 89°07′50″W / 36.98667°N 89.13056°W / 36.98667; -89.13056 (Ohio River (mouth))
7005204000000000000♠204,000 mi2
529,000 km2[46]
7005308400000000000♠308,400 ft3/s
8,733 m3/s
Pennsylvanias, Ohio, West Virginia, Indiana, Illinois, Kentuckym

11
Colorado River of Texas
Gulf of Mexico
7002970000000000000♠970 mi
1,560 km[47]
32°40′47″N 101°43′51″W / 32.67972°N 101.73083°W / 32.67972; -101.73083 (Colorado River of Texas (source)))[48]
28°35′41″N 95°58′59″W / 28.59472°N 95.98306°W / 28.59472; -95.98306 (Colorado River of Texas (mouth))
7004399000000000000♠39,900 mi2
103,341 km2[49]
7003260000000000000♠2,600 ft3/s
75 m3/s
Texass, m

12
Tennessee River
Ohio River
7002935000000000000♠935 mi
1,504 km[50]
35°57′33″N 83°51′01″W / 35.95917°N 83.85028°W / 35.95917; -83.85028 (Tennessee River (source))[51]
37°04′02″N 88°33′53″W / 37.06722°N 88.56472°W / 37.06722; -88.56472 (Tennessee River (mouth))
7004408800000000000♠40,880 mi2
105,870 km2[52]
7004710000000000000♠71,000 ft3/s
2,000 m3/s
Tennessees, Alabama, Kentuckym

13
Canadian River
Arkansas River
7002906000000000000♠906 mi
1,458 km[16]
37°01′11″N 105°04′33″W / 37.01972°N 105.07583°W / 37.01972; -105.07583 (Canadian River (source))[53]
35°27′12″N 95°01′58″W / 35.45333°N 95.03278°W / 35.45333; -95.03278 (Canadian River (mouth))
7004471300000000000♠47,130 mi2
122,070 km2[54]
7003610000000000000♠6,100 ft3/s
174 m3/s
Colorados, New Mexico, Texas, Oklahomam

14
Brazos River
Gulf of Mexico
7002860000000000000♠860 mi
1,390 km[55]
33°16′07″N 100°00′37″W / 33.26861°N 100.01028°W / 33.26861; -100.01028 (Brazos River (source))[56]
28°52′33″N 95°22′42″W / 28.87583°N 95.37833°W / 28.87583; -95.37833 (Brazos River (mouth))
7004446200000000000♠44,620 mi2
115,566 km2[57]
7003880000000000000♠8,800 ft3/s
249 m3/s
Texass, m

15
Green River
Colorado River
7002760000000000000♠760 mi
1,230 km[58]
43°09′13″N 109°40′18″W / 43.15361°N 109.67167°W / 43.15361; -109.67167 (Green River (source))[59]
38°11′21″N 109°53′07″W / 38.18917°N 109.88528°W / 38.18917; -109.88528 (Green River (mouth))
7004449000000000000♠44,900 mi2
116,200 km2[60]
7003610000000000000♠6,100 ft3/s
172 m3/s
Wyomings, Colorado, Utahm

16
Pecos River
Rio Grande
7002730000000000000♠730 mi
1,175 km[61]
35°58′34″N 105°33′29″W / 35.97611°N 105.55806°W / 35.97611; -105.55806 (Pecos River (source))[62]
29°41′59″N 101°22′17″W / 29.69972°N 101.37139°W / 29.69972; -101.37139 (Pecos River (mouth))
7004440000000000000♠44,000 mi2
113,960 km2[63]
7001710000000000000♠71 ft3/s
2 m3/s
New Mexicos, Texasm

17
White River (Arkansas)
Mississippi River
7002720000000000000♠720 mi
1,159 km[64]
35°50′20″N 93°36′16″W / 35.83889°N 93.60444°W / 35.83889; -93.60444 (White River (source))[65]
33°57′05″N 91°04′53″W / 33.95139°N 91.08139°W / 33.95139; -91.08139 (White River (mouth))
7004278720000000000♠27,872 mi2
72,189 km2[66]
7004346000000000000♠34,600 ft3/s
979 m3/s
Arkansass, m, Missouri

18
James River
[n 18]
Missouri River
7002710000000000000♠710 mi
1,140 km[67]
47°28′53″N 99°51′32″W / 47.48139°N 99.85889°W / 47.48139; -99.85889 (James River (source))[68]
42°52′17″N 97°17′26″W / 42.87139°N 97.29056°W / 42.87139; -97.29056 (James River (mouth))
7004209420000000000♠20,942 mi2
54,240 km2[69]
7002854000000000000♠854 ft3/s
24.2 m3/s[69]
[n 19]
North Dakotas, South Dakotam

19
Kuskokwim River
Bering Sea
7002702000000000000♠702 mi
1,130 km[70]
63°05′16″N 154°38′33″W / 63.08778°N 154.64250°W / 63.08778; -154.64250 (Kuskokwim River (source))[71]
60°04′59″N 162°20′02″W / 60.08306°N 162.33389°W / 60.08306; -162.33389 (Kuskokwim River (mouth))
7004480000000000000♠48,000 mi2
124,319 km2[72]
7004670000000000000♠67,000 ft3s
1,900 m3/s
Alaskas, m

20
Cimarron River
Arkansas River
7002698000000000000♠698 mi
1,123 km[73]
36°54′24″N 102°59′12″W / 36.90667°N 102.98667°W / 36.90667; -102.98667 ("Cimarron River (source))[74]
36°10′14″N 96°16′19″W / 36.17056°N 96.27194°W / 36.17056; -96.27194 (Cimarron River (mouth))
7004195100000000000♠19,510 mi2
50,540 km2[75]
7003150000000000000♠1,500 ft3/s
42 m3/s
Oklahomas, m, Colorado, Kansas

21
Cumberland River
Ohio River
7002696000000000000♠696 mi
1,120 km[76]
36°50′42″N 83°19′26″W / 36.84500°N 83.32389°W / 36.84500; -83.32389 (Cumberland River (source))[77]
37°08′36″N 88°24′27″W / 37.14333°N 88.40750°W / 37.14333; -88.40750 (Cumberland River (mouth))
7004179300000000000♠17,930 mi2
46,430 km2[78]
7004410000000000000♠41,000 ft3/s
862 m3/s
Kentuckys, m, Tennessee

22
Yellowstone River
Missouri River
7002678000000000000♠678 mi
1,091 km[79]
43°59′18″N 109°55′45″W / 43.98833°N 109.92917°W / 43.98833; -109.92917 (Yellowstone River (source))[80]
47°58′42″N 103°58′56″W / 47.97833°N 103.98222°W / 47.97833; -103.98222 (Yellowstone River (mouth))
7004704000000000000♠70,400 mi2
182,336 km2[81]
7004128000000000000♠12,800 ft3/s
362 m3/s
Wyomings, Montana, North Dakotam

23
North Platte River
Platte River
7002665000000000000♠665 mi
1,070 km[82]
40°38′23″N 106°24′19″W / 40.63972°N 106.40528°W / 40.63972; -106.40528 (North Platte River (source))[83]
41°06′50″N 100°40′33″W / 41.11389°N 100.67583°W / 41.11389; -100.67583 (North Platte River (mouth))
7004348850000000000♠34,885 mi2
90,352 km2[82]
7002770000000000000♠770 ft3/s
21.9 m3/s
Colorados, Wyoming, Nebraskam

24
Milk River
Missouri River
7002625000000000000♠625 mi
1,005 km[6][n 20]
48°51′20″N 113°01′10″W / 48.85556°N 113.01944°W / 48.85556; -113.01944 (Milk River (source))[85]
48°03′26″N 106°19′07″W / 48.05722°N 106.31861°W / 48.05722; -106.31861 (Milk River (mouth))
7004223320000000000♠22,332 mi2
57,839 km2[86]
[n 21]
7002670000000000000♠670 ft3/s
18.9 m3/s
Alberta, Montanas, m

25
Ouachita River
Black River
7002605000000000000♠605 mi
974 km[87]
31°41′56″N 94°19′57″W / 31.69889°N 94.33250°W / 31.69889; -94.33250 (Ouachita River (source))[88]
31°37′53″N 91°48′25″W / 31.63139°N 91.80694°W / 31.63139; -91.80694 (Ouachita River (mouth))
7004248860000000000♠24,886 mi2
64,454 km2[89]
7004298000000000000♠29,800 ft3/s
843 m3/s
Arkansass, Louisianam

26
Saint Lawrence River
Gulf of Saint Lawrence
7002600000000000000♠600 mi
965 km[90]
[n 22]
44°05′55″N 76°23′28″W / 44.09861°N 76.39111°W / 44.09861; -76.39111 (St. Lawrence River (source))[92]
49°40′00″N 64°30′00″W / 49.66667°N 64.50000°W / 49.66667; -64.50000 (Saint Lawrence River (mouth))[93]
7005620000000000000♠620,000 mi2
1,600,000 km2[94]
[n 23]
7005440000000000000♠440,000 ft3/s
12,600 m3/s
[n 24]
New Yorks, Ontarios, Quebecm

27
Gila River
Colorado River
7002600000000000000♠600 mi
960 km[95]
33°10′47″N 108°12′22″W / 33.17972°N 108.20611°W / 33.17972; -108.20611 (Gila River (source))[96]
32°43′11″N 114°33′19″W / 32.71972°N 114.55528°W / 32.71972; -114.55528 (Gila River (mouth))
7004578500000000000♠57,850 mi2
149,832 km2[97]
[n 25]
7002210000000000000♠210 ft3/s
6 m3/s
[n 26]
New Mexicos, Arizonam

28
Sheyenne River
Red River of the North
7002591000000000000♠591 mi
951 km[98]
47°41′46″N 100°29′52″W / 47.69611°N 100.49778°W / 47.69611; -100.49778 (Sheyenne River (source))[99]
47°01′25″N 96°49′31″W / 47.02361°N 96.82528°W / 47.02361; -96.82528 (Sheyenne River (mouth))
7003880000000000000♠8,800 mi2
23,000 km2
[n 27]
7002288000000000000♠288 ft3/s
8.2 m3/s
[n 28]
North Dakotas, m

29
Tanana River
Yukon River
7002584000000000000♠584 mi
940 km
[n 29]
63°02′57″N 141°51′52″W / 63.04917°N 141.86444°W / 63.04917; -141.86444 (Tanana River (source))[103]
65°09′38″N 151°57′37″W / 65.16056°N 151.96028°W / 65.16056; -151.96028 (Tanana River (mouth))
7004440000000000000♠44,000 mi2
114,000 km2[104]
7004418000000000000♠41,800 ft3/s
1,185 m3/s
Alaskas, m

30
Smoky Hill River
Kansas River
7002576000000000000♠576 mi
927 km[98]
38°57′01″N 102°34′49″W / 38.95028°N 102.58028°W / 38.95028; -102.58028 (Smoky Hill River (source))[105]
39°03′36″N 96°48′04″W / 39.06000°N 96.80111°W / 39.06000; -96.80111 (Smoky Hill (mouth))
7004192600000000000♠19,260 mi2
49,900 km2
[n 30]
7003154200000000000♠1,542 ft3/s
43.7 m3/s
[n 31]
Colorados, Kansasm

31
Niobrara River
Missouri River
7002568000000000000♠568 mi
914 km[98]
42°49′15″N 104°38′50″W / 42.82083°N 104.64722°W / 42.82083; -104.64722 (Niobrara River (source))[107]
42°45′58″N 98°02′50″W / 42.76611°N 98.04722°W / 42.76611; -98.04722 (Niobrara River (mouth))
7004126000000000000♠12,600 mi2
32,600 km2[108]
7003170000000000000♠1,700 ft3/s
49 m3/s
Wyomings, Nebraskam

32
Little Missouri River
Missouri River
7002560000000000000♠560 mi
900 km[109]
44°32′25″N 104°59′57″W / 44.54028°N 104.99917°W / 44.54028; -104.99917 ("Little Missouri River (source))[110]
47°36′38″N 102°52′24″W / 47.61056°N 102.87333°W / 47.61056; -102.87333 (Little Missouri River (mouth))
7003831000000000000♠8,310 mi2
21,500 km2[111]
[n 32]
7002450000000000000♠450 ft3/s
13 m3/s[111]
[n 33]
Wyomings, Montana, South Dakota, North Dakotam

33
Sabine River
Gulf of Mexico
7002553000000000000♠553 mi
890 km[112]
32°48′29″N 95°55′14″W / 32.80806°N 95.92056°W / 32.80806; -95.92056 (Sabine River (source))[113]
29°59′08″N 93°47′26″W / 29.98556°N 93.79056°W / 29.98556; -93.79056 (Sabine River (mouth))
7003975600000000000♠9,756 mi2
25,268 km2[114]
7003840000000000000♠8,400 ft3/s
238 m3/s
Texass, Louisianam

34
Red River of the North
Lake Winnipeg
7002550000000000000♠550 mi
890 km[115]
[n 34]
46°15′52″N 96°35′55″W / 46.26444°N 96.59861°W / 46.26444; -96.59861 (Red River of the North (source))[117]
50°23′47″N 96°48′39″W / 50.39639°N 96.81083°W / 50.39639; -96.81083 (Red River (mouth))[118]
7005111000000000000♠111,000 mi2
287,500 km2[119]
[n 35]
7003830000000000000♠8,300 ft3/s
236 m3/s
North Dakotas, Minnesotas, Manitobam

35
Des Moines River
Mississippi River
7002525000000000000♠525 mi
845 km[120]
44°05′02″N 95°41′17″W / 44.08389°N 95.68806°W / 44.08389; -95.68806 (Des Moines (source))[121]
41°22′52″N 91°25′21″W / 41.38111°N 91.42250°W / 41.38111; -91.42250 (Des Moines River (mouth))
7004120180000000000♠12,018 mi2
31,127 km2[122]
7003640000000000000♠6,400 ft3/s
182 m3/s
Minnesotas, Missouri, Iowam

36
White River (Missouri River)
Missouri River
7002506000000000000♠506 mi
815 km[123]
42°41′10″N 103°50′14″W / 42.68611°N 103.83722°W / 42.68611; -103.83722 (White River (source))[124]
43°42′50″N 99°28′01″W / 43.71389°N 99.46694°W / 43.71389; -99.46694 (White River (mouth))
7004102000000000000♠10,200 mi2
26,418 km2[125]
7002570000000000000♠570 ft3/s
16 m3/s
Nebraskas, South Dakotam

37
Trinity River
Galveston Bay
7002506000000000000♠506 mi
815 km[126]
32°47′54″N 96°53′52″W / 32.79833°N 96.89778°W / 32.79833; -96.89778 (Trinity River (source))[127]
29°44′35″N 94°42′12″W / 29.74306°N 94.70333°W / 29.74306; -94.70333 (Trinity River (mouth))
7004179700000000000♠17,970 mi2
46,540 km2[128]
7003780000000000000♠7,800 ft3/s
222 m3/s
Texass, m

38
Wabash River
Ohio River
7002503000000000000♠503 mi
810 km[98]
40°21′07″N 84°45′57″W / 40.35194°N 84.76583°W / 40.35194; -84.76583 (Wabash River (source))[129]
37°47′53″N 88°01′38″W / 37.79806°N 88.02722°W / 37.79806; -88.02722 (Wabash River (mouth))
7004329500000000000♠32,950 mi2
85,340 km2[130]</ref>
7003100100000000000♠1,001 ft3/s
28 m3/s
Ohios, Indianam, Illinoism

text: Map[edit]


document_title: Alexa & Katie

question_text: who plays alex's mom in alexa and katie

question_tokens: who plays alex 's mom in alexa and katie

root

text: Alexa & Katie

text: Plot[edit]

text: Lifelong best friends Alexa and Katie  are eagerly anticipating the start of their freshman year of high school. The two friends confront a crisis when Alexa discovers that she is ill and starts undergoing treatment for cancer, which leaves them feeling like outsiders at a time when what seems to matter most is fitting in.The girls try to navigate through high school while dealing with the illness.[2]

tag: p

text: Cast[edit]

text: Main[edit]

text:
Paris Berelc as Alexa
Isabel May as Katie
Tiffani Thiessen as Lori
Eddie Shin as Dave
Emery Kelly as Lucas
Finn Carr as Jack
Jolie Jenkins as Jennifer

tag: ul

text: Recurring[edit]

text:
Kerri Medders as Gwenny
Merit Leighton as Hannah
Jack Griffo as Dylan
Iman Benson as Reagan

text: Production[edit]

text: Alexa & Katie is the first multi-camera sitcom produced by Netflix.[3] On April 9, 2018, Netflix renewed the series for a second season, with Wordham set to take over as showrunner.[4]

text: Episodes[edit]

text:
No.TitleDirected byWritten byOriginal release date1"Bad Hair Day"Andy CadiffHeather WordhamMarch 23, 2018 (2018-03-23)
Alexa has cancer, however after the doctor clears her for school, she and her best friend Katie get ready to start their first day of high school. However due to Alexa's chemo her hair begins to fall out, which leaves her distressed. She convices Katie to teepee her rival Gwenny's house, but they then realize they accidentally teepee'd their principal Trugly's house. After being suspended for three days, Dave then finds out that Alexa knew she was teepee'ing Trugly, making Katie upset. After Jennifer returns Katie's ski cap, which Alexa had borrowed when they teepee'd Trugly's house, Katie finds Alexa's hair in the cap and realizes why Alexa wanted to get in trouble. After Katie confronts Alexa, Katie helps Alexa by shaving her hair off with Alexa.
2"Wigs"Andy CadiffHeather WordhamMarch 23, 2018 (2018-03-23)
After the girls shaved their hair off, they go to a department store to buy wigs. The wig Katie wants to buy, however, costs $300, more than she can afford. Not wanting to let Alexa know about her money troubles, she buys the wig anyway, along with a brightly colored one. Meanwhile, Dave struggles with seeing Alexa without any hair.
3"Basketball"Jeff MelmanMatthew CarlsonMarch 23, 2018 (2018-03-23)
Alexa wants to try out for the basketball team and compete with her rival, but due to her chemo, she isn't allowed to. Katie tries out for her as a sign of support. Subsequently, a rumor starts to spread that someone in the grade has cancer. Lori starts to work from home to be closer to Alexa, but it doesn't work out. During basketball try-outs, Katie's wig falls off and her bald head is revealed, leading everyone to believe she is the one with cancer.
4"Ungroundable"Jeff MelmanNancy CohenMarch 23, 2018 (2018-03-23)
Alexa continually ropes Katie into doing bad things with her to prove to her that her mother won't ground her. Eventually, Lori comes to her senses and grounds Alexa, and for getting a bad grade on her math test, hires a tutor, which is Lucas's friend Dylan.
5"The Play, Part 1"Jeff MelmanGary MurphyMarch 23, 2018 (2018-03-23)
As everyone thinks Katie is the one with cancer, she is left wondering if she is getting special treatment after she is given the lead in the school play. Jennifer asks Lucas to babysit Jack, however it proves harder than he thought.
6"Picture Day"Victor GonzalezRay LanconMarch 23, 2018 (2018-03-23)
Alexa reveals she is the one with cancer, and everyone starts being very nice to her - even her rival, Gwenny. She continually plays pranks on Gwenny to get her to start being mean to her again, which ultimately works. Jennifer and Jack form a rivalry with Dave over football.
7"The Play, Part 2"Jeff MelmanTodd LindenMarch 23, 2018 (2018-03-23)
Katie starts to ignore Alexa more and more, as she becomes focused on the play. Lori gives Katie life lessons during rehearals, which annoys Jennifer.
8"Support Group"Phill LewisErin WagonerMarch 23, 2018 (2018-03-23)
Katie starts to feel left out as Alexa, who is back in hospital, is receiving support from her fellow cancer patients. Lori stresses over her care, and bakes a load of cookies to try to bribe the hospital nurse into giving Alexa special treatment.
9"Winter Luau"Trevor KirschnerKamon NaddafMarch 23, 2018 (2018-03-23)
Due to her low immune system, Alexa is ordered to stay home, however she video-chats with Katie on an iPad to access her lessons. Jennifer gets upset when Jack asks Dave to go to his school career day instead of her.
10"Thanksgiving"Trevor KirschnerGary MurphyMarch 23, 2018 (2018-03-23)
Alexa cooks Thanksgiving dinner, however it doesn't take long for it to ruin. Meanwhile, Katie tries to reconnect with her father, but gets upset when he continues to treat her like a little girl.
11"Secret Sleepover"Katy GarretsonNancy CohenMarch 23, 2018 (2018-03-23)
Dave and Lori take Lucas on a trip to pilot-school interviews, leaving Alexa home for the weekend, at Jennifer's. However, she and Katie get up to no good while they are gone. Ryan asks Katie to the winter formal.
12"Winter Formal, Part 1"Andy CadiffBlake J. WilligerMarch 23, 2018 (2018-03-23)
Jack takes a 'stray' cat under his wing, which Dave develops an allergic reaction to. While Dylan and Alexa try to get closer, Lucas persistently interrupts the two and tries to break them apart.
13"Winter Formal, Part 2"Andy CadiffMatthew CarlsonMarch 23, 2018 (2018-03-23)
Alexa and Katie get ready for the Winter Formal. Alexa  convices Katie to ask Ryan to the dance, and Hannah tells everyone. Eventaully, the news gets to Ryan, and he says yes before Katie can even ask him. On the day of the dance, they find out there is a flu outbreak, meaning Alexa can't go. However Katie get an idea which will allow Alexa to go; wearing a medical mask. Upon entering the dance, Alexa finds everyone with masks, including Gwenny. The episode ends with everyone dancing to Katy Perry's "Firework".

tag: table


document_title: Ribosome

question_text: the association of more than one ribosome with a single molecule of m-rna complex is called as

text: Ribosome

text: Overview[edit]

text: The sequence of DNA, which encodes the sequence of the amino acids in a protein, is copied into a messenger RNA chain. It may be copied many times into RNA chains. Ribosomes can bind to a messenger RNA chain and use its sequence for determining the correct sequence of amino acids. Amino acids are selected, collected, and carried to the ribosome by transfer RNA (tRNA) molecules, which enter one part of the ribosome and bind to the messenger RNA chain. It is during this binding that the correct translation of nucleic acid sequence to amino acid sequence occurs. For each coding triplet in the messenger RNA there is a distinct transfer RNA that matches and which carries the correct amino acid for that coding triplet. The attached amino acids are then linked together by another part of the ribosome. Once the protein is produced, it can then fold to produce a specific functional three-dimensional structure although during synthesis some proteins start folding into their correct form.

text: A ribosome is made from complexes of RNAs and proteins and is therefore a ribonucleoprotein. Each ribosome is divided into two subunits: 1; a smaller subunit which binds to a larger subunit and the mRNA pattern, and 2; a larger subunit which binds to the tRNA, the amino acids, and the smaller subunit. When a ribosome finishes reading an mRNA molecule, these two subunits split apart. Ribosomes are ribozymes, because the catalytic peptidyl transferase activity that links amino acids together is performed by the ribosomal RNA. Ribosomes are often associated with the intracellular membranes that make up the rough endoplasmic reticulum.

text: Ribosomes from bacteria, archaea and eukaryotes in the three-domain system, resemble each other to a remarkable degree, evidence of a common origin. They differ in their size, sequence, structure, and the ratio of protein to RNA. The differences in structure allow some antibiotics to kill bacteria by inhibiting their ribosomes, while leaving human ribosomes unaffected. In bacteria and archaea, more than one ribosome may move along a single mRNA chain at one time, each "reading" its sequence and producing a corresponding protein molecule.

text: The mitochondrial ribosomes of eukaryotic cells, are produced from mitochondrial genes, and functionally resemble many features of those in bacteria, reflecting the likely evolutionary origin of mitochondria.[5][6]

text: Discovery[edit]

text: Ribosomes were first observed in the mid-1950s by Romanian cell biologist George Emil Palade, using an electron microscope, as dense particles or granules.[7] The term "ribosome" was proposed by scientist Richard B. Roberts in the end of 1950s:

text: During the course of the symposium a semantic difficulty became apparent. To some of the participants, "microsomes" mean the ribonucleoprotein particles of the microsome fraction contaminated by other protein and lipid material; to others, the microsomes consist of protein and lipid contaminated by particles. The phrase "microsomal particles" does not seem adequate, and "ribonucleoprotein particles of the microsome fraction" is much too awkward. During the meeting, the word "ribosome" was suggested, which has a very satisfactory name and a pleasant sound. The present confusion would be eliminated if "ribosome" were adopted to designate ribonucleoprotein particles in sizes ranging from 35 to 100S.

text: Albert Claude, Christian de Duve, and George Emil Palade were jointly awarded the Nobel Prize in Physiology or Medicine, in 1974, for the discovery of the ribosome.[9] The Nobel Prize in Chemistry 2009 was awarded to Venkatraman Ramakrishnan, Thomas A. Steitz and Ada E. Yonath for determining the detailed structure and mechanism of the ribosome.[10]

text: Structure[edit]

text: The ribosome is a highly complex cellular machine. It is largely made up of specialized RNA known as ribosomal RNA (rRNA) as well as dozens of distinct proteins (the exact number varies slightly between species). The ribosomal proteins and rRNAs are arranged into two distinct ribosomal pieces of different size, known generally as the large and small subunit of the ribosome. Ribosomes consist of two subunits that fit together (Figure 2) and work as one to translate the mRNA into a polypeptide chain during protein synthesis (Figure 1). Because they are formed from two subunits of non-equal size, they are slightly longer in the axis than in diameter.

text: Prokaryotic ribosomes are around 20 nm (200 Å) in diameter and are composed of 65% rRNA and 35% ribosomal proteins.[11] Eukaryotic ribosomes are between 25 and 30 nm (250–300 Å) in diameter with an rRNA-to-protein ratio that is close to 1.[12] Crystallographic work [13] has shown that there are no ribosomal proteins close to the reaction site for polypeptide synthesis. This suggests that the protein components of ribosomes do not directly participate in peptide bond formation catalysis, but rather that these proteins act as a scaffold that may enhance the ability of rRNA to synthesize protein (See: Ribozyme).

text: The ribosomal subunits of prokaryotes and eukaryotes are quite similar.[15]

text: The unit of measurement used to describe the ribosomal subunits and the rRNA fragments is the Svedberg unit, a measure of the rate of sedimentation in centrifugation rather than size. This accounts for why fragment names do not add up: for example, prokaryotic 70S ribosomes are made of 50S and 30S subunits.

text: Prokaryotes have 70S ribosomes, each consisting of a small (30S) and a large (50S) subunit. Their small subunit has a 16S RNA subunit (consisting of 1540 nucleotides) bound to 21 proteins. The large subunit is composed of a 5S RNA subunit (120 nucleotides), a 23S RNA subunit (2900 nucleotides) and 31 proteins.[15]

text:
prokaryotic ribosomes (E. coli)[16]

ribosome
subunit
rRNAs
r-proteins

70S
50S
23S (2904 nt)
31

5S (120 nt)

30S
16S (1542 nt)
21

text: Affinity label for the tRNA binding sites on the E. coli ribosome allowed the identification of A and P site proteins most likely associated with the peptidyltransferase activity; labelled proteins are L27, L14, L15, L16, L2; at least L27 is located at the donor site, as shown by E. Collatz and A.P. Czernilofsky.[17][18] Additional research has demonstrated that the S1 and S21 proteins, in association with the 3'-end of 16S ribosomal RNA, are involved in the initiation of translation.[19]

text: Eukaryotes have 80S ribosomes, each consisting of a small (40S) and large (60S) subunit. Their 40S subunit has an 18S RNA (1900 nucleotides) and 33 proteins.[20][21] The large subunit is composed of a 5S RNA (120 nucleotides), 28S RNA (4700 nucleotides), a 5.8S RNA (160 nucleotides) subunits and 46 proteins.[15][20][22]

text:
eukaryotic cytosolic ribosomes (R. norvegicus)[23]

ribosome
subunit
rRNAs
r-proteins

80S
60S
28S (4718 nt)
49

5.8S (160 nt)

5S (120 nt)

40S
18S (1874 nt)
33

text: During 1977, Czernilofsky published research that used affinity labeling to identify tRNA-binding sites on rat liver ribosomes. Several proteins, including L32/33, L36, L21, L23, L28/29 and L13 were implicated as being at or near the peptidyl transferase center.[24]

text: The ribosomes found in chloroplasts and mitochondria of eukaryotes also consist of large and small subunits bound together with proteins into one 70S particle.[15] These organelles are believed to be descendants of bacteria (see Endosymbiotic theory) and, as such, their ribosomes are similar to those of bacteria.[15]

text: The various ribosomes share a core structure, which is quite similar despite the large differences in size. Much of the RNA is highly organized into various tertiary structural motifs, for example pseudoknots that exhibit coaxial stacking. The extra RNA in the larger ribosomes is in several long continuous insertions, such that they form loops out of the core structure without disrupting or changing it.[15] All of the catalytic activity of the ribosome is carried out by the RNA; the proteins reside on the surface and seem to stabilize the structure.[15]

text: The differences between the bacterial and eukaryotic ribosomes are exploited by pharmaceutical chemists to create antibiotics that can destroy a bacterial infection without harming the cells of the infected person. Due to the differences in their structures, the bacterial 70S ribosomes are vulnerable to these antibiotics while the eukaryotic 80S ribosomes are not.[25] Even though mitochondria possess ribosomes similar to the bacterial ones, mitochondria are not affected by these antibiotics because they are surrounded by a double membrane that does not easily admit these antibiotics into the organelle.[26]

text: High-resolution structure[edit]

text: The general molecular structure of the ribosome has been known since the early 1970s. In the early 2000s, the structure has been achieved at high resolutions, of the order of a few Å.

text: The first papers giving the structure of the ribosome at atomic resolution were published almost simultaneously in late 2000. The 50S (large prokaryotic) subunit was determined from the archaeon Haloarcula marismortui[27] and the bacterium Deinococcus radiodurans,[28] and the structure of the 30S subunit was determined from Thermus thermophilus.[14] These structural studies were awarded the Nobel Prize in Chemistry in 2009. In May 2001 these coordinates were used to reconstruct the entire T. thermophilus 70S particle at 5.5 Å resolution.[29]

text: Two papers were published in November 2005 with structures of the Escherichia coli 70S ribosome. The structures of a vacant ribosome were determined at 3.5-Å resolution using x-ray crystallography.[30] Then, two weeks later, a structure based on cryo-electron microscopy was published,[31] which depicts the ribosome at 11–15Å resolution in the act of passing a newly synthesized protein strand into the protein-conducting channel.

text: The first atomic structures of the ribosome complexed with tRNA and mRNA molecules were solved by using X-ray crystallography by two groups independently, at 2.8 Å[32] and at 3.7 Å.[33] These structures allow one to see the details of interactions of the Thermus thermophilus ribosome with mRNA and with tRNAs bound at classical ribosomal sites. Interactions of the ribosome with long mRNAs containing Shine-Dalgarno sequences were visualized soon after that at 4.5- to 5.5-Å resolution.[34]

text: In 2011, the first complete atomic structure of the eukaryotic 80S ribosome from the yeast Saccharomyces cerevisiae was obtained by crystallography.[20] The model reveals the architecture of eukaryote-specific elements and their interaction with the universally conserved core. At the same time, the complete model of a eukaryotic 40S ribosomal structure in Tetrahymena thermophila was published and described the structure of the 40S subunit, as well as much about the 40S subunit's interaction with eIF1 during translation initiation.[21] Similarly, the eukaryotic 60S subunit structure was also determined from Tetrahymena thermophila in complex with eIF6.[22]

text: Function[edit]

text: Ribosomes are organelles that synthesize proteins. Proteins are needed for many cellular functions such as repairing damage or directing chemical processes. Ribosomes can be found floating within the cytoplasm or attached to the endoplasmic reticulum.

text: Translation[edit]

text: Ribosomes are the workplaces of protein biosynthesis, the process of translating mRNA into protein. The mRNA comprises a series of codons that dictate to the ribosome the sequence of the amino acids needed to make the protein. Using the mRNA as a template, the ribosome traverses each codon (3 nucleotides) of the mRNA, pairing it with the appropriate amino acid provided by an aminoacyl-tRNA. Aminoacyl-tRNA contains a complementary anticodon on one end and the appropriate amino acid on the other. For fast and accurate recognition of the appropriate tRNA, the ribosome utilizes large conformational changes (conformational proofreading) .[35] The small ribosomal subunit, typically bound to an aminoacyl-tRNA containing the amino acid methionine, binds to an AUG codon on the mRNA and recruits the large ribosomal subunit. The ribosome contains three RNA binding sites, designated A, P and E. The A site binds an aminoacyl-tRNA; the P site binds a peptidyl-tRNA (a tRNA bound to the peptide being synthesized); and the E site binds a free tRNA before it exits the ribosome. Protein synthesis begins at a start codon AUG near the 5' end of the mRNA. mRNA binds to the P site of the ribosome first. The ribosome is able to identify the start codon by use of the Shine-Dalgarno sequence of the mRNA in prokaryotes and Kozak box in eukaryotes.

text: Although catalysis of the peptide bond involves the C2 hydroxyl of RNA's P-site adenosine in a proton shuttle mechanism, other steps in protein synthesis (such as translocation) are caused by changes in protein conformations. Since their catalytic core is made of RNA, ribosomes are classified as "ribozymes,"[36] and it is thought that they might be remnants of the RNA world.[37]

text: In Figure 5, both ribosomal subunits (small and large) assemble at the start codon (towards the 5' end of the RNA). The ribosome uses RNA that matches the current codon (triplet) on the mRNA to append an amino acid to the polypeptide chain. This is done for each triplet on the RNA, while the ribosome moves towards the 3' end of the mRNA. Usually in bacterial cells, several ribosomes are working parallel on a single RNA, forming what is called a polyribosome or polysome.

text: Addition of translation-independent amino acids[edit]

text: Presence of a ribosome quality control protein Rqc2 is associated with mRNA-independent protein elongation.[38][39] This elongation is a result of ribosomal addition (via tRNAs brought by Rqc2) of CAT tails: ribosomes extend the C-terminus of a stalled protein with random, translation-independent sequences of alanines and threonines.[40][41]

text: Würzburg University and Max Planck Institute researches, the results of which were published in Cell Reports and The EMBO magazines in September 2016, have shown that ribosomes have the role of being "a quality control point". Professor Utz Fischer from the University of Würzburg has been researching the assembly of proteins called "macromolecular machines" in the cell for years. He describes this assembly process as LEGO blocks: "Think of it as LEGO bricks at the molecular level: One brick is attached to the next until the product is finished. If only one defective or wrong brick is used, the entire building may be compromised as a result."[42][43][44]

text: Ribosome locations[edit]

text: Ribosomes are classified as being either "free" or "membrane-bound".

text: Free and membrane-bound ribosomes differ only in their spatial distribution; they are identical in structure. Whether the ribosome exists in a free or membrane-bound state depends on the presence of an ER-targeting signal sequence on the protein being synthesized, so an individual ribosome might be membrane-bound when it is making one protein, but free in the cytosol when it makes another protein.

text: Ribosomes are sometimes referred to as organelles, but the use of the term organelle is often restricted to describing sub-cellular components that include a phospholipid membrane, which ribosomes, being entirely particulate, do not. For this reason, ribosomes may sometimes be described as "non-membranous organelles".

text: Free Ribosomes[edit]

text: Free ribosomes can move about anywhere in the cytosol, but are excluded from the cell nucleus and other organelles. Proteins that are formed from free ribosomes are released into the cytosol and used within the cell. Since the cytosol contains high concentrations of glutathione and is, therefore, a reducing environment, proteins containing disulfide bonds, which are formed from oxidized cysteine residues, cannot be produced within it.

text: Membrane-bound ribosomes[edit]

text: When a ribosome begins to synthesize proteins that are needed in some organelles, the ribosome making this protein can become "membrane-bound". In eukaryotic cells this happens in a region of the endoplasmic reticulum (ER) called the "rough ER". The newly produced polypeptide chains are inserted directly into the ER by the ribosome undertaking vectorial synthesis and are then transported to their destinations, through the secretory pathway. Bound ribosomes usually produce proteins that are used within the plasma membrane or are expelled from the cell via exocytosis.[45]

text: Biogenesis[edit]

text: In bacterial cells, ribosomes are synthesized in the cytoplasm through the transcription of multiple ribosome gene operons. In eukaryotes, the process takes place both in the cell cytoplasm and in the nucleolus, which is a region within the cell nucleus. The assembly process involves the coordinated function of over 200 proteins in the synthesis and processing of the four rRNAs, as well as assembly of those rRNAs with the ribosomal proteins.

text: Origin[edit]

text: The ribosome may have first originated in an RNA world, appearing as a self-replicating complex that only later evolved the ability to synthesize proteins when amino acids began to appear.[46] Studies suggest that ancient ribosomes constructed solely of rRNA could have developed the ability to synthesize peptide bonds.[47][48][49] In addition, evidence strongly points to ancient ribosomes as self-replicating complexes, where the rRNA in the ribosomes had informational, structural, and catalytic purposes because it could have coded for tRNAs and proteins needed for ribosomal self-replication.[50] Hypothetical cellular organisms with self-replicating RNA but without DNA are called ribocytes (or ribocells).[51][52]

text: As amino acids gradually appeared in the RNA world under prebiotic conditions,[53][54] their interactions with catalytic RNA would increase both the range and efficiency of function of catalytic RNA molecules.[46] Thus, the driving force for the evolution of the ribosome from an ancient self-replicating machine into its current form as a translational machine may have been the selective pressure to incorporate proteins into the ribosome’s self-replicating mechanisms, so as to increase its capacity for self-replication.[50]

text: Specialized ribosomes[edit]

text: Heterogeneity in ribosome composition has been proposed to be involved in translational control of protein synthesis.[55] Vincent Mauro and Gerald Edelman proposed the ribosome filter hypothesis to explain the regulatory functions of ribosomes. Emerging evidence has shown that specialized ribosomes specific to different cell populations can affect how genes are translated.[56] Some ribosomal proteins exchange from the assembled complex with cytosolic copies [57] suggesting that the structure of the in vivo ribosome can be modified without synthesizing an entire new ribosome.