Lecture 17 Supplemental Material Carbohydrates — Transcript

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1. 0:00so in this part of supplemental material
2. 0:02i want to give you some more information
3. 0:04working through carbohydrates looking at
4. 0:06those as monosaccharides and also
5. 0:07considering
6. 0:08um how monosaccharides become building
7. 0:10blocks for polysaccharides and how these
8. 0:12can allow for unique structural
9. 0:14properties
10. 0:15so the first is to look at glucose and
11. 0:17galactose
12. 0:18i think about how these can cyclize
13. 0:21the way that these sugar molecules exist
14. 0:24are in the cyclic forms in the cell
15. 0:26how does the cyclicization happen as
16. 0:28well as a difference in these structures
17. 0:29some important definitions we can look
18. 0:31at
19. 0:32also looking at the involvement of
20. 0:33monosaccharides in the structure of
21. 0:34lactose
22. 0:35we can consider linkage identify numeric
23. 0:37carbons and also discuss whether this
24. 0:40uh lactose is reducing or not reducing
25. 0:42sugar
26. 0:43so the first is to have you all practice
27. 0:45drying out these structures
28. 0:47obviously you need to know all the
29. 0:49structures in the boxes
30. 0:51but definitely glucose galactose and
31. 0:53fructose are going to be the ones that
32. 0:55we see the most and
33. 0:56obviously glucose of the three is
34. 0:58probably even the most important and
35. 1:00looking at derivatives
36. 1:01so anytime you study studying in
37. 1:03hierarchy um where
38. 1:04the things you're going to see the most
39. 1:05or the ones you need to know definitely
40. 1:07make sure that you understand
41. 1:08um glucose cyclicization work your way
42. 1:11through galactose
43. 1:12fructose and then start learning each of
44. 1:14the others
45. 1:15so this is draw the cichlid structures
46. 1:17as they exist in the cell
47. 1:19and how does the cyclicization happen
48. 1:21and what is the difference in the
49. 1:22structure so both galactose and glucose
50. 1:24are going to be
51. 1:26um aldo hexoses which means they're
52. 1:28going to prefer
53. 1:29the parent form it's the most stable
54. 1:31which is a six-membered ring
55. 1:33when we look at the six-membered ring
56. 1:35this means that there's going to be five
57. 1:36carbons in one oxygen
58. 1:38so if we start here at carbon one this
59. 1:41is where our aldehyde functional group
60. 1:43is
61. 1:43this is where we have the ability of
62. 1:45nucleophilic attack
63. 1:47we have to have five carbons that
64. 1:48cyclize through this
65. 1:50um uh sorry you have to have five
66. 1:53carbons in the pure and cyclic structure
67. 1:55and then the oxygen forms the sixth
68. 1:57member that's going to be the
69. 1:58nucleophile
70. 1:59so we would have to count one carbon two
71. 2:02three four
72. 2:02five so my fifth carbon and then i see
73. 2:04that my oh is going to serve as the
74. 2:06nucleophile
75. 2:07so this is how we have our ring
76. 2:10closing and we're going to do
77. 2:12nucleophilic attack
78. 2:13on our carbonyl we're going to push the
79. 2:15electrons up into the carbonyl oxygen
80. 2:17pick up a proton
81. 2:19and we're going to allow for
82. 2:20cyclicization so this is the formation
83. 2:23of the new bond
84. 2:24this is going to be the anomeric carbon
85. 2:29and we know that through ring opening
86. 2:31and closing
87. 2:32we can have in this case pointed in the
88. 2:36same
89. 2:36orientation as our beta conformation
90. 2:40if we have our anomeric carbon pointed
91. 2:42in the opposite orientation then it
92. 2:43would be in the alpha conformation
93. 2:45both of those are possible just depends
94. 2:47on directionality of which nucleophilic
95. 2:49attack happens
96. 2:50so that's the important thing for
97. 2:51cyclicalization we have the same thing
98. 2:53when it comes to glucose
99. 2:56and ring structure is going to be formed
100. 2:59we have here formation of our new
101. 3:01covalent bond and we also have
102. 3:03that beta conformation with respect to
103. 3:05our anomalous carbon
104. 3:08so in both cases we see our carbon one
105. 3:11that becomes anomier carbon okay the
106. 3:14next question says what are some of the
107. 3:16differences in the structure
108. 3:17so if we look at galactose and glucose
109. 3:19these structures are identical the only
110. 3:21difference is going to be
111. 3:22stereochemistry about carbon 4. because
112. 3:26of that by definition we call these
113. 3:28epimers
114. 3:29because they only differ in
115. 3:31stereochemistry at one carbon
116. 3:33so when we look at the structures this
117. 3:34is highlighted here in red
118. 3:36we would see that structure the flipping
119. 3:39with respect to the oh group to this
120. 3:44particular carbon four um where we have
121. 3:46these different
122. 3:47um forms so make sure as you draw these
123. 3:51we think about them in terms of the
124. 3:52linear structure how they cyclize
125. 3:54and drawing cyclic structure so taking
126. 3:56from monosaccharides these then become
127. 3:58building blocks for other disaccharides
128. 4:00and polysaccharides the next part was to
129. 4:02get you to look at the involvement of
130. 4:03these monosaccharides in terms of
131. 4:05structure of lactose which we know
132. 4:06lactose is a disaccharide so we're going
133. 4:09to look at how galactose and glucose
134. 4:11link together
135. 4:12identify involvement of anomeric carbons
136. 4:14determine if this is a reducing or
137. 4:15non-reducing sugar
138. 4:17so the first thing when we look at the
139. 4:19structure
140. 4:20is this leading sugar is going to use
141. 4:23its anomeric carbon
142. 4:25in order to form the glycosidic bond
143. 4:30so what we see here is carbon 1 is the
144. 4:32anomeric carbon of
145. 4:34galactose and we see that this bond is
146. 4:37pointing
147. 4:38up same directionality as we see with
148. 4:40carbon 6
149. 4:41so that tells us it's a beta
150. 4:43conformation for the linkage then we
151. 4:45have to see how it attaches to the
152. 4:47second sugar
153. 4:48in this case we're going to have glucose
154. 4:50and we see that its attachment is to
155. 4:52carbon 4. so for linkage we put beta
156. 4:55linkage one between carbon four so beta
157. 4:57orientation of anomeric carbon one and
158. 4:59it links to
159. 5:00carbon four which is the non-anomeric
160. 5:03carbon of glucose
161. 5:04so if i want to identify anomeric
162. 5:06carbons these are gonna be carbon one
163. 5:09i would see the anomeric carbons in both
164. 5:11of my structures we know that the
165. 5:13enormous carbon of galactose is involved
166. 5:15in
167. 5:15the glycosidic bond linkage beta 1 4 and
168. 5:18we see that the anomeric carbon of
169. 5:20glucose
170. 5:21is still capable of ring opening and
171. 5:22closing that tells us then
172. 5:25because we can still flip between
173. 5:29the alpha and the beta um anomeric
174. 5:33carbon
175. 5:33these animals that this is going to be
176. 5:35what we call
177. 5:36a reducing sugar
178. 5:41and this just tells us it's still
179. 5:43capable
180. 5:45of ring opening
181. 5:49and closing so in this case it would be
182. 5:52the hemiacetal
183. 5:54chemistry the next thing is to look at
184. 5:58similarities and differences in
185. 5:59structures when you have a lot of things
186. 6:00you're trying to learn relatively
187. 6:02quickly
188. 6:02if we can go back and think about this
189. 6:05previous
190. 6:06two slides we need to know the important
191. 6:08monosaccharides in terms of their
192. 6:10cyclized structures
193. 6:12and then we need to be able to determine
194. 6:14the polysaccharides linkage
195. 6:16anomeric carbons reducing and
196. 6:17non-reducing if you apply this to all of
197. 6:19these sugars that we're looking at and
198. 6:20start looking at
199. 6:21structures similarities and differences
200. 6:23it helps your brain learn these much
201. 6:25faster and far more easily be able to
202. 6:27answer questions so we're going to look
203. 6:29at some of the similarities and
204. 6:30differences that we see between chitin
205. 6:32and cellulose
206. 6:33so first we're going to start with
207. 6:34similarities so those things that are
208. 6:36similar
209. 6:37we see that in both cases they're going
210. 6:39to utilize glucose
211. 6:40as monosaccharides we can see in both of
212. 6:44these that we're going to
213. 6:46give rise to beta 1
214. 6:494 linkages
215. 6:55when we look in differences so those
216. 6:57things that are going to be the
217. 6:58uniquenesses we can see that
218. 7:00chitin utilizes in acetoglucosamine
219. 7:03so this is a modified form we have an
220. 7:05amination reaction of glucose
221. 7:07and when we look here at cellulose we
222. 7:10see that we do not have any
223. 7:12modifications
224. 7:13we still retain that oh group so that's
225. 7:16a way to help
226. 7:16allow for differences in terms of
227. 7:18similarities and structures
228. 7:19then you can go ahead and ask yourself
229. 7:21as a next step also what about function
230. 7:25in both of these cases these are going
231. 7:27to play structural role
232. 7:31these are going to be important in terms
233. 7:33of protecting
234. 7:34chitin we see it playing part of the
235. 7:36exoskeleton
236. 7:38and cellulose we know half the carbon in
237. 7:41the biosphere is involved in this this
238. 7:43is what we see for
239. 7:44plants and their structure the next
240. 7:47slide was to have you look at alpha
241. 7:49amylose and cellulose so again making
242. 7:51some comparisons and looking at the
243. 7:53differences in their structures so some
244. 7:55similarities again
245. 7:56in terms of looking at these both are
246. 7:59going to utilize glucose
247. 8:02and both of these are going to allow for
248. 8:04a large number of these glucose
249. 8:06molecules to be present
250. 8:08if we look at alpha amylose and think of
251. 8:10some differences
252. 8:11we have here an alpha 1 4 linkage
253. 8:14compare that to a cellulose beta 1 4
254. 8:17linkage
255. 8:18so really the major structural
256. 8:19difference is the linkage how important
257. 8:21is that
258. 8:21consider the overall structures that we
259. 8:23get thousands of these linked together
260. 8:25for alpha amylose this is going to be a
261. 8:27glucose storage molecule
262. 8:31that we have within plants
263. 8:34and when humans consume that
264. 8:38this is what we call within our diet
265. 8:40starch
266. 8:43and so lots of glucose molecules are
267. 8:45going to get released
268. 8:46it takes on this helical twist because
269. 8:49of the way
270. 8:50these alpha 1-4 linkages work now in
271. 8:52comparison for cellulose we already said
272. 8:54that it has a structural role it offers
273. 8:56protection for plants
274. 8:59and we know that because of the beta 1 4
275. 9:02linkages these form were linearized
276. 9:05and what happens is in between the
277. 9:06chains that we have a lot of hydrogen
278. 9:08bonds that start to exist
279. 9:10that really can help stabilize the
280. 9:12structure and allow for these to play
281. 9:15these molecules to play a role that
282. 9:17really allows for water
283. 9:19not even to be able to pass through the
284. 9:21cellulose structure
285. 9:24so helpful study hints always are going
286. 9:25to be to look for commonalities and
287. 9:27structures just like we know
288. 9:28glucose and galactose they go through
289. 9:30the same type of
290. 9:32cyclization we know that we have epimers
291. 9:35that exist between glucose and galactose
292. 9:37they only differ by one stereochemistry
293. 9:40we see that these are both involved in
294. 9:41forming the disaccharide lactose and we
295. 9:43can look at the importance of the
296. 9:44linkage
297. 9:45we have chitin and emanated form that
298. 9:48exist of glucose
299. 9:49plays again an important structural role
300. 9:51as exoskeletons and then we can compare
301. 9:53alpha amylose and cellulose
302. 9:55we know here that we're looking at the
303. 9:56different differences in linkage
304. 9:58alpha amyloid plays an important role in
305. 10:00plants for storing of glucose whereas
306. 10:02cellular
307. 10:03cellulose plays an important role in
308. 10:04plants and allowing for
309. 10:06their structural protection as well so
310. 10:09as you approach these looking for
311. 10:10commonalities looking for differences
312. 10:12can become helpful and don't just look
313. 10:14at it from a structural perspective
314. 10:16start there
315. 10:17they'll look to see how does the
316. 10:19structure allow for whatever
317. 10:20biological function that these
318. 10:22carbohydrates can have
319. 10:23hope that's helpful this will be the
320. 10:25quiz material for next week