HY USMLE Q #438 – Biochemistry / Pediatrics — Transcript

Full transcript

1. 0:00how's it going guys very easy question
2. 0:01for biochemistry for step one and for
3. 0:03pediatrics for 2ck uh you will
4. 0:06occasionally get questions that are very
5. 0:07molecular uh when we talk about some of
6. 0:10the pediatric disorders okay this is one
7. 0:12of the highest yield diseases on nvme
8. 0:14it's not my opinion it's a matter of
9. 0:16what shows up repeatedly so i'll tell
10. 0:18you exactly what you need to know not
11. 0:19waste your time before we get started
12. 0:20please subscribe my channel i really
13. 0:21appreciate it give the video like really
14. 0:23appreciate it find me on instagram at
15. 0:24melbourne underscore medical
16. 0:25m-e-h-l-m-a-n-underscore medical the
17. 0:27link is down below find me on telegram
18. 0:29recently created telegram grouping
19. 0:30channel links are down below and i'll
20. 0:31start the clip four-year-old boy he has
21. 0:34coarse facial features joint
22. 0:35contractures hepatomegaly molecular
23. 0:38analysis determines an inability to
24. 0:40phosphorylate the sixth position on
25. 0:41mannose question wants to know the most
26. 0:43likely diagnosis we have our answer
27. 0:44choices so let's just walk through the
28. 0:47the answers here choice a cherry red
29. 0:49spot in the macula
30. 0:50wrong answer this refers to both tay
31. 0:53sach and neiman pick classically
32. 0:55uh t tay sack is going to be
33. 0:58uh visual loss in
34. 1:01a young child its deficiency of
35. 1:03hexosaminidase a and a buildup of gm2
36. 1:06ganglioside okay it's like wow fancy
37. 1:09sounding uh
38. 1:11the yieldness is not exceptional okay
39. 1:14when you
40. 1:15are reading about the lysosomal storage
41. 1:16diseases you're trying to memorize a big
42. 1:18chart i can tell you that
43. 1:20the yieldness is very very low and now
44. 1:22that the step one has gone to pass fail
45. 1:25pretty much a waste of time apart from
46. 1:28this one question which i i will further
47. 1:30discuss here but
48. 1:32uh taysac hexosaminidase a deficiency
49. 1:35buildup of gm2 ganglioside and neiman
50. 1:38pick a deficiency of spinal myelinase a
51. 1:40buildup of sphingomyelin they're both
52. 1:42cherry red spot on the macula that you
53. 1:43can get
54. 1:44and
55. 1:45neiman pick will have hepatomegaly tay
56. 1:48sac will not once again they're low
57. 1:50yield we could spend more time chatting
58. 1:51about them but i'm not going to waste
59. 1:53your [ __ ] time okay it's not a
60. 1:54numerical step one anymore
61. 1:56choice b deficiency of myophosphorylates
62. 1:58wrong answer this is a glycogen storage
63. 2:00disease this is mcardle syndrome okay so
64. 2:02myophosphorylase aka muscle glycogen
65. 2:04phosphorylase this is of yieldness worth
66. 2:08knowing okay so this is going to be a
67. 2:10young adult generally who has severe
68. 2:13cramping with exercise
69. 2:16and this can lead to rhabdo okay with
70. 2:18myoglobin area that's mcardle syndrome
71. 2:20okay not not difficult okay just 21 year
72. 2:23old he's he went sprinting he gets
73. 2:25really bad muscle cramps and they say
74. 2:26what's the deficient enzyme it's just
75. 2:28myophosphorylase or glycogen uh or
76. 2:31muscle glycogen phosphorylase okay
77. 2:33glycogen storage these type 5 and
78. 2:35carlson
79. 2:36should i see violation of rough
80. 2:38endoplasmic reticulum wrong answer
81. 2:40however i threw this in here because
82. 2:43uh this is seen on one of the
83. 2:46step one offline nvme exams where they
84. 2:49just simply ask you
85. 2:50if
86. 2:51proteins cannot be sent from the rer to
87. 2:55the golgi
88. 2:57for processing what would be seen in the
89. 3:00cell
90. 3:01and the answer is just dilation of the
91. 3:02rer i mean it doesn't there's there's
92. 3:04nothing complicated about that thought
93. 3:06process okay if something can't be sent
94. 3:08out of the rear of the golgi well what's
95. 3:10gonna happen the rer could theoretically
96. 3:12dilate okay
97. 3:14not my [ __ ] opinion but it shows up
98. 3:16on one of the forms and students get
99. 3:18this wrong okay so i'm just i'm just
100. 3:20mentioning it
101. 3:21choice d increased serum enzyme levels
102. 3:23is the correct answer very very high
103. 3:25yield this is eye cell disease okay so
104. 3:28when i saw this presentation very very
105. 3:30buzzy very classic horse facial features
106. 3:33joint contractures hepatomegaly
107. 3:36now this condition
108. 3:37we have
109. 3:38lysosomal enzymes that are that are at
110. 3:41the golgi apparatus for processing okay
111. 3:44so when when proteins are synthesized
112. 3:46it's at the rough endoplasmic reticulum
113. 3:48they then go to the golgi where they're
114. 3:50modified and then when they're at the
115. 3:52golgi they can then be shuttled to
116. 3:53various locations so you have their
117. 3:55recently synthesized modified lysosomal
118. 3:59enzymes that are still at the golgi and
119. 4:01now they have to get sent to the
120. 4:02lysosomes for storage all right and the
121. 4:05way this
122. 4:08what am i going to do restart the whole
123. 4:09[ __ ] clip now that i coughed i mean i
124. 4:11could but i'm just going to continue
125. 4:12with the clip here so
126. 4:15you have the recently synthesized
127. 4:17modified
128. 4:18lysol enzymes at the golgi apparatus and
129. 4:20they have to be sent to the lysosomes
130. 4:22for storage and the way the cell does
131. 4:24this for whatever [ __ ] reason it
132. 4:26occurs via a molecule known as mannose
133. 4:296-phosphate
134. 4:31so
135. 4:32if we can't phosphorylate the 6-position
136. 4:34of mannose we can't make
137. 4:35mannose-6-phosphate and we therefore
138. 4:37can't send the lysol enzymes from the
139. 4:40golgi
140. 4:41to the lysosomes so that in and of
141. 4:43itself that mechanism is very high yield
142. 4:45if they say
143. 4:46uh if they give you this spin yet and
144. 4:48they say where is the location for the
145. 4:51defective enzyme process the answer is
146. 4:54the golgi because it's occurring at the
147. 4:55golgi what i just said but if they say
148. 4:58enzymes cannot be sent where the answer
149. 5:02is the lysosome because they can't get
150. 5:03sent there so the enzymes end up in the
151. 5:06cytosol slash
152. 5:09the serum instead and they can give you
153. 5:11a similar presentation and just say
154. 5:13uh laboratory studies show increased
155. 5:16serum levels of and then they list four
156. 5:18obscure sounding lysosomal enzymes
157. 5:20and you just need to know well that's
158. 5:23eye cell disease
159. 5:24because in that condition you're going
160. 5:26to get high lysosomal enzymes in the
161. 5:28serum and in the cell okay and the
162. 5:30cytoplasm it's it's a high yield point
163. 5:32you need to know
164. 5:33so
165. 5:35choice e misfolded protein retaining the
166. 5:37rer wrong answer this is cystic fibrosis
167. 5:40okay
168. 5:40so
169. 5:41uh cftr channel chloride channel it
170. 5:44should be on the cell surface
171. 5:46but
172. 5:47because of oftentimes
173. 5:49missense mutation delta f508 oftentimes
174. 5:54uh when we have the misfolded protein it
175. 5:56just gets retained in the cytoplasm
176. 5:58slash rer and they want you to know that
177. 6:00that's what you're going to see
178. 6:02on
179. 6:03electron microscopy students get this
180. 6:05wrong frequently they say what do you
181. 6:07see on electromicroscopy and cf a
182. 6:09student will say
183. 6:10uh abnormally folded uh channel on the
184. 6:13cell surface it's wrong answer because
185. 6:16it's not gonna it's not gonna make it to
186. 6:17the cell surface okay so it's going to
187. 6:19be uh sequestered in the rough
188. 6:21endoplasmic reticulum
189. 6:23you know the deal i'm going to continue
190. 6:24to make more content if you like my
191. 6:25stuff subscribe my channel and i
192. 6:27appreciate your time that's it