YouTube Transcript:
Galactose Metabolism

Skip watching entire videos - get the full transcript, search for keywords, and copy with one click.

Video Transcript

Available languages:

View:

welcome back to dirty medicines dirty

biochemistry series this video is on the

disorders of galactose metabolism if I

can pause for a second and just lay out

kind of how we're going to go through

this video we're going to start by

outlining the normal biochemistry so I'm

going to give you the pathway about how

we start with lactose and convert it

into different sugars and work our way

through the pathway of galactose

metabolism along the way I'll show you

what three diseases will manifest if we

knock out certain enzymes that is to say

if we have certain enzymatic

deficiencies as I go through these

diseases I'll give you my awesome dirty

medicine mnemonics to help you remember

the hi old findings that you'll be asked

to know on test day when you sit for us

Emily or comlex

so let's begin by talking about lactose

which is our starting material lactose

can be converted into both glucose and

galactose the enzyme that converts

lactose into galactose is lactase

another way of saying this is that the

enzyme lactase breaks down lactose now

think about the name you've probably

heard about lactose intolerance before

and you're also probably aware that this

is due to a problem with the lactase

enzyme but if you look at the name

lactase it's telling you that it's acing

or breaking down lack'd or lactose so

that's where the name comes from

so again lactose is converted into

galactose by lactase now everything you

see here shown in the gray box is

occurring at the brush border of the

small intestine we'll come back at the

end of this video and talk about lactose

intolerance because of the three

diseases of galactose metabolism it's

the lowest yield next galactose can be

converted also into one of two different

products one is galactose 1-phosphate

and the other is Galacta tall now you

need to know both of the enzymes that

convert galactose into these two

different products the enzyme that

converts galactose into Galacta tall is

aldose reductase the enzyme that

converts galactose into galactose

1-phosphate is galacto kinase now

just as an aside sort of a big picture

high-yield way of remembering some

biochemistry whenever you see an enzyme

that ends in kinase it means it's just

putting a phosphate group on whatever

the reactant is so in this case you

start with galactose and it gets a

phosphate in the one position and that's

why the enzyme is galacto kinase because

it's kinase Anor sticking a phosphate on

galactose this also helps explain why

the product is galactose 1-phosphate

because it has one phosphate stuck onto

it by galacto kinase so keep that in

mind if you're ever struggling with

enzyme names reactants and products

now galactose 1-phosphate can be

converted into glucose 1-phosphate by

the enzyme galacto kinase one phosphate

your it'll trance race in this step you

need UDP glucose to be converted into

UDP galactose as a cofactor now this

step is extremely extremely important to

understand and it's very high yield

we'll talk about it in a little bit

about knocking out this enzyme and what

disease you get if that happens now once

you have glucose 1-phosphate you should

be a little bit familiar with this

product glucose 1-phosphate

has a lot of downstream options it can

enter glycolysis it could enter glycol

Genesis it can be used in a ver in a

variety of biochemical pathways so

keeping with our theme that we've seen

throughout the dirty biochemistry series

different reactions are generating

different products which can be used by

other biochemical pathways so this is

the main pathway of galactose metabolism

and you need to know the enzymes shown

in red you also need to know the

cofactor shown in green now let's talk

about what happens if you have certain

enzyme deficiencies the first disease

that we'll talk about is what you get if

you knock out galacto kinase so shown in

this large blue X we have an enzyme

deficiency of galacto kinase now think

about this by looking at our pathway if

you don't have galacto kinase then you

cannot convert galactose into galactose

1-phosphate so you can't do the blue

dotted line instead

this will be shunted to the blue thick

line so galactose will be converted into

Galacta tall by aldose reductase so by

simply knocking out galacto kinase we

have a preference to divert galactose

into galactose all this disease is aptly

named a galacto kinase deficiency so

again what do you have here you have a

decrease of the enzyme galacto kinase

you have a decrease of the product

galacto kinase one phosphate because you

cannot convert the reactant into the

product instead you have an increase of

Galacta tall because the pathway gets

shunted in preference of converting

galacto kinase into Galacta tall so

these are the findings that you need to

be familiar with for a galacto kinase

deficiency but there are a lot of

clinical findings and other high-yield

features that you could be required to

know on USMLE or complex and that's what

we're going to talk about now the other

things that you should know about a

galacto kinase deficiency are that

you'll see galactosemia which means

galactose in the blood right

amia means blood so galactose emia

galactose in the blood galactose urea

which urea means urine so galactose in

the urine so galactose in the blood and

the urine because we have a lot of

galactose that's accumulating since we

cannot use galacto kinase you'll have

abnormal eye tracking i'll come back to

this in just a second but you're gonna

see a lot of visual difficulties when

you have an accumulation of galactose

all lack of the development of a social

smile this is an autosomal recessive

disease and you'll see infantile

cataracts now overall galacto kinase

deficiency is really not a severe disease

disease

so you see infantile cataracts that

aren't that bad and you see abnormal eye

tracking when you have an accumulation

of a substance like Galacta tall that

substance actually gets trapped in the

lens of the eye and when that happens

you get the cataracts and you get

abnormal eye tracking so how do you

remember all of these high heel findings

well you should remember this by

remembering galacto kinase deficiency

gee al AC G

for galactosemia and Galactus urea

because that galactic galactose is

accumulating in the blood and

accumulating in the urine a for abnormal

eye tracking because there's an increase

in Galacta tall which is being trapped

in the eye L for lack of a social smile

during development a for autosomal

recessive disease and C for infantile

cataracts or just cataracts so that's

galacto kinase deficiency and it's

really not as bad as the next disease

that we're going to talk about so again

this is a galacto kinase deficiency when

you knockout galacto kinase now let's

talk about the more severe form of a

galacto kinase problem and that's if we

actually knock out the next enzyme in

the pathway we knock out galacto kinase

one phosphate your it'll transfer ace so

this is a really severe disease much

more severe than the galacto kinase

deficiency and the reason is that

because this enzyme is processing a lot

more of the galactose load in the body

so if you knock this one out the

symptoms are going to be way more severe

and you're gonna get a greater

accumulation of products in the body and

it's that accumulation of products that

isn't normally there that causes all of

the symptoms so look at our pathway if

we knock out galacto kinase one

phosphate your Riddle trance race then

we can't do the two blue dotted lines we

cannot convert galactose 1-phosphate

into its next product and we can't

really convert galactose into galactose

1-phosphate because without this enzyme

galactose 1-phosphate is going to build

up and there's going to be negative

feedback that's going to tell galacto

kinase not to convert galactose into

galactose 1-phosphate so again just like

in the galacto kinase deficiency with a

galacto kinase one phosphate your it'll

transfer each deficiency there's going

to be a preference to shunt the

galactose into galactose all so here are

our findings and this disease is

referred to as classic galactosemia so

the pathophysiology here is that we have

a deficiency of galacto kinase one

phosphate your Riddle transferase and

because of this we have an increase in

Galacta tall just like we did in our

previous disease and an increase in

galactose the only difference here is

that these are accumulating in much

higher volumes and we're gonna get much

more severe symptoms so let's talk about

the high-yield symptoms and associated

findings that you should absolutely know

for USMLE and comlex

you get really severe cataracts you get

liver enlargement so hepatomegaly again

this is also autosomal recessive you're

very susceptible to sepsis and

specifically e-coli sepsis in in infancy

this classically will occur when the

infant starts feeding right so initially

if you start giving them milk and they

develop vomiting diarrhea nausea crying

after they're fed initially this is

where this classically presents so it's

going to be when the infant starts

feeding you're gonna see an intellectual

disability and you're gonna see the

color of their skin change so they're

gonna get jaundice so how do you

remember all this stuff right it's a lot

of information I totally get it

but dirty medicine has your back just

remember classic and galactosemia see

for cataracts l4 liver enlargement a4

autosomal recessive s4 sepsis s4 start

of feeding so when the infant begins

getting milk early in life I for

intellectual disability and see for

color changes

aka jaundice so the first disease was a

galacto kinase deficiency and this

disease is classic galactosemia so the

difference is in the name and the dirty

medicine mnemonic is to simply use the

name of the disease to help you recall

the high-yield findings so really simply

guys because the body can't process the

galactose the treatment is to just not

give them galactose or lactose in their

diet now remember that galactose comes

from lactose so you don't want to give

them the upstream reactant you don't

want to give them the lactose you also

don't want to give them galactose okay

so that's classic galactosemia very very

high yield associated findings know

about all of these features the last of

these three diseases that we're going to

talk about in this lecture is actually

lactose intolerance now I'm sure many of

you have heard about lactose intolerance

because it's very common in multiple

cultures across the world so really

briefly just

for completeness sake I'll discuss it

here but know that of these three

diseases it's the lowest yield lactose

intolerance your findings are going to

be increased h2 in the breath increase

ch4 and increased organic acids you're

obviously going to get the symptoms of

bloating gas eNOS some diarrhea and

you're gonna see a decrease in the pH of

the stool so know these findings but

don't overly commit this to memory like

this is definitely important to know but

if you're struggling for brain space

know the first two diseases that we

talked about there are two types of

lactose intolerance one is the primary

type so this is basically age

determinant so everybody in their life

reaches a certain age where the ability

of our intestines to process lactose

simply is not what it was at Birth the

prevailing theory here is that we

evolved as humans to need breast milk

when we're born and when we reach a

certain age we obviously don't need to

be breastfed anymore so the intestines

would evolve over time to not be able to

process milk because evolutionarily

speaking you don't need milk after a

certain age so that's what's responsible

for the primary type of lactose

intolerance and this is classically seen

in african-americans Asians and even

some Native Americans the secondary type

of lactose intolerance and the most

high-yield part of this slide that you

should definitely know is the post viral

lactose intolerance so if you get some

type of gastroenteritis and you knock

out the intestinal brush border because

of this inflammation or some type of

autoimmune process anything that can

damage the intestinal brush border can

cause an acquired lactose intolerance

because if you damage that intestinal

brush border then you cannot process

lactose because again the intestinal

brush border is the site where lactose

gets processed by lactase so no the

primary type which depends on your age

but no the secondary type especially

this is really high yield after a really

bad gastroenteritis you could develop

the symptoms of lactose intolerance

lasts really high you'll point that I

need to include about lactose

intolerance is that if you do a biopsy

or you look at the histology you'll see

normal intestinal mucosa and this is so

important guys

very very high yield buzzword because

there's so much different GI pathology

that they're gonna go after on USMLE and

comlex but lactose intolerance is normal

intestinal mucosa so if you see this it

helps you rule in or rule out certain

things that should be on your

differential when you're answering these

questions but guys that's it

that's galactose metabolism that's the

diseases of galactose metabolism know

the pathway know the enzymes and know

the symptoms especially of the galacto

kinase deficiency and classic

galactosemia if you know what I've

talked about in this video you'll

definitely get all of your questions

Click on any text or timestamp to jump to that moment in the video

Most transcripts ready in under 5 seconds

One-Click Copy125+ LanguagesSearch ContentJump to Timestamps

Paste YouTube URL

Enter any YouTube video link to get the full transcript

Most transcripts ready in under 5 seconds

Get Our Chrome Extension

Get transcripts instantly without leaving YouTube. Install our Chrome extension for one-click access to any video's transcript directly on the watch page.

Add to Chrome — Free

Works with YouTube, Coursera, Udemy and more educational platforms

Get Instant Transcripts: Just Edit the Domain in Your Address Bar!

YouTube

←

→

↻

https://www.youtube.com/watch?v=UF8uR6Z6KLc

YoutubeToText

←

→

↻

https://youtubetotext.net/watch?v=UF8uR6Z6KLc

YouTube Transcript:Galactose Metabolism

Video Transcript

Paste YouTube URL

Transcript Extraction Form

Get Our Chrome Extension

Get Instant Transcripts: Just Edit the Domain in Your Address Bar!

YouTube Transcript:
Galactose Metabolism