Carbohydrates | Biochemistry

Summary

In this video, Dr. Mike discusses carbohydrates, one of the four major macromolecules, alongside proteins, fats, and nucleic acids. He explains that carbohydrates are composed of carbon, hydrogen, and oxygen, and exist in various forms: monosaccharides, disaccharides, and polysaccharides. Glucose, fructose, and galactose are common monosaccharides with the same chemical formula but different structures. The video also covers the digestion and storage of carbohydrates, lactose intolerance, and the difference between plant polysaccharides like cellulose, which humans cannot digest, and glycogen, which the body stores for energy.

Takeaways

• 💡 Carbohydrates are one of the four major macromolecules, along with proteins, fats, and nucleic acids.
• 🧬 Carbohydrates are composed of carbon, hydrogen, and oxygen atoms (carbo = carbon, hydrate = water).
• 🔄 Carbohydrates mainly function as a source of energy in the body and are found in cells and cell membranes.
• 🍬 The three main types of monosaccharides are glucose, fructose, and galactose, all of which have the same chemical formula (C6H12O6) but differ in structure.
• 🏃 Glucose is the primary monosaccharide used for energy production in the body, while fructose and galactose are converted to glucose in the liver.
• 🔗 Disaccharides are formed by joining two monosaccharides through a dehydration reaction (removal of water). Examples include sucrose (glucose + fructose) and lactose (glucose + galactose).
• 🧪 Lactose intolerance occurs when the body lacks the enzyme lactase, preventing the breakdown of lactose into glucose and galactose, which can lead to diarrhea due to osmotic effects.
• 🌾 Polysaccharides, or complex carbohydrates, can be ingested from plants (starch, cellulose) or animals (glycogen).
• 🥬 Humans cannot digest cellulose from plants (e.g., in leafy greens) due to the lack of necessary enzymes, while animals like cows can.
• 🧱 Glucose can be stored in the body as glycogen, a highly branched polysaccharide, for later energy use.

Q & A

What are the four major types of macromolecules mentioned in the script?

The four major types of macromolecules are carbohydrates, proteins, fats, and nucleic acids.

What elements make up carbohydrates?

Carbohydrates are made up of carbon, hydrogen, and oxygen.

What are the three main types of monosaccharides?

The three main types of monosaccharides are glucose, fructose, and galactose.

How do glucose, fructose, and galactose differ chemically?

They have the same chemical formula (C6H12O6) but differ in the arrangement of their atoms, making them isomers.

What happens to galactose and fructose in the liver?

In the liver, galactose and fructose are converted into glucose for energy use or storage as glycogen.

What is a dehydration reaction, and how does it relate to carbohydrates?

A dehydration reaction removes a water molecule to link sugar molecules together, forming disaccharides like sucrose and lactose.

Why do people with lactose intolerance experience digestive issues?

People with lactose intolerance lack the enzyme lactase, which breaks down lactose. Without this enzyme, lactose remains undigested, leading to water retention in the intestines and resulting in diarrhea.

What is the difference between cellulose, starch, and glycogen?

Cellulose is a long linear chain of glucose found in plants, starch is branched glucose from plants, and glycogen is highly branched glucose used by animals for energy storage.

Why can cows digest cellulose but humans cannot?

Cows have the necessary enzymes to break down cellulose into glucose, while humans do not, making cellulose indigestible for us.

What role do polysaccharides play in the human diet?

Polysaccharides like starch and glycogen can be broken down for energy in humans, while cellulose acts as fiber, aiding in digestion by bulking up stool.

Outlines

00:00

🔬 Carbohydrates: Composition and Structure

This paragraph introduces carbohydrates as one of the four major macromolecules, alongside proteins, fats, and nucleic acids. It explains that carbohydrates are composed of carbon, hydrogen, and oxygen. The basic structure of carbohydrates is hydrocarbons, and many carbohydrates form ring-shaped molecules. Carbohydrates can exist as monosaccharides (single sugar units), disaccharides (two sugar units), or polysaccharides (many sugar units). Their primary role in the body is energy production, although they are also found in cell membranes and genetic material.

05:02

🔢 Types of Monosaccharides and Isomers

This section focuses on monosaccharides, highlighting three primary types: glucose, fructose, and galactose. Despite having the same chemical formula (C6H12O6), their structural arrangements differ, making them isomers. Glucose is the main monosaccharide used for energy. The liver converts fructose and galactose into glucose after absorption. Additionally, it explains the process of converting glucose into glycogen for storage. The paragraph discusses the role of monosaccharides in energy production and their structural properties.

⚛️ Disaccharides Formation and Lactose Intolerance

This paragraph explores the formation of disaccharides, like sucrose and lactose, through dehydration reactions where water is removed to link monosaccharides. It describes how sucrose (glucose + fructose) and lactose (glucose + galactose) are formed. The focus shifts to lactose intolerance, where some individuals lack the enzyme lactase, which is needed to break down lactose. Without lactase, lactose remains undigested in the intestines, leading to an osmotic effect where water is drawn into the intestines, resulting in diarrhea.

🌿 Polysaccharides and Fiber

This paragraph explains the differences between polysaccharides derived from plants and animals. It describes starch and cellulose from plants and glycogen from animals. Humans lack the enzymes needed to digest cellulose, which becomes dietary fiber that helps bulk up stool and move material through the intestines. In contrast, humans can digest starch and glycogen. The structural differences between these polysaccharides are explained, with cellulose being linear, starch slightly branched, and glycogen highly branched. The paragraph concludes by highlighting how carbohydrates are stored and used by the body.

Keywords

💡Carbohydrates

Carbohydrates are one of the four major macromolecules, alongside proteins, fats, and nucleic acids. They are composed of carbon, hydrogen, and oxygen. In the video, carbohydrates are explained as a key energy source for the human body and are present in forms like monosaccharides, disaccharides, and polysaccharides. They can be found in cell membranes and genetic material, but their primary function is energy production.

💡Monosaccharides

Monosaccharides are the simplest form of carbohydrates, consisting of single sugar molecules like glucose, fructose, and galactose. These sugars share the same chemical formula (C6H12O6), but differ in their structure. The video highlights glucose as the main monosaccharide used by the body for energy.

💡Disaccharides

Disaccharides are carbohydrates formed by the combination of two monosaccharides. For example, glucose and galactose bond to form lactose, while glucose and fructose bond to form sucrose. The process that links them is called a dehydration reaction, which removes a water molecule. Disaccharides must be broken down into monosaccharides to be absorbed by the body.

💡Polysaccharides

Polysaccharides are complex carbohydrates made up of many monosaccharide units. In the human body, glucose molecules can be stored as polysaccharides like glycogen. The video also mentions that polysaccharides can be ingested from plant sources as starch or cellulose. However, humans cannot break down cellulose, which forms dietary fiber.

💡Dehydration reaction

A dehydration reaction is a chemical process in which a water molecule is removed to bond two smaller molecules together. In the context of carbohydrates, it is the reaction that connects monosaccharides to form disaccharides like sucrose and lactose. The video uses this term to explain how carbohydrates are formed and stored.

💡Glucose

Glucose is the primary monosaccharide used by the body for energy. It is a simple sugar with the formula C6H12O6 and is a key player in cellular respiration, producing ATP. The video describes how glucose can be consumed in various forms and converted in the liver for energy or storage.

💡Lactose intolerance

Lactose intolerance occurs when a person lacks the enzyme lactase, which is necessary to break down lactose, a disaccharide made of glucose and galactose. The video explains that without lactase, lactose remains undigested in the intestines, leading to osmotic effects like diarrhea.

💡Glycogen

Glycogen is the storage form of glucose in animals. It is a highly branched polysaccharide stored in the liver and muscles. The video explains how glucose molecules are linked together in glycogen, and how it is broken down to release energy when needed.

💡Cellulose

Cellulose is a polysaccharide found in plant cell walls. While it is composed of glucose molecules like glycogen and starch, humans lack the enzymes to break it down, making it an indigestible form of carbohydrate. The video explains that cellulose contributes to dietary fiber, aiding in digestion by bulking up stool.

💡Isomers

Isomers are molecules that have the same chemical formula but differ in the arrangement of atoms. Glucose, fructose, and galactose are isomers, each with the formula C6H12O6. The video emphasizes how these structural differences affect their function and how the body processes them.

Highlights

Carbohydrates are one of the four major macromolecules, alongside proteins, fats, and nucleic acids.

Carbohydrates are composed of carbon, hydrogen, and oxygen, similar to other macromolecules.

Monosaccharides are single sugar molecules, such as glucose, fructose, and galactose, all sharing the same chemical formula C6H12O6.

Glucose is the primary monosaccharide used for energy production in the human body.

Galactose and fructose are converted into glucose in the liver, where it can either be used for energy or stored as glycogen.

Disaccharides, such as sucrose and lactose, are formed through dehydration reactions, which involve the removal of water molecules.

Lactose intolerance occurs when the enzyme lactase is not present to break down lactose into glucose and galactose, leading to digestive issues like diarrhea.

Polysaccharides are long chains of sugar molecules and include starch (from plants), cellulose (from plants), and glycogen (from animals).

Humans can digest starch and glycogen but cannot digest cellulose, which forms dietary fiber.

Cellulose is a polysaccharide found in plant material like leafy greens and grass, but humans lack the enzymes to break it down.

Cows can digest cellulose because they possess the necessary enzymes to break down these polysaccharides.

Glycogen is the stored form of glucose in animals and is highly branched compared to plant starch.

The dehydration process links monosaccharides to form disaccharides, whereas rehydration (adding water) breaks these bonds.

The osmotic effect of undigested lactose pulling water into the intestines explains why lactose intolerance often results in diarrhea.

Fiber from indigestible polysaccharides bulks up stool and aids in digestion by pushing food through the intestines.

Transcripts

[Music]

I've run dr. Mike here let's talk about

carbohydrates as one of the four major

types of macromolecules remember you got

carbs proteins fats and nucleic acids

also known as nucleotides now

carbohydrates if we think about what

they composed of you'll find that

carbohydrates are composed of carbo

being carbon atoms hydrate talking about

water we know water is made up of

hydrogen and oxygen so carbohydrates are

made up of carbon hydrogen and oxygen

that's basically it you'll find that all

these macromolecules whether it be

proteins fats carbs or nucleic acids are

simply made up of hydrocarbons being a

bunch of carbons connected to a bunch of

hydrogen's now when we look at

carbohydrates pretty much all of them

are in this ring shaped fashion and you

can either have them alone which we call

monosaccharides meaning one sugar you

can have them connected together which

we call disaccharides so that's two

sugar molecules click together or you

can have a whole bunch of them click

together which we call polysaccharides

now the human body by mass is made up of

1% carbohydrates and predominately we

use carbohydrates for energy you'll find

carbohydrates on cells in cell membranes

you'll find them associated with genetic

material but predominantly the

functional role for carbohydrates is

going to be energy production now if we

have a look there's three main types of

monosaccharides the simple return the

simple sugars and this includes glucose

fructose and galactose which you've

probably heard of before now if you have

a look they are all made up of carbons

hydrogen's and oxygens and you'll

actually find that they have the exact

same chemical formula c6 h-12 o-6 so

there's six carbons 12 hydrogen's and

six oxygens the only difference between

those three is that they're arranged

differently so glucose which is our

primary monosaccharide this is the main

one we used to produce energy you can

see this is the arrangement of all the

carbons or the hydrogen's or the oxygens

okay you can see the carbon ring

with all the hydrogen and oxygen coming

off then when we look at fructose still

c6h12o6 it looks very similar but there

are a couple of differences same goes

for galactose very similar couple of

differences they're termed isomers of

glucose in actual fact when you ingest

foodstuffs what will happen is once it's

absorbed from the intestines into your

bloodstream it goes to your liver your

liver will convert galactose and

fructose to glucose either to use the

glucose for energy or to store the

glucose as a polysaccharide which we

term glycogen but I'll get to that in

one second now what can happen is you

can ingest these carbohydrates as

disaccharides and when you have a look

at these carbohydrates for example if

you were to connect a glucose and

galactose together you'd have to do it

through a process called dehydration

you've heard that term before

dehydration it means you don't have

enough water in your body right so a

dehydration reaction simply means you

release or you remove a water molecule

from the reaction it's very easy if we

first start off by connecting a glucose

with a fructose for example that's terms

sucrose so that's sucrose is simply a

glucose connected to a fructose the way

you do it through a dehydration reaction

is water needs to be removed water is

h2o two hydrogen one oxygen there's a

hydrogen there's a hydrogen there's an

oxygen so you remove them away and then

those two carbons can click together

that's how you form a sucrose in a

dehydration reaction when you want to

separate them it's a rehydration

reaction you're going to put that water

molecule back in now if we were to

connect glucose and galactose together

we form something that's called lactose

and some people are lactose intolerant

which means when they ingest milk

products where you predominately find

glucose and galactose stuck together

you need an enzyme in your body that

snips

off that to bonds so remember you got

that water molecule that's you've taken

away that water molecule the carbons are

held together you need to rehydrate to

break them apart and you need an enzyme

to do this rehydration process when

you're rehydrating that of lactose it's

an enzyme called lactase ASAE

for some of us we no longer produce

lactase and so we don't have the

scissors that allows for us to cut that

bond and so what happens is the glucose

and the galactose remain stuck together

and continue to move through our

intestines we need to break this down

into glucose and galactose in order for

it to get absorbed it from our

intestines into the bloodstream so we

can use it if it doesn't snap apart to

this hydration process they stay

together and it continues to move

through the digestive tract now this is

a larger molecule and when you've got

larger molecules moving in bulk

through your intestines it actually

pulls water towards it this is called an

osmotic effect and if it pulls water

towards it now your intestines are

filled with water and that goes out in

the fecal material which we call

diarrhea so this is why lactose

intolerance can result in diarrhea okay

the other thing is what if we were to

click together fructose and galactose

well in actual fact this doesn't happen

so you don't actually get a disaccharide

or fructose and galactose now like I

said fructose and galactose will

ultimately turn in at the liver to

glucose and so now we've got a whole

bunch of glucose molecules in our liver

we can either use it to form ATP energy

or we can store it and click all the

glucose molecules together to form what

we call polysaccharides which means many

sugars now there's different types you

can actually ingest polysaccharides from

plants and they are called starches or

cellulose okay or you can ingest it from

animals which is called glycogen and we

store our glucose as glycogen okay now

the thing is when you ingest a

polysaccharide a cellulose from a plant

material we don't have the enzymes that

break those bonds remember that

rehydrate the process so cellulose which

you find in leafy greens you also find

in lettuce you find even in grass for

example if we were to eat grass which we

don't do there's heaps of carbohydrates

there but we can't break them up into

these monosaccharides because we don't

have the enzymes now cows for example do

have the enzymes so they can get all the

energy they need from just eating grass

but we can't okay so what happens is we

eat lettuce for example we don't break

it down but it forms fiber so fire by

these indigestible polysaccharides that

we can't break down bulks up the stool

helps push everything through but we do

have the enzyme that breaks down starch

and glycogen okay and we can see is the

way they're stacked together a different

for cellulose it's one long linear bit

of glucose connected together starch is

a whole bunch of glucose molecules

connected together in a branch like

fashion and glycogen is extremely branch

and this is the way that we store

glucose so when we look at macro

molecules this is how carbohydrates are

stored and made