Carbohydrates AP Biology Topics 1.4 & 1.5

Summary

This educational video script delves into the chemistry of carbohydrates, focusing on their structure and function. It covers the photosynthesis process where plants convert carbon dioxide and water into glucose. The script explains different types of monosaccharides like glucose, fructose, and galactose, and their role in forming disaccharides and polysaccharides through dehydration synthesis. It further discusses the functions of polysaccharides in plants, such as starch for energy storage and cellulose for structural support, and in animals, like glycogen for short-term energy storage. The script also touches on the conversion of excess glucose into fatty acids for long-term energy storage and the role of hydrolysis in breaking down carbohydrates during digestion.

Takeaways

• 🌿 **Photosynthesis**: Plants convert carbon dioxide and water into glucose, a carbohydrate, through photosynthesis.
• 🍬 **Monosaccharides**: Glucose, fructose, and galactose are examples of monosaccharides, which are single sugars composed of carbon, hydrogen, and oxygen.
• 🔗 **Disaccharides**: Two monosaccharides can join together through dehydration synthesis to form a disaccharide, like sucrose (glucose + fructose).
• 🔄 **Hydrolysis**: The process of breaking down disaccharides into monosaccharides by adding water is called hydrolysis.
• 🌱 **Starch and Cellulose**: Starch is a polysaccharide used for energy storage in plants, while cellulose provides structural support.
• 📦 **Polysaccharides**: Polysaccharides are long chains of glucose molecules, including starch, glycogen, and cellulose, each serving different functions.
• 🥩 **Glycogen**: In animals, glycogen is the storage form of glucose, similar to starch in plants, and is stored in the liver and muscles.
• 🍔 **Carbohydrate Metabolism**: Excess glucose is converted into fatty acids for long-term energy storage when glycogen stores are full.
• 🏋️‍♂️ **Exercise and Glycogen**: During exercise, stored glycogen is broken down into glucose to raise blood sugar levels and provide energy.
• 🔑 **Structural Differences**: The structure of polysaccharides, such as the straight chains in cellulose and branched chains in glycogen, determines their function.

Q & A

What are the primary elements used to build carbohydrates?

Carbohydrates are primarily built using carbon (C), hydrogen (H), and oxygen (O), which plants obtain from carbon dioxide in the air and water from the soil.

How does the process of photosynthesis contribute to the formation of glucose?

Photosynthesis is the process by which plants rearrange carbon dioxide and water into glucose, a simple sugar. This process involves the rearrangement of these molecules to form glucose, which has a hexagonal shape.

What is the chemical formula for glucose?

The chemical formula for glucose is C6H12O6.

What is the scientific term for a single sugar, and what does it mean?

The scientific term for a single sugar is 'monosaccharide', where 'saccharide' means sugar and 'mono' means one.

How do glucose and fructose differ in their molecular structure?

Glucose is a six-carbon sugar, while fructose is a five-carbon sugar. Both are composed of carbon, hydrogen, and oxygen.

What is a disaccharide and how is it formed?

A disaccharide is a carbohydrate formed by the joining of two monosaccharides through a dehydration synthesis reaction, which involves the removal of a water molecule to form a covalent bond between the two sugars.

What is the term for the bond formed between two monosaccharides in a disaccharide?

The bond formed between two monosaccharides in a disaccharide is called a glycosidic linkage.

How does the process of hydrolysis relate to the digestion of disaccharides?

Hydrolysis is the process of breaking down a disaccharide by adding a water molecule, which is facilitated by enzymes in saliva. This process splits the disaccharide into its constituent monosaccharides.

What are the two main functions of glucose in plants?

In plants, glucose serves two main functions: it can be used as an immediate energy source, or it can be stored for later use, often in the form of starch or cellulose.

What is the difference between starch and cellulose in plants?

Starch is an energy storage polysaccharide in plants, while cellulose provides structural support and forms the cell walls. The difference lies in the type of glycosidic linkages between glucose monomers, with starch having alpha linkages and cellulose having alternating alpha and beta linkages.

Why is cellulose indigestible to humans?

Cellulose is indigestible to humans because we lack the enzymes necessary to hydrolyze the glycosidic linkages between the glucose monomers in cellulose, which are alpha and beta alternately linked.

How does the body manage excess glucose after a carbohydrate-rich meal?

When blood sugar levels rise after consuming carbohydrates, the body responds by releasing insulin, which signals the liver and muscles to store excess glucose as glycogen through a process called dehydration synthesis.

What happens when the body's glycogen storage is full and blood sugar levels remain high?

If glycogen storage is full and blood sugar levels are still high, the body converts excess glucose into fatty acids, which are then stored as fat for long-term energy storage.

Outlines

00:00

🌿 Carbohydrates: Structure and Function

This paragraph introduces the topic of carbohydrates, focusing on their structure and function, particularly in the context of AP Biology's unit on the chemistry of life. It explains how plants use carbon dioxide and water to create glucose through photosynthesis, highlighting the chemical formula for glucose (C6H12O6). The paragraph also discusses monosaccharides, specifically glucose, fructose, and galactose, and how they are formed from carbon dioxide and water. The concept of dehydration synthesis is introduced, explaining how two monosaccharides can combine to form a disaccharide through this process, creating a glycosidic linkage.

05:02

🌱 Plant Utilization of Glucose

The second paragraph delves into the dual functions of glucose in plants: energy storage and structural support. It describes how plants convert excess glucose into polysaccharides, which are chains of glucose molecules linked by glycosidic linkages. The paragraph introduces three main types of plant polysaccharides: starch (for energy storage), cellulose (for structural support), and briefly mentions chitin. It explains the process of photosynthesis, where plants convert glucose into starch for energy storage and cellulose for building cell walls. The difference between starch and cellulose is highlighted, with starch being digestible by humans due to our enzymes' ability to hydrolyze the glycosidic linkages, while cellulose is indigestible due to the different arrangement of glucose monomers.

10:03

🍽️ Carbohydrate Metabolism in Animals

Paragraph three explores the role of carbohydrates in animal metabolism, particularly in humans. It discusses how excess glucose from digestion is managed by the body to maintain homeostasis. The liver and muscles store excess glucose as glycogen, a polysaccharide similar to plant starch but used for short-term energy storage. When blood sugar levels are too high, insulin is released, signaling the liver and muscles to store glucose. If glycogen storage is maxed out, the body converts excess glucose into fatty acids for long-term energy storage. The paragraph also explains how exercise can deplete glycogen stores, leading to an increase in hunger as the body signals the need to replenish these stores.

15:04

🏋️‍♂️ Glycogen and Exercise

The final paragraph focuses on the role of glycogen during physical activity. It explains how the hormone glucagon triggers the hydrolysis of glycogen into monosaccharides to raise blood sugar levels during exercise, providing the necessary energy. The paragraph also touches on the different structural forms of carbohydrates, comparing the straight chains of cellulose, the single chains of amylose (a component of starch), and the branched structure of glycogen, which allows for efficient energy release by breaking off sections of glucose monomers.

Keywords

💡Carbohydrates

Carbohydrates are organic molecules that are composed of carbon, hydrogen, and oxygen. They are one of the primary sources of energy for living organisms and are a key focus of the video. The script discusses how plants produce carbohydrates like glucose through photosynthesis, which involves rearranging carbon dioxide and water into glucose molecules. This process is fundamental to understanding the chemistry of life.

💡Photosynthesis

Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose or other sugars. The video explains that during photosynthesis, plants use carbon dioxide from the air and water from the soil to produce glucose. This process is central to the video's theme of exploring the structure and function of carbohydrates.

💡Monosaccharides

Monosaccharides, also known as simple sugars, are the simplest form of carbohydrates and cannot be broken down into simpler sugars. The script identifies glucose, fructose, and galactose as examples of monosaccharides. Glucose, a six-carbon monosaccharide, is highlighted as a primary product of photosynthesis and is fundamental to the video's discussion of carbohydrate structure and function.

💡Disaccharides

Disaccharides are carbohydrates composed of two monosaccharide units joined together by a dehydration synthesis reaction. The video uses sucrose, which is composed of glucose and fructose, as an example of a disaccharide. The concept is important for understanding how simple sugars can be linked to form more complex molecules.

💡Polysaccharides

Polysaccharides are complex carbohydrates composed of long chains of monosaccharide units. The video discusses starch, glycogen, and cellulose as examples of polysaccharides. Starch is highlighted as an energy storage molecule in plants, while glycogen serves a similar function in animals. Cellulose, on the other hand, provides structural support in plant cell walls.

💡Glycolysis

Glycolysis is a metabolic process that occurs in the cytoplasm of cells, where one molecule of glucose is broken down into two molecules of pyruvate, releasing a small amount of energy. The video mentions glycolysis as the starting point of cellular respiration, which is crucial for understanding how organisms utilize carbohydrates for energy.

💡Dehydration Synthesis

Dehydration synthesis is a chemical reaction that involves the removal of a water molecule from two molecules, allowing them to join together. In the context of the video, this reaction is used to form disaccharides and polysaccharides by linking monosaccharide units together. This process is essential for the formation of complex carbohydrates from simpler sugar units.

💡Hydrolysis

Hydrolysis is the reverse of dehydration synthesis, where a water molecule is added to break a bond in a molecule. The video explains that hydrolysis is used by enzymes in saliva to break down disaccharides like sucrose into monosaccharides. This process is critical for the digestion of carbohydrates and the release of energy.

💡Glycosidic Linkage

A glycosidic linkage is the type of covalent bond formed between two monosaccharides during dehydration synthesis. The video emphasizes that this bond is what holds monosaccharides together in disaccharides and polysaccharides. Understanding glycosidic linkages is key to comprehending the structure of complex carbohydrates.

💡Cellulose

Cellulose is a polysaccharide that provides structural support in plant cell walls. The video explains that cellulose is made up of glucose molecules linked together in a way that alternates between alpha and beta forms, making it indigestible to humans. However, herbivores have bacteria that can break these bonds and access the energy stored in cellulose.

💡Glycogen

Glycogen is an animal polysaccharide that stores glucose in the liver and muscles for short-term energy needs. The video describes how glycogen is formed through dehydration synthesis and can be broken down back into glucose through hydrolysis when blood sugar levels need to be raised, such as during exercise.

Highlights

Carbohydrates are essential organic molecules built from carbon dioxide and water during photosynthesis.

Glucose is a hexagon-shaped monosaccharide with the chemical formula C6H12O6.

Monosaccharides include glucose, fructose, and galactose, all composed of C, H, and O.

Disaccharides are formed by joining two monosaccharides through a dehydration synthesis process.

The bond formed between monosaccharides in a disaccharide is called a glycosidic linkage.

Cellular respiration begins with glycolysis, which is the splitting of sugar molecules.

Plants use glucose for energy storage or to build structural components like cell walls.

Starch is a polysaccharide used by plants for energy storage, found in high amounts in potatoes.

Cellulose is a polysaccharide that provides structural support and forms the cell walls in plants.

Humans cannot digest cellulose due to the lack of enzymes to break the glycosidic linkages.

Glycogen is the animal equivalent of starch, used for short-term energy storage.

The human body converts excess glucose into fatty acids for long-term energy storage.

Fatty acids are a compact form of potential energy that can be carried by the body.

Exercise depletes stored glycogen, leading to an increase in hunger as the body signals the need to replenish energy stores.

The structure of carbohydrates varies; cellulose forms rigid chains, starch forms straight chains, and glycogen has a branched structure.

Herbivores have bacteria that help them break down cellulose to obtain energy.

The body maintains homeostasis by regulating blood sugar levels with the help of insulin and glucagon.

Transcripts

okay so in this video we're gonna look

at the structure and function of

carbohydrates if you're in ap biology

this is unit 1 chemistry of life with a

major focus on one point four and one

point five okay so when we look at life

on Earth and what we have available to

build the organic molecules particularly

carbohydrates plants are going to take

that carbon dioxide and water from the

air and that's where they get the C H

and O in order to build carbohydrates so

here this carbon dioxide and this water

is going to be rearranged into a

molecule of glucose during the process

of photosynthesis so here this glucose

has CH and O and comes in like this

hexagon shape here and really um here's

what it is though a single sugar glucose

now when we look at these macromolecules

plants give their carbon hydrogen and

oxygen from the air and from the water

in the soil now ultimately for other

macromolecules they'll need nitrogen and

phosphorus but for carbohydrates we're

looking at C H and O okay so the

chemical formula for glucose is c6h12o6

all right so when we talk about sugars

or carbohydrates um the scientific name

is mono saccharide for one single sugar

so saccharide means sugar and mono means

one when we look at the different single

sugars or monosaccharides on earth we

have glucose which is going to be our

main monosaccharide and then we have

fructose which is fruit sugar and if you

look at the differences between these

two monosaccharides you can see that

glucose comes in a six carbon structure

and then fructose is five carbon sugar

they both however are made of C H and O

and then we have galactose and galactose

is part of the sugars in the breast milk

so that one is a little bit less common

on earth and so when we look at these

though they were all made

carbon dioxide and water during the

process of photosynthesis so if you were

to add however two sugars together like

this this is called a disaccharide dye

meaning two sugars and so if we think

about how do you join two

monosaccharides or two monomers together

in order to build a disaccharide well

we're going to do dehydration synthesis

and we're going to remove a water so now

we have a covalent bond right here in

the middle between the two

monosaccharides and the process of

removing a water to build is called

dehydration synthesis so this type of

bond though does have a name so we look

at the bond that was just formed by

dehydration synthesis removing a

hydrogen and a hydroxyl group from the

two monosaccharides this bond is called

a glycosidic linkage a lot of times when

you see the prefix with a GTL why it's

in reference to sugars or carbohydrates

so when we get to cellular respiration

that begins with glycolysis which is a

splitting of sugar okay so let's go

ahead and see when we take a

monosaccharides or a glucose and another

glucose an enzyme will actually

facilitate this reaction and remove the

water in dehydration synthesis and now

we have our disaccharide now enzymes are

pretty cool proteins that can be used

over and over and over again so here

we're taking monosaccharides to build

disaccharides

so here the monomer is a monosaccharide

or a glucose and then we don't quite

have a polymer but we do have a two

sugar molecule called disaccharide

now if we were to digest a disaccharide

like when you eat white table sugar for

example that's a sucrose molecule made

of glucose and fructose and what will

happen is our enzymes

saliva are going to add a water to split

in the process called hydrolysis so when

we split bonds by adding water that's

called hydro lysis or adding water to

split okay so let's talk a little bit

more about carbohydrates and their

functions so here we have chloroplasts

and chloroplasts do photosynthesis in

both the light and the dark reactions so

when a planet is going through

photosynthesis it's building technically

g3p but if you take a g3p and a g3p it

builds glucose together so plant is

building glucose and now what does it do

with it right well there's actually two

different functions that a plant can use

glucose for so here again as it does

photosynthesis it's going to one of the

functions could be that it saves the

extra excess glucose for a day when it's

not sunny or something so when a plant

though takes these excess glucose

molecules and builds them into a chain

there's many glucose molecules so we

call this poly saccharide so we look at

carbohydrates the monomer or the

building block is a single sugar a

single monosaccharides

this is called glucose then a polymer is

many glucose molecules so here we have

our polymer that we call a poly

saccharide now in between each of these

um glucose molecules these monomers is a

glycosidic linkage so in order to build

this molecule you see here this

polysaccharide we would actually have

produced 1 2 3 4 5 water molecules in

the building of this polysaccharide now

in our class there are there's actually

4 different types of polysaccharides

this one here we don't talk too much

about chitin but chitin is actually the

polysaccharide used to build

exoskeletons in lobsters and crabs and

beetles but this one we don't talk about

too much

now the other three are important and

all three of these starch glycogen and

cellulose they are all polysaccharides

all made from repeating glucose

molecules however they do serve

different functions so if you were to

compare and contrast them one thing they

have in common is they're all a chain of

glucose molecules okay so let's go ahead

and see what plants do with these

polysaccharides so in plants that are

two main types of polysaccharides we

have starch and we have cellulose so

starch is going to be the energy storage

for plants when you eat a potato you

were eating starch and that is a chain

of glucose molecules being saved by the

plant when you grow up and you hear that

plants make their own food this is it

they're making glucose and they're

storing it for times when they need

energy and then plants will use

cellulose another type of polysaccharide

however cellulose is used for structural

reasons this is what builds the cell

walls in plants so when we look at the

polysaccharides in plants they are both

a chain of glucose molecules however one

is for energy storage and one is for

structural support and then fiber for us

as well

so if I have the leaves of a plant doing

photosynthesis and it's gonna save the

glucose molecules for later the

photosynthesis happens in the leaves but

the sugars will travel from the leaves

and then be stored here in the plant now

plants though so this molecule is gonna

be starch an energy storage

polysaccharide however a plant also

grows and when you think about well how

does it build new cells and new cell

walls those cell walls are going to be

made from glucose as well however the

bonds from those glucose is joining

together are going to be slightly

different than the bonds you find in

starch and it's these the different ways

these

two monomers joined together that

results in the different properties okay

so let's go ahead and look at cellulose

so silos are those rigid AB cell walls

and plants to offer support and

protection now another cool thing about

cellulose is that we do not have the

enzymes to hydrolyze cellulose we cannot

break down this chain of glucose and

therefore cellulose is not free

available energy you will not get enough

energy to support life if you just eat

lettuce every day there's not enough

energy in it to support us you may be

thinking about herbivores though and

herbivores have bacteria in their

stomachs and intestines to help them

break these bonds and break it down and

get the energy from these molecules okay

so let's go ahead and see what makes

them different well we have two

different types of glucose we have the

alpha ring form and we have the beta

ring form and you can kind of see it

here slight variations and the two

glucose molecules now this is

significant for when they join by

dehydration synthesis to form a

polysaccharide so in starch it is made

of alpha alpha alpha alpha glucose

monomers joined together now in

cellulose it's made of alpha glucose

beta glucose alphabet glucose beta

glucose so the it like alternates a type

of glucose monomers so if i zoom into

those glycosidic linkages I see this

linkage and this one and they are

different we can to adjust and break

apart the monomers in starch however we

cannot break that glycosidic linkage

between an alpha glucose and a beta

glucose so therefore cellulose is

indigestible by us so starch while we

have the enzymes that can do hydrolysis

we can add waters and break that

polysaccharide down into its individual

monomers of glucose however cellulose is

hard

to digest and we do not have the enzymes

to break those bonds therefore it

remains intact as we eat it okay now for

animals we also have a polysaccharide

but we're not gonna use starch because

I'm not a plant instead we eat those

plants and we eat that starch and we

don't use cellulose because we don't

build cell walls but let's take our

blood sugar for example we have sugar

flowing in our blood and we try real

hard to maintain homeostasis and keep

things balanced however when we eat a

meal that's full of sugar carbohydrates

as our enzymes hydrolyze and break down

those large carbohydrates into

individual sugars our blood sugar Rises

and now we're not in homeostasis anymore

so our body kind of like had too much

sugar we have to do something about it

and so what we do is we have our liver

and our muscles and our liver at our

muscles store this extra sugar for us we

can store about 24 hours worth of sugar

in our livers so what happens is when

our blood sugar is too high our pancreas

will release insulin and that will

communicate to our liver and our muscles

that it's time to take sugar out of our

blood and store it so that's a really

cool thing so right now as that second

sugar came down dehydration synthesis is

happening right here to form a

glycosidic linkage

here's another glycosidic linkage etc so

we end up with the chain of glucose

monomers joined together in our liver

and our are we back in homeostasis not

quite we still have a couple of extra

glucose but for now the name of this

polysaccharide in animals is glycogen so

its purpose however is very similar to

starch in a plant while starch in a

plant is storing glucose for energy this

glycogen stores our glucose for energy

for like a short-term amount for us as I

mentioned earlier we store about 24

hours

the glucose in our liver and we store it

as the polysaccharide called glycogen so

let's say though that your your liver is

full it's at capacity you can't fit any

more glucose molecules in it like your

glycogen czar maxed out and you still

have too high of blood sugar well then

your body has the ability now let's

think about this your carbohydrates are

made of C H and O your lipids are made

of C H and O so what we can do with that

excess sugar that excess glucose is we

actually convert it into fatty acids you

can see all the hydrogen's and carbons

here we call this a fatty acid which is

a non-polar molecule it's a part of the

lipid category of macromolecules and so

what we'll do is that's how we're gonna

take that extra sugar out of our blood

and now the cool thing about fatty acids

is this we are saving this potential

energy and we can carry it around with

us so this fat is actually like a

survival mechanism for humans we eat

when we have a lot of food available to

us and then any energy we don't need in

the next 24 hours we can save for later

for times when we don't have access to

food so these hydrocarbons right here

are actually a lot of potential energy

and a nice compact shape being carried

around with us okay so when we look back

at homeostasis um let's say you go and

exercise well as you exercise you're

gonna use that blood sugar to power your

workout and this is where that stored

glycogen so the hormone is glucagon but

this polysaccharide was glycogen and

that's where we will actually do

hydrolysis so right here we're gonna do

how this hormone right here is going to

activate an enzyme that will do

hydrolysis to break that polysaccharide

into monosaccharides and Rhea

or right yeah raise our blood sugar back

so we can continue our workout this

empty liver here is also why you're

really hungry after you exercise

that's your brains way of telling you Oh

fill your liver back up okay so um now

when we look at the different shapes of

carbohydrates

you can see how cellulose which forms

like a rigid cell wall so it makes sense

that they're in very straight chains and

then starch um it amylose is our main

one is like a a single line a chain of

glucose monomers and then look at this

glycogen though we can just its branched

and we can just break off like sections

I have these carbohydrates to add to our

blood sugar to keep us on homeostasis

alright good job