Biological Molecules - glucose, starch Monosaccharides Flashcards
Define monomer
Monomers are the smaller units from which larger molecules are
made.
Define polymers
Polymers are molecules made from a large number of monomers
joined together.
Examples of monomers
Monosaccharides, amino acids and nucleotides are examples of
monomers
what is a condensation reaction
A condensation reaction joins two molecules together with the
formation of a chemical bond and involves the elimination of a
molecule of water.
what is a hydrolysis reaction
A hydrolysis reaction breaks a chemical bond between two
molecules and involves the use of a water molecule.
what is a monosaccharide
Monosaccharides are the monomers from which larger
carbohydrates are made
single sugar units
examples of carbohydrates
sugars and starch
where are sugars found e.g. sucrose
sucrose is found in cakes and biscuits
where is starch found
starch is found in foods such as pasta and rice
Describe the structure of glucose
Glucose has a ring shape
Glucose contains 6 carbon atoms
What do all carbohydrates contain
All carbohydrates including glucose contain only the elements carbon, hydrogen and oxygen
What are sugars /monosaccharides with six carbon atoms called
Sugars with six carbon atoms are called hexose sugars/monosaccharides
What type of sugar is glucose and why?
Glucose is a hexose sugar/monosaccharide because it contains six carbon atoms
A single sugar molecules (a monosaccharide)
Draw the structure of glucose
https://static.aqa.org.uk/assets/image/0018/235440/00055366-DA00046397-DB.png
write 1 - 6 on the inside of the hexagon
then 6 on the left of the stick
Give examples of a monosaccharide
glucose, galactose, fructose
describe a key feature of monosaccharides - explain using the structure of glucose
Monosaccharides are soluble in water
Monosaccharides including glucose have a large number of OH groups.
OH groups are called hydroxyl groups
Hydroxyl groups are polar due to the small negative charge in the oxygen atom and the small positive charge on the hydrogen atom.
This means that Hydroxyl groups can form hydrogen bonds with water molecules
Due to this, monosaccharides are soluble in water
These molecules are hydrophilic
What are hydrophilic molecules
Hydrophilic (water loving)
Hydrophilic molecules all dissolve in water
Monosaccharides are ______ molecules
Monosaccharides are hydrophilic molecules
State the two forms of glucose
Alpha glucose
Beta glucose
The two different forms of glucose can also be called ______ of glucose
The two different forms of glucose can also be called ISOMERS of glucose
Draw the structures of alpha and beta glucose
https://static.aqa.org.uk/assets/image/0018/235440/00055366-DA00046397-DB.png
https://static.aqa.org.uk/assets/image/0008/235439/00055366-DA00046396-DB.png
Describe the similarity between alpha and beta glucose
In both isomers of glucose, carbon 1 is bonded to a hydrogen atom and also to an OH (hydroxyl) group.
Describe the difference between alpha and beta glucose
The key difference between the two isomers of glucose is the position of the hydroxyl group on carbon 1
If the carbon 1 hydroxyl group
points below the plane of the ring, then this isomer is called alpha glucose
If the carbon 1 hydroxyl points above the plane of the ring, this this isomer is called beta glucose
https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcQtVcnkOpYu6-eFvrKkMGS7Zeacf_nG260b7BNijnErTnPs5fFs - beta glucose
https://www.youtube.com/watch?v=8GDXf2LrrUg&list=PL9IouNCPbCxVF0IVlwiILW-TmAMYX5OO7&index=4 at 1:43
Describe how disaccharides are formed from monosaccharides
Disaccharides are formed by the condensation of two
monosaccharides:
Describe what happens when two molecules of alpha glucose react together
When two molecules of alpha glucose react together, the disaccharide maltose is made.
Also when the disaccharide is made, a molecule of water is also produced
The water molecules is formed from a hydrogen atom from one of the monosaccharides and a hydroxyl group from the other
This reaction is called a condensation reaction since the reaction forms a water molecule
The glycosidic bond is formed between carbon 1 on one alpha glucose and carbon 4 on the other alpha glucose
When a disaccharide is made from two monosaccharide was is also produced and how?
Also when the disaccharide is made, a molecule of water is also produced
The water molecules is formed from a hydrogen atom from one of the monosaccharides hydroxyl group and a hydroxyl group from the other
This reaction is called a condensation reaction since the reaction forms a water molecule
a disaccharide is formed from two monosaccharides. What type of reaction is this and why?
This reaction is called a condensation reaction since the reaction forms a water molecule
What is a glycosidic bond
The chemical bond formed between the two molecules of alpha glucose
A condensation reaction between two monosaccharides forms a _____________
A condensation reaction between two monosaccharides forms a
glycosidic bond.
Draw the reaction for the formation of maltose
https://o.quizlet.com/pVG3e0ugJZiYwjQlseKHVw.jpg
How are the two alpha glucose molecules bonded together
What type of glycosidic bond is in the disaccharide maltose
Maltose has a 1,4 glycosidic bond
Explain how maltose has a 1,4 glycosidic bond
Why it is called a 1,4 glycosidic bond
The glycosidic bond is between carbon 1 on one alpha glucose and carbon 4 on the other alpha glucose
What type of reaction a disaccharides formed in
Disaccharides are formed in a condensation reaction (water molecule is also produced)
Describe what happens when you add water to a disaccharide
If water is added to the disaccharide, the glycosidic bond breaks.
This converts the disaccharide back to the original monosaccharides
This is called a hydrolysis reaction
What is a hydrolysis reaction
A reaction where water is added to the disaccharide which breaks the glycosidic bond
This converts the disaccharide back to the original monosaccharides
Where are hydrolysis reactions normally carried out and by what
In cells this reaction is normally carried out by enzymes
State some disaccharides
Maltose
Sucrose
Lactose
Are examples of disaccharides.
How is sucrose made
Glucose (alpha) + fructose = sucrose
The disaccharide sucrose is formed from the monosaccharides glucose and fructose
How is lactose made
Glucose (alpha) + galactose = lactose
The disaccharide lactose is formed from the monosaccharides glucose and galactose
Why is glucose being extremely soluble in water a problem
If a cell contains a large amount/(high conc. of in cell) dissolved glucose, this can cause water to move into the cell by osmosis
How do plant cells solve the problem of water moving into cells by osmosis (due to glucose’s solubility) and why?
To solve this problem, plant cells store glucose as starch - because starch is insoluble
What is a polysaccharide
Polysaccharides are formed by the condensation of many glucose
units.
Polysaccharides are formed when more than two monosaccharides are joined together by condensation reactions
What two molecules/polysaccharides does starch consist of
Amylose
Amylopectin
Describe the structure of amylose
Amylose is an unbranched polymer of alpha glucose molecules (joined by 1,4 glycosidic bonds)
If a large number of alpha glucose molecules are joined together, then the polysaccharide amylose is made.
The alpha glucose molecules are joined by 1,4 glycosidic bonds
Each bond forms in a condensation reaction producing a molecule of water
The amylose molecule then twists into a compact helix with hydrogen bonds forming between glucose molecules along the chain
Amylose forms a helix which is held in place by hydrogen bonds between glucose molecules
This helical shape helps to make starch a very compact molecule
In amylose how does each bond form
Each bond forms in a condensation reaction producing a molecule of water
What is starch
Starch is a store of glucose
If a cell needs glucose, what happens
If a cell needs glucose, water is used to break the glycosidic bonds
This converts the polysaccharide back to the original monosaccharides (glucose)
This is called a hydrolysis reaction
When the cell needs glucose, enzymes are used to break the glycosidic bonds in starch
This is a hydrolysis reaction and requires water
The enzymes that break down starch act at the ends of the molecules
Because amylopectin has a large number of branches, this means that it has a large number of ends.
Because of this the enzymes can break down starch rapidly
Draw the structure of amylose
https://o.quizlet.com/pVG3e0ugJZiYwjQlseKHVw.jpg
but many
Where do we find starch
We find starch in starch grains. /plants
State the advantage of the structure of amylose in starch / structure relate to function
Amylose twists into a helix
This helical shape helps to make starch a very compact molecule
SO A lot of it can be stored in a small space
Describe the structure of amylopectin
Amylopectin is a polymer of alpha glucose molecules joined by 1,4 glycosidic bonds
Amylopectin chains have a branch every 25-30 glucose molecules
A branch is another chain of alpha glucose molecules joined by 1,4 glycosidic bonds
The branch is connected to the main chain by a glycosidic bond.
The glycosidic bond is between carbon 1 of one of the alpha glucose molecules and carbon 6 of the other alpha glucose molecules.
This is called a 1,6 glycosidic bond
The glucose molecules at the branch points are joined by 1,6 glycosidic bonds.
Amylopectin is a heavily branched molecule
Regarding amylopectin, what is a branch
A branch is another chain of alpha glucose molecules joined by 1,4 glycosidic bonds
In amylopectin, how is the branch connected to the main chain
The branch is connected to the main chain by a glycosidic bond.
Describe the glycosidic bond between the branch and main chain in amylopectin
The branch is connected to the main chain by a glycosidic bond.
The glycosidic bond is between carbon 1 of one of the alpha glucose molecules and carbon 6 of the other alpha glucose molecules. This is called a 1,6 glycosidic bond
Draw the structure of amylopectin
Draw a simplified structure of amylopectin
Which polysaccharide is unbranched and which polysaccharide is branched
Amylose - unbranched polysaccharide
Amylopectin - branched polysaccharide
How is the structure of starch related to its function in cells
Amylose forms a tight helix. This makes starch compact
This means/allows for starch can store a large amount of glucose molecules for its size
Starch is insoluble in water
This means that starch does not cause water to enter the cell by osmosis
Because amylose and amylopectin are polymers, they are two large to diffuse through the cell membrane and pass out of the cell
When the cell needs glucose, enzymes are used to break the glycosidic bonds in starch
This is a hydrolysis reaction and requires water
The enzymes that break down starch act at the ends of the molecules
Because amylopectin has a large number of branches, this means that it has a large number of ends.
Because of this the enzymes can break down starch rapidly
insoluble - therefore doesnt affect water potential - so water is not drawn into cells by osmosis - means cell does not cell - makes it good for storage
being large and insoluble - does not diffuse out of cells
compact - a lot of it can be stored in a small placed
when hydrolysed forms alpha glycose - which is easily transported and readily used in resp.
branched form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly
has lots of branches (more than starch), so has more ends that can be acted on simultaneously by enzymes.
it is therefore more rapidly broken down to form glucose molecules, which are used in respiration
