1A | Biological Molecules Flashcards
What is a Polymer?
Polymers are large, complex molecules made from a high (3 or more) number of monomers joined together.
Give 2 examples of monomers.
Monosaccharides (Glucose, Galactose, etc.) Nucleotides Amino Acids Fatty Acids Glycerol
Give at least 2 elements that all carbohydrates have in common.
O (Oxygen)
C (Carbon)
H (Hydrogen)
Carbohydrates are made from monomers.
Give the more specific name for these monomers.
Monosaccharides
Glucose is a Hexose sugar.
Given this information, how many carbon atoms does it have?
6
List the 2 isomers of Glucose.
Alpha Glucose
Beta Glucose
Draw the structure of Alpha glucose.
https://static.aqa.org.uk/assets/image/0018/235440/00055366-DA00046397-DB.png
Draw the structure of Beta glucose.
https://static.aqa.org.uk/assets/image/0008/235439/00055366-DA00046396-DB.png
Describe the difference between Beta and Alpha Glucose.
In Beta glucose, the hydroxide on the right of the molecule is at the top.
In Alpha glucose, the hydroxide on the right of the molecule is at the bottom.
Hydroxide = OH
What is a condensation reaction?
A condensation reaction is when two molecules join together with the formation of a new chemical bond.
A water molecule is released when the bond is formed.
What reaction joins monosaccharides together?
Condensation
What is a glycosidic bond?
A glycosidic bond is the chemical bond formed between two monosaccharides when they are joined together by a condensation reaction.
What is a disaccharide?
A disaccharide is formed when two monosaccharides are joined together.
Draw two alpha glucose molecules near each other and draw a box over the atoms that will be lost when they join together in condensation.
https://media.discordapp.net/attachments/352951793187029005/825440516098228224/unknown.png
Draw two alpha glucose molecules joined together.
What type of ‘sugar’ is this?
Name the molecule created.
Draw a box over the glycosidic bond.
https://media.discordapp.net/attachments/352951793187029005/825440866969452594/unknown.png
+H2O must be included.
What monomers are made from Maltose?
Two molecules of alpha glucose.
What monomers are made from Sucrose?
One glucose molecule and one fructose molecule.
What monomers make up Lactose?
One glucose molecule and one galactose molecule.
List 3 disaccharides.
Lactose
Sucrose
Maltose
What is a Hydrolysis reaction?
A hydrolysis reaction is a reaction wherein the chemical bond between monomers are broken, with the use of a water molecule.
Here is a molecule of Maltose:
https://media.discordapp.net/attachments/352951793187029005/825440866969452594/unknown.png
Hydrolyze the molecule.
https://media.discordapp.net/attachments/352951793187029005/825443016416165958/unknown.png?width=1440&height=483
Remember, two alpha glucose molecules will have bonded at their hydroxide area. One molecule loses OH, the other loses H thus H2O and remaining O in the middle - just add them back.
Special attention should be paid to the fact that at the bonding area you just severed [OH] and [HO] are in a different order - while not doing it in correct order doesn’t lose you marks, it may be useful to keep this information as H faces outside the molecule on both sides, not O.
Which is a reducing sugar and which is a non-reducing sugar?
Maltose Sucrose Fructose Lactose Galactose Glucose
Reducing Non-reducing Reducing Reducing Reducing Reducing
Are all monosaccharides reducing sugars?
If not, list one that isn’t.
Yes
All are reducing.
Are all disaccharides reducing sugars?
If not, list one that isn’t.
No
Sucrose
What test can be used to check for the presence of sugars?
The Benedict’s Test
What solution in the Benedict’s Test is specifically used to check for sugars?
Benedict’s Reagent
Describe how we would use the Benedict’s Test to check for sugars.
You add Benedict’s reagent (which is blue) to a sample in a container such as a beaker and heat it in a water bath that’s been brought to a boil.
If the test is positive, the sample will form a colored precipitate (solid particles suspended in the solution), which must generally be green, yellow, orange or brick red.
Color itself is not a scientific metric for how concentrated a reducing sugar is in the Benedict’s Test.
An investigator has performed the Benedict’s Test on two samples. She wants to find (scientifically) which reducing sugar is more concentrated. They can’t just look at the color for this as they’re the same color.
Describe the 2 techniques she can do.
After doing the Benedict’s Test, filter the solution of one sample, which should leave the precipitate by itself. You must then weigh the precipitate on a balance.
Do the exact thing for the second sample, filtering and then weighing the precipitate.
The one that is heaver as shown from how heavy it is, by the weight, is more concentrated.
Describe the Benedict’s Test for non-reducing sugars.
If the result of your reducing sugars test was negative, there could still be a non-reducing sugar present.
To test for non-reducing sugars, like sucrose, first you have to break them down into monosaccharides - all monosaccharides are reducing.
You can do this by getting a new sample of the test solution, which should be in a container like a beaker, adding dilute hydrochloric acid to it and carefully heating it in a water bath that’s been brought to a boil. You then neutralize the sample with sodium hydrogencarbonate.
Carry out the rest of the test like you would normally in the reducing sugars test from this point forwards - adding Benedict’s Reagent.
If the test for non-reducing sugars is positive, it will form a colored precipitate.
If the test’s negative, the solution will stay blue.
An investigator carries out the non-reducing sugars test and finds the sample stays blue.
What does this imply?
The sample contains no sugar.
An investigator wants to find out if a sugar is non-reducing.
He does the non-reducing sugars test without doing the reducing sugars test first and gets a positive result.
Explain why, using your knowledge of the non-reducing Benedict’s Test, that the sample the investigator used may not be non-reducing even though the non-reducing result was positive.
.
The reason why you cannot conclude the sample was non-reducing is because the non-reducing Benedict’s test signals positive for the presence of any sugar.
This is due to the fact that Hydrochloric acid is used, which breaks glycosidic bonds from disaccharides and polysaccharides and makes them monosaccharides, which are all reducing.
As a result of this, you do not know if the investigator’s sample was specifically non-reducing, as the test has the ability to signal positive to the presence of a sample that initially had monosaccharides thus you cannot conclude it was a disaccharide without doing the test for reducing sugars.
An individual carries out the benedict’s test for sugars. on two samples.
Both samples are the same color and he is unable to distinguish which one is more concentrated.
Aside from the ‘filter and weigh precipitate’ technique, outline one other thing he can do to find which sample is more concentrated.
Use a colorimeter to measure the absorption of light from both samples.
A higher absorption means that the concentration of the sample is higher. Compare both absorptions to find out which samples are both concentrated (the one which is higher will be).
An investigator carries out the benedict’s test for reducing sugars.
The color is blue.
Is this negative or positive?
Using your knowledge of the test for reducing sugars, does this mean the sample used has no sugars?
Negative
This does not mean the sample has no sugars - it may be non-reducing.
Blue Brick Red Yellow Orange Green
From least concentrated to most concentrated reducing sugar, list these in order.
Blue Green Yellow Orange Brick Red
What is a Polysaccharide?
A polysaccharide is formed when more than two monosaccharides are joined together by condensation reactions.
What is Starch’s role in plants?
Starch is the main energy storage material in plants, thus it is used to store energy.
What is starch a mixture of?
Starch is a mixture of two polysaccharides of alpha glucose - amylose and amylopectin.
What is Amylose?
Amylose is a long, unbranched chain of alpha glucose.
The angles of the glycosidic bonds give it a coiled structure, and thus it becomes compact, therefore it is a very good molecule for storage because you can fit more in to a small space.
What is Amylopectin?
Amylopectin is a long, branched chain of alpha glucose.
It’s side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily, which means that glucose can be released at a faster rate when needed.
List one feature of starch that make it desirable as the main source of energy storage in plants.
Starch is insoluble in water and doesn’t affect water potential, so it doesn’t cause water to enter cells by osmosis, which would make them swell otherwise.
This makes it good for storage.
Give the solution that is used for testing starch.
Iodine (dissolved) in potassium iodide.
Describe how an individual can test for starch on a sample.
Add iodine dissolved in potassium iodide to the test sample. If there is starch present, the sample changes from brownish-orange to a dark blue-black color.
An investigator adds a drop of Iodine dissolved in potassium iodide onto a sample.
The iodine’s color is dark blue-black.
What does this mean for the sample?
The sample has a presence of starch - the iodine test for starch is positive.
An investigator adds a drop of iodine dissolved in potassium iodide onto a sample.
The Iodine’s color is brownish-orange.
What does this mean for the sample?
The sample has no presence of starch - the iodine test for starch is negative.
What is Glycogen’s role in Animals?
Glycogen’s main role in animals is to store energy, as it is the main energy storage material in animals.
An animal has excess glucose.
What does this get turned into?
Glycogen for storage.
Describe and explain the structure of Glycogen.
Glycogen is a highly branched, compact molecule made of chains of alpha glucose which means that a lot of the molecule can be fit into a small place.
The fact it’s highly branched means that the molecule can be broken down fast therefore the release of glucose is faster.
What is Cellulose?
Cellulose is a polymer that is made of long, unbranched chains of beta-glucose.
Cellulose’s structure is formed by straight chains, which sections are linked together by hydrogen bonds to form strong fibers called microfibrils.
Describe why microfibrils in cellulose are importnat.
Microfibrils are the hydrogen bonds that link the sections of straight beta glucose chains together to form strong fibers. These fibers mean cellulose provides structural support for cells.
Where is cellulose found in?
Plant cell walls
What is cellulose’s function?
To provide structural support for cells such as in plant cell walls.
Maltose is a sugar. Describe how a molecule of maltose is formed.
A molecule of maltose, a disaccharide, is formed by a condensation reaction between two molecules of alpha glucose which are held together by a glycosidic bond.
Chitin is a structural polysaccharide, similar to cellulose in plants, that is found in the exoskeletons of insects and crustaceans, as well as in the cell walls of the fungi. It is made up of chains of the monosaccharide N-acetylglucosamine, which is derived from glucose.
The polysaccharide chains are long, unbranched and linked together by weak hydrogen bonds.
Explain why chitin can be described as a polysaccharide.
Chitin is described as a polysaccharide as it is made up of more than 3 molecules of monosaccharides joined together, as shown by the fact that it is made up of multiple chains of monosaccharides which are joined together.
Chitin is a structural polysaccharide, similar to cellulose in plants, that is found in the exoskeletons of insects and crustaceans, as well as in the cell walls of the fungi. It is made up of chains of the monosaccharide N-acetylglucosamine, which is derived from glucose.
The polysaccharide chains are long, unbranched and linked together by weak hydrogen bonds.
Chitin is similar to cellulose in plants.
Describe the ways in which cellulose and chitin are similar.
Both polysaccharides have long and unbranched chains which are linked together by weak hydrogen bonds, known as microfibrils.
Chitin is a structural polysaccharide, similar to cellulose in plants, that is found in the exoskeletons of insects and crustaceans, as well as in the cell walls of the fungi. It is made up of chains of the monosaccharide N-acetylglucosamine, which is derived from glucose.
The polysaccharide chains are long, unbranched and linked together by weak hydrogen bonds.
Chitin can be broken down by enzymes called chitinases, which catalyze hydrolysis reactions.
Explain how these hydrolysis reactions break down chitin.
A molecule of water is used to break, or ‘hydrolyze’, the glycosidic bond which is present between the molecules of N-acetylglucosamine in chitin.
Chitin is a structural polysaccharide, similar to cellulose in plants, that is found in the exoskeletons of insects and crustaceans, as well as in the cell walls of the fungi. It is made up of chains of the monosaccharide N-acetylglucosamine, which is derived from glucose.
The polysaccharide chains are long, unbranched and linked together by weak hydrogen bonds.
Some organisms are able to make their own chitinases.
Explain how it would be beneficial for plants to make and secrete chitinases as a defense system.
Firstly, the secretion of chitinases from organisms such as plants will cause it to have a defense mechanism against insects that digest them as their exoskeleton is made out of chitin thus it can potentially break down.
As well as this, the secretion of chitinases protect organisms from fungal infection as chitinase can break down the cell walls of fungi.
Outline the structure of a Triglyceride.
Triglycerides have one molecule of glycerol with three fatty acids attached to it.
Draw the structure of a fatty acid.
The double bond between oxygen and carbon is required.
https://media.discordapp.net/attachments/352951793187029005/825801699938795550/unknown.png
What is a hydrocarbon?
Hydrocarbons are compounds of carbon and hydrogen.
