1A | Biological Molecules Flashcards
1
Q
What is a Polymer?
A
Polymers are large, complex molecules made from a high (3 or more) number of monomers joined together.
2
Q
Give 2 examples of monomers.
A
Monosaccharides (Glucose, Galactose, etc.) Nucleotides Amino Acids Fatty Acids Glycerol
3
Q
Give at least 2 elements that all carbohydrates have in common.
A
O (Oxygen)
C (Carbon)
H (Hydrogen)
4
Q
Carbohydrates are made from monomers.
Give the more specific name for these monomers.
A
Monosaccharides
5
Q
Glucose is a Hexose sugar.
Given this information, how many carbon atoms does it have?
A
6
6
Q
List the 2 isomers of Glucose.
A
Alpha Glucose
Beta Glucose
7
Q
Draw the structure of Alpha glucose.
A
https://static.aqa.org.uk/assets/image/0018/235440/00055366-DA00046397-DB.png
8
Q
Draw the structure of Beta glucose.
A
https://static.aqa.org.uk/assets/image/0008/235439/00055366-DA00046396-DB.png
9
Q
Describe the difference between Beta and Alpha Glucose.
A
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
10
Q
What is a condensation reaction?
A
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.
11
Q
What reaction joins monosaccharides together?
A
Condensation
12
Q
What is a glycosidic bond?
A
A glycosidic bond is the chemical bond formed between two monosaccharides when they are joined together by a condensation reaction.
13
Q
What is a disaccharide?
A
A disaccharide is formed when two monosaccharides are joined together.
14
Q
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.
A
https://media.discordapp.net/attachments/352951793187029005/825440516098228224/unknown.png
15
Q
Draw two alpha glucose molecules joined together.
What type of ‘sugar’ is this?
Name the molecule created.
Draw a box over the glycosidic bond.
A
https://media.discordapp.net/attachments/352951793187029005/825440866969452594/unknown.png
+H2O must be included.
16
Q
What monomers are made from Maltose?
A
Two molecules of alpha glucose.
17
Q
What monomers are made from Sucrose?
A
One glucose molecule and one fructose molecule.
18
Q
What monomers make up Lactose?
A
One glucose molecule and one galactose molecule.
19
Q
List 3 disaccharides.
A
Lactose
Sucrose
Maltose
20
Q
What is a Hydrolysis reaction?
A
A hydrolysis reaction is a reaction wherein the chemical bond between monomers are broken, with the use of a water molecule.
21
Q
Here is a molecule of Maltose:
https://media.discordapp.net/attachments/352951793187029005/825440866969452594/unknown.png
Hydrolyze the molecule.
A
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.
22
Q
Which is a reducing sugar and which is a non-reducing sugar?
Maltose Sucrose Fructose Lactose Galactose Glucose
A
Reducing Non-reducing Reducing Reducing Reducing Reducing
23
Q
Are all monosaccharides reducing sugars?
If not, list one that isn’t.
A
Yes
All are reducing.
24
Q
Are all disaccharides reducing sugars?
If not, list one that isn’t.
A
No
Sucrose
25
What test can be used to check for the presence of sugars?
The Benedict's Test
26
What solution in the Benedict's Test is specifically used to check for sugars?
Benedict's Reagent
27
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.
28
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.
29
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.
30
An investigator carries out the non-reducing sugars test and finds the sample stays blue.
What does this imply?
The sample contains no sugar.
31
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.
32
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).
33
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.
34
```
Blue
Brick Red
Yellow
Orange
Green
```
From least concentrated to most concentrated reducing sugar, list these in order.
```
Blue
Green
Yellow
Orange
Brick Red
```
35
What is a Polysaccharide?
A polysaccharide is formed when more than two monosaccharides are joined together by condensation reactions.
36
What is Starch's role in plants?
Starch is the main energy storage material in plants, thus it is used to store energy.
37
What is starch a mixture of?
Starch is a mixture of two polysaccharides of alpha glucose - amylose and amylopectin.
38
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.
39
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.
40
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.
41
Give the solution that is used for testing starch.
Iodine (dissolved) in potassium iodide.
42
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.
43
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.
44
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.
45
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.
46
An animal has excess glucose.
What does this get turned into?
Glycogen for storage.
47
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.
48
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.
49
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.
50
Where is cellulose found in?
Plant cell walls
51
What is cellulose's function?
To provide structural support for cells such as in plant cell walls.
52
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.
53
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.
54
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.
55
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.
56
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.
57
Outline the structure of a Triglyceride.
Triglycerides have one molecule of glycerol with three fatty acids attached to it.
58
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
59
What is a hydrocarbon?
Hydrocarbons are compounds of carbon and hydrogen.
60
Are fatty acids hydrocarbons?
Yes
61
Draw the structure of a Triglyceride.
https://media.discordapp.net/attachments/581202442524295179/826887915510169621/unknown.png
62
What does it mean to be hydrophobic?
Being hydrophobic means you repel water molecules.
63
In a Triglyceride, what part of it is hydrophobic?
The fatty acid tails
64
List one feature of Triglycerides.
They are insoluble in water.
65
Here is a Glycerol:
Through condensation reactions, turn this Glycerol into a Triglyceride.
https://media.discordapp.net/attachments/352951793187029005/825808858663616562/unknown.png
Here's the structure of a fatty acid:
https://media.discordapp.net/attachments/352951793187029005/825801699938795550/unknown.png
Thus it must look like this:
https://media.discordapp.net/attachments/773366869276753952/825809515344560178/unknown.png
+3H2O must be included.
66
Here's a Triglyceride:
https://media.discordapp.net/attachments/581202442524295179/826887915510169621/unknown.png
Circle all ester bonds.
https://media.discordapp.net/attachments/352951793187029005/825809997963067452/unknown.png
67
A fatty acid binds to a glycerol molecule.
What bond is formed?
An ester bond
68
What is a saturated fatty acid?
Saturated fatty acids don't have any double bonds between their carbon atoms.
69
What is an unsaturated fatty acid?
Unsaturated fatty acids have at least one double bond between carbon atoms, which cause the chain to kink.
70
Name this molecule:
https://media.discordapp.net/attachments/352951793187029005/825810598234423326/unknown.png
Saturated or Unsaturated?
Fatty acid
Saturated
71
https://media.discordapp.net/attachments/352951793187029005/825811232715571220/unknown.png
What molecule is this?
Phospholipid
72
Name all molecules:
https://media.discordapp.net/attachments/352951793187029005/825811527465828402/unknown.png
```
Blue = Phosphate
Orange = Fatty Acid
Green = Glycerol
```
73
Describe the structure of a phospolipid.
Phospholipids are molecules which have two fatty acids attached to a glycerol by ester bonds.
The glycerol also has a phosphate group attached, which is hydrophilic - it attracts water. The fatty acids are hydrophobic.
They are used as the main polymer in cell membranes.
74
What are triglyceride molecules mainly used for?
Energy storage molecules
75
Why are Triglycerides good for energy storage?
The long hydrocarbon tails of the fatty acids contain lots of chemical energy - a lot of energy is released when they are broken down. Because of this, triglycerides have about twice the amount of energy stored compared to carbohydrates.
They're insoluble, so they do not affect the water potential of the cell and so water does not enter the cells by osmosis which could make them swell.
76
Why do triglycerides form as droplets in response to water?
Triglycerides clump together in insoluble droplets in cells because the fatty acids tails are hydrophobic and the tails face inwards, shielding themselves from water with their glycerol heads.
77
Phospholipids make up a bilayer in cell membranes.
Describe what phospholipids are designed to do in the cell membrane.
2 Phospholipids form a bilayer, thus their phosphate groups, which are hydrophilic, are found outside the glycerol. Fatty acid tails, which are hydrophobic, are found inside the bilayer, as they are hydrophobic, protecting them from water by the glycerol heads.
As a result of this, the center of the bilayer is hydrophobic, so water soluble substances can't easily pass through it - the membrane acts as a barrier to these substances.
78
Describe the Emulsion Test for Lipids.
Firstly, you must have a test tube which has ethanol in it. Add your sample to the test tube with the ethanol.
Shake the test tube for about a minute so that it dissolves, the pour the solution into water.
Any lipid will show up as a milky emulsion - this shows why lipids are insoluble.
The more lipid there is, the more noticeable the milky color will be.
79
Describe the difference between a saturated fatty acid and an unsaturated fatty acid.
Unsaturated fatty acids have at least one double bond between two carbon elements thus making it 'kink'.
Saturated fatty acids, on the other hand, have no double bond between two carbon elements.
80
Name the 3 monomers of carbohydrates.
What is the scientific name for this?
Glucose
Galactose
Fructose
Monosaccharide
81
Name 3 disaccharides.
Include what each one is made from.
Maltose (Glucose + Glucose both Alpha)
Sucrose (Glucose + Fructose)
Lactose (Glucose + Galactose)
82
Name the 2 monomers of lipids.
Fatty Acids
| Glycerol
83
Name 3 polysaccharides.
Cellulose
Glycogen
Starch (Amylose and Amylopectin)
84
Name 2 lipid polymers.
Phospholipid
| Triglyceride
85
Name the monomer for proteins.
Amino Acid
86
What is a dipeptide?
A dipeptide refers to a molecule that has 2 amino acids joined together.
87
What is a polypeptide?
A polypeptide refers to a molecule that has more than 2 amino acids joined together.
88
What are proteins made of?
The answer is not 'Amino Acids'
One or more polypeptides
89
All living things share how many amino acids between them?
20
90
There are 20 possible different amino acids.
What makes each one different to eachother?
The R group is variable between each amino acid, thus each amino acid's difference to each other occurs in their R group.
91
Draw the structure of an amino acid.
https://media.discordapp.net/attachments/581202442524295179/826192592412082216/unknown.png
92
Here's the structure of an Amino Acid:
https://media.discordapp.net/attachments/581202442524295179/826192592412082216/unknown.png
Point out the 3 groups and their names.
https://media.discordapp.net/attachments/352951793187029005/826190822021005342/unknown.png
93
List all 3 groups in an Amino Acid.
Variable group
Carboxyl group
Amino group
94
List 2 elements found in an amino acid.
Nitrogen, Hydrogen, Oxygen and Carbon
95
Here are 2 amino acids:
https://media.discordapp.net/attachments/581202442524295179/826195410564415508/unknown.png
Form these amino acids together by a condensation reaction.
Describe what this forms.
Circle the bond formed as well as it's name.
https://media.discordapp.net/attachments/581202442524295179/826195627640750150/unknown.png
Dipeptide
Must include +H2O
96
The bonds between amino acids are called what?
Peptide bonds
97
Proteins have four structural levels.
Name all 4.
Primary
Secondary
Tertiary
Quaternary
98
Describe the Primary structure of a protein.
The primary structure refers to the sequence of amino acids in the polypeptide chain.
99
Describe the Secondary structure of a protein.
In a secondary structure, as more amino acids are added, the polypeptide chain does not remain fat and straight, as hydrogen bonds form between the amino acids in the chain.
This makes it automatically coil into an alpha helix or fold into a beta sheet.
100
Describe the Tertiary structure of a protein.
The tertiary structure of a protein often occurs when the coiled/folded chain of amino acids are coiled/folded even further.
More bonds form between different parts of the polypeptide chain:
- More hydrogen bonds
- Ionic bonds
- Disulfide bridges
For proteins made from a single polypeptide chain, the tertiary structure forms their final 3D structure.
101
Describe the Quaternary structure of a protein.
The Quaternary structure of a polypeptide is made up of several different polypeptide chains held together by bonds.
For proteins made from more than one polypeptide chain (e.g. Collagen/Haemoglobin), the quaternary structure is the protein's final 3D structure.
102
List 3 functions of proteins.
```
Enzymes
Hormones
Channel Proteins
Antibodies
Structural Proteins
```
103
Describe and explain at least 3 functions of proteins, as well as why they are needed.
Firstly, Proteins can be synthesized into Enzymes, which have catalyze reactions - they are biological catalysts.
They have a variety of functions and are needed to speed up chemical reactions and thus are necessary for the life of most if not all organisms. Some are used to hydrolyze large molecules into smaller ones, like Amylase, while other ones are used to help to synthesize (make) larger molecules.
Proteins can also be used as antibodies, which are involved in the immune response.
Without antibodies, phagocytes would become extremely ineffective due to how antibodies work to compliment them - the process called agglutimation, possible due to their 2 binding sites, means that many pathogens get clumped together at once, meaning getting rid of pathogens become much faster and efficient as phagocytes won't be digesting phagocytes one at a time. As a result of this, many organisms require the use of antibodies to survive from infection.
Proteins can be used as channel proteins.
They are present in cell membranes and, together with lipids, control what enter and leave the cell. Channel proteins allow ions and water molecules to transport across membranes which are sometimes needed for certain processes which will be necessary for an organism's survival.
As well as this, proteins exist in the form of hormones which travel through the bloodstream. They are needed to stimulate cells to do certain cells, triggered by glycoproteins and glycolipids which signal a presence of hormones.
They are necessary for certain processes, such as the release of glycogen to ration blood sugar in the body and the fight or flight response.
They also exist as structural proteins, i.e. Collagen is found in connective tissue.
104
Describe the Biuret test for proteins.
Firstly, get your container like a test tube and put your test solution in it.
Your test solution must be alkaline so you must add a few drops of sodium hydroxide solution to it.
Add some copper (II) sulfate solution to the solution. If there's no protein, the solution will stay blue. If there is protein, the solution will be purple.
105
What groups do all amino acids have in common?
Amino and Carboxyl group
106
Leucyl-alanine is a dipeptide.
Describe how a dipeptide is formed.
A dipeptide is formed by a condensation reaction between the amino group of one amino acid and the carboxyl group of another.
A water molecule (H2O) is formed in the process.
107
Myoglobin is a protein formed from a single polypeptide chain.
Describe the tertiary structure of a protein like myoglobin.
Firstly, a polypeptide's secondary structure folds and coils further to form a tertiary structure, forming ionic bonds, hydrogen bonds and disulfide bridges along the polypeptide chain.
108
What is an Enzyme?
Enzymes are tertiary proteins that speed up chemical reactions - they are biological catalysts.
109
List 3 features of an Enzyme.
Enzymes have an active site, which is a specific shape used to bind onto certain substrates.
Enzymes are proteins in their tertiary structure.
Enzymes catalyze metabolic reactions - both at a cellular level (e.g. respiration) and for the organism as a whole (e.g. digestion).
Enzymes have a second active site called an allosteric site.
110
What's activation energy?
Activation energy refers to the minimum amount of energy required to start a chemical reaction.
111
What do enzymes do to activation energy?
Enzymes lower the activation energy required when used in metabolic reactions thus they increase the rate of a reaction.
112
When a substrate fits into the enzyme's active site, what does it form?
An enzyme-substrate complex
113
Give 2 reasons why the formation of an enzyme-substrate complex decreases activation energy and speeds up chemical reactions.
If two substrate molecules need to be joined, being attached to the enzyme holds them close together, reducing and repulsion between the molecules so they can bond more easily.
If the enzyme is catalyzing a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate, so the substrate molecule breaks up more easily.
114
Here's a diagram showing two different curves:
https://media.discordapp.net/attachments/581202442524295179/826514380786761728/unknown.png?width=849&height=563
- One curve features the usage of an enzyme - which color curve is this?
- Describe where on the graph the chemical reaction begins.
- On both curves, label the activation energy.
https://media.discordapp.net/attachments/581202442524295179/826515572778860594/unknown.png?width=1105&height=564
- Red is enzyme, black is no enzyme
- Distance between the starting energy to the peak is activation for both, thus red is lower than black's
- Chemical reaction happens at peak.
115
Describe the Lock And Key model.
Early scientists studying the action of enzymes came up with the 'lock and key' model - this is where the substrate fits into the enzyme in the same way that a key fits into a lock.
Firstly, a complementary substrate must enter the active site of an enzyme. After doing this, the substrate becomes attached close to the enzyme, forming the enzyme-substrate complex.
Furthermore, the enzyme will then catalyze the needed substrate into the products required. The active site of the enzyme in the lock and key model is seen to not change at all.
116
Describe the flaw in the lock and key model.
The lock and key model is a theoretical model developed that scientists, wherein part of it stated that after the enzyme-substrate complex is formed, the active site of the enzyme does not change.
This was eventually seen as false. This is because it was seen that the enzyme's active site during the enzyme-substrate complex changes slightly to complete the fit, something the lock and key model did not account for.
This caused the creation of the induced fit model as a more modern example.
117
Describe the induced fit model.
Similar to the lock and key model, a substrate firstly enters the active site of an enzyme with a complementary shape.
As the substrate binds to the active site, the active site changes slightly - if it does not change shape in a complementary manner, it may lose it's attraction with the substrate, but assuming that it does not in this case, the enzyme-substrate complex is established and the enzyme will catalyze the reaction to form products.
118
Referring to the induced fit model in your answer, describe why enzymes are so specific.
Enzymes are so specific due to the fact that in order for them to bind with a substrate, their active site must be complementary for an attraction to form, as stated for an induced fit model.
However, enzymes are even more specific as when the substrate enters the active site, the active site of the enzymes changes shape slightly, which can mean if it changes shape in a way that makes it less complementary to the substrate, it may lose the ability to establish an enzyme-substrate complex.
Therefore, enzymes are so specific for not only their active site, but also due to the fact that they must also change shape in the correct way too or else they won't be able to catalyze reactions with their complementary substrate.
119
How is the enzyme's active site determined?
By it's tertiary structure (which is determined by the primary structure).
120
What is an enzyme-substrate complex?
An enzyme-substrate complex refers to the state wherein a substrate is bonded with the active site of an enzyme.
121
Temperature has an influence on enzyme activity.
Draw a diagram showing the influence temperature has on enzyme activity assuming that the optimum temperature is at a human level (37 C).
Label the optimum temperature on the diagram.
https://media.discordapp.net/attachments/581202442524295179/826521332476543067/unknown.png?width=735&height=563
(37 C is optimum here).
122
This image shows an enzyme's activity at different temperatures, with optimum temperature 37 C:
https://media.discordapp.net/attachments/581202442524295179/826521654795829288/unknown.png?width=788&height=564
Describe A, B and C.
For A, the enzyme activity is extremely low as the rate of reaction is very low, however, the enzyme is not denatured as that does not occur in low temperatures, only high ones - the low rate of reaction is due to the low kinetic energy as a result of low temperature, thus enzymes are slower and won't establish enzyme-substrate complexes as fast to catalyze chemical reactions and so rate of reaction is very low.
At B, the enzyme is operating at the optimum temperature (37 C) as this is the highest temperature the enzyme can be at before it is denatured - the higher kinetic energy, paired with the fact the enzyme is not denatured means that it has a higher chance to collide and establish enzyme-substrate complexes, therefore catalyzing reactions and speeding up enzyme activity and the rate of reaction.
At C, the enzyme is denatured, and so the active site of the enzyme changes, which is why there is a steep drop - the change in the active site of the enzyme will basically make it impossible for it to bind to the substrate it was supposed to bind with and thus it cannot catalyze reactions, lowering the rate of reaction.
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pH has an influence on enzyme activity.
Draw a diagram showing the influence pH has on enzyme activity assuming that the optimum temperature is at pH 7.
Label the optimum pH (roughly) on the diagram.
Draw an arrow to when the enzyme is denaturing/denatured.
https://media.discordapp.net/attachments/581202442524295179/826528233259663370/unknown.png
Different to temperature, both sides must be symmetrical - they give the same effect, thus try to make both curves symmetrical. This may be hard though
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This image shows an enzyme's activity at different pH levels, with optimum pH 7:
https://media.discordapp.net/attachments/581202442524295179/826529191519715348/unknown.png
Describe A, B and C.
Firstly at A, the pH is under 7. As a result of this, the environment the enzyme is working in is acidic and thus it will start to denature after a certain level of pH has passed.
The curve drops steeply at a certain point, and this shows the enzyme's active site denaturing and changing shape - it is not much harder, if not impossible to establish enzyme-substrate complexes and thus reactions cannot be catalyzed. This decreases the rate of reaction dramatically, becoming worse as you keep going down.
Similarly to A, the environment at C shows the same curve, however this time it is highly Alkaline - an alkaline environment also denatures the enzyme and changes the enzyme, giving the same conditions and lowering rate of reaction.
At B, the enzyme is at it's optimal pH and thus it is able to establish enzyme-substrate complexes easiest at that point, increasing rate of reaction as it can catalyze reactions quickly as it's active site is not denatured and will be able to fit into substrates.
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Describe and explain why enzymes denature at a pH outside of their optimum.
The H and OH ions found in acids and alkalis can mess up the ionic bonds and hydrogen bonds that hold the enzyme's tertiary structure in place.
This makes the active site change shape, so the enzyme is denatured.
126
Enzyme concentration has an influence on the rate of reaction.
Draw a diagram showing the influence enzyme concentration has on the rate of reaction.
Assume that the substrate concentration is limited.
Since the substrate concentration is limited, label the change related to this on the diagram and why it occurs.
https://media.discordapp.net/attachments/581202442524295179/826531644827107388/unknown.png?width=897&height=564
The reason the curve starts to level off when substrate concentration is limited is due to the fact that when there are too many enzymes, eventually they will saturate the environment and make the abundance of substrate more scarce, and as a result each addition of enzyme after a point begins to not have as much of an effect on the rate
of reaction, as they find it harder to find a substrate each time to bind to.
After more additions of enzymes, it eventually levels off, meaning that each addition of enzyme does not affect the rate of reaction as now there may be no substrates available for the additional enzymes to occupy.
127
Enzyme concentration has an influence on the rate of reaction.
Draw a diagram showing the influence enzyme concentration has on the rate of reaction.
Assume that the substrate concentration is unlimited.
https://media.discordapp.net/attachments/581202442524295179/826531987921043456/unknown.png?width=717&height=564
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This diagram shows the effect enzyme concentration has on the rate of reaction:
https://media.discordapp.net/attachments/581202442524295179/826532323939057664/unknown.png?width=668&height=564
Describe A and B.
Firstly, at A, the curve is increasing at a constant rate due to the fact that there are more substrate then there is enzymes, and as a result the increase in enzymes will always increase the rate of reaction as more substrates are occupied in an active site at one time - they are not oversaturated.
At B, we can assume that the substrate amount is limited. Even though there are still less enzymes then there are substrate, as the curve still increases at part of B, it starts to become more difficult for enzymes to find substrates to bind onto by their active site as less substrate is available at once as they are occupied by other enzymes, thus enzymes start to compete and there is a lesser chance each additional enzyme will collide with a substrate, so the rate of reaction increases at a diminishing rate until the curve levels out, meaning that enzymes are now oversaturated - additional enzymes have no further effect.
129
This diagram shows the effect enzyme concentration has on the rate of reaction:
https://media.discordapp.net/attachments/581202442524295179/826533908819738695/unknown.png?width=675&height=564
Describe what is shown.
In this curve, there is a surplus of substrate at all levels of enzyme concentration, thus it is seen to be unlimited.
The curve is upwards sloping, as the increase in enzymes are positively correlated with a higher rate of reaction, wherein the addition of each enzyme increases the rate of reaction by the same amount because the curve is constant.
The curve is constant due to the fact that there is a surplus of substrates for all levels of enzyme concentration and so adding enzymes only further increases the rate of reaction as there are more substrates that can be occupied into active sites at one time (so much substrate in fact that enzymes don't have to compete). Reactions are then catalyzed, therefore the reaction rate increases.
130
This diagram shows the effect substrate concentration has on the rate of reaction:
https://media.discordapp.net/attachments/581202442524295179/826535397122768906/unknown.png?width=641&height=564
Describe what is shown.
At A, the substrate concentration increasing is positively correlated to the rate of reaction due to the existence of enzymes - more substrates being added at this point means that more enzymes can form enzyme-substrate complexes easier (as there's a higher chance they'll collide with one) thus catalyzing reactions, increasing the rate of reaction overall.
At B, a saturation point is reached - at this point, there are so many substrate molecules that the enzymes have about as much as they can cope with (all the active sites are full), and adding more makes no difference as the curve levels off - the rest do not influence the rate of reaction.
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What are enzyme inhibitors?
Molecules that bind to the enzyme that they inhibit - inhibition can be competitive or non-competitive.
132
List 2 types of enzyme inhibitors.
Competitive
| Non-Competitive
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What is a competitive inhibitor?
Competitive inhibitors are molecules that have a very similar shape to that of the substrate molecules.
They compete with the substrate molecules to bind to the active site, but no reaction takes place.
Instead, they block the active site, so no actual substrate molecules can fit in it.
134
Draw a diagram showing the effect substrate concentration has on the rate of reaction.
Draw 2 curves, one with a competitive inhibitor and one with no inhibitor.
https://media.discordapp.net/attachments/581202442524295179/826537329569038367/unknown.png?width=916&height=563
135
This diagram shows the effect substrate concentration has on the rate of reaction with a competitive inhibitor and with no enzyme inhibitor:
Describe what is shown.
Firstly, when comparing no inhibitor with the competitive inhibitor, we can see that the rate of reaction is higher at almost all levels of substrate concentration in the curve with no inhibitor compared to the curve with the competitive inhibitor.
This is due to the fact that a competitive inhibitor is an enzyme inhibitor that features a similar shape to the other complementary substrate, however if it attaches itself to the active site of the complementary enzyme, a reaction does not occur. Because it is now occupied with the active site of an enzyme, real substrates can't join to it meaning that the rate of reaction decreases.
Since both the competitive inhibitor and real substrate are competing for the active site of the enzyme, the increase in substrate concentration increases the rate of reaction due to the fact it is more likely for substrates to win active sites over competitive inhibitors (as there begins to be more of them) which causes reactions to take place, increasing the rate of reaction.
At a certain point, it reaches the same reaction speed as would with no inhibitor, as there are now so many substrates that the competitive inhibitor can no longer legitimately compete, as the real substrate will win over the active site of the enzyme almost all the time.
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What is an allosteric site?
The allosteric site is a site that allows molecules to either activate or inhibit enzyme activity. It's different than the active site on an enzyme, where substrates bind.
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What is a non-competitive inhibitor?
A non-competitive inhibitor is a molecule that binds to the enzyme's allosteric site - an area located on the enzyme wherein molecules that bind to it can inhibit enzyme activity.
When the non-competitive inhibitor binds to the enzyme's allosteric site, the active site of the enzyme changes shape, so the substrate molecules can no longer bind to it.
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Why is a non-competitive inhibitor non-competitive?
The allosteric site is different to the active site, which is where the substrate binds, and therefore the non-competitive inhibitor does not have to compete with the substrate to bind to the enzyme as they both bind to different parts of the enzyme, not the same one, so they don't compete with each other (thus non competitive).
139
Describe why increasing substrate concentration in an environment with enzymes that are affected by non-competitive inhibitors will make little to no difference.
The reason for this is due to the fact that non-competitive inhibitors do not bind to the active site, thus they do not need to compete with the substrate.
What happens is that the substrates are still able to access the active site, but the active site of the enzyme is changed due to the fact that the non-competitive inhibitors bind to the allosteric site which change the shape of the active site, meaning that no substrates can bind to the active site as it is not complementary anymore, decreasing the rate of reaction as enzymes are not able to catalyze the reaction.
Therefore, it doesn't matter how high you make substrate concentration, it will not be able to establish an enzyme-substrate complex as the active site is now the incorrect shape.
140
The diagram shows the affect substrate concentration has on rate of reaction in an environment of complementary enzymes.
https://media.discordapp.net/attachments/581202442524295179/826554235281211442/unknown.png?width=627&height=563
Which color shows:
A non-competitive inhibitor?
No enzyme inhibitor?
Outline what is seen on the red curve.
Red shows a non-competitive inhibitor due to the fact that the change in rate of reaction as the result of the increase in substrate concentration is little to none.
Black shows no enzyme inhibitor.
141
What is a monomer?
A monomer is a smaller molecule from which larger molecules, known as polymers, are made from.
142
Following digestion and absorption of food, the undigested remains are processed to box
form faeces in the parts of the intestine below the ileum.
The faeces of people with constipation are dry and hard. Constipation can be treated
by drinking lactulose. Lactulose is soluble, but is not digested or absorbed in the
human intestine.
Use your knowledge of water potential to suggest why lactulose can be used to help people suffering from constipation.
Lactulose lowers the water potential of the faeces, so water retained enters the faeces due to osmosis, making it softer and so faeces can be passed easier.
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```
Lactulose can also be used to treat people who have too high a concentration of
hydrogen ions (H+) in their blood.
```
The normal range for blood H+ concentration is 3.55 × 10^−8 to 4.47 × 10^−8 mol dm−3.
A patient was found to have a blood H+ concentration of 2.82 × 10^−7 mol dm−3
Calculate the minimum percentage decrease required to bring the patient’s blood H+ concentration into the normal range
Firstly 4.47 x 10^-8 is closest to 2.82 x 10^-7
Change 4.47 x 10^-8 so 10 is by a factor of -7
= 0.447 x 10^-7
0.447 / 2.82 = 0.1585
to find % decrease minus result by 1
1 - 0.1585 = 0.8415
(-)84.15%
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Draw and label a nucleotide.
https://media.discordapp.net/attachments/352951793187029005/830543032427347988/unknown.png
Named bases are allowed.
145
Replication of mitochondrial DNA (mtDNA) is different from that of nuclear DNA.
The replication of the second strand of mtDNA only starts after two-thirds of the first strand of mtDNA has been copied.
A piece of mtDNA is 16 500 base pairs long and is replicated at a rate of 50 nucleotides per second.
How long will it take to replicate this strand of mtDNA?
a piece of mtdna is 16500 base pairs long with 2 strands
33000 nucleotides
so both are 16500 nucleotides long
16500 / 50 = 330 for the first strand during this time, the third of the second has been done too however 2/3 have not
so 16500 x 0.66666 = 11000
11000 / 50 = 220
330 + 220 = 550 seconds
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This image shows the structure of a fat substitute over triglycerides:
https://media.discordapp.net/attachments/352951793187029005/838084313601802280/unknown.png
This fat substitute cannot be digested in the gut by lipase.
Suggest why.
It is a fat substitute, and because it's structure is different to that of a triglyceride, it has a different shape.
As a result of this, ES complexes cannot be formed between the lipase and the fat substitute as it does not fit in the active site, meaning it can't be digested.
147
This fat substitute is a lipid:
https://media.discordapp.net/attachments/352951793187029005/838084313601802280/unknown.png
Despite being a lipid, it cannot cross the cell-surface membranes of cells lining the gut.
Suggest one reason why it cannot cross cell-surface membranes.
It's too large
It's polar
It's hydrophilic
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The linked image is a photograph (micrograph) of a mitochondrion taken using a scanning electron microscope.
https://media.discordapp.net/attachments/352951793187029005/838086130627903498/unknown.png
What is a feature of the image that proves that it was taken by a scanning electron microscope?
It's a 3D image.
TEM's can't be 3D.
149
What is a Micelle?
Micelles are lipid molecules that arrange themselves in a spherical form in aqueous solutions.
The formation of a micelle is a response to the amphipathic nature of fatty acids,
