Chapter 1 Biological Molecules Flashcards
1
Q
What is a monomer?
A
A single molecule that makes up larger molecules called polymers.
2
Q
What is a polymer?
A
A large molecule made up of multiple smaller molecules called monomers
3
Q
Name examples of monomers
A
Monosaccharide; amino acids, nucleotides.
4
Q
What reaction joins monomers together?
A
A condensation reaction.
5
Q
What happens in a condensation reaction?
A
Two monomers are chemically bonded together, water is formed as a by-product.
6
Q
What reaction takes place when biological molecules are separated?
A
A hydrolysis reaction.
7
Q
What happens in a hydrolysis reaction?
A
Two monomers are separated by breaking a chemical bond. Water is used up in this reaction
8
Q
What are larger complex carbohydrates made from?
A
Monosaccharides
9
Q
What are the common monosaccharides?
A
Glucose, galactose and fructose
10
Q
What reaction forms the bond between two monosaccharides?
A
A condensation reaction.
11
Q
What bond forms when monosaccharides join?
A
A glycosidic bond.
12
Q
What is a disaccharide?
A
A molecule made from 2 monosaccharides
13
Q
How is a disaccharide formed?
A
A condensation reaction between 2 monosaccharides
14
Q
What is maltose and what is it formed from?
A
A disaccharide formed from the condensation reaction between 2 glucose molecules.
15
Q
What is sucrose and what is it formed from?
A
A disaccharide formed from the condensation reaction between a glucose and a fructose molecule.
16
Q
What is lactose and what is it formed from?
A
A disaccharide formed from the condensation reaction between glucose and a galactose molecule.
17
Q
What is an isomer?
A
A variation of a particular molecule. The formula stays the same, but the structure is slightly different.
18
Q
What are the isomers of glucose?
A
Alpha (α) and beta (β) glucose.
19
Q
What is the difference between alpha and beta glucose?
A
The OH group on carbon 1 of α-glucose is below the ring, on β-glucose it is above. ABBA - Alpha Below Beta Above.
20
Q
What is a polysaccharide?
A
A complex carbohydrate formed from the condensation reactions of many monosaccharides.
21
Q
What is glycogen and what is it made of?
A
A complex carbohydrate, a polysaccharide made from multiple α-glucose molecules.
22
Q
What is starch and what is it formed from?
A
A complex carbohydrate, a polysaccharide made from multiple α-glucose molecules.
23
Q
What is cellulose?
A
A complex carbohydrate, a polysaccharide made from multiple β-glucose molecules.
24
Q
What is the purpose of glycogen?
A
It is an insoluble store of energy in animals.
25
What is the purpose of starch?
It is an insoluble store of energy in plants, and an energy source for animals
26
What is the purpose of cellulose?
It is an insoluble structural molecule for plants, especially for their cell walls.
27
What is the structure of glycogen?
Heavily branched polymer of α-glucose molecules. Linked at 1-4 glycosidic bonds. Branched with 1-6 glycosidic bonds.
28
Give 3 ways glycogen's structure is related to its function.
1. It is insoluble so it does not diffuse out of cells.
2. It is compact so lots can be stored in a small space.
3. It is highly branched so can be acted on simultaneously by enzymes.
29
What is the structure of starch?
Lightly branched polymer of α-glucose molecules. Linked at 1-4 glycosidic bonds. Branched with 1-6 glycosidic bonds.
30
Give 5 ways that the structure of starch is related to its function.
1. It is insoluble so doesn't affect water potential and osmosis
2. It is large so doesn’t diffuse out of cell
3. It is compact so lots stored in small space
4. It is hydrolysed to form a-glucose so it is easily transported and used for respiration
5. It is branched so more enzymes can act simultaneously.
31
What is the basic structure of cellulose?
Straight lengths of polymers made of β-glucose molecules. Bonded with 1,4 glycosidic bonds.
32
How are the monosaccharides in cellulose arranged?
Alternative β-glucose molecules are turned upside down
33
Give 3 ways that the structure of cellulose is related to its function.
1. It is made up of B-glucose so it forms long, straight unbranched chains.
2. The chains run parallel to each other and are crossed linked by hydrogen bonds which add collective strength.
3. Molecules are grouped to form microfibrils which are also grouped to form fibres which provide more strength.
34
Based on the arrangement of cellulose molecules, explain why cell walls provide strength and support to plant cells.
Cellulose molecules form hydrogen bonds with each other to make microfibrils. Microfibrils join to make macrofibrils. Macrofibrils join to make fibres. Fibres are insoluble and tough.
35
Give 4 examples of reducing sugars.
All monosaccharides - glucose, galactose, fructose. Also some disaccharides - e.g. lactose
36
What is an example of a non-reducing sugar?
Sucrose
37
What is Benedict's reagent used to test for?
Reducing sugars
38
What is the test for reducing sugars
Add equal volumes of the sample and Benedict's reagent, then gently heat for 5 minutes and if reducing sugar present then colour from blue through to orange
39
What is the test for non-reducing sugars
If the reducing sugar test presents no colour change, add more of your sample to an equal volume of HCl, then slowly add sodium hydrogen carbonate and re-test with Benedict's reagent whilst gently heating for 5 minutes and if sugar is present then colour will turn to orange
40
Explain how a positive result is formed in Benedict's test.
Reducing sugar reacts with blue Cu2+ --> to make brick-red Cu+
41
How can we test for starch?
Iodine solution turns from orange to blue/black if starch is present.
42
How can we use a colorimeter to do a quantitative Benedict's test?
Use a colorimeter to measure the absorbance or transmission of light by a coloured solution.
The more concentrated solution is the more light is absorbed (less light transmitted).
Compare this to a data table or calibration curve (known concentrations vs. abs/trans value)
43
What is the role of lipids?
A source of: energy/waterproofing/insulation/protection
44
What are the 2 main groups of lipids?
Triglycerides and phospholipids
45
What are the components of a triglyceride?
1 glycerol molecule and 3 fatty acids bonded with a condensation reaction.
46
Give 4 ways that the structure of triglycerides are related to their properties.
1. High ratio of energy storing C-H bonds so an excellent energy store.
2. Low mass to energy ratio so good storage molecules
3. Large and non-polar so insoluble in water meaning they will not affect osmosis in cells.
4. There is a high ratio of H to O atoms so they will release water when oxidised to provide a source of water.
47
What reaction occurs to form a triglyceride?
A condensation reaction.
48
What bond is formed when a fatty acid joins to glycerol?
An ester bond.
49
What is an R-group?
A long chain of carbon atoms with attached hydrogen atoms.
50
How can the R-group of a lipid vary?
It could be saturated or unsaturated.
51
What is the difference between saturated and unsaturated R-groups?
Saturated R groups have single bonds between carbons, and 2 hydrogens joined to each carbon. Unsaturated R groups have double bonds between carbon atoms, this limits the number of hydrogen atoms bonded.
52
How many water molecule(s) is/are needed when breaking down a triglyceride?
3
53
What is another term for the condensation reaction that makes lipids?
Esterification
54
Why do oils contain unsaturated triglycerides rather than saturated?
Unsaturated fatty acids cause the molecule to kink/bend. This means they cannot pack closely together (ie. They cannot form more H bonds)
55
What does monounsaturated and polyunsaturated mean?
Monounsaturated means that there is one carbon carbon double bond. Polyunsaturated means that there are many carbon-carbon double bonds.
56
What does having a double bond do to the fatty acid chain / R-group?
The double bond puts a kink into it, so that it isn't straight.
57
What does having unsaturated R-groups do to the fluidity of the triglycerides?
The kink caused by the double bond of unsaturation means the chains don't lie closely packed. They therefore can't make intermolecular hydrogen bonds and become solid.
58
What is the difference in structure between triglyceride and phospholipid?
Phospholipid: 2 fatty acid chains + 1 phosphate group
Triglyceride: 3 fatty acid chains
59
Describe the structure of a phospholipid.
Phospholipids have a hydrophobic tail which orients itself away from water but mixes readily with fat and a hydrophilic head which interacts with water.
60
What does hydrophobic mean?
Water fearing - will not dissolve, repels water.
61
What does hydrophilic mean?
Water loving - will dissolve in water.
62
How do triglycerides react to water?
They are hydrophobic - repel water.
63
How do phospholipids react to water?
They have a hydrophilic head and a hydrophobic tail. The head is attracted to water and the tail repels water.
64
What will a phospholipid do if placed in water?
It will sit on the water, head down and tails up, or form a sphere with heads in the water and tails inside being protected.
65
Describe the phospholipid bilayer arrangement.
Hydrophilic heads point outwards into water.
Hydrophobic tails point inwards (shielded from aqueous environment).
66
Why is a phospholipid hydrophilic and hydrophobic?
It has a hydrophilic phosphate head and a hydrophobic fatty acid tail.
67
Describe the steps in identifying lipids and state the positive result.
1. Mix sample with ethanol
2. Mix solution with water and shake
3. If a white emulsion layer is formed then a lipid is present.
68
What are the monomers of proteins?
Amino acids
69
List out the elements that make up proteins.
C, H, O, N, S
70
What are the components that make up an amino acid?
Central carbon + H atom + Amino group (-NH2) + Carboxyl group (-COOH) + R(side) group - this is the variable part which makes the amino acids different.
71
What is the basic structure of an amino acid?
72
What does NH2 represent in an amino acid?
The amine group
73
What does COOH in an amino acid represent?
Carboxyl group.
74
What does the "R" represent in an amino acid?
A side chain, mainly carbon and hydrogen, may also contain other groups.
75
What reaction causes two amino acids to bond together?
A condensation reaction.
76
What bond holds two amino acids together
Peptide
77
What is formed when two amino acids bond by condensation reaction?
A dipeptide.
78
What is formed when many amino acids bond by condensation reaction?
A polypeptide.
79
What is a functional protein?
A protein which has a particular role, it is not involved in structure.
80
True or false, a functional protein can be made of more than 1 polypeptide?
TRUE
81
What is the primary structure of a protein?
Amino acid sequence
82
What is the secondary structure of a protein?
alpha-helix + beta-pleated sheets
83
What is an alpha-helix?
A coiling of the polypeptide chain caused by hydrogen bonding between amino acids. This is in the constant region, it DOES NOT include the variable region.
84
What is the tertiary structure of a protein?
Folding into a 3D shape
85
What is the quaternary structure of a protein?
Multiple polypeptide chains with the additional prosthetic groups.
86
What bond is involved in the primary structure of a protein?
Peptide bond
87
What bond is involved in the secondary structure of a protein?
Hydrogen bond
88
State 3 bonds involved in the tertiary structure of a protein.
Ionic bonds, hydrogen bonds and disulphide bridges
89
Name the reaction that breaks down proteins.
Hydrolysis
90
What is the solution used to test for the presence of proteins?
Biuret solution.
91
Describe the test for proteins.
1. Add equal volumes of the sample and Biuret reagent.
2. Mix gently.
3. If protein is present then a colour change from blue to purple will be observed.
92
What are prosthetic groups?
Non-protein component in a protein, e.g. iron containing haem group in haemoglobin.
93
What is thin layer chromatography?
A technique to separate individual components of a mixture (eg. Amino acids).
94
Based on what principles are the amino acids separated in TLC?
Their solubility
95
Why should the chromatography plate be only handled by the edges?
To avoid contamination from proteins on your hands.
96
What are the two main types of proteins?
Globular, fibrous
97
What is the main role of fibrous proteins?
Structural.
98
What makes fibrous proteins stable?
Main parallel chains bonded with cross bridges.
99
What is the main role of globular proteins?
Metabolic reactions. Enzymes are globular.
100
What are metabolic reactions?
The sum of all reactions in the organism.
101
What are anabolic reactions?
Building up larger molecules.
102
What are catabolic reactions?
Breaking down molecules. This is a breakdancing cat.
103
What are enzymes?
Biological catalysts that speed up chemical reactions.
104
Name the energy that is required to start a reaction.
Activation energy.
105
How does an enzyme catalyse a reaction?
By lowering the activation energy.
106
Describe the lock and key model of enzyme action.
The shape of the active site is rigid. Only exactly complementary substrates can bind to form enzyme-substrate complexes.
107
What is the induced fit model?
The theory that the active site of an enzyme changes shape as the substrate binds to it. This is so that it can fit exactly to form an enzyme-substrate complex.
108
Name the structure where the enzyme and substrate are bound together.
Enzyme-substrate complex
109
Name the area on the enzyme that binds to and reacts with the substrate.
Active site
110
The active site has a _____ shape to the substrate.
Complementary/Specific
111
What creates the active site?
The tertiary structure
112
What does enzyme specificity mean?
Enzymes only work with one substrate. They are specific to that molecule.
113
What about the enzyme makes it specific?
Its active site. It will only allow one substrate to fit.
114
When an enzyme combines with a substrate what does it form?
An enzyme-substrate complex.
115
What happens to the substrate when an enzyme substrate complex is formed?
It is converted into products.
116
Give 4 factors that affect the rate of enzyme controlled reactions.
Temperature, pH, enzyme concentration and substrate concentration.
117
How does enzyme concentration affect the rate of a reaction?
The higher the enzyme concentration, the higher the rate of reaction. This is because there are more active sites available for the reaction to take place.
118
How does substrate concentration affect the rate of a reaction?
The higher the substrate concentration, the higher the rate of reaction. This is because more of the active sites are filled, and so the reaction occurs at a faster rate.
119
Will the rate of reaction continue to increase as the substrate concentration is increased? Why?
No. This is because the active sites will eventually all be filled all of the time, the reaction can't occur any faster under these conditions.
120
How does a competitive inhibitor affect the working of an enzyme?
They have a similar shape to the substrate, so compete for the active site. Bind to it, and stop the substrate binding.
121
How do the concentrations of substrate and competitive inhibitor affect the rate of reactions?
The greater the concentration of substrate, the less effective the competitive inhibitor is.
The greater the concentration of a competitive inhibitor, the slower the reaction.
122
Would a competitive inhibitor stop the reaction completely? Why?
No. Because the competitive inhibitor is not permanently bonded to the enzyme. When it leaves another molecule could fill its space. Eventually all substrate molecules will occupy an active site.
123
How does a noncompetitive inhibitor affect the working of an enzyme?
A noncompetitive inhibitor binds to an area of the enzyme which is not the active site. It alters the shape of the protein and so the substrate can't fit in the active site anymore.
124
How does increasing the substrate concentration affect the effect of the non-competitive inhibitor?
As they aren't competing, the non-competitive inhibitor's effect is not altered.
