Proteins And Enzymes Flashcards
(157 cards)
1
Q
What are the monomers from which proteins are made?
A
Amino acids
Amino acids are the building blocks of proteins and consist of an amine group, a carboxyl group, and a side chain.
2
Q
What is the general structure of an amino acid?
A
H,N - COOH
NH2 represents the amine group, COOH represents the carboxyl group, and R represents the side chain.
3
Q
What type of bond is formed by the condensation of two amino acids?
A
Peptide bond
This bond links amino acids together to form peptides and proteins.
4
Q
What are dipeptides and polypeptides?
A
Dipeptides are formed by two amino acids; polypeptides are formed by many amino acids
Polypeptides can consist of hundreds of amino acids.
5
Q
What types of bonds contribute to the structure of proteins?
A
Hydrogen bonds, ionic bonds, disulfide bridges
These interactions stabilize protein structures and contribute to their function.
6
Q
What is the relationship between protein structure and function?
A
Primary, secondary, tertiary, and quaternary structures affect protein function
Each level of structure is crucial for the protein’s specific role.
7
Q
What is the Buret test used for?
A
To test for proteins
This test detects peptide bonds in proteins.
8
Q
What is the role of enzymes in biochemical reactions?
A
Enzymes lower the activation energy of reactions
This makes reactions proceed faster and more efficiently.
9
Q
What model describes enzyme action?
A
Induced-fit model
This model illustrates how enzymes change shape to fit substrates.
10
Q
What determines the specificity of enzymes?
A
The tertiary structure of the enzyme’s active site
This structure allows enzymes to interact with specific substrates.
11
Q
List factors that affect the rate of enzyme-controlled reactions.
A
- Enzyme concentration
- Substrate concentration
- Competitive inhibitors
- Non-competitive inhibitors
- pH
- Temperature
Each factor can influence enzyme activity and reaction rates.
12
Q
True or False: Enzymes only catalyze reactions within cells.
A
False
Enzymes can catalyze both intracellular and extracellular reactions.
13
Q
What elements are commonly found in proteins?
A
- Nitrogen (N)
- Carbon (C)
- Hydrogen (H)
- Oxygen (O)
- Sulfur (S)
Some proteins may also contain sulfur.
14
Q
What is the function of hemoglobin?
A
Allows oxygen to bind and be transported around the organism
Hemoglobin is crucial for oxygen transport in the blood.
15
Q
What is the role of antibodies?
A
Bind to specific antigens and are used in the immune response
Antibodies help protect the organism from pathogens.
16
Q
What is the function of actin and myosin?
A
Structural proteins involved in muscle contraction
These proteins work together to facilitate movement.
17
Q
What are essential amino acids?
A
Amino acids that must be obtained from the diet
The body cannot synthesize essential amino acids.
18
Q
Fill in the blank: Proteins are made of monomers called _______.
A
Amino acids
Amino acids link together to form proteins.
19
Q
What is cell fractionation used for?
A
To isolate chloroplasts from leaf tissue
Cell fractionation involves breaking open cells and separating their components based on size and density.
20
Q
Why is an isotonic solution used during cell fractionation?
A
To prevent osmotic lysis of cells
Isotonic solutions have the same solute concentration as the inside of the cells, preventing water movement that could cause cell damage.
21
Q
Why is the solution kept ice-cold during the isolation of mitochondria?
A
To reduce enzyme activity and prevent degradation of organelles
Cold temperatures slow down metabolic reactions, preserving the integrity of the isolated organelles.
22
Q
What is the purpose of using a buffered solution in cell fractionation?
A
To maintain a stable pH
A buffered solution helps to prevent changes in pH that could denature proteins and affect organelle functionality.
23
Q
What are the main components of an amino acid?
A
Amino group, carboxylic acid group, hydrogen atom, variable side chain
The variable side chain (R group) determines the unique characteristics of each amino acid.
24
Q
What type of reaction occurs when two amino acids form a dipeptide?
A
Condensation reaction
A condensation reaction involves the removal of a water molecule and the formation of a peptide bond.
25
How many peptide bonds are present in a polypeptide chain?
One less than the total number of amino acids
## Footnote
For example, a dipeptide formed from two amino acids has one peptide bond.
26
What is the N-terminal end of a peptide chain?
The end with the amine group
## Footnote
The N-terminal is the start of the polypeptide chain where the amino group is located.
27
What is the C-terminal end of a peptide chain?
The end with the carboxyl group
## Footnote
The C-terminal is the end of the polypeptide chain where the carboxylic acid group is located.
28
Fill in the blank: A dipeptide is formed from _______ amino acids.
2
29
True or False: A polypeptide is a polymer made of amino acid monomers.
True
## Footnote
Polypeptides consist of long chains of amino acids linked by peptide bonds.
30
What happens during hydrolysis of a peptide bond?
Water is added, breaking the peptide bond
## Footnote
Hydrolysis involves the addition of water to split the peptide bond, releasing individual amino acids.
31
Complete the table: Number of peptide bonds in a dipeptide.
1
32
Complete the table: Number of water molecules produced when two amino acids form a dipeptide.
1
33
What is a single point mutation?
A change to a single nucleotide in DNA sequence
## Footnote
Single point mutations can lead to changes in protein structure and function.
34
What is the significance of the variable side chain (R group) in amino acids?
Determines the properties and identity of the amino acid
## Footnote
The R group can be hydrophilic, hydrophobic, positively or negatively charged, affecting protein structure and function.
35
What are the four levels of protein structure?
Primary Structure, Secondary Structure, Tertiary Structure, Quaternary Structure
## Footnote
The primary structure refers to the sequence of amino acids, while secondary, tertiary, and quaternary structures involve various folding and interactions.
36
What defines the primary structure of a protein?
The number and sequence of amino acids in a polypeptide chain
## Footnote
The unique sequence of amino acids determines the protein's characteristics and function.
37
What is the secondary structure of a protein, also known as 2°?
The way the polypeptide chain folds into alpha helices and/or beta pleated sheets
## Footnote
These structures are stabilized by hydrogen bonds between the backbone atoms.
38
What types of structures can be found in the secondary structure of proteins?
* Alpha helix
* Beta pleated sheet
## Footnote
These are common patterns found in the folding of polypeptide chains.
39
What is the tertiary structure of a protein, also known as 3°?
The overall three-dimensional shape of a polypeptide
## Footnote
This structure is formed by interactions between the side chains of the amino acids.
40
What is the quaternary structure of a protein, also known as 4°?
The arrangement of multiple polypeptide chains into a single functional unit
## Footnote
Not all proteins have quaternary structure; it is found in those that consist of more than one polypeptide chain.
41
True or False: The primary structure of proteins is the most complex level of organization.
False
## Footnote
The primary structure is the simplest level; complexity increases with secondary, tertiary, and quaternary structures.
42
What does secondary structure refer to in protein structure?
The way the polypeptide chain folds or coils into alpha helixes and/or beta pleated sheets
## Footnote
Secondary structure is a key level of protein structure that describes the local folded structures that form within a polypeptide due to hydrogen bonding.
43
What are the two types of secondary structures in proteins?
* Alpha helixes
* Beta pleated sheets
## Footnote
These structures are stabilized by hydrogen bonds between the backbone atoms in the polypeptide chain.
44
How is the secondary structure of proteins held together?
By weak hydrogen bonds
## Footnote
These hydrogen bonds form between the backbone of the polypeptide chain, specifically between the carbonyl oxygen of one amino acid and the amide hydrogen of another.
45
True or False: The secondary structure of proteins is primarily stabilized by covalent bonds.
False
## Footnote
The secondary structure is primarily stabilized by weak hydrogen bonds, not covalent bonds.
46
Fill in the blank: The alpha helix and beta pleated sheet are types of _______.
[secondary structures]
## Footnote
These structures are crucial for the overall shape and function of proteins.
47
What types of interactions are involved in forming an alpha helix?
Hydrogen bonds between every fourth amino acid
## Footnote
This specific bonding arrangement creates the helical structure characteristic of alpha helices.
48
In a beta pleated sheet, how are the strands arranged?
Strands are aligned next to each other, connected by hydrogen bonds
## Footnote
Beta sheets can be parallel or antiparallel based on the direction of the polypeptide strands.
49
What is tertiary structure in proteins?
The further folding of the polypeptide chain into a specific complex 3D shape
## Footnote
The R groups on the amino acids determine the specific shape and are held together by bonds between R groups.
50
What determines the specific tertiary structure of a protein?
The sequence of amino acids in the primary structure
## Footnote
This sequence dictates where the bonds form, influencing the 3D shape.
51
What types of bonds maintain the tertiary structure of proteins?
* Weak hydrogen bonds
* Ionic bonds
* Disulphide bridges
## Footnote
Weak hydrogen bonds form between C=O and NH of adjacent amino acids, ionic bonds form between oppositely charged R groups, and disulphide bridges are strong covalent bonds between cysteine amino acids.
52
What is the role of the specific shape of a protein?
Determines how it interacts with other molecules, such as active sites in enzymes or binding sites of receptor proteins
## Footnote
The shape is crucial for the protein's specific function.
53
What happens to proteins during denaturation?
Proteins lose their specific shape due to the breaking of weak hydrogen bonds
## Footnote
Denaturation can occur with increasing temperature, affecting the protein's function.
54
True or False: All proteins have a specific tertiary structure.
True
## Footnote
This specific structure is necessary for each protein to carry out its function.
55
What is quaternary structure in proteins?
The structure formed by the assembly of multiple polypeptide chains
## Footnote
Hemoglobin is an example of a protein with quaternary structure.
56
Fill in the blank: The strong covalent bonds that form between cysteine amino acids in proteins are called _______.
Disulphide bridges
## Footnote
These bonds are crucial for maintaining the protein's tertiary structure.
57
What types of amino acids contribute to the formation of hydrogen bonds in tertiary structure?
Amino acids with hydrophilic side chains
## Footnote
These side chains interact with polar environments, facilitating bond formation.
58
What are the two types of amino acids based on their side chain properties?
* Hydrophobic side chains
* Hydrophilic side chains
## Footnote
These properties influence the folding and stability of the protein structure.
59
What type of protein structure is characterized by a globular shape?
Tertiary structure
## Footnote
This shape is essential for the protein's function.
60
What is the quaternary structure of proteins?
Proteins consisting of two or more polypeptide chains joined together
## Footnote
An example includes hemoglobin, which has four polypeptide chains.
61
How many polypeptide chains does hemoglobin have?
Four polypeptide chains
## Footnote
Hemoglobin is classified as a globular, functional protein.
62
How many polypeptide chains does collagen have?
Three polypeptide chains
## Footnote
Collagen is classified as a fibrous, structural protein.
63
What are the two main types of proteins based on their structure?
* Globular proteins
* Fibrous proteins
64
What is denaturation in proteins?
A permanent change to the specific 3D tertiary structure of a protein
## Footnote
This occurs when bonds break due to high temperatures or pH changes.
65
At what temperatures do proteins typically denature?
High temperatures
## Footnote
Proteins do not denature at low temperatures.
66
What effect does increasing temperature have on protein molecules?
Increases kinetic energy, causing molecules to vibrate more
## Footnote
This can break weak hydrogen bonds in the secondary and tertiary structures.
67
What type of bonds are broken when the pH of the environment changes?
Ionic bonds between the R groups in the tertiary structure
## Footnote
This contributes to the loss of the specific tertiary shape of the protein.
68
What is the primary role of the specific shape of a protein?
Essential to its function
## Footnote
The shape determines how the protein interacts with other molecules.
69
Fill in the blank: In a fibrous protein, many pieces of the string are twisted together into a _______.
rope
70
Fill in the blank: In a globular protein, the pieces of string are usually fewer and are rolled into a _______.
ball
71
What is the basic structure of proteins?
Polymers of amino acids joined by peptide bonds formed by condensation
## Footnote
Proteins are macromolecules composed of long chains of amino acids that fold into specific shapes to perform various functions.
72
What is the primary structure of a protein?
Order and sequence of amino acids
## Footnote
The primary structure determines the protein's overall shape and function.
73
What characterizes the secondary structure of proteins?
Folding of polypeptide chain due to weak hydrogen bonding forming α-helices and β-pleated sheets
## Footnote
The secondary structure is stabilized by hydrogen bonds between backbone atoms.
74
What is the tertiary structure of a protein?
3-D folding due to hydrogen bonding and ionic/di-sulfide bonds
## Footnote
The tertiary structure is critical for the protein's functionality and interactions.
75
What defines the quaternary structure of a protein?
Two or more polypeptide chains joined together
## Footnote
Quaternary structure is observed in proteins like hemoglobin, which consists of multiple subunits.
76
Why are antibodies effective only against specific pathogens?
Antigens on pathogens have a specific shape; antibodies bind complementary to these antigens
## Footnote
The specificity is due to the unique variable regions on antibodies that match the shape of the antigen.
77
Fill in the blank: The _______ test is used to detect proteins.
Biuret
## Footnote
The Biuret test involves adding a reagent to a protein solution that changes color in the presence of peptide bonds.
78
True or False: The tertiary structure of a protein is only determined by peptide bonds.
False
## Footnote
The tertiary structure is influenced by various interactions, including hydrogen bonds, ionic bonds, and disulfide bridges.
79
What occurs during the Biuret test?
Add equal volume of Biuret reagent to protein solution; color change indicates presence of proteins
## Footnote
The color change from blue to purple indicates the presence of peptide bonds in proteins.
80
What is biology the study of?
Proteins and shapes fitting together
81
What does the Biuret test detect?
Peptide bonds
82
What is the procedure for the Biuret test?
Place a small volume of solution in a test tube and add an equal volume of Biuret solution
83
What color change indicates the presence of protein in the Biuret test?
Blue to purple/violet
84
What color indicates no protein is present in the Biuret test?
Stays blue
85
True or False: Enzymes are proteins and give a positive Biuret result.
True
86
What would you add to both solutions to distinguish lactase from lactose?
Add Biuret reagent
87
What color will lactase produce in the Biuret test?
Purple
88
Why does lactase give a purple color in the Biuret test?
Because lactase is a protein
89
What color will lactose produce in the Biuret test?
Will remain blue
90
What is the difference between lactase and lactose in the context of the Biuret test?
Lactase is a protein (purple), lactose is a reducing sugar (blue)
91
What are enzymes?
Lobular proteins that act as biological catalysts
## Footnote
Enzymes are soluble in water and participate in chemical reactions without being consumed.
92
What is the role of enzymes in chemical reactions?
They increase the rate of reaction by lowering the activation energy needed
## Footnote
Enzymes do not get used up in the reaction.
93
What is activation energy (Ea)?
The minimum energy required for a successful chemical reaction
## Footnote
Activation energy is essential for bond breaking and formation.
94
What happens to the bonds in the substrate during enzyme action?
Bonds are stressed, distorted, or weakened
## Footnote
This process facilitates the reaction at lower temperatures.
95
What is formed during enzyme action?
An enzyme-substrate complex
## Footnote
This complex is crucial for the catalytic activity of enzymes.
96
What type of molecules do enzymes help break down during digestion?
Large complex molecules (polymers) into small simple molecules (monomers)
## Footnote
This process occurs through hydrolysis.
97
At what temperature do enzymes typically function in the human body?
37°C
## Footnote
This is the average body temperature where enzymatic reactions occur efficiently.
98
Fill in the blank: Enzymes allow reactions that would normally require higher temperatures to work at a _______.
Lower temperature
99
True or False: Enzymes are consumed during the chemical reactions they catalyze.
False
## Footnote
Enzymes remain unchanged and can catalyze multiple reactions.
100
What does the arrow in a chemical equation indicate in biology?
An enzyme-controlled reaction
## Footnote
This signifies the direction of the reaction and the role of enzymes.
101
What is the relationship between reactants and products in an enzyme-catalyzed reaction?
Reactants are converted into products
## Footnote
This conversion involves breaking and reforming chemical bonds.
102
What is cell fractionation?
A technique used to separate cellular components based on their size and density.
## Footnote
Commonly used in biochemistry to study different parts of cells.
103
What is the role of enzymes in biological processes?
Enzymes are proteins that catalyze biochemical reactions by lowering the activation energy.
## Footnote
They are essential for various metabolic processes.
104
What is an active site?
The region on an enzyme where substrate molecules bind and undergo a chemical reaction.
## Footnote
It is specifically complementary in shape to its substrate.
105
What forms when a substrate binds to an enzyme's active site?
Enzyme-Substrate complex.
## Footnote
This complex is crucial for the catalysis of the reaction.
106
What is the significance of the active site in enzyme function?
It distorts and stresses the substrate's bonds, allowing them to break and reform configurations, thus lowering activation energy.
## Footnote
This process is essential for the speed of biochemical reactions.
107
Fill in the blank: Enzymes have a specific _______ structure.
[tertiary]
## Footnote
The specific structure is crucial for the function of the enzyme.
108
What does the 'lock and key' model of enzyme action describe?
The model states that the active site of the enzyme (the 'lock') is specifically shaped to fit the substrate (the 'key').
## Footnote
This model illustrates the specificity of enzyme-substrate interactions.
109
True or False: Only enzymes have active sites.
True.
## Footnote
While all proteins have binding sites, only enzymes have active sites.
110
What is the typical composition of active sites?
Made up of more than 10 amino acids.
## Footnote
The arrangement and properties of these amino acids are critical for enzyme activity.
111
What is the induced fit model of enzyme action?
The model suggests that the active site of the enzyme undergoes a slight change in shape to better fit the substrate upon interaction.
## Footnote
This model emphasizes flexibility in the enzyme structure.
112
How does the lock and key model differ from the induced fit model?
In the lock and key model, the active site is rigid and does not change shape, whereas in the induced fit model, the active site changes shape to bind the substrate.
## Footnote
The lock and key model suggests a perfect fit before binding, while the induced fit model allows for adaptation.
113
Why does one enzyme catalyze only one reaction?
An enzyme has a specific shaped active site that only fits one particular substrate.
## Footnote
This specificity is due to the unique structure of the enzyme.
114
Why can a protein be the substrate for two different enzymes?
Different parts of the protein have different amino acid sequences, resulting in varying shapes that fit different enzyme active sites.
## Footnote
Each enzyme's active site is complementary to specific parts of the protein.
115
Fill in the blank: In the induced fit model, the active site of the enzyme _______ to accommodate the substrate.
changes shape
## Footnote
This change allows for better interaction with the substrate.
116
True or False: The active site in the lock and key model is flexible and changes shape to fit the substrate.
False
## Footnote
The lock and key model depicts a fixed shape that does not change.
117
List two characteristics of the active site in the induced fit model.
* The active site is not fixed
* The active site wraps around the substrate
## Footnote
This allows for a more dynamic interaction between the enzyme and substrate.
118
What is formed when the substrate enters the enzyme's active site?
Enzyme/substrate complex
## Footnote
This complex is crucial for the biochemical reaction to occur.
119
What happens to the active site when the substrate binds to it?
The shape of the active site changes
## Footnote
This change is necessary for the reaction to proceed.
120
What does the change in shape of the active site affect?
It applies stress on the bonds within the substrate molecules
## Footnote
This stress lowers the activation energy required for the reaction.
121
What is the term for the energy required to initiate a chemical reaction?
Activation energy
## Footnote
Lowering this energy is a key function of enzymes.
122
What complex is formed after the reaction occurs and before the product leaves?
Enzyme/products complex
## Footnote
This complex is temporary and precedes the release of the product.
123
What occurs after the products leave the active site of the enzyme?
The active site returns to its original shape
## Footnote
This allows the enzyme to catalyze another reaction.
124
Fill in the blank: The substrate enters the enzyme's active site and binds to it, forming the _______.
Enzyme/substrate complex
125
True or False: The binding of the substrate to the enzyme increases the activation energy of the reaction.
False
## Footnote
The binding actually lowers the activation energy.
126
What is formed when the substrate enters the enzyme's active site?
Enzyme/substrate complex
## Footnote
This complex is crucial for the biochemical reaction to occur.
127
What happens to the active site when the substrate binds to it?
The shape of the active site changes
## Footnote
This change is necessary for the reaction to proceed.
128
What does the change in shape of the active site affect?
It applies stress on the bonds within the substrate molecules
## Footnote
This stress lowers the activation energy required for the reaction.
129
What is the term for the energy required to initiate a chemical reaction?
Activation energy
## Footnote
Lowering this energy is a key function of enzymes.
130
What complex is formed after the reaction occurs and before the product leaves?
Enzyme/products complex
## Footnote
This complex is temporary and precedes the release of the product.
131
What occurs after the products leave the active site of the enzyme?
The active site returns to its original shape
## Footnote
This allows the enzyme to catalyze another reaction.
132
Fill in the blank: The substrate enters the enzyme's active site and binds to it, forming the _______.
Enzyme/substrate complex
133
True or False: The binding of the substrate to the enzyme increases the activation energy of the reaction.
False
## Footnote
The binding actually lowers the activation energy.
134
What is a mutation?
A change in the DNA sequence of a gene
## Footnote
Mutations can lead to variations in traits and can affect enzyme function.
135
What factors affect enzyme action?
Factors include:
* Enzyme concentration
* Substrate concentration
* Temperature
* pH
* Inhibitors
## Footnote
These factors can influence the rate of enzyme-catalyzed reactions.
136
How does enzyme concentration affect the rate of reaction?
Initially, as enzyme concentration increases, the rate of reaction increases.
## Footnote
This is because more enzyme-substrate complexes can form per second.
137
What happens when substrate concentration increases?
Initially, the rate of reaction increases, but eventually plateaus as enzymes become saturated
## Footnote
This occurs when all enzyme active sites are fully occupied.
138
What is the effect of temperature on enzyme activity?
As temperature increases, kinetic energy increases, leading to more successful collisions and enzyme-substrate complexes
## Footnote
However, past the optimum temperature, enzymes may denature.
139
What occurs to enzymes when the pH moves away from optimum?
The hydrogen bonds in the tertiary structure are altered, changing the shape of the active site
## Footnote
This can result in decreased enzyme activity or denaturation.
140
What is enzyme denaturation?
The process where the enzyme's active site changes shape, preventing substrate binding
## Footnote
This can occur due to extreme pH or temperature conditions.
141
What is a competitive inhibitor?
A substance that competes with the substrate for the active site of an enzyme
## Footnote
Increasing substrate concentration can overcome competitive inhibition.
142
What is a non-competitive inhibitor?
A substance that binds to an enzyme at a site other than the active site, reducing enzyme activity
## Footnote
The maximum rate of reaction will be lower in the presence of non-competitive inhibitors.
143
True or False: At high concentrations of competitive inhibitors, the maximum rate of reaction can eventually reach the same as without an inhibitor.
True
## Footnote
Sufficient substrate can outcompete the inhibitor.
144
Fill in the blank: The maximum number of enzyme-substrate complexes are formed at the _______.
[optimum temperature]
## Footnote
Beyond this point, enzyme activity decreases due to denaturation.
145
What happens to enzyme activity at temperatures above the optimum?
Weak hydrogen bonds break, altering the tertiary structure of the enzyme
## Footnote
This results in the active site becoming non-complementary to the substrate.
146
How does enzyme concentration influence the formation of enzyme-substrate complexes?
Higher enzyme concentration increases the number of complexes formed per second until saturation
## Footnote
After saturation, further increases do not affect the rate of reaction.
147
What is the relationship between substrate concentration and the rate of reaction with a set amount of enzymes?
The rate of reaction increases with substrate concentration until all active sites are occupied
## Footnote
At this point, the enzyme concentration becomes the limiting factor.
148
What happens to the rate of reaction as all active sites in an enzyme become saturated?
It plateaus as the rate does not change
## Footnote
This plateau indicates that the enzyme is limiting the rate of reaction.
149
What is a mutation?
Any change to the DNA sequence
## Footnote
Mutations can affect the coding sequence of a gene.
150
What is a gene mutation?
A change in a single base in the DNA sequence
## Footnote
This is also known as a point mutation.
151
How can the initial rate of a reaction be determined from a graph?
By drawing a tangent that touches the curve at zero
## Footnote
This provides the slope at the start of the reaction.
152
What does the term 'E-S complexes' refer to?
Enzyme-substrate complexes
## Footnote
These complexes form when an enzyme binds to its substrate.
153
What is the significance of drawing a tangent on a curve at a specific point?
It allows for the calculation of the rate of reaction at that point
## Footnote
The slope of the tangent represents the rate.
154
What is the formula to find the rate between two points on a graph?
dy/dx
## Footnote
This represents the change in the product over the change in time.
155
What does a tangent that touches the curve at a specific point indicate?
The instantaneous rate of reaction at that point
## Footnote
This is key for analyzing reaction kinetics.
156
Fill in the blank: A mutation that changes a single base in the DNA sequence is known as a _______.
point mutation
157
True or False: The rate of reaction increases indefinitely as more substrate is added.
False
## Footnote
The rate eventually plateaus due to enzyme saturation.
