190 Questions
What is the basic structure of an amino acid?
Amino group, carboxyl group, and R group attached to a central carbon atom
What is the function of amino acids in the body?
Building blocks of proteins and catalysts for chemical reactions
What are proteins primarily responsible for in the cell?
Catalysing chemical reactions and providing structural elements
What is unique to each amino acid?
The organic R group (or side chain)
Which functional groups are present in every amino acid molecule?
Amino group (−NH2) and carboxyl group (−COOH)
What type of bond does the α-carbon atom of an amino acid typically form with the R group?
Covalent bond
What is the primary function of proteins in the cell?
Catalyze chemical reactions
What is the significance of the α-carbon atom in an amino acid?
It is the central carbon to which both an amino and a carboxyl group are attached
Which of the following is a function of proteins in the cell?
Catalysing chemical reactions
What is the role of antibodies in the form of proteins?
Protecting animals from disease
Which statement about proteins is accurate?
They help bind cells together into tissues
What is the function of interferon, a form of protein?
Mounting an intracellular attack against viruses
What is a key role of proteins in gene expression?
Controlling the activity of genes
What is the primary function of interferon, a form of protein?
Mount an intracellular attack against viruses
Which statement about the role of proteins in gene expression is accurate?
Proteins control the activity of genes
What is a key role of proteins in binding cells together into tissues?
Providing structural elements
What do proteins primarily protect animals from, when in the form of antibodies?
Disease
What is the main function of proteins in enabling movement?
Acting as contractile elements
How many different combinations of proteins are possible with 20 amino acids when considering a dipeptide made of just two amino acids joined together?
$20^2 = 400$
What is the formula to calculate the number of different combinations possible with 20 amino acids for a protein with n amino acids in the chain?
$20^n$
What type of reaction links together amino acids to form proteins?
Condensation reaction
What gives each protein a characteristic and unique sequence of amino acids?
Linking together amino acids
What is the formula to calculate the number of different combinations possible with 20 amino acids for a protein with $n$ amino acids in the chain?
$20^n$
If a protein has a chain of 4 amino acids, how many different combinations are possible with 20 amino acids?
$20^4 = 160,000$
What does a dipeptide made of just two amino acids joined together yield in terms of different combinations?
$400$
If a protein has a chain of 6 amino acids, how many different combinations are possible with 20 amino acids?
$20^6 = 64,000,000$
What is the significance of the unique sequence of amino acids in a protein?
It dictates the 3-D conformation the folded protein will have
Which level of protein structure is primarily responsible for giving identity and characteristics to a protein?
Primary structure
What determines the shape of a protein?
Local interactions between parts of the polypeptide backbone
What allows amino acids to interact with each other that are not close in primary structure?
Tertiary structure
What is the primary distinction between the terms 'polypeptide' and 'protein'?
Polypeptide may or may not have folded into its final, functional form, while protein generally refers to a folded, functional molecule.
When is the term 'protein' generally used?
To refer to a folded, functional molecule that may have one or more subunits.
What does the term 'polypeptide' specifically refer to?
A single polymer of amino acids that may or may not have folded into its final, functional form.
What is the primary distinction between the terms 'polypeptide' and 'protein'?
Protein generally refers to a functional, folded molecule, while polypeptide may or may not have folded into its final, functional form
What allows amino acids to interact with each other that are not close in primary structure?
Disulfide bonds between cysteine R groups
What determines the shape of a protein?
The sequence of amino acids in its primary structure
What allows proteins to be amazing catalysts and adapt to, respond to, and pass on signals upon binding of other molecules or proteins?
Flexibility in structure
What happens if the structure of a protein is altered?
The function is usually lost, but not always
What characteristic defines proteins in terms of structure?
Infinite flexibility
What allows proteins to be amazing catalysts and adapt to, respond to, and pass on signals upon binding of other molecules or proteins?
Infinite flexibility
What happens if the structure of a protein is altered?
It loses all function
What is the primary distinction between the terms 'polypeptide' and 'protein'?
'Polypeptide' refers to a single amino acid chain while 'protein' can have multiple chains
What is the end of the protein that contains the only free α-carboxyl group called?
Carboxyl terminus
Where does the synthesis of proteins occur?
Ribosomes
How does the synthesis of proteins proceed?
By joining the carboxyl terminus of the first amino acid to the amino terminus of the next one
What is the end of the protein that has the free α-amino group referred to as?
Amino terminus
Where does the synthesis of proteins occur?
Ribosomes
What is the primary function of the carboxyl terminus in a protein?
Containing the free α-carboxyl group
What is the primary reason for arranging R-groups in an alternating orientation on either side of the polypeptide chain?
To prevent steric hindrance between consecutive R-groups
What can occur when consecutive R-groups are oriented on the same side of a peptide backbone?
Steric hindrance
What is the significance of organizing R-groups in an alternating orientation on either side of the polypeptide chain?
Preventing steric hindrance between consecutive R-groups
Why is the organization of R-groups in a protein not random?
To prevent steric hindrance between consecutive R-groups on the same side of the peptide backbone
What is the primary consequence of consecutive R-groups being oriented on the same side of a peptide backbone?
Steric hindrance
In what manner are sequential R-groups arranged around a peptide bond?
In an alternating orientation on either side of the polypeptide chain
What is the primary determinant of the overall conformation of a protein?
Primary structure
What directly specifies the sequence of amino acids in proteins?
Codons in DNA
What is the result of mutation and selection over evolutionary time?
Primary structure of proteins
What are regions of DNA specifying proteins known as?
'Coding' regions
What is the ultimate determinant of the overall conformation of a protein?
Primary structure
What directly specifies the sequence of amino acids in proteins?
mRNA
What are regions of DNA specifying proteins known as?
Exons
What arrived at the current state of the primary structure of any protein?
Mutation and selection over evolutionary time
What is the primary determinant of the overall conformation of a protein?
Primary structure
What directly specifies the sequence of amino acids in proteins?
messenger RNA
What are regions of DNA specifying proteins known as?
Exons
What is the result of mutation and selection over evolutionary time?
Change in primary structure
What gives rise to the properties a protein has?
Sequence of amino acids
At the tertiary level of protein structure, what plays a role in folding?
Interactions among the polypeptide backbone and amino acid side groups
What brings amino acids close together that are not near each other in primary structure?
Secondary structure formation
What gives rise to folds that bring amino acids close together that are not near each other in primary structure?
Interactions among the R-groups of the amino acids
What is the primary role of the sequence of amino acids in determining a protein's properties?
It gives rise to all of the properties a protein has
Which level of protein structure involves individual components of secondary structure interacting with each other?
Tertiary structure
What stabilizes a globular protein?
Ionic interactions, hydrogen bonding, and hydrophobic forces
What treatments can cause a protein to unfold and lose its structure and function?
Heat, pH changes, detergents, and urea
What gives rise to distinct 3-D shapes in non-fibrous proteins?
Protein folding
Which of the following is a force that stabilizes a globular protein?
Van der Waals forces
What effect do treatments like heat, pH changes, detergents, and urea have on a globular protein?
Cause the protein to unfold
What gives rise to distinct 3-D shapes in non-fibrous proteins?
Folding of the proteins
Which force stabilizes protein structure as a result of interactions that favour the exclusion of water?
Van der Waals forces
What type of bonds are made when two sulfhydryl side-chains of cysteine are brought into close proximity?
Disulfide bonds
Which force arises as a result of ionization of R-groups in the amino acids comprising a protein?
Ionic interactions
What kind of forces can give rise to regular repeating structures, such as helices or pleats, in proteins?
Hydrogen bonds
What type of bond is made when two sulfhydryl side-chains of cysteine are brought into close proximity?
Disulfide bond
What type of interactions stabilize protein structure as a result of interactions that favor the exclusion of water?
Hydrophobic forces
What type of forces are generally weak in comparison to covalent bonds and are dynamic due to the fluctuating nature of the attraction?
Van der Waals forces
Which force between amino acids that are close to each other in primary structure can give rise to regular repeating structures, such as helices or pleats, in proteins?
Hydrogen bonds
Which force arises as a result of ionization of R-groups in the amino acids comprising a protein?
Ionic interactions
What is the term used to describe various weak interactions that are generally weak in comparison to covalent bonds?
Van der Waals forces
What type of bond can give great strength to the overall protein structure when two sulfhydryl side-chains of cysteine are brought into close proximity?
Disulfide bond
Which force stabilizes protein structure as a result of interactions favoring the exclusion of water?
Hydrophobic forces
What type of forces stabilize protein structure as a result of interactions that favor the exclusion of water?
Van der Waals forces
Which type of bond is made when two sulfhydryl side-chains of cysteine are brought into close proximity, covalently joining different protein regions and giving great strength to the overall structure?
Disulfide bonds
Which force arises as a result of ionization of R-groups in the amino acids comprising a protein?
Ionic interactions
What kind of forces can give rise to regular repeating structures, such as helices or pleats, in proteins?
Hydrogen bonds
Which type of interaction favors the exclusion of water and stabilizes protein structure?
Hydrogen bonds
What term is used to describe various weak interactions that are generally weak in comparison to covalent bonds?
Hydrogen bonds
What gives great strength to the overall protein structure when two sulfhydryl side-chains of cysteine are brought into close proximity?
Disulfide bonds
Which force is dynamic due to the fluctuating nature of the attraction and is generally weak in comparison to covalent bonds?
Van der Waals forces
What might be a consequence of protein misfolding?
Inactivation of the protein
Which diseases are associated with protein misfolding?
Mad Cow Disease, Alzheimers, and Parkinson’s Disease
Which tissue is often affected by misfolding diseases?
Brain tissue
What might be a consequence of protein misfolding?
Inactivation of the protein
Which diseases are associated with protein misfolding?
Mad Cow Disease, Alzheimers, and Parkinson’s Disease
Which tissue is often affected by misfolding diseases?
Brain tissue
What are the two classes of proteins used by cells to facilitate proper folding of proteins?
Chaperones and chaperonins
Why do cells expend energy to facilitate the proper folding of proteins?
To prevent diseases associated with misfolded proteins
What is the primary role of molecular chaperones in cells?
Facilitate the proper folding of proteins
What is a key characteristic of proteins with quaternary structure?
They arise as a result of interactions between multiple polypeptides
Which protein demonstrates quaternary structure?
Adult hemoglobin
How do myoglobin and hemoglobin differ in terms of subunit structure?
Myoglobin has a single subunit, while hemoglobin has multiple subunits
What gives rise to differences in the behavior towards oxygen between myoglobin and hemoglobin?
Hemoglobin's multiple subunits compared to myoglobin's single subunit
What is the primary difference between myoglobin and hemoglobin in terms of structure?
Myoglobin lacks quaternary structure, while hemoglobin has quaternary structure
What is a key characteristic of proteins with quaternary structure?
They are composed of multiple polypeptides
What gives rise to differences in the behavior towards oxygen between myoglobin and hemoglobin?
Quaternary structure
Which protein demonstrates quaternary structure?
Adult hemoglobin
What is the primary distinction between myoglobin and hemoglobin?
Subunit structure
What allows proteins to be amazing catalysts and adapt to, respond to, and pass on signals upon binding of other molecules or proteins?
Distinct 3-D shapes in non-fibrous proteins
Which amino acid is known for its unique ability to function in both acid and base catalysis near physiological pH values?
Histidine
Which group of amino acids are often found clustered on the surface of globular proteins in aqueous solutions due to their hydrophilic nature?
Group IV: Basic Amino Acids
Which amino acid is most often found in the active sites of protein enzymes?
Histidine
Which chemical property sets histidine apart from the other standard amino acids?
Ability to function in acid and base catalysis
Which type of amino acids are precursors of nitrogenous base components of nucleotides and nucleic acids?
'Nonstandard' Amino Acids
Which amino acid derivative acts as a neurotransmitter?
Serotonin (derived from tryptophan)
Which type of amino acids are often found clustered on the surface of globular proteins in aqueous solutions?
Basic Amino Acids
Which chemical reaction is particularly important due to its effect on protein structure?
Peptide bond reaction
What is the primary role of heme, a complex amino-acid derived cofactor?
Participating in oxygen transport and storage
What distinguishes nonstandard amino acids from standard amino acids?
They have unique side chains not found in standard amino acids.
Which group of amino acids is characterized as hydrophobic?
Glycine, alanine, valine, leucine
Which amino acids possess functional groups with electron pairs available for hydrogen bonding to water and other molecules?
Serine, cysteine, threonine
Which amino acids have a carboxylic acid on their side chains that gives them acidic properties?
Aspartic acid, glutamic acid
Which group of amino acids plays a central role in amino acid metabolism?
Glutamate, glutamine
Which type of amino acids will ionize in an aqueous solution at physiological pH?
Aspartic acid, glutamic acid
Which group of amino acids has R groups possessing a spectrum of functional groups?
Serine, cysteine
Which group of amino acids has either aliphatic or aromatic R groups?
Valine, leucine
Which group of amino acids is characterized by being hydrophobic ('water fearing')?
Valinie , leucinie
Which group of amino acids has side chains that will fold into a three-dimensional shape to bury hydrophobic side chains in the protein interior in aqueous solutions?
Valinie , leucinie
Which group of amino acids possess at least one atom (nitrogen,oxygen,sulfur) with electron pairs available for hydrogen bonding to water and other molecules?
Serine, cysteine, threonine
Which amino acid is known for its ability to function in both acid and base catalysis near physiological pH values?
Histidine
What is the most abundant excitatory neurotransmitter in the central nervous system?
Glutamate
Which group of amino acids are often found clustered on the surface of globular proteins in aqueous solutions?
Group IV: Basic Amino Acids
Which amino acid is most often found in the active sites of protein enzymes?
Histidine
Which amino acid is a precursor of serotonin and melatonin, and synthesized from histidine?
Tryptophan
Which type of amino acids refers to those that have been chemically modified after incorporation into a protein?
Nonstandard Amino Acids
Which group of amino acids possess at least one atom with electron pairs available for hydrogen bonding to water and other molecules?
Group II: Polar Amino Acids
What is the primary role of the sequence of amino acids in determining a protein's properties?
Determining all properties
What are some precursors of a variety of complex nitrogen-containing molecules?
Amino acids
What type of forces can give rise to regular repeating structures, such as helices or pleats, in proteins?
Hydrogen bonds
Which group of amino acids has side chains that are hydrophobic ('water fearing')?
Group I: Nonpolar amino acids
Which group of amino acids possess at least one atom (nitrogen, oxygen, sulfur) with electron pairs available for hydrogen bonding to water and other molecules?
Group II: Polar, Uncharged Amino Acids
Which two amino acids have carboxylic acid on their side chains, giving them acidic (proton-donating) properties?
Aspartic acid and glutamic acid
Which group of amino acids will ionize in an aqueous solution at physiological pH, giving an overall charge of −1?
Group III: Acidic amino acids
What type of functional groups do most amino acids in Group II possess?
At least one atom (nitrogen, oxygen, or sulfur) with electron pairs available for hydrogen bonding
What is the primary characteristic of Group I amino acids?
They are hydrophobic.
What is the distinguishing feature of Group III acidic amino acids?
They possess carboxylic acid on their side chains.
What is the primary property of Group II polar, uncharged amino acids in aqueous solutions?
Their R groups can form hydrogen bonds with water.
Which amino acid is known for its unique ability to function in both acid and base catalysis near physiological pH values?
Histidine
Which group of amino acids possess at least one atom with electron pairs available for hydrogen bonding to water and other molecules?
Group II: Polar, Uncharged Amino Acids
Which amino acid is most often found in the active sites of protein enzymes?
Histidine
What type of amino acids are often found clustered on the surface of globular proteins in aqueous solutions?
Polar Amino Acids
What are nonstandard amino acids known for?
Being chemically modified after incorporation into a protein
What is the primary role of Group II amino acids in proteins?
Forming hydrogen bonds with water and other molecules
What is the significance of histidine's imidazole side chain?
It allows histidine to function in both acid and base catalysis near physiological pH values
What is the primary function of arginine, histidine, and lysine?
Participating in acid and base catalysis near physiological pH values
What are some prominent nitrogen-containing molecules that amino acids are precursors of?
Nucleotides and nucleic acids (DNA and RNA)
What kind of reactions can amino acids undergo via their various chemical functionalities?
Numerous chemical reactions including peptide bond formation and cysteine oxidation
Which group of amino acids is characterized by having side chains with electron pairs available for hydrogen bonding to water and other molecules?
Group II: Polar, Uncharged Amino Acids
Which amino acid group has R groups that are hydrophobic ('water fearing') due to their aliphatic or aromatic nature?
Group I: Nonpolar amino acids
Which two amino acids have carboxylic acid on their side chains that give them acidic (proton-donating) properties?
Aspartic acid and glutamic acid
Which group of amino acids possess at least one atom (nitrogen, oxygen, or sulfur) with electron pairs available for hydrogen bonding to water and other molecules?
Group II: Polar, Uncharged Amino Acids
What is the charge of the acidic amino acids aspartate and glutamate in an aqueous solution at physiological pH?
-1
What type of R groups do nonpolar amino acids in Group I have that makes them hydrophobic?
Aliphatic or aromatic R groups
What is the primary distinguishing characteristic of polar, uncharged amino acids in Group II?
Their R groups are hydrophilic ('water loving')
What property of the side chains of nonpolar amino acids in Group I leads to their burial in the protein interior in aqueous solutions?
Aromatic or aliphatic nature of the side chains
What role do polar, uncharged amino acids play in the folding of globular proteins in aqueous solutions?
They stabilize the folded structure through hydrogen bonding and van der Waals interactions
Which amino acid is capable of functioning in both acid and base catalysis near physiological pH values?
Histidine
Which group of amino acids is often found clustered on the surface of globular proteins in aqueous solutions?
Group IV: Basic Amino Acids
Which amino acid group is characterized by having side chains with electron pairs available for hydrogen bonding to water and other molecules?
Group II: Polar, Uncharged Amino Acids
Which reaction is particularly important due to its effect on protein structure?
Peptide bond formation
Which complex nitrogen-containing molecule are amino acids precursors of?
Nucleotides and nucleic acids (DNA and RNA)
Which amino acid is a precursor of serotonin and melatonin, and synthesized from histidine?
Histidine
What is the primary reason for arranging R-groups in an alternating orientation on either side of the polypeptide chain?
To enhance hydrophobic interactions
What are nonstandard amino acids primarily referred to as?
Amino acids that occur in living organisms but are not found in proteins
What is the primary role of heme, a complex amino-acid derived cofactor?
Facilitating oxygen transport in hemoglobin and myoglobin
What gives rise to folds that bring amino acids close together that are not near each other in primary structure?
Disulfide bonds between cysteine residues
Which group of amino acids has R groups that are hydrophobic ('water fearing') due to their aliphatic or aromatic nature?
Group I: Nonpolar amino acids
Which type of amino acids will ionize in an aqueous solution at physiological pH?
Group III: Acidic amino acids
What is the distinguishing feature of Group III acidic amino acids?
They have a carboxylic acid on their side chain
Which group of amino acids possess at least one atom with electron pairs available for hydrogen bonding to water and other molecules?
Group II: Polar, Uncharged Amino Acids
What directly specifies the sequence of amino acids in proteins?
DNA
Which force stabilizes protein structure as a result of interactions favoring the exclusion of water?
Hydrophobic interactions
Learn about the basic structure of an amino acid, including its composition of an amino group, carboxyl group, and unique side chain. Understand the significance of the α-carbon atom and the fundamental components that make up this organic molecule.
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