Proteins Flashcards
What are the four main elements found in all proteins?
nitrogen
carbon
hydrogen
oxygen
Some proteins are involved in gene expression and include ___ which assists in synthesizing RNA from DNA. Other proteins are considered defensive proteins and include ___which help destroy microorganisms.
RNA Polymerase, antibodies
Proteins are made up of chains of ___ acids.
amino
What are the three major structural components of an amino acid?
Side chain (R)
Carboxyl group
Amino group
An amino acid may be described as nonpolar, polar uncharged, or polar charged based on the chemical properties of its ___ chain.
side (R)
The main elements that make up proteins are carbon, hydrogen, __, and __, in addition to small amounts of other elements, like sulfur.
nitrogen, oxygen
How do the amino acid side chains affect proteins?
Amino acid side chains play a critical role in the structure and function of a protein.
Cell signaling protein function
Allows cells to communicate with each other
Metabolic enzyme function
Increases the rate of a chemical reaction
Transporter function
Aids in the movement of solutes across the plasma membrane
Motor protein function
Initiates movement
What are the monomers found in proteins?
Amino acids
Which of the following accurately describes the chemical structure of a typical amino acid found in a protein?
- A central carbon is bound to a carbonyl group, an amino group, and two R groups.
- A central carbon atom is bound to an amino group, carboxyl group, a side chain, and a hydrogen atom.
- A central carbon is double bonded to both an amino group and a carboxyl group.
A central carbon atom is bound to an amino group, carboxyl group, a side chain, and a hydrogen atom.
Amino acids are categorized based on:
their side chains
How can amino acid side chains affect the structure and function of a protein?
Amino acid side chains play a role in protein folding.
Amino acid side chains are involved in catalysis at the active site of enzymes.
What process is responsible for linking amino acids together to form polypeptides?
Dehydration reactions
In a peptide bond, which parts of the two amino acids are joined together?
The amino group of one amino acid and the carboxyl group of the other
When amino acids are linked together they form a large molecule called a(n)
polypeptide.
Proteins are made by __ reactions, in which water is removed as amino acids are linked together to form polypeptides.
dehydration
When a peptide bond is formed, two amino acids are linked between the __ group of one amino acid and the __ group of the other.
amino, carboxyl
A type of covalent bond called a ___ bond forms between the carboxyl group of one amino acid and the amino group of another amino acid.
peptide
A polypeptide is a chain of
amino acids
Between what two atoms are peptide bonds located in the backbone of a polypeptide?
Carbon and nitrogen
A free __ group is found at the N-terminus of a protein, and a free __ group is found at the C-terminus.
amino, carboxyl
A protein whose highest level of structure is tertiary structure contains:
one polypeptide folded into its three-dimensional structure
Where are the peptide bonds in a polypeptide located?
In the polypeptide backbone
What functional groups are found at the N-terminus and the C-terminus of a polypeptide?
A carboxyl group is at the C-terminus.
An amino group is at the N-terminus.
What is the primary structure of a protein?
The amino acid sequence of a polypeptide
What is the secondary structure of a protein?
The repeating pattern of folding between regions
Match the level of protein organization with the proper description:
primary
the linear sequence of amino acids
Match the level of protein organization with the proper description:
secondary
repetitive folding patterns such as α helix and β pleated sheet
Match the level of protein organization with the proper description:
tertiary
the three-dimensional structure of a polypeptide
Match the level of protein organization with the proper description:
quaternary
two or more interacting polypeptides
What are the two types of secondary structure found in proteins?
β pleated sheet
α helix
Between what two atoms are peptide bonds located in the backbone of a polypeptide?
Carbon and nitrogen
What type of bond is responsible for the formation of α helices and β pleated sheets?
Hydrogen bond
The amino acid sequence of a polypeptide is called the ___ structure.
primary
The ___ structure of a polypeptide is the repeating pattern of folding stabilized by hydrogen bonds.
secondary
What level of protein organization refers to the three-dimensional shape of a polypeptide that includes all secondary structures and interactions between side chains?
Tertiary structure
A protein whose highest level of structure is tertiary structure contains:
one polypeptide folded into its three-dimensional structure
What level of protein structure is stabilized by interactions among the side chains of the polypeptide?
Tertiary structure
The two basic types of secondary structure are the alpha __ and the beta-pleated __.
helix, sheet
Proteins that have quaternary structure consist of at least __ polypeptide(s).
2
The elements of a polypeptide’s secondary structure, the α helix and β pleated sheets are stabilized by ___ bonds.
hydrogen
What factors contribute to protein-protein interactions?
van der Waals effects
hydrogen bonding
hydrophobic effects
ionic bonding
Match each bond or interaction with the correct description.
hydrogen bond
Bond between partial positive and negative charges on different amino acids
Match each bond or interaction with the correct description.
ionic bond
Bond between oppositely charged amino acid side chains
Match each bond or interaction with the correct description.
disulfide bond
Covalent bond between two cysteines
Match each bond or interaction with the correct description.
hydrophobic effect
Interaction between nonpolar amino acids
Match each bond or interaction with the correct description.
van der Waals force
Weak, temporary attraction between two atoms
The three-dimensional shape of a polypeptide is the ___ structure.
tertiary
Which levels of protein structure are stabilized by hydrogen bonds?
Secondary structure
Quaternary structure
Tertiary structure
Interactions among the side chains of amino acids help to stabilize the ___ structure of a polypeptide.
teritary
What level of protein structure occurs when two or more polypeptides interact with each other to form a functional protein?
Quaternary structure
What type of bonds can form between positively and negatively charged side chains within a polypeptide?
Ionic bonds
Interactions between different proteins can be stabilized by four main factors: __ bonds, ionic bonds, __ effect, and van der __ dispersion forces.
hydrogen, hydrophobic, waals
Which of the following bonds and interactions contribute directly to a protein’s tertiary structure?
- Peptide bonds
- Hydrogen bonds
- Disulfide bonds
- Hydrophobic effect
- van der Waals forces
- Glycosidic bonds
- Ionic bonds
Hydrogen bonds
Disulfide bonds
Hydrophobic effect
van der Waals forces
Ionic bonds
Hydrogen bonds can form:
within a polypeptide and between different polypeptide chains
What level of protein structure is stabilized by interactions among the side chains of the polypeptide?
Tertiary structure
__ bonds promote protein folding when they form between oppositely-charged side chains of a protein.
hydrogen
Amino acid side chains that are nonpolar tend to exclude water and contribute to __ effects involved in protein folding.
hydrophobic
What factors contribute to protein-protein interactions?
ionic bonding
hydrophobic effects
hydrogen bonding
van der Waals effects
What type of bond can form between the side R groups of two cysteine amino acids to stabilize protein structure?
Disulfide bond
Which levels of protein structure are stabilized by hydrogen bonds?
Quaternary structure
Tertiary structure
Secondary structure
Interactions among the side chains of amino acids help to stabilize the ___ structure of a polypeptide.
tertiary
What functional group is involved in disulfide bridges?
Sulfhydryl
Hydrophobic effects play a major role in what protein structures?
quaternary structure
tertiary structure
___ bridges can form between the side chains of two cysteine amino acids.
Disulfide
A disulfide bond can form between two cysteines located:
within the same polypeptide chain or in different polypeptide chains
When a protein is unfolded or ______, it is no longer functional.
denatured
The tertiary structure of a polypeptide is predominantly determined by its __ structure.
primary
Disulfide bridges are covalent bonds between ___ groups of cysteine side chains.
sulfhydryl
Amino acid side chains that are nonpolar tend to exclude water and contribute to __ effects involved in protein folding.
hydrophobic
A disulfide bond between two cysteines in the same polypeptide chain can help to stabilize the ______ structure of a protein.
tertiary
What happens when a protein is denatured?
Its three-dimensional structure is disrupted.
What is the main determinant of a protein’s tertiary structure?
Its primary structure
What functional group is involved in disulfide bridges?
Sulfhydryl
