Podcast
Questions and Answers
Which of the following atoms is a hydrogen bond acceptor in a peptide bond?
Which of the following atoms is a hydrogen bond acceptor in a peptide bond?
At physiological pH, which of the following amino acid side chains is ionized?
At physiological pH, which of the following amino acid side chains is ionized?
What is the primary cause of van der Waals forces between molecules?
What is the primary cause of van der Waals forces between molecules?
What is the approximate distance of a hydrogen bond?
What is the approximate distance of a hydrogen bond?
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Which of the following is a characteristic of hydrophobic regions in a protein?
Which of the following is a characteristic of hydrophobic regions in a protein?
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What is the energy of a hydrogen bond, approximately?
What is the energy of a hydrogen bond, approximately?
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Which of the following is an example of a hydrogen bond donor?
Which of the following is an example of a hydrogen bond donor?
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What is the term for the sum of the attractive or repulsive forces between molecules, excluding covalent bonds, hydrogen bonds, and electrostatic interactions?
What is the term for the sum of the attractive or repulsive forces between molecules, excluding covalent bonds, hydrogen bonds, and electrostatic interactions?
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What type of glycosylation occurs at the -OH of thr and ser?
What type of glycosylation occurs at the -OH of thr and ser?
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What is the name of the structure that forms when three chains come together and are held by H-bonds between chains?
What is the name of the structure that forms when three chains come together and are held by H-bonds between chains?
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What is the primary function of the alpha helix in proteins?
What is the primary function of the alpha helix in proteins?
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What type of beta sheet structure is widespread in globular proteins?
What type of beta sheet structure is widespread in globular proteins?
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What is the sequence of amino acids in collagen?
What is the sequence of amino acids in collagen?
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What is the percentage of alpha helix structure in haemoglobin?
What is the percentage of alpha helix structure in haemoglobin?
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What is the name of the type of protein that has a high percentage of beta sheet structure and is found in silk fibres?
What is the name of the type of protein that has a high percentage of beta sheet structure and is found in silk fibres?
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What type of force is responsible for the hydrophobic effect in proteins?
What type of force is responsible for the hydrophobic effect in proteins?
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Which of the following types of bonds is responsible for maintaining the tertiary structure of proteins?
Which of the following types of bonds is responsible for maintaining the tertiary structure of proteins?
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What is the functional importance of amino acid side chains?
What is the functional importance of amino acid side chains?
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Which of the following proteins is an example of a structural protein?
Which of the following proteins is an example of a structural protein?
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What is the role of the peptide bond between amino acids?
What is the role of the peptide bond between amino acids?
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What is the result of defects in amino acid metabolism and mis-folding?
What is the result of defects in amino acid metabolism and mis-folding?
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What is the direction of a polypeptide chain?
What is the direction of a polypeptide chain?
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What is the role of disulphide bonds in protein structure?
What is the role of disulphide bonds in protein structure?
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What is the characteristic of most folded proteins?
What is the characteristic of most folded proteins?
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What is the primary reason why proteins are sensitive to denaturation?
What is the primary reason why proteins are sensitive to denaturation?
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What is the role of amino acid sequence in protein structure?
What is the role of amino acid sequence in protein structure?
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Why are proteins stable?
Why are proteins stable?
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What is the consequence of misfolding in proteins?
What is the consequence of misfolding in proteins?
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What is the significance of the case-based discussion on human disease?
What is the significance of the case-based discussion on human disease?
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What is essential for protein function?
What is essential for protein function?
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Study Notes
Protein Structure and Function
- Proteins perform various biological functions, including:
- Structural roles (e.g., collagen, keratin)
- Movement (e.g., actin, myosin)
- Enzymatic functions (e.g., trypsin, DNA polymerase)
- Transport (e.g., hemoglobin, transferrin)
- Hormone regulation (e.g., insulin)
- Receptor functions (e.g., acetylcholine receptor)
- Defense mechanisms (e.g., antibodies, clotting factors)
- Gene regulation (e.g., histones)
- Chromosome separation (e.g., tubulin)
Primary Structure
- A polypeptide chain consists of 20 common amino acids
- The first amino acid has an NH3+ group (N-terminal end)
- The last amino acid has a COO- group (C-terminal end)
Secondary Structure
- α-helix:
- Formed by hydrogen bonds between peptide bonds in the same polypeptide chain
- Regular right-handed helix with 3.6 residues per turn
- R groups are on the outside of the helix
- Stabilized by hydrogen bonds
- β-pleated sheet:
- Formed by hydrogen bonds between peptide chains
- Linear peptide chains with side chains alternately above and below the plane of the sheet
Tertiary Structure
- The 3D shape of a polypeptide chain
- Consists of a number of different supersecondary structures (domains)
Quaternary Structure
- The 3D shape of a functional protein formed by multiple subunits
- Examples: hemoglobin (α2β2)
Forces that Stabilize Protein Structure
- Covalent:
- Disulfide bridges (not present in all proteins)
- Non-covalent:
- Hydrogen bonds
- Electrostatic interactions
- Van der Waals forces
- Hydrophobic effect
Hydrogen Bonds
- Formed between two electronegative atoms competing for the same H atom
- H-Bond donors (D): O-H, N-H
- H-Bond acceptors (A): C=O, =N-
Electrostatic Interactions
- Between charged side chains
- At physiological pH, Asp and Glu are ionized, while Lys and Arg are also ionized
Van der Waals Forces
- The sum of attractive or repulsive forces between molecules
- Excludes covalent bonds, hydrogen bonds, and electrostatic interactions
- Dependent on the dipole effect caused by the unequal distribution of electrons
Hydrophobic Effects
- Hydrophobic regions of a protein fold to minimize contact with the aqueous environment
- Hydrophobic regions are unable to form hydrogen bonds
Protein Folding and Stability
- The amount of stabilization energy in a protein is quite small
- Proteins are sensitive to denaturation by pH, temperature, and ionic strength
- Amino acid sequence encodes the final structure and the pathway that leads to that structure
- Misfolding can cause disease
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Description
This quiz covers the various biological functions performed by proteins, including structural roles, movement, enzymatic functions, and more.
