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Questions and Answers
Which amino acids are known to disrupt the formation of α helices?
Which amino acids are known to disrupt the formation of α helices?
- Proline and glycine (correct)
- Aspartate and serine
- Leucine and isoleucine
- Threonine and cysteine
What stabilizes the structure of β-sheets?
What stabilizes the structure of β-sheets?
- Disulfide bonds
- Ionic bonds
- Peptide bonds
- Hydrogen bonds (correct)
Which of the following statements about β-bends is true?
Which of the following statements about β-bends is true?
- They consist of five amino acids, one being proline.
- They are typically composed of four amino acids. (correct)
- They are stable only in α helices.
- They do not involve the formation of any bonds.
In the context of protein structure, what does the term 'domain' refer to?
In the context of protein structure, what does the term 'domain' refer to?
What characterizes the tertiary structure of globular proteins?
What characterizes the tertiary structure of globular proteins?
What is the term for the specific sequence of amino acids in a protein?
What is the term for the specific sequence of amino acids in a protein?
Which type of bond is primarily responsible for the formation of peptide bonds between amino acids?
Which type of bond is primarily responsible for the formation of peptide bonds between amino acids?
Which of the following is NOT a characteristic of peptide bonds?
Which of the following is NOT a characteristic of peptide bonds?
What stabilizes the α-helix structure in proteins?
What stabilizes the α-helix structure in proteins?
Which of the following describes a function of glutathione (GSH)?
Which of the following describes a function of glutathione (GSH)?
Which conformation of protein structure is characterized by spiral structures formed by tightly packed polypeptides?
Which conformation of protein structure is characterized by spiral structures formed by tightly packed polypeptides?
What is the main difference between globular and fibrous proteins?
What is the main difference between globular and fibrous proteins?
What type of interaction primarily stabilizes the quaternary structure of proteins?
What type of interaction primarily stabilizes the quaternary structure of proteins?
What type of molecular chaperones are specifically known to increase in response to high temperatures?
What type of molecular chaperones are specifically known to increase in response to high temperatures?
Which factors can lead to protein denaturation?
Which factors can lead to protein denaturation?
What is the primary role of molecular chaperones in protein folding?
What is the primary role of molecular chaperones in protein folding?
Which of these statements about prions is true?
Which of these statements about prions is true?
In which cellular organelle does protein folding primarily take place?
In which cellular organelle does protein folding primarily take place?
Which structure is characterized by having two or more polypeptides?
Which structure is characterized by having two or more polypeptides?
Which of the following interactions helps to stabilize the quaternary structure of proteins?
Which of the following interactions helps to stabilize the quaternary structure of proteins?
What can result from exposure to extreme heat or pH changes in proteins?
What can result from exposure to extreme heat or pH changes in proteins?
Which type of protein classification describes proteins composed of only a single polypeptide chain?
Which type of protein classification describes proteins composed of only a single polypeptide chain?
What term is used for proteins made up of multiple polypeptide chains of the same type?
What term is used for proteins made up of multiple polypeptide chains of the same type?
Which protein is specifically noted for being a conjugated protein containing a heme group?
Which protein is specifically noted for being a conjugated protein containing a heme group?
Which of the following protein functions is mainly structural in nature?
Which of the following protein functions is mainly structural in nature?
Which protein is least likely to be classified as a globular protein due to its structural characteristics?
Which protein is least likely to be classified as a globular protein due to its structural characteristics?
What type of interaction primarily stabilizes the secondary structures of proteins?
What type of interaction primarily stabilizes the secondary structures of proteins?
Which type of polypeptide arrangement is characterized by strong but flexible properties and is water insoluble?
Which type of polypeptide arrangement is characterized by strong but flexible properties and is water insoluble?
Which of the following proteins is an example of a storage protein in the human body?
Which of the following proteins is an example of a storage protein in the human body?
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Study Notes
Protein Structure & Function
- Proteins possess four levels of structure: primary, secondary, tertiary, and quaternary.
- Primary structure comprises the sequence of amino acids linked by peptide bonds.
- Peptide bonds are characterized by being partial double-bonded, uncharged but polar, rigid, and planar.
- Secondary structures include α-helix, β-sheets, and β-bends, stabilized primarily by hydrogen bonds.
- Tertiary structure refers to the overall 3D configuration of polypeptide chains, stabilized by hydrogen bonds, disulfide bonds, hydrophobic interactions, and ionic interactions.
- Quaternary structure exists in proteins composed of multiple polypeptide chains, such as hemoglobin.
- Prions are misfolded proteins that induce misfolding in normally folded proteins, causing diseases like Creutzfeldt-Jakob disease and mad cow disease.
- Protein denaturation involves the loss of structure due to extreme conditions (heat, pH, etc.), disrupting the protein's function.
Types of Bonds
- Covalent bonds include peptide bonds and disulfide bonds.
- Non-covalent interactions include hydrophobic interactions, ionic interactions, and hydrogen bonds.
Protein Classification
- Monomeric proteins consist of a single polypeptide chain; multimeric proteins contain multiple chains (homomultimer or heteromultimer).
- Fibrous proteins are structurally strong, insoluble in water, containing long strands (e.g., keratin, collagen).
- Globular proteins are soluble in water and perform diverse functions (e.g., enzymes, regulatory proteins).
- Conjugated proteins include prosthetic groups and examples include hemoglobin and phosphoproteins.
Functions of Proteins
- Functions include:
- Enzymatic: e.g., Amylase, Hexokinase.
- Structural: e.g., Collagen.
- Transport: e.g., Albumin.
- Motor: e.g., Actin.
- Storage: e.g., Ferritin.
- Signaling: e.g., Integrins, cadherins.
- Receptors: e.g., G-protein coupled receptors (GPCRs).
- Gene regulation: e.g., transcription factors like HIF-1.
Physiologically Important Peptides
- Examples include Glutathione (detoxification, antioxidant), Oxytocin, and Vasopressin.
Protein Folding and Chaperones
- Protein folding occurs primarily in the endoplasmic reticulum, aided by molecular chaperones which assist in proper protein configuration.
Key Diseases Related to Proteins
- Prion-related diseases include:
- Bovine spongiform encephalopathy (BSE)
- Creutzfeldt-Jakob disease (CJD)
- Scrapie
- Kuru (associated with cannibalism)
Answers to Questions
- Q1. Stabilizing bonds for secondary structures are Hydrogen bonds.
- Q2. Lactate dehydrogenase is likely to have a quaternary structure.
- Q3. Scrapie is caused by prion proteins.
- Q4. Ferritin is categorized as a Storage protein.
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