Amino Acids and Polypeptide Chains

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What type of bonding stabilizes the α-helix?

electrostatic bonding

ionic bonding

hydrogen bonding (correct)

covalent bonding

What is the primary structure of keratins?

β-bend

α-helical (correct)

β-pleated sheet

random coil

Why does proline disrupt an α-helix?

It forms ionic bonds with other amino acids

Its secondary amino group is geometrically compatible with the right-handed spiral of the α-helix

It has a bulky side chain

Its secondary amino group is not geometrically compatible with the right-handed spiral of the α-helix (correct)

What type of amino acids can interfere with the formation of an α-helix?

All of the above Signup and view all the answers

What is a characteristic of β-sheets?

All peptide bond components are involved in hydrogen bonding Signup and view all the answers

What is the arrangement of β-strands in an antiparallel β-sheet?

The N-terminal and C-terminal ends of the β-strands alternate Signup and view all the answers

What is the function of β-bends?

To join two units of secondary structures Signup and view all the answers

What is the secondary structure that myoglobin has?

α-helical Signup and view all the answers

What is the correct order of reading an amino acid sequence?

From the N-terminal to the C-terminal end Signup and view all the answers

What type of interactions occur between negatively charged groups and positively charged groups?

Ionic interactions Signup and view all the answers

What is the term used to describe proteins that consist of multiple polypeptide chains?

Multi-subunit protein Signup and view all the answers

What is the level of protein structure that describes the sequence of amino acids?

Primary structure Signup and view all the answers

What is the characteristic of fibrous 3D structure?

Less folded and more extended Signup and view all the answers

What is the type of bond that keeps the entire peptide in a rigid planar configuration?

Peptide bond Signup and view all the answers

What is the term for the arrangement of polypeptide subunits in a protein?

Quaternary structure Signup and view all the answers

What is an example of a protein with a dimeric quaternary structure?

Insulin Signup and view all the answers

What is the term used to describe the local conformation of a part of a polypeptide?

Secondary structure Signup and view all the answers

What is the result of mild denaturation of a protein?

Disruption of tertiary or quaternary structures Signup and view all the answers

What is the most common type of secondary structure in proteins?

α-Helix Signup and view all the answers

What is the shape of the α-helix?

Spiral Signup and view all the answers

What is an example of a physical agent of denaturation?

Heat Signup and view all the answers

What is the result of abnormalities in the amino acid sequences of proteins?

Genetic diseases Signup and view all the answers

What is a characteristic of denatured proteins?

They are more easily digested Signup and view all the answers

What is the result of harsh denaturation conditions on a protein?

Fragmentation of the chain Signup and view all the answers

What is the composition of amyloid proteins?

Aggregates of twisted β-pleated sheet fibrils Signup and view all the answers

What is the result of protein accumulation in tissues and organs?

Severe disruption of normal physiological processes Signup and view all the answers

In which of the following conditions can amyloid deposit be produced?

Chronic inflammatory diseases Signup and view all the answers

What is the purpose of protein turnover?

To maintain constant protein content in healthy adults Signup and view all the answers

How much protein is hydrolyzed and resynthesized daily?

300-400 g/day Signup and view all the answers

What determines the rate of protein degradation?

Half-life of the protein Signup and view all the answers

Which peptide is 200 times sweeter than sucrose and used as a low-calorie artificial sweetener?

Aspartame Signup and view all the answers

What is the significant function of Glutathione in proteins?

Prevents the oxidation of sulfhydryl (SH) groups to disulfide (SS) groups Signup and view all the answers

Which hormone is produced by the posterior pituitary gland and stimulates the kidney to retain water?

Vasopressin (ADH) Signup and view all the answers

What role do molecular chaperones play in protein folding?

They bind reversibly to unfolded polypeptide segments to prevent misfolding. Signup and view all the answers

What structure is predominantly found in proteins in persons with amyloidosis?

Beta-pleated sheet Signup and view all the answers

What does the process of protein folding seek to achieve?

Low-energy state Signup and view all the answers

Which peptide causes contraction of the uterus?

Oxytocin Signup and view all the answers

What is the common result of protein misfolding?

Formation of long, fibrillar protein assemblies Signup and view all the answers