Protein Structure and Function
42 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is a key characteristic of quaternary protein structure?

  • It involves a single polypeptide chain.
  • It does not exhibit hydrogen bonding.
  • It is only formed by fibrous proteins.
  • It results from interactions between multiple polypeptide chains. (correct)

Which of the following correctly describes an advantage of quaternary protein structure?

  • Improved genetic economy and efficiency. (correct)
  • Independence of polypeptide chains in function.
  • Increase in surface-to-volume ratio.
  • Total loss of cooperativity.

Which types of interactions are crucial for stabilizing quaternary protein structures?

  • Hydrophobic interactions solely.
  • Covalent bonds exclusively.
  • Only ionic bonds.
  • Hydrogen bonding and disulphide bonds. (correct)

What differentiates globular proteins from fibrous proteins?

<p>Fibrous proteins are elongated and insoluble in water. (A)</p> Signup and view all the answers

Why is protein folding considered thermodynamically favorable?

<p>It decreases energy and stabilizes the protein. (B)</p> Signup and view all the answers

What type of reaction leads to the formation of a peptide bond?

<p>Dehydration synthesis (C)</p> Signup and view all the answers

Which two amino acids are known to form disulfide bridges?

<p>Cysteine and Methionine (B)</p> Signup and view all the answers

What is the byproduct of the dehydration synthesis reaction that forms a peptide bond?

<p>Water (B)</p> Signup and view all the answers

How does the structure of a peptide bond affect protein stability?

<p>It has partial double bond character, restricting rotation. (D)</p> Signup and view all the answers

Which of the following hormones is associated with childbirth?

<p>Oxytocin (D)</p> Signup and view all the answers

Substance P primarily functions as which type of biological molecule?

<p>A neuropeptide (B)</p> Signup and view all the answers

Which antibiotic is specifically used against gram-negative bacteria?

<p>Polymyxin (B)</p> Signup and view all the answers

What is the structure of a peptide bond?

<p>–CO–NH– (A)</p> Signup and view all the answers

What is the role of proline in the formation of alpha helices?

<p>It acts as a helix breaker. (B)</p> Signup and view all the answers

Which type of beta sheet is characterized by a stronger hydrogen bond network?

<p>Antiparallel beta sheets (A)</p> Signup and view all the answers

Which residue is considered a strong helix former?

<p>Alanine (B)</p> Signup and view all the answers

What feature of the alpha helix contributes to its dipole moment?

<p>The orientation of peptide bonds. (B)</p> Signup and view all the answers

Which of the following interactions can affect the structure of an alpha helix?

<p>Side chain interactions 3-4 amino acids apart. (B)</p> Signup and view all the answers

How do side chains in beta sheets orient themselves?

<p>They alternate in up and down directions. (A)</p> Signup and view all the answers

What is the typical number of strands found in globular protein beta sheets?

<p>2-22 strands (B)</p> Signup and view all the answers

Which amino acid is known to terminate alpha helices due to its flexibility?

<p>Glycine (B)</p> Signup and view all the answers

What stabilizes the 180° turn in a beta turn?

<p>Hydrogen bond from a carbonyl oxygen to an amide proton three residues down the sequence (A)</p> Signup and view all the answers

Which amino acid is commonly found in position 2 of a type 1 beta turn?

<p>Proline (C)</p> Signup and view all the answers

What method is used to measure the secondary structure of proteins?

<p>Circular Dichroism (CD) (A)</p> Signup and view all the answers

How are beta sheet disruptions assessed concerning mutations?

<p>They assess whether the mutation alters protein folding (B)</p> Signup and view all the answers

In Circular Dichroism, what characteristic indicates an alpha helix structure?

<p>Negative peak followed by a double peak (A)</p> Signup and view all the answers

What type of interactions primarily stabilize the tertiary structure of a protein?

<p>Hydrophobic and polar interactions among side chains (A)</p> Signup and view all the answers

Which structural feature is characterized by a linear arrangement where electrons flow better when aligned?

<p>Antiparallel arrangement (C)</p> Signup and view all the answers

Which amino acid is typically found in position 3 of a type 1 beta turn?

<p>Glycine (B)</p> Signup and view all the answers

What effect can chaotropic agents such as urea and guanidinium hydrochloride have on proteins?

<p>They denature the proteins by disrupting interactions. (A)</p> Signup and view all the answers

What is indicated by the melting curve of a protein during denaturation?

<p>The increase in accessibility of peptide bonds to a dye at elevated temperatures. (D)</p> Signup and view all the answers

According to Ken Dill's folding funnel hypothesis, what guides the folding of proteins to their native structure?

<p>The thermodynamically most favorable conformation. (C)</p> Signup and view all the answers

What is the significance of the Levinthal paradox in protein folding?

<p>It illustrates the improbability of randomly searching all conformations. (D)</p> Signup and view all the answers

What role do internal residues play in protein folding?

<p>They direct the protein to its native conformation via hydrophobic interactions. (C)</p> Signup and view all the answers

What is the primary structural feature of globular proteins that influences their folding?

<p>Hydrophobic side chains are buried to minimize contact with water. (A)</p> Signup and view all the answers

Which amino acids are likely to be found on the surface of globular proteins in contact with water?

<p>Serine and Asparagine (C)</p> Signup and view all the answers

What is a key characteristic of the collagen protein?

<p>It is composed of several major types that assemble in a specific way. (D)</p> Signup and view all the answers

Which amino acid is present in high amounts specifically in collagen?

<p>Proline (C)</p> Signup and view all the answers

What is the structure of alpha keratin primarily composed of?

<p>A bundle of alpha helices. (A)</p> Signup and view all the answers

How do the alpha helices in coiled-coil motif proteins interact?

<p>They form left-handed superhelical structures. (B)</p> Signup and view all the answers

What role do disulfide bonds play in alpha keratin?

<p>They cross-link adjacent chains for structural stability. (C)</p> Signup and view all the answers

Which of the following best describes the structure of silk fibroin?

<p>It forms primarily beta strands in a repetitive sequence. (D)</p> Signup and view all the answers

Flashcards

Alpha Helix Structure

A common secondary protein structure where the polypeptide chain forms a right-handed helical coil stabilized by hydrogen bonds between the backbone amide and carbonyl groups of every fourth amino acid.

Helix Stability Factors

The stability of an alpha helix is influenced by the amino acid sequence, with certain amino acids promoting or hindering helix formation.

Helix Breakers

Certain amino acids like Proline and Glycine tend to disrupt alpha-helical structures due to steric hindrance or flexibility issues.

Beta Sheet Structure

A secondary protein structure formed by multiple strands of polypeptide chains arranged in a pleated sheet-like conformation.

Signup and view all the flashcards

Beta Sheet Stabilizing Interactions

Beta Sheet stability relies on hydrogen bonds between backbone amides in different strands (up to 15 residues), creating a sheet like structure

Signup and view all the flashcards

Parallel Beta Sheets

Beta sheets where polypeptide chains run in the same direction, creating bent hydrogen bonds.

Signup and view all the flashcards

Antiparallel Beta Sheets

Beta sheets where polypeptide chains run in opposite directions creating a linear hydrogen bond network.

Signup and view all the flashcards

Helix Dipole

Alpha helices have an overall dipole moment originating from the polarity of peptide bonds. The negative side of the dipole is on the carbonyl side of the peptide bonds.

Signup and view all the flashcards

Amino Acids

Building blocks of proteins, linked together by peptide bonds.

Signup and view all the flashcards

Peptide Bond

Covalent bond between two amino acids formed by dehydration synthesis.

Signup and view all the flashcards

Protein Synthesis

Process of assembling amino acids into proteins.

Signup and view all the flashcards

Hormones

Chemical messengers that regulate bodily functions.

Signup and view all the flashcards

Insulin

Hormone regulating blood sugar levels.

Signup and view all the flashcards

Oxytocin

Hormone associated with childbirth and social bonding.

Signup and view all the flashcards

Neuropeptides

Peptides that transmit signals in the nervous system.

Signup and view all the flashcards

Substance P

Neuropeptide involved in pain transmission.

Signup and view all the flashcards

Antibiotics

Drugs that kill or inhibit the growth of bacteria.

Signup and view all the flashcards

Polymyxin

Antibiotic targeting Gram-negative bacteria.

Signup and view all the flashcards

Bacitracin

Antibiotic targeting Gram-positive bacteria.

Signup and view all the flashcards

Peptide bond form

formed between the carboxyl group of one amino acid and the amino group of another.Release water (Hâ‚‚O)

Signup and view all the flashcards

Disulfide Bridge

Covalent bond between two cysteine amino acids.

Signup and view all the flashcards

Amino Acids with sulfur

Methionine and Cysteine.

Signup and view all the flashcards

Protein Folding

The process by which a polypeptide chain assumes its three-dimensional structure.

Signup and view all the flashcards

Globular Proteins

Water-soluble proteins with a roughly spherical shape.

Signup and view all the flashcards

Fibrous Proteins

Insoluble proteins with elongated shapes, often providing structural support.

Signup and view all the flashcards

Quaternary Structure

The arrangement of multiple polypeptide chains in a protein.

Signup and view all the flashcards

Protein Stability

The ability of a protein to maintain its three-dimensional structure.

Signup and view all the flashcards

Hydrogen Bonding

A weak attraction between a hydrogen atom and an electronegative atom (like oxygen or nitrogen).

Signup and view all the flashcards

Disulfide Bonds

A strong covalent bond between two cysteine amino acids.

Signup and view all the flashcards

Cooperative Binding

Binding of one molecule to a protein can influence the binding of subsequent molecules.

Signup and view all the flashcards

Haemoglobin

A protein that carries oxygen in red blood cells, an example of a quaternary structure.

Signup and view all the flashcards

Aligned Electrons

Aligned electrons in a protein allow for better electron flow.

Signup and view all the flashcards

Antiparallel B-sheet

B-sheets are strands that run in opposite directions. They are consistently linear.

Signup and view all the flashcards

B-turns

B-turns are abrupt 180° turns in polypeptide chains.

Signup and view all the flashcards

B-turn Stabilizing

Hydrogen bonds between carbonyl oxygens and amide protons stabilize B-turns.

Signup and view all the flashcards

Proline in B-turns

Proline is often found in position 2 of a B-turn, assisting in the 180° turn and providing stability.

Signup and view all the flashcards

Circular Dichroism (CD)

CD is a technique used to measure secondary structures in proteins.

Signup and view all the flashcards

CD Measurement

Circular dichroism measures the difference in absorption of left and right circularly polarized light by chiral chromophores.

Signup and view all the flashcards

Alpha Helix CD

Alpha helix structures in a protein show a negatively charged circular dichroism signal with a double peak.

Signup and view all the flashcards

Beta Sheet CD

Beta sheets give a positive, then negative, circular dichroism signal.

Signup and view all the flashcards

Random Coil CD

Random coils show a flat signal shape in circular dichroism.

Signup and view all the flashcards

Protein Tertiary Structure

The overall 3D arrangement of atoms in a protein.

Signup and view all the flashcards

Tertiary Structure Stabilizers

Weak interactions (hydrophobic/polar), and disulfide bonds stabilize tertiary structure.

Signup and view all the flashcards

Protein Denaturation

The loss of a protein's 3D structure and function due to external factors.

Signup and view all the flashcards

Protein Melting Temperature (Tm)

The temperature at which a protein transitions from a folded to an unfolded state.

Signup and view all the flashcards

Melting Curve

A graph showing how the dye intensity changes as the temperature increases, allowing scientists to infer how many protein bonds are disrupted.

Signup and view all the flashcards

Protein Folding

The process by which a protein adopts its native 3D structure.

Signup and view all the flashcards

Globular proteins

Proteins with a complex, roughly spherical 3D shape, often involved in metabolic processes.

Signup and view all the flashcards

Levinthal Paradox

The problem that random exploration of all possible conformations is highly improbable.

Signup and view all the flashcards

Protein Folding Funnel

A model that shows how protein folding is not random, but a directional process towards a stable conformation.

Signup and view all the flashcards

Ramachandran plot

A diagram showing the allowed angles of amino acid residue phi and psi. Used to predict protein structure.

Signup and view all the flashcards

Thermodynamics of Protein Folding

Proteins fold into their lowest energy conformation.

Signup and view all the flashcards

Fibrous proteins

Proteins with elongated structures, often providing structural support and strength.

Signup and view all the flashcards

Hydrophobic Effect

The driving force of protein folding, where nonpolar amino acids cluster together to minimize contact with water.

Signup and view all the flashcards

Collagen

A fibrous protein found in connective tissues, providing strength and flexibility.

Signup and view all the flashcards

Elastin

A fibrous protein that gives elasticity to tissues.

Signup and view all the flashcards

Protein Sequencing Methods

Methods used to determine the amino acid order in a polypeptide chain, Examples: Sanger, Edman, Mass Spectrometry.

Signup and view all the flashcards

Alpha Helix Coiled-Coil

A stable protein structure where two alpha helices wrap around each other.

Signup and view all the flashcards

Alpha Keratin

A fibrous protein that forms strong, durable structures like hair and nails, high levels of cysteine.

Signup and view all the flashcards

Silk Fibroin

A fibrous protein that forms beta sheets, used in silk.

Signup and view all the flashcards

Study Notes

Protein Structure and Function

  • Proteins are versatile macromolecules found in all living organisms, with diverse functions in biological processes.
  • Proteins are the main agents of biological function, performing various roles such as catalysis, transport, structure, and motion.

Catalysis

  • Catalysis is the acceleration of chemical reactions by a catalyst, a substance that increases the reaction rate without being consumed.
  • Enzymes are proteins that act as catalysts in biological systems, speeding up biochemical reactions.
  • Examples include enolase in glycolysis and DNA polymerase in DNA replication.

Transport

  • Proteins facilitate the transport of molecules across cell membranes or within the body.
  • Haemoglobin transports oxygen in the blood.
  • Lactose permease transports lactose across cell membranes.

Structure

  • Proteins provide structural support and shape to cells and tissues.
  • Examples include collagen (connective tissue) and keratin (nails, hair, feathers, and horns).

Motion

  • Proteins are essential for cellular movement and motility.
  • Myosin and actin are involved in muscle contraction.
  • Other proteins are involved in various types of cell movement.

Protein Structure

  • Amino acids are the building blocks of proteins.
  • The primary structure is the linear sequence of amino acids in a polypeptide chain.
  • The secondary structure involves interactions like alpha-helices and beta-sheets, formed by hydrogen bonding between amino acids.
  • The tertiary structure is the three-dimensional shape of the entire polypeptide chain.
  • The quaternary structure is the arrangement of multiple polypeptide subunits in a protein complex.

Amino Acids

  • There are 20 common amino acids.
  • Each has a central carbon atom (alpha carbon) bonded to four groups: an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group), which creates the diversity among the 20 different amino acids
  • Knowledge of their names, structures, and properties is crucial for understanding protein function.

Chirality

  • Most amino acids are chiral, meaning they have four different substituents around the alpha carbon, and thus exist in two isomeric forms (L and D). Only L-forms appear in proteins.

Common Amino Acids Classification

  • Common amino acids can be grouped into five categories based on their R-group characteristics: nonpolar, aliphatic, aromatic, polar, uncharged, positively charged, and negatively charged.

Peptide Bonds

  • Peptide bonds form between the carboxyl group of one amino acid and the amino group of the next amino acid in a polypeptide chain.
  • The peptide bond has characteristics of partial double bond character and resonance, which affects the structure and stability of the protein.

Unusual Amino Acids

  • Certain amino acids are not produced by standard ribosome processes.
  • Arise by post-translational modifications.
  • Example: selenocysteine and pyrrolysine.

Peptide Ends

  • Peptides have amino and carboxyl termini, crucial for directing and regulating other protein functions.
  • Numbering and naming of amino acids starts from the amino terminus (N terminus).

Protein Folding

  • Protein folding leads to a three-dimensional structure necessary to function.
  • The hydrophobic effect plays a significant role in protein folding by pushing hydrophobic side chains towards the interior of the protein.
  • Hydrogen bonding between amino acid residues can further stabilize protein structure.

Denaturation

  • Denaturation is the process where proteins lose their three-dimensional structure.
  • Denaturation is often caused by heat, pH extremes, organic solvents, and chemicals called chaotropes
  • Loss of function in protein commonly happens with denaturation.

Protein Synthesis

  • Synthesis occurs from C terminus to N terminus.
  • Signal sequence directs protein to specific locations within cell.
  • Proteins are often modified after synthesis.

Protein Sequencing

  • Determines the order of amino acids in a protein.
  • Methods such as Edman degradation and mass spectrometry.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

BCMB2002 Weeks 1-4 Basics PDF

Description

Explore the fascinating world of proteins, their structures, and their essential roles in biological systems. This quiz covers key functions such as catalysis, transport, and structural support provided by proteins. Test your knowledge on various enzymes and protein examples in living organisms.

More Like This

Enzymes and Their Functions
15 questions

Enzymes and Their Functions

ClearChalcedony8307 avatar
ClearChalcedony8307
Biology Chapter: Proteins and Enzymes
21 questions

Biology Chapter: Proteins and Enzymes

CherishedDogwood4258 avatar
CherishedDogwood4258
Enzymes and Their Function
13 questions

Enzymes and Their Function

WittyEvergreenForest avatar
WittyEvergreenForest
Protein Structure and Function
5 questions

Protein Structure and Function

AstonishedAmber7407 avatar
AstonishedAmber7407
Use Quizgecko on...
Browser
Open
Browser
Browser