Protein Function and Structure Flashcards

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Questions and Answers

What are the major functions of proteins? (Select all that apply)

Catalysis (correct)

Structural Support (correct)

Binding (correct)

Movement (correct)

Signal Transduction (correct)

Molecule transport across membranes (correct)

Explain the primary structure of proteins.

Linear sequence of amino acids that determines the secondary structure.

What connects amino acids together?

A peptide bond.

Why is sickle cell anemia an example of a primary structure mutation?

Glutamate gets mutated to valine, changing the charge. Signup and view all the answers

Explain the secondary structure of proteins.

Arrangement of portions of a polypeptide chain stabilized by hydrogen bonds. Signup and view all the answers

What is an alpha helix?

A helical structure with side chains located on the outside. Signup and view all the answers

What is a beta sheet?

Packing of beta strands. Signup and view all the answers

What does proline do in protein structure?

Disrupts the alpha helix due to having an alpha amino group with no free hydrogen for hydrogen bonding. Signup and view all the answers

What are motifs?

Secondary structures that have characteristic 3D shapes, also called super secondary structures. Signup and view all the answers

Where do super secondary structures work?

In binding small ligands and ions or in protein-DNA interactions. Signup and view all the answers

What is a zinc finger?

A super secondary structure with Zn+2 bound to two cysteine and histidine residues. Signup and view all the answers

Where are zinc fingers found?

In receptors that have a DNA-binding domain interacting with lipid-soluble hormones. Signup and view all the answers

What is a leucine zipper?

A super secondary structure where leucine residues of one alpha helix interdigitate with those of another alpha helix. Signup and view all the answers

Where are leucine zippers found?

In DNA-binding proteins like transcription factors. Signup and view all the answers

What are prions?

Infectious proteins that cause normal neural proteins to change their secondary structure through contact. Signup and view all the answers

What diseases are prions responsible for?

Kuru, mad cow disease, Creutzfeldt-Jakob disease. Signup and view all the answers

Explain the tertiary structure of proteins.

The 3D folded structure of a polypeptide, also called the native conformation. Signup and view all the answers

How are secreted proteins stabilized?

Covalent disulfide bonds. Signup and view all the answers

Explain quaternary structure.

The association of two or more tertiary structures. Signup and view all the answers

What is denaturation?

Loss of native conformation that produces loss of biological activity. Signup and view all the answers

What levels of structure are disrupted by denaturing agents?

Secondary, tertiary, and quaternary structures, but NOT primary structure. Signup and view all the answers

Describe the denaturing agents.

Extreme changes in pH or ionic strength, detergents, high temperature, heavy metals. Signup and view all the answers

What does G6PD deficiency have to do with denaturation?

Increased peroxide in RBC leads to the denaturing of hemoglobin and formation of Heinz bodies. Signup and view all the answers

Study Notes

Major Functions of Proteins

Provide structural support for cells and tissues
Facilitate movement within organisms
Involved in signal transduction processes
Bind to various molecules and ions
Transport substances across cellular membranes
Act as catalysts in biochemical reactions

Primary Structure of Proteins

Defined by the linear sequence of amino acids (AA)
Determines higher order structures including secondary structure
Mutations in the primary structure can lead to functional deficiencies

Peptide Bonds

Form connections between amino acids
Result from a condensation reaction between the amino group of one AA and the carboxyl group of another

Sickle Cell Disease Mutation

Caused by a mutation where glutamate is replaced with valine
Alters the charge of the hemoglobin molecule, impacting its functionality

Secondary Structure of Proteins

Comprises arrangements of the polypeptide chain stabilized primarily by hydrogen bonds
Two main types: alpha helix and beta sheet

Alpha Helix

Features a coiled, helical structure
Side chains of amino acids extend outward from the helix

Beta Sheet

Formed by the packing of beta strands
Characterizes the orientation of adjacent strands, which can be parallel or antiparallel

Role of Proline

Disrupts the formation of alpha helices
Lacks a free hydrogen atom for hydrogen bonding due to its unique structure

Motifs in Protein Structure

Comprise specific arrangements of secondary structures that adopt characteristic 3D shapes
Also referred to as super secondary structures

Function of Super Secondary Structures

Engage in binding small ligands, ions, and interact with DNA

Zinc Finger Structure

A type of super secondary structure containing zinc ions coordinated with cysteine and histidine residues
Important in DNA-binding proteins

Locations of Zinc Fingers

Present in receptors for lipid-soluble hormones that exhibit DNA-binding activity

Leucine Zipper Structure

Another super secondary structure where leucine residues from two alpha helices intertwine
Facilitates protein dimerization

Locations of Leucine Zippers

Found in DNA-binding proteins such as transcription factors

Prions

Infectious proteins that induce structural changes in normal neural proteins
Promote the conversion from alpha helices to beta sheets
Form aggregates that resist degradation through digestion or heat

Diseases Linked to Prions

Associated with conditions like kuru, mad cow disease, and Creutzfeldt-Jakob disease

Tertiary Structure of Proteins

Refers to the complete 3D folded shape of a polypeptide
Comprised of distinct structural and functional domains
Stabilized by interactions between side chains and associations of supersecondary motifs

Stabilization of Secreted Proteins

Achieved through the formation of covalent disulfide bonds

Quaternary Structure of Proteins

Involves the assembly of two or more tertiary structures
Common forms include dimers and tetramers
Stabilized by noncovalent interactions and interchain disulfide bonds

Denaturation of Proteins

Refers to the loss of native conformation leading to a loss of biological activity
Denatured proteins can aggregate due to exposed hydrophobic side chains becoming insoluble

Levels of Structure Affected by Denaturation

Denaturation disrupts secondary, tertiary, and quaternary structures but leaves primary structure intact

Denaturing Agents

Extreme pH or ionic strength changes, detergents, elevated temperatures, and heavy metals contribute to protein denaturation

G6PD Deficiency and Denaturation

Increased peroxide levels in red blood cells can denature hemoglobin, leading to the formation of Heinz bodies due to oxidative stress

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Description

Test your knowledge on the major functions and structures of proteins with these flashcards. Learn about protein functions like structural support, movement, and binding, as well as the primary structure and peptide bonds. Perfect for studying biochemistry concepts related to proteins.