PROTEIN FOLDING
Summary
TLDRThis video explains how proteins are made up of polypeptide chains, composed of 20 different amino acids linked by peptide bonds. It outlines the four levels of protein structure: primary (amino acid sequence), secondary (hydrogen bonds forming alpha helixes and beta sheets), tertiary (3D folding based on polar and nonpolar amino acids), and quaternary (interacting polypeptide chains). The video also discusses protein folding mechanisms and introduces three classes of proteins: globular, fibrous, and membrane proteins. These shapes and solubility characteristics define their biological roles.
Takeaways
- 𧬠Proteins are made of folded polypeptide chains composed of 20 different amino acids, each with unique chemical properties.
- π Amino acids are linked by covalent peptide bonds, forming a repeating polypeptide backbone with distinct side chains.
- π Protein folding results in different conformations, which are the spatial arrangements of atoms without bond breakage.
- π Protein structure is categorized into four levels: primary (amino acid sequence), secondary (hydrogen bonding interactions), tertiary (3D folding), and quaternary (multiple polypeptide chains).
- π Secondary structures include alpha helices and beta sheets, which are formed by hydrogen bonds between peptide bonds.
- π Alpha helices coil like springs, with hydrogen bonds between every 3.6 amino acids, giving the structure polarity with an N-terminus and C-terminus.
- 𧩠Beta sheets form parallel or antiparallel chains with hydrogen bonds between neighboring chains, contributing to the protein's overall structure.
- π Hydrophobic interactions drive protein folding, with nonpolar amino acids gathering inside the protein and polar amino acids forming bonds on the surface with water molecules.
- π¦ Tertiary structure forms as secondary structures interact, with nonpolar amino acids collapsing inward and long-range interactions shaping the final protein structure.
- π¬ Proteins are classified into three categories: globular (spherical and soluble), fibrous (linear and insoluble), and membrane (associated with cell membranes).
Q & A
What are proteins made up of?
-Proteins are made up of folded polypeptide chains composed of 20 different amino acids linked via covalent peptide bonds.
What is the polypeptide backbone?
-The polypeptide backbone is the sequence of atoms repeating to form the peptide bonds in a polypeptide chain.
What makes each amino acid different from the others?
-Each amino acid has a unique sidechain, which can be polar or nonpolar, giving it distinct chemical properties.
What are protein conformations?
-Conformations are the spatial arrangements of atoms in a protein that result from movement without breaking bonds.
What are the four levels of protein structure?
-Protein structure is described in four levels: primary (amino acid sequence), secondary (local interactions like alpha helices and beta sheets), tertiary (3D shape), and quaternary (multiple polypeptide subunits interacting).
How is secondary structure formed?
-Secondary structure is formed by hydrogen bond interactions between adjacent amino acids, leading to structures like alpha helices and beta sheets.
What causes proteins to fold into their tertiary structure?
-The pattern of polar and nonpolar amino acids in a polypeptide chain drives the folding process, with nonpolar amino acids aggregating to avoid water and polar amino acids interacting with the water environment.
What is the difference between parallel and anti-parallel beta sheets?
-Parallel beta sheets are made from neighboring chains running in the same direction, while anti-parallel beta sheets are formed by chains running in opposite directions.
What is hydrophobic collapse during protein folding?
-Hydrophobic collapse is the aggregation of nonpolar amino acids during the early stages of protein folding, reducing their interaction with water and promoting proper protein folding.
What are the three basic classes of proteins, and how do they differ?
-The three basic classes are globular, fibrous, and membrane proteins. Globular proteins are spherical and water-soluble, fibrous proteins have linear structures and provide structural support, and membrane proteins are associated with cell membranes.
Outlines
π¬ Introduction to Protein Structure
Proteins are composed of folded polypeptide chains made up of 20 distinct amino acids, each with unique chemical properties. These amino acids are linked by covalent peptide bonds. The sequence of repeating atoms forming these peptide bonds is called the polypeptide backbone, and the side chains of the amino acids can be either polar or nonpolar. Protein structures can adopt various conformations without breaking bonds, and these structures are classified into four levels: primary, secondary, tertiary, and quaternary. The primary structure is the amino acid sequence, which contains all the information needed for higher-order structures.
π Secondary Structures: Alpha Helices and Beta Sheets
Secondary structures arise from hydrogen bonds between adjacent amino acids. These bonds form two main types of structures: alpha helices and beta pleated sheets. An alpha helix coils like a spring with one turn every 3.6 amino acids, where the NH group forms a hydrogen bond with the C=O group of another peptide one coil away. This gives the polypeptide chain polarity, with one end having a positive charge and the other a negative charge. Beta sheets, on the other hand, can be parallel or antiparallel, depending on the direction of neighboring chains. These sheets are stabilized by inter-strand hydrogen bonds.
𧬠Tertiary Structure: The 3D Shape of Proteins
The tertiary structure of proteins results in a compact, three-dimensional shape. Large proteins often consist of multiple protein domains that fold independently. The structure is influenced by the distribution of polar and nonpolar amino acids in the chain. Nonpolar side chains aggregate in the proteinβs interior to avoid water, while polar side chains interact with the aqueous environment outside. Tertiary structures are critical for the protein's stability and function, as the hydrophobic core helps maintain its overall shape.
π Protein Folding and Final Structure
Protein folding begins with the formation of secondary structures. Next, a hydrophobic collapse occurs, where nonpolar amino acids group together to avoid water. Long-range interactions between secondary structures lead to further folding, potentially passing through intermediate states like the molten globule state. This process is essential for reaching the final functional form of the protein.
𧩠Classes of Proteins: Globular, Fibrous, and Membrane
Proteins are categorized into three main classes based on their shape and solubility: globular, fibrous, and membrane proteins. Globular proteins are spherical, highly soluble in water, and structurally marginally stable, which allows for flexibility and function. Fibrous proteins, on the other hand, have linear, simple structures that provide support and are insoluble. Membrane proteins are associated with cell membranes, playing roles in various cellular functions.
Mindmap
Keywords
π‘Polypeptide
π‘Amino Acids
π‘Peptide Bonds
π‘Secondary Structure
π‘Alpha Helix
π‘Beta Sheet
π‘Tertiary Structure
π‘Hydrophobic Collapse
π‘Quaternary Structure
π‘Protein Folding
Highlights
Proteins are made up of folded polypeptide chains composed of 20 different amino acids with varying chemical properties.
Amino acids are linked via covalent peptide bonds, forming the polypeptide backbone, with side chains giving unique chemical properties.
Protein structure is categorized into four levels: primary, secondary, tertiary, and quaternary.
The primary structure is the sequence of amino acids in the polypeptide chain and determines higher structural orders.
Secondary structure is formed through hydrogen bonds between adjacent amino acids, creating alpha helices and beta pleated sheets.
Tertiary structure results in a more compact, three-dimensional shape, often involving multiple protein domains.
Quaternary structure occurs when proteins consist of two or more interacting polypeptide chains (subunits).
Alpha helices form when the polypeptide chain coils like a spring, with specific hydrogen bonding patterns between peptide bonds.
Beta sheets can be parallel or anti-parallel, formed by neighboring chains running in the same or opposite directions.
Protein folding involves a hydrophobic collapse, where nonpolar amino acids aggregate, minimizing disruption to water molecules.
Polar amino acids tend to face the exterior of the protein, forming hydrogen bonds with surrounding water molecules.
Nonpolar amino acids are typically found in the interior of proteins, helping stabilize the folded structure.
The process of protein folding likely involves intermediate stages, such as a molten globule state.
Proteins are classified into three basic types based on shape and solubility: globular, fibrous, and membrane proteins.
Globular proteins are spherical, highly soluble in water, and marginally stable, facilitating motion and function.
Transcripts
proteins are made up of folded
polypeptide chains which are composed of
20 different amino acids each with
different chemical properties that are
linked to each other via covalent
peptide bonds the sequence of atoms
repeating to form the peptide bonds is
called the polypeptide backbone the
sidechain of each amino acid which is
the part that makes it different from
the other 19 amino acids can be either
polar or nonpolar
the polypeptide chain can fold in many
different ways called confirmations
confirmations are the spatial
arrangement of atoms that can result
from movement of atoms without breaking
of bonds protein structure can be
described in terms of four levels of
organization primary secondary tertiary
and quaternary structure the primary
structure is simply the amino acid
sequence of the polypeptide chain and it
is important to remember that this
sequence contains all the information
necessary for the higher orders of
structure the secondary structure is
formed by hydrogen bond interactions of
adjacent amino acids large numbers of
such local interactions form alpha
helixes and beta pleated sheets the
tertiary structure is a more compact
three-dimensional shape large proteins
often consists of several protein
domains which are distinct structural
units that fold somewhat independently
from one another
quaternary structure is found in those
proteins that have two or more
interacting polypeptide chains which are
then termed subunits
secondary structures include alpha
helixes and beta sheets an alpha helix
occurs where a polypeptide chain coils
like a spring with one turn every 3.6
amino acids in alpha helix ease the NH
of a peptide bond is hydrogen bonded to
the C double bond o of another peptide
bond which is one coil up in the helix
structure note also that all the NH
groups point in one direction towards
the end terminus and all the C double
bond o groups point in the opposite
direction towards the C terminus and
this is what gives the polypeptide chain
polarity the C terminus is partially
positively charged while the end
terminus is partially negatively charged
beta sheets conform parallel chains
which are made from neighboring chains
running in the same direction or anti
parallel chains which are made from a
polypeptide chain that folds back and
forth on itself so that nearby sections
run in opposite directions while
hydrogen bonds in an alpha helix our
interest Rand hydrogen bonds in beta
sheets are inter strand
tertiary structure formation can be
nucleated by the pattern of polar and
nonpolar amino acids in a polypeptide
chain which plays a central role in
determining the proteins final
confirmation this is because hydrophobic
molecules such as the nonpolar side
chains of certain amino acids are
entropically driven together in an
aqueous environment this limits their
disruption of the hydrogen bonding of
surrounding water molecules as a result
nonpolar amino acids tend to be found
predominantly in the interior of
proteins meanwhile polar amino acids
face the outside of the protein forming
hydrogen bonds with one another and with
the water molecules around the protein
those polar amino acids that are on the
inside of the protein bond with one
another or with the polypeptide backbone
it is thought that protein folding
happens roughly along the following
lines secondary structures form first
hydrophobic collapse during which
nonpolar amino acids aggregate happens
next
long-range interactions between
secondary structures cause further
folding to occur throughout this process
there may be one or more intermediate
states such as what has been termed a
molten globule
as a final note there are three basic
classes of proteins which are
distinguished based on shape and
solubility globular fibrous and membrane
proteins globular proteins are spherical
in shape with as little surface area per
volume as possible these proteins are
marginally stable and this marginal
stability facilitates motion which in
turn enables function hydrophilic amino
acids occupy this small surface area
making these proteins highly soluble in
water fibrous amino acids are simple
linear structures which have structural
roles and are insoluble lastly membrane
proteins are associated with cell
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