Enzyme Refolding and Protein Structure

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Questions and Answers

What caused the denatured enzyme to reform its disulfide linkages and spontaneously refold into its native conformation?

Folding into increasingly complex structures

Instructions from the amino acid sequence

Reaction with oxygen from the air (correct)

Chaperonin binding

What is the primary function of chaperone proteins?

To direct the conformation of newly synthesized proteins (correct)

To inhibit the folding of proteins into complex structures

To denature proteins

To provide the correct tertiary structure to proteins

What is the characteristic of protein folding according to Anfinsen's conclusion?

It is determined by the amino acid sequence (correct)

It is determined by the presence of oxygen

It is determined by the type of protein

It is determined by the presence of chaperonins

What is the shape of the chaperonin molecule?

Cylindrical with a cap Signup and view all the answers

What is the role of chaperonins during protein synthesis?

To guide the folding of newly synthesized proteins Signup and view all the answers

What happens to proteins as they are assembled?

They fold gradually into increasingly complex structures Signup and view all the answers

What is the purpose of the cap on the chaperonin molecule?

To bind temporarily with newly synthesized proteins Signup and view all the answers

What is the significance of Anfinsen's experiment?

It revealed that amino acid sequence determines protein structure Signup and view all the answers

What type of molecule is formed when proteins link with lipids?

Lipoproteins Signup and view all the answers

What is the function of glycoproteins?

Functioning as enzymes, antibodies, recognition and receptor molecules, and parts of extracellular supports Signup and view all the answers

What is the main component of nucleic acids?

Nucleotides Signup and view all the answers

What is the function of DNA?

Storing hereditary information Signup and view all the answers

What are the three components of a nucleotide?

Nitrogenous base, sugar, and phosphate group Signup and view all the answers

What is a nucleoside composed of?

Nitrogenous base and sugar Signup and view all the answers

What type of nitrogenous base has one carbon-nitrogen ring?

Pyrimidines Signup and view all the answers

What type of nitrogenous base has two carbon-nitrogen rings?

Purines Signup and view all the answers

What is the name of the triglyceride product formed in the reaction shown?

Glyceryl palmitate Signup and view all the answers

What is the effect of increasing chain length on fatty acids?

They become less water-soluble and more oily Signup and view all the answers

What is characteristic of a saturated fatty acid?

It binds the maximum number of hydrogen atoms Signup and view all the answers

What is the effect of a double bond on the shape of an unsaturated fatty acid?

It creates a kink Signup and view all the answers

What type of fatty acid is typically found in solid animal fats such as butter?

Saturated Signup and view all the answers

What type of groups can accept a 'Hydrogen' ion in water and act as a Base?

Carboxyl and phosphate groups Signup and view all the answers

What is the health effect of consuming unsaturated fats compared to saturated fats?

Unsaturated fats are considered healthier than saturated fats Signup and view all the answers

What is the characteristic of carbons that are linked to four different atoms or functional groups?

They can take either of two fixed positions with respect to other carbons in a chain Signup and view all the answers

What is the commercial process used to convert plant oils into saturated fats?

Hydrogenation Signup and view all the answers

What type of isomers are mirror images of each other?

Stereoisomers Signup and view all the answers

What is the term used to describe the bend in an unsaturated fatty acid molecule?

Kink Signup and view all the answers

Which of the following is an example of structural isomers?

Glucose, an aldehyde and fructose, a ketone Signup and view all the answers

Which type of enzymes recognize the L-stereoisomer of amino acids?

Most of the enzymes that catalyze biochemical reactions involving amino acids Signup and view all the answers

What is the location of the carbonyl group in glucose?

At the end of the carbon chain Signup and view all the answers

What is the term for the 'left' isomer of an amino acid?

L-isomer (L for laevus= left) Signup and view all the answers

Which of the following is an example of an asymmetric carbon?

A carbon linked to four different atoms or functional groups Signup and view all the answers

What is the primary characteristic of the fatty acid chains in phospholipids?

They are typically nonpolar and hydrophobic Signup and view all the answers

What is the function of the polar end in a phospholipid molecule?

It interacts with water molecules Signup and view all the answers

What is the common structural feature of steroids?

A framework of four carbon rings Signup and view all the answers

What is the primary difference between cholesterol and phytosterols?

The cell membrane they are found in Signup and view all the answers

What is the role of the hydrocarbon side chain in sterols?

It increases the nonpolar character of the sterol molecule Signup and view all the answers

What is the polarity of the fatty acid chains in phospholipids?

Nonpolar and hydrophobic Signup and view all the answers

What is the purpose of the kink in the fatty acid chain in phosphatidyl ethanolamine?

It reflects the presence of a double bond at that position Signup and view all the answers

What is the region of the sterol molecule that is slightly polar?

The region with the -OH group Signup and view all the answers

What is the primary function of triglycerides in animals?

To store energy reserves Signup and view all the answers

What is the role of waxes in animals?

To protect skin, hair, or feathers Signup and view all the answers

What is the primary component of cell membranes?

Phospholipids Signup and view all the answers

What is the arrangement of phospholipid molecules in a bilayer?

The polar ends face the surrounding water molecules Signup and view all the answers

What is the purpose of the phosphate group in phospholipids?

To link to another polar group Signup and view all the answers

What is the characteristic of the fatty acid chains in phospholipids?

They are nonpolar and hydrophobic Signup and view all the answers

What is the result of the buildup of plaques in the coronary arteries?

Atherosclerosis Signup and view all the answers

What is the function of the phospholipid bilayer?

To form the structural basis of membranes Signup and view all the answers

What is the primary function of photosynthesis in plants and other organisms?

To convert energy from sunlight into carbon-based compounds Signup and view all the answers

What are the four major classes of organic molecules found in living organisms?

Carbohydrates, lipids, proteins, and nucleic acids Signup and view all the answers

What is the simplest hydrocarbon, consisting of a single carbon atom bonded to four hydrogen atoms?

CH4 Signup and view all the answers

What is the result of chemical evolution on primordial Earth?

The formation of organic molecules Signup and view all the answers

What are functional groups in biological molecules?

Small, reactive groups of atoms that give larger molecules specific chemical properties Signup and view all the answers

Which functional group can donate a 'Hydrogen' ion in water and acts as an acid?

Hydroxyl group Signup and view all the answers

What is the term for the collective symbol representing carbon atoms in functional groups?

R Signup and view all the answers

What is the characteristic of carbon atoms in organic molecules?

They can bond covalently to other atoms Signup and view all the answers

What is the primary function of steroid hormones?

To control development and behavior Signup and view all the answers

What is the difference between estradiol and testosterone?

Estradiol has an —OH and testosterone has an oxygen Signup and view all the answers

Which of the following is an example of a steroid hormone?

Estradiol Signup and view all the answers

What is the effect of the difference between estradiol and testosterone on animals?

It greatly alters sexual structures and behavior Signup and view all the answers

What type of reaction occurs when water components are removed from functional groups?

Dehydration synthesis Signup and view all the answers

What is the function of the —OH group in estradiol?

It is responsible for the differentiation of the sexes Signup and view all the answers

What is the role of the methyl group in testosterone?

It is absent in estradiol Signup and view all the answers

What is the term for a single polymer molecule with a mass of 1,000 daltons or more?

Macromolecule Signup and view all the answers

What is the relationship between estradiol and testosterone?

They are both sex hormones with different functions Signup and view all the answers

What is the general ratio of carbon to hydrogen to oxygen in carbohydrates?

1C:2H:1O Signup and view all the answers

What is the term for the covalent bond linking two monosaccharides?

Glycosidic bond Signup and view all the answers

What is the significance of the structure of estradiol and testosterone?

It greatly affects their function in controlling development and behavior Signup and view all the answers

What is the term for the breakdown of polymers into monomers?

Hydrolysis Signup and view all the answers

What is the term for the type of carbohydrate that contains three to seven carbon atoms?

Monosaccharide Signup and view all the answers

What is the term for the type of carbohydrate that is formed by two monosaccharides?

Disaccharide Signup and view all the answers

What is the term for the type of carbohydrate that contains more than 10 linked monosaccharide units?

Polysaccharide Signup and view all the answers

What type of stereoisomers are all amino acids assembled into proteins?

l-form only Signup and view all the answers

What is the purpose of the disulfide linkage in a protein?

To maintain the protein's conformation Signup and view all the answers

What is the origin of the 'R' group in an amino acid?

The side chain of another amino acid Signup and view all the answers

What is the function of the sulfhydryl group in cysteines?

To form a disulfide linkage Signup and view all the answers

What type of amino acids have a neutral charge at the pH within the cell?

Uncharged polar amino acids Signup and view all the answers

What is the consequence of a reaction between the sulfhydryl groups of two cysteines?

A disulfide linkage is formed Signup and view all the answers

What is the characteristic of the amino acids shown in the diagrams?

They are in the ionic forms Signup and view all the answers

What is the significance of the three-letter and one-letter abbreviations?

They are commonly used for the amino acids Signup and view all the answers

Study Notes

Enzyme Refolding and Chaperonins

Anfinsen discovered that oxygen from the air can react with the OSH groups of denatured enzymes, causing disulfide linkages to reform and the enzyme to spontaneously refold into its native, active conformation.
This led to the conclusion that the information for determining the three-dimensional shape of ribonuclease is in its amino acid sequence.
Chaperonins are guide proteins that bind temporarily with newly synthesized proteins, directing their conformation toward the correct tertiary structure and inhibiting incorrect arrangements.

Isomers

Isomers are molecules with the same chemical formula but different molecular structures.
Carbons that are linked to four different atoms or functional groups are asymmetric and can take either of two fixed positions with respect to other carbons in a chain.
Examples of isomers include:
- Stereoisomers (e.g., glyceraldehyde), which are mirror images of each other.
- Structural isomers (e.g., glucose and fructose), which have the same chemical formula but different arrangements of atoms.

Fatty Acids and Lipids

Fatty acids are typically 14-22 carbons in length and can be saturated or unsaturated.
Saturated fatty acids have single bonds between carbon atoms and are typically found in solid animal fats.
Unsaturated fatty acids have one or more double bonds and are typically found in plant oils.
The kink in the fatty acid chain, introduced by a double bond, affects the fluidity of the molecule at biological temperatures.

Phospholipids

Phospholipids are lipids that contain a phosphate group.
Examples include phosphatidyl ethanolamine, which has a kink in the fatty acid chain due to a double bond.
Phospholipids are often depicted in cell membrane diagrams with a polar end (represented by a sphere) and nonpolar fatty acid chains (represented by zigzag lines).

Steroids

Steroids are lipids with a framework of four carbon rings.
Sterols, the most common steroids, have a single polar OH group linked to one end of the ring framework and a nonpolar hydrocarbon chain at the other end.
Examples of sterols include cholesterol and phytosterols, which are components of animal and plant cell membranes, respectively.

Protein Combinations

Proteins can link with lipids to form lipoproteins, which are part of cell membranes.
Proteins can link with carbohydrates to form glycoproteins, which function as enzymes, antibodies, recognition and receptor molecules, and parts of extracellular supports.
Proteins can link with nucleic acids to form nucleoproteins, which form structures such as chromosomes.

Nucleotides and Nucleic Acids

Nucleic acids are macromolecules assembled from repeating monomers called nucleotides.
Nucleotides consist of three parts: a nitrogenous base, a five-carbon sugar, and one to three phosphate groups.
DNA (deoxyribonucleic acid) stores hereditary information responsible for inherited traits in all eukaryotes and prokaryotes and in a large group of viruses.
RNA (ribonucleic acid) is the hereditary molecule of another large group of viruses and is involved in protein synthesis.

Nucleotide Structure

A nucleotide is composed of a nitrogenous base, a sugar, and one to three phosphate groups.
A nucleoside is composed of a nitrogenous base and a sugar.

Nitrogenous Bases

There are two types of nitrogenous bases: pyrimidines and purines.
Pyrimidines have one carbon-nitrogen ring and include uracil (U), thymine (T), and cytosine (C).
Purines have two carbon-nitrogen rings and include adenine (A) and guanine (G).

Steroid Hormones

Control development, behavior, and internal biochemical processes
Examples include sex hormones that control differentiation of the sexes and sexual behavior
Estradiol (female sex hormone) has an —OH group where testosterone (male sex hormone) has an =O, and testosterone has a methyl group (—CH3) that is absent from estradiol

Organic Molecules

Four major classes: carbohydrates, lipids, proteins, and nucleic acids
Carbon atoms bond covalently to each other and to other atoms in molecules that range in size from a few atoms to thousands or millions of atoms
Hydrocarbons: molecules consisting of carbon linked only to hydrogen atoms

Hydrocarbons

Carbon has four unpaired outer electrons
Simplest hydrocarbon: CH4 (methane), consisting of a single carbon atom bonded to four hydrogen atoms
More complex hydrocarbons involve two or more carbon atoms arranged in a linear unbranched chain, a linear branched chain, or a structure with one or more rings
Single and double bonds are found in linear and ring hydrocarbons; triple bonds only in two-carbon hydrocarbons

Chemical Evolution

Resulted in the first forms of life on Earth after formation of organic molecules
Involved reactions involving inorganic molecules on primordial Earth and conditions on the planet at that time
Stanley Miller and Harold Urey performed a classic set of experiments in 1953 to simulate chemical evolution and formed several complex organic molecules

Functional Groups

Small, reactive groups of atoms that give larger molecules specific chemical properties
Examples: hydroxyl, carbonyl, carboxyl, amino, phosphate, and sulfhydryl groups
Linked by covalent bonds to other atoms in biological molecules, usually carbon atoms

Hydroxyl and Carbonyl Groups

Can donate a "Hydrogen" ion in water, acting as an acid
Carbonyl group: carbon double-bonded to oxygen

Adding and Removing Water

In many reactions involving functional groups, the components of a water molecule (—H and —OH) are removed from or added to the groups as they interact
Dehydration synthesis reaction or condensation reaction: water components are removed
Hydrolysis: water components are added

Macromolecules

Large polymers assembled from subunit molecules (monomers) into a chain by covalent bonds
Polymers are assembled from monomers by dehydration synthesis reactions
Breakdown of polymers into monomers occurs by hydrolysis
Each type of polymeric biological molecule contains one type of monomer

Carbohydrates

Serve many functions
Energy-providing carbohydrates are stored in plant cells as starch, and in animal cells as glycogen
Structural carbohydrates include cellulose, a primary component of plant cell walls
Contain only carbon, hydrogen, and oxygen atoms in a ratio of about 1C:2H:1O (CH2O)
Monosaccharides contain three to seven carbon atoms

Monosaccharides

Occur either as monosaccharides or as polymers of monosaccharide units
Soluble in water and sweet-tasting
Common monosaccharides contain three carbons (trioses), five carbons (pentoses), or six carbons (hexoses)
All monosaccharides can occur in linear form

Disaccharides

Assembled from two monosaccharides covalently joined by a dehydration synthesis reaction
Examples: maltose (glucose + glucose), sucrose (glucose + fructose), and lactose (glucose + galactose)

Triglycerides

Serve as energy reserves in animals
Store more than twice the calories per gram as carbohydrates
Also help make bird feathers waterproof

Phospholipids

Primary lipids of cell membranes
Most common phospholipid has a glycerol backbone linked to two fatty acid chains and a polar phosphate group
Phospholipid bilayer: a film of phospholipids two molecules thick, with polar groups facing the surrounding water molecules at the surfaces and nonpolar, hydrophobic regions in the interior

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Description

This quiz covers the concept of enzyme refolding and the role of amino acid sequence in determining protein structure, as discovered by Anfinsen. It also touches on the process of protein folding and chaperonins.