Chapter 10: Introduction to Metabolism - Enzymes and Energy, Chapter 15. Here, we'll take a look at four major types of RNA: messenger RNA (mRNA), ribosomal RNA (rRNA), transfer RNA (tRNA), and regulatory RNAs. How Are They Connected?" The tightly packaged region is known as heterochromatin, and the less dense region is known as euchromatin. The sugar molecule has a central position in the nucleotide, with the base attached to one of its carbons and the phosphate group (or groups) attached to another. Which of the following is not part of nucleotide structure? Direct link to tyersome's post Both. The difference between the sugars is the presence of the hydroxyl group on the ribose's second carbon and hydrogen on the deoxyribose's second carbon. cytosine, phosphate group, ribose 2-deoxyribose, phosphate group, uracil 2-deoxyribose, phosphate group, thymine guanine, phosphate group, ribose cytidine, phosphate group, ribose adenine, phosphate group, ribose. "Nucleotide. Our website uses cookies to improve your experience. When a polynucleotide forms, the incoming nucleotide's 5 phosphate attaches to the 3 hydroxyl group at the end of the growing chain. The 2' carbon bears a hydroxyl group in ribose, but no hydroxyl (just hydrogen) in deoxyribose. Watson and Crick were able to piece together the puzzle of the DNA molecule on the basis of Franklins data because Crick had also studied X- ray diffraction (Figure 5.4). In DNA, adenine bonds with thymine. Direct link to Raian Ailanazar's post What is the role of U(ura, Posted 3 years ago. The base is attached to the ribose's 1 position, and the phosphate is attached to the 5 position. The nitrogenous bases found in DNA are adenine (A), thymine (T), Direct link to StephYakir87's post The first part is true, T, Posted 7 years ago. Special codons even specify to the machinery where to stop and start the process. What are 3 components of the DNA nucleotide? Nucleotides not only make up the building blocks of life, but also form many different molecules that function to make life possible. 2003-2023 Chegg Inc. All rights reserved. cytosine (C) and guanine (G). Sugar ThoughtCo, Apr. Nucleotide structure is simple, but the structure they can form together is complex. They are bases because they contain an amino group that has the potential of binding an extra hydrogen, and thus decreasing the hydrogen ion concentration in its environment, making it more basic. (, Pentose Sugar and nitrogenous base structure that is twisted along its entire length (Figure 6). Another protein, DNA ligase, finished the job by creating the phosphodiester bond between the sugar molecule of one base and the phosphate group of the next. researchers require special imaging technology, such as the X-ray diffraction Introduction Nucleic acids, and DNA in particular, are key macromolecules for the continuity of life. Although DNA is often found as a single-stranded The RNA sequence is complementary to the sequence of the DNA (except U replaces T). In the cytoplasm, the mRNA interacts with ribosomes and other cellular machinery (Figure 3.34). The difference is between DNA and RNA. Uracil is also a pyrimidine. Would it be possible for DNA and RNA to use other sugars aside from Deoxyribose and Ribose? Purines have a double ring structure, and pyrimidines have a single ring. (Scientists call this an antiparallel orientation and is important to DNA replication and in many nucleic acid interactions.). Even though the RNA is single stranded, most RNA types show extensive intramolecular base pairing between complementary sequences, creating a predictable three-dimensional structure essential for their function. One of the ways proteins are able to repair damaged DNA is that they can bind to uneven spots within the structure. Which are the 3 components of RNA nucleotide? Types of bonds in a RNA Adenine forms two bonds with thymine in DNA or two bonds with uracil in RNA. microscope. The nitrogenous base attaches to base 1, and the phosphate group attaches to base 5. Each nucleotide is made up of three components: a nitrogenous base, a pentose (five-carbon) sugar, and a phosphate group (Figure 5.2).Each nitrogenous base in a nucleotide is attached to a sugar molecule, which is attached to one or more phosphate groups. A nucleotide consists of a sugar molecule (either ribose in RNA or deoxyribose in DNA) attached to a phosphate group and a nitrogen-containing base. The base pairs are stabilized by hydrogen bonds; adenine and thymine form two hydrogen bonds and cytosine and guanine form three hydrogen bonds. This makes the cytosine-guanine bond slightly stronger than the thymine-adenine bond, which only forms two hydrogen bonds. DNA stores genetic information in We recommend using a Every base pair in the double helix is separated from the next base pair by 0.34 nm. They are also found in coenzymes like NAD and NADP, which come from ADP; these molecules are used in many chemical reactions that play roles in metabolism. Do you want to learn more about nucleotide base-pairing? DNA is found in nearly all living cells. used Franklin's images, along with their own evidence for the double-stranded polynucleotide, it assumes its most stable form when double stranded. Direct link to tyersome's post Within a gene *usually* o, Posted 7 years ago. stimulate the chemical and physical processes it calls for. Around the same time, OpenStax is part of Rice University, which is a 501(c)(3) nonprofit. Which organic compound contains three elements? - Quora Can we see pic of female inserting a tampon? Note that because the two polynucleotides that make up https://www.thoughtco.com/what-are-the-parts-of-nucleotide-606385 (accessed July 5, 2023). It is impossible for researchers to see double-stranded DNA Organisms composed of cells that contain nuclei are Each DNA strand is composed of nucleotidesunits made up of a sugar (deoxyribose), a phosphate group, and a nitrogenous base. The first, mRNA, carries the message from DNA, which controls all of the cellular activities in a cell. 100% (4 ratings) for this solution. Nucleotide - Definition, Structure (3 Parts), Examples & Function Regular exercise, a balanced diet, adequate sleep, and limiting smoking, alcohol, and drug use are essential for physical and mental health. A series of three nucleotides within the DNA is known as a codon, and directs the proteins within the cell to attach a specific protein to a series specified by the rest of the DNA. In eukaryotic cells, DNA forms a complex with histone proteins to form chromatin, the substance of eukaryotic chromosomes. For instance, one human alone consists of approximately 100 trillion cells. By the end of this section, you will be able to do the following: Nucleic acids are the most important macromolecules for the continuity of life. DNA and RNA are comprised of monomers that scientists call nucleotides. The purines and pyrimidines form bonds with one another. If the sequence of one strand is 5-AATTGGCC-3, the complementary strand would have the sequence 3-TTAACCGG-5. organisms composed of cells that lack nuclei are classified as prokaryotes. Some chemistry sources use the term nucleotide only for the single-phosphate case, but in molecular biology, the broader definition is generally accepted. Post any question and get expert help quickly. Retrieved from https://www.thoughtco.com/what-are-the-parts-of-nucleotide-606385. 5, 2023, thoughtco.com/what-are-the-parts-of-nucleotide-606385. During formation of DNA strand, it loses two of The primary difference between the forms is the direction that the helix spirals. Thus, these are the triangle that contributes to the state of complete health. Once an mRNA has been produced, it will associate with a ribosome, a molecular machine that specializes in assembling proteins out of amino acids. They also learn how to derive . Here's the answer for both DNA and RNA. In the 1950s, Francis Crick and James Watson worked together to determine the structure of DNA at the University of Cambridge, England. What was the date of sameul de champlians marriage? They also have functions related to cell signaling, metabolism, and enzyme reactions. Sugar 3 parts of a Nucleotide. What three components make up a nucleotide? - eNotes.com Could there ever be an instance where there are more than just five kinds of nitrogenous bases (Adenine, Thymine, Guanine, Cytocine and Uracil)? Deoxyribose nucleic acid, or DNA, is a polymeric molecule that consists of a linear chain of individual subunits called nucleotides. Adenine and guanine are. We will first discuss the main components of a nucleotide before elaborating on its structure and how it bonds together to form nucleic acids. Jan 9, 2023 OpenStax. When two DNA sequences match in this way, such that they can stick to each other in an antiparallel fashion and form a helix, they are said to be. If the sequence of one strand is AATTGGCC, the complementary strand would have the sequence TTAACCGG. to make a composite picture called a karyotype This arrangement makes an alternating chain of deoxyribose sugar and phosphate groups in the DNA polymer, a structure known as the sugar-phosphate backbone. Nucleic acids are macromolecules made up of monomers called nucleotides. Compare the relative sizes of the double helix, histones, and chromosomes. Direct link to Ivana - Science trainee's post This one is the best expl, Posted 5 years ago. Adenine and guanine are classified as purines and have two carbon-nitrogen rings. If the DNA strand has a sequence 5-AATTGCGC-3, the sequence of the complementary RNA is 3-UUAACGCG-5. This article has been posted to your Facebook page via Scitable LearnCast. these phosphate groups, so that only one phosphate is incorporated into a Because of the sizes and functional groups of the bases, base pairing is highly specific: A can only pair with T, and G can only pair with C, as shown below. DNA bears the hereditary information thats passed on from parents to children, providing instructions for how (and when) to make the many proteins needed to build and maintain functioning cells, tissues, and organisms. The ribosome uses the information in the mRNA to make a protein of a specific sequence, reading out the mRNAs nucleotides in groups of three (called. A nucleotide is a building block of DNA. At the metaphase stage, the chromosomes are at their most compact, are approximately 700 nm in width, and are found in association with scaffold proteins. Component. smaller molecules are arranged that differs among individuals. Which nucleotide is not found in DNA? The other type of nucleic acid, RNA, is mostly involved in protein synthesis. For example, a certain purine can only pair with a certain pyrimidine. The phosphate group is attached to the 5' carbon. components are the nucleobases of a nucleotide. How do mRNA and tRNA communicate with eachother during the formation of the proteins? Each codon codes for a single amino acid. This is the proper and typical arrangement. What are the three (3) components of a nucleotide? A Brief History of Genetics: Defining Experiments in Genetics, Unit 5.2. Name the type of bond that holds nucleotides together & identify it in a nucleic acid structure. all organisms. Nucleotides also are used for cell signaling and to transport energy throughout cells. Learn more about how Pressbooks supports open publishing practices. Adenine is a purine, which is one of two families of nitrogenous bases. In a cell, a nucleotide about to be added to the end of a polynucleotide chain will bear a series of three phosphate groups. The two strands are held together by Also, AT/G, Posted 7 years ago. A nucleotide has three major components: a nitrogenous base, a pentose sugar, and a phosphate group. DNA polymers are strings of nucleotides. Guanine form three bonds with cytosine in both DNA and RNA. The part of a nucleotide that can be removed without breaking DNA is a nucleotide polymer, or polynucleotide. Identify three possible components of a DNA nucleotide. They form by dehydration synthesis reactions (Figure 5.3). Component Definition and Examples - Biology Online Dictionary What is the role of U(uracil).Why we can't use uracil in DNA or use T(thymine) in RNA, what's the difference between them? in the 3' to 5' direction (Figure 4). Only certain types of base pairing occur. mRNA, rRNA, tRNA, miRNA, and siRNA. joined by glycosidic bond forms nucleoside, Carbon 1 of sugar and nitrogen 1 of pyrimidine Now Between The mRNA is read in sets of three bases known as codons. DNA translation, as it is known, converts the information from DNA into the language of proteins. What are the 3 components of DNA nucleotide? Image of a ribosome (made of proteins and rRNA) bound to an mRNA, with tRNAs bringing amino acids to be added to the growing chain. Watson and Crick correctly proposed that DNA is made up of two strands that are twisted around each other to form a right-handed helix. 2. Cytosine, thymine, and uracil are classified as pyrimidines, which have a single carbon-nitrogen ring (Figure 5.2). It consists of three main components- base, sugar and phosphate. What years of time was the separate but equal doctrine the law of the land in the US? To figure out the other strand, we simply need to know the complementary base pairing order. A simple dehydration reaction like the other linkages connecting monomers in macromolecules does not form the phosphodiester linkage. sugar-phosphate chain runs in the 5' to 3' direction, whereas the other's runs Biologydictionary.net, October 30, 2016. https://biologydictionary.net/nucleotide/. A Nucleotide are molecules that when combined make the A sugar, a base, and a polypeptide A phosphate, a base, and a polypeptide A sugar, a phosphate, and a peptide A sugar, a phosphate and a base This problem has been solved! ThoughtCo. But what, exactly, is DNA? A free nucleotide may have one, two, or three phosphate groups attached as a chain to the 5-carbon of the sugar. Opposite to the 5' side of the sugar molecule is the 3' side (dark gray), which has a free hydroxyl group attached (not shown). What is the relationship between Commerce and economics? It is a three-part structure that is composed of a nitrogenous base, a "pentose" sugar, and a phosphate group. Nucleotides are the building blocks of the DNA and RNA used as genetic material. The last part of nucleotide structure, the phosphate group, is probably familiar from another important molecule ATP. During replication and DNA synthesis, it pairs . Watson and Crick ultimately The nitrogenous bases are stacked in the interior, like the steps of a ladder. Figure 8:In eukaryotic chromatin, double-stranded DNA (gray) is wrapped around histone proteins (red). Sugar and phosphate forms the We often write out only one strand of DNA, but DNA is usually double-stranded. Some of the most fundamental properties of DNA emerge from the features of its four basic building blocks, called nucleotides. Direct link to Matt B's post Entirely true. What effects accomplishments did Francisco have. Phosphate, nitrogenous base and pentose sugar. offspring during the process of reproduction. Ribonucleic acid, or RNA, is mainly involved in the process of protein synthesis under the direction of DNA. The overall molecule has a shape somewhat like an L. Some types of non-coding RNAs (RNAs that do not encode proteins) help regulate the expression of other genes. The euchromatin usually contains genes that are transcribed, with DNA packaged around nucleosomes but not further compacted. In prokaryotes, the DNA is not enclosed in a nucleus. However, in RNA, the base T is absent and U is present instead. from one another. Glycosidic bond Pentose Sugar and nitrogenous base joined by glycosidic bond forms nucleoside Glycosidic bond (nitrogen-carbon linkage) between C1 of sugar-N9 of purine bases (C1-N9 glycosidic bond) (Adenine and Guanine) A. Like adenine, guanine is a purine nucleotide; it has a double ring. This is the Central Dogma of Life, which holds true for all organisms; however, exceptions to the rule occur in connection with viral infections. or arranged in opposite orientations. At these lengths, the four-letter nucleotide alphabet can encode nearly unlimited information. A. A-G B. C-G C. T-U D. U-C, 3. There are two groups of bases: The order of nucleotides along DNA polymers encodes the genetic information carried by DNA. Direct link to Katherine's post Why do some nitrogenous b, Posted 6 years ago. The protein will cut out one nucleotide, and replace it with another. Table 3.2 summarizes DNA and RNA features. In RNA, the base uracil (U) takes the place of thymine. They are bases because they contain an amino group that has the potential of binding an extra hydrogen. Only certain types of base pairing are allowed. characteristics, thanks to another set of molecules that "read" the pattern and ribose in RNA), a phosphate and a nitrogenous base. In RNA, the pentose sugar is ribose, which has a hydroxyl group attached to the 2 carbon. We can and do synt. It bonds with cytosine in both DNA and RNA. Each strand of DNA is a polynucleotide composed of units called nucleotides. Ribonucleic acid, or RNA, is mainly involved in protein synthesis. Carbon residues in the pentose are numbered 1 through 5 (the prime distinguishes these residues from those in the base, which are numbered without using a prime notation). Nitrogen-containing base. This missing hydroxyl group plays a role in the three-dimensional structure and chemical stability of DNA polymers. For the same reason that the sugar-phosphate backbone is so strong, the bonds in ATP are as well. When combined with special enzymes which have formed to release the energy, it can be transferred to other reactions and molecules. This means that one strand's In a double stranded DNA molecule, the two strands run antiparallel to one another so that one strand runs 5 to 3 and the other 3 to 5. Its formation involves removing two phosphate groups. New York: W. H. Freeman. Step 1 of 5. A nucleotide is an organic molecule that is the building block of DNA and RNA. Solved QUESTION 2 A DNA nucleotide has three components - Chegg Check out this, Posted 8 years ago. They also serve a number of function outside of genetic information storage, as messengers and energy moving molecules. It is the base pairing between the tRNA and mRNA that allows for the correct amino acid to insert itself in the polypeptide chain. Generally DNA has three chemical components 1. In molecular biology shorthand, the nitrogenous bases are often just referred to by their one-letter symbols, A, T, G, C, and U. DNA contains A, T, G, and C, while RNA contains A, U, G, and C (that is, U is swapped in for T). Pauling had discovered the secondary structure of proteins using X-ray crystallography. Recognize how nucleotides and nucleic acids are related. DNA Structure - Visible Body standard light microscope, as long as the chromosomes are in their most Process of transferring data to a storage medium? The carbon atoms of the sugar molecule are numbered as 1, 2, 3, 4, and 5 (1 is read as one prime). How can you tell is a firm is incorporated? Compare and contrast the two types of nucleic acids. How DNA carries this information, and how it is put into action by cells and organisms, is complex, fascinating, and fairly mind-blowing, and well explore it in more detail in the section on, In eukaryotes, such as plants and animals, DNA is found in the, In eukaryotes, DNA is typically broken up into a number of very long, linear pieces called, Many genes encode protein products, meaning that they specify the sequence of amino acids used to build a particular protein. "Nucleotide." are not subject to the Creative Commons license and may not be reproduced without the prior and express written Robustness (usability and dependability of all components) Completeness of the ActivitySheet web page For more information about the peer review process itself, . The cell's entire genetic content is its genome, and the study of genomes is genomics. How Are They Connected? Nucleotides: Definition, Component & Structure | StudySmarter Our mission is to improve educational access and learning for everyone. So how does this fit inside a small bacterial cell? A consequence of the structure of nucleotides is that a polynucleotide chain has, As new nucleotides are added to a strand of DNA or RNA, the strand grows at its 3 end, with the 5 phosphate of an incoming nucleotide attaching to the hydroxyl group at the 3 end of the chain. Nucleic acids are information molecules that serve as blueprints for the proteins that are made by cells. Direct link to Ivana - Science trainee's post Yes, miRNA regulates prot, Posted 3 years ago. They are also the hereditary material in cells, as reproducing cells pass the blueprints on to their offspring. Lets look at each part of a nucleotide in turn. Nucleotides also are used for cell signaling and to transport energy throughout cells. The answer to this question lies in the process known as DNA packaging, which is the phenomenon of fitting DNA into dense compact forms (Figure 7). Where is the tallest General Electric Building located? Three components comprise each nucleotide: a nitrogenous base, a pentose (five-carbon) sugar, and a phosphate group (Figure 3.31). Scientists classify adenine and guanine as purines. 1. Which one of the following is NOT a component of a DNA nucleotide? Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License . In eukaryotic cells but not in prokaryotes, DNA forms a complex with histone proteins to form chromatin, the substance of eukaryotic chromosomes. It carries the correct amino acid to the protein synthesis site. Components and Structure of a Nucleotide. Nitrogenous Base: They comprise pyrimidine or purine base. molecule contains five carbon atoms arranged in the shape of a ring, and each chromosomes as a result of the staining process are unique to each pair of The second portion of the nucleotide is the sugar. During DNA replication, each strand copies itself, resulting in a daughter DNA double helix containing one parental DNA strand and a newly synthesized strand. The entire genetic content of a cell is known as its genome. Staining makes the chromosomes easier to see under the You'll get a detailed solution from a subject matter expert that helps you learn core concepts. These A ribonucleotide in the RNA chain contains ribose (the pentose sugar), one of the four nitrogenous bases (A, U, G, and C), and the phosphate group. This illustration introduces nucleotide and the terminology used to describe them. Hydrogen bonding between complementary bases holds DNA strands together in a double helix of antiparallel strands. Adenosine triphosphate, or ATP, is the energy molecule that most life on Earth relies upon to store and transfer energy between reactions. They then form a bond, which becomes the sugar-phosphate backbone. Each nucleotide in DNA contains one of four possible nitrogenous bases: adenine (A), guanine (G) cytosine (C), and thymine (T). The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo Each nucleotide in DNA contains one of four possible nitrogenous bases: adenine (A), guanine (G) cytosine (C), and thymine (T). 0 0 Similar questions Identify the three components [ (i), (ii) and (iii)] of ATP molecule shown in the given figure. The histones are evolutionarily conserved proteins that are rich in basic amino acids and form an octamer. See Answer Question: What are the three components of a DNA nucleotide? Like DNA, RNA is made of nucleotides linked by phosphodiester bonds. Yes, all 46 chromosomes are found in each and every cell i.e in every cell there are 46 chromosomes (23 from each parents). DNA and RNA structure and function. This is known as the Central Dogma of Molecular Biology. The three components that create a DNA nucleotide are a You may be asked to name the three parts of a nucleotide and explain how they are connected or bonded to each other. These chromosomes are made up of thousands of shorter segments of DNA, called genes. specific sequence of A, T, C, and G nucleotides within an organism's DNA is Adenine forms hydrogen bonds (or base pairs) with thymine, and guanine base pairs with cytosine. What are the three components of a single nucleotide? The mRNA sits in between the two subunits. Each nitrogenous base in a nucleotide is attached to a sugar molecule, which is attached to one or more phosphate groups. The Central Dogma: Genes to Traits, 2. The bases used in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T). As an Amazon Associate we earn from qualifying purchases. This is known as the base complementary rule. A nucleotide consists of base, sugar, and phosphate group. So, in a chain of DNA or RNA, each nucleotide has just one phosphate group. the chain is the thymine for DNA and the uracil for RNA. Most cells are incredibly small. So do our bodies make these nitrogenous bases, or do we get them from consuming food? Biology Dictionary. During DNA packaging, long pieces of double-stranded DNA are tightly consent of Rice University. DNA dictates the structure of mRNA in a process scientists call transcription, and RNA dictates the protein's structure in a process scientists call translation. When this DNA is collected and purified, the result is a whitish, sticky It stores instructions for making other large molecules, called proteins. Each nucleotide contains three components: The sugar carbon atoms are numbered 1 to 5. In DNA, the 5-carbon sugar is deoxyribose, while in RNA, the 5-carbon sugar is ribose. An evolutionist would say it's all down to chance. DNA is the genetic material in all living organisms, ranging from single-celled bacteria to multicellular mammals. the area surrounding this carbon atom is known as the. Therefore Many genes contain the information to make protein products. In class, I prefer calling the pentose sugar . mRNA is a chain of nucleotides (A, U, C, and G, not T since this is RNA). 5-carbon sugar B. Phosphate group C. Phospholipid, 2. Figure 2:The four nitrogenous bases that compose DNA nucleotides are shown in bright colors: adenine (A, green), thymine (T, red), cytosine (C, orange), and guanine (G, blue). The phosphate residue attaches to the hydroxyl group of the 5 carbon of one sugar and the hydroxyl group of the 3 carbon of the sugar of the next nucleotide, which forms a 53 phosphodiester linkage. Which three components contribute to the state of complete health? Each nucleotide within has a specific structure which enables this formation. carbon in the ring is referred to by a number followed by the prime symbol ('). When they pass on, the strands of genetic material comes back together, driven by the attraction between the opposing nucleotide bases. Regulation of Gene Expression. At the most basic level, DNA is wrapped around proteins known as histones to form structures called nucleosomes. Russian DNA polymers can be tens of millions of nucleotides long. What is the word that goes with a public officer of a town or township responsible for keeping the peace? cytosine, phosphate group, ribose 2-deoxyribose, phosphate group, uracil 2-deoxyribose, phosphate group, thymine guanine, phosphate group, ribose cytidine, phosphate group, ribose adenine, phosphate group, ribose. phosphate group that contains one negatively charged Sugar: A nucleotide comprises a pentose sugar. When nucleotides connect to form DNA or RNA, the phosphate of one nucleotide attaches via a phosphodiester bond to the 3-carbon of the sugar of the next nucleotide, forming the sugar-phosphate backbone of the nucleic acid. DNA dictates the sequence of mRNA in a process known as transcription, and RNA dictates the structure of protein in a process known as translation. Other types of RNAlike rRNA, tRNA, and microRNAare involved in protein synthesis and its regulation. This molecule consists of two strands which wrap around each other, forming hydrogen bonds in the middle of the structure for support. Figure 10:This karyotype depicts all 23 pairs of chromosomes in a human cell, including the sex-determining X and Y chromosomes that together make up the twenty-third set (lower right). Nucleic acids are long, linear chains of nucleotides. chemical process that attaches the chromosomes to a glass slide and stains or This even formation causes a twist in the structure, and is smooth if there are no errors. A nucleotide in an RNA chain will contain ribose (the five-carbon sugar), one of the four nitrogenous bases (A, U, G, or C), and a phosphate group. Eukaryotes, whose chromosomes each consist of a linear DNA molecule, employ a different type of packing strategy to fit their DNA inside the nucleus (Figure 5.7). It is a molecularly inert form for the passing on of genes without having a massive effect upon the rest of the body - and so the active form is the sticky stuff of RNA and these determine how the proteins are folded together.