清华大学：《生物化学》课程PPT教学课件（英文版）Histones vs Nonhistone

Chromatin o Compaction of the large DNA molecules and the control of gene expression in eukaryotes are achieved by having the dna complexed with a set of special proteins to form the protein-DNA complex called chromatin. The DNA-binding proteins of chromatin are histones, and nonhistone

•Compaction of the large DNA molecules and the control of gene expression in eukaryotes are achieved by having the DNA complexed with a set of special proteins to form the protein–DNA complex called chromatin. The DNA-binding proteins of chromatin are histones, and nonhistones. Chromatin

Histones vs nonhistone Histones are small, very basic proteins rich in lysine and arginine. The histones are the basic building blocks of chromatin structure. The nucleoids of prokaryotic cells also have proteins associated with dna, but these proteins are quite different from the histones and do not seem to form a comparable chromatin structure Nonhistone chromosomal proteins- The histones are accompanied by a much more diverse group of DNA binding proteins called nonhistone chromosomal proteins

Histones vs Nonhistone • Histones are small, very basic proteins rich in lysine and arginine. The histones are the basic building blocks of chromatin structure. The nucleoids of prokaryotic cells also have proteins associated with DNA, but these proteins are quite different from the histones and do not seem to form a comparable chromatin structure. • Nonhistone chromosomal proteins - The histones are accompanied by a much more diverse group of DNA￾binding proteins called nonhistone chromosomal proteins

Chromosomes Bacterial chromosome- Almost all of the dna of a typical prokaryote like E coli is contained in a single, large, supercoiled circular DNA molecule, with a minor fraction present in small plasmids Eukaryotic chromosomes- The typical eukaryotic cell genome is divided into several or many chromosomes, each of which contains a single, very large, linear DNa molecule. These DNa molecules are commonly of the order of 10 to 10 bp in length. The number of eukaryotic chromosomes ranges from l(in an Australian ant)to 190(in a species of butterfly). Ploidy- Some eukaryotic cells are highly polyploid, carrying many copies of each chromosome

Bacterial chromosome - Almost all of the DNA of a typical prokaryote like E. coli is contained in a single, large, supercoiled circular DNA molecule, with a minor fraction present in small plasmids. Eukaryotic chromosomes - The typical eukaryotic cell's genome is divided into several or many chromosomes, each of which contains a single, very large, linear DNA molecule. These DNA molecules are commonly of the order of 107 to 109 bp in length. The number of eukaryotic chromosomes ranges from 1 (in an Australian ant) to 190 (in a species of butterfly). Ploidy - Some eukaryotic cells are highly polyploid, carrying many copies of each chromosome. Chromosomes

Eukaryotic chromosome Eukaryotic chromosome DNA A eukaryotic chromosome set Gene locus Chromosome

Eukaryotic chromosome

Considerations in eukaryotic chromosomes The enormous amount of dna in eukaryotic cells poses the following obstacles to cells. 1. Compaction- The length of the total DNA content of a human cell is nearly 3 meters, yet it must be packed into a nucleus about 10-5 m in diameter 2. Selective transcription-In a typical differentiated eukaryotic cell, only a small fraction of the DNA (5%-10%o)is ever transcribed. Many genes that do undergo transcription do so only in certain cell lines in particular tissues, and then often only under special circumstances. To maintain and regulate such complex programs of selective transcription, the accessibility of the dna to RNa Polymerases must be under strict control

Considerations in eukaryotic chromosomes The enormous amount of DNA in eukaryotic cells poses the following obstacles to cells: 1. Compaction - The length of the total DNA content of a human cell is nearly 3 meters, yet it must be packed into a nucleus about 10-5 m in diameter. 2. Selective transcription - In a typical differentiated eukaryotic cell, only a small fraction of the DNA (5%-10%) is ever transcribed. Many genes that do undergo transcription do so only in certain cell lines in particular tissues, and then often only under special circumstances. To maintain and regulate such complex programs of selective transcription, the accessibility of the DNA to RNA Polymerases must be under strict control

Biological Molecules(m): Polysaccharides Polysaccharide name Monomeric Unit Glycogen D-Glucose Cellulose D-Glucose Chitin N-Acetyl-D-glucosamine Amylopectin D-Glucose Amylose D-Glucose

Biological Molecules(II): Polysaccharides Polysaccharide Name Monomeric Unit Glycogen D-Glucose Cellulose D-Glucose Chitin N-Acetyl-D-glucosamine Amylopectin D-Glucose Amylose D-Glucose

Glucose Glucose is a Six carbon sugar which can provide a rapid source of aTP energy via glycolysis. Glucose is stored in polymer form by plants(starch) and animals (glycogen). Plants also have cellulose, which is not used to store glucose, but rather provides structural integrity to the cells. Glucose has an anomeric carbon, which can exist in the a and p configurations. Glucose can exist in both the d and l forms(though the D form predominates biologically

Glucose ◼ Glucose is a six carbon sugar which can provide a rapid source of ATP energy via glycolysis. Glucose is stored in polymer form by plants (starch) and animals (glycogen). Plants also have cellulose, which is not used to store glucose, but rather provides structural integrity to the cells. Glucose has an anomeric carbon, which can exist in the a and b configurations.Glucose can exist in both the D and L forms (though the D form predominates biologically)

Structure of glucose CH2 o、H OH OH OH OH Glucose

Structure of Glucose

P polysaccharides Polysaccharides containing a single sugar, such as glucose, are referred to as glucans. Others, which contain only mannose, are called mannans. Still others containing only xylose, are called xylans Another group of polysaccharides of importance is the glycosaminoglycans. These are heteropolysaccharides containing either N-acetylgalactosamine or N- acetylglucosamine as one of their monomeric units. Examples include chondroitin sulfates and keratan sulfates of connective tissue, dermatan sulfates of skin and yaluronic acid. All of these are acidic, through the presence of either sulfate or carboxylate groups

Polysaccharides • Polysaccharides containing a single sugar, such as glucose, are referred to as glucans. Others, which contain only mannose, are called mannans. Still others, containing only xylose, are called xylans. • Another group of polysaccharides of importance is the glycosaminoglycans. These are heteropolysaccharides containing either N-acetylgalactosamine or N￾acetylglucosamine as one of their monomeric units. Examples include chondroitin sulfates and keratan sulfates of connective tissue, dermatan sulfates of skin, and yaluronic acid. All of these are acidic, through the presence of either sulfate or carboxylate groups

Example of polymer: Cellulose CHOH CHOH CHOH CHOH Chain extend for OH H OH OH H OHHOHHOHH OH Guose res due ncelubse chen Cellubse, a pol mer of B-D-gluoase B -o-gLcose, the monomer

Example of polymer: Cellulose