LS1a F08 Lect 7 Lecture Notesr-3

LS1a F08 Lect 7 Lecture Notesr-3 - A polymer is built of...

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A polymer is built of repeating monomer units O O P HO OH O N N N N NH2 HO Biological (Natural) Polymers nucleotide monomer nucleic acid polymer O O N N N N N O P O O O O P O O O O N N O H O CH3 H H O P O O O P O O O O N N O H O CH3 DNA is the information carrier of life; along with RNA it provides instructions to make proteins Sugars are important in energy storage and have other functions that are not well understood sugar monomer polysaccharide O HO HO OH OH OH O HO O OH OH O HO O OH OH O HO OH OH Many of the molecules found in the cell are polymers, which are large molecules comprised of repeating monomer units. In a few weeks, you will learn about the structure and function of nucleic acid polymers of DNA and RNA. These polymers are comprised of only four different building blocks each and they are highly negatively charged. DNA has a single structure -- the double helix -- and a single function that is explained by its structure. Its function is to transmit information and it does so in two ways -- through replication (DNA copying itself, which is important in the generation of new cells) and through transcription (DNA making RNA, which is important for protein synthesis). RNA is single stranded and can fold into many different kinds of structures, and it plays several different kinds of roles in the cell. For example, messenger RNA encodes proteins, amino-acid linked tRNA molecules help decode messenger RNA, and ribosomal RNA forms part of the ribosomal machine that is involved in decoding messenger RNA. Cells also make polymers of sugars. These polymers are called oligosaccharides or polysaccharides depending on how many sugars they contain. On this slide we have only mentioned one role for sugars -- the storage of energy -- but they play many other roles. For example, oligosaccharides on cell surfaces bind to circulating proteins and to other cell surfaces, so they play roles in communication between cells. As you will see in a few lectures, they also act as receptors for viruses, bacteria, and bacterial toxins that have evolved to use cell surface carbohydrates to help gain entry into cells. Specifically, you will learn more about how HIV uses a glycoprotein called gp120 to enter T-cells and macrophages. We aren t going to talk very much about oligosaccharides and polysaccharides in this course, in part because their roles -- apart from energy storage -- really aren t that well understood yet.
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H 2 N O HO OH N H O H N N H O O HO OH protein polymer amino acid monomer Proteins: Amino acid polymers • Proteins have the most diverse shapes of the biological polymers • Proteins are comprised of a wider variety of monomers and has a more varied charge distribution • The different shapes combined with different properties allow proteins to have an incredible range of different functions Proteins are the most diverse biological polymers. They are made of a wider variety of monomer units than nucleic acid polymers -- twenty
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LS1a F08 Lect 7 Lecture Notesr-3 - A polymer is built of...

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