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BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor CHAPTER 3 The Molecules of Cells Modules 3.11 – 3.20 From PowerPoint® Lectures for Biology: Concepts & Connections Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings PROTEINS 3.11 Proteins are essential to the structures and activities of life • Proteins are involved in – cellular structure – movement – defense – transport – communication • Mammalian hair is composed of structural proteins • Enzymes regulate chemical reactions Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 3.11 Hair color -eumelanin and phaeomelanin Two gene pairs-Four gene pairs?? Phaeomelanin colors hair red. Nored/red Eumelanin- determines the darkness of the hair color. Low brown eumelanin results in blonde hair Higher brown eumelanin results in brown. Brown/blonde High black eumelanin results in black hair Low black eumelanin results in gray hair Black/grey Most noticeable in red-heads, all humans have varying concentrations of phaeomelanin. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Brown/blonde Not Red/red • Phaeomelanin is more chemically stable than black eumelanin. But less chemically stable than brown eumelanin. So it breaks down more slowly when oxidized. Brown-Red-Black (most stable to least stable) • Bleach will cause darker hair to turn reddishbrown during the artificial coloring process. As the phaeomelanin continues to break down, the hair will gradually become orange, later yellow, and then white. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Muscle contraction –actin and myosin http://www.sci.sdsu.edu/movies/a ctin_myosin.html Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings •Enzymes - proteins that catalyze chemical and biochemical reactions within living cell and outside. This group of proteins probably is the biggest and most important group of the proteins. •Hormones - proteins that are responsible for the regulation of many processes in organisms. Hormones are usually quite small and can be classifies as peptides (2-100 aa.) Best known protein hormones are: insulin, growth factors, etc. •Transport proteins - These proteins are transporting or store some other chemical compounds and ions. Some of them are well known: cytochrome C - electron transport; hemoglobin and myoglobin - oxygen transport •Immunoglobulin or Antibodies - proteins that involved into immune response of the organism to neutralize large foreign molecules, which can be a part of an infection. ie. antibodies •Structural proteins - These proteins maintain the structure of other biological components, like cells and tissues. Collagen, elastin, α-keratin, fibrin - these proteins are involved into formation of the whole organism body. •Motor proteins. These proteins can convert chemical energy into mechanical energy. actin and myosin are responsible for muscular motion. •Receptors These proteins are responsible for signal detection and translation into other type of signal. •Signalling proteins - This group of proteins is involved into signaling transduction process. •Storage proteins. These proteins contain energy, which can be released during metabolism processes in the organism. Egg ovalbumin and milk casein are such proteins. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 3.12 Proteins are made from just 20 kinds of amino acids • Proteins are the most structurally and functionally diverse of life’s molecules – Their diversity is based on different arrangements of amino acids – Proteins may be composed of one polypeptide chain or several. – Protein folding of the chain is essential to protein function. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The monomer of a polypeptide is an amino acid. Each amino acid contains: – an amino group – a carboxyl group – an R group, which distinguishes each of the 20 different amino acids Figure 3.12A Amino group Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Carboxyl (acid) group • Each amino acid has specific properties Leucine (Leu) Serine (Ser) HYDROPHOBIC Figure 3.12B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cysteine (Cys) HYDROPHILIC (*) Essential only in certain cases. • An essential amino acid is an amino acid that cannot be synthesized de novo by the organism (usually referring to humans), and therefore must be supplied in the diet. • Eight amino acids are generally regarded as essential for humans: phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, leucine, and lysine • PVT. TIM HALL (histidine and arginine in children ) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 20 amino acids Essential Nonessential Isoleucine Alanine Leucine Asparagine Lysine Aspartate Methionine Cysteine* Phenylalanine Glutamate Threonine Glutamine* Tryptophan Glycine* Valine Proline* Serine* Tyrosine* Arginine* Histidine* Amino acids can be linked by peptide bonds to form polypeptides. • Cells link amino acids together by dehydration synthesis • The bonds between amino acid monomers are called peptide bonds Carboxyl group Amino group PEPTIDE BOND Dehydration synthesis Amino acid Amino acid Figure 3.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Dipeptide 3.14 Overview: A protein’s specific shape determines its function • A protein, such as lysozyme, consists of polypeptide chains folded into a unique shape – The shape determines the protein’s function – A protein loses its specific function when its polypeptides unravel. Milk curdles and egg white solidifies when their proteins are unraveled. Mad Cow Disease is caused by a malformed protein. Figure 3.14A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 3.14B 3.15 A protein’s primary structure is its amino acid sequence 3.16 Secondary structure is polypeptide coiling or folding produced by hydrogen bonding Primary structure Amino acid Secondary structure Hydrogen bond Pleated sheet Alpha helix Figure 3.15, 16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 3.17 Tertiary structure is the overall shape of a polypeptide and due to R group interactions 3.18 Quaternary structure is the relationship among multiple polypeptides of a protein Tertiary structure Polypeptide (single subunit of transthyretin) Quaternary structure Transthyretin, with four identical polypeptide subunits. Transthyretin carries thyroid hormone through the blood. Figure 3.17, 18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 3.19 Talking About Science: Linus Pauling contributed to our understanding of the chemistry of life • Pauling made important contributions to our understanding of protein structure and function. He is often considered one of the founders of molecular biology. Figure 3.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings NUCLEIC ACIDS 3.20 Nucleic acids are information-rich polymers of nucleotides • Nucleic acids such and DNA and RNA serve as the blueprints for proteins • They ultimately control the life of a cell Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The monomers of nucleic acids are nucleotides – Each nucleotide is composed of a sugar, phosphate, and nitrogenous base Nitrogenous base (A) Phosphate group Figure 3.20A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Sugar • DNA has four kinds of bases, A, T, C, and G Thymine (T) Cytosine (C) Pyrimidines Adenine (A) Guanine (G) Purines Figure 10.2B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Note the designation of the Carbons as 1-5. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings DNA and RNA are polymers of nucleotides • DNA is a nucleic acid, made of long chains of nucleotides Phosphate group Nitrogenous base Sugar Phosphate group Nitrogenous base (A, G, C, or T) Nucleotide Thymine (T) Sugar (deoxyribose) DNA nucleotide Polynucleotide Sugar-phosphate backbone Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10.2A • DNA consists of two polynucleotides twisted around each other in a double helix. The sugar is deoxyribose. The bases are adenine, thymine, guanine, and cytosine. – The sequence of the four kinds of nitrogenous bases in DNA carries genetic information Base pair Nitrogenous base (A) Figure 3.20C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings DNA is Antiparallel Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings RNA is single stranded and the sugar is ribose. The bases are adenine , uracil, guanine and cytosine. DNA RNA Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The Bases of RNA Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • In most organisms, stretches of a DNA molecule, called genes, program the amino acid sequences of proteins. Retroviruses use RNA as their genetic material. The Dogma is not always correct. The Central Dogma. Dogma (the plural is either dogmata or dogmas, Greek δόγμα, plural δόγματα) is the established belief or doctrine held by a religion, ideology or any kind of organization, thought to be authoritative and not to be disputed or doubted. Wiki – DNA information is transcribed into RNA, a single-stranded nucleic acid – RNA is then translated into the primary structure of proteins Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings