Biological Molecules PDF

The Molecules of Life What are the four Main Types of Large Biological Molecules?  The Molecules of Life  Given the rich complexity of life on Earth, we might expect organisms to have an huge diversity of molecules  However, the important large molecules of all living things—...

The Molecules of Life What are the four Main Types of Large Biological Molecules?  The Molecules of Life  Given the rich complexity of life on Earth, we might expect organisms to have an huge diversity of molecules  However, the important large molecules of all living things— from bacteria to elephants—fall into just Four main classes:  Carbohydrates  Lipids  Proteins  Nucleic acids  Macromolecules  large molecules composed of smaller molecules  carbohydrates, proteins, and nucleic acids  complex in their structures  polymers, built from monomers  Polymer - is a long molecule  consisting of many similar or identical building blocks linked by covalent bonds  Monomers - The repeating units that serve as the building blocks of a polymer  Synthesis and Breakdown of Polymers  Facilitated by enzymes  Synthesizing a polymer  Dehydration reaction- Monomers are connected by a reaction in which two molecules are covalently bonded to each other, with the loss of a water molecule  Breaking down a polymer  Hydrolysis- Polymers are disassembled to monomers by a process that is essentially the reverse of the dehydration reaction Hydrolysis -means to break using water (from the Greek hydro, water, and lysis, break  Example: digestion Carbohydrates  include both sugars and polymers of sugars  serve as fuel and building material  Examples: starch, cellulose and polymers of sugars  basic components of protoplasmic structures of nucleic acids and nucleotides  serves as immediate source of chemical energy (glucose) in living systems. Biochemical Functions of Carbohydrates: 1. They supply one-half of the total energy requirements of an organism 2. They serve as structural components of organisms Ex: cellulose, chitin  Carbohydrates  Three Major classes ▪ Monosaccarides ▪ Disaccharides ▪ Polysaccharides  Monosaccharides  from the Greek monos, single, and sacchar, sugar  have molecular formulas that are some multiple of the unit CH2O ▪ Glucose, galactose and fructose ▪ The simplest carbohydrates and the building blocks of all other carbohydrates, single sugar molecules  Are the simplest sugars  Can be used for fuel  Can be converted into other organic molecules  Can be combined into polymers  Disaccharides  formed between two monosaccharides by a dehydration reaction.  Double sugars formed by bonding of two simple sugars,  Important as building blocks and cellular fuels Consist of two monosaccharides  Maltose – formed by 2 glucose molecules  Sucrose – formed by linkage of glucose and fructose  Lactose- formed by linkage of glucose and galactose  Example of Disaccharide Synthesis Polysaccharides  are polymers with a few hundred to a few thousand monosaccharides joined by glycosidic linkages. - are long chains of glucose linked together referred to as polymer, with empirical formula: (C6H10O5)n  Are polymers of sugars  Serve many roles in organisms  Building material for structure that protect the cell or the whole organism (cellulose and chitin)  Storage material (glycogen, starch)  Storage Polysaccharides  Starch  a polymer of glucose monomers, as granules within cellular structures known as plastids  the major storage form of glucose in plants  Storage Polysaccharides  Glycogen  Consists of glucose monomers  Is the major storage form of glucose in animals Mitochondria Giycogen granules 0.5 m Glycogen Figure 5.6 (b) Glycogen: an animal polysaccharide  Structural Polysaccharides  Cellulose  Is a polymer of glucose  Major component of cell walls of higher plants  plants produce almost 1014 kg (100 billion tons) of cellulose per year; it is the most abundant organic compound on Earth.  Cellulose is difficult to digest  Cows have microbes in their stomachs to facilitate this process  A cow harbors cellulose-digesting prokaryotes and protists in its stomach. These microbes hydrolyze the cellulose of hay and grass and convert the glucose to other compounds that nourish the cow. Figure 5.9  Structural Polysaccharides  Chitin  the carbohydrate used by arthropods (insects, spiders, crustaceans, and related animals) to build their exoskeletons  Can be used as surgical thread CH2O H H H O OH OH H OH H H NH C O CH3 (a) The structure of the (b) Chitin forms the exoskeleton (c) Chitin is used to make a chitin monomer. of arthropods. This cicada strong and flexible surgical is molting, shedding its old thread that decomposes after Figure 5.10 A–C exoskeleton and emerging the wound or incision heals. in adult form. Lipids  Lipids are a diverse group of hydrophobic molecules  hydrophobic (repel water) Biochemical Functions:  Perform structural and storage functions  Serve as a main source of energy among organisms  Metabolic regulators (ex.: hormones testosterone)  TYPES OF LIPIDS  FATS  PHOSPHOLIPIDS  STEROIDS  WAXES Fats - Are constructed from two types of smaller molecules, a single glycerol and usually three fatty acids - Store large amount of energy ❖ 1 gram of fats store more than twice as much energy as a gram of polysaccharide H O H H H H H H H H H H H H H H H H C OH C C C C C C C C H C C C C C C C C HO H H H H H H H H H H H H H H H H C OH Fatty acid H C OH (palmitic acid) H Glycerol (a) Dehydration reaction in the synthesis of a fat Ester linkage H O H H H H H H H H H H H H H H H H C O C C C C C C C C H C C C C C C C C H H H H H H H H H H H H H H H O H H H H H H H H H H H H H H H H C O C C C C C C C C H C C C C C C C C H H H H H H H H H H H H H H H O H H H H H H H H H H H H H H H H C O C C C C C C C C H C C C C C C C C H H H H H H H H H H H H H H H H Figure 5.11 (b) Fat molecule (triacylglycerol)  Saturated fatty acids – animal fats  Have the maximum number of hydrogen atoms possible  Have no double bonds  At room temperature, the molecules of a saturated fat, such as the fat in butter, are packed closely together, forming a solid. Stearic acid Figure 5.12 (a) Saturated fat and fatty acid Unsaturated fatty acids – plant and fish  Have one or more double bonds  A diet rich in saturated fats is one of several factors that may contribute to the cardiovascular disease known as atherosclerosis Phospholipids  Have only two fatty acids tails  Major component of the cell membrane   The structure of phospholipids  Results in a bilayer arrangement found in cell membranes WATER Hydrophilic head WATER Hydrophobic tail 4  Steroids  Steroids  cholesterol and the vertebrate sex hormones  Cholesterol is a crucial molecule in animals.  common component of animal cell membranes and is also the precursor from which other steroids are synthesized. In vertebrates, cholesterol is synthesized in the liver  A high level of cholesterol in the blood may contribute to atherosclerosis  One steroid, cholesterol  Is found in cell membranes  Is a precursor for some hormones H3C CH3 CH3 CH3 CH3 Figure 5.15 HO  Proteins  Proteins have many structures, resulting in a wide range of functions  Proteins  Have many roles inside the cell  Most complex macromolecules and are made of amino acids They have :  Structural roles (keratin and collagen)  Transport (hemoglobin)  Enzymatic roles (pepsin)  Immunological (antibodies)  Biochemical functions of Proteins Biochemical functions of Proteins (cont.)  Proteins also serve as source of energy  Enzymes  Are a type of protein that acts as a catalyst, speeding up chemical reactions 1 Active site is available for 2 Substrate binds to a molecule of substrate, the enzyme. Substrate reactant on which the enzyme acts. (sucrose) Glucose Enzyme OH (sucrase) H2O Fructose H O 4 Products are released. 3 Substrate is converted Figure 5.16 to products.  Amino Acid Monomers  Amino acids  Are organic molecules possessing both carboxyl and amino groups  Differ in their properties due to differing side chains, called R groups   20 different amino acids make up proteins CH3 CH3 CH3 CH3 CH3 CH CH2 H CH3 CH3 CH2 H3C CH O O O O O H3N+ C C H3N+ C C H3N+ C C H3N+ C C H3N+ C C O– O– O– O– O– H H H H H Glycine (Gly) Alanine (Ala) Valine (Val) Leucine (Leu) Isoleucine (Ile) Nonpolar CH3 CH2 S H2C CH2 NH O CH2 H2N C C CH2 O CH2 CH2 O– O O H H3N+ C C H3N+ C C H3N+ C C O– O– O– H H H Methionine (Met) Phenylalanine (Phe) Tryptophan (Trp) Proline (Pro) Figure 5.17  OH NH2 O NH2 O C OH SH C CH2 Polar OH CH3 CH2 CH CH2 CH2 CH2 O CH2 O O O O O H3N+ C C H3N+ C C H3N+ C C H3N+ C C H3N+ C C H3N+ C C O– O– O– O– O– O– H H H H H H Cysteine Tyrosine Asparagine Glutamine Serine (Ser) Threonine (Thr) (Gln) (Cys) (Tyr) (Asn) Acidic Basic NH3+ NH2 NH+ –O O O– O C C CH2 C NH2+ NH Electrically CH2 CH2 O CH2 CH2 CH2 charged O H3N+ C C CH2 CH2 CH2 H3N+ C C O O– CH2 O– H3N+ C C O CH2 H H O– H H3N+ C C CH2 O O– H H3N+ C C O– H Aspartic acid Glutamic acid Lysine (Lys) Arginine (Arg) Histidine (His) (Asp) (Glu)  Amino Acid Polymers  Amino acids  Are linked by peptide bonds  Repeated over and over, this process yields a polypeptide, a polymer of many amino acids linked by peptide bonds  NUCLEIC ACIDS The amino acid sequence of a polypeptide - is programmed by a discrete unit of inheritance known as a gene. Genes are made of DNA, a nucleic acid made of monomers called nucleotides  NUCLEIC ACIDS  Roles of NA: - store, transmit, and help express hereditary information Two types of nucleic acids: 1. Deoxyribonucleic acid(DNA) 2. Ribonucleic acid (RNA) DNA - provides directions for its own replication - directs RNA synthesis and, through RNA, controls protein synthesis; this entire process is called gene expression -DNA->RNA->protein  NUCLEIC ACIDS Components of NA Macromolecules that exist as polymers called polynucleotides Each polynucleotide consists of monomers called nucleotides Three parts of a nucleotide:  a nitrogen containing (nitrogenous) base  a five-carbon sugar (a pentose)  one or more phosphate groups The portion of a nucleotide without any phosphate groups is called a nucleoside  Two forms:  1. RNA –ribonucleic acid  2. DNA- deoxyribunucleic acid  RNA RNA plays an important role in protein synthesis It differs from DNA in three ways: RNA is single –stranded Nitrogen base called uracil is found  The sugar molecules in RNA are ribose sugars  TYPES OF RNA  Messenger RNA (mRNA)- copies the message from the DNA and brings it to the ribosomes located in the cytoplasm  Ribosomal RNA (rRNA)- is a component of the ribosomes; plays catalytic roles and structural roles in the ribosomes  Transfer RNA (tRNA) - picks up and carries the specific amino acids to the messenger RNA at the ribosomes Main Differences between DNA and RNA DNA RNA 5-carbon sugar - deoxyribose -ribose Organic bases -A,T,C,G -A,U,C, G Strand -double helix -single chain Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings