Lecture 3: The Nature of Life PDF

Lecture 3: The Nature of Life - Characteristics of Life - Chemical Properties Unifying themes in the study of life… ▪ Hierarchy of organization ▪ Cell as the basic unit of life ▪ Interaction of organisms with their environment ▪ Unity in Diversity ▪ DNA as the...

Lecture 3: The Nature of Life - Characteristics of Life - Chemical Properties Unifying themes in the study of life… ▪ Hierarchy of organization ▪ Cell as the basic unit of life ▪ Interaction of organisms with their environment ▪ Unity in Diversity ▪ DNA as the genetic material ▪ Structure vs. function ▪ Scientific process ▪ Evolution: Core theme 2 Emergent properties and processes… ▪ Composition ▪ Reproduction ▪ Growth and Development ▪ Energy utilization ▪ Response to environment ▪ Evolutionary Adaptation ▪ Movement ▪ Complexity of Organization 3 Composition and Order ▪ Structural units : CELLS ▪ Hierarchy of Organization ▪ Each builds up from the level below it ▪ Genetic Material: - DNA (Deoxyribonucleic Acid)  Producing one’s own kind Offspring always Reproduction resemble the parents Laws of inheritance (Genetics) Growth and Development Increase in Variations due Production of mass (matter), to Genetics and new cells volume Environment Energy Utilization Metabolism – collective product of all the biochemical reactions Metabolic activities (production of new cytoplasm, repair of damage, normal cell maintenance) Anabolic (Energy – producing); Catabolic (Energy-utilizing) Respiration, Photosynthesis, Digestion  Stimuli – any perceived change Response to stimuli is a major Response to characteristic of living things Environment Plants have different nature of response than animals - callose formation after wounding  Adaptation Means to tolerate and survive Generations of natural selection Plants – altitude, soil and climate adaptations Achieve homoestasis (steady-state) Movement ▪ plant movements, when compared with animals, are slow and imperceptible and are mostly related to growth phenomena. ▪ plant movements are obvious only when demonstrated experimentally or when shown by time-lapse photography ▪ Cyclosis, or cytoplasmic streaming – counter/clockwise Complexity of Organization ▪ Order and Hierarchy ▪ Molecules – Cells – Tissues – Organs – Systems ▪ More than 1 trillion molecules in a cell ▪ Molecules organized into compartments, membranes, structures Complicated and Highly Organized HIERARCHICAL ORGANIZATION OF BIOLOGICAL STRUCTURES supramol organis macrom organ tissue cell organelle ecular m assembly olecule Understanding plants ▪ Plants grow, develop and respond to its environment based on chemistry and physics ▪ Plants have means of storing and using information ▪ Plants reproduce passing information to its descendants ▪ Information can change ▪ Plants must survive in their environment 13 Understanding plants ▪ Plants are highly integrated organisms ▪ Plants are temporary results of genes and environmental effects ▪ Plants do not have decision-making capacity 14 Chemical Basis of Life Elements : Units of Matter ▪ Atoms – Molecules – Elements ▪ 98 naturally occurring ▪ Elements combined with other elements form Compounds ▪ Bonds attract and hold atoms together. Chemical Components of Cells 96% of cytoplasm and its living substance of cells included structures is 3% consists of consists of cytoplasm composed of the phosphorus, potassium, and the structures within elements carbon, and sulfur it hydrogen, oxygen, and nitrogen 1% includes calcium, iron, magnesium, sodium, Organic compounds - Inorganic compounds - chlorine, copper, have “backbones” of contain no carbon atoms manganese, cobalt, zinc, carbon atoms are called inorganic. and minute quantities of other elements Monomers and Polymers ▪ Monomers – basic units making up the polymer ▪ Polymers or Macromolecules formed by the removal of H+ and OH+ ▪ Dehydration synthesis - extracts water from compounds and uses energy; controlled by enzymes ▪ Hydrolysis – breaking down of polymers with the attachment of H+ and OH+ , energy released Carbohydrates serve as fuel and building material ▪ Carbohydrates include sugars and the polymers of sugars ▪ The simplest carbohydrates are monosaccharides, or single sugars ▪ Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Sugars ▪ Monosaccharides have molecular formulas that are usually multiples of CH2O ▪ Glucose (C6H12O6) is the most common monosaccharide ▪ Monosaccharides are classified by ▪ The location of the carbonyl group (as aldose or ketose) ▪ The number of carbons in the carbon skeleton ▪ A disaccharide is formed when a dehydration reaction joins two monosaccharides Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Sucrose consists of an α-D-glucose and a β -D-fructose molecule joined by an α,β-1,2-glycosidic bond o the glycosidic bond in sucrose is between carbon 1 of glucose and carbon 2 of fructose. Sucrose, a disaccharide obtained from sugar beets and sugar cane, contains glucose and fructose. Sucrose consists of an α-D-glucose and a β -D-fructose molecule joined by an α,β-1,2-glycosidic bond o the glycosidic bond in sucrose is between carbon 1 of glucose and carbon 2 of fructose. Sucrose, a disaccharide obtained from sugar beets and sugar cane, contains glucose and fructose. Fig. 5-3 Trioses (C3H6O3) Pentoses (C5H10O5) Hexoses (C6H12O6) Glyceraldehyde Ribose Glucose Galactose Dihydroxyacetone Ribulose Fructose Polysaccharides Polysaccharides, the polymers of sugars, have storage and structural roles The structure and function of a polysaccharide are determined by its sugar monomers Starches ▪ the main carbohydrate reserve of plants ▪ polysaccharides that usually consist of several hundred to several thousand glucose units. ▪ When many glucose molecules bond together to become a starch molecule, each glucose gives up a molecule of water. ▪ Formula for starch is (C6H10O5)n ; n indicates the number of units of glucose in the starch molecule. ▪ In order for a starch molecule to become available as an energy source in cells, it has to be hydrolyzed Fig. 5-6 Chloroplast Starch Mitochondria Glycogen granules 0.5 µm 1 µm Amylose Glycogen Amylopectin (a) Starch: a plant polysaccharide (b) Glycogen: an animal polysaccharide  the principal starch crops are potatoes, are major sources wheat, rice, and of carbohydrates corn in temperate for human areas and cassava, consumption sweet potatoes, and taro in tropical areas Starch and human consumption Cellulose: Structural Polysaccharide ▪ the chief structural polymer in plant cell walls ▪ consisting of 3,000 to 10,000 unbranched chains of glucose molecules. ▪ very widespread in nature, its glucose units are bonded together differently from those of starch ▪ most animals digest it much less readily than they do starch. ▪ Organisms that do digest cellulose (protozoans living in termite guts, caterpillars, and some fungi) produce special enzymes capable of facilitating the breakdown of bonds Cellulose, with (1→4)-glycosidic linkages, can adopt a fully extended conformation with alternating 180° flips of the glucose units. The hydrogen bonding inherent in such extended structures is responsible for the great strength of tree trunks and other cellulose-based materials. Cellulose acetates are produced by the action of acetic anhydride on cellulose in the presence of sulfuric acid and can be spun into a variety of fabrics with particular properties. Referred to simply as acetates, they have a silky appearance, a luxuriously soft feel, and a deep luster and are used in dresses, lingerie, linings, and blouses. Fig. 5-8 Cell walls Cellulose microfibrils in a plant cell wall Microfibril 10 µm 0.5 µm Cellulose molecules b Glucose monomer Lipids Monomers : Fatty acids + Glycerol fatty or oily substances that are mostly insoluble in water because they do not have polar regions store about twice as much energy as similar amounts of carbohydrate play an important role in the longer term energy reserves and structural components of cells. like carbohydrates, lipid molecules contain carbon, hydrogen, and oxygen, but there is proportionately much less oxygen present. Lipids: Fats and Oils Fatty acids vary in Saturated fatty acids fats, which are solid at length (number of have the maximum Unsaturated fatty room temperature and carbons) and in the number of hydrogen acids have one or oils, which are liquid. number and locations atoms possible and no more double bonds of double bonds double bonds Fig. 5-12 Structural formula of a saturated fat molecule Stearic acid, a saturated fatty acid (a) Saturated fat Structural formula of an unsaturated fat molecule Oleic acid, an unsaturated fatty acid cis double bond causes (b) Unsaturated fat bending Examples of Lipids ▪ Fats made from saturated fatty acids are called saturated fats, and are solid at room temperature ▪ Most animal fats are saturated ▪ Fats made from unsaturated fatty acids are called unsaturated fats or oils, and are liquid at room temperature ▪ Plant fats and fish fats are usually unsaturated Fatty acid compositions of some dietary lipids. The structures of some typical fatty acids. Note that most natural fatty acids contain an even number of carbon atoms and that the double bonds are nearly always cis and rarely conjugated. saturated fatty acid - long carbon chain is like an alkane - only single carbon–carbon bonds monounsaturated fatty acid - the long carbon chain has one double bond - properties similar to those of an alkene polyunsaturated fatty acid - there are at least two carbon–carbon double bonds. Lipids: Waxes ▪ very long-chain fatty acids bonded to a very long-chain alcohol other than glycerol. ▪ found on the surfaces of plant leaves and stems ▪ usually embedded in a matrix of cutin or suberin, which are also lipid polymers that are insoluble in water. ▪ combinations of wax and cutin or wax and suberin function in waterproofing, reduction of water loss, and protection against microorganisms and small insects Phospholipids ▪ In a phospholipid, two fatty acids and a phosphate group are attached to glycerol ▪ The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head ▪ Important components of all membranes found in living organisms Fig. 5-14 Hydrophilic WATER head Hydrophobic WATER tail Proteins, Polypeptides and Amino Acids ▪ monomer: Amino Acids ▪ cells of living organisms contain from several hundred to many thousands of different kinds of proteins, ▪ second only to cellulose in making up the dry weight of plant cells. ▪ consist of carbon, hydrogen, oxygen, and nitrogen atoms, and sometimes also sulfur atoms. ▪ regulate chemical reactions in cells ; comprise the bulk of protoplasm apart from water. ▪ usually very large and consist of one or more polypeptide chains with, in some instances, simple sugars or other smaller molecules attached Polypeptides ▪ chains of amino acids. ▪ 20 different kinds of amino acids, and from 50 to 50,00 or more of them are present in various combinations in each protein molecule ▪ Amino acids are formed by peptide bonds Amino Acids ▪ Plants can synthesize amino acids they need from raw materials in their cells, ▪ Animals must supplement from plant sources some amino acids they need (Essential Amino Acids) , they can manufacture only a few amino acids themselves. Fig. 5-UN1 carbon Amino Carboxyl group group Enzymes ▪ Enzymes are a type of protein that acts as a catalyst to speed up chemical reactions ▪ Enzymes can perform their functions repeatedly, functioning as workhorses that carry out the processes of life Fig. 5-16 Substrate (sucrose) Glucose Enzyme (sucrase) OH H2 O Fructose H O Storage Proteins ▪ plant food-storage organs, such as potato tubers and onion bulbs, store small amounts of proteins in addition to large amounts of carbohydrates. ▪ Seeds contain proportionately larger amounts of proteins in addition to carbohydrates and are very important sources of nutrition ▪ One example of an important protein source in human and animal diets is wheat gluten (to which, incidentally, some humans become allergic); consists of a complex of more than a dozen different proteins. Storage Proteins ▪ Seed’s proteins get used during germination and its subsequent development into a seedling. ▪ Some legume seeds may contain more than 40% protein, but legumes are deficient in certain amino acids (e.g., methionine), and a human diet based on beans needs to be balanced with other storage proteins (e.g., those found in unpolished rice) ▪ Some seed proteins, such as those of jequirity beans (Abrus precatorius—used in India to induce abortions and as a contraceptive), are highly poisonous. Nucleic Acids ▪ The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene ▪ Genes are made of DNA, a nucleic acid ▪ There are two types of nucleic acids: ▪ Deoxyribonucleic acid (DNA) ▪ Ribonucleic acid (RNA) Nucleic Acids ▪ Nucleic acids are polymers called polynucleotides ▪ Each polynucleotide is made of monomers called nucleotides ▪ Each nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group ▪ The portion of a nucleotide without the phosphate group is called a nucleoside Fig. 5-27 5 end Nitrogenous bases Pyrimidines 5 C 3 C Nucleoside Nitrogenous base Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA) Purines Phosphate group Sugar 5 C (pentose) Adenine (A) Guanine (G) 3 C (b) Nucleotide Sugars 3 end (a) Polynucleotide, or nucleic acid Deoxyribose (in DNA) Ribose (in RNA) (c) Nucleoside components: sugars DNA ▪ DNA provides directions for its own replication ▪ DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis ▪ Protein synthesis occurs in ribosomes Fig. 5-26-3 DNA 1 Synthesis of mRNA in the nucleus mRNA NUCLEUS CYTOPLASM mRNA 2 Movement of mRNA into cytoplasm Ribosome via nuclear pore 3 Synthesis of protein Amino Polypeptide acids Genetic Material of Heredity and Evolution ▪ The linear sequences of nucleotides in DNA molecules are passed from parents to offspring ▪ Two closely related species are more similar in DNA than are more distantly related species ▪ Molecular biology can be used to assess evolutionary kinship