1、1.5.1 The Chemical Elements of Life 1.5.2 Many Important Biomolecules Are Polymers 1.5.3 The Energetics of Life 1.5.4 Biochemistry and Evolution 1.5.5 The Cell Is the Basic Unit of Life 1.5 Basic Phenomena of living systems The elemental composition of living matter differs markedly from the relativ
2、e abundance of elements in the earths. Only six nonmetallic elements- carbon, Hydrogen, oxygen, nitrogen, phosphorus, and sulfuraccount for more than 97% of the weight of most organisms. Water is a major component of cells and accounts for the high percentage of oxygen. 1.5.1 The Chemical Elements o
3、f Life A total of 29 different elements are commonly found in living organisms.These include five ions that are essential in all species: Ca+, K+, Na+, Mg+ and Cl-. The most important elements. Biomolecules Are Carbon Compounds. Biochemical reactions involve specific chemical bonds and functional gr
4、oupsester, ether, amide, phosphate ester and phosphoanhydride linkages. The major precursors for the formation of biomolecules are water, carbon dioxide, and three inorganic nitrogen compounds ammonium (NH4+), nitrate (NO3-), and dinitrogen (N2). Some functional groups and linkages of biomolecules L
5、inkages Examples （肾上腺素）（肾上腺素） Macromolecules (biopolymers) are composed of building blocks (monomers) Proteins-amino acids Nucleic acids-nucleotides Polysaccharides-sugars Lipids-fatty acids, glycerol and choline etc. 1.5.2 Many Important Biomolecules Are Polymers ( biochemistry identity ) A topolog
6、ical model of the monosaccharide transporter IgG Biomolecules Have Characteristic Three- Dimensional Structure Covalent bonds hold atoms together so that molecules are formed. In contrast, weak chemical forces or noncovalent bonds are intramolecular or intermolecular attractions between atoms. Weak
7、forces maintain biological structure and determine biomolecular interactions Hydrogen bonds, Van der Waals forces, Ionic interactions, Hydrophobic interactions Weak Forces This principle of structural complementarity is the very essence of biomolecular recognition. Biological systems from the macrom
8、olecular level to the cellular level operate via specific molecular recognition and interactions mechanisms based on structural complementarity: a protein recognizes its specific metabolite, a strand of DNA recognizes its complementary strand, sperm recognize an egg. 1.5.3 The Energetics of Life ( M
9、etabolism ) Photosynthesis is one of the key biochemical processes that is essential for life, even though many species, including animals,benefit only indirectly. Energy Flow Living systems are actively engaged in energy transformations Food pyramid Carnivores Herbivores Photosynthesis A prairie fa
10、lcon acquires nutrients by consuming a smaller bird. ATP and NADPH, two biochemically important energy-rich compounds. Thermodynamic principle also apply to biochemistry. The spontaneity of a reaction depends on the overall free-energy change(G),which is expressed as: G= H-TS When G0, the reaction r
11、equires external energy to proceed; When G=0, the reaction is at equilibrium. The rate of a reaction depends on the acivation energy The rates of enzyme-catalyzed reactions can be up to 1017 times greater than the rates of the corresponding uncatalyzed reactions. Metabolic Regulation Is Achieved by
12、Controlling the Activity of Enzymes Thousands of reactions mediated by an equal number of enzymes are occurring at any given instant within the cell. Metabolism has many branch points, cycles, and interconnections. This metabolic regulation is achieved through controls on enzyme activity so that the
13、 rates of cellular reactions are appropriate to cellular requirements. Orderliness: A glance at a metabolic pathway map. All cells on Earth appear to have evolved from a common ancestry that existed more than 3 billion years ago. The evidence for includes the presence in all living organisms of comm
14、on biochemical building blocks, the same general patterns of metabolism, and a common genetic code. 1.5.4 Biochemistry and Evolution Living systems have a remarkable capacity for self-replication.So biological reproduction occurs with near-perfect fidelity . In the DNA double helix, two complementar
15、y polynucleotide chains running in opposite directions can pair through hydrogen bonding between their nitrogenous bases. Their complementary nucleotide sequences give rise to structural complementarity. Diverse living organisms 1.5.5 The Cell Is the Basic Unit of Life ( Structure multilevel ) Proka
16、ryotic cells Cells Eukaryotic cells Despite their many differences, cells of all kinds share certain structural features. All cells have a nucleus or nucleoid, a plasma membrane, and cytoplasm. （支原体）（支原体） 1. Prokaryotes Each prokaryotic cell is surrounded by a plasma membrane. The cell has no define
17、d membrane- bound nucleus and subcellular organelles. They can be divided into two separate groups: eubacteria（真细菌）（真细菌） archaebacteria（古细菌）（古细菌） E. coli is (a) gram-negative and (b) a prokaryote. These designations are based on (a) the presence of the outer membrane that does not allow gram stain t
18、o bind and (b) the absence of a nucleus. Cell wall structure of Gram-negative bacteria 2.Eukaryote cell organization Plasma membrane Nucleus Endoplasmic reticulum Golgi apparatus Mitochondria Chloroplasts Lysosomes Peroxisomes Cytosol Plant cell wall Plant cell vacuole Eukaryotic cell (animal) The p
19、lasma membrane surrounds the cell, separating it from the external environment. It is a selectively permeable barrier. It is also involved in receiving information. The nucleus stores the cells genetic information as DNA in chromosomes. Eukaryotic chromosome Golgi apparatus is the sorting and packag
20、ing center of the cell. The lumen is the interior of the Golgi sacs. Vesicles bud off from the ends of the sacs. Golgi apparatus receives membrane vesicles from the RER, further modifies the proteins within them, and then packages the modified proteins in other vesicles which eventually fuse with th
21、e plasma membrane or other subcellular organelles. Mitochondria are the power factory of aerobic eukaryotic cell. Mitochondria have an inner and an outer membrane. The inner membrane is folded to form cristae. Enclosed by the inner membrane is the matrix. The inner membrane is the site of oxidative
22、phosphorylation. Eukaryotic cell (plant) Chloroplasts convert solar energy into chemical energy. Chloroplasts are surrounded by a double membrane and have an internal membrane system of thylakoid vesicles. The thylakoid vesicles contain chlorophyll and are the site of photosynthesis. Lysosomes, foun
23、d only in animal cells, are spherical vesicles bounded by a single membrane bilayer. They have an acidic internal pH (pH 4-5), maintained by proteins in the membrane that pump in H+ ions. Within the lysosomes are acid hydrolases; enzymes involve in the degradation of macromolecules, including those
24、internalized by endocytosis. Lysosome Peroxisomes contain enzymes involved in the breakdown of amino acid and fatty acid, a byproduct of which is hydrogen peroxide (H2O2). The cytosol is the soluble part of the cytoplasm where a large number of metabolic reactions take place. Within the cytosol is t
25、he cytoskeleton, a network of fibers that maintain the shape of the cell. Plant cell wall Most cells of higher plants have a cell wall outside the plasma membrane, which serves as a rigid, protective shell. The cell wall is made up of the polysacchride cellulose and other carbohydrate polymers. Plan
26、t cell wall Plant cell vacuole The membrane-bound vacuole is used to store nutrients and waste products, has an acidic pH and, due to the influx of water, create turgor pressure inside the cell as it pushes out against the cell wall. Plant cell vacule The Cytoskeleton A protein scaffold is required
27、for support, internal organization and movement of a cell Actin filaments form ropelike threads Microtubules are rigid fibers packed into bundles - Serve as an internal skeleton - Form the mitotic spindle during mitosis - Form movement structures (e.g. cilia, flagella) Fluorescently labeled: (a) Act
28、in filaments (b) Microtubules Viruses Are Supramolecular Assemblies Acting as Cell Parasites Virions, nonliving particles(outside of the host cells) Bacteriophages, simply phages, specific for the becteria. A gallery of viruses HIV HIV leaving an infected T lymphocyte of the immune system SARS :Coro
29、navirus Molecular surface model of the canine parvovirus Human poliovirus (type 2), a picornavirus (a) a bacterial virus, bacteriophage T4; (b) an animal virus, adenovirus (inset at greater magnification); (c) a plant virus, tobacco mosaic virus. Filamentous phage fd Bacteriophage f fX174 The End of Chapter 1The End of Chapter 1 Thank You For Attention!Thank You For Attention!
