Presentation on theme: "Chapter 13.Chemicals of life No molecule in a living organism is a permanent resident. Within 7 years, most of the molecules in a human body have been."— Presentation transcript:
Chapter 13.Chemicals of life No molecule in a living organism is a permanent resident. Within 7 years, most of the molecules in a human body have been replaced by new one! Individual? Decided completely by the genetic code? No! An individual’s identity is continually re-established each and every moment.
13.1 Biomolecules are produced and utilized in cells Plasma membrane: 细胞 膜 Cell wall: 细胞壁 Cell nucleus ：细胞核 Cytoplasm: 细胞质 Organelles: 细胞器 Carbohydrate: 碳水化合 物 Lipid: 脂类 Protein: 蛋白质 Nucleic acid: 核酸 Plant cell Animal cell
13.2 Carbohydrates give structure and energy Carbohydrates are molecules of carbon, hydrogen and oxygen produced by plant through photosysthesis ( 光 合作用 ). Saccharide: 糖类 Glucose: 葡萄糖 Fructose: 果糖 Glucose Fructose Honey
The polysaccharides of the human diet are made only of glucose. These polysaccharides include starch ( 淀粉 ), glycogen （糖原） and cellulose （纤维素）, which differ from one another in how the glucose units are chained together. Amylose: 直链淀粉 20% Amylopectin: 支链淀粉 80%
Cellulose is consisted of β–glucose and has a straight conformation. Cellulose is by far the most abundant organic compound on earth. But most animals, including humans, are not able to break cellulose down to glycose.
Fats are used for energy and insulation A fat is any biomolecule formed from the reaction of a glycerol molecule, attached to three fatty acid molecules. Fatty acid can be saturated or unsaturated. Fats are used to reserve energy. 1 gram of fat contains about 9 calories of energy, while a gram of carbohydrate and protein contains only 4 calories of energy. Fats are also used to insulate us from cold. 13.3 Lipids are insoluble in water
Saturated fat and unsaturated fat The molecules of saturated fats can pack together, leading to high melting points. The molecules of unsaturated fats can not pack together, leading to low melting points. stearic acid ， m.p.69 ℃ oleic acid ， m.p.13 ℃
Fats from animals and plants are mixture of different fat molecules Table 13.1 degree of unsaturation in some common fats Fat Percentage of total fatty acid content SaturatedMonounsaturatedpolyunsaturated Coconut9361 Palm57367 Lard444610 Cottonseed262252 peanut21430 Olive157312 Corn142957 Soybean142462 Sunflower114970 Safflower101476 Canola oil65836
13.4 Proteins are polymers of amino acids ( 氨基酸 ) 20 amino acids differ from one another by the chemical identity of their side groups.
Amino acids are linked through peptide bonds ( 肽键 ). A group of amino acids linked together through peptide bonds is called peptide. Peptides containing more than ten amino acids are generally called polypeptides.
The proteins in hair and fingernails contain a lot of disulfide bonds
Many proteins consist of two or more polypeptide chains. 血红蛋白 The proteins can be denatured with the change in conditions.
Enzymes are biological catalysts Figure 13.25 Upon binding to the receptor site on the enzyme sucrase, the substrate sucrose is split into its two monosac- charide units, glucose and fructose.
13.5 Nucleic acids code for proteins Our bodies are built of proteins. Our bodies are able to assemble amino acids in just the right order to build proteins that have highly functional structures. A nucleotide ( 核苷 ) consists of a phosphate ( 磷酯 ), a ribose sugar ( 核 糖 ), and a nitrogenous base ( 碱基 ). A nucleic acid is a polymer made up to nucleotide monomers.
Two types of nucleic acids: deoxyribonucleic acid ( 脱氧核糖核酸 ) and ribonucleic acid ( 核糖核 酸 ). Deoxyribonucleic acids are the primary source of genetic information and are found in the cell nucleus. Ribonucleic acids occur mostly outside the cell nucleus in the cytoplasm, where they piece together amino acids to make proteins.
DNA is the template of life Gregor Mendel’s work rose the idea of heredity. The unit containing the heritable information is called genes. In 1900s, genes have been related to chromosomes ( 染色 体 ), which consist of DNA and proteins.
In 1953, James Watson and Francis Crick proposed the double helix structure of DNA. The most critical point of double helix model is the hydrogen bonding between guanine and cytosine, and also between adenine and thymine.
One gene codes for one polypeptide Gene controls the protein’s amino acid sequence. Each gene codes for the synthesis of a particular protein. The number of human gene is 30000-100000. Each chromosome contains 1000-2000 genes. Each DNA molecule contains about 3.1 billion base pairs. Genes make up only about 20% of a DNA molecule.
RNA is largely responsible for protein synthesis The manufacturing of proteins involves two processes: transcription ( 转录 ) and translation ( 转译 ). These steps are mediated by the three forms of RNA: messenger RNA ( 信使 RNA ， mRNA), ribosomal RNA ( 核糖体 RNA ， rRNA) and transfer RNA ( 转移 RNA ， tRNA).
13.6 Vitamins are organic, minerals are inorganic Lipid-soluble vitamins and water-soluble vitamins Lipid-soluble vitamins can be stored in body for long time, but not for children. Over-dose of vitamins A and D are harmful. Vitamins B and C are washed away by water.
Table 13.2 Some Vitamins Needed by the Human Body VitaminFunctionDeficiency syndrome Lipid-soluble Vitamin A (retinol)Precursor to rhodopsin, a chemical used for vision; assists in inhibiting bacterial and viral infections Night blindness Vitamin D (calciferol)Helps incorporate calcium into body Weak bones Vitamin E (tocopherol)Inhibits oxidation of polyunsaturated fats; free radical scavenger; Diminished hemoglobin Vitamin K ( phylloquinone)helps maintain ability to form blood clots Abnormal bleeding Water-soluble B vitaminsCoenzymes in biochemical reactions for growth and energy production Various nerve and skin disorders, anemia Vitamin C (ascorbic acid)Antioxidant; asisits in inhibiting bacterial and viral infections scurvy
Minerals Macromineral (ionic form)Some functionsDeficiency syndrome Sodium (Na + )Transportation of molecules across cell membrane, nerve function Muscle cramps, reduced appetite Potassium(K + )Transportation of molecules across cell membrane, nerve function Muscular weakness, paralysis, nausea, heart failure Calcium(Ca 2+ )Bone and tooth formation, nerve and muscle function Retarded growth, possibly loss of bone mass Magnesium(Mg 2+ )Enzyme functionNervous system disturbances Chlorine(Cl - )Transportation of molecules across cell membrane, digestive fluid, nerve function Muscle cramps, reduced appetite Phosphorus(H 2 PO 4- )Bone and tooth formation, nerve and muscle function Weakness, calcium loss Sulfur(SO 4 2- )Amino acid componentProtein deficiency Table 13.3 Some Macrominerals Needed by the Human Body
13.7 Metabolism ( 代谢 ) is the cycling of biomolecules through the body catabolism and metabolism
13.8 The food pyramid summarizes a healthful diet
Carbohydrates Glycemic Index （血糖指数） Glucose100Honey58 Baked potato85Sweet corn55 Cornflakes83Brown rice55 Microwaved potato82Popcorn55 Jelly beans80Oatmeal cookies55 Vanilla wafer77Sweet potato54 French fries75Banana54 Cheerios74Milk chocolate49 White bread71Orange44 Mashed potato70Snickers candy bar40 Life-savers candy70Pinto beans39 Shredded wheat69Apple38 Wheat bread68Spaghetti, boiled 5minutes36 Sucrose64Skim milk32 Raisins64Whole milk27 Mars candy bar64Grapefruit25 High-fructose corn syrup62soybean18 White rice58peanuts15 Table 13.4 Glycemic Index for Select Foods source: Jennie Brand Miller et al., the Glucose Revolution: the authoritative guide to the Glycemic index. Sydney: Marlowe & company, 1999
Unsaturated fats are generally more healthful than saturated fats Saturated fats are used to synthesize cholesterol. Fats are also packaged with water soluble proteins (Lipoproteins) to move through bloodstream. Hydrogenation of unsaturated fats can be used to prepare margarine and also in the process of making chocolates. LipoproteinPercent protein Density(g/ml)Primary function Very-low-density(VLDL)51.006-1.019Fat transport Low-density(LDL)251.019-1.063Cholesterol transport(to cells to build cell walls) High-density(HDL)501.063-1.210Cholesterol transport(to liver for processing) Table 13.5 The Classification of Lipoproteins