Lecture 1: Biochemistry

Transcription

1 Lecture 1: Biochemistry In this lession you will study some of the key terminologies commonly used in Biochemistry. You will be divided into small groups of 6-8 students and each group will discuss some aspects relating to the metabolism of nutrients. At the end of this lession, you will be required to write a short paragraph using the special terms that you have learnt. In addition, you will be asked to do some excercises about those terms to make sure that you understand and use them correctly. Key terminologies -Absorb (v): hấp thu -Absorption (n): sự hấp thu -Acting (n): tác dụng -Activate (v): hoạt hóa -Adapt (v): thích ứng, thích nghi -Aerobic (adj): hiếu khí -Amphipathic (adj): phân tử chứa phần kỵ nước và ưa nước -Anaerobic (adj): kỵ khí -Anabolism (n): sự đồng hóa -Pathway: con đường, quá trình -Burst of energy: sự gắng sức -Carbon skeleton: sườn cacbon -Carnivorous (adj): ăn thịt -Catabolism (n): sự dị hóa -Cell (n): tế bào -Chylomicron (n): vi thể nhũ trấp -Circulation (n): sự tuần hoàn, sự lưu thông -Cycle (n): chu trình -Deamidation (n): khử amit -Deamination (n): khử amin -Detergent (n): chất tẩy -Diet (n): khẩu phần -Dietary (adj): thuộc về khẩu phần -Digestion (n): sự tiêu hóa -Eicosanoid (n): chất truyền tín hiệu -End product: sản phẩm cuối cùng -Endoplasmic reticulum: mạng lưới nội chất -Energy (n): năng lượng -Equivalent (adj): tương đương -Fat (n): mỡ -Fatty acid-binding protein: protein mang (liên kết) axít béo -Fatty acids: các axít béo

2 -Feed (v): cung cấp -Gene expression: sự biểu lộ (biểu hiện) gien -Gluconeogenesis (n): sự sinh tổng hợp đường glucose (từ cơ chất không phải carbohydrate) -Glycolysis (n): sự đường phân -Hydrolysis (n): sự thủy phân -Hydrophilic (adj): ưa nước -Hydrophobic (adj): kỵ nước -Intracellular (adj): nội bào -Lactation (n): sự tiết sữa -Lipid (n): chất béo -Lipogenesis (n): sự hình thành chất béo -Locally (adv): có tính chất tại chỗ, cục bộ -Lymphatic (adj): (thuộc) bạch huyết -Mechanical protection: bảo vệ cơ học -Membrane (n): màng -Metabolic fuel: nhiên liệu biến dưỡng -Metabolism (n): sự trao đổi chất, sự chuyển hóa, sự biến dưỡng -Metabolite (n): chất chuyển hóa/trao đổi -Micelle (n): hạt mixen -Mitochondria (n): ti thể -Molecule (n): phân tử -Monoacylglycerol (n): chất béo chứa một phân tử axít béo -Mucosa (n): niêm mạc -Orchestrate (v): sắp đặt, tổ chức, phối hợp -Oxidation (n): oxy hóa -Peroxisome (n): vi thể peroxi -Phosphorylation (n): sự photphat hóa -Plasma (n): huyết tương, nguyên sinh chất -Polyunsaturated fatty acids: axít béo không no nhiều nối đôi -Precursor (n): tiền chất -Re-esterify (v): tái este hóa -Regulator (n): chất điều tiết -Release (v): giải phóng ra, cắt ra -Saturated (adj): bão hòa -Shuttle (v): vận chuyển qua lại -Small intestine: ruột non -Species (n): loài -Storage (n): dự trữ -Substrate (n): cơ chất -Suit (v): thỏa mãn, đáp ứng nhu cầu -Surplus (n): sự thừa, sự dư -Synthesis (n): sự tổng hợp -Take up (n): hấp thụ

3 -Thermal and electrical insulation: cách điện và nhiệt -Tissue (n): mô -Transaminate (n): chuyển nhóm amin -Transcription (n): quá trình phiên mã -Transform (v): chuyển dạng -Transporter (n): chất vận chuyển -Triacylglycerol (n): chất béo trung tính -Tricarboxylic acid cycle: chu trình tạo axít chứa 3 nhóm carboxy, chu trình axít citric, chu trình Krebs -Vessel (n): mạch, ống Reading Metabolism of fatty acids Fatty acids, both free and as part of complex lipids, play a number of key roles in metabolism major metabolic fuel (storage and transport of energy), as essential components of all membranes, and as gene regulators (Table 1). In addition, dietary lipids provide polyunsaturated fatty acids (PUFAs) that are precursors of powerful locally acting metabolites, i.e. the eicosanoids. As part of complex lipids, fatty acids are also important for thermal and electrical insulation, and for mechanical protection. Moreover, free fatty acids and their salts may function as detergents and soaps owing to their amphipathic properties and the formation of micelles. An adult consumes approximately 85 g of fat daily, most of it as triacylglycerols. During digestion, free fatty acids (FFA) and monoacylglycerols are released and absorbed in the small intestine. In the intestinal mucosa cells, FFA are re-esterified to triacylglycerols, which are transported via lymphatic vessels to the circulation as part of chylomicrons. In the circulation, fatty acids are transported bound to albumin or as part of lipoproteins. FFA are taken up into cells mainly by protein transporters in the plasma membrane and are transported intracellularly via fatty acidbinding proteins (FABP). FFA are then activated (acyl-coa) before they are shuttled via acyl-coabinding protein (ACBP) to mitochondria or peroxisomes for b-oxidation (and formation of energy as ATP and heat) or to endoplasmic reticulum for esterification to different classes of lipid. Acyl- CoA or certain FFA may bind to transcription factors that regulate gene expression or may be converted to signal molecules (eicosanoids). Glucose may be transformed to fatty acids (lipogenesis) if there is a surplus of glucose/energy in the cells. Glycolysis The first stage of glucose metabolism is called glycolysis, and it was the first biochemical pathway elucidated. Glycolysis is an anaerobic process that, by itself, yields only two molecules of ATP. The complete aerobic oxidation of glucose to carbon dioxide and water (involving glycolysis, the citric acid cycle, and oxidative phosphorylation) yields the energy equivalent of 32 molecules of ATP. During strenuous physical activity, the body aerobically metabolizes carbohydrates, fats, and

4 proteins for fuel; however, more carbohydrates are used as the intensity of physical activity increases. In sudden bursts of energy, such as in a 400-meter dash, the body uses carbohydrates faster than it can process them aerobically. Glucose will be metabolized via glycolysis, with pyruvate being the end product. This pyruvate will be converted to lactic acid, which will eventually be exported from muscle to the liver. Thus, the two ATPs from anaerobic glycolysis will be an additional energy source under these conditions. Under aerobic conditions, the main purpose of glycolysis is to feed pyruvate into the citric acid cycle, where further metabolic steps will give rise to considerably more ATP. Metabolism of amino acids Enzymes for the catabolism and synthesis of amino acids are present in every tissue, but their levels of expression and activities vary in some species to suit the metabolic needs or functions of the tissue. Catabolism involves deamination/deamidation reactions with the resulting carbon skeleton reaminated to form non-essential amino acids or the carbon skeleton can be channelled into the tricarboxylic acid cycle where it is either oxidized, channelled towards gluconeogenesis via pyruvate carboxylase, or from pyruvate converted into acetate for fatty acid synthesis. The excess nitrogen (amino groups) is ultimately transaminated to form alanine, aspar-tate, glutamine or glutamate for entry into the ornithine cycle for urea or arginine synthesis. Metabolism in ruminants is orchestrated to conserve glucose, and so it is no surprise that amino acid carbon contributes 12 35% to gluconeogenesis. In early lactation when glucose demands for lactose synthesis are high, and where glucose-precursor (propionate) supply is low, the channelling of amino acid carbon towards gluconeogenesis is probably vital. Fish species are unique in this respect because their diets are generally high in protein and fatty acids, but low in carbohydrates, particularly in carnivorous fish. Fish have adapted to use amino acids as the main substrates for gluconeogenesis and as the main oxidative fuel, especially in migratory fish, which may go for long periods without eating. Apart from dietary glucose and its immediate precursors (e.g. propionate in ruminants), all new glucose carbon derives from amino acid. Discussion 1.What are the functions of fatty acids? 2.Briefly describe how fatty acids are metabolized. 3.What is glycolysis? 4.How is an amino acid metabolized? Assignment 1.Fill in the blanks using the following words: fatty acids, dietary, glycolysis, molecule, pathway, synthesis, metabolites, catabolism

5 a).. represent 30 35% of total energy intake in many industrial countries and the most important sources of fatty acids are vegetable oils, dairy products, meat products, grain and fatty fish or fish oils. b) In., one of glucose is converted to fructose-1,6-bisphosphat, which eventually gives rise to two molecules of pyruvate. c) The glycolytic.. involves many steps, including the reactions in which of glucose are oxidized. d) The intestines and the liver are the major sites of amino acid.. and.. 2.Match the words in column A with the appropriate definitions in column B Column A Column B Correct answers 1 Amphipathic A A reaction involving the breaking of a bond in a molecule using water 2 Oxidation B Mucus-secreting membrane lining all body cavities or passages that communicate with the exterior 3 Mucosa C The loss of electrons from a compound 4 Hydrolysis D A molecule that possesses both hydrophobic and hydrophilic elements 5 Metabolism E The entire set of enzymecatalyzed transformations of organic molecules in living cells Grammar: key syllable and left syllable The major stress of nearly all polysyllabic words goes on the key syllable or the left syllable -To help us identify syllables using spelling, we say that each syllable begins with a vowel letter. It contains any following consonant letters, too. Example 1: the last syllable of each word is underlined. One Syllable Two Syllables Three or more Syllables graph credit economic list program paragraph stop echo misinterpret -Since a syllable begins with a vowel letter, we need to know which letters are vowel letters. Of course, a, e, i, and o are vowel letters. But as you will see later in this lesson, u and y are not always vowel letters. What is the key syllable? 1.The key syllable occurs at the end of a word or immediately to the left of an ending.

6 2.The key syllable consists of +All adjacent vowel letters but only the V of iv and uv spellings and +Any additional consonant letters up to the end of the word or up to an ending. Example 2: two vowel letters together represent one single vowel sound. Impairing, schools, sound, appeared, etc. Example 3: two vowel letters together represent two separate vowel sounds. iv spellings (ia, io, iu, iet, ienc): dieted, bias, triad uv spellings (ua, ue, ui, uo): fluid, duet, nuance How can I find the key? In order to find the key of any word, use this Key Search Strategy. -Work from the end of a word: greetings -Use a strike-out mark (/) to mark off any neutral ending: greetings. -Use an open parenthesis to separate any basic ending: greet(ings. -Look to the left until you find all of the adjacent vowel letters: greet(ings. -Underline all vowel and consonant letters up to the end of a word or up to an open parenthesis or a neutral ending: greet(ings. Exercise 1: Practice finding key syllables. Underline the key in each word below. Use the Key Search Strategy. third sound audit concerns promoted growing proudly admires enhance stirringly reputedly relaxing needles mountain sustaining