Giáo trình tiếng anh sinh học english in biology phần 2

CHEMICAL ASPECTS OF DIGESTION I T EX T Polysaccharides such as starch and glycogen form an important part of the food ingested by man and most animals T\\e glucose units of these large molecules are joined by glycoskllc bonds liiiking carbon (or carbon 6) of one glucose molecule with carbon of tl٠ie adjacent molecule These bonds are hydrolyzed by amylases These enzymes will digest polysaccharides to tl٦e disaccharide, maltose , but will not split the bond between the two glucose units of maltose Tlie amylases will split tlie a-glycosidic bonds present in starch and glycogen but not the B-glycosidic bonds present m cellulose The garden snail's digestive juice contains ii-glycosidases that can hydrolyze cellulose In most vertebrates, amylase is secreted only by the pancreas ; in man and certain other mammals, amylase is secreted by the salivary gland as well Different individuals have salivas containing different amounts of amylase ; thus the time required for the salivary digestion of a given amoui'it of starch will vary You can test the activity of your own saliva by this simple experiment An estimate of the amount of starch in solution can be obtained by adding a standard amount of iodine solution, which yields a bluecoloured complex with starch but not with sugar Place 10 ml of a dilute boiled starch solution in a test tube and add ml of saliva Mix thoroughly and at tlie end of each minute after the addition of the saliva, remove a drop and add it to a drop of iodine solution At first the resulting solution will be blue ; subsequently, samples will turn violet or red and eventually remain yellow, indicating that all the starch has been digested The red colour results from the reaction of iodine with certain mtermediate substances formed in the breakdo ١vn of starch to sugar All enzymes are proteins and are denatured, i.e., rendered inactive, by heating You can prove that the digestion of starch by saliva is mediated by enzymes by repeating the test using saliva that has been boiled 285 286 Unit Eleven Disaccharides are cleaved to monosaccharides by enzymes tl٦at are specific for the particular disaccharide Maltose is split by maltases present in saliva and in the intestinal juice secreted by intestinal glands The intestinal juice also contains sucrase , which splits tlie disaccharide sucrose to its constituents, glucose and fructose, and lactase, which split lactose (milk sugar) to glucose and galactose The ultimate products of the digestion of carbohydrates tlie hexoses, glucose, fructose and galactose - are absorbed into the blood stream through the intestinal wall There are several kinds of hydrolases that attack tlie peptide bonds of proteins ; each is specific for peptide bonds in a specific location in a polypeptide chain ExopeptiJases cleave the peptide bond joining the terminal amirio acids to tlie peptide chain Carboxypeptidase splits the peptide bond joining the amino acid witli tl٦e free terminal carboxyl group to the chain, and aniinopeptidase removes the amino acid with a free terminal a-amino group Other hydrolases, tl٠ie endopeptidases, will cleave only peptide bonds within a peptide chain Pepsin , secreted by tlie chief cells in the gastric mucosa, and trypsin and chymotrypsin , secreted by the pancreas, are endopeptidases but differ in their requirements for specific amino acids adjacent to the peptide bond to be cleaved These endopeptidases split peptide chains in smaller fragments which are then cleaved further by exopeptidases The combined action of tlie endopeptidases and exopeptidases results in splitting the protein molecules to free amino acids, which are then absorbed through the intestinal wall into the blood stream by active transport These powerful proteolytic enzymes would constitute a serious threat to the tissues secreting them However, pepsin, tiypsin and chymotrypsin are not secreted as such, but are secreted in the form of inactive precursors - pepsinogen, trypsinogen and chymotrypsinogen This prevents tlieir digesting the proteins of tlie cells that produce them In the gut each is activated by tlie removal of part of the precursor molecule to yield the active enzyme and an inactive fragment The digestion of fats is catalyzed by esterases that split the ester bond between glycerol and fatty acid The principal mammalian esterase is lipase , secreted by the pancreas Like other proteins, lipase is water-soluble, but its substrates are not Thus the enzyme can attack only those molecules of fat at the surface of a fat droplet The bile salts are detergents that reduce the surface tension of fats, breaking the large droplets of fat into very fine ones ; tliis greatly increases tlie surface area of fat exposed to tlie action of lipase and increases tlie rate of digestion of lipids Conditions in the intestine are usually not optimal for the complete hydrolysis of lipids to glycerol and fatty acids The products of digestion include glycerol and free fatty acids plus monoacylglycerols, diacylglycerols and some ti٠iacylglycerols, imdigested fats The pancreas also secretes ribonuclease, an esterase which splits the phosphate ester bonds linking adjacent nucleotides in ribonucleic acids, and deoxyribonuclease, which splits the phosphate ester bonds linking adjacent nucleotides in deoxyribonucleic acids Enzymes that complete the cleavage of nucleic acids are secreted by the intestinal mucosa Phosphodiesterase removes nucleotides one at a time from the end of a polynucleotide chain Tlie nucleotides in turn are attacked by phosphatases which remove the phosphate group and leave the nucleosides, which are absorbed It should be noted that these hydrolytic enzymes not usually serve for the formation of the bonds they normally split Starches are not syntliesized by amylases, proteins are not synthesized by pepsin or hypsin, and fats are not usually syntliesized by lipase Tlie English ỉn Biology 287 synthesis of a polysaccharide chain does not involve the removal of water from molecules of glucose but rather the removal of phosphate from molecules of glucose-phosphate As a general rule organic compounds are synthesized in the cell by enzyme systems that differ, at least in certain key enzymes, from those that take the compound apart II BIOLOGICAL T E R M S (CÁC TH UẬT NGỮ SINH HOC) Amylase (amilaza) : Enzyme which hydrolyses the internal 1,4-glycosidic bonds of starch Chyniotrypsm (kimotripxin) : A peptidase of the mammalian digestive system which is specific for peptide ponds adjacent to amio acids with aromatic or bulky hydrophobic side chains Dénaturation (sự biến tính) : The destruction of the native conformation or state of a biological molecule by heat, exti'emes of pH, heavy metal ions, chaotropic agents etc., resulting in loss of biological activity Specifically in DNA, the breakage of the hydrogen bonds maintaining the double-helical stiucture, a process which can be reserved by renaturation or annealing Eiuiopeptidase (endopeptidaza) : An enzyme which cuts a polypeptide chain internally, not just removing terminal peptides Exopeptidases (ekzopeptidaza) : Peptidases which attack terminal peptide linkages, thus spitting off amino acids Esterase (esteraza) ; An enzyme which catalyses the hydrolysis of ester bonds Fatty adds (axit béo) : A term for the whole group of saturated and unsaturated monobasic aliphatic carboxylic acids The lower members of the series are liquids of pungent odour and corrosive action, soluble in water; the ilitermediate members are oily liquids of unpleasant smell, slightly soluble in water The higher members from Cjo upwards, are mainly solids, insoluble in water, but soluble in ethanol and in ethoxyethane Medically, saturated fatty acids with no double bonds are linked with tlie development of atheroma In conti'ast the polyunsaturated fatty acids, Imoleic, linolenic and arachidonic are termed essential fatty acids as they must be included in the diet and may have a preventative role against atheroma and are required for tl٦e syirthesis of prostaglandiiis (biologically active lipids produced during anaphylactic reactions, some of which have antagonistic actions on platelet activation and vascular permeability) Glycogen (glicogen) : Storage polysaccharide, a,1-4 linked with frequent a ,1-6 branches, existing as small granules in cyanobacteria and otlier bacteria and in the cytoplasm of eumycete fungi and animals but not m plants or algae Mucosa {Mucous membrane, màng nháy) ; A tissue layer found lining various tubular cavities of the body (as the gut, uterus, trachea etc.) It is composed of a layer of epithelium containing numerous unicellular mucous glands and an underlying layer of areolar and lymphoid tissue, separated by a basement membrane 10 Pancreas (tụy) : A moderately compact sti'ucture found in Vertebrates, tlie larger part of which consists of exocrine glandular tissue with one or more ducts opening to the small mtestine , and also containing scattered islets of endocrine tissue Tl٦e former produces six or more enzymes involved in the digestion of proteins, carbohydrates, and fats, while the latter secrete the hormones insulin and glucacon 11 Pepsin (pepsin) : Protease of the gastric juice which is able to function optimally under the acidic conditions of the stomach Unit Eleven 288 12 Peptidase (pepticlaza) : An enzyme which degrades peptides into their constituent ammo acids 13 Peptide (peptit) ; A sequence of amino acids held togethrt by peptide bonds With rare exceptions peptides are unbranched chains joined by peptide bonds between their a-amino and a-carboxyl groups Peptides can vary in length from dipeptides with to polypeptides with several hundred amino acids 14 Precursor (tiền chat) : A substance which precedes the formation of a compound 15 Trypsin (h.ipsũi) : A protease secreted by tire pancreas which is specific for peptide bonds adjacent to lysme and argmiire residues III GRAM M AR RELATIVE PRONOUNS USED WITH PREPOSITIONS AND PREPOSITIONAL PH R A SES (CÁC ĐẠI TỪ QUAN HỆ DÙNG VỚI GIỚI T Ừ V À CỤM GIỚI T Ừ ) Các đại từ quan hệ có thê đưỢc sử dụng với giới từ cụm giới từ WHOM, WHOSE, WHICH Riêng đại từ quan hệ THAT khổng thể sử dụng theo cách Ví d ụ : You are tire person on whose help and advice I have always been able to rely (Anh người mà tơi ln ln có thê dựa vào nlrững giúp đỡ lời khuyên) My teacher is a person from whom I have always received the greatest encouragement (Thầy giáo tơi người mà từ luôn nhận lời cổ vũ to lớn nhâ١ ) Across the river was a large dam at the base of which was a powerhouse (Chắn ngang dịng sơng đập mà chân nhà máy điện) Iron, on which man depended for many hundreds of years, has now been replaced by many alloys (Sắt, kim loại mà người lệ thuộc nhiều kỷ thay nhiều loại hỢp kim) He had a serious accident in his car as a result of which he is crippled for live ( Anh ta gặp tai nạn nghiêm trọng chiêc xe mừih mà hậu bị què quặt suốt đời) TH E PO SSESSIVE RELATIVE PRONOUN "W HOSE" (ĐẠI TỪ QUAN HỆ sở HỮU "WHOSE") WHOSE đại từ sở hữu thường sử dụng ữong mệi٦h đề quan hệ để giải thích cho danh từ người, song dùng cho danh từ khơng người Ví dụ : The professor, whose book on Immunology is a standard textbook, is now givmg a series of lectures at the university (Vi giáo sư, mà cuốh sách ông Miễn dịch học sách giáo khoa chuẩn mực, giảng nlìiều giáo tiliứi Trường Đại học Tổng hỢp) Penicillm, whose discoverer was Alexander Fleming, was the world's first English in Biology 289 antibiotic (Penixilin, mà người phát Alexander Fleming, chat kiiáng sinh thê" giới) Cần lưu ý ià, khí chuyển mệnli đề phụ thành câu hồn chỉnh danli từ thay WHOSE luôn nằm dạng danli từ sơ hửu Trong ví dụ nói ti١ên, câu hốn chỉnh chuyển từ mệnh đề phụ ; The professor's book on Immunology is a standart texbook Do vậy, câu phức hỢp, WHOSE chiếm vị trí PROFESSORS Ngồi ra, WHOSE cóthê di với giới từ đứng trước ví dụ WHICH" RELATIVE C L A U S E S TH AT R EFER TO A SE N T EN C E MỆNH Đ Ề QUAN HỆ TR O N G ĐĨ "WHICH" GIẢI THÍCH CHO C Ả MỘT CÂU Đối khi, đại từ quan hệ "WHICH" khơng giải tiiích cho daiìh từ hay đại từ mà cho câu Câ"u trúc thường gặp mệi-ih đề quan hệ bìi٦h giải Hãy xem xét ví dụ sau : The research project yielded few useful results, which is uiiderstandable considering the small amount of money spent on it (Dự án nghiên cứu đạt kết hữu ích điều dễ hiểu klìi xem xét lượng tiền ỏi mà dư án tiêu.) Rỏ ràng đại từ WHICH ưong câu khơng giải tiìích cho "dự án" khơng cho "các kết quả" Thực tế giải tlìích cho câu đứng ữước nó, tức "dự án nghiên cứu đạt đưỢc kết hữu ích" Sau số ví dụ khác : The Ministry of Science, Technology and Environment may decide not to fmance the project, in which case the last six months' research will be wasted (Bộ Klioa học, Cơng nghệ Mơi ti.ường có thê định khơng tải trỢ cho dự án, ữong ti.ường hợp phần nghiên cứu tháng vừa trở thành lãng phí) 10 The death rate of village children is very high, which is only to be expected in such a remote mountainous area (Ty lệ tử vong trẻ em nông thôn râ"t cao, điều mà lẽ có thê gặp vùng núi cao xa xơi) 1 Tlìe ti'actor failed to start, which was the result of negected mamtenance (Chiêc máy cày không khởi động đưỢc, hậu việc bảo dưỡng câu tlìả) IV EX ER C IS ES Study the following passage and the paragraph beneath i t : SOURCES OF ENERGY ١The fuels of the body are carbohydrates, fats and proteins ‘These are taken in the diet ١They are found mamly in cereal grains, vegetable oils, meat, fish, and dairy products ^Carbohydrates are tlie prmcipal source of energy in most diets ^They are absorbed into the bloodstream in the form of glucose ^Glucose not needed for immediate use is converted into glycogen and stored in the liver "When the blood sugar concentration goes down, the liver 290 Unit Eleven reconverts some of its stored glycogen into glucose ®Fats make up the second largest source of energy in most diets ٦١ hey are stored in adipose tissue and round the principal internal organs ^٥If excess carbohydrate is taken in, this can be converted into fat and stored ” The stored fat is utilized when the liver is empty of glycogen ^“Proteins are essential for tlie growth and rebuilding of tissue, but they can also be utilized as a source of energy ” I1.1 sonic diets, such as the diet of the Eskimo, they form the main source of energy ” Proteins are fu٠st broken down iiito amino acids ^^Then they are absorbed iiito the blood and pass round the body ^^Amino acids not used by the body are eventually excreted in the urine in the form of urea ^^Proteins, unlike carbohydrates and fats, cannot be stored for future use (a) These are taken in the diet (2) d ese : carbohydrates, fats and proteins = the fuels of the body (!) Б ١е fuels o f tlie body are taken in tire diet (b) They (carbohydrates, fats aird proteins) are found MAINLY ii٦ cereal grairrs, vegetable oils, meat, fish, and dairy products (3) mainly # only It is NOT TRUE that carbohydrates, fats and proteins are found ONLY in cereal graiirs, vegetable oils, meat, fish and dairy products (c) They (carbohydrates) are absorbed into tire bloodsheam in the form of glucose (5) i.e Carbohydrates are converted into glucose Glucose not needed for immediate use is converted into glycogen and stored hr the liver (‫)؛‬ I.e Glucose is stored in the liver as glycogeir : ٠ Carbohydrates are stored in the liver as glycogen (d) They (fats) are stored in adipose tissue aird round the prirrcipal irrtemal orgairs (9) i.e Fats are stored round the principal Urtenral organs AND ALSO hr adipose tissue It is NOT TRUE that fats are stored ONLY round tire principal hrtemal organs (‫ ) ﺀ‬Proteins are essential for the growth and rebuilding of tissue (12) i.e Proteins are essential for growth they (proteins) CAN also be utilized as a source of energy (12) can # must i.e Proteins are irot essential for eirergy Proteins are essential for growth but they are irot esseirtial for eirergy Proteins are NOT essential for growtlr AND enei'gy (f) In SOME diets, such as the diet of tire Eskimo, tlrey (proteins) form tire main source of energy (13) hr some diets # hr most diets Proteins are NOT the main source of energy hr MOST diets (g) They (amino adds) are absorbed into the blood (15) Amino acids irot used by tire body are evenhrally excreted irr tire urhre in tire fornr of urea ‫ ؟‬٠‫)؛‬amhro acids are absorbed into the blood in the first place, (see 15) All It is NOT TRUE that amino acids which are not absorbed into the blood are excreted hr tire urine in tire form of urea (h) Proteins, unlike carbohydrates and fats, caimot be stored for future use (17) English in Biology 291 /.،■ Carbohydrates and fats are not like proteins Proteins CANNOT be stored for future use Carbohydrates and fats CAN be stored for future use True-False Question : (a) Tl٦e fuels of the body are taken in the diet (b) Carbohydrates, fats and proteins are found only in cereal grams, vegetable oils, meat, fish and dairy products (c) Carbohydrates are stored m the liver as glycogen (٥) Fats are stored only round the principal internal orgaiis (e) Proteins are essential for growth and energy (f) Proteins are the main source of energy in most diets (g) Amino acids which are not absorbed into tlie blood are excreted in die urine in the form of urea (h) Carbohydrates and fats cannot be stored for future use Complete the following sentences after studying the reading passage : "these" in sentence refers to "they" in sentence 5refers to "this" in sentence 10 refers to "d١ey" in sentence 13 refers to "diey" in sentence 15 refers to Rewrite the following sentences replacing the words printed in italics with expressions from the reading passage which have the same meaning : Cereal grains are one of the main sources of carbohydrate in the diet Glucose which is not needed immediately is converted into glycogen Carbohydrates are stored in the liver a،‫ ؟‬glycogen The liver reconverts some of its glycogen when the blood sugar concentration falls, If too much sugar is ingested, it is excreted in the urine A well-balanced diet is necessary {or growth and energy in contrast with milk, beef contains no vitamin A and no vitamin C Glycogen, derived from glucose, is stored for later use Place the following expressions in die sentences indicated Where necessary, replace and re-order the words in the sentences, and change the punctuation : (a) of course (4) (b) also (9) (c) in addition (12 ) (d) indeed (e) for (f) therefore (17) Complete die diagram by filling in the blanks : example (13) (13) 292 Unit Eleven Finish the following sentences usiiig the completed diagram Use tire verbs absorb,, convert and store: N.B The verbs are all used here in the passive (a) (b) (c) (d) (e) (f) (g) (h) (i) Carbohydrates into glucose Glucose into glycogen Glucose into the blood Glycogen iir the liver Glycogen back into glucose, and this into the blood Fats in and round the Proteins into Amino acids into the blood.' The amino acids not needed by the cells of the body into urea and excreted in the Complete the following lists with reference to the first paragraph of the reading passage : (a) The fuels-of the body are (b) They are found mainly in English in Bioiogy 293 Notice how these lists are punctuated in the reading passage: (a) carbohydrates, fats and proteins (b) cereal grains, vegetable oils, meat, fish, and dairy products When a list is written out within a sentence, items are separated by commas and the last two items are separated by and You may put a comma before and if you want to Lists (a) and (b) above could also be written: (a) carbohydrates, fats, and proteins (b) cereal grains, vegetable oils, meat, fish and dairy products Write out the following lists with the appropriate punctuation Insert them into the sentences at the places marked by dots : EXAMPLE The small intestine consists o f tlie duodenum the jejunum the ileum The small intestine consists of the duodenum, the jejunum, and the ileum (or; Tire small intestine consists of the duodenum, the jejunum and tire ileum.) (a) The spleen touches the diaphragm the end of the pancreas the left kidney (b) The principal bones of the face are the frontal bone the temporal bone the nasal bone tire maxilla tire mandible (c) The enter the lungs on their inner side bronchi blood vessels lymphatic vessels nerves (d) The following are the chief branches of the aorta: the coeliac artery the superior mesenteric artery the renal arteries the gonadal arteries the inferior mesenteric artery (e) Splenic pulp consists of a network of fibrous connective tissue with in the meshes red blood corpuscles lymphocytes reticulo-endothelial cells 294 Unit Eleven (f) The functions of the back muscles are to support the spine to move the spine to move the exti.emities of the body 10 Short-form relative clauses A relative clause containing a p،?s'.s7Vt verb can be shortened as follows: (a) Glycogen which has been stored in tiie liver be reconverted iiito glucose (b) Glycogen stored in the liver Ccin be reconverted into glucose A relative clause containing ai٦ acY/Ve verb can be shortened as follows: (c) Mucous membrane lines spaces which communicate with the outside o f the body (d) Mucous membrane lines spaces comm unicci ting with the outside o f the body Rewrite the relative clauses in the following sentences as in examples (b) or (d) above N.B Retain the commas when the clause is non-defining Iron, which is found mainly in meat, eggs, beans and peas, is an essential part of the diet The acidity of chyme in the duodenum is reduced by bile, a substance which is produced by the liver The cells which form the islets of Langerhans have no ducts The oesophagus is a tube which leads from the pharynx to the stomach The envelope which encloses haemoglobin is a semi-permeable membrane Fat which has been absorbed into the lacteals passes into the bloodsheam at tlie left internal jugular vem The mah.ix of bone is made up of an inorganic material, which contains calcium phosphate The mandible is made up of tw^o halves, which fuse at the midline to form the chin Most of the energy which is required by the body is derived from carbohydrates and fats 10 The intestine receives food which is already partly digested 11 The cytoplasm of a neutrophil contains numerous granules which stain with acid and basic dyes 12 Pepsin and hydrochloric acid are among constituents of the juice which is secreted by the stomach 13 The epithelium which lines the urinary passages is referred to as transitional epithelium 14 Bulk in tlie faeces may be provided by cellulose, which is taken in the diet 15 Reticular tissue is a special type of areolar tissue, which consists of a loose network of fiiie collagen fibres 11 Rewrite the following sentences so that each contains a relative clause beginning with which Take care in choosing active or passive voice : The shaft of a Ioi٦g bone consists of compact bone surrounding a tubular cavity Glycogen, derived from glucose, is stored for future use Food broken down by enzymes is absorbed through the linmg of the mtestine into the blood Amino acids not required for new protoplasm can be utilized by the liver in the manufacture of fibrinogen The pyloric sphiiicter, separating the stomach from the duodenum, opens periodically to English in Biology 295 allow some of the chyme to pass through Vitamin K is required for the formation of prothrombin, a substance needed for blood- clotting The spinal cord gives off paired spiiaal nerves, passing out between the vertebrae Glucose taken out of tlie bloodsti.eam by the muscles is converted into glycogen until needed Juices secreted by the stomach, liver and pancreas all play a part m the digestive process 10 The epithelial cells forming the mucous membrane of \he stomach are columnar in shape 11 The thyroid gland is an endocrine gland consisting of two lobes joined at their lower ends 12 The portal vein carries to the liver the products of digestion absorbed into the bloodstream 13 Air is expelled from the thorax as a result of a passive elastic recoil occurring in tlie lungs and the thoracic wall 14 The small intestine receives sucrose broken down into glucose and fructose 15 There are muscles at tl٠ie base of the little finger forming the hypothenar eminence 12 Complete tlie following sentences so tliat each contains a short-form relative clause Use tl٦e -ing or tlie -e J form of tlie verbs below : attach cover separate form grow produce lie contain The marrow cells within bone have a haemopoietic function The serous membrane the pericardium is reflected over tlie surface of the heart The diaphragm is a dome-shaped muscle to the ribs and vertebrae Tlie skull may be divided into tlie face, with its sinuses and cavities, and the cranium, the brain Calcified cartilage and dead cells are replaced by bone The mediastinum is a partition the two lungs The movements of the vertebral column are produced by muscles widely from each other The bones the hand and wrist are the carpals, metacarpals and phalanges A mucous membrane with columnar ciliated epithelium lines the nasal cavities 10 Tlie infratemporal fossa is a space beneath the base of the skull between the pharynx and the mandible 11 Ovulation is suppressed by progesterone a hormone by tlie corpus luteum 12 ٠3 weat glands are tubes of epitlielium - down from the epidermis into the corium 13 Study tlie following graph and the paragraph beneath it Complete the paragraph with reference to the graph : Unit Eleven 296 10 20 30 40 50 60 70 80 90 100 calories protein % calcium Percentage o f daily requirements in in ounces o f beef iron v.tamin A v.tamm B riboflavin nicotinamide vitamin C Four ounces of beef supply 60% of the daily requirement o f % of tl٦e protein and about 28% Beef tarns no and no , and only 3% of the necessary 14 Compare the following graph with the paragraph above, and then complete the paragraph beneath i t : 10 20 30 40 50 60 70 80 90 100 calories Percentage o f daily requirements in ounces o f haddock protein calcium iron vitamin A vitamin ١ riboflavin nicotinamide vitamin C and four ounces of beef supply almost equal amounts o f a n d Like , haddock contains n o and no , but haddock supplies less vitamm beef Beef is the greater source o f , ai٦d It has about 45% more nicotinamide, more iron, a n d than haddock 15 Use the following graph to write a paragraph describiiig tire percentage of daily requirements contained in a half pint of milk (3-4 sentences) 10 20 30 40 50 60 70 80 90 100 calories protein calcium iron vitamin A vitamin Bj riboflavin P Ш1 I % ГШШ Percentage o f daily requirements in beef haddock and m ilk f١.cotinam.de vitamin C 16 Compare the graph in with the graph in Write a paragraph-describing the differences betw^een beef and milk as sources of daily requirements (^4-5 sentences) English in Biology 297 17 Join each of the groups of sentences below into one longer sentence, using the additional words printed in capital letters above some of the groups Omit words in italics You may use relative clauses or short-form relative clauses, but note that these are NOT indicated The most powerful enzyme is pepsin Pepsin begins the process of converting proteins into amino acids BOTH/AND The stomach has a chemical function The stomach has a physical function Waves of peristalsis chum the food particles into a semi-solid mass The semi-solid mass is known as chyme ALTHOUGH/UNTIL Enzymatic action begins in the mouth The major processes of digestion nut occur in the mouth The food passes down tlirough the oesophagus into the stomach Waves of contraction and relaxation occur These ivaves are known as peristalsis sweep the walls of the stomach The walls of the stomach secrete gastric juices The gastric juices are composed of several enzymes and hydrochloric acid The wails o f the stomach are protected by a layer of mucus 18 Rewrite the six sentences in a logical order to make a paragraph, making the following changes to the sentences indicated: write "they" instead of "waves of peristalsis" in sentence write "ill addition, durmg these chemical reactions" at the beginning of sentence When you have written your paragraph, re-read it and make sure the sentences are presented in a logical order Give the paragraph a suitable title Compare your paragraph with the relevant paragraph in the Free Reading passage Make any changes that you think are necessary, but remember that sentences can often be arranged in more than one way 19 Read through the paragraph again Make sure you know all the words, using a dictionary if necessary Without referring to your previous work, rewrite the paragraph Here are some notes to help you enzymatic action - mouth - major digestive processes - stomach stomach - two functions - (1 ) chemical (2) physical (1 ) walls - protected by mucus - secrete gastric juices ٠ several enzymes -hydrochloric acid most powerful ٠ pepsin - begins process - converting proteins - amino acids (2) waves of conti'action and relaxation - peristalsis - sweep walls of stomach churn food particles - semi-solid mass - chyme ١ 20 Read the following passage in your own time Try to find additional examples of the points you have studied in tliis and other units Unit Eleven 298 THE PROCESS OF DIGESTION The process of digestion begins when food is taken into the mouth Chewing breaks the food into smaller pieces, thereby exposing more surfaces to the saliva Saliva itself has a double function It moistens the food, so facilitating swallowing, and it contains ptyalin which begins the conversion of starch into simple sugars Although enzymatic action begins in the mouth, the major processes of digestion not occur imtil the food passes down through the oesophagus into the stomach The stomach has both a chemical and a physical function The walls of the stomach, which are protected by a layer of mucus, secrete gastric juices composed of several enzymes and hydrochloric acid The most powerful enzyme is pepsin, which begins the process of converting proteins into amino acids In addition, during these chemical reactions waves of contraction and relaxation, known as peristalsis, sweep the walls of the stomach They chum the food particles into a semi-solid mass known as chyme From the stomach, the chyme passes into the small intestine through the pyloric sphincter Much undigested material is still present Proteins have not been completely broken down, starches are still being converted into simple sugars, and fats remain in large globules In the small intestine the process of digestion is completed by the action of bile, which is secreted by the liver and released by the gall bladder, and by the action of various enzymes; such-as lipase and diastase,- which are secreted by the pancreas, and erepsin and invertase, secreted by the walls of the small intestine Foods which are still undigested pass on in a liquid state into the large intestine, and are now called faeces Absorption of the products of digestion takes place mainly through the wall of the small intestine Its inner surface is covered with minute hair-like projections called villi Each villus contains several blood capillaries and a specialized lymphatic vessel, known as a lacteal Glucose, fructose, galactose and the amino acids are all absorbed directly into the blood by entering the blood capillaries inside the villi Glycerol and the fatty acids, on the other hand, pass into the lacteals The lymph then carries the fat up to the left internal jugular vein, where it enters the bloodstream 21 The following are the food substances required by human : Carbohydrates, water, fat, proteins, mineral salts, vitamins, roughage (i) Which of the above food substances provide the body with energy? (ii) State the unit used to measure tlie energy value of food (iii) Name the apparatus used to measure the energy value of food (iv) Which food substance is not absorbed by the body at all? (v) State whether the following statements are true or false (1) We can take vitamins when we are himgry (2) Proteins are only for growth and tissue repair (3) We cannot make vitamins All of them must be obtained from food (4) We become fat only when we take in excess fat (5) Water can only be obtained from drinking water (6) All vitamins are destroyed by heat English in Biology 299 22 The table below shows the energy (in kj/g) of some common foods together with the percentage of carbohydrate, fat, protein and water in each Food Potatoes Beans Fish Milk Beef Cabbage Butter kJ/g 3.4 2.7 9.0 2.7 9.2 0.66 32 ،‫^؟‬W — 4 !9 ٠7o X ٠7o Y 17.5 60 80 15 77 88 62 95 17 — — — 82 — %Z 2.5 20 18 19 1 i) Study the figures in the table and state what W, X,Y and Z belong to respectively (ii) Explain why tiie total percentages of W, X, Y and Z in beans not add up to 100% (iii) Which food in the table has (1) tlie highest energy value ? (2) the lowest energy value? (iv) Which one of the foods is the most suitable for a vegetarian? Explam your answer 23 The diagram below illustrates a typical meal eaten by many people in the fast-food shop today coffee chips hamburger sugar (i) Give tliree reasons why this is not a balanced diet (ii) Give three ways ix\ which you could improve tlie balance of nutrients (iii) Wl٦at diseases could result from eating such unbalanced meals over a long period of time? ٠ State tire exact cause of each disease 24 Tire table below shows some of the food substances contained hr lOOg portions of five plants Carbo­ Protein Fat Carotene Vitamin C hydrate (g) (g) (mg) (Mg) (g) Rice 87 6.2 1.0 Tomatoes 2.4 117 0.8 24 Potatoes 20.2 1.4 15 Peas 7.7 5.8■ 0.2 50 15 Carrots 5.4 0.7 2000 Plants — — — — — — Unit Eleven 300 (i) Which of the five plants will yield the most energy? Explain your answer (ii) State and explain which plant in tlie table would best help you to prevent (1) scurvy (2) night blindness (iii) (1) Describe how you can test for the presence of vitamin Q and state the result of the test (2) What advice would you give to a chef about cooking vegetables? (iv) (1) Name the food substance provided by plants only but it is not listed in the table (2) State the function of this food substance 25 The table below shows the approximate amount of energy used by the body in one minute for various activities sleeping sitting writing sewing eating teaching housework playiirg the piano wood-working washing and dressing walking fairly fast playing tennis playing baseball 2.5 kj/m in 2.9 kJ/min 3.4 kJ/min 3.5 kJ/min 4.3 kJ/min 8.1 kJ/min 8.2 kJ/min 9.8 kJ/min 10.5 k j/ 15.0 kJ/min 18.5 kJ/min 25.0 kJ/min 35.5 kJ/m in (i) Which activity requires tlie greatest amount of energy ? (ii) Tire following table shows the activities of a teacher in 24 hours walking teaching eating washing and dressing writing sitting sleeping l'/2 ٠ /: 4 hour hours hours hour hours hours hours Calculate the total amount of energy used up by the teacher in 24 hours Show your working in full 26 The table below shows die approximate values for the daily requirements of energy and protein for males of different ages English in Biology 301 Age Body mass Energy Protein Protein (g protein (years) (kg) (kJ) per kg body mass) (g) 11 34 10 500 70 2.1 18 62 16 000 100 1.6 25 75 13 500 65 0.9 60 75 11 000 65 0.9 (i) What you observe about the energy requirements of the four age groups? (ii) Account for the difference in the energy requirements between an 18-year-old and a 60year-old male (iii) What can you observe about the protein requirements per kg of body n^ass between the ages of 11 and 25 years? (iv) State one function of the protein consumed by the 60-year-old male (v) Name two foods which could provide a large proportion of proteins in a diet 27 The table below shows the composition by weight of certain nutrients present in soya beans and milk The daily requirement of an adult for the respective nutrients is also included Nutrient A m oun t in lOOg soya bean A m ount in D aily lOOg requirem ent milk o f an adult (g) (g) 3.30 80.00 Protein (g) 38.00 Carbohydrate 31.30 4.70 380.00 Fai 18.00 3.80 80.00 0.06 0.12 Calcium (i) If the adult took in only lOOOg of soya bean in (1) which nutrients shown in the table would be m excess of his daily requirement ? (2) what would be the fate of the excess nutrients in ( 1) in his body? (ii) Given that the energy content of 100 g of milk is 272 k j , calculate the minimum amount of milk a baby should take per day in order to meet its daily energy requirement of 400 kJ (iii) Why is milk considered an ideal food for babies? (iv) What is the importance of calcium in the body? (v) State a test for the presence of protein in milk, and the result of such a test 28 The table below shows an analysis of the food taken by a 15-year-old boy during the course of one day : Unit Eleven 30 Food components Food taken Meal Breakfast Lunch Supper hot dog milk fried chicken leg potato chips soft drink barbecued pork rice Daily total carbohy­ drates (g) fat Energy obtained (R) protein (g) vitam in c (mg) roughage (g) 105 26 18 0.5 3105 65 33 45 3238 108 15 36 3000 278 74 99 2.5 9343 (kJ) (i) Apart from water, which essential inorganic component of a balanced diet is not listed in the table? (ii) Of the food taken for lunch and supper, which one would provide tlie largest proportioi٠i of carbohydrate? (hi) The normal daily requirement of protein and energy recommended for such a boy is 70 g and 11700 kj, respectively (1) Describe what happens to tlie excess protem in his body (2) How can extra energy be derived from his body to meet his daily requirement? (iv) It is suggested that oranges should also be taken in order to make up for tlie deficiency of two of the food components listed (1) Give two reasons supporting this suggestion (2) State two kinds of disorder he would suffer as a result of a long term deficiency of such food components 29 Tlie table below shows tl٠ie average body weight, the daily requirements of energy and certain nutrients for four groups of people: Children (4 to years old) Men (23 to 50 years old) Women (23 to 50 years old) Pregnant women Body weight (kg) Energy Iron (kJ) Protein (g) Vitamin D (gg) (mg) 20 7560 30 10 10 70 11340 56 10 55 8400 44 18 65 9660 74 10 45 English In Biology 303 (i) (1) Which group of people requires \he greatest amount of energy per unit body weight? Show how you arrive at your answer (2) Suggest a reason why this group of people requires the greatest amount of energy per unit body weight (ii) How men differ from children ii٠i their requirements for vitamin D? Give a reason for this difference (iii) Of the three adult groups, which group requires tiie largest amount of protein? Why is this so? (iv) Account for the difference in iron requirement between men and non-pregnant women 30 The table below shows the contents and the energy value of human milk and cow's milk: H um an m ilk (per 100 cmO C ow ’s milk (per 100 cm^ protein fat carbohydrate 1.2 g 3.8 g g 3.4 g 3.8 g 4.8 g vitamin A vitamin C vitamin D 0.053 mg 4.3 mg 0.0008 mg 0.034 mg 1.80 mg 0.0002 mg calcium phosphorus 'iron 0.034 g 0.016 g 0.00021 g 0.126 g 0.100 g 0.00015 g water 87.6 g 87.2 g energy value 300 kJ 290 kJ Witli reference to the table above, answer the following questions: (1) (1) Which mineral is present in the least amount in both types of milk? (2) In the absence of this mineral, what deficiency symptom would develop? (ii) A one-year-old baby requires 5100 kj of energy a day How much humaii milk should the baby take in one day to meet its energy requirements? (iii) Give ONE advantage of breast feeding a baby over bottle feeding witli cow's milk Explain your answer (iv) Suggest TWO reasons why cow's milk is better for the growth of children and youths Explain your answer Unit Eleven 304 31 In an experiment, four spots on a starch agar plate were treated differently as shown in the diagram below: Spot A saliva mixed with acid saliva only The set-up was then incubated in an oven at 37.C After 24 hours, the agar plate was flooded with iodine solution and the results were recorded in the table below: Spot Content/treatment Colour change of the starch agar plate after flooding with iodine solution A В C D Saliva mixed with acid Boiled saliva Saliva only Bread mould only Blue black Blue black Reddish brown Reddish brown (i) (ii) (iii) (iv) Explain the colour change at spots A and B Briefly account for the result on spot D Suggest TWO reasons to explain why the agar plate was incubated at 37.C A similar set-up was left unattended After a week black dots were found covering the agar plate Draw a labelled diagram to show some of these black dots and their associated structures when observed imder a microscope of high magnification (v) Medical authorities advise that care should be taken in performing experiments using saliva Suggest ONE reason for this 32 Answer the following questions ; Describe an aldose and a ketose What is a glycosidic bond ? Draw a structure of an aldopentose Draw a structure of an aldohexose Draw a structure of a ketohexose What monosaccharides are produced from the hydrolysis of lactose ? What monosaccharides are produced from the hydrolysis of sucrose ? What are the structural similarities between amylose and amylopectin ? Explain why humans cannot digest cellulose  ... wood-working washing and dressing walking fairly fast playing tennis playing baseball 2. 5 kj/m in 2. 9 kJ/min 3.4 kJ/min 3.5 kJ/min 4.3 kJ/min 8.1 kJ/min 8 .2 kJ/min 9.8 kJ/min 10.5 k j/ 15.0 kJ/min... when we take in excess fat (5) Water can only be obtained from drinking water (6) All vitamins are destroyed by heat English in Biology 29 9 22 The table below shows the energy (in kj/g) of some... kJ/min 25 .0 kJ/min 35.5 kJ/m in (i) Which activity requires tlie greatest amount of energy ? (ii) Tire following table shows the activities of a teacher in 24 hours walking teaching eating washing