National Science Olympiad 2012: Life Sciences
Total Page:16
File Type:pdf, Size:1020Kb
NATIONAL SCIENCE OLYMPIAD 2012: LIFE SCIENCES These questions were compiled from a variety of sources and the detailed answers are mainly from WIKIPEDIA as well as Encyclopedia Britannica and some textbooks. The following structures are naturally Biotin (vitamin B7) is a water-soluble B- occurring compounds which perform various complex vitamin. It is composed of a functions in animal/mammalian biology. tetrahydroimidazalone ring fused with a Look at them carefully and answer questions tetrahydrothiophene ring. A valeric acid (1), (2), (3), (4), (5), (6), (7), (8), (9) and (10). substituent is attached to one of the carbon atoms of the tetrahydrothiophene ring. Biotin H H is a coenzyme in the metabolism and plays OH N HO S O a role in cell growth, the production of fatty N H H acids, and the metabolism of fats and amino O acids. It plays a role in the Krebs’ cycle, OH which is the process by which biochemical NH OH (1) (2) energy is generated during aerobic OH respiration. HO I I (2) Which structure is necessary for cell I O growth, the production of fatty acids, I and the metabolism of fats and amino acids? NH2 O (3) OH A) (1) (4) (B) (2) (C) (3) (1) Which of the structures is known as (D) (4) vitamin B7? ANSWER: B (A) (1) Please read the explanation in the answer to (B) (2) question (1) (C) (3) (D) (4) (3) Which structure is the precursor for the hormones testosterone and ANSWER: B oestrogen? 1 (A) (1) being stimulated by thyroid stimulating (B) (2) hormone. T4 is involved in controlling the (C) (4) rate of metabolic processes in the body and (D) None of the options (A) to (C) influencing physical development. ANSWER: (D) (5) Which of the structures is called Cholesterol [structure no (3)] is a waxy dopamine, a neurotransmitter in the steroid produced in the liver or intestines. It brain involved in cognition, mood, is an essential structural component of motivation and voluntary movement mammalian cell membranes and is required control? to establish proper membrane permeability and fluidity. In addition, cholesterol is an (A) (1) important component for the production of (B) (2) bile acids, steroid hormones (e.g., (C) (3) testosterone and oestrogen), and vitamin D. (D) None of the above (4) Which of the structures is involved ANSWER: (D) in controlling the rate of metabolic Dopamine, which has the IUPAC name 4-(2- processes in the body and aminoethyl)benzene-1,2-diol, has the influencing physical development? following structure: (A) (1) HO NH2 (B) (2) HO (C) (4) (D) None of the options (A) to (C) (6) Which of the structures is adrenaline, the fight/flight hormone? ANSWER: (C) Thyroxine, or 3,5,3',5'-tetraiodothyronine (A) (1) (often abbreviated as T ), is the major 4 (B) (2) hormone secreted by the follicular cells of (C) (3) the thyroid gland. Thyroxine is synthesized (D) (4) via the iodination and covalent bonding of the phenyl portions of tyrosine residues ANSWER: (A) found in an initial peptide, thyroglobulin, Adrenaline, also called epinephrine is a which is secreted into thyroid granules. hormone and neurotransmitter that These iodinated diphenyl compounds are increases heart rate, constricts blood cleaved from their peptide backbone upon vessels, dilates air passages and 2 participates in the fight of flight response of OH HO OH the sympathetic nervous system. Chemically, epinephrine is a catechol- O O OH derived monoamine, produced only by the adrenal glands from the amino acids Vitamin C, also known as ascorbic acid, phenylalanine and tyrosine. functions as a water-soluble antioxidant and as a cofactor in various enzyme systems, such as those involved in the synthesis of (7) Which of the structures is known as connective tissue components and triidothyronine, a hormone produced neurotransmitters. A deficiency in vitamin c by the thyroid gland? leads to scurvy, a disease whose symptoms include pinpoint hemorrhages (petechiae) (A) (2) under the skin, bleeding gums, joint pain, (B) (3) and impaired wound healing. (C) (4) (D) None of the above (9) Which of the structures is Follicle Stimulating Hormone, a peptide ANSWER: D hormone which regulates the The prefix triiodo means 3 iodine atoms in a development, growth, pubertal structure, whereas the depicted structure (4) maturation, and reproductive has 4 iodine atoms and is called processes of the body? tetraiodothyronine. See the Answer to Question 4. (A) (1) (B) (2) (8) Which of the structures is called (C) (4) ascorbic acid, also known as vitamin (D) None of the above C? ANSWER: D (A) (1) Follicle-stimulating hormone (FSH) is a (B) (3) glycoprotein hormone secreted by the (C) (4) pituitary gland. The hormone regulates the (D) None of the above development, growth, pubertal maturation, and reproductive processes of the body. It is ANSWER: (D) a dimeric structure containing two sub-units Vitamin C has the following structure: called alpha and beta, both of which have a sugar unit attached to them. The alpha subunit of FSH contains 92 amino acids and 3 is similar to that of three other hormones (11) Which mould was penicillin isolated secreted by the pituitary gland: Luteinizing from? Hormone (LH), Thyroid Stimulating Hormone (TSH) and human chorionic (A) Penicillium camemberti gonadotrophin (hCG). The beta subunit of (B) Penicillium roqueforti FSH has 118 amino acids and confers its (C) Penicillium chrysogenum specific biologic action and is responsible for (D) Penicillium marneffei interaction with the FSH receptor. The sugar part of the hormone is composed of fucose, ANSWER: C galactose, mannose, galactosamine, Penicillium chrysogenum is a fungus glucosamine and sialic acid. (mould) common in temperate and subtropical regions and can be found on (10) Which of the structures are salted food products, but it is mostly found in derivatives of the amino acid indoor environments, especially in damp tyrosine? buildings. It was previously known as Penicillium notatum. It is the source of (A) (1) and (2) several beta-lactam antibiotics, most notably (B) (2) and (3) penicillin. (C) (1) and (4) Penicillium camemberti is a species of (D) (1) and (3) fungus used in the production of Camembert and Brie cheeses, on which colonies of P. ANSWER: C camemberti form a hard, white crust. It is Please read the answers to questions (4) responsible for giving these cheeses their and (6). distinctive taste. Penicillium roqueforti is a fungus widespread The following statement was apparently in nature- it can be isolated from soil, uttered by Mohammad Ali, the legendary decaying organic matter, and plants. The heavyweight boxing champion, as advice to major industrial use of this fungus is the a young man. production of blue cheeses such as “Go to college and get an education and Roquefort, Stilton and Danish Blue. stay there until you finish. If they can make Penicillium marneffei, discovered in 1956, is penicillin out of mouldy bread, they sure can the only known thermally dimorphic species make something out of you!” of Penicillium and it can cause a lethal On the basis of this statement, please systemic infection (penicillosis) with fever answer questions (11), (12), (13) (14) and and anaemia. Discovered in bamboo rats in (15). Vietnam, it is associated with these rats and the tropical South-East Asia area. It infects 4 mainly immuno-compromised (HIV infected) Prize in Medicine or Physiology with Fleming people in that part of the world. However, an for this work. Penicillin has since become increase in global travel and migration the most widely used antibiotic to date and means it is increasingly becoming is still used for many Gram positive bacterial important/noticeable as an infection in AIDS infections. It works by inhibiting the sufferers worldwide. formation of peptidoglycan cross-links in the bacterial cell wall. (12) As an antibiotic, penicillin acts by (13) Which two amino acids are (A) inhibiting the formation of precursors to the bicyclic core of peptidoglycan cross-links in the penicillin? bacterial cell wall. (B) inhibiting DNA polymerases and (A) valine and cysteine leading to cell death (B) isoleucine and methionine (C) Blocking all bacterial transcription (C) proline and cycteine factors and inhibiting protein (D) proline and methionine synthesis. (D) None of the above. ANSWER: A Depicted below is the structure of penicillin ANSWER: A G. Penicillin refers to a group of beta-lactam antibiotics used in the treatment of bacterial H H N S infections caused by susceptible, usually O N Gram-positive, organisms. The O O HO serendipitous discovery of penicillin is usually attributed to Scottish scientist The first step in the biosynthesis of penicillin Alexander Fleming in 1928, though others G is the condensation of three amino acids had earlier noted the anti-bacterial effects of L-α-aminoadipic acid, L-cysteine, L-valine Penicillin. The chemical structure of into a tripeptide. This condensation is penicillin was determined by Dorothy catalyzed by an enzyme called δ-(L-α- Crowfoot Hodgkin in the early 1940s, aminoadipyl)-L-cysteine-D-valine enabling synthetic production. A team of synthetase. Before condensing into a Oxford research scientists led by Australian tripeptide, the amino acid L-valine will Howard Walter Florey and including Ernst undergo epimerization and become D- Boris Chain and Norman Heatley discovered valine. The second step is transformation of a method of mass producing the drug. the tripeptide by oxidation followed by ring Florey and Chain shared the 1945 Nobel closure to form the bicyclic structure. These 5 steps are catalyzed by the enzyme isopenicillin N synthase. The last step in the Clavulanic acid is a natural product that biosynthesis of penicillin G is the exchange contains a β-lactam group, similar to that of the side-chain group so that isopenicillin found in penicillins.