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HighFour Biology Category D: Grades 11 – 12 Round 8 Friday, April 22, 2016 The use of calculator is not required. Answer#1: Explanation: adrenal gland The adrenal glands are small glands located on top of the kidney. The adrenal cortex secretes steroid hormones that help maintain homeostasis during long-term stress, whereas the adrenal medulla secretes epinephrine and norepinephrine in response to nerve signals triggered by short-term stress. Answer #2: Explanation: florigen Florigen is the hypothetical hormone-like molecule responsible for flowering in plants. Until now, the exact nature of florigen remains unknown. Answer #3: Explanation: Shannon Diversity Index The Shannon Diversity Index is an index of community diversity symbolized by H and calculated using the relative abundance of the species in the community. A higher value of H indicates a more diverse community. Answer #4: Explanation: proton pump The proton pump is an active transport protein that utilizes adenosine triphosphate (ATP) to transport hydrogen ions against their concentration gradient, a process which generates membrane potential. Answer #5: Explanation: 3/ three The circular DNA has three restriction sites for EcoRI. As a result, digestion with EcoRI will produce three fragments. HighFour Biology Category D: Grades 11 – 12 Round 8 Friday, April 22, 2016 The use of calculator is not required. Answer #6: Explanation: methanogen Methanogens are organisms that produce methane as a waste product of the process by which they obtain energy. All known methanogens belong to the domain Archaea. Answer #7: Explanation: high-density lipoprotein (HDL) High-density lipoprotein or HDL is a particle in the blood that is made up of several cholesterol molecules and other lipids bound to a protein. HDL scavenges excess cholesterol and returns it to the liver. Individuals with high ratio of LDL to HDL are more at risk for heart disease. Answer #8: Explanation: sclerenchyma cells Sclerenchyma cells are specialized for support and strengthening. They can be subdivided into two types, namely sclereids and fibers. Sclereids bestow hardness to nutshells and seed coats, whereas fibers are typically grouped in strands, such as in hemp fibers. Answer #9: Explanation: serotonin Serotonin is a neurotransmitter released at many sites in the brain. It is involved in sleep, mood, attention, and learning. Answer #10: Explanation: law of independent assortment The law of independent assortment is applicable when genes for two characters are located on different pairs of homologous chromosomes or when they are far apart enough on the same chromosome. HighFour Biology Category D: Grades 11 – 12 Round 8 Friday, April 22, 2016 The use of calculator is not required. Answer #11: Explanation: ectoderm The ectoderm is the outermost of the three primary germ layers in animal embryos. It gives rise to the outer covering of the animal, and in some phyla, to the central nervous system. Answer #12: Explanation: sickle-cell disease Sickle-cell disease is a recessively inherited human blood disorder caused by a single nucleotide change in the β-globin gene. As a result, red blood cells assume a sickle shape, causing multiple symptoms in afflicted individuals. Answer #13: Explanation: peptide bond Peptide bond is the covalent bond that connects amino acids to form polypeptides. Extending from the polypeptide backbone are the different side chains (R groups) of amino acids. Answer #14: Explanation: electrocardiogram (ECG or EKG) An electrocardiogram is the record of the currents that travel through the heart muscle. The characteristic shape of ECG graphs is generated from the different stages in the cardiac cycle. Answer #15: Explanation: gel electrophoresis Gel electrophoresis is a technique for separating nucleic acids or proteins according to their sizes and electrical charges through an electric field in a gel made of polymer. HighFour Biology Category D: Grades 11 – 12 Round 8 Friday, April 22, 2016 The use of calculator is not required. Answer #16: Explanation interferons Interferons are proteins with antiviral or immune regulatory functions. They belong to the larger group of glycoprotein cytokines secreted by host lymphocytes. The activation of interferons ultimately leads to the clearance of the pathogen or tumor cells from the organism. Answer #17: Explanation: P site / peptidyl-tRNA binding site The P site or the peptidyl-tRNA binding site holds the tRNA which carries the growing polypeptide chain. During the initiation of translation, the P site holds the initiator tRNA for Met. Answer #18: Explanation: utricle and saccule The chambers called utricle and saccule participate in the sense of balance and open into the three semicircular canals. They contain a sheet of hair cells that project into a gelatinous material with many small calcium carbonate particles embedded onto it. Answer #19: Explanation: leptin Leptin acts as a satiety factor in regulating appetite. The exact nature of leptin remains unknown. For instance, it has complex functions, including in the development of the nervous system. It also apparently fails in eliciting a response from the brain’s satiety center when present in abnormally high amounts. Answer #20: Explanation: rhodopsin Rhodopsin is the visual pigment of rods. It consists of both retinal and opsin. As light is absorbed by rhodopsin, the retinal changes shape and dissociates from the opsin.