IB Biology HL Questions and answers IB Biology HL Questions and answers, Exams of Biology

Download IB Biology HL Questions and answers IB Biology HL Questions and answers and more Exams Biology in PDF only on Docsity! IB Biology HL Questions and answers What are the characteristics common to all forms of life? CORRECT ANSWERS✅ reproduction, carbon, responds to surroundings, Growth and Development, cellular organization, and energy. What are the levels of biological organization from simple to most complex? CORRECT ANSWERS✅ Molecules, cell, tissue, organ, organism, population, community, ecosystem, biosphere. What are the 4 most common types of biological molecules? CORRECT ANSWERS✅ Proteins, nucleic acids, carbohydrates, and lipids Organelle CORRECT ANSWERS✅ any of a number of organized or specialized structures in a living cell Cell CORRECT ANSWERS✅ The smallest structure and functional unit of an organism. Tissue CORRECT ANSWERS✅ The material of specialized cells and their products that make a wall of cells and their products IB Biology HL Questions and answers Organ CORRECT ANSWERS✅ a part of an organism that is self-contained and serves a function Organism CORRECT ANSWERS✅ an individual animal, plant, or single-celled life form What are the similarities and differences of a population and an ecosystem? CORRECT ANSWERS✅ a population and ecosystem both include organisms, however a population is one type of species while an ecosystem is both biotic and abiotic things. What is the definition of emergent properties? CORRECT ANSWERS✅ the feature that can't be directly from the features of its simpler parts eg. the taste of salt w/ the combination of Na+Cl What are the 4 shared characteristics of cells? CORRECT ANSWERS✅ DNA, cytoplasm, ribosome, and plasma membranes What is the definition of unicellular organisms? CORRECT ANSWERS✅ an organism that consists only of 1 cell eg. bacteria/microorganisms IB Biology HL Questions and answers What is the definition of anabolism? CORRECT ANSWERS✅ constructive metabolism that synthesizes more complex substances from simple substances What is the definition of an atom? CORRECT ANSWERS✅ The smallest unit of matter What is the definition of autotroph? CORRECT ANSWERS✅ any organism capable of self nourishment to get energy What is the definition of Biome? CORRECT ANSWERS✅ a large naturally occuring community of fauna and flora occupying that habitat What is the definition of biosphere? CORRECT ANSWERS✅ it is the part of the earth's crust, waters, and atmosphere that support life What is the definition of catabolism? CORRECT ANSWERS✅ the metabolism breaking down complex into simple substances with the release of energy What is the definition of cell? CORRECT ANSWERS✅ the smallest functioning structure of living matter IB Biology HL Questions and answers What is the definition of cell membrane? CORRECT ANSWERS✅ The semipermeable membrane enclosing the cytoplasm of a cell What is the definition of community? CORRECT ANSWERS✅ a set of species found in the same place at the same time What is the definition of cytoplasm? CORRECT ANSWERS✅ The cell substance between cell membrane and nucleus What is the definition of detritivore? CORRECT ANSWERS✅ an organism that uses organic waste as a food source What is the definition of differentiation? CORRECT ANSWERS✅ process by which cells or tissues change/specialize in development What is an electron? CORRECT ANSWERS✅ an elementary particle having negative charge and exists outside of the nucleus (electron cloud) What is evolution? CORRECT ANSWERS✅ process how different living organisms developed and diversified IB Biology HL Questions and answers What is growth? CORRECT ANSWERS✅ increasing in amount or complexity What is a heterotroph? CORRECT ANSWERS✅ organism deriving nutrients from complex organic substances What is a molecule? CORRECT ANSWERS✅ a group of atoms bonded together What is a neutron? CORRECT ANSWERS✅ a neutrally charged ion inside the nucleus with proton What is organization? CORRECT ANSWERS✅ organic structure or compositions What is a proton? CORRECT ANSWERS✅ A positive ion in the nucleus with a neutron What are ribosomes? CORRECT ANSWERS✅ tiny mitten-shaped organelles that manufacture proteins What is a saprotroph? CORRECT ANSWERS✅ organism that live and feeds on dead organic matter IB Biology HL Questions and answers Why are phospholipids in the membrane fluid? CORRECT ANSWERS✅ fluid membranes allow cells to be dynamic and responsive in their environment Why are some fatty acids considered saturated while others are unsaturated? CORRECT ANSWERS✅ saturated fatty acids are evenly filled with hydrogen, while double bonds in the hydrocarbon chain create unsaturated fatty acids What is the effect on the fluidity of being saturated or unsaturated? CORRECT ANSWERS✅ That the double bonds in the unsaturated require more room, so unsaturated is more fluid than saturated What is the function of the cholesterol molecules in the membrane? CORRECT ANSWERS✅ to provide protection from some water soluble molecules and provide structure in the cell membrane. Cholesterol also contains both a hydrophilic and hydrophobic What is adhesion? CORRECT ANSWERS✅ water is attracted to other substances (like how water sticks together) What is a carrier transport protein? CORRECT ANSWERS✅ can carry non charged substances across the membrane IB Biology HL Questions and answers What is a channel carrier protein? CORRECT ANSWERS✅ can carry charged substances across the membrane What is cholesterol in the membrane? CORRECT ANSWERS✅ used to build and maintain the membrane, and modulates membrane fluidity What is an enzyme? CORRECT ANSWERS✅ a substance produced by a living organism that acts as a catalyst in reactions What is a fatty acid? CORRECT ANSWERS✅ carboxylic acid consists of hydrocarbon chain and terminal carboxyl groups What is a fluid mosaic? CORRECT ANSWERS✅ widely accepted idea: in plasma membranes proteins are embedded in lipids What is an integral protein? CORRECT ANSWERS✅ protein molecule is permanently attached to biological membrane What is a peripheral protein? CORRECT ANSWERS✅ adheres only temporarily to biological membrane that they're associated IB Biology HL Questions and answers What is the phospholipid bilayer? CORRECT ANSWERS✅ thin membrane made of 2 layers of lipid molecules What is the plasma membrane? CORRECT ANSWERS✅ external fatty layer surrounding molecules of a cell What is a receptor? CORRECT ANSWERS✅ an organ or cell able to respond to stimuli and transmit signal What is saturated? CORRECT ANSWERS✅ containing no double or triple bonds 2.1.1 Outline Cell Theory CORRECT ANSWERS✅ Cell theory states that: all living organisms are composed of cells. Multicellular organisms are composed of many cells, while unicellular are of one cell. Cells are the basic unit of structure in all organisms. Cells are the smallest units of life capable of surviving on their own. Cells come from pre-existing cells and never non-living material 2.1.2 Discuss the evidence for the Cell Theory CORRECT ANSWERS✅ Scientists had experimented and found the cell was the smallest piece of living matter that could live on its own, and because of these units were so small, they were named cells. IB Biology HL Questions and answers 2.4.1 Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes. CORRECT ANSWERS✅ the phospholipid is both hydrophilic and hydrophobic. With a hydrophilic head pointed pointed out hydrophobic tailspointed in when the lipid is in water, the phospholipid can be flexible but strong. This is also in part that the hydrophobic tails like to be by each other. This is a stable structure with fluidity that allows the cell to change shape easily and maintain the structure of cell membranes 2.4.3 List the functions of membrane proteins. CORRECT ANSWERS✅ Membrane proteins can act as hormone binding sites, electron carriers, pumps for active transport, channels for passive transport, and enzymes. Also, they can be used for cell to cell communication and cell adhesion. 2.4.8 Describe how the fluidity of the membrane allows it to change shape, break and reform during endocytosis and exocytosis. CORRECT ANSWERS✅ the phospholipids int he cell membrane are not solid but are in a fluid state allowing the membrane to change its shape and also vesicles to fuse with. This means substances can enter the cell via endocytosis and exit via exocytosis. The membrane then returns to its original states. In exocytosis, the vesicles fuse with the membrane expelling their content outside the cell. The membrane then goes back to its original state. Endocytosis is a similar process which involves the pulling of the plasma membrane inwards so that a vesicle is pinched off and then this vesicle can carry its content to anywhere in the cell IB Biology HL Questions and answers 3.1.1 - State that the most frequently occurring elements in living things are carbon, hydrogen, oxygen and nitrogen. CORRECT ANSWERS✅ Carbon, hydrogen, oxygen and nitrogen are the most frequently occurring chemical elements in living things. All of these elements form macromolecules essential to life, and are macronutrients/important components in all biochemical molecules.This is why all organisms are carbon-based life-forms. 3.1.2 - State that a variety of other elements are needed by living organisms, including sulfur, calcium, phosphorus, iron and sodium. CORRECT ANSWERS✅ A variety of other elements are needed by living organisms including sulfur, calcium, phosphorus, iron and sodium to maintain homeostasis in living organisms with the most significant function being bonding to oxygen. 3.1.3 - State one role for each of the elements mentioned in 3.1.2 CORRECT ANSWERS✅ Sulfur is needed for the synthesis of two amino acids. Calcium acts as a messenger by binding to calmodulin and a few other proteins that regulate transcription and other processes in the cell. Phosphorus is a part of DNA molecules and is also part of the phosphate groups in ATP. Iron is needed for the synthesis of cytochromes that are proteins used during electron transport for aerobic cell respiration. Sodium upon entering the cytoplasm raises the solute concentration, which allows water to enter by osmosis. IB Biology HL Questions and answers 3.1.4 - Draw and label a diagram showing the structure of water molecules to show their polarity and hydrogen bond formation. CORRECT ANSWERS✅ The Hydrogen in this diagram are positive and the oxygen carries a -2 polarity. To let the Oxygen form bonds with other Hydrogen after becoming neutral, it must connect by a covalent bond to the Hydrogen of another neutral water molecule. 3.1.5 - Outline the thermal, cohesive and solvent properties of water. CORRECT ANSWERS✅ Thermal properties of water include heat capacity, boiling and freezing points and the cooling effect of evaporation. Due to water's substantial heat capacity, a significant amount of energy is needed to increase its temperature and break the many sturdy Hydrogen bonds included in its structure. This is why the temperature of water maintains homeostasis easily. Water has a high boiling and freezing point. It boils at 100 C due to strong hydrogen bonds that need to break before liquid can change to gas. Due to low density in the water as it reaches its freezing point, ice will float. To evaporate water below the boiling temperature, Hydrogen bonds need to break. Cohesion is the effect of hydrogen bonds holding the water molecules together. Capillary Action is due to cohesion. The polarity of water creates a magnetism in water, allowing for strong adhesion between water molecules. The solvent properties of water helps the many different molecules can adhere to it due to its polarity. 3.1.6 - Explain the relationship between the properties of water and its uses in living organisms as a coolant, medium for metabolic reactions and transport medium. CORRECT ANSWERS✅ Water can evaporate at temperatures below the IB Biology HL Questions and answers between two subunits. Monosaccharides are single monomers that are joined to form disaccharides, while sugars containing multiple subunits are called polysaccharides. 3.2.6 - State three functions of lipids. CORRECT ANSWERS✅ Lipids can be used for energy storage in the form of fat in mammals and oil in plants. Lipids can be used as heat insulation as fat under the skin reduces heat loss. Lipids allow buoyancy as they are less dense than water and help some animals float in water. 3.2.7 - Compare the use of carbohydrates and lipids in energy storage. CORRECT ANSWERS✅ Carbohydrates and lipids can both be used as energy storage, however carbohydrates are normally used for short-term storage whereas lipids are used for long-term storage. Unlike lipids, carbohydrates are soluble in water. This makes carbohydrates easier to transport around the body (from and to storage). Also, carbohydrates are a lot faster by being more rapidly digested their energy is useful if the body requires energy. As for lipids, they are insoluble which makes them more difficult to transport however because they are insoluble, lipids do not have an effect on osmosis which prevents problems within the cells in the body. They also contain more energy per gram than carbohydrates that make lipids a lighter store compared to a store of carbohydrates equivalent in energy. Adhesion CORRECT ANSWERS✅ being attracted to other substances IB Biology HL Questions and answers Anion CORRECT ANSWERS✅ negatively charged ion Atom CORRECT ANSWERS✅ Basic unit of chemical element/smallest unit of matter Calcium CORRECT ANSWERS✅ the chemical element of atomic number 20, needed for survival of organisms Capillary Action CORRECT ANSWERS✅ ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to external forces like gravity. Eg. water uses its magnetism and adhesive/cohesive properties to pull water through stem of plant from roots to top Carbohydrate CORRECT ANSWERS✅ any large group of compounds occurring in foods and living tissues containing: sugars, starch, and cellulose. They contain hydrogen and oxygen in the same ratio as water (2:1) and can typically be broken down to release energy in the animal body. Carbon CORRECT ANSWERS✅ chemical element of atomic number 6, found in almost all living or formerly living matter. IB Biology HL Questions and answers Carboxyl CORRECT ANSWERS✅ of or denoting the acid radical COOH, present in most organic acids. The -COOH group where a carbon atom is doubly bonded to an oxygen atom and singly bonded to an OH group. Cation CORRECT ANSWERS✅ positively charged ion Cellulose CORRECT ANSWERS✅ insoluble substance that is the main constitute of plant cell walls and of vegetable fibers. It is a polysaccharide consisting of chains of glucose monomers. Chemical bond CORRECT ANSWERS✅ an electrical force linking atoms, creating molecules Chemical Formula CORRECT ANSWERS✅ representation of a substance using symbols for its constituent elements. Chitin CORRECT ANSWERS✅ fibrous substance consisting of polysaccharides and forming the major constituent in the exoskeleton of arthropods and walls of fungi. Cholesterol CORRECT ANSWERS✅ important constituent of cell membranes and precursors of other steroid compounds. IB Biology HL Questions and answers Glycerol CORRECT ANSWERS✅ has three hydrophilic hydroxyl groups that are responsible for its solubility in water and its hydroscopic nature Glycogen CORRECT ANSWERS✅ substance deposited in bodily tissue as a store of carbohydrates. It is a polysaccharide that forms glucose on hydrolysis Hydrocarbon CORRECT ANSWERS✅ a compound of hydrogen and carbon, such as any of those that are the chief components of petroleum and natural gas Hydrogen CORRECT ANSWERS✅ chemical element atomic number 1, the lightest chemical element Hydrogen bond CORRECT ANSWERS✅ a weak bond between two molecules resulting from an electrostatic attraction between a proton in one molecule and an electronegative atom in the other Hydrolysis Reaction CORRECT ANSWERS✅ molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism Hydrophilic CORRECT ANSWERS✅ having a tendency to mix with, dissolve in, or be wetted by water IB Biology HL Questions and answers Hydrophobic CORRECT ANSWERS✅ tending to repel or fail to mix with water Inorganic CORRECT ANSWERS✅ does not include carbon in its molecular structure Ionic Bond CORRECT ANSWERS✅ chemical bond in which one atom loses an electron to form a positive ion and the other atom gains an electron to form a negative ion Iron CORRECT ANSWERS✅ chemical element atomic number 26, ferrum, exists in wide range of oxidation states and is a necessary mineral for life Isomer CORRECT ANSWERS✅ each of the two or more compounds with the same formula but a different arrangement of atoms in the molecule and different properties. Lactose CORRECT ANSWERS✅ a sugar present in milk; disaccharide containing glucose and galactose units Lipid CORRECT ANSWERS✅ any of a class of organic compounds that are fatty acids in their derivatives and are insoluble in water but soluble in organic solvents. IB Biology HL Questions and answers Macromolecule CORRECT ANSWERS✅ a molecule containing a very large number of atoms, such as a protein, nucleic acid, or synthetic polymer. Maltose CORRECT ANSWERS✅ a sugar produced by the breakdown of starch, e.g., by enzymes found in malt and saliva. It is a disaccharide consisting of two linked glucose units Matter CORRECT ANSWERS✅ generally anything that has mass and volume. Typically includes atoms and other particles that have mass. Monomer CORRECT ANSWERS✅ a molecule that can be bonded to other identical molecules to form a polymer Monosaccharide CORRECT ANSWERS✅ any of the class of sugars (e.g., glucose) that cannot be hydrolyzed to give a simpler sugar Neutron CORRECT ANSWERS✅ a subatomic particle of about the same mass as a proton but without and electric charge, present in all atomic nuclei expect those of ordinary hydrogen IB Biology HL Questions and answers acids and are an essential part of all living organisms, esp. as structural components of body tissues. Proton CORRECT ANSWERS✅ stable subatomic particle occurring in all atomic nuclei, with a positive electric charge equal in magnitude to that of an electron, but of opposite sign. Ribose CORRECT ANSWERS✅ sugar of the pentose class that occurs widely in nature as a constituent of nucleosides and several vitamins and enzymes. Saturated CORRECT ANSWERS✅ consists of triglycerides containing no carbon- carbon double bonds Sodium CORRECT ANSWERS✅ the chemical element of atomic number 11, trace element that can affect the osmosis of water into the cell membrane Solute CORRECT ANSWERS✅ the minor component in a solution, dissolved in the solvent Solvent CORRECT ANSWERS✅ liquid in which a solute is dissolved to form a solution IB Biology HL Questions and answers Specific heat CORRECT ANSWERS✅ the heat required to raise the temperature of the unit mass of a given substance by a given amount Starch CORRECT ANSWERS✅ a polysaccharide that functions as a carbohydrate store and is an important constituent of the human diet Sterol CORRECT ANSWERS✅ any of a group of naturally occurring unsaturated steroid alcohols, typically waxy solids Sucrose CORRECT ANSWERS✅ a compound that is the chief component of cane or beet sugar Sulfur CORRECT ANSWERS✅ the chemical element of atomic number 16, a yellow combustible nonmetal Surface tension CORRECT ANSWERS✅ the tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area IB Biology HL Questions and answers Trace element CORRECT ANSWERS✅ a chemical element present only in minute amounts in a particular sample or environment. Required only in minute amounts by living organisms for normal growth. Trans CORRECT ANSWERS✅ denoting or relating to a molecular structure in which two particular atoms or groups lie on opposite sides of a given plane in a molecule, in particular denoting an isomer in which substituents at opposite ends of a carbon-carbon double bond are also on opposite sides of the bond Transparent CORRECT ANSWERS✅ allowing light to pass through so that objects can be distinctly seen Triglyceride CORRECT ANSWERS✅ an ester formed from glycerol and three fatty acid groups. Triglycerides are the main constituent of natural fats and oils, and high concentrations in the blood indicate an elevated risk of stroke. Unsaturated CORRECT ANSWERS✅ hydrocarbons that have double or triple covalent bonds between adjacent carbon atoms. Water CORRECT ANSWERS✅ two hydrogen bonded to one oxygen, and is the basis of the fluids of living organisms IB Biology HL Questions and answers Helicase CORRECT ANSWERS✅ catalyst enzyme in replication DNA or RNA Polymerase CORRECT ANSWERS✅ links the phosphate of newest nucleotides to the sugar of new nucleotides before it, covalent bond, and is polymer of nucleotides Semi-conservative CORRECT ANSWERS✅ when dividing, DNA reuses 1 strand in each molecule and 1 new strand Ligase CORRECT ANSWERS✅ enzyme in DNA joins Okazaki fragment Okazaki fragments CORRECT ANSWERS✅ fragments on the lagging strand Codon CORRECT ANSWERS✅ sequence of 3 bases on the mRNA. Each codes for an AA to be added to polypeptides in translation Anticodon CORRECT ANSWERS✅ complementary to codon on tRNA can make attachment to mRNA IB Biology HL Questions and answers Gene CORRECT ANSWERS✅ a distinct sequence of nucleotides forming part of a chromosome None Coding Sequence CORRECT ANSWERS✅ 3 codons/stop codon Human Genome Project CORRECT ANSWERS✅ has led us to understand that there are a number of recognizable patterns observed in DNA Start code/stop code CORRECT ANSWERS✅ first or last 3 codons of mRNA for an AA sequence in translation Loci CORRECT ANSWERS✅ the position of a gene or mutation of a chromosome Polypeptide CORRECT ANSWERS✅ compose a protein, synthesized by mRNA, sequence of AA Amino Acid CORRECT ANSWERS✅ simple organic compound containing both a carboxyl (COOH) and an amino (NH2) group Enzyme CORRECT ANSWERS✅ biological catalysts that speed up biochemical reactions IB Biology HL Questions and answers Spindle Fibers CORRECT ANSWERS✅ separates the chromosomes into daughter cells during cell division. It is part of the cytoskeleton in eukaryotic cells Cell Cycle CORRECT ANSWERS✅ series of events leading to the cell's division and replication Mitosis CORRECT ANSWERS✅ the process of nuclear division in a cell in steps of: prophase, metaphase, anaphase, telophase, cytokinesis Meiosis CORRECT ANSWERS✅ a type of cell division that results in two daughter cells each with half the chromosome number of the parent cell Cell phases CORRECT ANSWERS✅ prophase, metaphase, anaphase, telophase, cytokinesis Chromatin CORRECT ANSWERS✅ the material of which the chromosomes of organisms other than bacteria are composed. It consists of protein, RNA, and DNA. IB Biology HL Questions and answers recombination CORRECT ANSWERS✅ rearrangement of genetic material, especially by crossing over in chromosomes or by the artificial joining of segments of DNA from different organisms. DNA anatomy CORRECT ANSWERS✅ nucleotides in each strand are joined by covalent bonds, alternating sugar and phosphate molecules form a backbone for each strand, the 2 strands are held together by hydrogen bonds between nitrogenous bases, 2 strands in helix, contains: adenine, thymine, guanine, and cytosine in nitrogenous bases. Adenine bonds to Thymine and Guanine bonds to Cytosine. 3.3.1 Outline DNA nucleotide structure in terms of sugar (deoxyribose), base and phosphate. CORRECT ANSWERS✅ A nucleotide is made of the sugar deoxyribose, a base (which can be either adenine, guanine, cytosine or thymine) and a phosphate group. Below is a representation of a nucleotide. 3.3.2 - State the names of the four bases in DNA. CORRECT ANSWERS✅ Adenine, Thymine, Guanine, Cytosine 3.3.3 - Outline how DNA nucleotides are linked together by covalent bonds into a single strand. CORRECT ANSWERS✅ Nucleotides are linked to one another to form IB Biology HL Questions and answers a strand. A covalent bond forms between the sugar of one nucleotide and the phosphate group of another nucleotide. 3.3.4 - Explain how a DNA double helix is formed using complementary base pairing and hydrogen bonds. CORRECT ANSWERS✅ DNA is made up of two nucleotide strands. The nucleotides are connected together by covalent bonds within each strand. The sugar of one nucleotide forms a covalent bond with the phosphate group of another. The two strands themselves are connected by hydrogen bonds. The hydrogen bonds are found between the bases of the two strands of nucleotides. Adenine forms hydrogen bonds with thymine whereas guanine forms hydrogen bonds with cytosine. This is called complementary base pairing. 3.3.5 - Draw and label a simple diagram of the molecular structure of DNA. CORRECT ANSWERS✅ Without a picture here... Imagine the left of the ladder starting with a phosphate, then bonding covalently to a pentose sugar (deoxyribose) and then another phosphate. This continues down the ladder and on the other side of the ladder, the 3 prime starts the same way, only missing its first phosphate. The nucleotides, making half of the ladder, composed of: one phosphate covalently bonded to pentose sugar, which is also bonded to a nitrogenous base. On the other half of the ladder it will be the same, but with the corresponding nitrogenous base. If A and T are the nitrogenous bases, a double hydrogen bond will be used. If C and G are used, a triple hydrogen bond will be IB Biology HL Questions and answers used. The 5 prime will end in 3 prime and the 3 prime will end in 5 prime, making up for the lagging and leading. 3.4.1 - Explain DNA replication in terms of unwinding the double helix and separation of the strands by helicase, followed by formation of the new complementary strands by DNA polymerase. CORRECT ANSWERS✅ DNA Replication is semi-conservative as both of the DNA molecules produced are formed from an old strand and a new one. The first stage of DNA replication involves the unwinding of the double strand of DNA (DNA double helix) and separating them by breaking the hydrogen bonds between the bases. This is done by the enzyme helicase. Each separated strand now is a template for the new strands. There are many free nucleotides around the replication for which to bond to the template strands. The free nucleotides form hydrogen bonds with their complimentary base pairs on the template strand. Adenine will pair up with thymine and guanine will pair up with cytosine. DNA polymerase is the enzyme responsible for this. The new DNA strands then rewind to form a double helix. The replication process has produced a new DNA molecule which is identical to the initial one. 3.4.2 - Explain the significance of complementary base pairing in the conservation of the base sequence of DNA. CORRECT ANSWERS✅ Complementary base pairing is very important in the conservation of the base sequence of DNA. This is because adenine always pairs up with thymine and guanine always pairs up with cytosine. As DNA replication is semi-conservative (one old strand an d one new IB Biology HL Questions and answers Then the two amino acids on the two transfer RNA molecules form a peptide bond. The first transfer RNA then detaches from the ribosome and the second one takes its place. The ribosome moves along the messenger RNA to the next codon so that another transfer RNA can bind. Again, a peptide bond is formed between the amino acids and this process continues. This forms a polypeptide chain and is the basis of protein synthesis. Enzyme CORRECT ANSWERS✅ a substance produced by a living organism that acts as a catalyst to bring about a specific biochemical reaction. Active site CORRECT ANSWERS✅ a region or an enzyme that binds to a protein or other substance during a reaction Enzyme-substrate specificity CORRECT ANSWERS✅ the enzyme can only work for one substrate at a time pH CORRECT ANSWERS✅ a figure expressing the acidity or alkalinity of a solution on a logarithmic scale on which 7 is neutral, lower values are more acidic, and higher values are more alkaline. substrate concentration CORRECT ANSWERS✅ as the concentration of substrate increases, the rate of reaction also increases until the point of saturation occurs. IB Biology HL Questions and answers induced fit model CORRECT ANSWERS✅ enzymes are proteins that catalyze (i.e., increase the rate of) chemical reactions. in enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. If the substrate does not fit exactly into the active site in an enzyme, and the enzyme must work to fit with the substrate, this is induced fit. denaturation CORRECT ANSWERS✅ to unfold a protein or break it up, changing its usual 3D structure. Proteins can be denatured by chemical action, heat or even agitation of a protein solution. lactase CORRECT ANSWERS✅ an enzyme that catalyzes the hydrolysis of lactose to glucose and galactose lock and key model CORRECT ANSWERS✅ enzymes are proteins that catalyze (i.e., increase the rate of chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. coenzyme CORRECT ANSWERS✅ a nonprotein compound that is necessary for the functioning of an enzyme IB Biology HL Questions and answers activation energy CORRECT ANSWERS✅ the minimum quanitity of energy that the reacting species must possess in order to form an 'activated complex' or 'transition state' before proceeding to become products. lactose intolerance CORRECT ANSWERS✅ a genetic trait characterized by the absence of the enzyme lactase, which breaks down lactose, the main sugar in milk and other dairy products. transition state CORRECT ANSWERS✅ transition state speculation assumes, that during an alkali-containing reaction, the reactants have been initially altered into a magnitude activated passing from a singular to another state and afterwards they get converted into the last products. inhibitor CORRECT ANSWERS✅ a chemical compound that has the effect of blocking or slowing an enzymatic reaction allosteric interactions and site CORRECT ANSWERS✅ allosteric regulation is the regulation of an enzyme or other protein by binding an effector molecule at the protein's allosteric site (that is, a site other than the protein's active site) IB Biology HL Questions and answers Cell respiration CORRECT ANSWERS✅ cellular respiration is the process by which the chemical energy of "food" molecules is released and partially captured in the form of ATP ATP CORRECT ANSWERS✅ adenosine triphosphate: a nucleotide derived from adenosine that occurs in muscle tissue; the major source of energy for cellular reactions Glycolysis CORRECT ANSWERS✅ the breakdown of glucose by enzymes, releasing energy and pyruvic acid Pyruvate CORRECT ANSWERS✅ the product of glycolysis that enters into the mitochondria matrix to produce Acetyl-CoA, or it's used to produce lactic or alcohol fermentation in anaerobic conditions. Anaerobic CORRECT ANSWERS✅ production of ATP without oxygen builds up lactic acid. This is system is responsible for quick bursts of power and speed, but burns the fuel stored directly in your muscles creating lactic acid buildup. Lactate CORRECT ANSWERS✅ a metabolic intermediary produced (mainly) during intense exercise when the demand for energy in the muscles outstrips that which IB Biology HL Questions and answers an be produced by aerobic metabolism. The point at which lactate begins to accumulate is often referred to as the "lactate threshold" Ethanol CORRECT ANSWERS✅ anaerobic respiration leaves a lot of energy in the form of ethanol or lactate molecules that the cell cannot use and must excrete. carbon dioxide CORRECT ANSWERS✅ a heavy odorless gas formed during respiration and by the decomposition of organic substances; absorbed from the air by plants in photosynthesis. Mitochondrion CORRECT ANSWERS✅ mitochondria are sometimes described as "cellular power plants" because they generate most of the cell's supply of ATP, used as a source of chemical energy. In addition to supplying cellular energy, mitochondria are involved in other tasks such as: signaling, cell differentiation, cell death as well as the control of the cell cycle and cell growth. ADP CORRECT ANSWERS✅ adenosine diphosphate - contains 2 phosphate and is weaker than ATP because of its sub energy levels. Aerobic CORRECT ANSWERS✅ This process using oxygen provides cells with needed ATP. Byproducts are carbon dioxide and water in this process. IB Biology HL Questions and answers Oxidation/reduction CORRECT ANSWERS✅ any chemical reaction in which the transfer of electrons from one substance to another substance occurs. The substance losing electrons is oxidized and the substance gaining the electrons is reduced. Sometimes called "redox" Krebs Cycle CORRECT ANSWERS✅ the sequence of reactions by which most living cells generate energy during the process of aerobic respiration. It takes place in the mitochondria, consuming oxygen, producing carbon dioxide and water as waste products, and converting ADP to energy-rich ATP. Oxidative phosphorylation CORRECT ANSWERS✅ an enzymatic process in cell metabolism that synthesizes ATP from ADP. Electron-transport chain CORRECT ANSWERS✅ the third and final stage of glucose oxidation. A series of metabolic reactions that transport electrons from NAHD or FADH2 through a series of carriers resulting in ATP production. 3.7.1 Define Cell respiration CORRECT ANSWERS✅ Cell respiration is the controlled release of energy from organic compounds in cells to form ATP. IB Biology HL Questions and answers processes found in autotrophs, usually driven by photosynthesis, whereby carbon dioxide is changed into sugars. Biomass CORRECT ANSWERS✅ vegetation used as a fuel, or source of energy, especially if cultivated for that purpose. Total weight of plants. Cyanobacteria CORRECT ANSWERS✅ a division of microorganisms that are related to the bacteria but are capable of photosynthesis. They are prokaryotic and represent the earliest known form of life on the earth. Electromagnetic spectrum CORRECT ANSWERS✅ the entire range of light waves arranged according to their wavelength or the energy of their photons. Photoactivated CORRECT ANSWERS✅ process wherby something is prepared or excited for a subsequent reaction. Thylakoid, stoma, grana CORRECT ANSWERS✅ make up chloroplasts, where photosynthesis starts/ the matrix of a chloroplast, in which the grana are embedded/ the stacks of thylakoids embedded in the stoma of a chloroplast IB Biology HL Questions and answers Chemiosmosis CORRECT ANSWERS✅ An energycouplling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Most ATP synthesis in cell occurs by chemiosmos. Calvin Cycle CORRECT ANSWERS✅ The biochemical pathway used by photosynthesis and chemosynthetic organisms to fix CO2 and synthesize sugars Cyclic photophosphorylation CORRECT ANSWERS✅ the production of ATP using the energy of sunlight. Only two sources of energy are available to living organisms: sunlight and oxidation-reduction (redox) reactions. All organisms produce ATP, which is the universal energy currency of life. 3.8.1 State that photosynthesis involves the conversion of light energy into chemical energy. CORRECT ANSWERS✅ Chlorophyll traps light energy from the Sun and converts those photons into chemical energy. In the chloroplast, substrates of CO2 and H2O react with the photons absorbed from the Sun to make sugars and O2. Photosynthesis is observed in most often aquatic and terrestrial environments with light. At extreme altitudes, extremophiles can still photosynthesize. In exceedingly high temperatures, photosynthesis can be seen in geothermal active regions. IB Biology HL Questions and answers 3.8.2 State that light from the Sun is composed of a range of wavelengths (colours) - CORRECT ANSWERS✅ Light from the Sun is composed of a range of wavelengths. There is a visible spectrum of light ranging from a multitude of colors. When these colors are combined together they create the "white light" we associate with sunlight. The shortest of these wavelengths on the visible spectrum of light are blues, which give off the most energy. The longest wavelengths are reds, which give off the least energy in the visible spectrum of light. 3.8.3 State that chlorophyll is the main photosynthetic pigment CORRECT ANSWERS✅ Chlorophyll is the main photosynthetic pigment. This is where light energy is trapped and turned into chemical energy. The head of the molecule is polar and composed of a ring structure. At the heart of this ring structure is the inorganic ion magnesium. This is the light-trapping region of the chlorophyll molecule. The tail of the molecule is non polar and embeds itself in membranes in the chloroplast. There are other pigments, reds, yellows and browns but these are only usually seen in the experimental chromatography or in the autumnal colors of deciduous trees in a temperate climate. 3.8.4 Outline the differences in absorption of red, blue and green light by chlorophyll. - CORRECT ANSWERS✅ Chlorophyll can absorb red and blue light more than green. Chlorophyll cannot absorb green light and so instead reflects it making leaves look green. IB Biology HL Questions and answers distinct nucleus. Eukaryotes include all living organisms other than the eubacteria and archaebacteria. Gene CORRECT ANSWERS✅ basic unit of genetic information. Genes determine the inherited characters. Allele CORRECT ANSWERS✅ one variant form of a gene/marker at a particular locus. Genome CORRECT ANSWERS✅ - the collection of genetic information. Structural Genes CORRECT ANSWERS✅ are genes that create forming structures (in the body). Regulator Genes CORRECT ANSWERS✅ are genes that turn on and off processes (in the body). tRNA and rRNA genes CORRECT ANSWERS✅ tRNA genes help synthesize proteins and insert codons into the DNA. rRNA genes help synthesize bacteria, and sequencing these genes can help discover new bacteria. IB Biology HL Questions and answers base substitution mutation CORRECT ANSWERS✅ A type of mutation involving replacement or substitution of a single nucleotide base with another in DNA or RNA molecule. Transcription/Translation CORRECT ANSWERS✅ Transcription is the process of converting the genetic information stored in DNA to messenger RNA (mRNA). This is performed by RNA Polymerase in the nucleus of the cell (assuming the organism is eukaryotic). At this point the mRNA is comprised of exons and introns, and the introns are cut out with splicing machinery. Now the mRNA is exported from the nucleus into the cytoplasm where it meets the ribosome. The ribosome uses the information stored in the mRNA, along with transfer RNAs (tRNA) holding onto amino acids to create protein. This process is known as translation because you are translating from the language of nucleotides to the language of amino acids. Sickle-cell anemia CORRECT ANSWERS✅ Sickle-cell disease (SCD), or sickle-cell anaemia (or anemia; SCA) or drepanocytosis, is an autosomal recessive genetic blood disorder characterized by red blood cells that assume an abnormal, rigid, sickle shape. reduction division CORRECT ANSWERS✅ - In biology, meiosis (pronounced) is a process of reductional division in which the number of chromosomes per cell is cut in half. In animals, meiosis always results in the formation of gametes, while in other organisms it can give rise to spores. IB Biology HL Questions and answers diploid/haploid CORRECT ANSWERS✅ diploid is containing two complete sets of chromosomes from parents, while haploid only has one set of chromosomes from parents. homologous chromosomes CORRECT ANSWERS✅ Chromosomes that are paired during meiosis. Such chromosomes are alike with regard to size and also position of the centromere. They also have the same genes, but not necessarily the same alleles, at the same locus or location. meiosis CORRECT ANSWERS✅ is the process that transforms one diploid into four haploid cells. crossing over CORRECT ANSWERS✅ The exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring names and stages of cell division CORRECT ANSWERS✅ Prophase: The chromosomes condense and become visible, The centrioles form and move toward opposite ends of the cell ("the poles"), The nuclear membrane dissolves, The mitotic spindle forms (from the centrioles in animal cells), Spindle fibers from each centriole attach to each sister chromatid at the kinetochore. Metaphase: The Centrioles complete their migration to the poles. The chromosomes line up in the IB Biology HL Questions and answers 4.1.1 State that eukaryotic chromosomes are made of DNA and proteins. The names of the proteins (histones) are not required, nor is the structural relationship between DNA and the proteins. CORRECT ANSWERS✅ The chromosome is composed of 2 main molecules: DNA and proteins called histones. 4.1.2 Define gene, allele, and genome. Know the differences between structural genes, regulator genes and genes coding for tRNA and rRNA. CORRECT ANSWERS✅ Gene is a heritable factor that controls a specific characteristic. Allele is one specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene. Genome is the whole of the genetic information of an organism. 4.1.3 Define gene mutation. The terms point mutation or frameshift mutation will not be used. CORRECT ANSWERS✅ Changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. Radiation, viruses, transposons and mutagenic chemicals, as well as errors that occur during meiosis or DNA replication can cause this. 4.1.4 Explain the consequence of a base substitution mutation in relation to the processes of transcription and translation, using the example of sickle-cell anemia. CORRECT ANSWERS✅ Sickle cell anaemia is a genetic disease that affects red blood cells in the body. It is due to a mutation on the Hb gene which codes for a IB Biology HL Questions and answers polypeptide of 146 amino acids which is part of haemoglobin (haemoglobin is an important protein component in red blood cells). In sickle cell anaemia the codon GAG found in the normal Hb gene is mutated to GTG. This is called a base substitution mutation as adenine (A) is replaced by thymine (T). This means that when the mutated gene is transcribed, a codon in the messenger RNA will be different. Instead of the normal codon GAG, the messenger RNA will contain the codon GUG. This in turn will result in a mistake during translation. In a healthy individual the codon GAG on the messenger RNA matches with the anticodon CUC on the transfer RNA carrying the amino acid glutamic acid. However, if the mutated gene is present then GUG on the messenger RNA matches with the anticodon CAC on the transfer RNA which carries the amino acid valine. So the base substitution mutation has caused glutamic acid to be replaced by valine on the sixth position on the polypeptide. This results in haemoglobin S being present in red blood cells instead of the normal haemoglobin A. This has an effect on the phenotype as instead of normal donut shaped red blood cells being produced some of the red blood cells will be sickle shaped. As a result these sickle shaped red blood cells cannot carry oxygen as efficiently as normal red blood cells would. However, there is an advantage to sickle cell anemia. The sickle cell red blood cells give resistance to malaria and so the allele Hbs on the Hb gene which causes sickle cell anemia is quite common in parts of the world where malaria is found as it provides an advantage over the disease. 4.2.1 State that meiosis is a reduction division of a diploid nucleus to form haploid nuclei. CORRECT ANSWERS✅ Meiosis is a reduction division of a diploid IB Biology HL Questions and answers nucleus(2n) to form a haploid nucleus (n). The cell is in G1 of the interphase and has a total of 2 chromosomes, 2n=2. The S phase of the interphase is DNA replication.In G2 of the interphase the cell has two daughter chromatids per chromosome, the cell mass of DNA has doubled. Meiosis occurs in a series of phases similar to mitosis but with significant differences.The diploid cell has divided to form haploid gamete cells (n=1).The homologous pair of chromosomes has been separated One diploid cell which undergoes meiosis produces four haploid gametic cells. 4.2.2 Define homologous chromosomes. CORRECT ANSWERS✅ Homologous chromosomes are chromosomes with the same genes as each other, in the same sequence but do not necessarily have the same allele of those genes. 4.2.3 Outline the process of meiosis, including pairing of homologous chromosomes and crossing over, followed by two divisions, which results in four haploid cells. Limit crossing over to the exchange of genetic material between non-sister chromatids during prophase. Names of the stages are required. CORRECT ANSWERS✅ Meiosis is a form of cell division that produces gametes. It takes place in the reproductive organs and shows variation in how long the process occurs. Although meiosis can produce millions of gametes in a short period of time in comparison to mitosis in the body it is relatively rare. The stages of meiosis are shown below but begins with some diagrams about Interphase as a reminder. In the diagrams homologous pairs are shown in different IB Biology HL Questions and answers methods used to determine if an unborn child is suffering from a disease or abnormal condition. karyotyping: If cells from the foetus can be obtained they can be cultured and then examined. Karyotyping to determine if a genetic abnormality exists. e.g. Downs Syndrome. Amniocentesis and chorionic villus sampling are the two main methods of obtaining tissue samples for pre-natal diagnosis. Both techniques take advantage of the fact that embryonic membranes, chorion, amnion and placenta are both derived form the embryo not the mother. The cells of these membranes have exactly the same genotype / genome (DNA) as the embryo. 4.2.7 Analyze a human karyotype to determine gender and whether nondisjunction has occurred. Karyotyping can be done by using enlarged photographs of chromosomes. CORRECT ANSWERS✅ Karyotyping can be used to determine gender of a fetus and look for chromosome abnormalities such as non- disjunction. The gender can be deduced by looking at the sex chromosomes. Females will have two X chromosomes while males have one X and one Y. We can distinguish this on with karyotyping as the Y chromosome is smaller than the X. As for non-disjunctions we can see if a chromosome is missing or if their is an extra one by looking at the number of chromosomes. If There should only be two of each chromosome. Each 23 chromosomes should have a pair resulting in 46 chromosomes in total. For example, if we notice that there are three chromosomes 21 then we can conclude that a non-disjunction occurred. In this case, the non-disjunction results in Down's syndrome. (trisomy 21) IB Biology HL Questions and answers 10.1.1 Describe the behavior of the chromosomes in the phases of meiosis. CORRECT ANSWERS✅ Two divisions occure during meiosis, these are termed meiosis I and meiosis II. Each division involves the four stages of prophase, metaphase, anaphase and telophase. Meiosis I Prophase I ▪ Chromosomes coil up tightly and become visible under a light microscope ▪ Homologous chromosomes pair up and crossing over occures (the point of cross over is known as the chiasma) ▪ Nuclear membrane disintgrates and the centrioles travel to the poles of the cell Metaphase I ▪ Microtubules form a spindle and the spindle fibers attach to the centromeres of the chromosomes ▪ Pairs of homologous chromosomes align along the equator Anaphase I ▪ Spindle fibers shorten pulling paired homologous chromosomes in opposite directions ▪ Paired homologous chromosomes are seperated and pulled to opposite poles so that each pole contains one chromosome of each pair. Telophase I IB Biology HL Questions and answers ▪ A nuclear membrane forms around the chromosomes at each pole and chromosomes uncoil ▪ The cell undergoes cytokinesis to form two daughter cells ▪ Forms two haploid cells ▪ At the end of telophase I the cells may enter a short interphase period or proceed directly to meiosis II DNA is not replicated Meiosis II Prophase II ▪ Chromosomes coil up again ▪ Centrioles move to the cell poles ▪ Nuclear membrane disintergrates Metaphase II ▪ Spindle fibers attach to the the centromeres ▪ Chromosomes align along the equator Anaphase II ▪ Spindle fibers shorten ▪ Centromeres split ▪ Chromatids of each chromosome travel to opposite poles Telophase II