OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS, Exams of Nursing

Download OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS and more Exams Nursing in PDF only on Docsity! OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . enzyme- substrate complex - CORRECT ANSWERS When the substrate and the enzyme bind together and the reaction takes place. enzyme- product complex - CORRECT ANSWERS The products are formed in this complex activation energy - CORRECT ANSWERS The added energy required before a reaction can take place lock and key hypothesis - CORRECT ANSWERS The shape of the active site and the specific substrate are complementary Induced fit model - CORRECT ANSWERS The active site changes shape as the substrate approaches, becoming complementary- allowing the reaction to take place denatured - CORRECT ANSWERS Loss of tertiary structure. Loss of active site. Loss of function optimum temperature - CORRECT ANSWERS Temperature at which an enzyme has maximum rate of activity Thermophiles - CORRECT ANSWERS Organisms adapted to very hot conditions have extra bonds in their enzymes to prevent denaturation Vmax - CORRECT ANSWERS Maximum initial rate of reaction Competitive inhibition - CORRECT ANSWERS An inhibitor that binds to the active site of the enzyme, thus competing with the substrate and reducing the rate of reaction Non-competitive inhibition - CORRECT ANSWERS An inhibitor that binds to the enzyme away from the active site reducing the rate of reaction OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . End- product inhibition - CORRECT ANSWERS The product at the end of series of reactions inhibits the enzyme at the start of the series cofactor - CORRECT ANSWERS Non- protein components necessary for effective action of an enzyme coenzyme - CORRECT ANSWERS an organic molecule that acts as a cofactor precursor activation - CORRECT ANSWERS Inactive enzymes that require a cofactor before they produce the tertiary structure required to catalyse a reaction anabolic - CORRECT ANSWERS A reaction that builds a bigger molecule from smaller ones e.g. protein synthesis catabolic - CORRECT ANSWERS A reaction that breaks down a big molecule into smaller ones Amino acid - CORRECT ANSWERS Protein monomer, composed of an amine group, carboxyl group and a variable R group attached to a central carbon atom. carboxyl group - CORRECT ANSWERS An organic acid goup amine group - CORRECT ANSWERS A nitrogen atom with 2 hydrogen atoms attached R group - CORRECT ANSWERS A chemical group that is different in each of the 20 different amino acids found in nature Condensation reaction between amino acids - CORRECT ANSWERS When the carboxyl group of one amino acid reacts with the amine group of another amino acid, water is produced and a dipeptide is formed dipeptide - CORRECT ANSWERS the condensation product/ residue of 2 amino acids reacting together polypeptide - CORRECT ANSWERS A polymer made of many amino acids OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Hemizygous - CORRECT ANSWERS Having a single copy of a gene instead of the normal two. For example, if there is heterozygous inheritance of the sex chromosomes, XY. Variation - CORRECT ANSWERS The range of differences in characteristics between organisms Phencopy - CORRECT ANSWERS When environmental conditions alter the phenotype to resemble the effects of genotypic change Discontinuous variation - CORRECT ANSWERS Variation where there are 2 or more distinct categories with no intermediates. Determined by a small number of genes with little or no environmental influence. Continuous variation - CORRECT ANSWERS Variation where there are two extremes and all possible intermediate forms. Determined by many genes (polygenic) and influenced by the environment. Etiolation - CORRECT ANSWERS When plants grow abnormally long and spindly because they are not getting enough light. Chlorosis - CORRECT ANSWERS When plants don't produce enough chlorophyll and turn yellow eg due to lack of magnesium in the soil. Artificial selection - CORRECT ANSWERS When humans select which individuals in a population to breed together in order to get desirable traits. Stabilising selection pressure - CORRECT ANSWERS Factor that reduces the range of phenotypes by selecting against individuals with the extreme phenotype. Selection pressure - CORRECT ANSWERS A factor that gives a greater chance of surviving to some members of the population than others e.g. moth camouflage Stabilising selection - CORRECT ANSWERS Types of selection that operates against the extremes of the range of phenotypes so the population remains the same over time. OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Directional selection - CORRECT ANSWERS Factor that selects individuals with an extreme phenotype of a range of phenotypes so the population changes over time. Genetic drift - CORRECT ANSWERS The increase or decrease in the frequency of alleles as a result of chance events. Carrying capacity - CORRECT ANSWERS The maximum population size of a species that a particular habitat can support over time. Gene pool - CORRECT ANSWERS The sum of all the alleles in a population at a given time. Genetic bottleneck - CORRECT ANSWERS An event, such as a natural disaster, that causes a large reduction in the size of a population. Founder effect - CORRECT ANSWERS What happens when a small number of individuals start a new population and there is only a small number of alleles. Species - CORRECT ANSWERS A group of similar organisms that can reproduce to give fertile offspring. Allopatric speciation - CORRECT ANSWERS Populations become geographically isolated and, as a result of natural selection, form new species. Sympatric speciation - CORRECT ANSWERS Formation of a new species without geographical isolation. Reproductive isolation - CORRECT ANSWERS Populations cannot breed successfully together because of mechanical changes or behavioral changes. Geographical isolation - CORRECT ANSWERS A physical barrier such as a mountain range or a desert that prevents gene flow between populations. Natural selection - CORRECT ANSWERS The mechanism of evolution.It is the survival of individuals in a population to reproduce and pass on their alleles to the next generation. OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Restriction endonuclease - CORRECT ANSWERS Enzyme that cuts DNA molecules at a specific sequence of bases. Palindromic recognition site - CORRECT ANSWERS The specific sequence of bases where a restriction enzyme will cut. The sequence of bases reads the same in opposite directions. DNA ligase - CORRECT ANSWERS Enzyme which joins sections of DNA together, catalysing condensation reaction. Sticky ends - CORRECT ANSWERS When a restriction endonuclease cuts DNA and leaves unpaired bases. Vector DNA - CORRECT ANSWERS Used to transfer DNA into a cell eg a plasmid or bacteriophage. Plasmid - CORRECT ANSWERS Small, circular molecule of DNA used to transfer DNA into cells. Bacteriophage - CORRECT ANSWERS A virus that infects a bacterium and can be used as a DNA vector. Electroporation - CORRECT ANSWERS An electric field used to increase the permeability of a bacterial cell membrane so that it takes up plasmids more readily. Agrobacterium tumefaciens - CORRECT ANSWERS A bacterium used to introduce genes into a plant cell in order to produce genetically modified plants. Technology transfer - CORRECT ANSWERS The sharing of knowledge, skills and technology. Somatic gene therapy - CORRECT ANSWERS Altering the alleles in body cells in order to treat a genetic disorder. Germ line gene therapy - CORRECT ANSWERS Altering the alleles in sex cells/zygotes. (Currently illegal in humans) OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Transcription Factors - CORRECT ANSWERS A protein that binds to DNA and switches a gene on or off by increasing or decreasing the rate of transcription Promoter - CORRECT ANSWERS A DNA sequence (located before the structural genes in an operon) that RNA polymerase binds to. Activator - CORRECT ANSWERS A transcription factor that increases the rate of transcription Repressor - CORRECT ANSWERS A transcription factor that decreases the rate of transcription Operon - CORRECT ANSWERS A section of DNA that contains structural genes that are all transcribed together, control elements and sometimes a regulatory gene. Regulatory gene - CORRECT ANSWERS A gene that gives rise to a transcription factor. Structural gene - CORRECT ANSWERS A gene that codes for a polypeptide (protein) The lac operon - CORRECT ANSWERS A gene in E.coli that codes for the production of enzymes that break down lactose. This gene is only turned on in the presence of lactose and is therefore self- regulating. Intron - CORRECT ANSWERS A section of DNA that doesn't code for an amino acid Exon - CORRECT ANSWERS A section of DNA that codes for amino acids Splicing - CORRECT ANSWERS The process that changes primary mRNA into mature mRNA by removing the introns and rejoining the exons together. cyclic AMP (cAMP) - CORRECT ANSWERS A molecule that activates proteins inside cells by altering their tertiary structures. Hox genes - CORRECT ANSWERS Genes that encode proteins which control body plan development OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Homeobox sequence - CORRECT ANSWERS A sequence in a homeotic gene that codes for the homeodomain. Homeodomain - CORRECT ANSWERS Part of a transcription regulatory protein that binds to DNA, allowing the protein to act as a transcription factor. Apoptosis - CORRECT ANSWERS A highly controlled process by which cells are broken down. part of programmed cell death. Mutation - CORRECT ANSWERS Any change in the DNA base (nucleotide) sequence Deletion mutation - CORRECT ANSWERS A mutation where one or more bases are removed and may result in a frame shift. Insertion mutation - CORRECT ANSWERS A mutation where one or more bases are inserted and may result in a frame shift Substitution mutation - CORRECT ANSWERS A mutation where one or more bases are replaced by another base. Frame shift mutation - CORRECT ANSWERS This occurs when a deletion or insertion mutation occurs in a gene. The number of bases in the entire sequence changes, causing a shift in all the base triplets that follow. Neutral mutation - CORRECT ANSWERS A mutation that does not affect the phenotype of the organism. Post Translation Level Control - CORRECT ANSWERS Modify the protein after it is made by chemical modification or cleavage Meristem - CORRECT ANSWERS an undifferentiated, growing region of a plant that is constantly undergoing cell division and differentiation OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Vegetative propagation - CORRECT ANSWERS A form of asexual reproduction in which plants produce genetically identical offshoots (clones) of themselves, which then develop into independent plants. Cloning - CORRECT ANSWERS Process that produces a group of genetically identical organisms. Micropropagation - CORRECT ANSWERS Using sterile plant tissue grown to form a callus culture from which many new plants are grown by separation and growth of small parts of the callus. Artificial embryo twinning - CORRECT ANSWERS Method of cloning animals by separating the individual cells of an early embryo to form a number of genetically identical embryos. Somatic cell nuclear transfer (SCNT) - CORRECT ANSWERS Involves removing the nucleus of an unfertilized egg cell, replacing it with the nucleus of a "somatic cell" (a skin, heart, or nerve cell, for example), and stimulating this cell to begin dividing. It is then implanted into a surrogate mother. Therapeutic cloning - CORRECT ANSWERS The cloning of human cells by nuclear transplantation for therapeutic purposes, such as the generation of embryonic stem cells to treat disease. Embryonic stem cell - CORRECT ANSWERS An undifferentiated cell, taken from an embryo that is able to undergo mitosis and has the potential to give rise to many various other cell or tissue types Non reproductive cloning - CORRECT ANSWERS Use of stem cells to generate replacement tissues and organs which may be used to treat disease reproductive cloning - CORRECT ANSWERS a method to clone an adult using nuclei from some of its somatic cell mitosis - CORRECT ANSWERS A type of cell division that results in two daughter cells that are genetically identical to the parent nucleus, typical of ordinary tissue growth. callus - CORRECT ANSWERS A mass of dividing, undifferentiated cells at the cut end of a shoot. tissue culture - CORRECT ANSWERS Using small groups of cells from a plant to make new plants. OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . intracellular enzymes - CORRECT ANSWERS Enzymes that catalyse reactions inside of the cell extracellular enzymes - CORRECT ANSWERS What term describes enzymes that microorganisms produce and release outside of the cell? Biotic factor - CORRECT ANSWERS A living factor that influences populations in an ecosystem Abiotic Factor - CORRECT ANSWERS A non living factor that influences populations. Ecosystem - CORRECT ANSWERS Habitat and community within a fixed area Biomass - CORRECT ANSWERS Mass of living material per unit area. Efficiency of biomass transfer - CORRECT ANSWERS Biomass of previous trophic level divided by biomass of current trophic level then x 100 Saprobiotic nutrition - CORRECT ANSWERS Fungi and bacteria that produces enzymes within the cell which are then transported outside of the cell (extracellular) to digest biochemicals. They then absorb the products. Nitrogen fixation - CORRECT ANSWERS Taking nitrogen gas and incorporating it into a nitrogen compound. Rhizobium - CORRECT ANSWERS Found in root nodules. Fix nitrogen into ammonia. Azotobactor - CORRECT ANSWERS Free living Nitrogen fixing bacteria Ammonification - CORRECT ANSWERS Decomposition of proteins in dead organic matter to release ammonia. Nitrification - CORRECT ANSWERS Turning ammonia into nitrate. OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Nitrosomanas - CORRECT ANSWERS Bacteria involved in oxidation of ammonia into nitrites Nitrobacter - CORRECT ANSWERS Bacteria involved in the oxidation of Nitrites to nitrates. Denitrification - CORRECT ANSWERS Denitrifying bacteria convert nitrates into nitrogen gas ( anaerobic) Primary succession - CORRECT ANSWERS Sequence of plants colonizing a newly formed environment. e.g. on newly formed volcanic rock. Secondary succession - CORRECT ANSWERS If an environment has already undergone succession and an event e.g. tree fall removes the climax community and succession starts again - not necessarily from the beginning. Deflected succession - CORRECT ANSWERS Something prevents the process reaching climax community such as grazing. the result is a plagioclimax community. Taxonomic hierarchy - CORRECT ANSWERS Classification system based on large groups being subdivided in to smaller groups that do not overlap. Phylogeny - CORRECT ANSWERS The study of evolutionary relationships between organisms. Phylogenetic tree - CORRECT ANSWERS Diagram representing the evolutionary relationships of organisms with a common ancestor. Cladistics - CORRECT ANSWERS Classification system based on an organisms evolutionary history. Domain Bacteria - CORRECT ANSWERS A domain made up of prokaryotes. Contains the Kingdom Eubacteria. They lack a nucleus and membrane bound organelles. They have a single circular strand of DNA and small 70s ribosomes. OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Domain - CORRECT ANSWERS A taxonomic category above the kingdom level. The three domains are Archaea, Bacteria, and Eukarya. Domain Archaea - CORRECT ANSWERS Domain containing single-celled, simple organisms, genetically distinct from bacteria, often thriving in extreme environmental conditions. Domain Eukarya - CORRECT ANSWERS Domain of all organisms whose cells have membrane bound organelles including nuclei. The domain includes protists, plants, fungi, and animals. Kingdom - CORRECT ANSWERS Large taxonomic group, consisting of closely related phyla Kingdom Prokaryotae - CORRECT ANSWERS Bacteria (most recently divided into two kingdoms: Kingdom Eubacteria and Kingdom Archaebacteria/Archaea) Kingdom Protoctista - CORRECT ANSWERS Includes a diverse collection of single-celled and multicelled organisms that have a nucleus. Includes algae. Kingdom Fungi - CORRECT ANSWERS Heterotrophic organisms, they secrete enzymes and digest food outside of their bodies then absorb the nutrients, are multicellular, and have cell walls of chitin and often form mulitnucleate hypae. Kingdom Plantae - CORRECT ANSWERS Multicellular eukaryotes that photosynthesize (photoautotrophs) and have cell walls made of cellulose. Kingdom Animalia - CORRECT ANSWERS A kingdom a of multicellular, heterotrophic eukaryotic organismsins that are free-moving, lack cell walls Binomial nomenclature - CORRECT ANSWERS A system for giving each organism a two-word scientific name that consists of the genus name (initial letter written with a capital letter) followed by the species name (Lower case). Written in italics/underlined. Species - CORRECT ANSWERS A group of similar organisms that can breed and produce fertile offspring. OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Clonal selection - CORRECT ANSWERS the process during the immune responses when specific B cells /T cells interact with antigens displayed by APC Clonal expansion - CORRECT ANSWERS Mitotic division of a small group of identical cells after clonal selection. Cells differentiate into memory /plasma cells Phagocytosis - CORRECT ANSWERS process in which neutrophils and macrophages engulf and digest microorganisms and cellular debris. Third line of defence - CORRECT ANSWERS A response to invading specific pathogens involving lymphocytes and antibodies Callose - CORRECT ANSWERS A polysaccharide made by plant cells in defence against attack by pests and pathogens Communicable disease - CORRECT ANSWERS Diseases caused by a pathogen that can be transmitted from one host organism to another Vector - CORRECT ANSWERS An organism that transfers a pathogen from an infected host to an uninfected host. First line of defence - CORRECT ANSWERS Physical and chemical defences that prevent entry of pathogens Inflammation - CORRECT ANSWERS a reaction to injury or infection.Excess tissue fluid forms (swollen). Histamines are released and arterioles dilate ( red). Phagocytes squeeze out of capillaries and engulf pathogens( hot ) Cytokines - CORRECT ANSWERS Small protein molecules that act as cell-signalling molecules Plasma cell - CORRECT ANSWERS An activated B cell that makes and releases antibodies during an immune response OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . T helper cell - CORRECT ANSWERS Type of lymphocyte that coordinates the immune response using chemical signals such as interleukins Agglutination - CORRECT ANSWERS The clumping together of pathogens using antibodies Opsonisation - CORRECT ANSWERS the marking of pathogens by antibodies to facilitate phagoctosis Antibiotics - CORRECT ANSWERS Any substance produced by a microorganism that can harm or kill another microorganisms Autoimmune disease - CORRECT ANSWERS A disease in which the immune system attacks the organisms own cells antibiotic resistance - CORRECT ANSWERS Resistance evolving rapidly in many species of prokaryotes due to overuse of antibiotics, especially in agriculture. Neutralisation - CORRECT ANSWERS Antibodies - Main role = Blood clotting - CORRECT ANSWERS platelets,cells and fibres form a mesh at a cut preventing blood loss and entry of pathogens. Scab forms Expulsive reflex - CORRECT ANSWERS sneezing,coughing,vomiting antigen presenting cell - CORRECT ANSWERS these are cells that recognizes antigens and brings them into the cell by phagocytosis; the cells then breaks up the antigen and present them on the cell surface membrane plasmodesma - CORRECT ANSWERS A microscopic channel through plant cell walls, connecting the cytoplasm of two cells. These are lined with plasma membrane. (pl: plasmodesmata) Accuracy - CORRECT ANSWERS How close a measurement is to the true value. However, the true value may not be known OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Anomaly - CORRECT ANSWERS All results show variation. This describes a result that lies beyond this variation. Confidence - CORRECT ANSWERS Is a qualitative judgement expressing the extent to which a conclusion is justified by the quality of the evidence. Error (of measurement) - CORRECT ANSWERS The Difference between the recorded value and the true value. Precision - CORRECT ANSWERS The closeness of agreement between independent measurements obtained under the same conditions. It depends only on the distribution of random errors (i.e. the spread of measurements) and does not relate to the true value. Repeatability - CORRECT ANSWERS The precision obtained when measurement results are produced over a short timescale by one person using the same equipment in the same place. Reproducibility - CORRECT ANSWERS Is the precision obtained when measurement results are produced over a wider timescale by different people using equivalent equipment in different places. Resolution - CORRECT ANSWERS Is the smallest change in the quantity being measured that can be detected by an instrument. Uncertainty - CORRECT ANSWERS An estimate as to where the true value actually lies. This is normally expressed as a range of values such as 44.0 ± 0.4. Validity - CORRECT ANSWERS A description of a measurement of whole investigation to explain if it measures what it set out to measure. i.e. confounding variables have not significantly affected the result and it has been referenced to a control experiment. Bar chart - CORRECT ANSWERS A graph used to display discontinuous discrete data e.g. blood group. The bars do not touch Line graph - CORRECT ANSWERS A graph used to display continuous data e.g. height. OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Monoculture - CORRECT ANSWERS Growing the same crop (or farming the same species of livestock) over a large area for several years. Reduces species and habitat diversity. Eutrophication - CORRECT ANSWERS When fertilisers cause water pollution. Keystone species - CORRECT ANSWERS A species that contributes more to an ecosystem than it's size or number may suggest. These are usually apex predators at the top of the food web. Flagship species - CORRECT ANSWERS A species that boosts ecotourism for a particular area. People will travel especially to see it in the wild e.g. elephants in Africa or Giant Panda's in China. In situ conservation - CORRECT ANSWERS The protection and maintenance of an area so that species can continue to live in their original habitat. UNESCO - CORRECT ANSWERS United Nations Educational, Scientific and Cultural Organisation Ex situ conservation - CORRECT ANSWERS Removal of a species to a protected place that is not its normal habitat. Seed bank - CORRECT ANSWERS A long term store of germplasm in the form of seeds. Collections of seeds are dried and then stored at temperatures near -20C CBD - CORRECT ANSWERS Convention of Biological Diversity (1992/3) CITES - CORRECT ANSWERS Convention on International Trade in Endangered Species (of Wild Fauna and Flora) 1975. Tissue - CORRECT ANSWERS A group of cells (plus any extracellular material they secrete) that are specialised to work together to carry out a particular function. Organ - CORRECT ANSWERS A group of different tissues that work together to carry out a particular function. OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Organ system - CORRECT ANSWERS A group of organs that work together to carry out a particular function. Totipotent - CORRECT ANSWERS These cells are unspecialised and are able to divide and give rise to any type of body cell. They include the zygote and the very early embryo. Pluripotent - CORRECT ANSWERS These cells (embryonic stem cells) are unspecialised and are able to divide and give rise to any type of body cell but not the extra-embryonic membranes. Multipotent - CORRECT ANSWERS These cells (adult stem cells) can divide and give rise to a small number of cell types. Stem cells - CORRECT ANSWERS Cells that are able to divide and give rise to a number of different cell types. They may be pluripotent (embryonic stem cells) or multipotent (adult stem cells). Differentiation - CORRECT ANSWERS Process by which unspecialised cells become specialised and adapted for their particular function by the switching on and off of different genes. Meristem - CORRECT ANSWERS That part of plant where mitosis takes place and plants grow. Cambium - CORRECT ANSWERS The meristematic cells that divide to produce new xylem and phloem when a plant increases in girth. All tests. - CORRECT ANSWERS Add sample to a test tube and crush with a stirring rod. Proteins - CORRECT ANSWERS Add sodium hydroxide. Trickle dilute copper sulphate down the wall of the test tube. A positive result is from blue to purple. Lipids - CORRECT ANSWERS Add ethanol. Mix well. Decant supernatant into a test tube of water. The water will turn from clear to a milky white emulsion for a positive result. Starch - CORRECT ANSWERS Add iodine. Colour changes from brown to deep blue/black. OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Reducing sugars. - CORRECT ANSWERS Add excess benedicts solution. Heat to above 80 degrees for 5 minutes. A positive result will result in a colour change from blue to green, brown and finally brick red. Quantitative analysis of reducing sugars. - CORRECT ANSWERS by comparison of colour change if both samples are tested in an identical manner. An improvement is to let the sample settle then use a colourometer to measure the density of colour in the supernatant. More reducing sugar will leave less blue colour of the benedicts in solution. Non reduding sugar. - CORRECT ANSWERS After negative for the reducing sugar. Add HCl and heat at 80 degrees for 5 min. Cool. Neutralise with excess solid sodium hydrogen carbonate. Repeat benedicts test. Positive will result in colour change from blue to green/ brown / brick red. active site - CORRECT ANSWERS An area within the tertiary structure of the enzyme able to bind to the substrate substrate - CORRECT ANSWERS The molecule(s) that react in the presence of the enzyme biological catalyst - CORRECT ANSWERS Increases the rate of a chemical reaction. Works under normal biological conditions of temperature and pressure. Not used up in the reaction Biuret test for proteins - CORRECT ANSWERS Add NaOH to a protein sample, add weak CuSO4 and a purple solution forms alpha helix - CORRECT ANSWERS H bonds form between amino acids in the polypeptide pulling it into a spiral shape. beta pleated sheet - CORRECT ANSWERS Forms where polypeptide chains lie parallel to each other. Held together by H bonds OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Extrinsic protein - CORRECT ANSWERS Proteins only found on the inner OR outer surface of the bilayer Channel protein - CORRECT ANSWERS Transmembrane proteins that transport soluble ions down a concentration gradient through a tunnel through the protein carrier protein - CORRECT ANSWERS Transmembrane proteins that transport water soluble and large molecules by binding to the molecule, changing shape and releasing the molecule on the other side of the membrane Receptor - CORRECT ANSWERS A transmembrane molecule that binds to signaling molecule (has a complementary shape) e.g. a hormone and triggers a specific change inside the cell Cholesterol - CORRECT ANSWERS One of the steroids group of lipids. It possess hydrophilic and hydrophobic regions. Cholesterol is an important component in cell membrane structure water potential - CORRECT ANSWERS the tendency(potential ) of water molecules to move.Distilled water has the highest water potential = 0kPa. Solute reduces the potential of water molecules to move. Diffusion - CORRECT ANSWERS the net movement of particles from a high concentration to a low concentration until equilibrium is reached isotonic solution - CORRECT ANSWERS A solution with the same water potential as the cells/ tissue it surrounds Hypotonic solution - CORRECT ANSWERS A solution with a less negative water potential than the cells/ tissue it surrounds Hypertonic solution - CORRECT ANSWERS A solution with a more negative water potential than the cells/ tissue it surrounds Turgid - CORRECT ANSWERS Applies to plants cells that have taken in the maximum volume of water they can from a hypotonic solution OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Plasmolysis and Flacid - CORRECT ANSWERS Applies to plant cells that have lost water to a hypertonic solution, causing the cytoplasm to shrink Osmosis - CORRECT ANSWERS The movement of water from a higher water potential to a more negative water across a partial permeable membrane. It must always have a direction e.g. osmosis from the cell cytoplasm to the surrounding solution. Prokaryotic cell - CORRECT ANSWERS A group of organisms that lack a true nucleus and other membrane bound organelles. e.g. bacteria and archaea. Eukaryotic cell - CORRECT ANSWERS Cells containing nucleus. e.g. animal or plant cells. Nucleus - CORRECT ANSWERS Surrounded by the nuclear envelope, it contains the DNA. Mitochondrion - CORRECT ANSWERS Membrane bound organelle with a folded inner membrane. The site of aerobic respiration. Chloroplast. - CORRECT ANSWERS A membrane bound organelle containing thylakoid membranes. The site of photosynthesis. Smooth Endoplasmic reticulum - CORRECT ANSWERS Membrane tubes. The site of lipid synthesis and processing. Rough Endoplasmic Reticulum. - CORRECT ANSWERS Membrane tubes with ribosomes embedded. The site of protein synthesis. Golgi apparatus. - CORRECT ANSWERS Membrane bound flattened sacks. It processes and packages lipids and proteins making vesicles. Cytoskeleton. - CORRECT ANSWERS Made of microtubules and microfilaments. It supports and strengthens the cell and allows transport within the cell. Microtubules. - CORRECT ANSWERS Part of the cytoskeleton. Protein cylinders. OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Microfilaments. - CORRECT ANSWERS Part of the cytoskeleton. Protein fibers. Lysosome. - CORRECT ANSWERS A membrane vesicle that contains digestive enzymes for digesting damaged organelles or the cell itself. Ribosome. - CORRECT ANSWERS A small organelle made of protein that can be free or bound to RER. Site of protein synthesis. Cristae - CORRECT ANSWERS The inner folds of the mitochondria. Intrinsically involved in the reactions of aerobic respiration. Microvilli - CORRECT ANSWERS Folding of the cell surface membrane to increase the surface area of the cell. Plasma membrane - CORRECT ANSWERS Made of a phospholipid bilayer. Regulates movement of molecules in or out of the cell. Cell wall - CORRECT ANSWERS Made of a mesh of cellulose. Strengthens plant cells. Centrioles - CORRECT ANSWERS Microtubules involved in the separation of chromosomes. Cilia - CORRECT ANSWERS Hair like structures on the surface of some animal cells. They have 9 microtubules round the edge and 2 in the middle which allow movement. Flagellum - CORRECT ANSWERS Found on the surface of some eukaryotic cells. Longer than cilia, they also have the 9 plus 2 structure of microtubules. They can propel a cell e.g. a sperm. polar molecule - CORRECT ANSWERS A molecule with regions of negative an positive charge covalent bond - CORRECT ANSWERS Strong bond formed by the sharing of electrons between atoms to give a stable electronic configuration OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . 1,6 glycosidic bond - CORRECT ANSWERS Glycosidic bond formed between carbon1 of first monosaccharide and carbon 6 of the second monosaccharide Starch - CORRECT ANSWERS Complex energy storage polysaccharide molecule in plants. Made up of Amylose and Amylopectin Test for a Reducing sugar - CORRECT ANSWERS Add Benedict's solution and heat. Brick red precipitate forms. Test for Non- Reducing sugar - CORRECT ANSWERS If reducing sugar test result is negative, then heat with hydrochloric acid, neutralise with sodium bicarbonate then re test using Benedict's solution. Brick red precipitate forms. Nucleotide - CORRECT ANSWERS Monomer from which DNA and RNA is made, consisting of a pentose sugar, a phosphate group and a nitrogenous base. Also forms ATP. Phosphodiester bond - CORRECT ANSWERS Bond that forms between the phosphate group of one nucleotide and the pentose sugar of the next nucleotide in a CONDENSATION reaction. Complementary base pairing - CORRECT ANSWERS Arrangement of nitrogenous bases. Adenine and thymine are held together by 2 hydrogen bonds. Guanine and cytosine are held together by 3 hydrogen bonds. Purine - CORRECT ANSWERS Double ring nitrogenous bases....Adenine and Guanine. Pyrimidine - CORRECT ANSWERS Single ring nitrogenous bases.....Thymine, Cytosine and Uracil. Polynucleotide - CORRECT ANSWERS Chain of nucleotides joined together by phosphodiester bonds made as a result of condensation reactions. Gene - CORRECT ANSWERS A sequence of DNA nucleotides that codes for the primary structure of a polypeptide. OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Allele - CORRECT ANSWERS An alternative version of a gene. Primary structure - CORRECT ANSWERS The sequence of amino acids in a polypeptide/protein. DNA triplet - CORRECT ANSWERS 3 DNA bases that code for one amino acid. Universal genetic code - CORRECT ANSWERS The same specific base triplets code for the same amino acid in all organisms. Degenerate genetic code - CORRECT ANSWERS More than one DNA triplet or codon codes for the same amino acid. Non-overlapping genetic code - CORRECT ANSWERS Each base forms part of only one triplet.. Codon - CORRECT ANSWERS 3 bases on the mRNA molecule, that codes for one amino acid. Transcription - CORRECT ANSWERS First stage of protein synthesis when a gene is copied and mRNA is produced. Template strand/antisense strand - CORRECT ANSWERS The DNA strand that is copied in transcription. Translation - CORRECT ANSWERS Second stage of protein synthesis when amino acids are joined together at the ribosomes. RNA polymerase - CORRECT ANSWERS The enzyme that joins free nucleotides together to form mRNA in transcription. Anticodon - CORRECT ANSWERS 3 bases on the tRNA molecule, that is complementary to the codon on the mRNA. Mitosis - CORRECT ANSWERS Type of cell division where a cell divides to produce two genetically identical daughter cells. OCR A LEVEL BIOLOGY PAPER 2 EXAM QUESTIONS AND ANSWERS LATEST UPDATE 2023/2024 ALL ANSWERS CORRECT ELABORATED TO SCORE A+ . Interphase (G1, S, G2) - CORRECT ANSWERS Period of cell growth when a cells DNA is replicated. Checkpoint - CORRECT ANSWERS How cell division is regulated. If stages are not completed successfully then cell division should stop and the cell return to the resting stage. Semi-conservative DNA replication - CORRECT ANSWERS The process by which DNA molecules replicate. The new DNA molecule consists of one new polynucleotide chain and one polynucleotide chain from the original DNA molecule. DNA Polymerase - CORRECT ANSWERS Enzyme responsible to joining new nucleotides together during DNA replication. Catalyses formation of new phosphodiester bonds and the formation of the sugar phosphate backbone. Centrioles - CORRECT ANSWERS Pair of cylindrical structures, consisting of microtubules which organise the spindle fibres. Spindle fibres - CORRECT ANSWERS Structures made of microtubules, responsible for separating chromatids and chromosomes during mitosis and meiosis. Centromere - CORRECT ANSWERS Structure responsible holding sister chromatids together and attaching chromosomes to spindle fibres. Meiosis - CORRECT ANSWERS Type of cell division where the daughter cells have half the number of chomosomes of the parent cell and are all genetically different. Haploid cell - CORRECT ANSWERS These cells only have one set of each chromosome. They have half the number of chromosomes that a diploid cell does. Diploid cell - CORRECT ANSWERS These cells have two sets of each chromosome. Sister chromatids - CORRECT ANSWERS Following semiconservative DNA replication, there are to copies of each chromosome, held together by the centromere.