Edexcel A Level Biology Exam Questions 2024, Exams of Nursing

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3.1: Define what prokaryote and eukaryote cells are and give an example of a type of organism for each group. - Correct Answers ✅Prokaryote: "before nucleus"- these are bacteria and cyanobacteria Eukaryotes: "true nucleus"- these are all other cells, including plant and animal cells 3.2: State the symbols used for millimeters, micrometers and nanometers and be able to convert measurements - Correct Answers ✅Millimeters to Micrometers: divide by 1000 Micrometers to Nanometers: divide by 1000 Nanometers to Micrometers: times by 1000 Micrometers to Millimeters: times by 1000 3.3: Draw a diagram of a prokaryotic cell, label the structures listed and describe their function: cell wall, capsule, plasmid, flagellum, pili, ribosomes, mesosomes, and circular DNA. - Correct Answers ✅ONLY SOME Mesosome: (infolding of cell surface membrane); site of respiration Plasmid: circular DNA, antibiotic resistance Capsule: prevent dehydration Pili: adhere to surfaces

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Flagellum: make cell motile ALL Ribosomes: protein synthesis Circular DNA: carrier genetic code Cell Surface Membrane: controls what enters and exits cell Cell Wall: structure Cytoplasm: site of chemical reactions 3.4: Draw a diagram of a eukaryotic cell, label the structures listed and describe their functions: nucleus, nucleolus, ribosomes, RER, SER, mitochondria, centrioles, lysosomes, and golgi apparatus. - Correct Answers ✅Mitochondria: site of respiration SER: no ribosomes attached; production and transport of lipids Cytoplasm: site of chemical reactions Ribosomes: site of protein synthesis (transcription) Cell Membrane: controls what enters and exits the cell Centrioles: Involved in formation of cell fibres Nucleolus: Ribosomes are made here RER: covered in ribosomes; transport of proteins Lysosome: contains digestive enzymes Golgi Apparatus: modifies proteins

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3.5: State 3 similarities and 3 differences between prokaryotic and eukaryotic cells. - Correct Answers ✅Similarities: -both have ribosomes -both have cell surface membranes -both have cytoplasm Differences: -no nucleus in prokaryotic cells -eukaryotic is larger -prokaryotic have plasmid (eukaryotic does not) 3.6: Identify cell structures from photographs and electron micrographs of cells. - Correct Answers ✅See Diagram. 3.7: Manipulate and use the formula of magnification in order to calculate size information about an organelle. - Correct Answers ✅Magnification= size of imagine/size of real object e.g.: 0.023 micrometers diameter magnification imagine= 0.0345mm 1mm=1000 micrometers

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0.0345x1000=34.5 micrometers 34.5 micrometers/0.023 micrometers= 3.8: Convert numerical size information about an organelle between ordinary and standard form. - Correct Answers ✅15 000 000 = 1.5 × 10 000 000 This can be rewritten as: 1.5 × 10 × 10 × 10 × 10 × 10 × 10 × 10= 1. 5 × 10 7 3.9: Calculate the surface area and volume of a cell which has a regular shape. - Correct Answers ✅SA= l x w x number of sides v= l x w x d 3.10: Draw a flowchart that shows how different organelles and nucleus involved in the process of protein production and trafficking in a cell. - Correct Answers ✅1. transcription of DNA to mRNA

2. mRNA leaves nucleus
3. protein made on ribosomes enter RER
4. protein moves through the ER assuming 3D shape (folding)
5. vesicles pinched off the RER contain the protein
6. vesicles from RER fuse to form the flattened sacs of Golgi Apparatus
7. proteins are modified within the Golgi Apparatus

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8. vesicles pinched off the GA contained modified protein
9. vesicles fuse with GA cell surface membrane and releases it by exocytosis 3.11: Describe and explain the role of the RER and golgi apparatus in protein production and modification. - Correct Answers ✅RER- produces proteins in ribosomes and folds them assuming 3D shape Golgi Apparatus- modified within here, e.g.: add glycoprotein 3.12: Draw an ovum (egg cell), label the structures and describe their functions. - Correct Answers ✅Haploid Nucleus: contains genetic code Mitochondria: used for energy Cortical Granules: involved in cortical reaction to prevent polyspermy Lipid Droplets: used as an energy store Cell Surface Membrane: controls what enters and exits the cell Jelly Coat: prevent polyspermy/protection 1.13: Explain why an ovum needs to be large. - Correct Answers ✅The ovum needs to be large relative to the sperm so it can be more easily found and act as a bigger target.

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3.14: Draw a sperm cell, label the structures and describe their function. - Correct Answers ✅Acrosome: takes part in acrosome reaction to digest zona pellucida and follicle cells Haploid Nucleus: contains genetic code Middle Piece: contains mitochondria Flagellum: make sperm motle Mitochondria: energy store 3.15: Draw a flow chart that shows how a sperm reaches an ovum and fertilisation is achieved (including the stages in the acrosome reaction, the cortical reaction and fertilisation of the nuclei). - Correct Answers ✅1. sperm reaches ovum

2. acrosome reaction is triggered by chemicals from the ovum (follicle cell)
3. acrosome swells and fuses with cell surface membrane of sperm
4. digestive enzymes released
5. enzymes digest follicle cells and jelly coat
6. sperm moves to egg cell surface membrane and fuses
7. sperm nucleus and egg nuclei fuse after sperm nuclei moves through egg cell surface membrane
8. cortical grannuels release enzymes and thicken jelly coat

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3.16: Define the terms chromosome, homologous pair, locus, gamete, haploid, diploid. - Correct Answers ✅Chromosome- DNA molecule, histone proteins Homologous Pair- Pair of chromosomes that have same genes Locus: Location (of gene on chromosomes) Gamete: Sex cell, produced in mitosis Haploid: Half number of chromosomes Diploid: Regular number of chromosomes 3.17: Explain the terms linkage of genes and sex linkage. - Correct Answers ✅Genetic Linkage: is the tendency of alleles that are located close together on a chromosome to be inherited together during meiosis phase of sexual reproduction Sex Linkage: colour blindness is an example of sex-linkage; this means that genes involved are located on the sex chromosomes 3.18: Explain why alleles at adjacent loci on the same chromosomes are more likely to be linked compared to alleles at distant loci on the same chromosomes. - Correct Answers ✅See Diagram. 3.19: Explain why it is important for gametes to haploid. - Correct Answers ✅Gametes have to be haploid (half the number of

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chromosomes) because when they join, the original diploid chromosome number will be restored. 3.20: Explain the relationship between chromosomes and chromatids. - Correct Answers ✅See Diagram. 3.21: Draw a sequence of diagrams that show the process of meiosis and annotate them with what is happening at each stage. - Correct Answers ✅See Diagram. 3.22: Describe the outcome of meiosis and what happens to these cells in male and female organisms. - Correct Answers ✅The outcome of meiosis is four haploid cells and these in males become sperm and in females become eggs. 3.23: State 2 ways in which meiosis can produce genetic variation. - Correct Answers ✅-crossing over of homologous pairs -independent/random assortment of homologous pairs 3.24: Describe the process of crossing over and explain how it can produce genetic variation. - Correct Answers ✅They have different alleles for their genes so when they cross over, there is genetic variation.

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3.25: Describe the process of independent assortment of homologous chromosomes and explain how it can produce genetic variation. - Correct Answers ✅When chromosomes are split, they are pulled to either end of the cell (poles)- the side which they go to is random, so when they split, this creates variation. 3.26: Calculate the number of different possible ways in which homologous chromosomes can align along the equator of the cell during meiosis. - Correct Answers ✅If there are 6 diploid chromosomes, there will be 3 homologous pairs lined up along the equator during meiosis 1. There are 8 possible gamete combinations calculated by 2 ^3 (cubed). 3.27: Define the terms zygote and embryo. - Correct Answers ✅Zygote: cell after egg has been fertilised and started dividing. Embryo: stage after zygote, where more cell division had taken place. 3.28: List the stages in the cell cycle in order, and state what happens during each stage. - Correct Answers ✅Interphase- cells prepare for DNA replication (G1, S,G2) DNA synthesises Prophase- chromosomes become visible; nucleolus and nuclear membrane disappear

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Metaphase- chromatids line up along the equator Anaphase- chromatids are pulled apart by spindle fibres (at centromeres) Telophase- nuclear membrane reforms Cytokinesis- cell divides in two 3.29: List the stages of interphase in order and stage what happens at each stage. - Correct Answers ✅G1- growth, replication of cell organelles S- synthesis of DNA (DNA copies/doubles) G2- more growth/copying 3.30: List the stages of mitosis in order and with the help of diagrams describe what is happening at each stage. - Correct Answers ✅[Interphase: G1,S,G2: growth, synthesis of DNA, replication of organelles]

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Prophase: nuclear membrane disappears, chromosomes become visible Metaphase: chromatids line up along the equator Anaphase: chromatids are pulled to the poles (by spindle fibres) Telophase: nuclear membrane reforms 3.31: Explain the role of centrioles, centromeres, and spindle fibres in mitosis. - Correct Answers ✅Centrioles- produce spindle fibres, go to either pole Centromeres- pulled by spindle fibres, join chromatids together Spindle Fibres- pull chromatids apart 3.32: Identify what stage of the cell cycle a cell is in from a photograph or diagram. - Correct Answers ✅See Diagram. 3.33: Describe a safe, reliable method to prepare cells from a garlic plant in order to see cells in different stages of the cell cycle. - Correct Answers ✅DV: stages of the cell cycle (using an microscope) IV: root tip (cells within root tip of garlic) Control Variables: temperature, volume of hydrochloric acid (2cm cubed), time left in water (5 mins) Safety: wear goggles when using hydrochloric acid, carry microscope with two hands when transferring it from place to place

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-cut root tip off -place in 2cm cubed of hydrochloric acid for 5 mins -put root tips in water for 5 mins -transfer onto clean microscope slide -break up root tip with mounted needle (macerate) -cover with coverslip and blot firmly with several layers of tissue/filter paper 3.34: Describe how the processes in the cell cycle in plants differ from the processes in animals. - Correct Answers ✅Some plants, like moss, have irregular cell cycles. GAMETES --[fertilisation]--ZYGOTE--[mitosis]--SPOROPHYTE--[meiosis]-- SPORES--[mitosis]--GAMETOPHYTE--[mitosis] (Back to gametes) 3.35: Explain which processes in living things require mitosis. - Correct Answers ✅-growth (increase cell number) -repair (cells die/get damaged, need to be replaced) 3.36: Calculate how many cells have been produced during mitosis from one cell, given the number of cell cycles that have taken place. - Correct Answers ✅During mitosis, one cell splits into two. After every cell cycle, the number of cells with double.

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3.37: Define the terms totipotent, pluripotent, multipotent, stem cell and differentiated cell. - Correct Answers ✅Stem cell that can.. -totipotent: become all cells -pluripotent: become most cells -multipotent: become some cells Stem Cell: cell with the potential to become multiple cells, unspecialised Differentiated Cell: cell with one purpose, cannot become multiple cells. 3.38: Explain why some cells do not remain totipotent. - Correct Answers ✅Some cells do not remain totipotent because during fertilisation and cell division, they become specialised for a purpose. 3.39: Describe the development of a zygote into a blastocyst, and describe the structure of a blastocyst and state the fate of the cells in a blastocyst. - Correct Answers ✅-after a week of fertilisation/cell division, the zygote [single cell] becomes a blastocyst [about 200 cells] -fluid filled cavity forms -the outer cells will become the placenta, as they are totipotent

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-the inner, pluripotent cells will become the foetus 3.40: State 3 examples of multipotent stem cells in adult humans. - Correct Answers ✅-nerve cells -muscle cells -bone marrow 3.41: Explain how the "potency" of plant cells is different from animal cells. - Correct Answers ✅In animal cells, once specialised/differentiated, they are usually permanently specialised However, in plant cells, they become specialised and unspecialised throughout their lifetime. 3.42: Describe the potential uses of stem cells in medicine and explain why they may be so useful. - Correct Answers ✅Stem cells can be used to regrow limbs, organs, etc. as well as control/cure degenerative diseases. They could be so useful as unlike donor organs, there is no chance of rejection.

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3.43: Explain why pluripotent embryonic stem cells could be considered more useful than adult multipotent stem cells. - Correct Answers ✅With embryonic stem cells, they could be more useful than body stem cells because embryonic cells can turn into more types of cells than body cells. Therefore they are more useful. 3.44: Explain why some people are "for" the use of embryonic stem cells and others are "against" it by using the frameworks for ethical decisions. - Correct Answers ✅FOR -embryos will be destroyed anyway -advance science with the hope of saving lives AGAINST -parents/mothers pressured into donating eggs -equivalent to murder on religious grounds 3.45: Explain how therapeutic cloning and somatic cell nuclear transfer an overcome the problem of possible rejection of transplanted organs. - Correct Answers ✅If stem cells are used, there is no risk of rejection because the DNA is from you (in the stem cells); it will not be recognised as a foreign body.

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3.56: State the legal situation with the use of cloned human embryos and animal-human embryos. - Correct Answers ✅It is currently legal in the UK, but does have strict regulations on it; they are not to develop beyond a certain point. 3.47: State 3 dangers of stem cell therapy. - Correct Answers ✅-stem cells becoming cancerous -body may reject stem cells -when injecting stem cells, there will always be a risk of introducing infection 3.48: Explain the role of regulatory authorities in scientific research. - Correct Answers ✅In scientific research, the role of regulatory authorities is to prevent extremely controversial research being allowed to be carried out- also to balance ethical debates with advancements of science. 3.49: Sketch and label a diagram of the nucleus to show its 3 main features. - Correct Answers ✅1. nucleolus

2. nuclear pore
3. double membrane/nuclear envelope 3.50: Draw and annotate a series of diagrams to illustrate the experiments of Hammerling which demonstrated the importance of the

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nucleus in the control of the development- your diagrams must use colour to show the different hats, stalks and rhizoids. - Correct Answers ✅Experiment #1: procedure: cut of hat result: hat regrew Experiment #2: procedure: took 2 species; removed hats; put species 2 stalk on species 1 rhizoids (stalks) result: new hat had features of both species Experiment #3: procedure: removed "mixed hat" from Experiment 2; let it regrow again result: species 1 hat grew Therefore, nucleus (in rhizoids) was critical to development 3.51: Explain how, by having a diploid nucleus, a cell can be produced that is able to produce any protein that an organism requires. - Correct Answers ✅A diploid cell contains all of the genes required to make any protein the body requires; the nucleus can produce all proteins the body needs.

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3.52: Understand how the experiments of Dawid and Sargent on developing frogs demonstrated that different genes are expressed in different cells. - Correct Answers ✅LATE FROM EMBRYO (CELLS MORE SPECIALISED)

1. extract mRNA from cells
2. add reverse transcriptase
3. remove RNA/RNA is digested EARLY FROG EMBRYO (CELLS NOT SPECIALISED)
4. extract mRNA from cells
5. early cell mRNA and cDNA care mixed ((hybrids pairs created; some RNA unbound)) Results showed in the later frog, more genes were switched on. 3.53: State what is meant by gene "induction." - Correct Answers ✅Gene induction is when a gene is active or switched on. 3.54: Describe the connection between a "switched on" gene and the presence of active mRNA, and hence the ability to make proteins. -

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Correct Answers ✅When a gene is switched on, RNA polymerase can carry out transcription and mRNA is produced. 3.55: Describe what is meant by the "LAC operon." - Correct Answers ✅operon= promoter region, operator gene, repressor molecule, gene [e.g.: to make beta galactosidase] lac operon = operon to make lactose operon; operation lac; lactose 3.56: Describe how E.coli responds to a medium in which only lactose is present as respiratory substrate (mentioning beta galactosidase enzyme, hydrolysis and the relevant monomers.) - Correct Answers ✅When lactose is present, it binds to the repressor molecule; then the RNA polymerase can bind to the promoter region. mRNA is produced and gene is switched on. 3.57: Explain how E.coli responds differently if glucose is present (referring to beta galacatosidase). - Correct Answers ✅If glucose is present, the gene for the production of beta galactosidase does not need to be switched on as it is only needed if glucose is in a more complex form (like lactose; glucose + galactose).

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3.58: Explain how E.coli "know" how to respond differently by reference to genetic witched (repressor proteins) - Correct Answers ✅E.coli "know" because when lactose is NOT present, the repressor molecule is bound to the operator gene, prevent the RNA polymerase from reading the gene to make beta galactosidase. When lactose IS present, it binds to the repressor molecule, allowing the operator gene

• gene for making beta galactosidase to be read. 3.59: Describe the role of the enzyme RNA polymerase in determining whether a gene will be transcribed or not. - Correct Answers ✅When RNA polymerase can read and bind to the operator gene and the gene is trying to be read, the gene is transcribed. If the RNA polymerase cannot do this, there is no transcription. 3.60: Describe 2 ways in which a gene can be switched off by the presence of a protein repressor molecule. - Correct Answers ✅1. if repressor molecule is bound to the promoter region

2. if the repressor molecule is bound to the regulator protein 3.61: Define the following terms: cell, tissue, organ, organ system. - Correct Answers ✅Cell: the smallest independent structure in an organism that may have a specialised function, e.g.: RBC

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Tissue: identical cells grouped, working together to perform the same function, e.g.: nerve tissue Organs: two or more different tissues working together to carry out a number of functions, e.g.: a heart Organ System: a group of organs working together to carry out a function, e.g.: circulatory system. 3.62: Describe an adhesion molecule (mentioning proteins and cell surface membrane) - Correct Answers ✅Adhesion molecules/recognition proteins are arranged in the cell surface membrane. 3.63: Explain the role of adhesion molecules in tissue structure. - Correct Answers ✅Adhesion molecules join cells together so that tissues can form. If two certain types of adhesion molecules join together, a certain type of tissue will form. 3.64: Describe the connection between gene expression of adhesion molecules and the ability to form tissues. - Correct Answers ✅Changing the type of recognition proteins produced by the cells, by switching off the previously used gene, and switching on others instead.

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3.65: Describe the role of master genes in the development of the fruit fly. - Correct Answers ✅Drosophila; they have particular segments which may have cells that become legs, antennae or wings. Master genes control the development of eat segment. 3.66: Describe how master genes are thought to switch off genes (mentioning mRNA and signal proteins). - Correct Answers ✅Master genes produce mRNA which is translated into signal proteins. These signal proteins switch on genes responsible for producing proteins needed for specialisation. 3.67: Apply your knowledge of gene expression to novel examples (e.g.: the genes needed to make the structure within a flower in the correct sequence.) - Correct Answers ✅A only=sepals C only=carpels A+B=petals B+C=stamens These genes produce mRNA that codes for signal proteins which switch on the appropriate genes.

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3.68: Define and distinguish between the following terms: gene, allele, locus, phenotype, genotype. - Correct Answers ✅Gene: a section of DNA that codes for proteins Allele: variation of one gene Locus: location of a gene on a chromosome Phenotype: the physical expression of an allele, e.g.: blue eyes Genotype: the written form of a gene (alleles), e.g.: Bb 3.69: Define the term "variation" (using the term species). - Correct Answers ✅Variation is individual differences between members of the same species. 3.70: List 2 main causes of variation. - Correct Answers ✅1. the genes which the organism carries (genotype)

2. the environment in which it lives 3.71: Name the two types of variation and give 2 examples of each in humans. - Correct Answers ✅continuous, e.g.: height, skin colour discontinuous, e.g.: blood groups, sex 2.37: Distinguish between the two types of variation in terms of the number of genes that have influence and the relative influence of the environment. - Correct Answers ✅continuous

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-many genes -impacted by the environment discontinuous -one/two genes -not really affected by environment 3.73: Sketch typical graphs for both continuous and discontinuous variation. - Correct Answers ✅continuous -continuous data graph, bell graph discontinuous -discrete data -distinct groups 3.74: List 4 factors thought to help explain why we are taller than British people 200 years ago. - Correct Answers ✅-better nutrition -clean air -warmer climate -more food suplies

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3.75: Calculate the mean, median and mode of a set of data for a given phenotype. - Correct Answers ✅mean: add all up and divide them by how many there are median: middle value mode: most frequent 3.76: Calculate the standard deviation of a set of data for a given phenotype. - Correct Answers ✅See Diagram. 3.77: Explain why standard deviation might be more useful measure of dispersion for given set of data. - Correct Answers ✅It allows error bars to be shown to see if there is actually a statistical difference- and if the error bar is smaller, the data is more consistent; if larger, the data is more spread out. 3.78: Define the terms: genetics, epigenetics, genome and epigenome. - Correct Answers ✅Genetics- the study of genes, heredity and genetic variation in living organism. Epigenetics- the study of cellular and physiological variations that are NOT caused by changes in the DNA sequence but changes in the environment Genome- all of the genes of the DNA in a diploid cell Epigenome- chemical markers attached to the surface of DNA and its histone proteins.