AQA A LEVEL BIOLOGY EXAM WITH GUARANTEED ACCURATE ANSWERS, Exams of Nursing

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AQA A LEVEL BIOLOGY EXAM

WITH GUARANTEED ACCURATE

ANSWERS

what is RNA? - correct answer ✔✔ribonucleic acid MRNA and TRNA single stranded shorter AU CG what are biological molecules? - correct answer ✔✔molecules made and used by living organisms eg. lipids, carbs, DNA, AT, water, inorganic ions what are the functions of carbohydrates? - correct answer ✔✔-energy source (respiration) -energy store (starch and glycogen) -structure (cellulose) ATP structure? - correct answer ✔✔1 adenosine 3 phosphates ADP and energy= ATP condensation reaction using ATP synthase carries energy in bonds hydrolysis breaks down into ADP and energy using ATP hydrolase

releases energy from phosphate group bonds what are the building blocks of carbohydrates called? - correct answer ✔✔monosaccharides why is ATP a good source of energy? - correct answer ✔✔immediate release, only need to break one bond releases small amounts of energy at a time, manageable examples of monosaccharides - correct answer ✔✔glucose, fructose, galactose uses of ATP? - correct answer ✔✔protein synthesis organelle synthesis dna replication mitosis active transport metabolic reactions movement homeostasis formula for monosaccharides? - correct answer ✔✔c6h12o6 -same formula but arranged differently

role of water in biology? - correct answer ✔✔acts as a habitat for organisms make up cytoplasm, tissue fluid, blood, xylem and phloem water properties? - correct answer ✔✔dipolar partially positive hydrogen partially negative oxygen so separate water molecules form hydrogen bonds with eachother difference between alpha and beta glucose? - correct answer ✔✔on carbon 1, alpha glucose has an OH group on the bottom. beta glucose has it at the top. how are monosaccharides joined together? - correct answer ✔✔condensation reaction between 2 OH groups roles of water? - correct answer ✔✔-habitat, high shc so a lot of heat needs to be applied before evaporation due to hydrogen bonds. ice is less dense than water so floats up -solvent, dipolar so separate solutes by charge depending on partial charge. solute dissolves in water, useful for cytoplasm, diffusion and active transport ect -hydrostatic pressure, when pressurised, water provides a strong pushing force particularly in mass flow. supports turgidity -homeostasis, sweat on skin uses blood heat to evaporate, cooling individual. sweat is made up of hydrogen bonds,stable structure, large amount of heat to evaporate. LATENT HEAT OF EVAPORATION.

bond in carbohydrate? - correct answer ✔✔glycosidic what are inorganic ions? - correct answer ✔✔salts or minerals don't contain carbon eg sodium and chloride ions examples of disaccharides - correct answer ✔✔sucrose, lactose (glucose

• galactose), maltose (glucose + glucose) kingdoms of biology? - correct answer ✔✔animal, plant, bacteria, fungi, protocista animal and plant multicellular others are microorganisms viruses aren't living all organisms made up of cells eukaryotic vs prokaryotic - correct answer ✔✔eukaryotic - membrane bound organelles eg. nucleus prokaryotic - no membrane bound organelles, smaller ribosomes formula for disaccharides? - correct answer ✔✔c12h22o

what are the 2 forms of reproduction? - correct answer ✔✔sexual- 2 parents each provide gamete which fuse to make zygote which develops into organism asexual- one parent to produce genetically identical offspring how are polymers separated? - correct answer ✔✔hydrolysis (addition of water) how does a zygote develop into an organism? - correct answer ✔✔stem cell, undifferentiated divides by mitosis to make more stem cells each cell differentiates into specialised each specialised divides by mitosis to make tissues different tissues for organ, and so on what is a polysaccharide? - correct answer ✔✔many monosaccharides joined together by condensation reaction/glycosidic bonds. structure of nucleus? - correct answer ✔✔contains DNA wrapped around histones to form chromatin double membrane called nuclear envelope with pores nucleolus produces ribosomes and mRNA nucleoplasm contains chromatin

examples of polysaccharides - correct answer ✔✔-amylose, long chain of alpha glucose, makes starch/glycogen -cellulose, long chain of beta glucose properties of starch and glycogen as energy stores? - correct answer ✔✔-insoluble, doesn't affect water potential, cell won't shrink or burst -coiled, compact, fits inside cells better -branched/chained, easy to break down, glucose removed from the end endoplasmic reticulum? - correct answer ✔✔rough- has ribosomes ,protein synthesis, process and package smooth- makes lipids and carbs golgi apparatus? - correct answer ✔✔processes and packages proteins into vesicles digestive enzymes placed into lysozomes, vesicles with membranes structure of cellulose? - correct answer ✔✔-beta glucose arranged in straight chain (each alternative beta glucose rotated 180°) -many cellulose chains are cross linked by hydrogen bonds, form microfibrils -microfibrils crosslinked to make macrofibrils -hydrogen bonds are strong together, hard to break,makes cellulose strong -forms cell wall structure

mitochondria? - correct answer ✔✔site of respiration, produces ATP which releases energy cristae- inner membrane has large surface area so more metabolic enzymes can attach matrix- middle liquid test for starch? - correct answer ✔✔iodine brown to blue/black chloroplast structure? - correct answer ✔✔absorbs light energy for photosynthesis to produce glucose double membrane thylakoid disks stack into granum thylakoid surrounded by stroma fluid large surface area test for reducing sugars - correct answer ✔✔heat with benedicts, turns brick red vacuole - correct answer ✔✔surrounded by membrane called tonoplast contains cell sap keeps cell turgid pushes chloroplasts to surface

test for non reducing sugar? - correct answer ✔✔-heat with benedicts, no change -add dilute hcl (hydrolyses glycosidic bond) -add sodium hydrogen carbonate to neutralise -heat with benedicts, will turn brick red structure of bacteria? - correct answer ✔✔circular DNA and plasmids no membrane bound organelles smaller ribosomes cell wall made of murein some have slime capsule (protect from phagocytosis) and flagella (movement) types of proteins? - correct answer ✔✔globular and fibrous structure of virus? - correct answer ✔✔DNA or RNA if RNA, contains reverse transcriptase enzyme to convert it into DNA capsid phospholipid membrane attachment proteins to identify and attach to host what are globular proteins? - correct answer ✔✔have a specific 3d shape, soluble eg. haemoglobin

how does a virus infect their host cell? - correct answer ✔✔uses attachment protein to attach send in DNA capsid which uses cell to make virus components producing copies and destroying host cell what are fibrous proteins? - correct answer ✔✔insoluble, inflexible and strong eg. keratin how do amino acids differ? - correct answer ✔✔have different r groups what is a chromosome? - correct answer ✔✔coiled DNA formed during interphase made of 2 sister chromatids joined by centromere 2 copies of same DNA molecule what is a homologous pair of chromosomes? - correct answer ✔✔ 1 maternal 1 paternal same genes but different alleles how are amino acids joined? - correct answer ✔✔condensation reaction between carboxyl group and amine group. leaves bond between carbon and nitrogen, DIPEPTIDE

primary structure of a protein? - correct answer ✔✔sequence of AA, polypeptide chain. change in sequence, bonds will be formed in different places in secondary. secondary structure? - correct answer ✔✔primary structure coils to form an alpha helix, hydrogen bonds form between amino acids tertiary structure? - correct answer ✔✔secondary structure folds again to form final 3d shape, held by ionic/hydrogen/disulfide bonds quarternary structure? - correct answer ✔✔more than one polypeptide chain, non protein can be involved quarternary structure examples? - correct answer ✔✔haemoglobin, antibodies, collagen collagen structure? - correct answer ✔✔-strong -primary structure glycine -secondary tight coil -tertiary coils again -quarternary three chains wrapped like rope protein test? - correct answer ✔✔biruet reagent, turns purple what is an enzyme? - correct answer ✔✔biological catalyst

speeds up reaction without being used up lowers activation energy what makes an enzyme specific? - correct answer ✔✔specific active site, only complimentary substrates can bind and form enzyme substrate complexes lock and key model? - correct answer ✔✔active site is rigid, only exactly complimentary substrates fit induced fit model? - correct answer ✔✔shape of active site changes slightly so substrate fits exactly forming ES complex affect of substrate concentration on enzyme activity? - correct answer ✔✔more substrate, more chance of successful collisions, ES complex, increase rate increases until all enzymes are saturated affect of enzyme concentration on enzyme activity? - correct answer ✔✔more enzymes, more successful reactions, ES complexes continues until all the substrates are used up affect of temperature on enzyme activity? - correct answer ✔✔as temp increases, kinetic energy increases, molecules move faster more collisions, more ES complexes

carries on until optimum after optimum, tertiary bonds break lose active site shape no longer complimentary denatured affect of ph on enzyme activity? - correct answer ✔✔if ph is changed away from optimum, bonds in tertiary structure break, enzyme denatured competitive inbibitor? - correct answer ✔✔similar shape to substrate fits in active site blocks ESCS from forming non competitive inhibitor - correct answer ✔✔binds on somewhere other than active site, changes the enzymes shape, prevents substrate from binding 3 types of lipids? - correct answer ✔✔triglycerides phospholipids cholesterol triglyceride structure - correct answer ✔✔1 glycerol 3 fatty acids joined by ester bonds in condensation reaction COOC bond

either saturated or unsaturated phospholipid stucture? - correct answer ✔✔1 glycerol 2 fatty acids 1 phosphate group phosphate forms hydrophilic head fatty acid hydrophobic tail forms phospholipid bilayer what are nucleic acids? - correct answer ✔✔polymers made from nucleotides eg DNA and RNA what is DNA? - correct answer ✔✔deoxyribonucleic acid in all organisms carries genes, section of DNA coding for a protein building block of DNA? - correct answer ✔✔nucleotide (made of phosphate, deoxyribonucleic sugar, nitrogenous base) AT CG DNA structure? - correct answer ✔✔double helix sugar and phosphate condensation reaction hydrogen bonds between bases

AT CG

double strand coiled in double helix properties of DNA structure? - correct answer ✔✔double stranded, one strand acts as template for semi con replication helix, more compact sugar phosphate backbone protects bases hydrogen bonds weak, easy to break for replication complimentary Base pairing, ensures identical DNA copies made describe semi conservative replication? - correct answer ✔✔DNA double strand separated by DNA helicase, breaks h bonds one strand acts as template free nucleotides match up and bind to complimentary bases DNA polymerase joins sugar phosphate back of new strand scr evidence? - correct answer ✔✔bacteria DNA has 2 isotopes 14n and 15n 15n heavy 14n light nitrogen found in bases what does mitosis produce? - correct answer ✔✔two genetically identical diploids which have a full set of chromosomes

what happens in interphase? - correct answer ✔✔dna replication protein and organelle synthesis what happens during prophase? - correct answer ✔✔chromatin condenses to make chromatids nuclear envelope breaks down spindle fibres form what happens during metaphase? - correct answer ✔✔chromosomes line up on cell equator attach to spindle fibres by centromere what happens during anaphase? - correct answer ✔✔spindle fibres pull sister chromatids by centromere to opposite poles sister chromatids make a v shape what happens during teleophase? - correct answer ✔✔chromatids uncoil to make chromatin again nuclear envelopes reform 2 identical nuclei formed in one cell what happens during cytokinesis? - correct answer ✔✔cytoplasm splits into 2 creating 2 identical sister cells

what happens to chromosome number during mitosis? - correct answer ✔✔stays the same diploid what is cancer? - correct answer ✔✔formation of tumour due to uncontrolled mitosis/ cell division how does uncontrolled cell division occur? - correct answer ✔✔mutation of dna/ genes that regulate mitosis cell mutations can occur randomly or due to mutagens eg. radiation cancer cells are rapidly dividing spend less time in interphase and more time in mitosis treatments for cancer? - correct answer ✔✔surgery to remove tumour chemotherapy, drugs that inhibit mitosis in rapidly dividing cells radiotherapy, radiation used to kill cancer cells disadvantages of chemotherapy? - correct answer ✔✔kills off normal healthy cells eg hair skin rbcs causing hair loss,dry skin and tiredness needs to be given as regular doses to allow time for healthy cells to recover

how do bacteria reproduce? - correct answer ✔✔binary fission (roughly splits cell into two parts) copy DNA and separate by asexual reproduction formula for magnification - correct answer ✔✔image/actual unit conversions? - correct answer ✔✔1mm=1000 micrometers 1mm=1,000,000 nanometers why do mitochondria appear different shapes in images? - correct answer ✔✔viewed from different angles at different levels some cut transversely others cut through the middle of the cell why do electron microscopes have a higher resolution? - correct answer ✔✔electron beams have a shorter wavelength TEM and SEM differences? - correct answer ✔✔tem- electrons absorbed sem- electrons bounce off specimen advantages and disadvantages of TEM? - correct answer ✔✔good- highest magnification and resolution bad- artefacts made, only dead specimens, need to be thin, black and white, 2d image

why do electron microscopes need to be in a vacuum? - correct answer ✔✔in air, oxygen molecules could collide with electrons and prevent electrons from reaching specimen advantages and disadvantages of SEM? - correct answer ✔✔good- 3d image bad- only dead specimens, black and white image, artefacts why does cell solution need to be cold, isotonic and ph buffered before homogenisation? - correct answer ✔✔cold- reduce enzyme activity which could damage organelles isotonic- no osmosis occurs so cells don't shrink or burst ph buffered- mantain constant ph why do cells need to be homogenised during cell fractionation? - correct answer ✔✔to break open cell membrane and release organelles so organelles can be studied in isolation why do cells need to be filtered during fractionation? - correct answer ✔✔remove membrane and whole cells what is cell ultra centrifugation? - correct answer ✔✔spun at low centrifugal force at first nucleus is largest so forms the first pellet at bottom pellet decanted and supernatant recentrifuged at higher speed

next heaviest organelle leaves and so on organelles by size? - correct answer ✔✔nucleus chloroplast mitochondria er/golgi/lysozomes ribosomes factors affecting diffusion? - correct answer ✔✔surface area concentration gradient thickness temperature size of molecules define osmosis - correct answer ✔✔net movement of water molecules from a high water potential to a low water potential through a semi permeable membrane what affects water potential? - correct answer ✔✔amount of solute in liquid more solute, more negative wp what happens when an animal cell is surrounded by pure water? - correct answer ✔✔swell and burst

high wp to low wp what happens when a plant cell is surrounded by pure water? - correct answer ✔✔swells but doesn't burst cell wall protects made of cellulose cell is turgid animal cell surrounded by glucose solution? - correct answer ✔✔shrinks flacid plant cell surrounded by glucose solution? - correct answer ✔✔water leaves cell wall prevents shrinking protoplast shrinks cell is plasmolysed describe active transport? - correct answer ✔✔molecules bind to carrier protein ATP breaks down to ADP, Pi and energy energy causes carrier protein to change shape carrier protein releases molecules on opposite side where there is a high con carrier protein releases pi to return to original shape

small intestines adaptions for diffusion? - correct answer ✔✔micro villi large surface area capillaries near by for circulation, maintain concentration gradient epithelial layer one cell thick, short diffusion pathway active transport of glucose in the small intestine? - correct answer ✔✔sodium ions actively transported from the epithelial cells into the blood stream, creating a concentration gradient as concentration is lower in cell sodium ions move into epithelial cells through diffusion glucose is pulled in through a Co transport protein with sodium glucose builds up in cell, so moves into bloodstream by diffusion what is a pathogen? - correct answer ✔✔a microorganism that causes diseases bacteria produce toxins viruses divide inside cells making them burst body's defense against pathogens? - correct answer ✔✔barriers phagocytosis specific immune response what are the barriers to pathogens? - correct answer ✔✔skin, impermeable barrier made of keratin

cilia and mucus in lungs stomach acid which denatures pathogens describe phagocytosis? - correct answer ✔✔pathogen releases chemicals that attract phagocyte phagocyte binds engulfs pathogen in phagocytic vacuoule lysozomes fuse and release digestive enzymes which break down pathogen by hydrolysis phagocyte presents pathogenic antigens on surface describe the specific immune response? - correct answer ✔✔phagocyte presents pathogen antigens on surface which stimulates t cells when binded t cells divide by mitosis to make helper, killer t cells killer cells kill infected cells helper t cells release chemical signals to stimulate b cells b cells divide by mitosis to make plasma and memory cells plasma cells make monoclonal antibodies memory cells long term immunity remain in blood what is an antigen? - correct answer ✔✔protein on surface of pathogen that stimulates an immune response

how does the immune response lead to the production of antibodies? - correct answer ✔✔t cells stimulated helper t cells stimulate b cells b cells have antibodies on surface and divide to make plasma cells which produce more antibodies what is an antibody? - correct answer ✔✔globular protein made by plasma cells variable, hinge and constant regions variable region has different shape on each antibody bind to complimentary antigens forming antigen antibody complexes destroy pathogen hinge region gives flexibility constant region binds to phagocytes for phagocytosis how do memory t cells work? - correct answer ✔✔made during specific immune response remain in blood if person is infected by same pathogen, memory cells will recognise pathogen and produce antibodies RAPIDLY in LARGE AMOUNTS- immunity how does a vaccine produce immunity? - correct answer ✔✔injection of dead or weakened pathogens that stimulate an immune response leading to production of specific antibodies and memory cells

active immunity? - correct answer ✔✔has memory cells long term immunity produces own antibodies occurs by vaccine or infection passive immunity? - correct answer ✔✔person given antibodies which eventually die no memory cells or long term immunity through placenta or breast milk or injection successful vaccination programme? - correct answer ✔✔low cost, safe, effective, long term immunity , easily produced ,no side effects produces herd immunity what is herd immunity? - correct answer ✔✔when a large proportion of the population is vaccinated , so most immune only few non immune so pathogen will have nowhere to go and die out less infection problems with vaccination programmes? - correct answer ✔✔doesn't work side effects no weak pathogen

many strains in one vaccine antigenic variability cannot achieve herd immunity as some will not be vaccinated what is antigenic variability? - correct answer ✔✔pathogen mutates antigen changes shape memory cells not complimentary so don't recognise pathogen therefore pathogen can reharm what is a monoclonal antibody? - correct answer ✔✔one type of antibody complimentary to one antigen made by one type of plasma cell what are monoclonal antibodies used for? - correct answer ✔✔pregnancy tests identify specific antigens/antibodies in the persons blood how do monoclonal antibodies identify specific antigens in the blood? - correct answer ✔✔place antibodies on plate add persons blood if antigen is present in blood, it will bind to monoclonal antibodies 2nd set of monoclonal antibodies with enzyme attached is added 2nd antibody binds to antigen. if not, antigen won't bind test plate washed