ESTAS SON ALGUNAS RESPUESTAS TÍPICAS A PREGUNTAS TÍPICAS DEL PAPER 2 PARTE B

SORRY, PERO LA TRADUCCIÓN CORRE POR SU CUENTA…..

CÉLULAS

QUÉ DEBE CONTENER TU DIBUJO DE UNA MEMBRANA CELULAR (ADEMAS DEL AUMENTO Y LA BARRA DE TAMAÑO-1CM- INDICANDO ESPESOR DE LA MEMBRANA)

Award [1] for each of the following structures clearly drawn and labelled correctly in a diagram of a plasma membrane.phospholipid bilayer;protein channels / integral (intrinsic) membrane proteins;peripheral (extrinsic) proteins associated with the membrane;cholesterol embedded in the membrane;glycoproteins / receptor proteins on the outside;hydrophobic and hydrophilic portions of membrane indicated; (both needed for [1])

[5]

Phospholipid structurehydrophobic tail / hydrophilic head;head made from glycerol and phosphate;tail made from two fatty acids;saturated / unsaturated fatty acid (in tail);

arrangement in membranephospholipids form a bilayer;heads face outside the membrane / tails face inside the membrane / hydrophobic interior / hydrophilic exterior of membrane;

A suitable annotated diagram may incorporate all or many of the above points.Award [5 max] for a suitable diagram that is labeled correctly.

FUNCIÓN DE LOS FOSLÍPIDOS EN LAS MEMBRANAS

phospholipids held together by hydrophobic interactions;phospholipids layers are stabilized by interaction of hydrophilic heads and surrounding water;phospholipids allow for membrane fluidity / flexibility;fluidity / flexibility helps membranes to be (functionally) stable;phospholipids with short fatty acids / unsaturated fatty acids are more fluid;fluidity is important in breaking and remaking membranes (eg endocytosis / exocytosis);phospholipids can move about / move horizontally / “flip flop” to

increase fluidity;hydrophilic / hydrophobic layers restrict entry / exit of substances;

.

TEMA 2- DIVISIÓN CELULAR

(a) Before cell division in unicellular and multicellular organisms, the nucleus must divide to produce two genetically identical nuclei. Explain the events that occur in cells that result in the production of genetically identical nuclei.

mitosis;DNA replication;each chromosome consists of two sister / identical chromatids;chromosomes condense / supercoiling;nuclear membrane breaks down;chromosomes align (at equatorial plate);spindle fibres / microtubules attach to centromeres of chromosomes on oppositesides;centromeres split;chromatids become chromosomes;sister / identical chromosomes pulled to opposite poles;nuclear membranes reform;events correctly assigned to interphase, prophase, metaphase,anaphase, and telophase;

TEMA 5 - ECOLOGÍA

(b)Cell division in unicellular organisms can increase the population size. Outline reasons for the population of a unicellular organism not increasing, despite reproduction by cell division.

mortality / cell death;emigration;rate of death / mortality equal to or greater than cell division / reproduction;predation / example of predator / macrophage;disease;competition for food / other resources;food running out;accumulation of waste products;change in pH;change in temperature;antibiotics:change in the growth medium;

lack of oxygen / carbon dioxide; 6 max

TEMA 2 DIVISIÓN CELULAR

c) Suggest why cell division is necessary in multicellular organisms.

more cells needed for growth;repair / replacement;cells specialize / differentiate for particular functions;formation of reproductive cells (meiosis);cells have to divide when they reach a certain size;surface area to volume ratio becomes too small;materials / oxygen / named material cannot be absorbed quickly enough;rate of use of materials related to volume but rate of exchange relatedto SA; 4 max

(Plus up to [2] for quality)

DIFERENCIAS ENTRE MITOSIS Y MEIOSIS

Outline the differences between the behaviour of the chromosomes in mitosis and meiosis.(Total 5 marks)

two divisions in meiosis, only one in mitosis;meiosis results in haploid cells, mitosis in diploid cells;crossing over only occurs in meiosis;no S phase precedes meiosis II;chromosome behaviour in meiosis II and mitosis is similar / chromosomebehaviour in meiosis I and mitosis is different;chiasmata only form during meiosis;homologous chromosomes move to the equator in pairs only in meiosis;Do not accept number of cells produced - it is a result not a behaviour.

[5]

TEMA 3 – QUÍMICA DE LA VIDA

ADN

PROCESO DE TRADUCCIÓN

Explain the process of translation.

consists of initiation, elongation and termination;mRNA translated in a 5' to 3' direction;binding of ribosome to mRNA;small sub-unit then large;first / initiator tRNA binds to start codon / to small subunit of ribosome;AUG is the start codon;second tRNA binds to ribosome;large subunit moves down mRNA after a second tRNA binds;amino acid / polypeptide on first tRNA is transferred / bonded to amino acid on second tRNA;peptide bonds between amino acids / peptidyl transferase;requires GTP;movement of ribosome / small subunit of ribosome down the mRNA;loss of tRNA and new tRNA binds;reach a stop codon / termination;polypeptide released;tRNA activating enzymes link correct amino acid to each tRNA;(activated) tRNA has an anticodon and thecorresponding amino acid attached;

ADNCOMPARACIÓN ENTRE TRANSCRIPCIÓN Y TRADUCCIÓN

Compare DNA transcription with translation.

both in 5' to 3' direction;both require ATP;DNA is transcribed and mRNA is translated;transcription produces RNA and translation produces polypeptides / protein;RNA polymerase for transcription and ribosomes for translation / ribosomesin translation only;transcription in the nucleus (of eukaryotes) and translation in the cytoplasm / at ER;tRNA needed for translation but not transcription;

RESPIRACIÓN CELULAR AERÓBICA

Explain the process of aerobic cellular respiration.

glucose is broken down to pyruvate in the cytoplasm;with a small yield of ATP / net yield of 2 ATP;and NADH + H+ / NADH;aerobic respiration in the presence of oxygen;pyruvate converted to acetyl CoA;acetyl CoA enters Krebs cycle;Krebs cycle yields a small amount of ATP / one ATP per cycle;and FADH2 / FADH + H+ / NADH / NADH + H+ / reduced compounds / electron collecting molecules;these molecules pass electrons to electron transport chain;oxygen is final electron acceptor / water produced;electron transport chain linked to creation of an electrochemical gradient;electrochemical gradient / chemiosmosis powers creation of ATP;through ATPase;

(5)

ADN

ESTRUCTURA DEL ADN CON DIAGRAMA, OF COURSE

Outline the structure of DNA.

double helix;two chains of nucleotides / composed of nucleotides;nucleotides consist of base, deoxyribose (sugar)and phosphate;bases are adenine, cytosine, guanine and thymine;anti-parallel / strands;

53 links between nucleotides;hydrogen bonds between base pairs / purine and pyrimidine on oppositechains;only A-T and G-C / complementary base pairs are A-T and G-C;two bonds between A-T and 3 between G-C; 5 max

Credit can be given for any of these points shown on a correctly drawn and labelled diagram.

TEMA 4 GENÉTICA Y BIOTECNOLOGÍA

GENÉTICA TEÓRICAEFECTOS DE LA HERENCIA CON DOS EJEMPLOS

(b) Describe the effects of polygenic inheritance using two specific examples.

more than one gene controls / affects one characteristic;Reject more than 2 alleles

can cause continuous variation / many different possible phenotypes;eg skin colour / other valid example;allele of each gene promotes melanin production or not / other validexample;eg grain colour in wheat / other valid example;allele of each gene promotes pigment production or not / other validexample; 5 max

If first or second example is incorrect do not accept third or subsequent examples.

ADN

EXPLIQUE EL PROCESO DE TRANSCRIPCIÓN EN EUCARIOTAS

Explain the process of transcription in eukaryotes.

(c) RNA polymerase controls transcription / is the enzyme used in transcription;DNA is unwound by RNA polymerase;DNA is split into two strands;mRNA is made by transcription;promoter region (by start of gene) causes RNA polymerase to bind;anti-sense / template strand of DNA is transcribed;direction of transcription is 35 ;free nucleotide triphosphates used;complementary base pairing between template strand and RNAnucleotides / bases;

Accept this marking point if illustrated using a diagram

RNA contains uracil instead of thymine;terminator (sequence) stops RNA polymerase / transcription;mRNA is released / RNA polymerase released; 8 max

(Plus up to [2] for quality)

TEMA 3 QUÍMICA DE LA VIDA

RESPIRACIÓN

COMPARACIÓN ENTRE RESPIRACIÓN AERÓBICA Y ANAERÓBICA

Explain the similarities and differences in anaerobic and aerobic cellular respiration.

Answers must include both similarities and differences to receive full marks.aerobic requires oxygen and anaerobic does not utilize oxygen;

similarities: 3 maxboth can start with glucose;both use glycolysis;both produce ATP / energy (heat);both produce pyruvate;carbon dioxide is produced;(both start with glycolysis) aerobic leads to Krebs’ cycle and anaerobicleads to fermentation;

differences: 5 maxanaerobic:(fermentation) produces lactic acid in humans;(fermentation) produces ethanol and CO2 in yeast;occurs in cytoplasm of the cell;recycles NADH (NAD+);

aerobic cellular respiration:pyruvate transported to mitochondria;further oxidized to CO2 and water (in Krebs’ cycle);produce a larger amount of ATP (36–38 ATP) / anaerobic produces less ATP (2);can use other compounds / lipids / amino acids for energy;

[8]

TEMA 3 QUÍMICA DE LA VIDA

DESCRIBA EL USO DE LOS HIDRATOS DE CARBONO Y LOS LÍPIDOS PARA EL ALAMACENAMEINTO DE ENERGÍA EN ANIMALES

Describe the use of carbohydrates and lipids for energy storage in animals.

nswers must discuss both carbohydrates and lipids to receive full marks.

carbohydrates: 3 maxstored as glycogen (in liver);short-term energy storage;more easily digested than lipids so energy can be released more quickly;more soluble in water for easier transport;

lipids: 3 maxstored as fat in animals;long-term energy storage;more energy per gram than carbohydrates;lipids are insoluble in water less osmotic effect; 5 max(Plus up to [2] for quality)

ENZIMAS

EXPLIQUE LA ESPECIFICIDAD ENZIMA SUSTRATO

Outline enzyme-substrate specificity.

Active site of enzyme binds to specific substrate;shape of the active site and substrate fit / complement each other;lock and key model;chemical properties of substrate and enzyme attract / opposite charges;enzyme / active site is not rigid and substrate can induce slight changes in shape;allows substrates of similar structure to bind with same enzyme;induced fit;causes weakening of bonds in substrate to lower activation energy;

[5]

TEMA 6 FISIOLOGÍA SISTEMA DIGESTIVO

DIBUJO Y ROTULO DEL SISTEMA DIGESTIVODraw and label a diagram of the digestive system.

Award [1] for each structure correctly drawn and labelled.esophagus attached to both mouth and stomach;stomach j-shaped sac attached to esophagus and u-shaped portion ofsmall intestine;large intestine wider diameter than small intestine, attached to small intestine;pancreas leaf-shaped, in u-shaped region of small intestine with small ductconnected to small intestine;liver large, triangular, to left of stomach;gall bladder small sac drawn on top of liver with tube connected to smallintestine at same region as duct from pancreas;anus at end of large intestine but narrower in diameter; 4 max

TEMA 3 QUÍMICA DE LA VIDA ENZIMAS

DISCUTA FACTORES QUE AFECTA LA ACTIVIDAD ENZIMÁTICA Discuss factors that affect enzyme activity (9)

(b) at low temperatures, rate of reaction increases as temperature increases(or vice versa);more kinetic energy / faster movement of molecules means more collisionsbetween enzyme / active site and substrate;optimum temperature is temperature at which rate of enzyme-catalyzedreaction is fastest;at high temperatures enzymes are denatured and stop working;

denatured means change of structure in enzyme / protein resulting in loss of itsbiological properties / no longer can carry out its function;too much kinetic energy / vibrations breaks bonds that give enzyme specificshape;optimum pH is one at which rate of enzyme-catalyzed reaction is fastest;rate of reaction reduced as increase or decrease pH (from optimum);strong acids and alkalis can denature enzymes;affect (weak, ionic, hydrogen) bonds that hold enzyme in specific shape;at low substrate concentrations, as increase concentration get increase in rateof reaction;more chance of collision between substrate and enzyme / active site;at high substrate concentration, have no change in rate as increaseconcentration;all active sites occupied; 9 max

ENZIMAS Y BIOTECNOLOGÍA

UTILIZACION DE LA LACTASA

Outline one industrial use of lactose.

(c) lactose intolerance high in some human populations / Asian / African / nativeAmerican and Australian aboriginal populations;lactase used to produce lactose-free / low-lactose milk;lactase breaks down lactose to glucose and galactose;source of lactase is usually yeast / many sources such as bacteria, moulds;milk passed over immobilized lactase / lactase bound to inert substance;increase sweetness of milk;no need to add extra sugar in manufacture of flavoured milk drinks / frozen desserts;can add (harmless) bacterium such as L.acidophilus which has same effect onlactose as in yoghurt; 5 max

(Plus up to [2] for quality)[20]

ENZIMAS E HIDRÓLISIS EN EL PROCESO DIGESTIVO

Outline the need for enzymatic hydrolysis in the digestive process.(6)

large molecules cannot be absorbed;mechanical digestion only to break down food physically;enzymes breakdown large molecules into smaller ones (that can be absorbed);need several enzymes as they are substrate specific;enzymes speed up the rate of digestion considerably;higher speeds at low / normal body temperature;named example of enzyme;example of named enzyme’s action; 6 max

ENZIMA SUSTRATO Y CONCENTRACIÓN DEL SUSTRATO

Explain why enzymes are substrate specific and why their activity is affected by substrate concentration.

(4)

Specificity:(active site works as a) lock and (substrate as a) key;(enzyme has) a specific shape;active site;(substrate has) a specific / complementary shape;(active site) fits substrate molecule / part of molecule / enzyme-substrate complex formed;activation energy lowered;

substrate concentration:lower / medium concentration activity increases;directly proportional to concentration of substrate;random collisions more frequent;activity levels off / plateau;high concentration no change in activity;as all active sites fully utilised; 8 maxAward [6 max] if only specificity or substrate concentrationaspects addressed.

TEMA 4 GENÉTICA Y BIOTECNOLOGÍA

USO DE LAS ENZIMAS DE RESTRICCIÓN Y ADN LIGASA EN BIOTECNOLOGÍA

(b) Outline the use of restriction enzymes (endonucleases) and DNA ligase in gene technology.

(6)

b) restriction enzyme:bacteria / E. coli has plasmids;plasmids / DNA cleaved / cut by enzyme;at specific points;leaving sticky ends;other species DNA cleaved / cut out by enzyme at same base sequence;suitable example;

ligase:DNA added to plasmid / other DNA;spliced to plasmid / other DNA by enzyme;at sticky ends;recombinant plasmids / DNA inserted into (new) host cells;(new) host cells may be cloned; 6 maxAward [4 max] if only restriction enzyme or ligase aspects addressed.

TEMA 6 FISIOLOGÍA SISTEMA DIGESTIVO

ROL DE ENZIMA S DEL SISTEMA DIGESTIVO

(c) Outline the role of two enzymes found in the digestive system of humans.

(c)Type / Specific example Substrate Product

eg amylase / salivaryamylase;

starch; maltose;

egprotease / pepsin; proteins; polypeptides / shortpeptide chains;

eglipase / pancreatic lipase; lipid; glycerol and fatty acids; 4 max

Award [2 max] for all three parts correct for one enzyme and[1 max] for correct enzyme and substrate or enzyme and product.

TEMA 6 SISTEMA

RESPIRATORIO

DIBUJO DEL SISTEMA RESPIRATORIO –SISTEMA DE VENTILACIÓN

Draw a diagram of the human gas exchange system.

Award [1] for each of the following structures clearly drawn and labelled.mouth / nose;trachea;bronchi;bronchioles;lungs;alveoli;diaphragm;ribs / rib eye / intercostal muscles;

[5]

REPRODUCTOR

ESPERMATOGÉNESIS Y OVOGENÉSIS

Compare the processes of spermatogenesis and oogenesis.

both involve meiosis;both involve cell proliferation / mitosis (before meiosis);both involve cell growth / enlargement (before meiosis);LH / FSH involved in both;testes versus ovaries;spermatogenesis starts at puberty versus oogenesisstarts in the fetus;spermatogenesis until death versus oogenesis until menopause;spermatogenesis continuously versus oogenesis in a cycle;millions of sperm daily versus one egg per month;ejaculation of sperm any time versus ovulation in middleof menstrual cycle;four sperm per meiosis / spermatogonium versus oneegg per meiosis / oogonium;spermatogenesis involves equal divisions versus oogenesisinvolves unequal cell / cytoplasm divisions;no polar bodies in spermatogenesis versus 2 or 3 polarbodies in oogenesis;spermatogenesis involves Sertoli / nurse cells versus oogenesis does not;meiosis II completed before fertilization in spermatogenesis

versus after in oogenesis;testosterone needed for spermatogenesis versusnot needed for oogenesis;

[7]

RESPIRACIÓN

EXPLIQUE PORQUÉ LAS TASAS DE RESPIRACIÓN VARÍAN CON EL EJERCICIO

Explain how and why the breathing rate varies with exercise.

oxygen is becoming limited;CO2 concentration builds up in blood;lactic acid builds up in blood;lowers blood pH;chemosensors detect lowered pH;sensors in carotid artery / aorta;send impulses to breathing centre / brain stem;impulse sent to diaphragm;impulse sent to intercostal muscles;increases / decreases rate of breathing / contraction / relaxation of muscles;involuntary control;breathing rate increases to remove more CO2 from blood / lungs;

CIRCULATORIO

DESCRIBA EL MECANISMO DE CONTROL DE LATIDOS DEL CORAZÓN

Describe the mechanisms that control the heartbeat.

Myogenic / initiated in heart muscle itself;SA node / pacemaker sends waves of excitation / impulse to atria;stimulus to the AV node;conducting fibres / bundle of His / Purkinje fibres conduct impulses to lower ventricles;moderated by ANS / vagus nerve / parasympathetic;

CIRCULATORIO

DIBUJO DEL CORAZÓN CON RÓTULOS

Draw a labelled diagram to show the internal structure of the heart.

left and right ventricle;left and right atria;atrioventricular valves / bicuspid / mitral and tricuspid valves;semilunar valves;aorta and vena cava;pulmonary artery and pulmonary vein;ventricle wall thicker than atria;left ventricle wall thicker than right ventricle wall;

RESPIRATORIO

NECESIDAD Y MECANISMO DE VENTILACIÓN PULMONAR

Explain the need for, and the mechanism of, ventilation of the lungs in humans.

draws fresh air / oxygen into the lungs;removal / excretion of CO2;maintains concentration gradient of O2 / CO2 / respiratory gases;

diaphragm contracts;(external) intercostal muscles contract;increased volume (of thorax / thoracic cavity);decreasing air pressure in lungs;air rushes in down air pressure gradient;

converse of the above causes exhalation;abdominal muscles contract during active exhalation;elastic recoil of lungs helps exhalation; 8 max(Plus up to [2] for quality)

CIRCULATORIO

CONTROL DE LOS LATIDOS

the heart is myogenic / beats on its own accord;60-80 times a minute (at rest);coordination of heartbeat is under the control of pacemaker;located in the muscle / walls;sends out signal for contraction of heart muscle;atria contract followed by ventricular contraction;fibres / electrical impulses cause chambers to contract;nerve from brain can cause heart rate to speed up;nerve from brain can cause heart rate to slow down;adrenalin (carried by blood) speeds up heart rate;artificial pacemakers can control the heartbeat; 6 max

EXTRUCTURA Y FUNCIÓN DE LOS VASOS SANGUÍNEOS HUMANOS

(c) Explain the relationship between the structure and function of blood vessels that are found in a human.

(c) Answers must refer to all three vessels to achieve [8 max].

arteries: [3 max]thick muscle layers / elastic fibres to help pump blood;thick collagen / fibres to avoid bursting / withstand high pressure;narrow lumen relative to overall diameter;narrow lumen to maintain pressure;

veins: [3 max]thin muscle layers with few fibres because blood not under highpressure;thin so they are able to be pressed by muscles to pump blood;wide lumen relative to overall diameter;wide lumen to maintain blood flow / decrease resistance to flow;contains valves to prevent backflow;

capillaries: [3 max]single layer of (thin) cells for diffusion;pores between cells so phagocytes can squeeze out;narrow lumen to fit into small spaces;large number resulting in increased surface area; 8 max

RESPIRATORIO

VCARACTERÍSTICA DE LOS ALVEÓLOS COMO ESTRUCTURAS EFECIENTES EN EL INTERCAMBIO DE GASES

List the characteristics of alveoli that permit efficient gas exchange.

large total surface area;wall of single layer of flattened cells;moist lining;walls elastic;network of capillaries;capillary walls are thin / one cell thick; 4 max

(4)

SISTEMA CIRCULATORIO

ESTRUCTURA DE LAS ARTERIAS Y VENA RELACIONADA CON SUS FUNCIONES

(b) Describe the structures of arteries and veins as related to their functions.(6)

(b) Each characteristic must be linked to a function for the mark to be awarded.Arteries: Award [3 max]thick muscular wall to help pump blood / to help distribution of blood;thick outer wall (of collagen and elastic fibres) to withstand highpressure / to avoid bursting / leaks;narrow lumen results in fast-moving blood;

veins: Award [3 max]thin outer muscular walls so no pumping action;thin walls allow pressure from surrounding muscles to move blood;thin walls (of collagen and elastic) as not likely to burst / low pressure;wide lumen allows for slow-moving blood;valves to prevent back flow / control direction of blood flow; 6 max

TEMA 3 RESPIRACIÓN

EXPLIQUE EL PROCESO DE RESPIRACIÓN AERÓBICA

(c) cell respiration produces energy;controlled release of energy;by breakdown of organic molecules / glucose;energy from them is used to make ATP;aerobic respiration is in mitochondria;requires oxygen;pyruvate is produced by glycolysis / glucose broken down;pyruvate is broken down in the mitochondria;into carbon dioxide and water;large production of ATP;per molecule / mass of glucose;much higher production of ATP than in anaerobic respiration; 8 max

TEMA 6 SISTEMA NERVIOSO

DIAGRAMA DE UNA NEURONA MOTORA

Draw a labelled diagram showing the structure of a motor neurone.

ward [1] for each of the following clearly drawn and correctly labelled.cell body - complete with nucleus and dendrites;axon - shown longer than the longest dendrite, with the membrane drawn as acontinuous line;myelin sheath - surrounding the axon, showing nodes of Ranvier;motor end plates - not covered by myelin sheath and ending in a button / dot; 4

(4) (6)

(b) Outline how heartbeat is controlled as the body goes from rest to hard exercise.

(b) heart muscle is myogenic / pacemaker;rise in CO2 detected in medulla of brain;nerve impulse sent to pacemaker;sympathetic / parasympathetic control;modifies heart beat;SA node initiates contraction of atria;impulses (from SA) cause AV node to contract ventricles;transmitted through Purkinje fibres;output rises;CO2 level falls; 6 max

Allow converse of above