Paper 3 OCR Unified Biology specific revision 2021 QUESTIONS AND ANSWERS UPDATE 2023/2024, Exams of Nursing

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Difference between excretion and secretion - CORRECT ANSWERS Excretion is the removal of toxic, metabolic waste while Secretion is the release of substances by cells chi-square test - CORRECT ANSWERS - degrees of freedom = n-1 (no. categories-1)

• p = 0.
• how reliable/significant
• how likely it is to happen
• how "lucky" is the experiment data If the value in the table is smaller than the X^2 value, significant difference between O and E
• X^2 value = bigger, reject nul hypotheiss genetic engineering process in stages - CORRECT ANSWERS 1) Obtain required gene

2. Copy of gene is placed in Vector
3. Vector carries Gene into recipient cell
4. Recipient expresses new gene Methods of aiding DNA to cross recipient cell membrane: Heat Shock - CORRECT ANSWERS Heat Shock:

• 0 degress to 42 degrees
• calcium chloride --> walls and membranes become more porous --> Ca+ ions surround negative DNA + negative phospholipids in membrane, reducing repulsion How is PCR used to identify and compare - CORRECT ANSWERS - Amplified DNA sample for DNA Profiling
• to identify criminals or parentage DNA Profiling Procedure - CORRECT ANSWERS - STR, short variable sequences are used
• Number of STRS vary from person to person

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1. DNA obtained, amplified by PCR
2. Add restriction enzymes = fragments at specific recognition sites unique to the individual
3. Gel electrophoresis
4. Banding pattern is determined by the number and size of the different fragments
5. compare similarities of DNA banding patterns stratified sampling - CORRECT ANSWERS - dividing a habitat into areas which appear different

• sampling each area separately Advantages:
• ensures species are not underrepresented which can happen during random sampling
• ensures all habitats are sampled Disadvantages:
• may lead to overrepresentation of some species from small areas Preservation vs. Conservation - CORRECT ANSWERS Preservation states that we should protect our environment in a pristine, unaltered state. Conservation says we should put natural resources to use but that we have a responsibility to manage them wisely. - can have human intervention and emphasises sustainability. Conservation agreements - CORRECT ANSWERS - CITES
• The countryside Stewardship scheme
• Rio convention on Biological diversity CITES - CORRECT ANSWERS Convention on International Trade in Endangered Species
• aims to monitor trade of plants and animals
• ensures trade deosn't endanger the survival of population in the wild ETC

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The Countryside Stewardship Scheme - CORRECT ANSWERS Payments and grants are given to farmers in an effort to enhance and restore the English countryside Aims:

• to improve natural beauty and diversity
• to enhance and restore wildlife habitats and historical features of the countryside
• improve opportunities for public access Antibiotic resistant genes in Genetic engineering - CORRECT ANSWERS so that the GM plants and cells can be distinguished from non-GM ones. Phototropism - CORRECT ANSWERS A growth response to light
• so it can photosynthesise
• directional response t - test - CORRECT ANSWERS - compare 2 means
• x = mean of the data set
• n = number of data points in the data set
• s = Standard deviation of the data set
• ignore minus sign on top Significance:
• degree of freedom = (n1+n2)-
• if the calculated value is below the 5% significance Value then it is not significant plant growth hormone - CORRECT ANSWERS auxin = regulating plant growth
• apical dominance prevents lateral buds from growing
• high auxin in shoot keeps abscisic acid levels high in bud and it can't grow
• cytokinins can override the apical dominance effect and induce growth
• go to shoot tip

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• when shoot tip is cut off they are spread evenly around the plant. gibberellins = control stem elongation and seed germination Lub-dub heart sound - CORRECT ANSWERS Lub: closing of both AV valves during ventricular systole Dub: closing of both semilunar valves during ventricular diastole Effects of a hole in the septum of the heart? - CORRECT ANSWERS - Oxygenated and deoxygenated blood not separated as well
• Oxygenated blood returns to lungs
• Deoxygenated blood goes round the body
• Not as much oxygen is delivered to respiring tissues per second, at a lower rate
• Heart has to work much harder for the same amount of oxygen to be absorbed from the lungs and delivered to respiring tissues and cells Role of heart valves - CORRECT ANSWERS - prevent backflow of blood
• semi-lunar treatments of type 2 diabetes - CORRECT ANSWERS weight loss, diet, exercise and possibly oral medications that reduce amount of glucose the liver releases and boosts amounts of insulin released from pancreas Selective reabsorption in Collecting Duct - CORRECT ANSWERS The absorption of certain selected molecules back into the blood from the fluid in the nephron tubule. affects of ADH - CORRECT ANSWERS - High ADH means high reabsorption of water into the blood
• less urine
• ADH binds to receptors on collecting duct cells
• enzyme controlled reactions cause water-permeable vesicles to rise to surface of membrane
• this allows water to pass from collecting duct back into blood by osmosis Why do prokaryotes have a cytoskeleton? - CORRECT ANSWERS - cell division

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• protection
• shape + polarity determination in some Distal convoluted Tubule - CORRECT ANSWERS Between the loop of Henle and the collecting duct; Selective reabsorption and secretion occur here
• to regulate reabsorption of water and sodium proximal convoluted tubule specialised how? - CORRECT ANSWERS - cell cytoplasm has many mitochondria, active processes
• opposite of cell membrane is folded many times, many Na+ ion pumps and K= ion pumps between tissue fluid and blood
• highly folded to form microvilli, microvilli increase surface area for reabsorption
• cell surface membranes contain cotransporter proteins for Glucose and Amino acids
• 85% fluid is reabsorbed here
• all sugars, most mineral ions and some water Adaptations of the Kidney - CORRECT ANSWERS Podocytes:
• finger like projections = major processes
• minor processes
• ensure there are gaps between the cells

Kidney structure - CORRECT ANSWERS from the outside in: cortex, medulla, renal pelvis How is urea removed from the body? - CORRECT ANSWERS kidneys filter urea out of blood and concentrated in urine

• urea is actively moved into tubule

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• urea concentration rises as water is withdrawn from tubule Haemoglobin - CORRECT ANSWERS - takes up oxygen = oxyhaemoglobin
• heam group with single Fe2+ ion has high affinity for O
• 4 haem groups carry 1 Oz molecule each, 1 haemoglobin can carry 4 oxygen molecules
• S shaped curve for oxygen association/dissociation Fetal haemoglobin - CORRECT ANSWERS - higher affinity for oxygen
• curve to the left of adult
• fetal haemoglobin must be able to associate woth oxygen in environment where ppt of O2 is low enough for adult haemoglobin to dissociate with the Oxygen for it to pick up.
• eg. placenta
• fetal haemoglobin decreases the oxygen tension further
• oxygen diffuses from mother's blood to fetus