Principles MCQs Flashcards

Question

**A form of glia responsible for producing myelin in the central nervous system** ## Footnote A - Astrocytes B - Cardiac muscle fibres C - Chondrocytes D - Mast cells E - Microglial cells F - Mucous cells G - Oligodendrocytes H - Osteocytes I - Skeletal muscle fibres

Answer 1

**G - Oligodendrocytes** ## Footnote Three of the cell types listed are central nervous system glial cells: astrocytes, microglia and oligodendrocytes. Astrocytes have a number of functions including support and maintaining homeostasis in the extracellular environment, microglia are immune surveillance cells, but only oligodendrocytes produce myelin in the CNS (as opposed to Schwann cells, which produced myelin in the peripheral nervous system).

Answer 2

**C - Chondrocytes** ## Footnote Chondrocytes are the resident cells of cartilage. Indeed the prefix ‘chondro’ means cartilage (comes from the Greek word for cartilage ‘chondros’).

Answer 3

**C - increase the velocity of a reaction by decreasing the energy of activation**

Answer 4

**C - 4** ## Footnote For each glucose molecule that enters the glycolytic pathway, two ATP molecules are initially consumed to phosphorylate the glucose. Later, the phosphorylated hexose is split into two phosphorylated triose. Each triosephosphate is converted into pyruvate, and in that process, two ATP molecules are formed per triosephosphate.

Answer 5

**B - It is a protein other than RNA polymerase that is involved in transcription** ## Footnote Transcription factors are proteins, and are NOT subunits of RNA polymerase. Furthermore, they don’t contain nucleic acids. They also are NOT any sequences within the DNA of a cell, but most transcription factors can bind DNA in a sequencespecific manner, i.e. they will bind only to very specific DNA sequences.

Answer 6

**A - RNA and proteins** ## Footnote Ribosomes are nucleoprotein complexes and consist of rRNA molecules (four different ones in humans) and a large number of protein subunits, but no DNA or carbohydrates.

Answer 7

**A - The relative orientation of one polypeptide to another polypeptide in a multisubunit protein** ## Footnote Quaternary structure only refers to the relative orientation of different polypeptide subunits in a multisubunit complex. The overall shape of a polypeptide is termed its tertiary structure, and the path of the peptide backbone in threedimensional space refers to secondary structure elements like helices and sheets.

Answer 8

**A - From the 5'end to the 3'end on both strands** ## Footnote During DNA synthesis both strands of a double helix are replicated. ALL nucleic acids are always polymerised from the 5’ end towards the 3’ end, because additional nucleotides can only be added to a free 3’ hydroxyl group.

Answer 9

**A - The extent to which a buffer solution can counteract the effect of added acid or base** ## Footnote The capacity of a buffer has nothing to do with the actual pH of the solution, nor the molecular weight of the buffering substance, nor with commercial antacids. The ratio between acid and conjugate base in solution determines the pH of this solution, but not how well a solution can buffer. The buffering capacity simply refers to how well a buffer can resist changes in pH when acid or base is added.

Answer 10

**A - It allows for the regeneration of NAD+** ## Footnote This is a reaction that occurs in many microorganisms, but also in eukaryotic cells. It also occurs in highly active human muscle cells when not enough oxygen can be delivered to the cell for its requirements. As a consequence, the cell can not generate enough ATP by oxidative phosphorylation, but has to resort to substrate level phosphorylation using increased glycolysis. This generates more NADH than can be reoxidised by the electron transport chain. To allow glycolysis to continue, NAD + has to be regenerated, that occurs by the reduction of pyruvate (the product of glycolysis) to lactate. This reaction is not linked to the phosphorylation of ADP. Lactate is actually involved in generating the muscle pain after strong exercise.

Answer 11

**E - Signalling is terminated by hydrolysis of GTP to GDP by the BTPase activity of the G-protein a subunit** ## Footnote A) is incorrect as guanine nucleotide exchange occurs at the a subunit of the Gprotein B) is incorrect as all betaadrenoceptors signal primarily through the Gs Gprotein C) is incorrect as dissociation of the agonist from the receptor has no effect on the activated Gprotein D) is incorrect as Gprotein coupled receptors are a single protein

Answer 12

**C - The position of the agonist concentration response curve is shifted to the right in a parallel manner with no change in the maximum response** ## Footnote A) is incorrect because a rightward parallel shift occurs B) is incorrect because the maximal response is not depressed (this statement describes the action of a noncompetitive antagonist) D) is incorrect because the shift is parallel with no depression of the maximum response E) is incorrect because the shift is parallel

Answer 13

**D - Stimulation of the sympathetic division decreases heart rate and force** ## Footnote A) incorrect – parasympathetic stimulation causes erection, sympathetic stimulation cause ejaculation B) incorrect sympathetic stimulation decreases motility of the G.I. tract C) incorrect sympathetic stimulation increases heart rate E) incorrect – sympathetic stimulation causes bronchodilatation (via the release of adrenaline from the adrenal medulla)

Answer 14

**A - The excitatory postsynaptic potential (epsp) is caused by the activation of the nicotinic acetylcholine receptors composed of α3 and β4 subunits** ## Footnote B) incorrect transmission is terminated by hydrolysis of ACh by extracellular acetylcholinesterase C) incorrect amphetamine displaces noradrenaline for storage vesicles at noradrenergic synapses D) incorrect the a4b2 receptor is found in the CNS, not the autonomic ganglia E) incorrect atropine locks muscarinic, not nicotinic, ACh receptors

Answer 15

**D - α2-adrenoceptor** ## Footnote A) incorrect b1 receptors are located, for example, in the heart B) incorrect muscarinic receptor can act as autoreceptors at parasympathetic neuroeffector junctions C) incorrect a1 receptors are located, for example, on vascular smooth muscle D) correct E) incorrect b2 receptors are located, for example, in airway smooth muscle

Answer 16

**B - Ionised drugs of low molecular weight that are not protein bound move freely between most capillaru circulations and the interstitial space** ## Footnote A) incorrect – the surface area of the stomach is much less than that of the small intestine. The latter is largely responsible for the absorption of orally administered drugs B) correct C) incorrect – some drugs (e.g. Ldopa), are absorbed via transport systems D) incorrect – being polar such drugs cannot readily cross phospholipid bilayers unless assisted by transport systems E) incorrect – the enteral route includes buccal, sublingual and rectal routes that either completely, or partially, avoid a ‘first pass’ through the liver

Answer 17

**D - The sympathetic nerve fibres innervating the adrenal medulla utilize acetylcholine as their neurotransmitter** ## Footnote A) incorrect – the transmitter is always ACh B) incorrect – the preganglionic fibres have a cranial, or sacral, outflow C) incorrect – they are usually embedded in the target organ (with the exception of some ganglia in the head) D) correct E) incorrect – the transmitter is noradrenaline (with the exception of the innervation to the sweat glands where the transmitter is unusually ACh)

Answer 18

**C - Amphetamine** ## Footnote The only other plausible alternative would be cocaine (F) which is ruled out because although it binds to U1 it is not transported as a substrate and does not cause Ca 2+ independent release of noradrenaline.

Answer 19

**E - Atropine** ## Footnote The only other drug that binds to muscarinic receptors is muscarine which is excluded because it is an agonist, rather than an antagonist

Answer 20

**J - Salbutamol** Atenolol (D) which also binds to badrenoceptors is excluded because it is an antagonist and b1 selective. Noradrenaline (B) is excluded as it is not b2 selective. Prazosin (I) is incorrect because it is an a1blocker.

Answer 21

**E - Intravenous** ## Footnote Clues are (i) 100% availability (ii) rapid onset of action and (iii) total avoidance of first pass. Collectively, these rule out any other option

Answer 22

**G - Rectal** ## Footnote Buccal and sublingual are ruled out because those routes totally, rather than partially, avoid fist pass and they are hardly suited to nocturnal dosing.

Answer 23

**B - Inhalational** None of the other routes match the description well

Answer 24

**D - Arteriolar vasodilatation** ## Footnote The baroreceptor response to decreased mean arterial blood pressure includes arteriolar vasoconstriction and not arteriolar vasodilatation. Arteriolar vasodilation would decrease the total peripheral vascular resistance and hence further decreases (rather than increase) the mean arterial blood pressure. All the other options are part the baroreceptor response to decreased mean arterial blood pressure.

Answer 25

**B - 70-105 mmHg** ## Footnote A mean arterial blood pressure of at least 60 mmHg is needed to adequately perfuse the vital organs including e.g. the heart, brain and kidneys. The mean arterial blood pressure should be high enough to perfuse the body organs, but not too high to damage them, damage the blood vessels or place an extra strain on the heart.

Answer 26

**E - - 70mV**

Answer 27

**C - Negative feedback opposes the initial change in a controlled variable** ## Footnote All the other statements are incorrect: Feed forward occurs in anticipation of a change. Negative feedback (and not positive feedback) systems are the main type of control mechanisms in the body. Control of blood pressure is an example of a negative (and not positive feedback) system. Negative feedback helps with (rather than opposes) stability of the internal environment.

Answer 28

**E - Heat exposure decreases muscle tone** ## Footnote All the other options are incorrect: Body temperatures of 4042 degree Celsius indicate hyperthermia. Hypothermia is indicated by body temperature at or below 35 degree Celsius. The anterior hypothalamic centre is stimulated by warmth not cold. The posterior hypothalamic centre is stimulated by cold. Vasoconstriction of skin arterioles is caused by sympathetic and not parasympathetic nerves.

Answer 29

**C - Stimulation of the vagus nerve slows down the heart rate** ## Footnote The vagus nerve provides the parasympathetic supply to the heart. All the other answers are incorrect: Vasoconstriction increases (rather than decreases) the total peripheral vascular resistance and mean arterial blood pressure. Vascular smooth muscles are predominantly supplied by sympathetic rather than parasympathetic nerves. Under resting conditions, the vgal tone and not the sympathetic tone dominate on the heart. The vasomotor tone is caused by tonic discharge of sympathetic and not parasympathetic nerves.

Answer 30

**F - The condition can only be transmitted from an affected mother to her children** ## Footnote Mitochondrial DNA is inherited from the mother.

Answer 31

**D - Where one child is affected in the family, the risk of the next child, to the same parents, being affected is 1 in 4.** ## Footnote Only one child affected so the parents must be carriers (heterozygous).

Answer 32

**B - There is no male to male transmission of the condition** ## Footnote Since males only have one X chromosome and male progeny receive their X-chromosome from the mother, any defect on the paternal X-chromosome will not be passed on to male progeny.

Answer 33

**E - A female with normal intellegence and infertility** ## Footnote Turner's syndrome.

Answer 34

**D - A normal female** ## Footnote In constitutional balanced translocations there is commonly no abnormal phenotype since there is no loss or gain of DNA.

Answer 35

**B - A child with Down synrome** ## Footnote Trisomy 21 - constitutional

Answer 36

**C - RNA**

Answer 37

**D - An adenocarcinoma** ## Footnote Adeno' pertaining to a gland, 'carcinoma' meaning cancer (malignant).

Answer 38

**C - Hypoplasia is a developmental disorder** ## Footnote Apoptosis can also be a physiological response e.g. during embryonic development or T cell development.

Answer 39

**C - The prognosis declined with increasing stage of disease** ## Footnote As the cancer starts to involve additional anatomical areas (stage) the prognosis worsens

Answer 40

**A - Hypertrophy** ## Footnote Fact - increase in cells would be hyperplasia.

Answer 41

**C - Human papilloma Virus** ## Footnote The intended answer is Human Papilloma Virus. The others do not cause cancer in man.

Answer 42

**G - p53** ## Footnote The gene TP53 is often mutated in cancer and results in a non-functional protein.

Answer 43

**B - Caspase** ## Footnote Fact - hence the ion of these proteins result in uncontrolled proliferation and survival of cells.

Answer 44

**E - c-myc** ## Footnote Fact - due to chromosomal translocations that juxtapose c-myc with immunoglobulin gene promotes (usually heavy chain e.g. t(8 ;14))

Answer 45

**A - Endothelial injury**

Answer 46

**C - Intimal accumulation of macrophages**

Answer 47

**F - Plaque rupture**

Answer 48

**C - Herpes simplex virus** ## Footnote The correct answer is Herpes Simplex Virus, latency is characteristic of the herpes viruses. None of the other options are herpes viruses.

Answer 49

**H - Sexual intercourse** ## Footnote Unprotected sexual intercourse is the most likely explanation as the symptoms suggest a sexually transmitted infection.

Answer 50

**D - Faecal-oral route** ## Footnote The symptoms of gastroenteritis are most likely due to food poisoning (acquired via the faecal oral route).

Answer 51

**A - Blood-blood spread** ## Footnote Hepatitis A is unlikely as the incubation period is less than 6 weeks (and is mainly spread via the faecal oral route): hepatitis C unlikely, though it can be spread via tattooing practices the incubation is usually less than 12 weeks and 90% don't have jaundice. This is most likely to be hepatitis B, spread by blood to blood contact on improperly sterilised equipment, the incubation period is 6 weeks to 6 months and about half of infected adults have jaundice.

Answer 52

**H - Pattern recognition receptor** ## Footnote Innate immune cells such as macrophages recognise pathogens using PRRs (Pattern Recognition Receptors).

Answer 53

**G - Membrane attack complex** ## Footnote The Membrane Attack Complex (MAC) of the complement system can directly lyse pathogens via membrane insertion and osmotic lysis.

Answer 54

**B - C-reactive protein** ## Footnote Proteins of the immune system that can promote pathogen phagocytosis are known as Opsonins (the process is known as Opsonisation). Opsonins include the acute phase protein C reactive protein, the complement protein C3b and antibodies of the IgG class.

Answer 55

**C - C3** ## Footnote C3 is the key mediator of the complement system - it is activated by all three activation pathways.

Answer 56

**F - TNF alpha** ## Footnote Only cytokine in possible answers (TNF)

Answer 57

**A - Neutrophil** ## Footnote Neutrophils play a critical role in the early innate immune response. This is therefore the best answer. Mast cells are also involved in some responses e.g. allergy, but overall, neutrophils are much more important.

Answer 58

**E - Liver cell**

Answer 59

**G - Lifestyle** ## Footnote His job is so busy that his perception is that he has no time to exercise. In fact, this may not be the case, and if he were your patient, you would be trying to find ways of incorporating exercise into his daily routine, rather than suggesting he alters that routine dramatically. Other possible answers might have been C or I, but the best place to start is to try to alter his lifestyle.

Answer 60

**J - Social support** ## Footnote The man has just lost his wife (you can assume they were married for along time) and will be going through the grieving process, trying to find a new routine for life, and handling all of the administrative and financial issues associated with a death. He is having to do this without the immediate, physical and practical support of his family, as they are on the other side of the world. Whilst they may be very supportive in principle, there’s a limit to what can be done on the phone or email.

Answer 61

**D - Environment** ## Footnote The biggest immediate threat to the health of this worker is from infection. That risk will be moderated by other environmental factors, such as access to clean water and sanitation. Possible other factors might be G, as individual behaviour can alter risk (handwashing for example); or H, as if they do get infected, the medical support may be rudimentary at best.

Answer 62

**D - In between patients when hands are socially clean** ## Footnote A, B, C, E are incorrect as if hands soiled exposure to MRSA, C. difficle due to perform aseptic procedure or used gel several times need to wash hands.

Answer 63

**B - Blue bag** ## Footnote B: Correct - confidential. A: Household waste. C: Clinical waste. D: Semi-clear red for soiled laundry. E: Theatre / anatomy clinical waste e.g. amputated digits.

Answer 64

**C - Personal Protective Equiptment**

Answer 65

**B - Brachial**

Answer 66

**C - Situation Bcakground Assessment Recommendation**

Answer 67

**G - Yellow sharps bin with blue lid** ## Footnote Yellow sharps blue lid = medications vials with residual medicine

Answer 68

**A - Black bag** ## Footnote Black bag = Household waste

Answer 69

**E - Orange bag** Orange bag - Clinical waste

Answer 70

**D - D** ## Footnote A: Airway assessment B: Breathing assessment C: Circulation assessment D: Disability assessment in which glucose monitoring is integral E: Evidence, environment, exposure

Answer 71

**C - Non-technical skills** ## Footnote A: Human factors does not provide a framework B: Communication is a recognised human factor but only one element of human factors C: Correct - sometimes referred to as non-technical skills, human factors are the social and cognitive skills which support and underpin performance of physical and technical skills. D: Human factors are not tools for patient assessment E: Technical skills are general practical procedures.

Answer 72

**D - Allergies, Medication, Past medical History, Last ate or drank & Events prior to now**

Answer 73

**B - 1** ## Footnote RESP Rate - 0 Heart Rate - 0 BP - 0 Temp - 1 SpO2 - 0 (patient known to have COPD therefore target range is 88-92%) AVPU - 0 NEWS score = 1

Answer 74

**A - 0** ## Footnote Resp Rate - 0 Heart Rate - 0 Sp02 - 0 BP - 0 Temp - 0 AVPU - 0 NEWS score = 0

Answer 75

**H - 14** ## Footnote Resp rate - 3 Heart rate - 1 Sp02 - 2 O2 therapy - 2 BP - 3 Temp - 0 AVPU - 3 NEWS score = 14

Answer 76

**E - Escherichia** ## Footnote They belong to the genus Escherichia (Escherichia is the genus name, coli is the species name)

Answer 77

**J - Endotoxin** ## Footnote Gram negative bacilli produce endotoxin, which is derived from the Gram negative cell wall

Answer 78

**A - Gram negative bacilli** ## Footnote These are rodshaped organisms (bacilli) and stain pink/red with Gram stain Gram negative bacilli

Answer 79

**B - Gram positive cocci** ## Footnote These are round bacteria (cocci) staining blue/purple, i.e Gram positive cocci

Answer 80

**F - Staphylococcus** ## Footnote The cocci are arranged in grapelike clusters, so are likely to be Staphylococci

Answer 81

**G - Exotoxin** ## Footnote Gram positive organisms produce exotoxins (toxins exported from the bacterial cell)

Answer 82

**C - Dysplasia** ## Footnote Dysplasia refers to disordered growth. The cells have begun to accumulate genetic damage and have taken steps towards becoming cancer.

Answer 83

**C - Recieve trastuzamab** ## Footnote This relates to the EGHR pathway. Remember that Her2 is a type of EGFR and the target of herceptin. Herceptin is a trade name and the drug is called trastuzamab. There is controversy about how much the drugs cost - they are very expensive. Breaset cancers with EGFR mutations typically have a worse prognosis. Whilst trastuzamab is a good drug you would therefore rather not need it because it means you have a nastier tumour.

Answer 84

**A - acquired immunodeficiency syndrome** ## Footnote This is a case of exclusion. Human papilloma virus can cause cancer. Patients that have AIDs are more likely to contract infections many of which can cause cancer. Diabetes can be associated can be associated with obesity which carries an increased risk of malignancy but diabetes itself does not.

Answer 85

**D - malignant** ## Footnote These are all features of malignancy. Hyperplasia and metaplasia refers to mature cells with no genetic abnormalities and normal development. There are no irregularitief from cell to cell. The image encompasses all the features of malignancy. You can't tell what the cell of origin is and we would therefore call these cells poorly differentiated. There are large cells. There are calls with little cytoplasm (high n:c ratio). The nuclei are dark (hyperchromatic). There is great variation in size and shape (pleomorphism). The nuclei are atypical (asymmetrical and irregular contours). Mitoses are present, some of which are abnormal.

Answer 86

**D - poor differentiation** ## Footnote We can't tell what the cell of origin is so we would call this poorly differentiated and therefore of a high grade. Tumour stage on the other hand refers to hor far the tumour has spread. This is generally done using the TNM classiciation (Tumour, Nodes, Metastases). Local spread is covered un "T". Distant spread refers to nodal spread and distant metastes. Neither tumour stage or grade tell us about how quickly the tumour has grown. However, in general high stage and high grade tumours tend to be faster growing. Growth of tumours depends on a large number of other factors including the tumours blood supply.

Answer 87

**D - Pulse pressure is the difference between systolic arterial and diastolic arterial blood pressures** ## Footnote Blood pressure is "the outwards (hydrostatic) pressure exerted by the blood on blood vessel walls" In clinical practice we often measure the Systemic Arterial Blood Pressure and express it as "Systolic" and "Diastolic" blood pressures. Systemic Systolic Arterial Blood Pressure: "is the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart contracts": Systolic Pressure is normally \<140 mm Hg under resting conditions. Systemic Diastolic Arterial Blood Pressure: "is the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxes": normally \<90 mm Hg

Answer 88

**C - Effectors are heart and blood vessels**

Answer 89

**D - Vasoconstriction is caused by increased sympathetic activity**

Answer 90

Dizzy - Low arterial blood pressure as a result of blood loss - brain not getting normal perfusion and oxygenation. This can progress to confusion, lethargy and lodd of consciousness with more blood loss Breathless - Body trying to supply more oxygen to tissues

Answer 91

Arterial blood pressure decreases as a result of blood loss, low arterial blood pressure detected by baroreceptors, resulting in sympathetic stimulation and peripheral vasoconstriction. This helps raise systemic vascular resistance (SVR) and hence fight the drop in blood pressure.

Answer 92

Pulse is rapid (tachycardia) and weak. Arterial blood pressure decreases as a result of blood loss, low arterial blood pressure detected by baroreceptors, resulting in increased sympathetic and decreased parasympathetic activity to the heart - both of these increase heart rate. The pulse is weak due to loss of blood volume resulting in low stroke volume.

Answer 93

**D - In fever, a cold response raises the body temperature to a new set point**

Answer 94

**Answer: -79.4 mV**

Answer 95

**Answer: 56.2 mV**

Answer 96

**Answer: -74.9 mV**

Answer 97

**Answer: 115.2 mV**

Answer 98

**Answer: -62.6 mV**

Answer 99

**Answer: 99.7% (approx.)**

Answer 100

**Answer: 83.4% (approx.)**

Answer 101

**Answer: 35.3 mg (approx.)**

Answer 102

**Answer: 1.625 mg min-1**

Answer 103

**Numerical answer: (a) 90 min, (b) 120 min**

Answer 104

**Answer: 15 mg**

Answer 105

**Answer: 20**

Answer 106

**B - may occur spontaneously if coupled to a reaction in which the enthalpy change is negative and of greater magnitude**

Answer 107

**B - is likely to be irreversible in the cell**

Answer 108

**C - ATP is present at high concentrations in the cell**

Answer 109

**D - The reaction is likely to happen to a large extent, with large amounts of product formed**

Answer 110

**A - zero**

Answer 111

**B - A molecule with opposite charges at opposite ends**

Answer 112

**D - All of these answers are true**

Answer 113

**C - Hydrogen bonds involve a linea arrangement of one hydrogen atom between two electronegative atoms**

Answer 114

**A - Amino acids are classified according to the structures and properties of their side chains**

Answer 115

**A - an amino group (-NH2), a carboxyl group (-COOH), a hydrogen (-H), a side chain (-R)**

Answer 116

**C - Electron resonance between amino and carbonyl groups creates a partial double bond**

Answer 117

**A - *a-*amino group of one amino acid acts as a nucleophile to displace the hydroxyl group of another amino acid forming a peptide bond**

Answer 118

**C - The concentration of [H⁺] in solution A is 100 times that in solution B**

Answer 119

**A - Acid A dissociates to a greater extent in water than acid B**

Answer 120

**C - 3.40** ## Footnote pH -= -log[H⁺] [H⁺] = 0.0004M -log[0.0004] = 3.39794 or 3.40

Answer 121

**C - 5.0**

Answer 122

**True** ## Footnote Srtong acids favour [H+]. [A-} so ratio to [HA] gives a larger value. Since pKa = - logKa, pKa values become smaller with increasing acid strength.

Answer 123

**True** ## Footnote The carboxyl group donates [H+] = acid The amino group can accept [H+] and so can act as a base

Answer 124

**B - Zwitterionsare dipolar molecules which act as buffers of acids and bases** **D - Zwitterion ion charge may be positive or negative depending upon prevailing pH** **F - The overall charge of a zwitterion is neutral at a pH equivalent to the isoelectric point, pl**

Answer 125

**B - Hydrogen bonding between the C=O and N-H groups of peptide bonds**

Answer 126

**A - The arrangement of two or more polypeptide subunits into a single functional complex**

Answer 127

**A - Collagen contains a high proportion of hydroxylated proline residues**

Answer 128

**A - Proline**

Answer 129

**D - Through hydrogen bonds joining different parts of the peptide backbone**

Answer 130

**B - Glutamate and lysine**

Answer 131

**D - Cysteine**

Answer 132

**B - A discrete region of polypeptide chain that has folded into a self-contaned three dimensional structure**

Answer 133

**B - Hydrophobic interactions between hemoglobin tetramers cause aggregation**

Answer 134

**B - New nucleotides are added to the 3' end of growing nucleic acids**

Answer 135

**D - Replication does not require RNA molecules**

Answer 136

**C - They require additional factors to bind DNA**

Answer 137

**A - Non-coding sequences**

Answer 138

**A - It occurs in the cytoplasm**

Answer 139

**C - Proteins are synthesised from the N-terminus to the C-terminus**

Answer 140

**B - Starts with the first start codon from the 5' end of the RNA**

Answer 141

**B - It is ambiguous**

Answer 142

**C - Translation**

Answer 143

**B - Introduce a stop codon**

Answer 144

**B - A buffer is a solution to control the pH of a reaction mixture**

Answer 145

**D - It shows that the pH of a solution containing a weak acid is directly proportional to the concentration of the acid**

Answer 146

**B - All amino acids have D- abd L-isomers**

Answer 147

**C - In solutions of high pH amino acids are positivly charges**

Answer 148

**D - Hydrogen bonds**

Answer 149

**A - Hydrophobic interactions**