BMAT 2009-S2

Explanation

The correct answer is C.

Let dominant allele = P, recessive allele = p.

A: homozygous dominant = PP; B: homozygous recessive = pp

C and D are 100% heterozygous dominant. For F homozygous recessive:

1. i) E is homozygous recessive:

E alleles = pp

Ratio = 1 (PP) : 1 (pp)

Hence, there is a 50% probability that F is homozygous recessive

1. ii) E heterozygous:

E alleles = Pp

Ratio = 1 (PP) : 2 (Pp) : 1 (pp) – 1+2+1=4. pp = 1⁄4

Hence, there is a 25% probability that F is homozygous recessive

Explanation

The correct answer is E.

Alkenes form addition polymers – the carbon-carbon double bond ‘opens up’ to form single carbon-carbon bonds with adjacent monomers. 1 and 3 are haloalkanes, so do not contain C=C bonds, and hence cannot form addition polymers. 2 is an alkene (as its molecular formula adheres to the general formula CnH2n) so is can under addition polymerisation. 4 and 5 are haloalkenes, so do have C=C bonds and can form addition polymers. So compounds 2, 4 and 5 can undergo addition polymerisation.

Explanation

The correct answer is C.

Resultant Force = 900N – 600N = 300N

Hence, force = upwards. a = F/m ; 300/60 = 5 ms-²

Explanation

The correct answer is C.

The total number of balls: x+y+z

The probability of red: x/(x+y+z) , blue: y/(x+y+z) , yellow: z/(x+y+z)

Red first: x/(x+y+z) X blue second: y/(x+y+z) = 2xy/(x+y+z)²

Explanation

The correct answer is E.

Cloning produces another organism, which is genetically identical to its parent organism – it contains the same genetic material.

Clones do not always show identical features at maturity, as the genes may be expressed differently as characteristics, dependent upon various transcription factors that dictate gene expression. Multiple births (I.e. twins, triplets etc.), are not always members of a clone. This is as, non-identical twins/triplets etc. can occur due to the release of multiple eggs at ovulation, which are subsequently fertilised by multiple sperms. The genetic material of the sperms and eggs differ from each other, due to genetic recombination (crossing over) in meiosis. Hence, they can express different characteristics. Members of a clone cannot be produced through a mutation; if this occurred, then their genetic material would differ immensely, and so they would be genetically non-identical – not members of a clone.

Explanation

The correct answer is B.

SiO₂ can exist as a giant structure – a covalent macromolecule, as it is held by strong covalent bonds. The strong covalent bonds link all the atoms together – a Si bonded to an O bonded to a Si bonded to an O etc.

Explanation

The correct answer is E.

P = VI ; P = watts, I = amps. V = P/I. Hence, V = watts/amps = watts per amp

Explanation

The correct answer is B.

Unit length is defined as a length of 1. To find the diagonal of the base, use the Pythagorean Formula: √(1²+1²) = √2

The length of the midpoint of the diagonal: √2/2

Repeat usage of Pythagorean Formula: (the vertical height is 1, the base length to midpoint is √2, and the length in question is the hypotenuse of this triangle)

Hence, √((√2/2)²+1²) = √(1/2 + 1) = √(3/2)

Explanation

The correct answer is D.

Statement D is incorrect. Statement A is correct, as the risk increases by 0.5 (1.0 ! 1.5 and 4.0 ! 4.5) in both types of alcohol intake. Statement B is correct, as there is a positive correlation of increase between the variables of number of mutant alleles present and risk value; as the number of mutant alleles present increases, so does the risk. Statement C is correct, as the figures for heavy drinking significantly increase the risk from being in the range of 1-1.8, to 4-6 which is an increase greater than fourfold. Statement E is correct, as the difference between the risk values with 1 and 2 alleles is 1.5 for heavy drinkers (6 – 4.5 = 1.5), whereas it is only 0.3 (1.8 – 1.5) for light drinkers. Statement D is incorrect, as the presence of at least one mutant allele is not the main factor for an increase in risk – this contradicts Statement C, which has proven that heavy drinking is the main factor which increases risk.

Explanation

The correct answer is E.

Mr (CO₂) = 12 + 2(16) = 44

Ratio of C:Mass of CO₂ = 12/44 = 3/11

Hence, 4.77g of CO₂: 3/11 x 4.77 = 1.3g of C

For 2g of Carbon (Percentage by mass): Mass/Actual x 100 = 1.3/2 x 100 = 65%

Explanation

The correct answer is C.

The radiation is Beta, as beta particles have a short range in air, a few cm, and a short half life of a few hours too – all values for half life are within the range of 2-3 hours. It cannot be alpha, as the range of alpha is too short – 3-5 cm. For half life: count rate initially = 220. Count rate halved at 110. Graphically, this corresponds to 2.40 hours – it cannot be 2.76 hours, as on the graph, the point is less than halfway. Detector 2 has a constant reading, as the range of beta particles is around 15cm, and so there is a constant rate of minimal beta particles being detected.

Explanation

The correct answer is C.

This question may appear to be confusing, However, this is just a substitution and calculation question. Firstly, identify that y X (mathematical binary operation) x = yᵡ/x

Let mathematical binary operation =

Hence, wherever that expression is seen, replace it with yᵡ/x, where x and y are defined.

For (23)2 Firstly, y = 2, x=3.

Hence, 23/3 = 8/3

Then, y = 8/3, x=2

Hence, (8/3)²/ 2 = 64/9/2 = 32/9

Explanation

The correct answer is B.

If oxygen concentration in the blood becomes very low, all other processes, apart from B, are unaffected. This is as, processes A and C are gaseous exchange – if the blood oxygen concentration is low, oxygen can pass from the alveoli to the blood, down a concentration gradient. Similarly, the concentration of carbon dioxide in the blood will be high, due to the previous usage of oxygen in respiration to produce carbon dioxide, thus carbon dioxide also passes out of the blood, into the alveoli, down a concentration gradient. Water from the blood plasma passes into the muscle cells and nephron via osmosis, which does not require oxygen. Urea passes from the blood plasma into the nephron via diffusion, which does not require oxygen either. Only process B is affected. This is as, glucose enters the villi, from the lumen, via the glucose-sodium co-transport mechanism – facilitated diffusion. Here, glucose passes into the epithelial cells on the villi lining due to the presence of sodium ions. The sodium-potassium pump on the cell membrane of the epithelial cell bordering the capillary in the villi, actively transports sodium ions against their concentration gradient, out of the epithelial cells (and couples the transport of potassium ions into the cell). This causes a low concentration of sodium ions, promoting the entry of sodium ions, which couple with glucose, into the epithelial cell via the lumen. Due to a constant concentration gradient established by the active transport of sodium ions, glucose continuously moves out of the epithelial cells, into the villi capillaries. Active transport requires oxygen. If there is insufficient oxygen, the active transport of sodium cannot occur, hence sodium accumulates in the cell, stopping the concentration gradient of glucose and sodium into the cell.

Explanation

The correct answer is B.

MSO₄ + J → JSO₄ + M – Reaction 2 would occur, as J is more reactive than M, and so it would displace it from MSO₄.

TO + Q → QO + T – Reaction 3 would occur, as Q is more reactive than T, and so it would displace it from TO.

QO + J → JO + Q – Reaction 4 would occur, as J is more reactive than Q, and so it would displace it from QO.

Explanation

The correct answer is D.

The trapezium (for 1 minute) can be calculated: (15 + (20×60)) x 1⁄2 = 607.5

Rectangle: (3×60) x (20) = 3600

Approximate area as triangle: (3×60) x 20/3 = 1200

Hence, 607.5 + 3600 + 1200 = 5407.5m nearest value is 6km

Explanation

The correct answer is F.

Simplify the expression

Explanation

The correct answer is F.

All Statements 1,2,3 and 4 are correct. Statements 1 and 2 – Competition can occur between individuals of the same species (intraspecific competition) and between individuals of different species (interspecific competition). Statements 3 and 4 – Selection of advantageous alleles, which are favoured by the environment, can lead to evolution of a species, as they are passed onto successive generations. However, if a species does not possess any advantageous alleles to suit the changes in the environment, the individuals cannot survive to breed successfully, hence their alleles are not passed onto any offspring, leading to extinction.

Explanation

The correct answer is D.

LHS: Cu = 1, H = 1, N = 1, O = 3. RHS: Cu = 1, H = 2, O = 8, N = 4

Using algebra:

Cu (1 x a = 1 x a) ; H (1 x b = 2 x c) ; N (1 x b = 2 xa+ 2);

O (3 x b = 6 x a +1 x c + 2)

Hence:

a=a

b=2c

b=2a+2

3b=6a + c + 2

We use substitution here:

6b=12a+2c+4

6b=12a+b+4

6(2a+2)=12a+(2a+2)+4

12a+12=12a+2a+2+4

12a+12=14a+6

2a=6

a=3

b=2a+2

b=6+2

b=8

b=2c

c=b/2

c=4

Hence, 3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 4H₂O + 2NO

Explanation

The correct answer is B.

Loss of GPE = gain in Ek

mgh=1/2mv2 ; h = 1⁄2 (v2/g) = 1⁄2 x (20)2/10 = 20

Explanation

The correct answer is D.

The question says that the cylinder has the same length as the internal diameter of the sphere. Hence, h (length) = 2r for the cylinder

To find the fraction: Volume of sphere/Volume of cylinder

3/4πr³/ (πr²h)=3/4πr³/ (πr²(2r)) = 2/3

Explanation

The correct answer is D.

The blood in the capillaries is deoxygenated, with high carbon dioxide concentration. This is as oxygen is used by the cells for respiration, which produces carbon dioxide, which passes into the blood capillaries. This high concentration of carbon dioxide reaches the alveoli. Due to the air in the alveolus having a higher concentration of oxygen, relative to the capillaries, oxygen passes down a concentration gradient from the alveolus to the capillaries. The reverse occurs for carbon dioxide, as the blood capillaries has a greater carbon dioxide concentration, relative to the air in the alveolus. Hence, carbon dioxide moves out of the capillaries, into the alveolus, to be exhaled.

Explanation

The correct answer is D.

Equation 2 is very fast, as it occurs between oppositely charged ions, which are attracted to each other due to electrostatic forces of attraction between them. Ag⁺ + Cl- rapidly combine AgCl.

Equation 3 is very fast as no bonds have to be broken. Also, the radicals combine rapidly, as they have a single unpaired electron in the outermost shell, as denoted by the dot. As both radicals have this, they combine to form a single C-C covalent bond, forming C₂H₆ (formed from .CH₃ + .CH₃).

Equations 1 and 2 are slow. Equation 1: H₂ needs to break up into 2 single H atoms, and I₂ needs to break up into 2 single I atoms. Then, 2HI molecules are formed separately. Hence, bonds are broken.

Equation 2: Firstly, there is no attraction to the negatively charged OH- ion, as the CH₃Br is uncharged. Secondly, via electrophilic substitution, the OH- needs to replace the Br=, which involves bond breaking.

Explanation

The correct answer is A.

F=ma

15000 = (20000+2(5000))a

a=1/2

15000 – T = (20000+5000)a

T = 15000 – 12500 = 2500

Explanation

The correct answer is A.

Add 10 to both sides: y + 10 =  5((x/2)-3)²

Divide by 5 on both sides: (y+10)/5 = ((x/2)-3)²

Square root both sides (remembering that there are positive and negative square roots): ± √((y+10)/5) = ((x/2)-3)

Add 3 to both sides: 3 ± √((y+10)/5) = x/2

Multiply by 2 on both sides: 6 ± 2(√((y+10)/5)) = x

Explanation

The correct answer is F.

Statement 1 is incorrect – insulin regulates blood glucose level, not water content. ADH regulates water content of the body.

Statement 2 is incorrect – Homeostasis is not only dependent on hormones – the nervous system can influence the release of hormones, such as the release of hormones noradrenaline and acetylcholine at the SAN to regulate heart rate, when detected by chemical and pressure changes in the blood flowing through the medulla oblongata in the brain, via the parasympathetic (decreases heart rate) and sympathetic (increases heart rate) nervous systems. Statements 3,4 and 5 are all correct. The pancreas produces insulin to control glucose content of the blood. Both nervous and hormonal systems are involved in homeostasis (which contradicts Statement 2), and thermoreceptors on the skin can help to control body temperature.

Explanation

The correct answer is C.

In CH2BrCl, the CH2 will be constant. Hence, Ar (CH2) = 12 + 2 = 14.

Hence, the variant part is: 128 – 14 = 114

To get 114, the only combination is: 35 + 79 = 104

There is 1⁄2 chance of 79 – Br isotope, and 3⁄4 chance of getting the 35 – Cl isotope.

As they are independent, multiply the fractions together, as they are probabilistic quantities: 1⁄2 x 3⁄4 = 3/8

Explanation

The correct answer is E.

The displacement distance graph gives the wavelength of the wave. The wavelength is the distance between peak to peak, or trough to trough of a wave. However, only the total distance is given. There are 2 waves within that distance, and the distance is 60m. Hence, the wavelength = 60/2 = 30.

The displacement time graph gives the time period of the wave. The time of the waves is 0.6s, and there are 3 waves. Hence, the time period: 0.6/3 = 0.2s. The frequency is 1/time period. Hence, 1/0.2 = 5.

As c=f�, 30 x 5 = 150.