stpm_bio_p1_p2_skema

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JABATAN PELAJARAN NEGERI SEMBILANTRIAL STPM 2011

MARKING SCHEMEBIOLOGY 964Paper 1 (964/1)Paper 2 (964/2)


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PEPERIKSAAN PERCUBAAN BERSAMA STPMPAPER 1(96411)

Marking Scheme- BIOLOGY

-- NO ANSWER +- NO ANSWER--1 B 26 c~ 2 A 27 A- - " B 28 B- - c 29 B--tA 30 A6 B 31 I D-7 D 32 c8 c "" D9 A 34 B10 c 35 D-I 1 B 36 c- - 12 - -1 A 37 -- ~ D13 c 38 B14 D 39 c-15 I A 40 c'___ __._16 B 41 D17 D 42 A - - - - - - - --

~ _ _ _ _ 1 _ _ 8 D 43 D,--- 19 B 44 B-20 D 45 c----21 I c 46 A

22 -T A -t 47 - Br - - -23 _f ___c ---- ~ - - - - 48 . -- 1-- A- - 1--------j2 4 i\ - . 1 - 49 1-------t--- I- ____2s _ c ___[ so --


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NO1 a)

'J(b) .~ ~ ) (i)

(ii)

1 d)

I ! (e)

1 f)

L _

1

.MARKING SCHEME PAPER 2SECTION A

ANSWER-Amino acid

Hydrogen bondr-- Secondary structure/ 0-pleated sheet Many hydrogen bonds are formed between C=O

and NH- group from the peptide bond regions.These maintain the stable structure of 0-pleatedstructure

Polypeptide chain is folded to form ~ - p l e a t e d sheetHydrogen bonds break;the secondary structure II ~ - p l e a t e d sheet will unfold IIbecome denaturedFibrous protein :Keratin I collagen I myosin I silk IGlobular protein : any named enzyme e.g amylase I anynamed protein hormone I antibodies

Polypeptide Polysaccharide Is linked by peptide I Has glycosidicbonds bonds Contains sequence Has identical/same

of difference monomersmonomers/aminoI acids Linear/straight Some havechain branches

SUBTOTAL TOTAL1 11 11 I

1

1 2ll 1

(Any 1)11

( any 1) 2

j2

1

1(any 2)

total 10- -


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2

NO ANSWER SUBTOTAL TOTAL2 (a)

Both X and Y axes with correct labels and unit 1/0 Both curves with labels correct(b)rul 110 %of Hb saturation for PC0 2 (40mmHg)- 60%, 75% % ofHb saturation for PC02 (80mmHg)- 95%, 98%

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(i i)1-- -+--(c) At higher partial pressure of C02, the affinity of Hbfor 0 2 is reduced

(d) Hb is comprised of 4 protein subunits I 4 polypeptidechains Has 2 a chains and 2 pchains Max2 Each globular subunit contains a haem molecule At the centre of each haem molecule is a ferrous ion

' - - - - - - -


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(e) RBC has no nucleus -more space for more lhaemoglobin thus more 02 can be transported Round, disc-like shape, flexible/elastic- allow cells Ito be squeezed through narrow capillaries I Thin plasma membrane- give a short diffusiondistance into and out of cells Biconcave- increases the surface area to volumeratio/ providing larger surface area for diffusion of l Max 3gases I gaseous exchange

Total 100 (a) Allometric growth l

Different parts of the body grows at different ratescompared to the overall growth rate of the organisms l 2(b) P-Thymus/ Lymphoid tissues I

Q-Brain/head l R-Absolute growth rate of human S-Reproductive organs ll 4

(c) P-Lymphoid tissues grow rapidly in early childhood lcompared to adolescent. This is because the risk of infection is high in early llife when immunity has not yet been acquired l S-The reproductive organ grow slowly

In early life but rapidly at puberty l To ensure that the reproductive system starts todevelop after other parts of the body have completed Itheir developmentMax 4

1----I

Total 10L -


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5

ANSWER SCHEME PAPER 2 BIOLOGY TRIAL STPM 2011Section B

NO- 5(a)

ANSWER

}GDrawing and structures correct5 labels(all):1. Intrinsic(A)(D)/lntegral(A)(D)//TransmemPore protein( A)/Extrinsic protein (G)

brane(A)(D)/2. Phospholipid bilayer (B)3. Cholesterol (E)4. Glycoprotein (C)5. Glycolipid (F)

5(b) Structure and function: the biological cell membrane acts as barrier and are

selectively permeablef phospholipidsthe membrane consists of a fluid bilayer o

and various protein molecules act as ion c hannels, CatTierprotein or pumps embedded in it

the phospholipids bilayer has a hydrophobiand a hydrophilic head

the phospholipids bilayer is permeableuncharged molecules like oxygen andsteroid based hormone, fatty acids and

c fatty acids tailto very small

carbon dioxide,alcohol (simple

SUB-TOTAL

Diagram: 1

Label:210

11

1

l

-iffusion)- ~ - - - - + - = - - - - - - ' c c _ : _ . : _ : c c L . _ _ . - - ; : - - - ; - - - - - - ; - - - - - - ; - - - - c : - - - - - - Transportation of substances into the cell: simple diffusion of water molecules across the semi Ipermeable cell membrane is called osmosls.

some integral mt;mbrane protein fom1 hydrophilic ioncham1els enable diffusion of various charged ions e.g.K+,Na+, Ca+, and HC03- down their concentration gradient some of this ion protein channels can open or close and are

I TOTAL

I

I

3 Max

4

called gated channels e.g. voltage-gated channels and11

ligand-gated channels large sized hydrophilic molecules such as glucose are Il twnsportcd across the cell membrane th;ough facilitated idr>IusJOn usmg a canier pwtem I,_____ "_ir1__i_:lC!lttatscl_ c ] ~ f f u s r o n , the_QJ_11dmg_ __o_L_s_t.llStdt1C_es_t_o__tl1e - ~ _ } _ _ - ~ ' - - - - ~

I


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NO ANSWER SUB- TOTALTOTALspecific protein carrier causes the change in its shape andthe substance is released into the cell

I l l active transport, the shape of protein carrier changes 1using energy (ATP) to transport substances across the cellmembrane

in endocytosis the substances are transported into the cell 1through the invagination of the cell membrane pinocytosis occurs when the cell membrane invaginates to 1actively transport a small amount of fluid into the cell all these structures and its related process enable the cellmembrane to function as semi-permeable membrane as well 1

as enable the cell membrane to regulate the movementof substances in and out of the cell (Any 8) Max 8

f-- TOTAL 156(a) Phloem tissue consists mainly of sieve tubes and companion lcells

Sieve elements are arranged end to end to form a long 1cylindrical sieve tubes The end walls of sieve tubes are perforated fanning a sieve 1plates with sieve pores Mature sreve tubes are Living cells with no nucleus, 1ribosomes or Golgi apparatus Companion cells connected to the sieve elements throughplasmodesmata contains a large nucleus, dense cytoplasm 1 Max4and numerous of mitochondria

(b) Translocation IS the movement of orgamc solutes I 1sucrose/an1ino acids/soluble Qroducts ofQhotosynthesis From the leaves/source through the sieve tubes to be carried 1 2to other garts of the Qlant/sink/root.

(c) The Mass flow hypothesis state that : The hydrostatic pressure gradient formed between the leaf 1cells (source) and root cells (sink) drives the passrve mass flow of water and dissolve solutes 1

downwards In leaves, orgamc substances /sucrose synthesized I l l the Imesophyll cells are actively transQorted into sieve tube Low water QOtential is created in sieve tubes, 1 Thus water enters the sieve tubes tLuough osmosis from the

;:cylem II The entry of water generates a high hydrostatic Qressure inthe sieve tubes 1

In the roots/sink, s u ~ a r s / s u c r o s e are activelv transQorted intothe tissue for cellular respiration or converted to starch for Istorage

As sugars are ren1oved, the water [JOtential of sieve tubes inroo!,;_b;_ increased, causing the water molecules to diffuse out 1

L-___ _jhrough osmosis into x y l e r ~ 1 roots_ _ _ _ _ _ _ _


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NO ANSWER SUB- TOTALTOTAL Low hvdrostatic pressure is created in the sieve tubes of the I 9

rootsTOTAL 157(a) Antibody is globular protein that reacts with specific antigen I" it is made up of 2 heavy chains and 2 light chains I

the structure are held together by disulphide bonds I" each chain has constant and variable parts I the variable part is the binding site of the antibody onto a I 5sgecific antigen

(b) "Humoral I antibody-mediated immune response involves B Ilymphocyte cell pathogens bearing foreign antigens invade the body 1 macrophages 111 the body engulf I phagoc ytocizes thesepathogens I digest the antigen into fragments by hydrolytic 1

enzymesMHC class II molecules bind to the macrophages to the Iantigen fragment to fonn MHC complex this foreign antigen , MHC complex is then displayed on the l

cell surface this macrophage is called antigen-presenting cell (APC) I helper T cell binds to APC and secretes IL-2 I The activated B cell then divides by mitosis and a clone of B Icell is produced B cells differentiate, becoming plasma cells and memory B Icells The plasma cells secrete antibodies I

I10

1---- TOTAL ISr-- 8(a)(i) 1ardy-Weinberg's Law

The frequency of (dominant and recessive) alleles ll1 apopulation will rem am constant from one generation to 1 1generation/ allele and genotype frequencies do not changefrom generation to generation 111 a population at geneticequilibrium

provided these four conditions are met:1. the population is large] I . mating is randomIll . no mutation occursIV. no migration occurs 2/0 2

(all four conditions must be correct)(ii) Sickle cell anaemia is a result of point/gene mutation/base substitution I

Glutamine is replaced by Valine. IIThis causes the abnormal haemoglobin to be pulled into a III sickk shape I_ _ _ j _ _ . _ c : : a u s i n g J E ~ S ~ _ ( ) X j i g C n to be carried to tbe tisstJe 1 Max 3 '' -- _______j


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NO ANSWER SUB- TOTALTOTAL-(b)

p+q= l 1r' + 2pq + q' = 1requency of allele h = q, frequency of allele H = p,

q' = 0.085% = 0.00085q = v.00085 1q = 0.029*p = I - qp = I - 0.029p = 0.971 * 1

%genotype HH = 0.971 2 X 100= 94.28% 1% genotype Hh = 2 X 0.971 X 0.029 X 100= 5.63% 1 Max4

(c )(i) q = 4% = 0.04q = v .04q = 0.2 Ip = I - qp = I - 0.2 Ip = 0.8

% genotype HH = 0.8 2 X 100 I= 64% I% genotype Hh = 2 X 0.8 X 0.2 X 100 I= 32% Max 3-, ..(c)(u) Normal blood cell sickle cell anemia blood cell(HH, Hh) (hh)64% + 32% 4% I96% 4%

24 I I 2- -TOTAL 1 5 - -

9(a) AmniocentesisI indirect screening for genetic defects in a foetus. I

a long, sterilized needle is pierced through the abdominal and 1uterus walls into the amniotic cavity.

a small sample of amniotic fluid together with cells sloughed 1off from the foetus' body are extracted.

the foetal cells are cultured in laboratory. 1 I II biochemical analysis of DNA and products of defective genes 1 I I(such as) u-foctoprotcin (AFP) for the spina bifida defect 'I~


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NO

9

ANSWERand karyotypic study are carried out.

this test is especially important for mothers above the age of35 if the foetus is handicapped, measures such as gene therapy,genetic counseling or abortion can be carried out

SUB-TOTAL11

(b) DNA fingerprinting. DNA is isolated from samples of blood, sperm or skin and is amplified using the polymerase chain reaction (PCR)teclmique. restriction enzyme is used to cut the DNA into fragments that

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are different in length and base sequences (the fragments are 1placed in agarose gel). the fragments are then separated according to s1ze and 1

charged by using the technique of gel electrophoresis. DNA fragments are heated to split double-stranded DNA into 1single strands (and then denatured tluough chemicaltreatment.) then transferred to a nylon membrane (through the process of ISouthem blotting). radioactive probes are added to bind to complementary base 1sequences in the DNA and are placed on an X-ray film.

radioactive probes in DNA fragments produce dark bands on Ithe film/autoradiography

TOTAL

Max 6

_____ - - c , - - c ; - - - - - - ; . : ~ - - - - - - - ; - - - : - . - - - - - - - - - - - - - - - + - ' " ( a = n : y _ y _ 7 : ) - - + _ _ : : M . : . : a : : - x : . . . : 7 ~ Use of fingerprinting: DNA fingerprint can be used in forensic science for testingspecimens and identification of individuals in criminal casesI accidents, immigration cases.

determination of kinship I patemity. identification of defective gene.

1

II(any 2) Max 2

--lO(a) Biogeochemical cycle means: Natural cycle of essential chemical elements in (various 1forms) by the geological and biological processes chemical elements flow from abiotic reserve to the biotic 1components and back to the abiotic pool II Involves

interactions between living things and non-living things The cycle prevent depletion of the resource. 3


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NO ANSWER SUB- TOTALTOTAL

(b) erosion\!'Inorganic inorganiC

mining, industrial phosphate f-+I>' phosphates inDissolved production of fertilisers in rocks r fr shwater, teansactive uptake by aquaticinorganic decomposition by organ1smsphosphate detmposecs v J land tons in the soil uplih V

death, decompositiondeath bones, teeth, ,).ctive ion upt ke shells. excret orywastes Sedimentation Vc> c u e " i

Organic eaten by Organic Inorganicphosphates animals V phosphates phosphates on

ocean floorsin plants in animals

~ -D iagrarn conect 2210 Max4All 6 ticked (,J) labels must be conect

c------- L Sedimentation of phosphates on ocean floor from the rocks. I2. After millions of years, geological land uplift raised the 1

rocks containing phosphorns above sea leveL0 Throngh erosion, phosphates returned to soil, rivers, lakes I~ and oceans from the rocks.4. Mining of rocks for the manufacture of fertilizers supply I Inorganic phosphates to the soiL5. Inorganic phosphate ions are absorbed by plants, II 6. then assimilated to synthesise important compounds/amino II acids.

I 7. Transfen-ed to herbivores when eaten and then to other 1trophic levels in the food chain through assimilation.I 8. When organisms die, remains of bones , teeth , shells and 1excretory wastes area acted on by bacteria to releasec-_ --

inorganic phosphates into soil through decomposition. 8OTAL 15~ -

stpm_bio_p1_p2_skema

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