Section-A 1. These are archaebacteria. Since they live and grow in high saline or salty environments they a re called ha lophiles. 1 2. The stomatal apertur e, gua rd cells and t he surr ounding subsidiary cells together a re called stomat al apparatus. 1 3. T he age of a tree ca n be determined by counting a nn ua l grow t h rings in th e lower part of the stem. 1 4. Pota ssium is involved in ma ny phy siological processes like respira tion, photosynt hesis, stomata l movement a nd protein sy nthesis. 1 5. It prevents enzy ma tic hydrolysis of stored food and ena bles the seed to surviv e a long period of dormancy. 1 Section-B 6. Head Collar Ta il fibres (b) Sheath 2 OR Sporophyte Gametophyte Capsule Seta Leaves Main a xis Rhizoids 2 7. Ca lc iu m : (a ) For the form a tion of spindles durin g cell wall. (b) For t he fo ion of middle l mella. S AMPLE QUESTION PAPER–B AglaSem Schools
Transcript
8/13/2019 CBSE Sample Paper for Class 11 Biology Solutions - Set B
14. ATP is syn th esized wit h t h e help of complex V (ATP syn t ha se). Complex V consist s of F 0 – F 1
components. F0 is an int egra l membra ne protein complex tha t a ct as th e cha nn el thr ough w hich
the proteins pass across the membrane into the matrix. The passage of protons through the
cha nn el is coupled to th e ca ta lyt ic site of F 1 component a n d one molecule of ATP is syn th esized
for every 2H + passing through F 0. 3
15. It is a ty pe of cell division w here th e nu mber of chr omosomes is reduced to ha lf in the da ugh ter
cells.
Significance :
(i) It ensures th e ma intena nce of a const a nt chromosome number, cha ra cteristic of a species.
(ii) The crossing over results in va riat ions of genetic char a cters in the progeny; va ria tion is
necessa ry for sur vival of species a nd it is the ra w ma teria l for evolution. 1+2=3
16. Act in fi lament conta in t hree proteins na mely, actin (F-a ctin a nd G -a ctins), tr opomy osin a nd
tr oponin. E a ch actin filam ent consists of tw o F-a ctin w hich a re helica lly w oun d to each other.
Ea ch F-a ctin is a polymer of globula r a ctin. Tw o filam ents of tr opomyosin a lso run close to F-
a ctins th roughout t heir length . Troponin is a complex protein found a t r egular interva ls on the
tropomyosin. In the reac t ing s ta te , a subuni t o f t roponin masks the ac t in-binding site of
myosin. 3
17. I t is th e phenomenon in w hich a substa nce closely resembling the substra te in its molecular
str ucture competes wit h it for t he active sit e on t he enzyme. Eg – Malona te resembles succina tein its structure a nd inhibits t he a ction of succina te dehydr ogena se. C ompetitive inhibition is
used in th e contr ol of bacteria l pa th ogens. 3
(i) Essentia l elements a s components of biomolecules an d hence s tructura l element s of cells
(e.g., car bon, hy drogen, oxygen a nd nitrogen).
(ii) Essentia l element s th a t a re components of energy-relat ed chemica l compoun ds in pla nt s
(e.g., ma gnesium in chlorophy ll a nd phosphorous in ATP ).
(ii i) Essentia l elements th a t a ct ivate or inhibit enzymes, for exam ple Mg2+ is an activator for
both ribulose biphosphate carboxylase-oxygenase and phosphoenol pyruvate carboxylase,
bot h of w hich ar e crit ica l enzym es in photosyn th etic car bon fixat ion; Zn2+ is an act ivator of
a lcohol dehy drogena se a nd Mo of n itrogena se during n itrogen meta bolism.
(iv) Some essentia l elements can a lter the osmotic potentia l of a cell. P ota ssium plays a n importa nt
role in th e openin g an d closing of stoma ta . 5
26. (1) ECG is a gra phica l representa t ion of the electr ica l ac t iv ity of the hear t during a ca rdiac
cycle. A pat ient is connected t o the ma chine with th ree electr ica l lea ds (one to ea ch w rist a nd
to the left a nkle) th a t cont inuously monit or th e heart a ctivity. For a detailed evalua tion of
the h ear t’s function, mu ltiple lea ds a re a tt a ched to the chest region. Here, we w ill ta lk only
about a s t andard EC G .
(2) E a ch pea k in the EC G is identified w ith a lett er from P to T th a t corr esponds to a specific
electrica l ac t iv i ty o f the hear t . The P-wave represents the e lec tr ic a l exc i ta t ion (or
depolarisa tion) of the a tr ia, w hich leads t o th e cont ra ction of both the a tr ia. The QRS complex
represen ts th e depolar isation of the ventr icles, w hich initiat es the ventricular cont ra ction.(3) The con t ra ct ion s t ar ts short ly a f ter Q an d ma rks the beginning of the syst ole. Th e T-w a ve
represen ts t he retur n of the ventr icles from excited t o norma l sta te (repola risa t ion). The end
of the T-w a ve mar ks the end of systole.
(4) O bv iou sly, by coun ting t he nu mber of QRS complexes tha t occur in a given t ime period, one
ca n determine the hea rt beat ra te of an individua l .
(5) S in ce t h e EC G s obta ined from different individuals ha ve roughly t he same sha pe for a given
lead conf igura tion, an y deviat ion from this sha pe indica tes a possible abnorma lity or disease.
R
P Q ST
5
OR
(1) H ea r t is situa ted in the th oracic ca vity, in betw een t he tw o lungs, slightly tilted t o th e left. It
ha s the size of a clenched fist. It is protected by a double w a lled membra nous ba g, perica rdium,enclosing t he perica rdia l fluid.
(2) Our heart ha s four chambers , tw o rela t ively small upper cha mbers cal led at r ia a nd tw o
lar ger low er cha mbers ca lled ventr icles.
(3) A thin, muscular w a ll ca lled the inter-a tria l septum sepa ra tes the right a nd the left at ria,
w hereas a th ick-w a lled, the inter-ventricula r septum, separa tes th e left a nd th e right vent ricles.
(4) The at r ium a nd th e vent ricle of the sa me side ar e also separa ted by a thick f ibrous t issue
ca lled t he a tr io-ventricula r septum.
(5) Ea ch of these septa is provided w ith a n opening th rough which the tw o cha mbers of the same
side a re conn ected. The opening betw een t he right a trium a nd t he right ventricle is gua rdedby a va lve formed of th ree muscular fla ps or cusps, th e tricuspid va lve, wh ereas a bicuspid or
mitra l va lve gua rds th e opening betw een th e left a tr ium an d the left ventr icle.
(6) The openings of the r ight a nd th e lef t ventricles int o the pulmona ry ar tery a nd t he aorta
respectively a re provided w ith th e semilun a r va lves. The va lves in th e hear t a llow s t he flow
of blood only in one direction, i.e., from the at ria to the ventr icles a nd from the ventr icles to
the pulmona ry a rtery or a ort a . These valves prevent a ny ba ckwa rd flow .
(7) The entir e hear t is ma de of car diac mu scles. The w a lls of ventr icles ar e much t hicker tha n
tha t of the a tria . A specialized ca rdia c muscula tu re ca lled th e nodal tissue is a lso distributed
in th e hea rt. A patch of th is tissue is present in the right upper corn er of th e right a tr ium
called t he sino-a tr ia l node (SAN).
(8) Another ma ss of th is tissue is seen in t he low er left corner of th e right a tr ium close to the
a tr io-vent ricular sept um called th e a tr io-vent ricular node (AVN). A bun dle of noda l fibres,
a t rio-vent ricula r bun dle (AV bun dle) cont inu es from th e AVN w hich passes th rough t he at rio-
ventricula r septa to emerge on t he top of th e inter-ventricula r septum a nd immediat ely divides
into a right a nd left bundle.
(9) These bra nches give rise to minut e fibres t hroughout th e vent ricula r m uscula tur e of t herespective sides an d a re called purk inje fibres. These fibr es a long w ith right a nd left bund les
