Download 5. 4oC

Answer Kev
F.Y. Life Sciences paper
I
Q.P. code 754909
Exam held on 2lst November 2016
Q.1
A Fill in the blanks
1. Lysine orArginine
2. Amino or N and Carboxyl or C
3. Starch or Glycogen
4. Hemoglobin orname of any enzyme
5. 4oC
B Match the column
l. a-v
2.b-iv
J.
C-r
4.
d-iii
5. e-vi
c.
1' Euchromatin: Chromatin that does not stain darkly in an
interphase nucleus. It represents
the major genes and is involved in transcription.
2' Sarcomere: A structural unit of a myofibril in striated muscle, consisting
of a dark band
and light bands. It is the segment between two neighbouring
Z-lines
many
me
4' Histone: A group of f1ve. small basic proteins,occurring in the nucleus
of eukaryotic cells,
that organize DNA strands into nucleosomes by forming riolecular
complexes u.ouna which
the DNA winds.
5' Intermediate Filament: Any of a group ofprotein filaments that are a
component of the
cytoskeleton in animal cells, are composed of a variety of proteins
such as lamins and
keratins, and provide structural support for the cytoplasm and nucleus.
Intermediate filaments
are intermediate in diameter betwoen microfilaments and microtubules.
D.
1. True
2. False
3. False
4. False
5. True
Q.2
A.
l.
Physical Properties of w
o Each physical property of water:
. With significance : *1
2.
Classification of proteins
o Classification(Structu
{ Ptimary,
Structural and
{ Simple, Conju
o With Examples: 2
o Functions ( At least 4)
r'
I
Mark
/ Function / Composition) : 2 Marks
, Tertiary and Quaternary
ional
and Derived
B.
l.
Diffusion and Osmosis
o Compare (2 points): 2
o Contrast (2 Points): 2
o Example: I Mark
arks
2. Buffers
o
o
o
Definition: lMark
Example(s): I Mark
Significance: 3 Marks
3. Monosaccharide
o
o
o
Definition: lMark
Structure / Example(s): I Mark
Functions: 3 Marks
4. Polysaccharide that cannot
. Cellulose: I Mark
o Structure: 2 Marks
o Function / Significance
digested by human
eason (Why
it cannot be digested): 2 Marks
Q.3 A)
f . With a neat and labelled iagram, explain ultra structure
of bacterial cell
Ans: Diagram: 5 marks
Description: 5 mks
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flag*ilurn
srni6
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2. Factors influencing micro$ial growth- Any five of the following and their
effects- 2 mks each
Solutes and Water Acidity, pH
Temperature, Oxygen Requirer{rents
Pressure,Radiation
Q.3B)
5mks
.Qd!dl*lUcnr
HmmIhtI{
nFffiFftrbghr,
trffidqqrgr!frrgE'
2.
Endosymbiont theory- both
mi
t, a) from prokaryotic
ast and b) prokaryotic
photosynthetic unicellular orgganism
unicellular non photosynthetic bacterial
3. Isolation of microorganisms
i) Broth Cultureii)Serial dilution
-
ndria- 2.5 mks each.
any two techniques of the following- 2.5 mks each
iii)Streak plating
iv)Spread Plate
v)Pour plate technique
4.
Gl and S phase in Cell cycle with their
significance
The Cell
withyrmark significance
with%mark significance
(DNA replication)- 2 mks description with%mark significance
2 mks description
Gr Phase (Growth)- 2 mks description
s Phase
Q.4. A) Attempt any one of the following: 10 marks
1. Explain
in detail Euchromatin and Heterochromatin.
Answer:
(2 marks definitions * 8 marks discussion of properties)
chromatin is found in two varieties: Euchromatin and Heterochromatin.
The concept of heterochromatin was described by Emil Heitz in 192g.
The two forms were distinguished cytologically by how intensely they stained the
euchromatin is less intense in an interphase nucleus, while heterochromatin stains intensely,
indicating tighter packing.
Heterochromatin
Condensed in Interphase
Heterochromatin DNA is
Latereplicating
Euchromatin
NOT condensed in Interphase
Euchromatin DNA is Early replicating
t
Heterochromatin DNA is methvlated
I
Histones from heterochromatin are
DNA is NOT methvlated
Histones from euchromatin are NOT
I
I
I
t
!
methylated
methylated
Heterochromatin is transcdption.allv
Euchromatin is transcriptionally
INACTIVE
ACTIVE
Heterochromatin DOES NOT
participate in genetic recor4bination
Heterochromatin has a gre arious
Euchromatinparticipates in genetic
recombination
EuchromatinDoEs NOT have a
gregarious instinct
instinct
2.
what are microfilaments? Exprain their role in muscle contraction.
Answer:
@escription of sarcomere 5 marks
* mechanism
of contractlon 5 marks)
A
skeletal muscle comprises a bundle of muscle cells, or myofibers.Each
muscle cell is
tin and
s that extend the
end to
s, the functional
ine and contains
several dark bands
(Z-line From the German word.,,zwischenscheibe,,
dillt:fres.
"td the I+bands) On either
meaning "the band between
side of the Z lines are the lightly stained I
bands, composed of actin filamen[s. These thin filaments extend from both
sides of the Zline
to interdigitate with
myosin
thick
filaments
that
make
up
the A band. The
lhe lqk-stairred
region containing both thick and thin filaments (.
only myosin thick filaments (the H zone). A s
composed only of actin filaments located at
staining A band or A zone is loctted between
myosin filaments.
Q-bgd: Ani$otropic). A lightly staining H zone made up of only myosin
filaments is located in the center 0f the A band. (H-Zone = F.oto the German
word,,Heller"
meaning "Bright"). In the centre of the HZone is the M-line (MJine from the German
word
'Mittel" meaning "Middle')
:
ntrosln
-
MI I r-r
actln
MIM
I r--1
|
Bands and lines in lhe contrastlle
apparalue of skeletal muscle
Sliding Filament Theory of musclo contraction:
' An action potential inducpd at the neuromuscular junction is propagated along the
sarcolemma of the skeletal muscle.
The
sarcolemma contains regions known as T-fubules. As the action potential is
'
propagated along the T- tubule, it membrane gets depolarized.
' This leads to increase in permeability of the sarcoplasmic reticulum to calcium ions"
' Calcium ions then diffuse from the sarcoplasmic reticulum into the sarcoplasm.
I
I
In skeletal muscles,
T.pO..ygrin proteins are attached to the actin filament blocking
the sites where myosin cFn bind to actin filament. And
troponin remains attached to
tropomyosin.
When calcium ions bind {o troponin, this causes troponin to change
conformation and
move tropomyosin.
When tropomyosin
the myosin binding sites on actin are uncovered, allowing
}o_ve$,
myosin heads to bind tp actin. Thus yosin forms cross-bridges between
actin
filaments.
The myosin head which i$ bound to actin flexes, pulling the actin filament
along with
it. This causes the actin fifament to slide by the myosin hhrn.nt.
Then the myosin head feleases from the actin filament and unflexes. This
step
requires energy which is supplied by hydrolysis of ATP. This frees
the myosin head
to bind to a different actin molecule, farther up the actin filament.
The entire process is repe{ted many times.
Thus, the myosin "walksi'along the actin filament, moving the actin
filament more
and more each time.
Thus the muscle contractsr
Q.4. B) Attempt any two of the following: 5 marks each
1.
using a neat and labeled diagpam explain the structure of
a Nucleus
Nuclear envelope and pores: The 4uclear envelope, otherwise known as nuclear membrane,
consists of two cellular membranes, an inner and an outer membrane, ananged parallel to one
another and separated by 10 to 50 nanomehes (nm). The nuclear envelope completely
encloses the nucleus and separates the cell's genetic material from the surrounding cytoplasm,
serving as a barrier to prevent maoromolecules from diffusing freely between the
nucleoplasm and the cytoplasm. The outer nuclear membrane is continuous with the
membrane of the rough endoplasnlic reticulum (RER), and is similarly studded with
ribosomes.Nuclear pores, which ptovide aqueous channels through the envelope, are
composed of multiple proteins, collectively referred to as nucleoporins.
Nuclear Lamina: The nuclear lamina is composed mostly of lamin proteins. Like all proteins,
lamins are synthesized in the cytoplasm and later transported to the nucleus interior, where
they are assembled before being incorporated into the existing network of nuclear lamina.
Chromosomes: The cell nucleus pontains the majority
of the cell,s genetic material in the
form of multiple linear DNA molecules organized into
structures called chromosomes.
Nucleolus: The nucleolus is a discrete densely stained structure found
in the nucleus. It is not
surrounded by a membrane, and is sometimes called a suborganelle.
It forms around tandem
repeats of rDNA, DNA coding for ribosomal RNA
GRNA).These regions are called
nucleolar organizer regions (NOR). The main roles of the nucleolus
are to synthesize
rRNA
and assemble ribosomes"
2.
write a note on: structure of Gram negative bacterial cell wall
Answer:
@iagram 2 marks + Description 3 marks)
The walls of Gram negative bactqria have a low peptigoglycan content
of approximately 5 to
15 Yo
ered
of
wall
bacteria
cell
ell.
of
ow
constituieJtire
bacteria is sim
f
cross-linking
many of the peptide chains are not crossJinked
and
Superimposed on the thin layer of peptidoglycan layer of Gram negative bacteria
is an outer
wall layer the major component of which is Lipopolysaccharide (Lps).
1. Lipids:
The lipids which are apart of Gram negative cell wall are contained within
the Lipid A region of the outer cell wall layer of Gram negative bacteria. The
Lipid
region consists of phosphorylated glucoseamine which is isterified with long chain
A
fatty acids like lauric acid, myristic acid and palmitic acid in a ratio of 1:1:l]thus this
region of the molecule is hydrophobic and is arranged such that its orientation is
towards the inner cell wall layer so as to shield it from water.
2.
Polvsaccharide: the polysaccharide component of the outer membrane of the cell
wall of Gram negative bacteria consists of two distinct regions:
(a) R-core region - The R.core region is attached to one of the glucoseamine residues
of the Lpid A region. The R-core region is made up of two cores The inner core in
tum consists of two regions, one made up of ketodeoxyoctonate (KDO) and the other
of diheptose. The outer core is made up of oligosaccharides i.e. short cirains of sugars.
(b) O-side chain - The R-oore possess a hydrophobic O-side chain which is mainly
composed of sugars. It is much longer than the R-core region and has many repeaiing
trisaccharide, tefrasaccharide and pentasaccharide units.
3.
Write
a note on: Larnpbrush Chromosomes
Answer:
o
t
o
o
The existence of lampbrush chromosomes supports the concept that chromatin
is
organized in a series ofloops.
Lampbrush chromosomes occur in a limited phase of meiosis during oogenesis
in
amphibian oocytes.
The lampbrush chromosome is a bivalent (2 pairs of sister chromatids held together
by
chiasmata).
The chromosome strands (20 nm diameter fibers consisting of two double strands
of
DNA) are dotted with about 5000 chromomeres (dark staining irregular structures also
o
o
o
seen in interphase chromosomes).
Twin loops (length 400-800 nm) emerge from chromomeres. An identical pattem of
twinned loops occurs on both pairs of sister chromatids.
Loops show a gradual increase of electron density from the chromomere around the loop
and back to the chromomere.
The average length of loops corresponds to the average length of RNA transcripts in these
oocytes, but is much longer than the average length of RNA transcribed in somatic cells.
Functions of Lampbrush chromosomes:
(a) Synthesis of RNA:
Functions of lampbrush chromosomes involve synthesis of RNA and protein by their loops.
RNA is synthesized only at the thin insertion and then carried aroundihe loops to the thick
insertion. There it may be either destroyed or released into nucieus.
(b) Formation of yolk material:
10
4.
Write
a note on: Structure of flagellum
Answer:
(Structure 3 marks * Diagram 2 marks))
' Flagella are attached to strucfures known as basal bodies,which in turn are anchored to
the plasma membrane. From the basal bodies the microtubule ,,backbone,,
extends,
pushing the plasma membrane out with it.
' Within the flagella, nine outer doublet microfubules surround a central pair of singlet
microtubules (Figure below).
"r This characteristic"g + 2" arrangement of microfubules is viewed in cross section
Each doublet microtubule consists of A and B tubules: the
A tubule is a complete
microtubule with 13 protofilaments, while the B tubule contains
protofilaments.
l0
' 'Ihe flagellar structures are held together by three sets of protein cross-links:
(a) The central pair of singlet microtubuleJ are connected by bridges.
O) A set of linkers, composed of the protein nexi4 joins adjacent outer doublet
microtubules.
(c) Radial spokes, which radiate from the central singlets to
each
doublets, form the third linkage system.
A tubule of the outer
InnErdy*ein
N(xin
Spulk*hrnd
fudlal:9poke
nrmttmb(ft
t1
Q.s
I Primary
o
o
o
structure of protein
Definition: lMark
Structure: 2 Marks
Functions / Specific Features/ Examples: 2 Marks
2. Water as Universal Solvent
" Definition: lMark
o
o
3.
Reasons: 2 Marks
Importance:2 Marks
Any two of the following media components
Solid MediaSemi solidLiquid/broth media
- 2.5 marks each
OR
Synthetic
Non synthetic media
Or
Basic, Enriched, Selective, Differential media
4' Animal cell, with cell components ( at least five- Cell wall, nucleus, mitochondria,
lysosomes, centrosomes, golgi bodies, rough ER etc) diagrammatic with p"op..
labels -5
mks, if no labels only 3 marks
plnocytotlc
voslde
lysosome
Golgl
wslder
rough ER
smooth ER
(no rlbosomes)
centrlolar (2)
Each compmed
olll
nlcrotubrla trlplrtr.
mlcrotubilhs
coll(plasma
cytoplasm
mombranG
dbosome
@e.*.*m*rtnriiOci
t2
5.
Draw a neat and labeled diagram of Nucleus
Euchonudn
Nuclsarpors
Parinuclearspact
llelarochromatln
P6dnucleghr
6hrsindtln
Intranucleahr
drromaffn
onvelopo
hn$rmembeng
Oulerrnombrane
6. Write a note on plant cell wall:
Answer:
@escription 3 marks * Diagram 2 marks)
The plant cell wall is multi-layered and consists of up to three sections. From the outermost
layer of the cell wall, these layers are identified as the middle lamella, primary cell
wall, and
secondary cell wall. While all plant cells have a middle lamella and prirnary cell wall, not all
have a secondary cell wall.
Middle lamella - outer cell wall layer that contains polysaccharides called pectins.
Pectins aid in cell adhesion by helping the cell walls of adjacent cells to binh to one
.
.
.
another.
Primary cell wall - layer formed between the middle lamella and plasma membrane
in growing plant cells. It is primarily composed of cellulose microirbrils contained
within a gel-like matrix of hemicellulose fibers and pectin polysaccharides. The
primary cell wall provides the strength and flexibility needed io allow for cell growth.
Secondary cell wall - layer formed between the primary cell wall andplasma
membrane in some plant cells. Once the primary cell wall has stopped dividing and
gtowing, it may thicken to form a secondary cell wall. This rigid layer strenghens and
supports the cell. In addition to cellulose and hemicellulose, some secondary cell
walls contain lignin. Lignin strengthens the cell wall and aids in water conductivitv in
plant vascular tissue cells.
Plant Cell Wall Function
A major role of the cell wall is to form
a framework for the cell to prevent over expansion.
Cellulose fibers, structural proteins, and other polysaccharides he$ to maintain the shape and
form of the cell. Additional functions of the cell wall include:
Support - the cell wall provides mechanical strength and support. It also controls the
.
.
.
direction of cell growth.
Withstand turgor pressure - turgor pressure is the force exerted against the cell wall
as the contents of the cell push the plasma membrane against the ceil wall. This
pressure helps a plant to remain rigid and erect, but can also cause a cell to rupture.
Regulate growth - sends signals for the cell to enter the cell cycle in order to divide
and grow.
13
Regulate diffusion - the cell wall is porous allowing some substances, including
proteins, to pass into the cell while keeping other substances out.
Communication - cells communicate with one another via plasmodesmata (pores or
channels between plant cell walls that allow molecules and iommunication signals to
pass between individual plant cells).
Protection - provides a barrier to protect against plant viruses and other pathogens. It
also helps to prevent water loss.
storage - stores carbohydrates for use in plant growth, especially in seeds.
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