Question

1.Which of the following is not an oligosaccharide?

1. Trehalose
2. Nodulation factor
3. Streptomycin
4. Amylose
5. Maltose

2.Which strand of DNA is replicated exclusively in a discontinuous fashion?

1. forward strand
2. reverse strand
3. leading strand
4. lagging strand
5. the strand that is read in a 5’ to 3’ direction

3.Which of the following statements about DNA synthesis in eukaryotes is correct?

1. Synthesis of linear chromosomes leads to telomere shortening in somatic cells
2. Unwinding of DNA by helicases is facilitated by positive supercoils
3. DNA synthesis is initiated at a single origin of replication
4. The daughter strands are synthesised in a 3’-5’ direction
5. Activation of an origin of replication generates a single replication fork

4.What element in prokaryotic mRNAs directs the ribosome to the initiation codon?

1. TATA box
2. Promoter
3. Pribnow box
4. Lac Operator
5. Shine-Dalgarno sequence

5.Which one of these organs is not a sink tissue

A. very young leaf

B. mature leaf

C. root

D. tuber

E. fruit

primary metabolites in plant cells are

6.A. chemicals that help plants cope with their environment

B. largely conserved between species

C. proteins involvedin defense mechanisms

D. inorganic molecules

E. organic molecules involved in pollination of higher plants

7.Cluster roots in proteaceae are

A. allowing the plants to anchor in soil

B. allowing the plants to mine soil for water

C. present all year long

D.allowing plants efficiently to mine the soil for phosphorus

E.all of the above

8.Which of the following statements is false?

1. Phospholipids can easily move within the plane of biological membranes
2. Phospholipids can rotate in the lipid bilayer
3. Phospholipids can easily move from one side of the lipid bilayer to the other
4. The fatty acyl side chains in the interior of the phospholipid bilayer are in constant motion at room temperature
5. None of the above

9.A base found exclusively in DNA is _____ while _____ is found only in RNA.

1. adenine; cytosine
2. guanine; thymine
3. uracil; adenine
4. cytosine; guanine
5. thymine; uracil

10.Which chemical groups from a pair of amino acids must react to form a peptide bond?

A. the two R-groups or sidechains
B. the two carboxyls- I think
C. the two alpha carbons
D. the amino group of one and the alpha carbon carboxyl group of the other

E. the amino group of one and the carbon of the other

11.Which one of the following catecholamines and neurotransmitters is notmade from Tyrosine in human cells?

A. Serotonin
B. L-DOPA
C. Adrenaline (or epinephrine)

D. Dopamine
E. Norepinephrine

Answer 1

Question No.	Correct option	Explanation
1	D. Amylose	An oligosaccharide is a relatively small chain of individual monosaccharide molecules made up of 2-9 units. All the others are examples of oligosaccharides. But amylose is a linear chain of numerous glucose units and hence it is a polysaccharide.
2	D. Lagging strand	Since DNA molecules are antiparallel (meaning that one strand is 5' to 3' and the other is 3'-5'), when they are unwound during replication, the DNA polymerase faces a challenge as it can only synthesize a new strand in 5'-3' direction. So, the direction of replication for the two strands are the opposite. THE new DNA strand opposite to the strand with 3'-5' orientation is made continuously as the movement is toward the replication fork. The other strand synthesis occurs in a different fashion-in a discontinuous way. As the polymerase move toward the replication fork, a short stretch is replicated in this strand, then the strand is released and another stretch is captured and replicated as polymerase follows the helicase.
3	A. Synthesis of linear chromosomes leads to telomere shortening in somatic cells	At the very end of the linear chromosome, the sequence replication of the lagging strand is not complete. At the 5'-end of the original DNA molecule, a complementary RNA primer is attached during replication. But after RNAse action, the end becomes empty. The short empty sequence cannot be filled by DNA polymerase I as there are no 3' ends available. So, a strand with fewer sequences is formed each time somatic DNA is replicated. Germline chromosomes use an enzyme named telomerase to overcome this difficulty.
4	E.Shine-Dalgarno sequence	This sequence is present in the mRNA itself in prokaryotes upstream to the initiation codon. It serves the function of attaching itself to a ribosome that would be performing the translation process.
5	B. mature leaf	A sink is a tissue that exports carbon products such as sugar. Tubers, root, fruit, young leaves all import carbon products for their growth. On the other hand, a source is a tissue that is a net exporter of carbon. This means that it produces those carbon products (sucrose). Mature leaves produce more carbon than they need for themselves, making it a source of tissue.
6	B. largely conserved between species	A primary metabolite is a metabolite that is part of its normal growth and development and that serves important functions. Amino acids, carbohydrate molecules, etc. These are highly conserved among species, meaning that the same primary metabolite can be found in distance of the species carrying out the same function.
7	E.all of the above	The clustered nature of the root in Proteaceae helps to integrate soil particles, maneuvering phosphate solubilization, and therefore can grow in harsh conditions for a longer period.
8	C. Phospholipids can easily move from one side of the lipid bilayer to the other	Phospholipids cannot move easily from one layer of the lipid membrane to another. It is a highly energetically expensive process, and ATP-dependent enzymes such as flippases are used for such operation.
9	E. thymine; uracil	Adenine, guanine, and cytosine can be found in both DNA and RNA. However, thymine is only found in DNA whereas its analogous base uracil is exclusive to RNA.
10	A. Serotonin	Serotonin is biosynthesized from Tryptophan. All the others are biosynthesized from Tyrosine.