Biology Test - 7

An enzyme brings about reduction in activation energy. Enzymes are proteins which accelerate the rate of the reaction. The substrate and product have different energy state. The energy gap between the substrate and the product is known as activation energy which is the minimum energy required to initiate a reaction. The binding energy is the source of energy used by enzyme to lower the activation energy of reaction. Activation energy is the minimum energy required from outside to overcome the energy barrier of reactants. The enzymes lower the activation energy and lead to the faster conversion of substrate to the product.

The chemical composition of chromatin is DNA, histones, non-histones and RNA.

Alkaline pH of gut solubilizes the protein crystals and activates protoxin.

Bacillus thuringiensis forms protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein. These protein exist as inactive protoxins but once an insect ingest the inactive toxin, it is converted into an active form of toxin due to alkaline pH of the gut which solubilize the crystals. The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually cause death of insect.

In DNA, the sugar-phosphate backbone forms the outer structure of the double helix, with nitrogenous bases positioned internally. Base pairing via hydrogen bonds (A with T and C with G) results in the ladder-like structure of the helix, where bases stack internally and the sugar-phosphate backbone comprises the sides. This arrangement gives DNA its characteristic double helical shape.

The root nodules formation in legumes involve following events:

(i) Rhizobia multiply and colonize the surroundings of roots and get attached to epidermal and root hair cells. 

(ii) The root-hairs curl and the bacteria invade the root-hair. 

(iii) An infection thread is produced carrying the bacteria into the cortex of the root, where they initiate the nodule formation in the cortex of the root. Then the bacteria are released from the thread into the cells which leads to the differentiation of specialized nitrogen fixing cells. 

(iv) The nodule thus formed, establishes a direct vascular connection with the host for exchange of nutrients.

Thus, the correct answer is '(i), (iv), (iii), (ii).'

Darwinism explains all except variations are inherited from parents to offspring through genes.

One of the major drawbacks of Darwin's theory is the absence of knowledge on inheritance. The genetic basis of evolution, cause of variations was not included in Darwin's 'Origin of Species'. It was only after the discovery of genes and traits by Mendel, genetics could be associated with evolution.

The oesophagus from inside to outside has four layers: innermost mucosa, sub-mucosa, muscularis propria, and outermost adventitia. It does not have serosa or serous lining as its outermost layer because serosa is lined by a visceral peritoneum while the outermost layer of oesophagus is not lined by any visceral peritonium.

The enormous diversity of protein molecules is due mainly to the diversity of amino acid sequences within the protein molecule.Proteins are building blocks of the body. The proteins are made up of amino acids. The amino acids are linked together by peptide bonds to form a protein. The amino acids consist of amine group made up of nitrogen and hydrogen and the carboxyl group at the end and a side chain of R group which is specific to a particular amino acid. This specific group brings a variability to the proteins. If R group is H it is glycine while if it is\(\mathrm{CH}_{2}\),it is alanine. The sequence of amino acids determines the protein.

Bioaugmentation is the addition of bacterial cultures to enhance the rate of degradation of a contaminant. It is used in municipal wastewater treatment to restart activated sludge bioreactors.

Bioaugmentation is the practice of adding cultured microorganisms into the subsurface for the purpose of biodegrading specific soil and groundwater contaminants.

Bramble Cay melomysis the first mammal species to be wiped out by human-induced climate change.

• Bramble Cay melomysis a recently extinct rodent genus of the Muridae family and the Murinae subfamily.
• It was an extinct species of the isolated Bramble Cay, a vegetated coral caysituated at the northern tip of the Great Barrier Reef in Australia.
• Described as having been last seen in 2009 and confirmed extinct by researchers from the Queensland Government and the University of Queensland in 2016, the International Union for the Conservation of Nature (IUCN) officially declared extinct in May 2015, and the Australian Government in February 2019.
• Its extinction was identified as the first mammal species to be extinct due to anthropogenic climate change.