General Science Questions (MCQs) for Competitive Examinations

Notes:
Keratin is a family of fibrous structural proteins involved in making up the outer layer of human skin. It is also the key structural component of hair and nails. Cells in the epidermis contain a structural matrix of keratin, which makes this outermost layer of the skin almost waterproof, and along with collagen and elastin, gives skin its strength. It also makes up fish scales and crustacean shells, bird feathers and beaks, animal horns and hooves.

Notes:
During hibernation in winter, toads or frogs spend the time tucked away deep in the soil, in the mud underwater or hidden amidst foliage or rotting plants. Outside of times of hibernation, they usually take in oxygen via the air, employing their lungs. However, during hibernation, they receive their necessary oxygen through their permeable skin. This is referred to as cutaneous gas exchange.

Notes:
Mitochondria is an organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur. It is for this reason that mitochondria are often referred to as the powerhouses of the cell mitochondria also play a key role in the ageing process as well as in the onset of degenerative disease.

Notes:
Milk is a poor source of ascorbic acid (Vitamin C). It contains about 1 mg ascorbate per 100 g. Even the little Vitamin C is usually destroyed when the milk is heat treated. Milk as a complete food contains most of the esential nutrients except are vitamin C and iron.

Notes:
Jaundice is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae (whites of the eyes), and other mucous membranes caused by hyperbilirubinemia. Concentration of bilirubin in blood plasma does not normally exceed 1 mg/dL (>17?mol/L). A concentration higher than 1.8 mg/ dL (>30?mol/L) leads to jaundice. Jaundice is often seen in liver disease such as hepatitis or liver cancer.

Notes:
The right pulmonary artery is longer and larger and runs horizontally outward in front of right main bronchus and behind the superior vena cava, to the base of the right lung where it divides in two branches. The left pulmonary artery is shorter and runs horizontally over the left upper division bronchus, to the base of the left hilum where it divides into two branches.

Notes:
Animals, such as mammals and birds, that maintain a constant body temperature regardless of the temperature of the surroundings are called warm blooded. These include birds and mammals. Whales are aquatic mammals hence, being mammal, they are warm blooded. The have a thick layer of fats called blubber underneath their skin to maintain temperature even in cold water of oceans.

Notes:
The three organelles that contain DNA are the nucleus, mitochondria and chloroplasts. Mitochondria are unlike most organelles (with an exception of plant chloroplasts) in that they have their own set of DNA and genes that encode proteins. They are specialized structures unique to the cells of animals, plants and fungi.

Notes:
The urinary bladder is a hollow muscular organ that collects and stores urine from the kidneys before disposal by urination. In humans, the bladder is a hollow muscular organ situated at the base of the pelvis. Urine enters the bladder via the ureters and exits via the urethra.

Notes:
The best-known and most common chromosome abnormality in humans is Down’s syndrome, (Trisomy of 21st pair of chromosome). Down’s syndrome individuals also almost invariably develop Alzheimer’s disease, a form of dementia that is fairly common among the elderly people. People with Down’s syndrome develop this disease in their fourth or fifth decade of life, much sooner than other people. These people are also characterized by presence of webbed neck, Plamers crease, very broad forehead, round face and forked tongue.