General Science Questions (MCQs) for Competitive Examinations

Notes:
Swine flu is a disease of pigs that can, in rare cases, be passed to humans. It is a highly contagious respiratory disease caused by one of many Influenza A viruses. The disease is spread among pigs by direct and indirect contact, aerosols, and from pigs that are infected but do not have symptoms.

Notes:
Most of Earth’s oxygen comes from tiny ocean plants – called phytoplankton – that live near the water’s surface and drift with the currents. Like all plants, they photosynthesize – that is, they use sunlight and carbon dioxide to make food. Scientists believe that phytoplankton contribute between 50 to 85 percent of the oxygen in Earth’s atmosphere (National Geographic).

Notes:
Chloramines are a group of chemical compounds that contain chlorine and ammonia. It is used as a disinfectant for water. The particular type of chloramine used in drinking water disinfection is called monochloramine. However, it is used as a secondary disinfectant that are added to water that has already been disinfected with a primary disinfectant, often chlorine using bleaching powder.

Notes:
The femur (pl. femurs or femora), or thigh bone, is the most proximal (closest to the center of the body) bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in the rear legs. By most measures the femur is not only the largest but also other of the strongest bones in the body head of the femur articulates with the acetabulum.

Notes:
Transcription is the first step of gene expression, in which a particular segment of DNA is copied into RNA by the enzyme, RNA polymerase. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand. The transcribed direct and oversee the translation of genes into specific protein synthesis once in cytoplasm.

Notes:
The term fine particles, or particulate matter 2.5 (PM2.5), refers to tiny particles or droplets in the air that are two and one half microns or less in width. Particles in the PM2.5 size range are able to travel deeply into the respiratory tract, reaching the lungs. Once in lungs, they block alveoli for gaseous exchange.

Notes:
The plasma membrane allows or permits the entry and exit of some materials in and out of the cell. It also prevents movement of some other materials. The cell membrane, therefore, is called a selectively permeable membrane.

Notes:
A heterogeneous mixture is a mixture in which the composition is not uniform throughout the mixture. A suspension is a heterogeneous mixture in which solute-like particles settle out of a solvent-like phase sometime after their introduction. Examples of suspensions are: fine sand or silt in water or tomato juice.

Notes:
Reduction reaction is defined as the addition of hydrogen or removal of oxygen. Oxidation meant gaining oxygen. Because electrons are neither created nor destroyed in a chemical reaction, oxidation and reduction are linked. It is impossible to have one without the other.

Notes:
A reactive metal is one that readily reacts with other elements to give up its electrons. The order of intensity of reactivity is known as reactivity series. Potassium is at the top of the series and hence most reactive. Reactivity of some metals are given in descending order:

• K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu