General Science Questions (MCQs) for Competitive Examinations

Notes:
Blood pressure is usually expressed in terms of the systolic (maximum) pressure over diastolic (minimum) pressure and is measured in millimetres of mercury (mm Hg). It is one of the vital signs along with respiratory rate, heart rate, oxygen saturation, and body temperature. Normal resting blood pressure in an adult is approximately 120/80 mm Hg.

Notes:
According to the K+ ion theory the guard cells absorb K+ ions from the cells around them as they produce ATP (due to photosynthesis) and become hypertonic. This leads to absorption of water from nearby cells by endosmosis due to which the guard cells become turgid and the stomata opens. Decreasing light intensity and photosynthesis causes Stomatal closing.

Notes:
Methane (CH4) is a greenhouse gas and causes warming the same way that CO2 does. It absorbs radiation emitted from the surface and re-emits that radiation in all directions with some of the radiation returning to the surface where it is absorbed and converted to heat. In the first two decades after its release, methane is 84 times more potent than carbon dioxide.

Notes:
During glycolysis, glucose is broken down in ten steps to two molecules of pyruvate in cytoplasm (in the cellular matrix called cytosol). It then enters the mitochondria where it is oxidised through the tricarboxylic acid cycle to carbon dioxide and water.

Notes:
Beriberi is a disease caused by a vitamin B1 (thiamine) deficiency. There are two types of the disease: wet beriberi and dry beriberi. Wet beriberi affects the heart and circulatory system. In extreme cases, wet beriberi can cause heart failure. Dry beriberi damages the nerves and can lead to a loss of muscle strength and eventually, muscle paralysis.

Notes:
Frogs that spend the coldest times of the year inside of the mud or within rotten heaps of leaves during hibernation receive their necessary oxygen through their skin. This is referred to as cutaneous gas exchange. They use their skin to soak in the oxygen their bodies require. Outside of hibernation period, frogs usually respire using their lungs.

Notes:
Some plants have the stem branching out near the base. The stem is hard but not thick. Such plants are called shrubs. Eg: Rose plant. Shrubs have persistent woody stems above the field, unlike herbaceous plants. Shrubs may be evergreen or deciduous. By their numerous stems and shorter height, less than 6 m-10 m long, they are distinguished from trees.

Notes:
A typical adult human skeleton consists of 206 bones. Individuals may have more or fewer bones than this owing to anatomical variations. These include: 22 Cranial and Facial Bones; 6 Ear Bones; 1 Throat Bone; 4 Shoulder Bones; 25 Chest Bones; 26 Vertebral Bones; 6 Arm and Forearm Bones; 54 Hand Bones; 2 Pelvic Bones; 8 Leg Bones; and 52 Foot Bones.

Notes:
Palisade parenchyma is the layer of tissue directly beneath the epidermis of the upper surface of a leaf. It contains the cylinder-shaped cells that hold the chloroplasts and constitutes the primary area of photosynthesis that converts the light energy to the chemical potential energy of carbohydrates.

Notes:
Photorespiration is a special type of respiration shown by many green plants when they are exposed to light. Glycolate (glycolic acid) is the chief metabolite of photorespiration and also its substrate. Other important metabolites are the amino acids glycine and serine.