GK Questions with Answers - Science

Science is one of the most essential subjects for students preparing for competitive exams like UPSC, SSC, Banking, Railways, Defence, and State PSCs. It forms the foundation of logical understanding and analytical thinking. Questions from Physics, Chemistry, and Biology are frequently asked in the general knowledge and general science sections of various exams. Having a clear understanding of scientific concepts, discoveries, inventions, and their applications helps students answer these questions accurately and enhances their overall awareness of everyday scientific phenomena.

In this article, we have compiled a set of Science GK Questions with Answers along with brief explanations to make learning easier and more effective. These MCQs cover important topics such as basic physics laws, chemical reactions, human body systems, space science, and everyday applications of science. Practicing these questions will not only help you revise key concepts but also strengthen your preparation for the general awareness and science sections of upcoming competitive exams 2025.

GK Questions with Answers - Science

1. What is the largest organ in the human body?

1. Liver
2. Heart
3. Skin
4. Lungs

Answer: C) Skin

Explanation: The skin is the largest organ of the human body, covering an average area of 1.5 to 2 square meters in adults. It accounts for around 16% of total body weight, making it the heaviest organ as well. The skin acts as the first line of defense against pathogens, harmful chemicals, and physical injuries. It plays a vital role in regulating body temperature through sweating and blood flow control.

2. How many bones are there in the human body?

1. 206
2. 210
3. 201
4. 208

Answer: A) 206 bones

Explanation: The human skeleton is made up of 206 bones in adulthood. A newborn baby has about 270 bones, but many of them fuse together during growth. The human skeleton is divided into two main parts: 1.Axial Skeleton (80 bones) includes the skull, vertebral column, and rib cage 2.Appendicular Skeleton (126 bones) includes the bones of arms, legs, shoulders, and pelvic girdle. The longest bone in the human body is the femur (thigh bone). The smallest bone is the stapes bone in the middle ear.

3. Which is the largest bone in the human body?

1. Tibia
2. Femur
3. Humerus
4. Pelvis

Answer: B) Femur (Thigh Bone)

Explanation: The femur is the longest, heaviest, and strongest bone in the human body. It connects the hip joint (pelvis) to the knee joint, forming the main structure of the thigh. The average adult femur is about 18–19 inches (45–48 cm) in length. The femur supports the entire body weight when standing and during locomotion. The femur is essential for walking, running, and jumping, providing leverage and mobility. Because it is very dense and strong, it is also the least likely bone to break, though fractures may occur due to severe trauma. In addition to support, the femur contains bone marrow, which helps in the production of blood cells.

4. Which is the largest cell in the human body?

1. Nerve cell
2. Muscle cell
3. Liver cell
4. Ovum

Answer: D) Ovum (female gamete)

Explanation: The ovum (egg cell) is the largest cell in the human body, measuring about 100 micrometers (0.1 mm) in diameter. It is a female reproductive cell (gamete) that combines with the male gamete (sperm cell) during fertilization to form a zygote. The large size of the ovum allows it to store nutrients and cytoplasmic materials that support the initial stages of embryonic growth. The ovum is spherical in shape and is visible to the naked eye without a microscope. While the ovum is the largest cell, the sperm cell is the smallest cell in the human body.

5. Which is the longest cell in the human body?

1. Muscle cell
2. Nerve cell
3. Bone cell
4. Blood cell

Answer: B) Nerve cell

Explanation: The nerve cell (neuron) is the longest cell in the human body, with some extending up to 100 cm (1 meter). A neuron consists of three main parts: 1.Cell body (soma) contains the nucleus and cytoplasm 2.Dendrites is a Branch-like structures that receive signals from other neurons 3.Axon is A long fiber that carries signals away from the cell body. The length of a neuron is mainly due to its axon, which can stretch from the spinal cord to the toes in humans. Neurons are responsible for carrying messages in the form of electrical impulses throughout the nervous system.

6. Who discovered penicillin?

1. Louis Pasteur
2. Robert Koch
3. Alexander Fleming
4. Edward Jenner

Answer: C) Alexander Fleming

Explanation: Penicillin, the world’s first true antibiotic, was discovered by Alexander Fleming in 1928. While working at St. Mary’s Hospital in London, Fleming observed that a mold called Penicillium notatum (now Penicillium chrysogenum) accidentally contaminated one of his Petri dishes containing staphylococcus bacteria. He noticed that the bacteria around the mold were destroyed, while those farther away remained unharmed. This observation led him to identify penicillin as a substance capable of killing or inhibiting the growth of many harmful bacteria.

7. How many chambers does the human heart have?

1. Four
2. Two
3. Five
4. Three

Answer: A) Four

Explanation: The human heart is a muscular organ responsible for pumping blood throughout the body. It is divided into four chambers - Two atria (upper chambers): Right atrium and left atrium - Two ventricles (lower chambers): Right ventricle and left ventricle. The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs for oxygenation. The left side of the heart receives oxygenated blood from the lungs and pumps it to the rest of the body. This double circulation system ensures continuous supply of oxygen and nutrients to tissues while removing carbon dioxide and waste products.

8. Which gas do plants absorb from the atmosphere?

1. Oxygen
2. Carbon Dioxide
3. Nitrogen
4. Hydrogen

Answer: B) Carbon Dioxide

Explanation: Plants absorb carbon dioxide (CO₂) from the atmosphere mainly through small openings on the leaves called stomata. Using this carbon dioxide, along with water absorbed by roots and sunlight, plants perform photosynthesis. In photosynthesis, plants convert carbon dioxide and water into glucose (food) and release oxygen as a by-product. This process is crucial for life on Earth, as it maintains the oxygen–carbon dioxide balance in the atmosphere.

9. What color is chlorophyll?

1. Red
2. Blue
3. Yellow
4. Green

Answer: D) Green

Explanation: Chlorophyll is a green pigment found in the chloroplasts of plant cells. It appears green because it absorbs red and blue wavelengths of light from the visible spectrum and reflects green light, which makes leaves look green to our eyes. Chlorophyll plays a crucial role in photosynthesis, as it captures light energy from the sun and converts it into chemical energy, which is used to produce food (glucose) for the plant.

10. What is the term for molten rock after it erupts from a volcano?

1. Magma
2. Lava
3. Basalt
4. Granite

Answer: B) Lava

Explanation: Molten rock beneath the Earth’s surface is called magma. When this magma rises through volcanic vents and erupts onto the Earth’s surface, it is called lava. Lava is extremely hot, ranging between 700°C and 1200°C. Once lava comes out, it cools and solidifies to form different types of igneous rocks such as basalt (from rapid cooling on the surface) or granite (from slow cooling beneath the surface). Lava flows shape landscapes, create volcanic islands (like Hawaii), and contribute to fertile soil after weathering. Thus, the correct term for molten rock after eruption is lava.