Question Discussion & Solution

The correct answer is Cell.

Key Points

• Cell:
  • A cell is the smallest unit capable of independent existence which can reproduce itself. Hence, Option 3 is correct.
  • All living organisms, except for viruses, are composed of one or more cells.
  • Single-cell organisms; such as, bacteria, protozoa, and other micro-organisms are termed unicellular, while plants and animals that contain many cells are termed multicellular.
  • Highly complex organisms; such as, human beings consist of billions of cells, all of which are adapted to carry out specific functions; for example, groups of these specialized cells are organized into tissue and bodily organs.
  • Although cells may differ widely in size, appearance, and function, their essential features are similar.

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Important Points

• Almost all cells perform biochemical processes, generate and process energy, and store genetic information to be passed down to future generations of cells.
• Advanced single-celled and multicelled organisms have nuclei that carry the DNA, primitive cells; such as, bacteria, have no nucleus and carry their DNA loosely in coils throughout the cells
• The number of cells in an organism varies; for example, bacteria are single-celled organisms; the average adult human body has about one hundred trillion cells.
• Cells are the structural unit of all organisms and come in a range of sizes and shapes.
• Animal cells contain only an outside cell membrane.
• In most fungi, bacteria, and plants; there is a rigid cell wall outside the membrane.
• Each cell is composed of a mass of jelly-like substance called the cytoplasm, surrounded by a membrane.

Additional Information

The correct answer is All of the above.

Key Points

• Living organisms share characteristics such as the ability to move and reproduce.
• There are different types of living organisms including plants, animals, fungi, bacteria, and protoctists.
• Characteristics of living organisms:
  • Movement - they can move and change their position.
  • Reproduction – they can make more of the same kind of organism as themselves.
  • Sensitivity – they can detect or sense stimuli and respond to them.
  • Growth - they can permanently increase their size or dry mass by increasing the number or size of their cells.
  • Respiration – they can create chemical reactions that break down nutrient molecules in living cells to release energy.
  • Excretion – they can excrete toxic materials, waste products of metabolism, and excess substances.
  • Nutrition - they can take in and absorb nutrients such as organic substances and mineral ions. These nutrients contain the raw materials or energy needed for growth and tissue repair.

  Additional Information

• Cells are the building blocks of every living organism.
• Two-thirds of a cell is composed of water and is made up of biological molecules such as proteins and lipids.
• They provide a definite structure to the body, help to break down food, and release energy which is used up by our body to perform multiple tasks throughout the day.

Oboe is a musical instrument. Similarly, scalpel is a surgical instrument used in surgeries.

The correct answer is Leeuwenhoek.

Key Points

Additional Information

• Penicillin:
  • Penicillin is one of the first and still one of the most widely used antibiotic agents, derived from the Penicillium mold.
  • In 1928 Scottish bacteriologist Alexander Fleming first observed that colonies of the bacterium Staphylococcus aureus failed to grow in those areas of a culture that had been accidentally contaminated by the green mold Penicillium notatum.
  • He isolated the mold, grew it in a fluid medium, and found that it produced a substance capable of killing many of the common bacteria that infect humans.
  • Australian pathologist Howard Florey and British biochemist Ernst Boris Chain isolated and purified penicillin in the late 1930s, and by 1941 an injectable form of the drug was available for therapeutic use.
• Microscope:
  • Microscope is an instrument that produces enlarged images of small objects, allowing the observer an exceedingly close view of minute structures at a scale convenient for examination and analysis.
  • Although optical microscopes are the subject of this article, an image may also be enlarged by many other waveforms, including acoustic, X-ray, or electron beam, and be received by direct or digital imaging or by a combination of these methods.
  • The microscope may provide a dynamic image (as with conventional optical instruments) or one that is static (as with conventional scanning electron microscopes).
• Reverse transcriptase:
  • Reverse transcriptase also called RNA-directed DNA polymerase, an enzyme encoded from the genetic material of retroviruses that catalyzes the transcription of retrovirus RNA (ribonucleic acid) into DNA (deoxyribonucleic acid).
  • This catalyzed transcription is the reverse process of normal cellular transcription of DNA into RNA, hence the names reverse transcriptase and retrovirus.
  • Reverse transcriptase is central to the infectious nature of retroviruses, several of which cause disease in humans, including human immunodeficiency virus (HIV), which causes acquired immunodeficiency syndrome (AIDS), and human T-cell lymphotropic virus I (HTLV-I), which causes leukemia.
• Bacteria:
  • Bacteria, singular bacterium, any of a group of microscopic single-celled organisms that live in enormous numbers in almost every environment on Earth, from deep-sea vents to deep below Earth’s surface to the digestive tracts of humans.
  • Bacteria lack a membrane-bound nucleus and other internal structures and are therefore ranked among the unicellular life-forms called prokaryotes.
  • Prokaryotes are the dominant living creatures on Earth, having been present for perhaps three-quarters of Earth history and having adapted to almost all available ecological habitats.
  • As a group, they display exceedingly diverse metabolic capabilities and can use almost any organic compound, and some inorganic compounds, as a food source.

The correct answer is Ctrl+U.

Key Points

• In Microsoft Outlook, pressing Ctrl+U marks a selected read e-mail as un-read.

Additional Information

• Microsoft Outlook Keyboard Shortcuts