Biological Roles of Water: Why is water necessary for life? - Science in the News (2022)

by Molly Sargen
figures by Daniel Utter

Water makes up 60-75% of human body weight. A loss of just 4% of total body water leads to dehydration, and a loss of 15% can be fatal. Likewise, a person could survive a month without food but wouldn’t survive 3 days without water. This crucial dependence on water broadly governs all life forms. Clearly water is vital for survival, but what makes it so necessary?

The Molecular Make-up of Water

Many of water’s roles in supporting life are due to its molecular structure and a few special properties. Water is a simple molecule composed of two small, positively charged hydrogen atoms and one large negatively charged oxygen atom. When the hydrogens bind to the oxygen, it creates an asymmetrical molecule with positive charge on one side and negative charge on the other side (Figure 1). This charge differential is called polarity and dictates how water interacts with other molecules.

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Biological Roles of Water: Why is water necessary for life? - Science in the News (1)

Water is the “Universal Solvent”

As a polar molecule, water interacts best with other polar molecules, such as itself. This is because of the phenomenon wherein opposite charges attract one another: because each individual water molecule has both a negative portion and a positive portion, each side is attracted to molecules of the opposite charge. This attraction allows water to form relatively strong connections, called bonds, with other polar molecules around it, including other water molecules. In this case, the positive hydrogen of one water molecule will bond with the negative oxygen of the adjacent molecule, whose own hydrogens are attracted to the next oxygen, and so on (Figure 1). Importantly, this bonding makes water molecules stick together in a property called cohesion. The cohesion of water molecules helps plants take up water at their roots. Cohesion also contributes to water’s high boiling point, which helps animals regulate body temperature.

Furthermore, since most biological molecules have some electrical asymmetry, they too are polar and water molecules can form bonds with and surround both their positive and negative regions. In the act of surrounding the polar molecules of another substance, water wriggles its way into all the nooks and crannies between molecules, effectively breaking it apart are dissolving it. This is what happens when you put sugar crystals into water: both water and sugar are polar, allowing individual water molecules to surround individual sugar molecules, breaking apart the sugar and dissolving it. Similar to polarity, some molecules are made of ions, or oppositely charged particles. Water breaks apart these ionic molecules as well by interacting with both the positively and negatively charged particles. This is what happens when you put salt in water, because salt is composed of sodium and chloride ions.

Water’s extensive capability to dissolve a variety of molecules has earned it the designation of “universal solvent,” and it is this ability that makes water such an invaluable life-sustaining force. On a biological level, water’s role as a solvent helps cells transport and use substances like oxygen or nutrients. Water-based solutions like blood help carry molecules to the necessary locations. Thus, water’s role as a solvent facilitates the transport of molecules like oxygen for respiration and has a major impact on the ability of drugs to reach their targets in the body.

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Water Supports Cellular Structure

Water also has an important structural role in biology. Visually, water fills cells to help maintain shape and structure (Figure 2). The water inside many cells (including those that make up the human body) creates pressure that opposes external forces, similar to putting air in a balloon. However, even some plants, which can maintain their cell structure without water, still require water to survive. Water allows everything inside cells to have the right shape at the molecular level. As shape is critical for biochemical processes, this is also one of water’s most important roles.

Biological Roles of Water: Why is water necessary for life? - Science in the News (2)

Water also contributes to the formation of membranes surrounding cells. Every cell on Earth is surrounded by a membrane, most of which are formed by two layers of molecules called phospholipids (Figure 3). The phospholipids, like water, have two distinct components: a polar “head” and a nonpolar “tail.” Due to this, the polar heads interact with water, while the nonpolar tails try to avoid water and interact with each other instead. Seeking these favorable interactions, phospholipids spontaneously form bilayers with the heads facing outward towards the surrounding water and the tails facing inward, excluding water. The bilayer surrounds cells and selectively allows substances like salts and nutrients to enter and exit the cell. The interactions involved in forming the membrane are strong enough that the membranes form spontaneously and aren’t easily disrupted. Without water, cell membranes would lack structure, and without proper membrane structure, cells would be unable to keep important molecules inside the cell and harmful molecules outside the cell.

Biological Roles of Water: Why is water necessary for life? - Science in the News (3)

In addition to influencing the overall shape of cells, water also impacts some fundamental components of every cell: DNA and proteins. Proteins are produced as a long chain of building blocks called amino acids and need to fold into a specific shape to function correctly. Water drives the folding of amino acid chains as different types of amino acids seek and avoid interacting with water. Proteins provide structure, receive signals, and catalyze chemical reactions in the cell. In this way, proteins are the workhorses of cells. Ultimately proteins drive contraction of muscles, communication, digestion of nutrients, and many other vital functions. Without the proper shape, proteins would be unable to perform these functions and a cell (let alone an entire human) could not survive. Similarly, DNA needs to be in a specific shape for its instructions to be properly decoded. Proteins that read or copy DNA can only bind DNA that has a particular shape. Water molecules surround DNA in an ordered fashion to support its characteristic double-helix conformation. Without this shape, cells would be unable to follow the careful instructions encoded by DNA or to pass the instructions onto future cells, making human growth, reproduction, and, ultimately, survival infeasible .

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Chemical Reactions of Water

Water is directly involved in many chemical reactions to build and break down important components of the cell. Photosynthesis, the process in plants that creates sugars for all life forms, requires water. Water also participates in building larger molecules in cells. Molecules like DNA and proteins are made of repetitive units of smaller molecules. Putting these small molecules together occurs through a reaction that produces water. Conversely, water is required for the reverse reaction that breaks down these molecules, allowing cells to obtain nutrients or repurpose pieces of big molecules.

Additionally, water buffers cells from the dangerous effects of acids and bases. Highly acidic or basic substances, like bleach or hydrochloric acid, are corrosive to even the most durable materials. This is because acids and bases release excess hydrogens or take up excess hydrogens, respectively, from the surrounding materials. Losing or gaining positively-charged hydrogens disrupts the structure of molecules. As we’ve learned, proteins require a specific structure to function properly, so it’s important to protect them from acids and bases. Water does this by acting as both an acid and a base (Figure 4). Although the chemical bonds within a water molecule are very stable, it’s possible for a water molecule to give up a hydrogen and become OH, thus acting as a base, or accept another hydrogen and become H3O+, thus acting as an acid. This adaptability allows water to combat drastic changes of pH due to acidic or basic substances in the body in a process called buffering. Ultimately, this protects proteins and other molecules in the cell.

Biological Roles of Water: Why is water necessary for life? - Science in the News (4)

In conclusion, water is vital for all life. Its versatility and adaptability help perform important chemical reactions. Its simple molecular structure helps maintain important shapes for cells’ inner components and outer membrane. No other molecule matches water when it comes to unique properties that support life. Excitingly, researchers continue to establish new properties of water such as additional effects of its asymmetrical structure. Scientists have yet to determine the physiological impacts of these properties. It’s amazing how a simple molecule is universally important for organisms with diverse needs.

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Molly Sargen is a first-year PhD Student in the Biological and Biomedical Sciences Program at Harvard Medical School.

Dan Utter is a fifth-year PhD student in Organismic and Evolutionary Biology at Harvard University.

For More Information:

  • To learn more about the importance of drug solubility see this article.
  • Check out these articles for more information about proteins and how water impacts their folding.
  • Learn more about phospholipids here.
  • Learn more about water affects DNA structure here.
  • Learn more about acids and bases here.
  • Check out the unique properties of water at this page or recently discovered properties of water at this article.

This article is part of our special edition on water. To read more, check out our special edition homepage!

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FAQs

Why does life science need water? ›

Life needs chemical reactions to take place in order to gain energy, grow, and get rid of waste. Water is a liquid which allows the chemistry of life to take place. It is also a polar molecule which allows most other molecules to be dissolved. Because of this, we call water a “solvent”.

How important is water for the life of the earth? ›

Water, by its simplest definition, is life. Every living thing on Earth requires water to survive.

Is water necessary for all life? ›

All living things, from tiny cyanobacteria to giant blue whales , need water to survive. Without water, life as we know it would not exist. And life exists wherever there is water. All organisms, like animals and plants, use water: salty or fresh, hot or cold, plenty of water or almost no water at all.

How can you say water is necessary for us? ›

Water is necessary for us because the important use of water is to drink. If we don't drink water, we get dehydrated & health problems will occur. Other important uses are also their like bathing, washing clothes, washing utensils, cooking food & for farming. If we get water for farming, we don't get food to eat.

What is the importance of water? ›

Water helps your body:

Keep a normal temperature. Lubricate and cushion joints. Protect your spinal cord and other sensitive tissues. Get rid of wastes through urination, perspiration, and bowel movements.

What are the 10 importance of water? ›

Enough water intake prevents constipation, indigestion and other problems of gastrointestinal tract. Lack of fluids in the body makes stool tight and it tends to pull water from the colon resulting in constipation. Proper hydration improves digestion and allows maximum nutrient absorption in the blood.

What is the role of water in our body? ›

Water serves as a lubricant. It makes up saliva and the fluids surrounding the joints. Water regulates the body temperature through perspiration. It also helps prevent and relieve constipation by moving food through the intestines.

What are 5 properties of water that are important to life? ›

Discussion of the properties of water that make it essential to life as we know it: polarity, "universal" solvent, high heat capacity, high heat of vaporization, cohesion, adhesion and lower density when frozen.

Why is water essential for life Brainly? ›

Our bodies use water in all the cells, organs, and tissues, to help regulate body temperature and maintain other bodily functions. Because our bodies lose water through breathing, sweating, and digestion, it's crucial to rehydrate and replace water by drinking fluids and eating foods that contain water.

What is necessary for life to exist? ›

It is useful to categorize the requirements for life on Earth as four items: energy, carbon, liquid water, and various other elements.

What are 3 reasons why water is important? ›

Regulates body temperature. Moistens tissues in the eyes, nose and mouth. Protects body organs and tissues. Carries nutrients and oxygen to cells.

Why water is important for our life Write at least 10 points? ›

(1) Water is essential for our life, and there is no life without water on earth. (2) We get water from many sources like rivers, groundwater (wells), rain, etc. (3) We use water for drinking, cooking food, cleaning, and many other purposes. (4) Water is useful to grow plants and for agricultural life to get food.

Why is water essential for life write any two points? ›

It plays a vital role as all the metabolic processes required for growth and development requires a liquid medium. Most of the reactions occur when the substances are in the dissolved state. Water also helps in the transportation of these dissolved substances in the body.

What is the importance of water? ›

Water helps your body:

Keep a normal temperature. Lubricate and cushion joints. Protect your spinal cord and other sensitive tissues. Get rid of wastes through urination, perspiration, and bowel movements.

Why do cells need water? ›

Here are just a few important ways water works in your body:

Carries nutrients and oxygen to cells. Lubricates joints. Lessens burden the on kidneys and liver by flushing out waste products. Helps dissolve minerals and nutrients to make them accessible to your body.

What are 3 properties of water that are important to life? ›

Water is the medium of life. Its four key properties - thermal properties, ability to act as a universal solvent, cohesion and adhesion - help support the life processes and habitats of virtually all organisms.

What are the 10 importance of water? ›

Enough water intake prevents constipation, indigestion and other problems of gastrointestinal tract. Lack of fluids in the body makes stool tight and it tends to pull water from the colon resulting in constipation. Proper hydration improves digestion and allows maximum nutrient absorption in the blood.

Why water is important for our life Write at least 10 points? ›

(1) Water is essential for our life, and there is no life without water on earth. (2) We get water from many sources like rivers, groundwater (wells), rain, etc. (3) We use water for drinking, cooking food, cleaning, and many other purposes. (4) Water is useful to grow plants and for agricultural life to get food.

Why is water important 10 points? ›

1) Water is a colorless, tasteless and odorless substance essential for the survival of living beings. 2) Water is the essential element for all human beings, animals and plants. 3) Water comprises of more than 71% of the earth's surface. 4) Water is derived from various sources like rivers, lakes, oceans, and streams.

What are the uses of water essay? ›

Water is essentially needed for different purposes like for drinking, cooking, washing, for agriculture, industry etc. Apart from drinking water, we use it at home for various domestic purposes. We use it for bathing, washing our clothes, utensils, vehicles and other things.

What would happen without water? ›

Without enough water, the kidneys use more energy and wear on tissue. Your kidneys need to function adequately to flush out waste from your blood. Eventually, your kidneys will cease to function without adequate water intake. Other organs in your body may also cease to function without water.

What is water in biology? ›

water, a substance composed of the chemical elements hydrogen and oxygen and existing in gaseous, liquid, and solid states. It is one of the most plentiful and essential of compounds. A tasteless and odourless liquid at room temperature, it has the important ability to dissolve many other substances.

What is one role water plays in living organisms? ›

Water helps to regulate the body temperature, keeps the eyes, mouth, and nose and internal organs moisturized/hydrated, protect the cells, carries nutrients and oxygen, provides lubrication to the joints, and acts as a solvent to dissolve nutrients and minerals.

What is the most important property of water? ›

Water has the unique ability to dissolve many polar and ionic substances. This is important to all living things because, as water travels through the water cycle, it takes many valuable nutrients along with it! Water has high heat capacity.

What is properties of water in biology? ›

These include: Cohesion, Adhesion, High surface tension, High specific heat, High Heat of vaporization, and the fact that ice floats (Ice is less dense as a solid than liquid water). For each of these properties, we discuss how they impact living creatures on Earth.

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