Water and Hydrogen Bonds in Biology

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Questions and Answers

What is the term used to describe the attractive force between dissimilar molecules?

Hydrophobic exclusion

Thermal stability

Adhesion (correct)

Cohesion

Why does water have a high specific heat?

Owing to weak van der Waals forces

Due to its non-polar nature

Because of its low molecular weight

Resulting from hydrogen bonding (correct)

What does the heat of vaporization indicate about water?

It is equivalent to the boiling point of water

It contributes to cooling through evaporation (correct)

It defines the freezing point of water

It requires minimal energy to evaporate

What occurs due to hydrophobic exclusion in water?

Water molecules coalesce around hydrophobic substances Signup and view all the answers

How does adhesion contribute to water movement in vessels?

It holds and prevents backward flow of water Signup and view all the answers

What is the relationship between the ionization of water and its role as an amphoteric substance?

Water's ionization allows it to either donate or accept protons. Signup and view all the answers

Which property of water allows ice to float on its surface?

Water expands below 4°C, decreasing its density. Signup and view all the answers

What distinguishes carbohydrates from other biomolecules in terms of their composition?

They have a 2:1 ratio of hydrogen to oxygen similar to water. Signup and view all the answers

How do carbohydrates primarily contribute to plant biology?

They are the main products of photosynthesis and provide energy. Signup and view all the answers

What unusual behavior of water below 4°C is essential for sustaining life, particularly in aquatic environments?

Water expands, allowing organisms to thrive under frozen surfaces. Signup and view all the answers

What is the primary reason that water is considered an excellent solvent for ionic compounds?

Its polarity promotes ion-dipole interactions. Signup and view all the answers

Which of the following best describes the nature of hydrogen bonds?

They are attractive forces based on partial electrical charges. Signup and view all the answers

How does water's cohesive force of attraction affect its properties in biological systems?

It facilitates the movement of nutrients in plant tissues. Signup and view all the answers

In what way does the structure of water contribute to its high specific heat capacity?

The large number of hydrogen bonds limits molecular movement. Signup and view all the answers

Which statement accurately reflects the significance of water's chemical composition?

Water's structural composition promotes enzymatic reactions. Signup and view all the answers

What characteristics differentiate oligosaccharides from monosaccharides?

Oligosaccharides consist of 2 to 10 monosaccharides. Signup and view all the answers

Which of the following statements is true regarding reducing and non-reducing sugars?

Non-reducing sugars lack free aldehyde or ketone groups. Signup and view all the answers

Why is sucrose an effective sugar for transport in living organisms?

It is a non-reducing sugar that does not react or oxidize. Signup and view all the answers

What is the nature of the bond formed between monosaccharides in oligosaccharides?

Glycosidic bond Signup and view all the answers

Which of the following examples correctly categorizes reducing and non-reducing sugars?

Lactose is a reducing sugar; sucrose is a non-reducing sugar. Signup and view all the answers

Which of the following accurately describes the empirical formula of monosaccharides?

CnH₂nOn Signup and view all the answers

What type of saccharides are Glycerose and Dihydroxyacetone classified as?

Triose Signup and view all the answers

Which statement about hexoses is true?

Glucose is classified as a hexose and is common in many natural sources. Signup and view all the answers

Which of the following examples is NOT a monosaccharide?

Sucrose Signup and view all the answers

Which class of monosaccharides is characterized by having four carbon atoms?

Tetrose Signup and view all the answers

What is the main distinguishing feature of saturated acylglycerol?

Is typically solid at room temperature Signup and view all the answers

What role do phospholipids primarily play in cellular structure?

They form the structural framework of the cell membrane Signup and view all the answers

How does the energy content of triglycerides compare to that of carbohydrates?

It is more than twice that of carbohydrates Signup and view all the answers

What is a primary characteristic of the hydrophobic end of phospholipids?

It repels water due to its nonpolar nature Signup and view all the answers

What is the main product formed when glycerol combines with three fatty acids?

Triglyceride Signup and view all the answers

Which function do digestive enzymes primarily serve?

Help in digestion of food by hydrolysis into simple monomers. Signup and view all the answers

What characteristic distinguishes lipids from carbohydrates?

Insolubility in water and solubility in organic solvents. Signup and view all the answers

Which statement accurately describes triglycerides?

They are esters formed via condensation of glycerol and three fatty acids. Signup and view all the answers

What is the primary role of hormones like insulin and thyroxin?

They coordinate different functions of the body. Signup and view all the answers

In the context of lipids, what does the term esterification refer to?

The bond formation between glycerol and fatty acids through water removal. Signup and view all the answers

What type of proteins are hemoglobin and albumin classified as?

Transport proteins. Signup and view all the answers

How do contractile proteins like actin and myosin function in the body?

By facilitating muscle contraction. Signup and view all the answers

What distinguishes the energy content of lipids compared to carbohydrates?

Lipids contain almost double the amount of energy compared to carbohydrates. Signup and view all the answers

What structural characteristic differentiates cellulose from chitin?

Cellulose is a polymer primarily of glucose. Signup and view all the answers

Which property of chitin allows it to bond more strongly than cellulose?

The presence of nitrogen. Signup and view all the answers

What distinguishes the physical state of chitin in nature compared to its pure form?

Chitin is often found in modified forms. Signup and view all the answers

How does cellulose contribute to the structure of plant cells?

By creating the cell walls. Signup and view all the answers

What is the solubility characteristic of cellulose?

It is insoluble in water. Signup and view all the answers

Which statement accurately describes the composition of starch?

Starch is formed by the condensation of monosaccharides, primarily glucose, into straight and branched chains. Signup and view all the answers

What color does glycogen produce when reacted with iodine?

Red Signup and view all the answers

Where is glycogen primarily stored in animals?

In the liver and muscles Signup and view all the answers

Which of the following pairs correctly identify the polysaccharide and its type?

Chitin - structural polysaccharide Signup and view all the answers

Which structural feature differentiates amylopectin from amylose?

Presence of α-1,6-glycosidic linkages at branch points Signup and view all the answers

Which of the following proteins is primarily responsible for providing strength and elasticity to human tissues and organs?

Collagen Signup and view all the answers

Which structural protein is associated with the formation of microtubules?

Tubulin Signup and view all the answers

What is the primary function of amyloid as a structural protein?

As a cell surface protein Signup and view all the answers

Which of the following proteins is NOT categorized as a structural protein in the provided information?

Myoglobin Signup and view all the answers

What distinctive role does fibrillin play in the body compared to other structural proteins?

Providing framework for elastic tissues Signup and view all the answers

Study Notes

Water

Water is essential for all living organisms and makes up the majority of a cell's composition (between 70-90%).
It acts as the medium for nearly all cellular reactions, playing a crucial role in many biochemical reactions like hydrolysis and photosynthesis.
Its polar nature, resulting from the difference in electronegativity between hydrogen and oxygen atoms, makes it an excellent solvent for ionic compounds.

Hydrogen Bonds

A hydrogen bond is an intermolecular attractive force between two molecules.
One molecule contains a partially charged hydrogen atom (H⁺), while the other contains a partially charged oxygen atom (O⁻).
These partial charges attract the molecules together, forming a hydrogen bond.

Cohesive Force of Attraction

The attraction between similar molecules is called cohesion.
Water molecules attract each other due to hydrogen bonds, forming long chains.
This contributes to water's ability to flow freely as protoplasm within cells, blood in vessels, and as a transporting fluid in plant tissues.

Adhesive Force of Attraction

The attraction between dissimilar molecules is called adhesion.
Due to its polarity, water attracts and holds charged molecules.
This helps hold water molecules in vessels and prevents backward flow.

High Specific Heat

Specific heat is the amount of heat energy required to raise the temperature of 1 gram of a substance by 1°C.
Water has a high specific heat due to its polar nature and hydrogen bonding.
It requires a significant amount of heat to change its temperature, acting as a temperature stabilizer, protecting organisms from sudden thermal changes.

High Heat of Vaporization

The amount of heat needed to convert water from liquid to vapor is called the heat of vaporization.
Water has a very high heat of vaporization (574 kcal/kg).
This contributes to its stability and plays a crucial role in thermoregulation, providing a cooling effect during evaporation.

Hydrophobic Exclusion

Water has a tendency to coalesce oil droplets into large droplets.
The presence of hydrophobic oils disrupts the hydrogen bonding between water molecules, causing them to form new bonds with themselves.
This excludes hydrophobic substances (like oils) from water.

Ionization of Water

Water molecules ionize into H⁺ and OH⁻ ions.
This reaction is reversible and maintains equilibrium.
Water also acts as an amphoteric substance (acid or base), and a buffer, maintaining pH levels for enzymatic activity in cells and organs.

Anomalous Behavior of Water

Water exhibits unusual behavior below 4°C.
Typically, matter contracts when cooled, but water expands below 4°C.
This expansion decreases its density, so at 0°C water is maximally expanded in ice form.
Ice is less dense than liquid water, allowing it to float on the surface, facilitating life under frozen water.

Carbohydrates

Carbohydrates are biomolecules composed of carbon, hydrogen, and oxygen, with a 2:1 ratio of hydrogen to oxygen like water.
Their general formula is CnH₂nOn.
They are categorized as polyhydroxy aldehydes or ketones.
Plants produce carbohydrates as primary products through photosynthesis.
They taste sweet and are therefore also called saccharides or sugars.
They are found extensively in all organisms, such as cellulose (plant cell walls), starch (stored in grains), and other materials.
Carbohydrates serve both structural and functional roles.

Classification of Carbohydrates

Carbohydrate molecules are also called "Saccharides".
They are classified into three groups:
- Monosaccharides
- Oligosaccharides
- Polysaccharides

Monosaccharides

Monosaccharides contain only one sugar molecule and cannot be hydrolyzed.
Their empirical formula is CnH₂nOn.
Examples include Ribose (C₅H₁₀O₅), Fructose (C₆H₁₂O₆), etc.
They are white crystalline solids, sweet-tasting, and soluble in water.
Monosaccharides are classified based on the number of carbon atoms present.

Oligosaccharides

Oligosaccharides are carbohydrates made up of 2 to 10 monosaccharides.
They are less sweet and less soluble in water compared to monosaccharides.
Hydrolysis of an oligosaccharide yields two or more monosaccharides.
The covalent bond between the monosaccharides is called a glycosidic bond or linkage.
Examples include sucrose, a disaccharide composed of glucose and fructose.

Reducing vs. Non-reducing Sugars

A reducing sugar can be oxidized and cause the reduction of other substances without hydrolysis.
This property is due to the presence of a free aldehyde or ketone group.
Examples of reducing sugars include maltose and lactose.
Non-reducing sugars cannot be oxidized and do not reduce other substances.
This is due to the absence of free aldehyde or ketone groups.
Examples include sucrose and raffinose.

Sugar Transport in Living Organisms

Living organisms, especially plants, transport sugars from sources to sinks (e.g., leaf to fruit) in the form of non-reducing sugars.
Glycosidic bonds are formed between carbonyl groups of the sugars.
Sucrose serves as a non-reducing sugar for efficient energy transport and storage.
It does not react or oxidize with other molecules during transport.

Polysaccharides

These are high molecular weight carbohydrates formed by the condensation of hundreds or thousands of monosaccharide units.
Examples include starch, glycogen, cellulose, and chitin.

Starch

Starch is the most important and abundant reserve food material in plants, found in cereals, legumes, tubers, and other vegetables.
It is made up of many glucose molecules joined together in a straight chain (amylose) which is soluble in hot water, and a branched chain (amylopectin) which is insoluble in hot and cold water.
Starch gives a blue color with iodine.

Glycogen

Glycogen is a polymer of glucose, similar in structure to starch, but found in animals.
It is commonly called animal starch, and is mainly found in bacteria, fungi, and in animals abundantly found in liver and muscles.
Glycogen gives a red color with iodine.

Cellulose

Cellulose is a polymer of glucose, the most abundant carbohydrate in nature.
It is insoluble in water and not digested by the human body.
Glucose units in cellulose form straight chains that coil and condense into tubes.
These tubes form the cell walls of plant cells.
Cellulose does not react with iodine.

Chitin

Chitin is a long-chain polymer of N-acetyl glucosamine, an amide derivative of glucose.
Its structure is similar to cellulose, forming crystalline nano-fibrils.
Functionally, it is comparable to keratin protein.
Chitin contains nitrogen, which allows for increased hydrogen bonding between adjacent polymer chains, leading to greater strength.
In its pure form, chitin is translucent, pliable, and resilient.
However, it is often found in modified forms, such as in the exoskeletons of insects (with $CaCO_3$) and shells of mollusks and crustaceans.
In these modified forms, the composite material becomes much harder and stiffer than pure chitin.

Globular Proteins

These proteins are spherical or ellipsoidal due to their three-dimensional folding of secondary protein structure.
They are either tertiary or quaternary proteins.
These proteins are soluble in salt, acid, or base-containing aqueous media or alcohol.
They can also be crystallized.
These proteins function as enzymes, antibodies, hormones, and hemoglobin.

Structural Proteins

Actin: Muscle forming protein
Amyloid: Works as cell surface protein
Caddisfly (Fibroin): Used to bind debris like rocks, sticks, twigs, and shells for net of prey
Condrocalein: Forms extra cellular matrix
Collagen: Provides strength, turned elasticity to skin, main component of cartilage, ligaments, tendon, bone, and teeth. Also provides resilience and elasticity to tissues and organs. Glycoproteins provide force bearing structural support in elastic and non-elastic connective tissues. Nutritious protein derived from collagen of skin and bones.
Elastin: Provides elasticity to tissues and organs.
Fibrillin: Important component of connective tissues providing support and flexibility.
Gelatin: Nutritious protein derived from collagen of skin and bones.
Sclera protein: Includes Keratin, collagen, elastin and fibrin
Titin: Provides elastic stabilization of myosin and actin filament.
Tubulin: Microtubules forming protein
Keratin: Nails and hairs forming protein

Functional Proteins

Digestive enzymes: Amylase, lipase, pepsin, trypsin - Help in digestion of food by hydrolysis into simple monomers.
Transport: Hemoglobin, albumin - Carry O₂ and CO₂, other substances in the blood or lymph throughout the body.
Hormones: Insulin, thyroxin - Co-ordinate different functions of the body.
Defenses: Interferon, immunoglobulin - Protect the body from foreign pathogens.
Contractile: Actin, myosin - Muscle contraction.
Storage: Legume storage protein, egg white (albumin) - Provide nourishment at the time of development of the embryo.

Lipids

Lipids are a diverse group of biological molecules, widely distributed among plants and animals.
They are insoluble in water and soluble in organic solvents like ether and alcohol.
These compounds are made up of C, H, O, like carbohydrates, but contain much lesser ratio of oxygen than carbohydrates.
Due to the high quantity of carbon and hydrogen, they contain almost double the amount of energy than carbohydrates.

Acylglycerol (Fats and Oils)

Are condensation products of glycerol and three fatty acids, commonly called fats and oils.
They can be defined as the esters of glycerol and fatty acid.
Ester is the bond or linkage formed between alcohol and organic acid by removing water; this reaction is called esterification.

Glycerol and Fatty Acids

Glycerol is a trihydroxy alcohol, with three carbon atoms and one OH group.
A fatty acid is an organic acid with a long hydrocarbon chain and one carboxylic acid group.
When three fatty acids combine with glycerol, forming three ester bonds, a compound called triglycerol (or triglyceride) is produced.
Triglycerides have no charge-bearing OH groups.

Saturated Acylglycerol (Fats)

These contain saturated fatty acids, meaning no double bonds between carbon atoms e.g., stearic acid.

Unsaturated Acylglycerol (Oils)

These contain unsaturated fatty acids, with one or more double bonds between carbon atoms.
They are typically liquid at room temperature, e.g., linoleic acid.
Found commonly in plants.

Acylglycerol

Acylglycerol provides energy for various metabolic activities and is rich in chemical energy.
The energy content is roughly twice that of carbohydrates.

Phospholipids

Phospholipids are a type of lipid composed of glycerol, two fatty acids, choline, and a phosphate group.
They are similar to triglycerides except that one fatty acid is replaced by a phosphate group that links to choline.
Phospholipids have two distinct ends:
- Hydrophobic end: The fatty acid part is nonpolar and repels water.
- Hydrophilic end: The phosphate and choline part are polar, therefore attracts water.
Due to these different properties, phospholipids are crucial components of cell membranes in all living organisms.
They regulate cell permeability and are involved in several vital cellular functions.

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Description

Explore the essential role of water and hydrogen bonds in biological systems. Understand how water's properties contribute to cellular processes and the significance of cohesive forces among water molecules. Delve into the biochemical importance of these interactions.