Physical Science Lesson 13 the Structure and Properties of Matter

The Structure and Properties of Matter The Structure and Properties of Matter The Structure and Properties of Matter - The Structures, Properties, and Functions of Biomolecules

Objective  At the end of the lesson, lesson, you should be able able to explain how how the structures of biological biological macromolecules such as proteins, carbohydrates, lipids, and nucleic acids determine their properties and functions. Biomolecules are large organic compounds that are important to life’s processes processes,, such as respiration and metabolism. There are numerous biomolecules with different structures and functions. They are generally classified into four major groups – proteins, carbohydrates, carbohydra tes, lipids, and nucleic acids. In this lesson, you will look into the general structure, properties, properties, and functions fu nctions of each of these groups of biomolecule biomolecules. s.

Last Updated: 08.12.16

Learn about it! Proteins Proteins  are biomolecules composed of amino acid units. Amino Proteins are units. Amino acids acids are  are organic molecules that have a central carbon atom bonded to four different groups — an amino group (), an acidic carboxyl group (), a hydrogen atom, and a variable side chain, R. The side chain can range from a single hydrogen atom to complex ring structures.

In a protein, the amino acids are linked via a peptide bond. bond. This peptide bond is formed between an amino group of one amino acid and an acid carboxyl group of another amino acid. A chain of two or more amino acids linked together by peptide  bonds is called called a peptide peptide..

The smallest protein has about 50 amino acids. However, large proteins can have as many as 1000 amino acids, arranged in any possible sequence. It is estimated that human cells can create between 80 000 to 100 000 different proteins. The shape of a protein is important so that it can carry out its function. Long chains of amino acids fold into a unique three-dimensional shape. Some areas of the protein may twirl into helices, like the coils of a telephone cord. Other areas may be repeatedly bent into a pleated sheet, like the folds of an accordion. An important intermolecular force of attraction that dictate and maintain the shape of a protein is the hydrogen  bonding.

Properties Proteins can participate in neutral, acidic, or basic reactions because their amino acids have an acidic carboxyl end and a basic amino end. The amino acids are amphoteric which means they can function either as an acid or a base. Also, proteins have high molecular weights because they are comprised of many amino acids. Functions The sequence of amino acids determines the protein’s shape and function. Proteins play many important roles in living cells. They can hasten chemical reactions, transport substances, and provide structural support. Many proteins function as enzymes, which are molecules that catalyze or speed up chemical reactions in the body. The reactant molecules bind to the active site of the enzymes, where they react to form products. Enzymes have shapes that are highly specific for their functions. A slight change to their structures will inhibit them to do their function. Transport proteins carry small particles throughout the body. For example, the protein haemoglobin carries oxygen in the blood from the lungs to the rest of the body.  An important part of hemoglobin is its iron group (called heme), the part to which oxygen binds. Structural proteins are fibrous proteins which have long, thin structures. A typical example of a structural protein is keratin, which is a component of the protective covering of most animals – hair, nails, skin or feathers.

Learn about it!

Carbohydrates Carbohydrates are molecules that are composed of carbon, hydrogen, and oxygen. They have a general formula of . They can be grouped depending on the number of their monomer units called saccharides. Carbohydrates can be divided into three major groups: monosaccharides, disaccharides, and polysaccharides. Monosaccharides are the simplest form of carbohydrates. They contain either five or six carbon atoms. They have open-chain and cyclic forms. A typical example of monosaccharide is glucose, , one of the products of photosynthesis in plants.

Disaccharides are two monosaccharides bonded to each other. The monosaccharides are linked through an ether () group. A common example of a disaccharide is the sweetener sucrose, or table sugar. Sucrose is formed by glucose and fructose.

Polysaccharides are long chains of monosaccharide units. They are also called complex carbohydrates. Similar to disaccharides, the monosaccharides in a polysaccharide are linked through an ether bond. An example of a polysaccharide is starch, which is used to store energy in plants. It is comprised solely of glucose subunits.

Properties Monosaccharides and disaccharides are small molecules with multiple polar groups so they are water soluble. Because they exhibit hydrogen bonding in their structures, they have high melting points. In comparison, polysaccharides are less soluble due to their large sizes and complex shapes. For example, starch and glycogen are both insoluble in water. On the other hand, cellulose, also water-insoluble, cannot be digested by humans because the appropriate enzyme to breakdown cellulose into simpler monosaccharides is lacking. Hence, nutritionists call cellulose as dietary fiber because it just passes through the digestive system unchanged. Functions The main function of carbohydrates is to store and provide energy . They are broken down into smaller glucose units that can be easily absorbed by the cells. When glucose is further broken down, the energy released by breaking its chemical bonds are used or stored by the body in the form of glycogen.

Some carbohydrates also serve as the framework of cellular structures. For example, cellulose makes up the cell wall of plant cells. Chitin, another carbohydrate, forms the exoskeleton of arthropods and the cell wall of fungal cells.

Learn about it! Lipids

Lipids are large, nonpolar biomolecules. They are mainly composed of carbon, hydrogen, and oxygen. Unlike proteins and carbohydrates, lipids are not polymers with repeating monomer subunits. They have many kinds including triglycerides, waxes, and steroids. Triglycerides Triglycerides are lipids composed of glycerol and fatty acids. Glycerol is a molecule  with three carbons, each containing a hydroxyl () group while fatty acid is a long chain of carboxylic acid.

 When three fatty acids bond to glycerol, they form ester bonds.

Triglycerides can be solid or liquid at room temperature. If solid at room temperature, they are called fats. Fats, such as lard and butter, are produced by animals. If liquid at room temperature, they are called oils. Oils, such as coconut and olive oils, are produced by plants. Waxes  Waxes are lipids that are composed of a fatty acid with a long chain of alcohol. They are produced by both plants and animals. Plants often produce wax that coats their leaves  which prevents them from drying out. Animals such as bees also produce wax. Bees create their honeycomb structures from beeswax.

 Steroids Steroids are lipids without fatty acid chains. Instead, they have multiple rings in their structures. They are built from the basic four-ring steroid structure.

 An example of a steroid is dietary lipid cholesterol. Cholesterol is the precursor of hormones such as estrogen and progesterone. Recall that hormones are molecules that communicate between organs to regulate physiology and behavior. Properties Lipids such as triglycerides and waxes are mostly made of nonpolar hydrocarbon chains, making them generally insoluble in water. The hydrocarbon chains are the “hydrophobic (water-fearing) tails” of lipids. On the other hand, their hydroxyl, ester, and ether groups can interact with water. These groups are called “hydrophilic (water-loving) heads.” When lipids are mixed with water, they arrange themselves in a spherical form called a micelle. Functions Lipids are the reserved sources of energy . The energy stored in their bonds is used  by the body for fuel. When the energy is abundant, cells store the excess energy in the fatty acids of triglycerides. Lipids like waxes are used as a protective coating of organisms. Because they are hydrophobic, lipids protect plants and animals from drying out by controlling evaporation.

Learn about it! Nucleic Acids

Nucleic acids, discovered by Friedrich Miescher in 1869, are biomolecules that are made up of repeating units of nucleotides. Nucleotides are monomers with three components, a 5-carbon sugar, a phosphate group, and a nitrogenous base. The nucleotides are linked through phosphodiester bonds.

If the sugar is ribose, then the nucleotides make up the ribonucleic acid (RNA). On the other hand, if the sugar is deoxyribose, then the nucleotides make up the deoxyribonucleic acid (DNA). Both DNA and RNA have nitrogenous bases. The five common nitrogenous bases are adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U).

Properties DNA and RNA are very stable molecules because of the stacking interaction between their hydrophobic parts. Also, hydrogen bonding present between the polar parts of the molecule plays a role in maintaining the structure of the nucleic acid. Functions

DNA contains the genetic instructions for the development and functioning of organisms. This genetic information is converted by the RNA into amino acid sequences of proteins. RNA has three types, messenger RNA  (mRNA), ribosomal RNA  (rRNA), and transfer RNA  (tRNA). The mRNA carries the genetic sequence information between the DNA and ribosomes. In ribosomes, proteins are synthesized. The rRNA catalyzes the peptide bond formation while the tRNA serve as the carrier molecules of the amino acids that make up the protein.

Try it!  A concept map is a graphic organizer that illustrates the connection between terms, ideas, concepts, and processes. Make a concept map of the four types of biomolecules and their properties and functions.

What do you think? How are nucleic acids related to proteins? What will happen to the protein being synthesized in the ribosomes if an error occurs in the genetic information passed from the DNA to the RNA?

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Biomolecules are large organic compounds that are important to life’s processes. They are generally classified into four major groups – proteins, carbohydrates, lipids, and nucleic acids. Proteins are biomolecules composed of amino acid units. The sequence of amino acids determines the protein’s shape and function. In the human body, proteins hasten chemical reactions, transport substances, and provide structural support. Carbohydrates are molecules that are composed of carbon, hydrogen, and oxygen. They have a general formula of . Their functions are to store energy and serve as the framework of cellular structures. Lipids are large, nonpolar biomolecules mainly composed of carbon, hydrogen, and oxygen. They function as reserved sources of energy and protective coating of organisms. Nucleic acids are biomolecules that are made up of repeating units of nucleotides, which are made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base. They encode, transmit, and express genetic information.

Question 1  Which of the following are biomolecules composed of amino acid units? Correct!

1proteins Proteins are biomolecules composed of amino acid units linked via peptide bonds. Next question

2carbohydrates3nucleic acids4lipids Question 2  Which of the following are examples of carbohydrates? Incorrect!

1triglyceride2glucose Carbohydrates are molecules that are composed of carbon, hydrogen, and oxygen. Examples of carbohydrates include glucose (monosaccharide) and glycogen (polysaccharide). Next question

3uracil4glycogen

Question 3 Fats and oils belong to which group of biomolecules? Incorrect!

2carbohydrates Fats and oils are triglycerides, which are lipids composed of glycerol and fatty acids. Next question

1lipids3nucleic acids4proteins Question 4  Which of the following biomolecules contain only carbon, hydrogen and oxygen? Correct!

1carbohydrates4lipids Carbohydrates and lipids are mainly composed of carbon, hydrogen, and oxygen. Proteins and nucleic acids contain other elements such as nitrogen, phosphorus, and sulfur. Next question

2nucleic acids3proteins Question 5  Which of the following statements is true about waxes? Correct!

1They are composed of a fatty acid with a long chain of alcohol.  Waxes are lipids that are composed of a fatty acid with a long chain of alcohol. They are produced by  both plants and animals. Next question

2They are biomolecules that are made up of repeating units of nucleotides.3They are complex carbohydrates composed of carbon, hydrogen, and oxygen. 4They are amphoteric  because their amino acids have an acidic carboxyl end and a basic amino end.

Question 6  Which of the following is the arrangement of triglycerides and waxes when they are mixed with  water? Incorrect!

3pleated sheet  When lipids are mixed with water, they arrange themselves in a spherical form called a micelle.

Next question

1cyclic2micelle4helix Question 7  Which of the following nucleic acids catalyzes the peptide bond formation? Correct!

2rRNA  The rRNA is the RNA component of ribosomes. It catalyzes the peptide bond formation during protein synthesis. Next question

1mRNA 3tRNA 4DNA  Question 8  Which of the following are functions of carbohydrates? Incorrect!

4speed up chemical reactions The main function of carbohydrates is to store and provide energy. They are broken down into smaller glucose units that can be easily absorbed by the cells. In addition, some carbohydrates serve as the framework of cellular structures. Next question

1store and provide energy 2express genetic information3provide framework of cellular structures

Question 9  Which of the following are the reasons why cellulose passes through the digestive system unchanged? Incorrect!

1It cannot be broken down into simpler monosaccharides in the body. Cellulose, a water-insoluble polysaccharide, cannot be digested by humans because the appropriate enzyme to breakdown cellulose into simpler monosaccharides is lacking. Hence, nutritionists call cellulose as dietary fiber because it just passes through the digestive system unchanged. Next question

2Its large molecular size makes it insoluble in water. 3It forms a micelle when it mixes with  water in the body.4Its helical shape is not recognized by the enzymes for digestion.

Question 10  Molecules A and B both contain carbon, hydrogen and oxygen only. Molecule A is soluble in water while Molecule B is insoluble in water.

 What are the most probable identities of A and B? Incorrect!

1 A is a protein and B is a nucleic acid. Carbohydrates and lipids both have C, H, and O atoms. However, most carbohydrates are soluble in  water while lipids are insoluble. Finish quiz

2 A is a carbohydrate and B is a lipid. 3 A is a nucleic acid and B is a carbohydrate. 4 A is a lipid and B is a protein.