Assignment: Building Blocks of Molecules

Assignment: Building Blocks of Molecules

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Matter is anything that occupies space and has mass. It is made up of atoms of different elements. All the 92 elements that occur naturally have unique qualities that allow them to combine in various ways to create compounds or molecules. Atoms, which consist of protons, neutrons, and electrons, are the smallest units of an element that retain all the properties of that element. Electrons can be donated or shared between atoms to create bonds, including ionic, covalent, and hydrogen bonds, as well as van der Waals interactions. Assignment: Building Blocks of Molecules

Water 

Water has many properties that are critical to maintaining life. It is polar, allowing for the formation of hydrogen bonds, which allow ions and other polar molecules to dissolve in water. Therefore, water is an excellent solvent. The hydrogen bonds between water molecules give water the ability to hold heat better than many other substances. As the temperature rises, the hydrogen bonds between water continually break and reform, allowing for the overall temperature to remain stable, although increased energy is added to the system. Water’s cohesive forces allow for the property of surface tension. All these unique properties of water are important in the chemistry of living organisms.

The pH of a solution is a measure of the concentration of hydrogen ions in the solution. A solution with a high number of hydrogen ions is acidic and has a low pH value. A solution with a high number of hydroxide ions is basic and has a high pH value. The pH scale ranges from 0 to 14, with a pH of 7 being neutral. Buffers are solutions that moderate pH changes when an acid or base is added to the buffer system. Buffers are important in biological systems because of their ability to maintain constant pH conditions.

Biological Molecules 

Living things are carbon-based because carbon plays such a prominent role in the chemistry of living things. The four covalent bonding positions of the carbon atom can give rise to a wide diversity of compounds with many functions, accounting for the importance of carbon in living things. Carbohydrates are a group of macromolecules that are a vital energy source for the cell, provide structural support to many organisms, and can be found on the surface of the cell as receptors or for cell recognition. Carbohydrates are classified as monosaccharides, disaccharides, and polysaccharides, depending on the number of monomers in the molecule.

Lipids are a class of macromolecules that are nonpolar and hydrophobic in nature. Major types include fats and oils, waxes, phospholipids, and steroids. Fats and oils are a stored form of energy and can include triglycerides. Fats and oils are usually made up of fatty acids and glycerol.

Proteins are a class of macromolecules that can perform a diverse range of functions for the cell.

They help in metabolism by providing structural support and by acting as enzymes, carriers, or as hormones. The building blocks of proteins are amino acids. Proteins are organized at four levels: primary, secondary, tertiary, and quaternary. Protein shape and function are intricately linked; any change in shape caused by changes in temperature, pH, or chemical exposure may lead to protein denaturation and a loss of function.

Nucleic acids are molecules made up of repeating units of nucleotides that direct cellular activities such as cell division and protein synthesis. Each nucleotide is made up of a pentose sugar, a nitrogenous base, and a phosphate group. There are two types of nucleic acids: DNA and RNA.

Art Connection Question

1.  Figure 3 How many neutrons do (K) potassium-39 and potassium-40 have, respectively?

Review Questions

1.  Magnesium has an atomic number of 12. Which of the following statements is true of a neutral magnesium atom?

a. It has 12 protons, 12 electrons, and 12 neutrons.

b.  It has 12 protons, 12 electrons, and six neutrons.

c. It has six protons, six electrons, and no neutrons.

d. It has six protons, six electrons, and six neutrons.

2.  Which type of bond represents a weak chemical bond?

a. hydrogen bond

b. ionic bond

c. covalent bond

d. polar covalent bond

3.  An isotope of sodium (Na) has a mass number of 22. How many neutrons does it have?

a. 11

b. 12

c. 22

d. 44

4.  Which of the following statements is not true?

a. Water is polar.

b.  Water stabilizes temperature.

c.. Water is essential for life.

d. Water is the most abundant atom in Earth’s atmosphere.

5.  Using a pH meter, you find the pH of an unknown solution to be 8.0. How would you describe this solution?

a. weakly acidic

b. strongly acidic

c. weakly basic

d. strongly basic

6.  The pH of lemon juice is about 2.0; tomato juice’s pH is about 4.0. Approximately how much of an increase in hydrogen ion concentration is there between tomato juice and lemon juice?

a. 2 times

b. 10 times

c. 100 times

d. 1000 times

7.  An example of a monosaccharide is

a. fructose

b. glucose

c. galactose

d. all of the above

8.  Cellulose and starch are examples of

a. monosaccharides

b. disaccharides

c. lipids

d. polysaccharides

9.      Phospholipids are important components of

a. the plasma membrane of cells

b. the ring structure of steroids

c. the waxy covering on leaves

d. the double bond in hydrocarbon chains

10.  The monomers that make up proteins are called     .

a. nucleotides

b. disaccharides

c. amino acids