Chapter 2 Chemical Basis of Life Distinguish between chemistry and biochemistry



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Chapter 2

Chemical Basis of Life


  1. Distinguish between chemistry and biochemistry.

Chemistry is the study of the composition of substances and how they change. Biochemistry is the chemistry of living organisms.

  1. Define matter.

Matter is anything that has weight and takes up space.

  1. Explain the relationship between elements and atoms.

An element is a basic substance that other things are composed from. Each individual element is made up of tiny, invisible particles called atoms. The atom is the smallest complete unit of an element.

  1. Define compound.

A compound is the product of two or more elements being combined.

  1. List the four most abundant elements in the human body.

The four most abundant elements are hydrogen, oxygen, carbon, and nitrogen.

  1. Describe the major parts of an atom.

Each atom is composed of a central portion, called a nucleus, and one or more electrons that are in constant motion around the nucleus. The nucleus contains one or more large particles called protons, and can also contain one or more similarly-sized particles called neutrons.

  1. Distinguish between protons and neutrons.

Protons carry a single, positive electrical charge (p+). Neutrons are uncharged and thus are electrically neutral (n0).

  1. Explain why a complete atom is electrically neutral.

The electron carries a single negative electric charge. The protons carry a single positive electric charge. Neutrons carry no charge, thereby making them electrically neutral. The atom is electrically neutral because there is the exact same number of protons and electrons, which effectively cancel each other out.

  1. Distinguish between atomic number and atomic weight.

Atomic number represents the number of protons in an atom of a particular element. Since atoms are electrically neutral, it also tells you the number of electrons. Atomic weight represents the number of protons plus the number of neutrons in an atom of a particular element.

  1. Define isotope.

Isotopes are elements with the same atomic number but different atomic weights.

  1. Define atomic radiation.

Atomic radiation is the energy or atomic fragments that are given off by unstable isotopes.

  1. Describe how electrons are arranged within atoms.

The electrons of an atom are found in one or more shells around the nucleus. The maximum number of electrons that each of the first three inner shells can hold is as follows:

First shell (closest to the nucleus) 2 electrons

Second shell 8 electrons

Third shell 8 electrons



  1. Explain why some atoms are chemically inert.

An atom is chemically inert when the outermost electron shells are filled. These atoms cannot form chemical bonds.

  1. Distinguish between an ionic bond and a covalent bond.

An ionic bond (electrovalent bond) is formed when atoms gain or lose electrons. A covalent bond forms when atoms share electrons.

  1. Distinguish between a single covalent bond and a double covalent bond.

A single covalent bond occurs when atoms share one pair of electrons.

A double covalent bond occurs when atoms share two pairs of electrons.



  1. Explain the relationship between molecules and compounds.

A molecule is formed when two or more atoms of the same element bond together. A compound is formed when two or more elements of different atoms combine.

  1. Distinguish between a molecular formula and a structural formula.

A molecular formula consists of the symbols of the elements in the molecule together with numbers to indicate how many atoms of each element are present. It is essentially the recipe for that particular molecule or compound. A structural formula is drawn to represent how atoms are joined and arranged in various molecules. This is essentially the blueprint of how they fit together.

  1. Describe three major types of chemical reactions.

A synthesis reaction occurs when two or more reactants bond together to make a new and more complex product. It can be symbolized as follows: A + B  AB. A decomposition reaction occurs when a more complex substance is broken apart into smaller, simple substances. It can be symbolized as follows: AB  A + B. An exchange reaction occurs when parts of two molecules change positions. It can be symbolized as follows: AB + CD  AD + CB.

  1. Explain what is meant by reversible reaction.

A reversible reaction is one in which the end product (or products) of the reaction can changed back to the reactant (or reactants) that originally underwent the reaction A + B  AB.

  1. Define catalyst.

A catalyst is a particular atom or molecule that can change the rate of a reaction without being consumed or changed by the reaction.

  1. Define acid, base, salt, and electrolyte.

An electrolyte is a substance that releases ions in water. An acid is an electrolyte that releases hydrogen ions (H+) in water. A base is an electrolyte that releases ions that can combine with hydrogen ions. These are usually hydroxyl ions (OH-). A salt is the product formed by the reactions of acids and bases.

  1. Explain what pH measures.

pH measures the concentration of hydrogen ions found in substances.

  1. Distinguish between organic and inorganic substances.

An organic substance contains both carbon and hydrogen atoms. An inorganic substance lacks carbon atoms.

  1. Describe the roles played by water and by oxygen in the human body.

Water is the most abundant substance in the human body. It is a major component of blood and other body fluids. It is an important solvent. It also has an important role in the transportation of chemicals in the body. Additionally, water can absorb and transport heat. Oxygen is used by cellular organelles in the process of releasing energy from glucose and certain other molecules. The resultant energy is used to drive the cell’s metabolic activities.

  1. List several ions that cells require, and describe their general functions.

Sodium (Na+), chlorine (Cl-), potassium (K+), calcium (Ca+), magnesium (Mg+2), phosphate (PO4-3), carbonate (CO3-2), bicarbonate (HCO3-), and sulfate (SO4-2) are the ions that play important roles in metabolic processes. These processes include maintenance of proper water concentrations and nerve functions, in body fluids, pH, blood clotting, bone development, energy transfer within cells, and muscle function.

  1. Define electrolyte balance.

Electrolyte balance is the condition where the electrolytes are present in certain concentrations, both inside and outside cells, to maintain homeostasis.

  1. Describe the general characteristics of carbohydrates.

Carbohydrates supply much of the energy for the cells. They supply building materials for certain cell structures and are often stored as reserve energy. These molecules contain atoms of carbon, hydrogen, and oxygen. Carbohydrates usually have twice as many hydrogen as oxygen atoms. The carbon atoms are joined in chains that vary in length with the specific kinds of carbohydrates.

  1. Distinguish between simple and complex carbohydrates.

Simple carbohydrates are the six-carbon sugars known as simple sugars. Complex carbohydrates are formed when a number of simple sugar molecules are bound together to form molecules of varying size.

  1. Describe the general characteristics of lipids.

Lipids are organic substances that are insoluble in water but soluble in certain organic solvents. They supply more energy, gram for gram, than carbohydrates. They contain carbon, hydrogen, and oxygen. Lipids contain a much smaller proportion of oxygen than carbohydrates.

  1. Distinguish between saturated and unsaturated fats.

A saturated fat contains no double bonds between carbon atoms. An unsaturated fat contains one or more double bonds between carbon atoms.

  1. Describe the general characteristics of proteins.

Proteins can be used as structural materials, energy sources, hormones, and receptors on cell surfaces that are specialized to bond to particular kinds of molecules. Others act as antibodies against foreign substances that can enter the body. Still others act as enzymes in metabolic processes. Proteins contain atoms of carbon, hydrogen, and oxygen. In addition, they always contain nitrogen atoms, and sometimes contain sulfur atoms as well.

  1. Describe the function of an enzyme.

An enzyme is a molecule that acts as a catalyst in living systems. That is, it speeds specific chemical reactions without being consumed or changed in the process.

  1. Explain how protein molecules may become denatured.

When protein molecules lose their unique shape and become disorganized, they become denatured. This can be a result of exposure to excessive heat, radiation, electricity, or various chemicals. When they become denatured, it is a permanent change and they are therefore nonfunctional.

  1. Describe the general characteristics of nucleic acids.

Nucleic acid molecules are generally very large and complex. They contain atoms of carbon, hydrogen, oxygen, nitrogen, and phosphorus. These are bound into building blocks called nucleotides.

  1. Explain the general functions of nucleic acids.

These control all cell activities. They store information that is used by cell parts to construct specific kinds of protein molecules, including enzymes.
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