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Chemistry of Life
Chapter section 2.3
As you read through your text, please complete this chapter guide by typing into the
document after each question. Note: I do not collect Chapter Guides. These are to
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Biological Molecules
What is a macromolecule? It’s a large molecule.
What are the 4 categories of macromolecules? carbohydrates, lipids, proteins, and
nucleic acids
“Organic” in biology and chemistry means something different that “organic” at the
grocery store. What do we mean by “organic” when we are describing a molecule?
Contain carbon
What elements (or, kinds of atoms) are in a carbohydrate? Carbon, hydrogen, oxygen.
What is the ratio for these elements? 1:2:1 (carbon : hydrogen : oxygen)
What is the molecular formula for a carbohydrate? CH2O
What is a monosaccharide? a disaccharide? Give one example for each.
Monosaccharide is unit of carbohydrate( ex. glucose ). Disaccharide is a substance
consisting of two monosaccharide ( ex. Lactose).
Both starch and cellulose are polysaccharides made by plants. Why is it that we can
digest starch but not cellulose? The starch that is consumed by animals is broken down
into smaller molecules, but we don’t have the appropriate enzymes to digest cellulose.
Glucose-glucose bonds in cellulose cannot be broken down by human digestive
What elements (or, kinds of atoms) are in a lipid? Carbon, Hydrogen, Oxygen
What does “hydrophobic” mean? Why are lipids hydrophobic? Hydrophobic means an
incompatibility with water. Because lipids are nonpolar.
What is a hydrocarbon? Organic compound consisting carbon and hydrogen.
Carbon has four electrons in its outer shell, which means it can form four covalent
bonds. If there are only single bonds, how many atoms are covalently bonded to the
carbon atom? Four
If there is a double bond, how many how many atoms are covalently bonded to the
carbon atom? Two
What is a saturated fat? Give an example. Type of a fat, the fatty acid chains have single
bonds. (ex. Butter)
What is an unsaturated fat? Give an example. Type of a fat, the fatty acid chain have
double bond. (ex. Vegetable oils)
What is a trans-fat? How is it made? Why aren’t trans-fats good for you?
Fat produced by the process of adding hydrogen to process unsaturated fats in liquid
states into solid states. Trans-fats raise bad cholesterol levels and lower good
cholesterol levels.
What kind of lipid is cholesterol? How is cholesterol used by our cells?
Cholesterol is kind of glycolipid. It’s essential for cell because it is used to make and
maintain all cell membranes, and it’s a component of bile.
What are some functions of proteins in our bodies?
It’s functions are diverse, they can work for enzymes or hormones.
A monomer of a carbohydrate is a simple sugar (monosaccharide). What is a monomer
of a protein? How many different kinds are there?
Amino acids are monomer of a protein, and there are 20 kinds of amino acids.
What is an “R-group”?
R-group is difference between 20 amino acids .
How is a polypeptide different than a protein? (hint- look at figure 2.21)
Proteins contain polypeptides.
What causes proteins to have their specific shape? (again, look at figure 2.21)
They have their specific shaped by chemical interactions.
What does it mean if we say a protein has been “denatured”? How could denaturation
happen? What does denaturing do to the ability of a protein to function?
Denatured means protein structures are changed by some reasons ( temperature, PH,
chemical reasons).
Nucleic Acids
What are the two main types of nucleic acids and what are their general functions?
The two main types of nucleic acids are DNA and RNA. DNA(deoxyribonucleic acid) is
genetic material found in organisms. RNA(ribonucleic acid) is most involved protein
What is the monomer of a nucleic acid? And what are the three components of each
Monomer of a nucleic acid is nucleotide, made up of three components ( a nitrogenous
base, a pentose sugar, a phosphate group )
We will look at nucleic acids in more detail in a future chapter. For now, just familiarize
yourself with the basic structure of DNA.
A DNA molecule is a double helix. You can picture it as a rope ladder that has twisted.
Using this analogy, what parts of the molecules make up the rungs of the ladder?
The nitrogenous base make up the rung of the ladder.
What parts make up the sides of the ladder?
The alternating sugar and phosphate groups are forming the sides of the ladder.
How are the two sides of the ladder held together?
They are combined in a hydrogen bond.
Photo Credit
Title image: Argonne's Midwest Center for Structural Genomics