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Molecules of Life
Molecules of Life
Section 2 Molecules of LifeChapter 3
Carbohydrates• Carbohydrates are organic compounds composed
of carbon, hydrogen, and oxygen in a ratio of about one carbon to two hydrogen atoms to one oxygen atom.
• Carbohydrates are a source of energy and are used as structural materials in organisms.
Section 2 Molecules of LifeChapter 3
• Monosaccharides – Carbohydrates are made up of monomers
called monosaccharides. • Disaccharides and Polysaccharides
– Two monosaccharides join to form a double sugar called a disaccharide.
– A complex sugar, or polysaccharide, is made of three or more monosaccharides.
Carbohydrates
Section 2 Molecules of LifeChapter 3
• Proteins are organic compounds composed mainly of carbon, hydrogen, oxygen, and nitrogen.
• Proteins have many functions including structural, defensive, and catalytic roles.
Proteins
Section 2 Molecules of LifeChapter 3
• Amino Acids– Proteins are made up of monomers called
amino acids. The sequence of amino acids determines a protein’s shape and function.
• Dipeptides and Polypeptides– Two amino acids are joined by peptide bonds
to form a dipeptide.– A long chain of amino acids is called a
polypeptide.
Proteins
Chapter 3Structure of Proteins
Section 2 Molecules of Life
Section 2 Molecules of LifeChapter 3
• Enzymes– Enzymes speed up chemical reactions and bind
to specific substrates. – The binding of a substrate with an enzyme
causes a change in the enzyme’s shape and reduces the activation energy of the reaction.
Proteins
Chapter 3Enzyme Activity
Section 2 Molecules of Life
Section 2 Molecules of LifeChapter 3
• Lipids are nonpolar molecules that store energy and are an important part of cell membranes.
Lipids
Section 2 Molecules of LifeChapter 3
• Fatty Acids– Most lipids contain fatty acids, unbranched
carbon molecules that have a hydrophilic end and a hydrophobic end.
• Triglycerides– Triglycerides consist of three fatty acids and
one molecule of glycerol.
Lipids
Section 2 Molecules of LifeChapter 3
• Phospholipids– Phospholipids, which make up cell membranes,
consist of two fatty acids and one glycerol molecule.
• Waxes– A wax is made of one long fatty acid chain joined to
one long alcohol.
• Steroids– A steroid is composed of four fused carbon rings.
Lipids
Section 2 Molecules of LifeChapter 3
• A nucleic acid is a large and complex organic molecule that stores and transports information.
• The nucleic acid deoxyribonucleic acid (DNA) contains genetic information for cell activities.
• Ribonucleic acid (RNA) molecules play many key roles in building of proteins and can act as enzymes.
Nucleic Acids
Chapter 3Structure of Nucleic Acids
Section 2 Molecules of Life
Multiple Choice
1. Which of the following is not a function of polysaccharides?
A. energy source
B. energy storage
C. structural support
D. storage of genetic information
Standardized Test PrepChapter 3
Multiple Choice, continued
2. Which of the following statements is false?
A. A wax is a lipid.
B. Starch is a lipid.
C. Saturated fats are solid at room temperature.
D. Unsaturated fats are liquid at room temperature.
Standardized Test PrepChapter 3
Multiple Choice, continued
3. Which of the following molecules stores hereditary information?
A. ATP
B. DNA
C. protein
D. carbohydrates
Standardized Test PrepChapter 3
Multiple Choice, continued
4. What is the name of the molecule in plants that stores sugars?
A. starch
B. protein
C. cellulose
D. glycogen
Standardized Test PrepChapter 3
Multiple Choice, continued
5. Which of the following molecules make up the basic structure of a cell membrane?A. waxesB. steroidsC. fatty acidsD. phospholipids
Chapter 3
The figure below illustratesthe basic structure of a cell membrane. Use thefigure to answer the questions that follow.
Standardized Test Prep
Multiple Choice, continued
6. The “tails” of the molecules in the figure orient away from water. Which of the following describes the tail’s movement away from water?A. polarB. adhesiveC. hydrophilicD. hydrophobic
Chapter 3
The figure below illustratesthe basic structure of a cell membrane. Use thefigure to answer the questions that follow.
Standardized Test Prep
Multiple Choice, continued
7. simple sugars : carbohydrates :: amino acids :A. lipids
B. proteinsC. nucleic acidsD. amino acids
Chapter 3 Standardized Test Prep
Multiple Choice, continued
8. What is the name of the functional group circled in the structural formula?A. aminoB. hydroxylC. phosphateD. carboxyl
Chapter 3
The figure below representsthe structural formula of a molecule. Use thefigure to answer the question that follows.
Standardized Test Prep
