• Lipids, specifically triglycerides (such as fats and oils), are
another energy source. Other lipids include structural phos-
pholipids and multi-ringed steroids derived from cholester-
ol. Steroids have structural functions and serve as chemical
messengers (hormones).
• Proteins are large molecules consisting of long chains of
amino acids bound together by peptide bonds. Amino acid
polypeptide chains twist and fold together to give a protein
its three-dimensional structure, which is essential to its func-
tion. Proteins have many functions.
• Enzymes, a class of proteins, are biological catalysts that
speed up chemical reactions.
• Nucleic acids are proteins composed of long chains of
nucleotides. Nucleic acids, including DNA and RNA, con-
tain information for building and regulating proteins. One
nucleotide, ATP, is important for storing and transferring
chemical energy in biochemical reactions.
Key Terms
• acid 32
• active site 39
• adenosine triphosphate (ATP) 42
• amino acid 36
• anabolism 31
• anion 32
• anode 27
• antioxidant 30
• atherosclerosis 30
• atom 24
• atomic number 24
• base 32
• buffer 33
• catabolism 31
• catalyst 39
• cathode 27
• cation 32
• chemical bond 26
• chemical change 22
• chemical element 23
• chemical energy 23
• chemical reaction 31
• chemistry 22
• coenzyme 39
• cofactor 39
• covalent bond 28
• decomposition 31
• dehydration synthesis 32
• denaturation 39
• deoxyribonucleic acid (DNA)
• disaccharide 35
• disulfide bond 39
• electrical energy 23
• electromagnetic spectrum 23
• electron (e-) 24
• electron level 25
• electron shell 25
• energy 22
• enzyme 39
• enzyme-substrate complex 39
• exchange 31
• fibrous protein 36
• free radical 29
• gas 22
• globular protein 36
• hydrogen bond 29
• hydrolysis 32
• hydrophilic 31
• hydrophobic 31
• inorganic compound 32
• ion 27
• ionic bond 27
• isotope 25
• kinetic energy 22
• lipid 36
• liquid 22
• mass number 24
• matter 22
• mechanical energy 23
• molecular formula 28
• molecule 28
• monosaccharide 34
• neutron (n0) 24
• nitrogenous base 41
• non-polar covalent bond 29
• non-polar molecule 29
• nucleic acid 40
• nucleus 24
• nucleotide 40
• organic compound 34
• peptide bond 38
• period 26
• periodic table of the ele-
ments 26
• pH scale 32
• phospholipid 36
• physical change 22
• polar covalent bond 29
• polar molecule 29
• polysaccharide 35
• potential energy 22
• protein 36
• proton (p+) 24
• radiant energy 23
• radioisotope 25
• reversible 31
• ribonucleic acid (RNA) 41
• salt 32
• solid 22
• solute 31
• solution 31
• solvent 31
• steroid 36
• substrate 39
• synthesis 31
• triglyceride 36
• valence shell 25
• volume 22
• water 31
41
Critical and Creative Thinking Questions
1. Some chefs “cook" raw fish filets by soaking them in lemon
juice or marinades containing lemon juice, rice vinegar, and
wine. How do these techniques produce “cooked" fish?
2. After cooking bacon in a frying pan, Susan notices that the
grease solidifies upon cooling. What can you deduce about the
triglycerides in the bacon?
3. Jim has heartburn, which is caused by excess stomach acid.
He takes a bicarbonate antacid drink to make him feel better.
Using what you have learned in this chapter about acids and
bases, explain how the antacid works.
4. In a chemistry lab, Jill stirs sucrose into water, and the sucrose
disappears. Bill heats a tablespoon of sucrose in a flame, and it
turns black, with droplets of water around the edges. Who has
actually changed the sucrose, and why?
5. Jane makes a salad dressing by mixing vegetable oil, water,
and salt. She shakes it up and lets it sit on the table. After a
while, the oil is floating on top of the water. Why do the ingre-
dients separate?
Critical and Creative Thinking Questions 45
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