# Critical Thinking Questions

39.
The word hydrolysis is defined as the lysis of water. How does this apply to polymers?
1. Polymers break by separating water into hydrogen and hydroxyl group that are added to the monomers.
2. Polymers are synthesized by using the energy released by the breaking of water molecules into hydrogen and hydroxyl group.
3. Polymers are separated into monomers producing energy and water molecules.
4. Polymers are hydrolyzed into monomers using water in the process and are called as dehydration synthesis.
40.
What role do electrons play in dehydration synthesis and hydrolysis?
1. Electrons are added to $OH$ and $H$ ion in the dehydration synthesis. They are removed from $OH$ and $H$ in hydrolysis.
2. Electrons are transferred from $OH$ and $H$ ions to the monomers in dehydration synthesis. They are taken up by the $H$ and $OH$ ions from the monomers in hydrolysis.
3. Electrons are removed from $OH$ and $H$ in the dehydration synthesis. They are added to $OH$ and $H$ in hydrolysis.
4. Electrons are transferred from monomers to $H$ and $OH$ ions in hydrolysis and from $OH$ and $H$ to monomers in dehydration synthesis.
41.
Which of the following bodily process would most likely be hindered by a lack of water in the body?
1. digestion
2. protein synthesis
3. DNA copying
4. respiration
42.

Why is it impossible for humans to digest food that contains cellulose?

1. There is no energy available in fiber.
2. An inactive form of cellulase in the human digestive tract renders it undigested and removes it as waste.
3. The acidic environment in the human stomach makes it impossible to break the bonds in cellulose.
4. Human digestive enzymes cannot break down the β -1,4 glycosidic linkage in cellulose, which requires a special enzyme that is absent in humans.
43.
Which statement describes some of the differences between cellulose and starch?
1. Cellulose is unbranched, and starch is branched. Both molecules are found in animals.
2. Starch is unbranched, and cellulose is branched. Both molecules are found in plants.
3. Starch is branched, and cellulose is unbranched. Both molecules are found in plants.
4. Cellulose is branched, and starch is unbranched. Both molecules are found in animals.
44.
Which of these best describes the production of sucrose, maltose, and lactose?
1. Glucose and fructose combine to form sucrose. Glucose and galactose combine to form lactose. Two glucose monomers combine to form maltose.
2. Glucose and fructose combine to form sucrose. Glucose and galactose combine to form maltose. Two glucose combine to form lactose.
3. Two glucose combine to form lactose. Glucose and galactose combine to form sucrose. Glucose and fructose combine to form maltose.
4. Two galactose combine to form sucrose. Fructose and glucose combine to form lactose. Two glucose combine to form maltose.
45.

What are the four classes of lipids? Provide a common example for each one.

1. Fats like margarine, waxes like the coating on feathers, phospholipids like cell membrane constituents, steroids like cholesterol
2. Fats like phosphatidylserine, waxes like phosphatidic acid, phospholipids like oleic acid, steroids like epinephrine
3. Fats like phosphatidic acid, waxes like margarine, phospholipids like phosphatidylcholine, steroids like testosterone
4. Fats like cholesterol, waxes like the coating on feathers, phospholipids like phosphatidylserine, steroids like margarine
46.
What are three functions that lipids serve in plants and/or animals?
1. Lipids serve in the storage of energy, as a structural component of hormones, and also as signaling molecules.
2. Lipids serve in the storage of energy, as carriers for the transport of proteins across the membrane, and as signaling molecules.
3. Lipids serve in the breakdown of stored energy molecules, as signaling molecules, and as structural components of hormones.
4. Lipids serve in the breakdown of stored energy molecules, as signaling molecules, and as channels for protein transport.
47.

How are trans fats created? Why have they been banned from some restaurants?

1. Trans fat is produced by the hydrogenation of oil that makes it more saturated and isomerized. It increases the LDL in the body.
2. The dehydrogenation of oil forms the trans fat, which contains single bonds in its structure. This increases the HDL in the body and has been banned.
3. Trans fat is produced by dehydrogenation of oils, which makes it unsaturated. It increases the LDL in the body.
4. The hydrogenation of oil makes the trans fat, which contains double bonds in its structure. It decreases the HDL in the body.
48.

How do phospholipids contribute to cell membrane structure?

1. Phospholipids orient their heads toward the polar molecules and tails in the interior of the membrane, thus forming a bilayer.
2. Phospholipids orient their tails toward the polar molecules of water solutions, and heads in the interior of the membrane, thus forming a bilayer.
3. Phospholipids orient their heads toward the nonpolar molecules and tails in the interior of the membrane, forming a bilayer.
4. Phospholipids orient their tails toward the polar molecules and heads in the nonpolar side of the membrane, forming a bilayer.
49.

What type of compound functions in hormone production, contributes to membrane flexibility, and is the starting molecule for bile salts?

1. All steroid molecules help in the mentioned functions.
2. Cholesterol, which is a lipid and also a steroid, functions here.
3. Glycogen, which is a multi-branched polysaccharide of glucose, is the compound.
4. Phosphatidylcholine, which is a phospholipid with a choline head group, serves the functions.
50.
What part of cell membranes gives flexibility to the structure?
1. carbohydrates
2. cytoskeleton filaments
3. lipids
4. proteins
51.
How do the differences in amino acid sequences lead to different protein functions?
1. Different amino acids produce different proteins because of the secondary bonds they form.
2. Differences in amino acids lead to the recycling of proteins, which produces other functional proteins.
3. Different amino acids cause rearrangements of amino acids to produce a functional protein.
4. Differences in the amino acids cause post-translational modification of the protein, which reassembles to produce a functional protein.
52.
What causes the changes in protein structure through the three or four levels of structure?
1. The primary chain forms secondary α-helix and β-pleated sheets which fold onto each other forming the tertiary structure.
2. The primary structure undergoes alternative splicing to form secondary structures, which fold on other protein chains to form tertiary structures.
3. The primary structure forms secondary α-helix and β-pleated sheets. This further undergoes phosphorylation and acetylation to form the tertiary structure.
4. The primary structure undergoes alternative splicing to form a secondary structure, and then disulfide bonds give way to tertiary structures.
53.

What structural level of proteins is functional? Why?

1. The secondary structure is functional as it attains its two-dimensional shape, which has the necessary bonds.
2. The tertiary structure is functional, as it possesses the geometric shape showing the necessary loops and bends.
3. The tertiary structure is functional as it has the non-covalent and covalent bonds along with the subunits attached at the right places, which help it function properly.
4. Quaternary structure is functional, as it has the essential set of subunits.
54.
How does a chaperone work with proteins?
1. Chaperones assist proteins in folding.
2. Chaperones cause the aggregation of polypeptides.
3. Chaperones associate with proteins once the target protein is folded.
4. Chaperones escort proteins during translation.
55.
What is a difference between DNA and RNA?
1. DNA is made from nucleotides; RNA is not.
2. DNA contains deoxyribose and thymine while RNA contains ribose and uracil.
3. DNA contains adenine, while RNA contains guanine.
4. DNA is double stranded, while RNA may be double stranded in animals.
56.
Which molecule carries information in a form that is inherited from one generation to another?
1. DNA
2. mRNA
3. Proteins
4. tRNA
57.
What are the four types and functions of RNA?
1. mRNA is a single stranded transcript of DNA. rRNA is found in ribosomes. tRNA transfers specific amino acids to a growing protein strand. miRNA regulates the expression of mRNA strands.
2. mRNA is a single stranded transcript of rRNA. rRNA is translated in ribosomes to make proteins. tRNA transfers specific amino acids to a growing protein strand. microRNA (miRNA) regulates the expression of the mRNA strand.
3. mRNA regulates the expression of the miRNA strand. rRNA is found in ribosomes. tRNA transfers specific amino acids to a growing protein strand. miRNA is a single stranded transcript of DNA.
4. mRNA is a single stranded transcript of DNA. rRNA transfers specific amino acids to a growing protein strand. tRNA is found in ribosomes. miRNA regulates the expression of the mRNA strand.