4. Biomolecules

Carbohydrates

A team led by evolutionary biologist Hopi Hoekstra set out to test the hypothesis that predators are an agent of natural selection on mouse color. They made 250 plasticine models of mice that were alike in every way except that half were painted white and half were painted brown. Suggest one advantage and one disadvantage of using model mice instead of real mice in this experiment.

Which of the following categories includes all others in the list?
a. disaccharide
b. polysaccharide
c. starch
d. carbohydrate

Formation & Breakdown of Polysaccharides

 No. Glycogen is a glucose storage polymer found in animals. 

 No. Cellulose is not digestible by plants, so cellulose cannot be an energy source. 

 No. Protein is a polypeptide, not a polysaccharide. 

Think potato.

In what polysaccharide form do plants store glucose to be available later as an energy source?

Biomolecules: The Carbohydrates

Animation: Synthesis of Sucrose

Animation: Starch, Cellulose, and Glycogen Structures

 No. Collagen is a structural protein found in tendons and ligaments (among other places). 

 No. Cellulose is a structural polysaccharide found in plant cell walls. 

 No. Palmitic acid is a saturated fatty acid. 

 No. In animals, glycogen is a glucose storage form of polysaccharide. 

What carbohydrate forms the hard exoskeleton of an insect?

At a conference, the speaker's grand finale was saut&eacute;ing mealworms (insect larvae) in butter and serving them to the audience. They were crunchy (like popcorn hulls) because their exoskeletons contain the polysaccharide __________.

True or false? Some traits are considered vestigial because they existed long ago.

 No. Sucrose, lactose, and maltose are not polysaccharides. A polysaccharide is composed of many monosaccharide building blocks. 

 No. Sucrose, lactose, and maltose are not monosaccharides. A monosaccharide is a simple sugar containing three to seven carbons. 

 No. Of these three sugars, only sucrose contains a fructose monomer. 

 No. Sucrose, lactose, and maltose are digestible by humans. 

Consider the number of monosaccharide subunits in each of these three carbohydrates.

One characteristic shared by sucrose, lactose, and maltose is that __________.

Why don’t the biggest and strongest individuals in a population always produce the most offspring?
a. The biggest and strongest individuals always have higher fitness.
b. In some environments, being big and strong lowers fitness.
c. Sometimes the biggest and strongest individuals may choose to have fewer offspring.
d. Sometimes the number of offspring is not related to fitness.

C51H98O6

 No. Consider the C:H:O ratio present in a monosaccharide. 

C45H84O8PN

 No. Monosaccharides do not generally contain phosphorus or nitrogen. Also, consider the C:H:O ratio present in a monosaccharide. 

C25H43O8

C22H49O10N5

 No. Monosaccharides do not generally contain nitrogen. Also, consider the C:H:O ratio present in a monosaccharide. 

C6H12O6

Consider the meaning of carbo- and -hydrate.

Which of the following molecules is a monosaccharide?

Which polysaccharide is an important component in the structure of lobsters and insects?a) Chitin.b) Cellulose.c) Starch.d) Glycogen.e) Polypeptides.

 No. This is a polysaccharide found in arthropod exoskeletons. 

The polysaccharide that you are most likely to have eaten recently is __________.

Animation: Monosaccharides

Monosaccharides are linked together via a ______________ reaction, forming a _____________bond.a) Hydrolysis ; Glycosidic.b) Dehydration synthesis ; Hydrogen.c) Hydrolysis ; Peptide.d) Dehydration synthesis ; Glycosidic.e) Hydrolysis ; Hydrogen.

 The enzyme cannot attack cellulose because of its helical shape. 

 No. Cellulose is straight; starch is helical. 

 Cellulose molecules are much too large. 

 No. Because amylase sequentially removes a disaccharide from one end of its substrate, it does not matter how large the molecule is. 

 Starch is made of glucose; cellulose is made of fructose. 

 No. Both cellulose and starch are made from glucose monomers. 

 The bonds between the monosaccharide monomers in cellulose are much stronger. 

 No. Bond strength is related to the bonded atoms, which for both molecules are carbon-to-oxygen glycosidic linkages. 

 The monosaccharide monomers in cellulose are bonded together differently than those in starch. 

Consider how starch differs from cellulose structurally.

Amylase is an enzyme that breaks down starch. Why can the same enzyme not break down cellulose?

Evaluate this statement: Evolution is said to occur when new traits accumulate over time, increasing complexity.

Animation: Carbohydrates

Some biologists summarize evolution by natural selection with the phrase “mutation proposes, selection disposes.” Mutation is a process that creates heritable variation. Explain what the phrase means.

In humans, albinism is caused by loss-of-function mutations in genes involved in the synthesis of melanin, the dark pigment in skin. Only people homozygous for a loss-of-function allele (genotype aa) have the albino phenotype. In Americans of northern European ancestry, albino individuals are present at a frequency of about 1 in 10,000 (or 0.0001). Assuming that genotypes are in Hardy–Weinberg equilibrium, what is the predicted frequency of Caucasians in the United States who carry a single allele for albinism?

The researchers placed white and brown mouse models both in abandoned fields on the mainland (dark soil) and on sand dunes on the islands (light soil) and then measured the percentage of models that were attacked by predators. What is the take-home message of the data? Do the data support or reject the hypothesis that mouse color is adaptive? <IMAGE>

Macromolecule Review

 No. Carbohydrate monomers are not ions. 

 No. Nucleotides are joined together by phosphodiester linkages. 

 No. Fatty acids are joined to glycerol by ester linkages. 

Consider the type of bond that joins monosaccharides together as a result of a dehydration reaction.

The subunits (monomers) in cellulose are linked together by __________.

Animal cells store energy in the form of _________, and plant cells store energy in the form of ___________.a) Sucrose ; glucose.b) Disaccharides ; monosaccharides.c) Starch ; glycogen.d) Cellulose ; chitin.e) Glycogen ; starch.

How can evolutionary fitness be measured? Select True or False for each statement.
T/F Document how long individuals survive.
T/F Count the number of healthy, fertile offspring produced.
T/F Determine which individuals are strongest.
T/F Determine which phenotype is the most common.

 No. That would not make cellulose any more digestible. 

 Cows and other herbivores are exceptions and make some cellulose-digesting enzymes. 

 No. Cows cannot digest cellulose without the help of their microorganismal flora because they cannot produce an enzyme to hydrolyze the specific beta (&#946;) glycosidic linkages present in the cellulose polymer. 

 The flat teeth and strong stomach of herbivores break the cellulose fibers so that the cows get enough nutrition from the cell contents. 

 No. There would not be enough nutrients provided in this manner. 

 All of the listed responses are correct. 

 No. Only one of the choices is correct. 

 Microorganisms in their digestive tracts hydrolyze the cellulose to individual glucose units. 

Think about the constituents of a cow's digestive tract.

Generally, animals cannot digest (hydrolyze) the glycosidic linkages between the glucose molecules in cellulose. How then do cows get enough nutrients from eating grass?

Which of the following chemical reactions results in energy release when glycosidic bonds are broken?a) Condensation reaction.b) Dehydration synthesis reaction.c) Hydrolysis reaction.d) Hydrogen bonding.

Carbohydrates | Biological Molecules Simplified #1

Carbohydrate Functions

#1 A Level Biology - Biological Molecules

 No. Cellulose is an example of a structural polysaccharide, but there is a better answer. 

 No. Plants store energy in the form of starch, but there is a better answer. 

 No. Nucleic acids function in energy storage. 

 No. Most enzymatic catalysts are proteins. 

Refer to the different functions of carbohydrates in plant and animal cells. .

Carbohydrates can function in which of the following ways?

Most mice living on the mainland of Florida are brown, but the mice that live on the sand dunes of the barrier islands have white fur. The differences in color are heritable, determined by genes such as MC1R. It is intuitive that the light color of beach-dwelling mice is an adaptation for blending into their environment—and thus evading predators.

What is an evolutionary adaptation?

a. a trait that improves the fitness of its bearer, compared with individuals without the trait

b. a trait that changes in response to environmental influences within the individual’s lifetime

c. the ability of an individual to adjust to its environment

d. a trait that an individual wants so that it can survive

Explain why the overprescription of antibiotics by doctors, or the overuse of everyday soaps containing antibiotics, can be a health risk.

The enzyme amylase can break glycosidic linkages between glucose monomers only if the monomers are in the α
 form. Which of the following could amylase break down?
a. glycogen, starch, and amylopectin
b. glycogen and cellulose
c. cellulose and chitin
d. starch, chitin, and cellulose

 No. Glucose is a monosaccharide, not a polysaccharide. 

 No. Chitin is not found in humans. Chitin is a structural polysaccharide found in the exoskeleton of arthropods. 

 No. Cellulose is a polysaccharide present in plant cell walls. 

Consider which of these is a polysaccharide found in humans and other animals.

A polysaccharide that is used for storing energy in human muscle and liver cells is __________.

3 Size Classes of Carbohydrates

Properties of Biological Macromolecules | AP Biology 1.4

 No. Sugars will be digested and absorbed. 

 No. Oils will be digested and absorbed. 

 No. Most proteins are completely digestible. 

Consider the enzymes available in the human digestive system.

Which of the following components of a tossed salad will pass through the human digestive tract and be digested the least?

 No. Membranes are composed primarily of lipids. 

 structural molecules, such as hair and fingernails 

 No. These are composed primarily of protein. 

 No. Genetic material is composed of nucleic acids, and enzymatic proteins catalyze its construction. 

 No. Although carbohydrates can be converted to lipids, carbohydrates and lipids are two different categories of the four major kinds of macromolecules found in living systems. 

Why are carbohydrates one of the major ingredients in sports drinks?

Carbohydrates are used in our bodies mainly for __________.

C6H12O6.

Which of the following chemical formulas represents that of a simple carbohydrate?a) C2H2O2.b) C6H12O6.c) C5H4O3.d) C3H6O9.

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