Biology Chapter 3 MSU

How many possible types of bases are there in a DNA molecule?

4 There are 4 different possible nitrogenous bases in DNA: A, C, T, and G.

___________ is the most important monosaccharide for living organisms.

Glucose Glucose is the most important simple sugar for fueling living organisms' cells.

In DNA, guanine from one strand binds to ______ in the complementary strand

cytosine (G connects to C)

Which of the following is not a function of proteins? provide the structure of hair and fingernails help fight invading microorganisms in the body control cell activity in the body transport molecules, such as oxygen, around the body form the membrane that surrounds the contents of cells

form the membrane that surrounds the contents of cells Phospholipids form the bilayer that surrounds the contents of cells.

The unique part of the structure of an amino acid is:

its side chain. The side chain is the unique part of each amino acid and determines the amino acid's chemical properties.

Unlike humans, termites are able to extract energy from wood because:

they have some microorganisms living in their gut that are able to break down cellulose. It is the microorganisms that live in the termite's gut that produce cellulose-degrading enzymes.

If a DNA molecule consists of 20% adenine, what percent is cytosine?

30% DNA contains equal proportions of adenine and thymine (which pair together) and equal proportions of cytosine and guanine (which pair together). If a particular molecule of DNA contains 20% adenine, that implies another 20% is thymine, and the remaining 60% would be evenly split between cytosine and guanine.

A carbohydrate molecule is discovered that contains 28 carbon atoms. Based on what you know about the chemical composition of carbohydrates, this molecule likely will have ____ hydrogen atoms and ____ oxygen atoms.

56, 28 Although there are exceptions, carbohydrates typically contain the same number of carbon atoms as they do H2O units. Therefore, a molecule containing 28 carbon atoms likely would have 56 hydrogen atoms and 28 oxygen atoms.

Which of the following statements is false? All fats are lipids. Conversely, all lipids are also fats. All fats are lipids, but not all lipids are fats. Lipids do not have subunit structures, such as the subunits that make up carbohydrates. They are identified based on physical characteristics. Lipids have three functions: long-term energy storage and insulation, membrane formation, and composition of hormones. Sterols primarily function to regulate growth and development.

All fats are lipids. Conversely, all lipids are also fats. Fats belong to the lipid class, but some lipids—namely, sterols and phospholipids—are not fats.

Which of the following statements about enzymes is false? Enzymes are proteins. Without enzymes, many biochemical reactions would not occur fast enough to support life. An enzyme catalyzes a chemical reaction by amplifying the energy of activation. The shape of the enzyme creates an active site that binds to one or more specific substrates. The presence of activators or inhibitors can alter the rate at which an enzyme catalyzes a reaction.

An enzyme catalyzes a chemical reaction by amplifying the energy of activation. Enzymes act as catalysts by lowering the activation energy.

True or False: Water (H2O) is an organic molecule. Please choose the correct answer from the following choices, and then select the submit answer button.

False. Organic molecules always contain carbon. Water is not considered an organic molecule because it does not contain carbon.

Which of the following statements is false? a. DNA requires a "middle man," RNA, to direct protein synthesis. b. The codons that result in a specific amino acid are based upon RNA bases, not DNA bases. c. The sugar molecule in the RNA backbone contains an extra atom of oxygen. d. In addition to thymine, RNA contains a unique base called uracil. e. DNA is double-stranded, whereas RNA is single-stranded.

In addition to thymine, RNA contains a unique base called uracil. RNA does not contain thymine; it contains uracil instead of thymine.

Which of the following is not a fate of glucose circulating in the blood of a healthy individual?

It can remain, circulating in the blood indefinitely. Glycogen will not just circulate indefinitely. Depending upon whether energy is needed, glucose can be broken down for immediate use by cells or stored on a short- or long-term basis.

______________ are large molecules, made from smaller building blocks.

Macromolecules Many of these molecules contain tens of thousands of atoms.

Phenylketonuria is a rare condition in which a baby is born without the ability to break down the amino acid, phenylalanine. Which of the following best explains what causes this condition?

The sequence of amino acids is incorrect, altering the enzyme phenylalanine hydroxylase's formation enough that it loses its function. A functioning enzyme then becomes a nonfunctioning enzyme due to this "misspelling" of amino acids.

Which of the following describes how complex carbohydrates—particularly starches that have not been highly processed—are broken down and used for energy? The bonds between glucose molecules are broken slowly, resulting in a large burst of energy. They are immediately broken down, releasing a large burst of energy. They are immediately broken down, providing a steady level of energy. They are used as structural molecules and not used for energy. They are slowly broken down over time, providing a steady level of energy.

They are slowly broken down over time, providing a steady level of energy. The glucose molecules in these complex carbohydrates are like "time-release" pellets of energy.

Animal fats and plant oils are sometimes used as sources of fuel for automobile engines. How is energy harvested from these molecules?

They contain long chains of hydrocarbons that, when broken, release the energy stored in the bonds linking the atoms together. The chemical breakdown of fat molecules releases a significant amount of energy.

Fats having three fatty acids linked to a glycerol molecule are called ___________. They are the fats most commonly found in the foods we eat.

Triglycerides (For this reason, the terms "fats" and "triglycerides" are often used interchangeably. Triglycerides that are solid at room temperature are generally called "fats," while those that are liquid at room temperature are called "oils.")

Triglyceride and phospholipid molecules differ in what way? -Triglycerides are nonpolar, whereas phospholipids are polar. -Triglycerides have a greater number of fatty acid tails than phospholipids. -Triglycerides are hydrophilic, whereas phospholipids are hydrophobic. -Triglycerides are proteins, whereas phospholipids are lipids. -Triglycerides are hydrophobic, whereas phospholipids are hydrophilic.

Triglycerides have a greater number of fatty acid tails than phospholipids. A triglyceride has three fatty acid tails, whereas a phospholipid has only two fatty acid tails.

True or False: Cellulose cannot be digested by humans. a. True, because cellulose is made of chitin, a complex carbohydrate that is indigestible by humans. b. True, because cellulose has a molecular structure that makes it impossible for humans to digest. c. False, because cellulose is essentially the same as starch, which is easily digested by humans. d. False, because cellulose is made of chitin, a complex carbohydrate that is easily digested by humans. e. False, because, unlike other animals, humans have microorganisms in our guts that can digest cellulose

b. Although cellulose is almost identical in composition to starch, which is easily digested by humans and other animals, a small difference in the chemical bonds between the simple sugar units causes cellulose to have a different three-dimensional shape from starch, making it indigestible.

Which of the following types of food would be considered a "fat"? A. table sugar B. lean meats C. oils D. bread E. honey

c. oils Oils consist of unsaturated triglycerides, which are a type of fat.

Which of the following elements is present in ALL organic molecules?

carbon Carbon is the element found in all organic molecules. It is almost always bound to hydrogen.

Lipids are made up of long hydrocarbon chains, composed of all carbon and hydrogen atoms. This characteristic makes lipids insoluble in water ("oil and water don't mix") because:

hydrocarbons are nonpolar. Hydrocarbons are nonpolar and hydrophobic, making them insoluble in water.

Lipids are made up of long hydrocarbon chains, composed of all carbon and hydrogen atoms. This characteristic makes lipids insoluble in water ("oil and water don't mix") because: Please choose the correct answer from the following choices, and then select the submit answer button.

hydrocarbons are nonpolar. Hydrocarbons are nonpolar and hydrophobic, making them insoluble in water.

Identify the molecule that is not a carbohydrate. glucose galactose lactase lactose fructose

lactase Lactase is an enzymatic protein. The -ase suffix at the end of its name provides a hint that it is not a carbohydrate.

All lipids are: a. phospholipids that form cell membranes. b. triglycerides that serve as an energy source. c. nonpolar and insoluble in water. d. used for short-term energy storage. e. modified forms of cholesterol.

nonpolar and insoluble in water. All lipids are nonpolar molecules that do not dissolve in water.

glucose (C subscript 6 H subscript 12 O subscript 6), which has a hexagon shape. The molecule of glucose pictured here is a(n):

organic molecule. The carbon in this molecule of glucose indicates that it is an organic molecule.

In a nucleic acid, adjacent nucleotides are bound to each other in what way?

phosphate group to sugar In nucleic acids, nucleotides are linked in a series to form a strand, with a sugar molecule attached to a phosphate group, and then a nitrogen-containing base attached to the sugar, protruding from the sugar-phosphate backbone.

In proteins, bonds between amino acids can cause a segment of the polypeptide chain to twist or fold in a corkscrew or zigzag pattern. The distribution of these corkscrew and zigzag patterns creates the ________ structure of a protein.

secondary The secondary structure of proteins is formed by the corkscrews and zigzags that result from the hydrogen bonds that form between amino acids in the polypeptide chain.

All of the following are carbohydrates except: glycogen. spider's silk. chitin. cellulose. starch.

spider's silk. Spider's silk is a protein fiber, not a carbohydrate.

Generally speaking, the greater the number of double bonds in a triglyceride:

the more "kinks" there are in the hydrocarbon tails. In unsaturated fats, some of the carbons in the hydrocarbon tails are bound to single hydrogen atoms (and to each other by double bonds). This causes the fatty acid tails of unsaturated fats to have "kinks."

The tertiary structure of a protein is the:

unique three-dimensional shape of the fully folded polypeptide. The tertiary structure of a protein is formed by the multiple twists and bends in the polypeptide chain.