4. Biomolecules

Lipids

Lipid overview | Macromolecules | Biology | Khan Academy

 No. Triacylglycerols are completely insoluble in aqueous solution and thus have an unsuitable structure for membranes. 

 No. Proteins do make up a substantial portion of cell membranes, but proteins are not lipids. 

 No. There is some cholesterol in cell membranes, but it is not the main structural component. 

The cell membrane has a unique position. It must separate the aqueous solution inside the cell from the aqueous solutions outside the cell.

The lipids that form the main structural component of cell membranes are __________.

Properties of Biological Macromolecules | AP Biology 1.4

Steroids & Waxes

Animation: Space-Filling Model of a Phospholipid

 three fatty acid molecules, all pointing in different directions 

 No. Phospholipids are composed of two fatty acid tails attached to a glycerol to which is also attached an electrically charged head region. Think about how hydrophobic substances differ from hydrophilic ones. 

 two fatty acid molecules pointing in different directions 

 No. Think about how hydrophobic substances differ from hydrophilic ones. 

 both a saturated fatty acid and an unsaturated fatty acid 

 No. Unsaturated fatty acids and saturated fatty acids would have similar solubility when placed in water. 

 No. Only one end of a phospholipid molecule is charged. 

 a charged or polar end and an uncharged or nonpolar end 

What would be the structure of a molecule that has both polar, or charged, and nonpolar regions?

If a small droplet of triacylglycerol molecules is suspended in water, the fat molecules form a "ball of spaghetti" with no particular orientation. But if a droplet of phospholipid molecules is put in water, all the molecules point outward, toward the water. Phospholipids are forced into this orientation because phospholipids have __________.

Evaluate this statement: Gene flow increases the genetic divergence of populations.

The polar heads avoid water; the nonpolar tails attract water (because water is polar and opposites attract).

Phospholipids do not interact with water because water is polar and lipids are nonpolar.

The polar heads interact with water; the nonpolar tails do not.

How do phospholipids interact with water molecules?a) The polar heads avoid water; the nonpolar tails attract water (because water is polar and opposites attract).b) Phospholipids do not interact with water because water is polar and lipids are nonpolar.c) The polar heads interact with water; the nonpolar tails do not.d) Phospholipids dissolve in water.

Which type of fatty acids only contain Carbon-Carbon single bonds?a) Unsaturated.b) Saturated.c) Trans fats.d) Steroids.

 No. Actually, lipids are typically smaller than the other three types of biological macromolecules. 

 No. All molecules have a specific shape. 

 No. Carbon forms the skeleton of fatty acids and steroids. 

 do not contain nitrogen and phosphorus atoms 

 No. Phospholipids contain phosphorus and may contain nitrogen. 

Contrast the structure of lipids with that of carbohydrates, proteins, and nucleic acids.

Lipids differ from other large biological molecules in that they __________.

#1 A Level Biology - Biological Molecules

 Cholesterol is not important for humans anymore. It is a holdover from hunter-gatherer days when food was scarce. 

 No. Cholesterol is an important constituent of cell membranes and the precursor for vertebrate sex hormones. 

 Cholesterol is an important energy storage molecule. 

 No. Although cholesterol is a lipid, it is not used for cellular energy storage. 

 Cholesterol is an important constituent of nucleotides. 

 No. Cholesterol is not directly involved in nucleotide synthesis. 

 Cholesterol aids in the formation of amino acids that are used to build proteins. 

 No. Cholesterol is not directly involved in amino acid synthesis. 

 Cholesterol is the precursor for many important molecules such as sex hormones. 

Where is cholesterol used in the body?

High cholesterol levels are considered a major risk factor for heart disease. If it is so bad for humans, why does the body make cholesterol in the first place?

Which of the following terms is least like the others?
a. monosaccharide;
b. phospholipid;
c. fat;
d. steroid;
e. lipid

Fatty Acids

Human activities are causing the fragmentation of the Brazilian Atlantic rain forest. One result is that toucans have become extinct or nearly extinct in some of the forest fragments. Does the absence of toucans affect the forest?

Toucans can eat fruits with large seeds because their large bills can open wide. Most other birds in the same forest can only eat small seeds. Ecologist Mauro Galetti and his colleagues measured the seed sizes of palms in forest fragments with and without toucans. The graphs show two of the forest populations they studied. What is the take-home message of the data? <IMAGE>

The main constituents of the plasma membrane are                   .
a. carbohydrates and lipids;
b. proteins and phospholipids;
c. fats and carbohydrates;
d. fatty acids and nucleic acids

 removing hydrogen atoms and forming additional double bonds in the fatty acid hydrocarbon chains 

 No. This process would make the vegetable oil liquid, even at lower temperatures. 

 removing hydrogen atoms and forming additional single bonds in the fatty acid hydrocarbon chains 

 No. If hydrogen atoms were removed, additional double bonds would be formed. 

 adding hydrogen atoms to the single-bonded carbon atoms of the fatty acid hydrocarbon chains 

 No. Additional hydrogen atoms cannot be added if each carbon of the fatty acid hydrocarbon chain is already saturated with hydrogen. 

 None of the listed responses is correct. 

 adding hydrogen atoms to the fatty acid hydrocarbon chains, thereby converting carbon-carbon double bonds to single bonds 

What is the structural difference between saturated and unsaturated fatty acids?

Manufacturers make vegetable oils solid or semisolid at room temperature by __________.

They contain at least one steroid molecule.

They are fatty acids bound to long chain alcohol molecules.

They are made of 4 fused carbon ring molecules.

Choose the correct statement about biological waxes:a) They contain at least one steroid molecule.b) They are fatty acids bound to long chain alcohol molecules.c) They are extremely hydrophilic.d) They are made of 4 fused carbon ring molecules.

The molecule shown the figure is a ________.<img src="https://static.studychannel-prd.pearsonprd.tech/courses/biology/thumbnails/images/7356911c" class="fr-fic fr-dii">a) Fatty acid.b) Wax.c) Steroid.d) Triacylglycerol.e) Phospholipid.

 Both molecules contain a phosphate group. 

 No. Triacylglycerols do not contain a phosphate group. 

 Triacylglycerols may be saturated or unsaturated, but all phospholipids are saturated. 

 No. The two fatty acid chains of phospholipids may be saturated or unsaturated. 

 Phospholipids are the primary storage form for fats in our bodies. 

 No. Triacylglycerols are the primary storage form for fats in our bodies. 

 In nature, phospholipids occur in fused rings (sterol form), whereas triacylglycerols maintain a straight-chain form. 

 No. Phospholipids are not steroids. Triacylglycerols are composed of three fatty acids joined to a molecule of glycerol by ester linkages. 

 Phospholipid molecules have a distinctly polar "head" and a distinctly nonpolar "tail," whereas triacylglycerols are predominantly nonpolar. 

Consider what phospholipids contain that is missing from triacylglycerols.

Which of the following is a true statement comparing phospholipids and triacylglycerols (fats and oils)?

Triglycerides

Animation: Lipids

 Saturated triacylglycerols are fats; unsaturated triacylglycerols are carbohydrates. 

 Saturated triacylglycerols have more double bonds than unsaturated triacylglycerols do. 

 No. Saturated triacylglycerols have fewer double bonds than unsaturated triacylglycerols do. 

 Saturated triacylglycerols are liquid at room temperature. 

 No. Saturated triacylglycerols are solid at room temperature; unsaturated triacylglycerols are usually liquid at room temperature. 

 All of the listed responses are correct. 

 No. Only one of the choices is correct. 

 For carbon skeletons of equal length, saturated triacylglycerols have more hydrogen atoms than unsaturated triacylglycerols do. 

Review the structures of saturated and unsaturated triacylglycerols. .

Nutritionally, saturated triacylglycerols are considered to be less healthful than unsaturated triacylglycerols. What is the difference between them?

 No. Estradiol and testosterone are not proteins. 

 No. Estradiol and testosterone are not amino acids. 

 No. Estradiol and testosterone are not carbohydrates. 

 No. Estradiol and testosterone are not nucleic acids. 

Consider the molecular structures and the solubilities of these substances.

The sex hormones estradiol and testosterone belong to which class of molecules?

Biomolecules - The Lipids

No. Hydrophobic means "water fearing."

 hydrophilic; consist of units assembled by dehydration reactions 

 No. Fatty acid tails, which consist of nonpolar hydrocarbon chains, are not hydrophilic. 

 hydrophilic; are easily hydrolyzed into their monomers 

 No. Fatty acid tails, which consist of nonpolar hydrocarbon chains, are not hydrophilic. Fatty acid tails are not polymers; hence, they are not composed of monomers. 

 hydrophobic; consist of units assembled by dehydration reactions 

 No. Both hydrophilic and hydrophobic molecules may be assembled by dehydration reactions. 

 hydrophobic; have no charges to which water molecules can adhere 

Consider the molecular structure of a fatty acid.

The fatty acid tails of a phospholipid are __________ because they __________.

Macromolecule Review

 No. Phospholipids are partially soluble in an aqueous medium because of their hydrophilic "heads." 

 No. Hydrophilic compounds are those that are soluble in water. 

 No. Proteins may be soluble or insoluble in water depending on the number and types of their R (side) groups. 

 No. Although hydrogen-bonded compounds are likely to be water-soluble, this is not the term that means "do not mix with water." 

Consider the meaning of the prefixes and suffixes of the choices.

Which of the following terms can be correctly used to describe compounds that do not mix with water?

A triglyceride is a form of _______ composed of ___________.a) Lipid ; fatty acids &amp; Glucose.b) Lipid ; Fatty acids &amp; Glycerol.c) Carbohydrate ; Fatty acids only.d) Lipid ; Ribose.

Which of the following is true of unsaturated fats?
a. They are more common in animals than in plants.
b. They have double bonds in their fatty acid chains.
c. They generally solidify at room temperature.
d. They contain more hydrogen than do saturated fats having the same number of carbon atoms.

Lipids | Fats, Steroids, and Phospholipids | Biological Molecules Simplified #4

 No. Glycosidic linkages join carbohydrate monomers. 

 No. Phosphodiester linkages join nucleotides. 

Review the formation and structure of triacylglycerols. .

Some lipids are formed when fatty acids are linked to glycerol. These subunits are linked together by __________.

A fat molecule consists of                   .
a. carbohydrates and proteins;
b. complex carbohydrates only;
c. saturated oxygen atoms;
d. a carbon skeleton and fatty acids

Phospholipids

Macronutrients                   .
a. include carbohydrates and vitamins;
b. should make up a small percentage of a healthful diet;
c. are essential in minute amounts to help enzymes function;
d. include carbohydrates, fats, and proteins;
e. are synthesized by cells and not necessary to obtain from the diet

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