Chapter 5: Structure and Function of Large Biological Molecules

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

chitin

In living organisms, DNA exists as a __________ with the strand(s) __________.

double helix; running antiparallel

The type of bond that forms to join monomers (such as sugars and amino acids) into polymers (such as starch and proteins) is a(n) __________ bond.

covalent

The secondary structure of a peptide backbone is stabilized by __________ forming either a(n) __________ or a(n) __________.

hydrogen bonds; α helix; β pleated sheet

The sequence of amino acids in a protein is called the __________ structure of the protein.

primary

Sugars have a(n) __________ group that interacts with a _________ group that forms ring structures when the dry molecule is placed in water.

carbonyl (-C=O); hydroxyl (-OH)

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

glycogen

A shortage of phosphorus in the soil would make it especially difficult for a plant to manufacture __________.

DNA

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

phospholipids

The tertiary structure of a protein includes all of the following interactions except _________ bonds.

peptide

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

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

The proper three-dimensional shape and folding of a protein is assisted by _________.

molecules called chaperonins

Which type of protein shields a newly forming protein from cytoplasmic influences while it is folding into its functional form?

Chaperonins

Sugars are molecules that have __________ C:H:O and are called __________.

a 1:2:1 ratio of; carbohydrates

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

glycosidic linkages

Which is the term for compounds that do not mix with water?

Hydrophobic

Nitrogenous bases are classified as either purines or pyrimidines. Examples of purines are __________.

adenine and guanine

Macromolecules, the molecules of life, include all of the following except __________.

trace elements

In a dehydration synthesis reaction, __________ is always formed as a by-product of the reaction.

water

Protein molecules are polymers (chains) of __________.

amino acid molecules

The components of nucleic acids are __________.

a nitrogenous base, a pentose sugar, and a phosphate

Carbohydrates are used in our bodies mainly for __________.

energy storage and release

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

they are all disaccharides

When comparing saturated and naturally occurring unsaturated fats, the unsaturated fats have __________ and are __________ at room temperature.

cis double bonds; liquids

Which of the following is a polymer?

Cellulose, a plant cell wall component

The sex hormones estrogen, progesterone, and testosterone belong to which class of molecules?

Lipids

__________ is always involved in hydrolysis reactions.

Water

The molecule with four fused rings that is found in animal membranes and is the precursor of vertebrate sex hormones is __________.

cholesterol

Sickle-cell anemia is a disease that is caused by __________ in the __________ of the protein.

a single amino acid change; primary structure

The peptide bond is __________.

a covalent bond joining amino acids together to form a polypeptide

Large polymers are known as __________

macromolecules

A _______ is a long molecule consisting of many similar blocks

Polymer

The repeating units that serve as building block are called

monomers

Dehydration reaction

synthesizing a polymer

Hydrolysis

breaking down a polymer

Carbohydrates

Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar budling blocks

Monosaccharides _____________________

have molecular formulas that are usually multiples of CH₂O

The most common monosaccharide

Glucose (C₆H₁₂O₆)

How are monosaccharides classified?

• The location of the carbonyl group ( as aldose or ketose )

• The number of carbons in the carbon skeleton

Trioses

Three carbon sugars ( C₃H₆O₃)

Pentoses

five carbon sugars ( C₅H₁₀O₅ )

Hexoses

Six-carbon sugars ( C₆H₁₂O₆ )

Though often drawn as linear skeletons, _____________

in aqueous solutions many sugars form rings

What does Monosaccharides serve as _____________

major fuel for cells and as raw material for building molecules

A disaccharide is formed when_________

a dehydration reaction joins two monosaccharides

This covalent bond between two monosaccharides is called_________

a glycosidic linkage

Polysaccharides have___________

storage and structural roles

How do we determine the function and architecture of a polysaccharide?

-By its sugar monomers

-The positions of its glycosidic linkages

Simplest form of starch

Amylose

What is starch and what does it consist of ?

A storage polysaccharide of plants and consists of glucose monomers

___________ is a storage polysaccharide in animals

Glycogen

Where is glycogen mainly stored?

In the liver and muscle cells

When the demand for sugar increases_______________

Hydrolysis of glycogen in these cells releases glucose

What is a major component of the tough wall of plant cells?

The polysaccharide cellulose

________________ is a polymer of glucose

Cellulose

The two rings for glucose

Alpha ( α )

Beta ( β )

Enzymes that digest starch by hydrolyzing α linkages___________________

cant hydrolyze β linkages in cellulose

Where can chitin be found?

In exoskeleton of arthropods

What does Chitin provide?

structural support for the cell walls of many fungi

What does not include true polymers?

Lipids

What does lipids consist mostly of?

hydrocarbon regions

The most biologically important lipids are?

Fats, phospholipids, and steroids

A fatty acid consists of ?

A carboxyl group attached to a long carbon skeleton

Why does fats separate from water?

Water molecules hydrogen-bond to each other and exclude the fats

How are triacylglycerol created?

Three fatty acids are joined to glycerol by an ester linkage

Which fatty acid have the maximum number hydrogen atoms?

Saturated fatty acids

Does saturated fatty acids have double bonds?

NO

which one has one or more double bonds?

Unsaturated fatty acids

What is the major function of fats?

Energy storage

Where do humans and other mammals store their long-term food reserves?

In Adipose cells

what do adipose tissue also do?

Cushions vital organs and insulates the body

In a phospholipid___________________

Two fatty acids and a phosphate group are attached to glycerol

Are the two fatty acids tails on a phospholipid hydrophobic or hydrophilic?

hydrophobic

The phosphate group that is attached to glycerol is hydrophobic or hydrophilic?

hydrophilic

Steroids are lipids characterized by ________

A carbon skeleton consisting of four fused rings

________ accounts for more than 50% of the dry mass of most cells

Proteins

What acts like a catalysts that speeds up chemical reactions?

Enzymes

What is the function of Enzymatic proteins?

Selective acceleration of chemical reactions

What is the function of Defensive proteins?

Protection against disease

What is the function of storage proteins?

Storage of amino acids

What is the function of transport proteins?

Transport of substances

What is the Function of Hormonal Proteins

Coordination of an organism’s activities

What is the Function of receptor proteins

Response of cell to chemical stimuli

What is the function of contractile and motor proteins?

Movement

What is the function of structural proteins?

Support

Proteins are all constructed from the _____________________

same set of 20 amino acids

________ are unbraced polymers build from these amino acids

Polypeptides

For proteins, what does it consist of?

One or more polypeptides

Amino acids are organic molecules________

with amino and carboxyl groups

Amino acids differ in their properties due to differing side chains called_____

R groups

Amino acids are linked by covalent bonds called____________

peptide bonds

What determines a protein’s three dimensional structure?

The sequence of amino acids

In what level of protein structure does it have coils and folds in the polypeptide chain?

Secondary structure

How are tertiary structure determined?

By interactions among various side chains ( R groups )

Quaternary structure results when_______

two or more polypeptide chains form one macromolecule

Protein consist of how many polypeptides?

Four

The loss of protein’s native structure is called?

Denaturation

A denatured protein is biologically _______

inactive

The amino acid sequence of a polypeptide is programmed by a unit of inheritance called_______?

gene

What are the two types of nucleic acids?

DNA and RNA