BIO 161 CH. 5 Carbohydrates

Glycogen

An extensively branched glucose storage polysaccharide found in the liver and muscle tissue of animals; the animal equivalent of starch.

Glucose

C6H12O6 A simple sugar that is an important source of energy.

Photosynthesis

CO2 + H2O + sunlight ----> (CH2O)n + O2 1. The electrons in the C=O bonds of carbon dioxide and the C-O bonds of carbohydrates are held tightly because of oxygen's high electronegativity. Thus, they have relatively low potential energy. 2. The electrons involved in the C-H bonds of carbohydrates are shared equally because the electronegativity of carbon and hydrogen is about the same. Thus, bonds are weaker and these electrons have relatively high potential energy. 3. Electrons are also shared equally in the carbon-carbon (C-C) bonds of carbohydrates—meaning that they, too, have relatively high potential energy. So, because C-C and C-H bonds have much higher potential energy than C-O bonds have, carbohydrates store much more chemical energy than carbon dioxide does.

cellulose, chitin, or peptidoglycan

These fibers tend to be insoluble due to the strong interactions between strands consisting of β-1,4- glycosidic linkages. The exclusion of water within these fibers makes their hydrolysis more difficult so they are resistant to deg- radation and decay

Glycolipids are

a lipid that has been glycosylated, meaning it has one or more covalently bonded carbohydrates

Cellulose

a polymer made from β-glucose monomers joined by β-1,4-glycosidic linkages that is common in the cell walls of many organisms

Amylose

a polysaccharide found in plants as one of the two components of starch, unbranched helix all alpha 1-4, linkages (making up approximately 20-30% of the structure).

3-dimensional structure of peptidoglycan

a short chain of amino acids is attached at the C-3 carbon of NAM. When molecules of peptidoglycan align, peptide bonds link the amino acid chains on adjacent strands.

Amylopectin

a soluble polysaccharide and highly-branched polymer (branching occurs at about one out of every 30 glucose residues) of glucose found in plants as one of the two components of starch (the other being amylose).

2. What type of bond is formed between two sugars in a disaccharide? a. glycosidic linkage b. phosphodiester bond c. peptide bond d. hydrogen bond

a.

4. What are the primary functions of carbohydrates in cells? a. cell identity, energy storage, raw material source for synthesis, and structure b. catalysis, energy storage, metabolism, and structure c. catalysis, digestion, energy storage, and information storage d. energy storage, information storage, polymerization, and raw material source for synthesis

a.

carbohydrate, or sugar

Encompasses the monomers called monosaccharides. made up of a carbonyl group (C=O), several hydroxyl groups (-OH), along with multiple carbon-hydrogen bonds (C-H). Consider formaldehyde (CH2O)

Monosaccharides

Single sugar molecules ex.glucose, fructose, galactose

Amylases

The enzymes involved in breaking the α-glycosidic link- ages in starch are called... Your salivary glands and pancreas produce these that are then secreted into your mouth and small intestine

Sucrose is a disaccharide consisting of α-glucose and β-fructose. What type of glycosidic bond links these monosaccharides?

The monosaccharides are linked by an α-1,2-glycosidic bond because the hydroxyl is in the α position in glucose. Since the bond is formed with β-fructose, the linkage is often referred to as being an α-β-1,2-glycosidic bond.

Phosphorylase

The most important enzyme involved in catalyzing the hydro- lysis of α-glycosidic linkages in glycogen molecules is a protein

13. You perceive the sweetness of sucrose based on a specific interaction between fructose and proteins on your tongue's taste buds. What structural difference between glucose and fructose would you predict to be responsible for the fact that fructose tastes sweeter?

The position of the carbonyl is the most striking structural difference between these sugars (glucose is an aldose while fructose is a ketose) and so it is most likely responsible for the disparity in taste perception.

Peptidoglycan

The primary structural component of bacterial cell walls consists of a polysaccharide called .... It has a long backbone formed by NAG and N-acetylmuramic acid (NAM) that alternate with each other and are linked by β-1,4-glycosidic linkages

When a cell needs energy, reactions break down glucose and capture some of the released energy through synthesis of the nucleotide adenosine triphosphate (ATP)

(CH2O)n +O2 +ADP +Pi---->CO2 +H2O+ATP

Glycolipids and glycoproteins

contain carbohydrates that project outside the cell from the surface of the plasma membrane enclosing the cell. these sugar groups have distinctive structures that identify the type or species of the cell.

Formation of β-glycosidic linkage

creates lactose a disacchride

Formation of α-glycosidic linkage

creates maltose in a condensation reaction, a disacchride

9. SOCIETY Galactosemia is a potentially fatal disease that occurs in humans who lack the enzyme that converts galactose to glucose. If you were a physician treating a person with this disease, which of the following would you have them exclude from their diet? a. maltose b. starch c. mannose d. lactose

d; lactose is a disaccharide of glucose and galac- tose, which can be cleaved by enzymes expressed in the human gut to release galactose.

How glycosidic linkages are different from peptide bonds in proteins and phosphodiester linkages in nucleic acids

glycosidic linkages form between hydroxyl groups, and because every monosaccharide contains at least two hydroxyls, the location and geometry of glycosidic linkages can vary widely among oligosaccharides and polysaccharides

Glycoprotein

is a protein that is similarly linked to carbohydrates—usually rela- tively short oligosaccharides

Polysaccharides

large polymers of monosaccharides connected by glycosidic linkages

The presence of a carbonyl group along with multiple polar hydroxyl groups means that even the simplest sugars have many reactive and hydrophilic functional groups

sugars are polar molecules that form hydrogen bonds with water and are easily dissolved in aqueous solutions

When glucose forms a ring

the C-1 carbon (the first carbon in the linear chain) forms a bond with the oxy- gen atom of the C-5 hydroxyl. The hydrogen displaced from the C-5 hydroxyl is transferred to the C-1 carbonyl. This transfer preserves the number of atoms and hydroxyls between the ring and linear forms

Two aldose sugars have same molecular formula (C6H12O6) but different bc...

they differ in the spatial arrangement of the hydroxyl group on the fourth carbon

trisoses

three carbon sugars

Disaccharide

two sugars link together, the resulting molecule is known as

Pentose

5 carbon sugar (ribose, deoxyribose)

Hexose

A 6-carbon sugar (ex: glucose, galactose, fructose)

Ketose

A carbohydrate whose carbonyl group is a ketone

Aldose

A carbohydrate whose carbonyl group is an aldehyde

Starch

A storage polysaccharide in plants consisting entirely of α-glucose joined by glycosidic linkage that sare between C-1 and C-4 carbons, and the angle of these bonds causes the chain of glucose residues to coil into a helix

Chitin

A structural polysaccharide that stiffens the cell walls of fungi and in the exoskeletons of all arthropods. The monosaccharide involved is one called N-acetylglucosamine. These NAG monomers are joined by β-1,4-glycosidic linkages

12. Sucrose is cleaved in your saliva by the enzyme sucrase to release glucose and fructose. Use the structural formula of sucrose to describe fructose using the terms that define its carbon number and placement of the carbonyl group.

Fructose is a hexose based on having six carbons, and it is a ketose because the carbonyl is within the carbon chain (C-2)

Carbohydrates have diverse functions in cells:

In addition to serving as precursors to larger molecules, they (1) provide fibrous structural materials, (2) indicate cell identity, and (3) store chemical energy

cellulose, chitin, and peptidoglycan are effective structural molecules

In the cell walls of plants, for example, a collection of about 80 cellulose molecules are cross-linked by hydrogen bonding to produce a tough fiber. These cellulose fibers, in turn, crisscross to form a tough sheet that is able to withstand pulling and pushing forces—what an engineer would call tension and compression

Galactose

Milk sugar (monosaccharide)

7. Compare and contrast polysaccharides and nucleic acids (see Chapter 4) in terms of monomer diversity and how the monomers are joined together.

Monomers of carbohydrates vary exten- sively in their numbers of carbons, the position of the carbonyl group, the orientations of hydroxyl groups, and the presence of modifications (e.g., modified sugar residues in chitin and peptidoglycan). In contrast, there are only four different monomers of nucleic acids. Glycosidic linkages vary more in location and geometry than do linkages between nucleic acid residues

1. What are three ways monosaccharides differ from one another?

Monosaccharides can differ from one another in three ways: (1) the location of their carbonyl group; (2) the number of carbon atoms they contain; and (3) the orientations of their hydroxyl groups

glycosidic linkage

Monosaccharides polymerize when a condensation reaction occurs between two hydroxyl groups, resulting in a covalent bond called a

Carbon Dioxide (CO2)

O::=C=::O

alpha glucose

OH on bottom

beta glucose

OH on top beta is more common because it is slightly more stable than α-glucose

Cellulose three dimensional structure

Parallel strands joined by hydrogen bonds

14. High-fructose corn syrup is produced by converting starch from corn into a mixture of glucose and fructose monosaccharides. What two events must occur in this process in order to turn starch into these simple sugars?

To convert the starch polymer into monosaccharides, it must be hydrolyzed by an enzyme such as amylase. Since fructose is not in starch, the second event must be to convert some of the glucose sugars into fructose

8. Lysozyme, an enzyme found in human saliva, tears, and other secretions, catalyzes the hydrolysis of the β-1,4-glycosidic linkages in peptidoglycan. Predict the effect of this enzyme on bacteria and how it may be involved in human health.

When bacteria contact lysozyme, the peptidoglycan in their cell walls begins to degrade, leading to the death of the bacteria. Lysozyme therefore helps protect humans against bacterial infections.

6. What is the difference between linking glucose molecules with α-1,4-glycosidic linkages versus β-1,4-glycosidic linkages? What are the consequences?

When you compare the glucose monomers in an α-1,4-glycosidic linkage versus those in a β-1,4-glycosidic linkage, the linkages are located on opposite sides of the plane of the glucose rings, and the glucose monomers are linked in the same orientation versus having every other glucose flipped in orienta- tion. β-1,4-glycosidic linkages are much more likely to form linear fibers and sheets, so they resist degrada- tion.

3. What holds cellulose molecules together in bundles large enough to form fibers? a. the cell wall b. peptide bonds c. hydrogen bonds d. hydrophobic interactions

c.

5. Which of the differences listed here could be found among molecules of the same monosaccharide? a. different orientations of a hydroxyl group in the linear form b. different numbers of carbons c. different orientations of a hydroxyl group in the ring form d. different positions of the carbonyl group in the linear form

c.

3-dimensional structure of Chitin

every other residue being flipped in orientation. The NAG subunits in chitin also form hydrogen bonds between adjacent strands to produce a stiff protective armor.

The cellulose that you ingest when you eat plants

fiber, forms a porous mass that absorbs and retains water. This sponge- like mass adds moisture and bulk that helps fecal material move through the intestinal tract more quickly, preventing constipa- tion and other problems

glucose is both a source of carbon atoms that are used to construct other mol- ecules and of chemical energy that sustains life

galactose must first be converted to glucose via an enzyme-catalyzed reaction to be used in these same ways

Starch is made up of

polymers amylose an α-1,4-glycosidic linkages, and amylopectin an α-1,6 linkage

Oligosaccharides

short chains of 3 or more monosaccharides (at least 10)

Most common polysaccharides found in organisms today

starch, glycogen, cellulose, and chitin, along with a modified polysaccharide called pepti- doglycan

Maltose and lactose

α-1,4-glycosidic linkage and the β-1,4-glycosidic linkage. The numbers refer to the carbons on either side of the linkage, indicating that both linkages are between the C-1 and C-4 carbons. Their geometry, however, is different: α and β refer to the contrasting orientations of the C-1 hydroxyls—on opposite sides of the plane of the glucose rings (i.e., "below" versus "above" the plane)