BioChem (CarbsA)

Question 1

Are the most abundant class of organic biomolecules on Earth

Answer 1

Carbohydrates

Question 2

Although they constitute about _____ by mass of dry plant materials, they are relatively low in
the human body

Answer 2

75%

Carbohydrates

Question 3

Play structural and metabolic roles in plants and animals

Answer 3

Carbohydrates

Question 4

In plants, ____ is synthesized from ____ and _____ by _____ and stored as _____ or used to synthesize the ____ of plant cell walls

Answer 4

glucose

CO2

H2O

photosynthesis

starch

cellulose

Question 5

______ is the major carbohydrate source for humans and animals

Answer 5

Dietary intake of plant materials

Question 6

The average human diet should ideally be about ____

Answer 6

two-thirds carbohydrate by mass

Question 7

Although animals can synthesize carbohydrates from_____ (as well as glycerol and
lactate), but most are derived ultimately from plants

Answer 7

amino acids

Question 8

most important carbohydrate

Answer 8

Glucose

Question 9

is the major metabolic fuel of mammals

Answer 9

Glucose

Question 10

a universal fuel of the fetus

Answer 10

Glucose

Question 11

Is the precursor of other carbohydrates in the body

What are these 3:

Galactose for synthesis of:

Answer 11

Glucose

glycogen
ribose
deoxyribose

lactose in milk,
in glycolipids
in glycoproteins and
proteoglycans

Question 12

Functions of carbohydrates in humans

Question 13

Functions of carbohydrates in humans

______ provides energy

______ (storage form of carbohydrates in humans) provides short-term energy reserve

Carbohydrates supply _____ for the synthesis of other biochemical substances
(e.g., proteins, lipids, and nucleic acids)

________ form part of RNA’s and DNA’s structural framework
respectively

______ are structural components of cell membranes

______function in a variety of cell-to-cell and
cell-to-molecule recognition processes

Answer 13

Oxidation of carbohydrates

Glycogen

carbon atoms

Ribose and deoxyribose

Carbohydrates linked to lipids (glycolipids)

Carbohydrates linked to proteins (glycoproteins)

Question 14

Examples of diseases associated with carbohydrate metabolism:

Answer 14

Diabetes mellitus

Galactosemia

Glycogen storage diseases

Lactose intolerance

Question 15

Some terms used in the study of carbohydrates:

______ is the study of the roles of sugars in health and disease

_______ refers to the entire complement of sugars of an organism, whether free or present in more complex molecules

_______ is the comprehensive study of glycome, including genetic, physiological,
pathological, and other aspects

Answer 15

Glycobiology

Glycome

Glycomics

Question 16

Carbohydrates are either _______, ________, ________ or a _____ that yields polyhydroxy aldehydes and/or polyhydroxy ketones upon ______

In short, they are aldehyde and/or ketone derivatives of polyhydric alcohols.

For example, glucose is a _______, while fructose is a ________.

Answer 16

polyhydroxy aldehydes, polyhydroxy ketones, or both

compound

hydrolysis

polyhydroxy aldehyde

polyhydroxy ketone

Question 17

Based on the number of _________, carbohydrates are classified as follows:

Answer 17

polyhydroxy aldehyde or polyhydroxy ketone units (or saccharide units)

Monosaccharide

Disaccharide

Oligosaccharide

Polysaccharide

Question 18

Monosaccharide

Also known as ______

Contains a double polyhydroxy aldehyde or polyhydroxy ketone unit

Can be broken down into simpler units by hydrolysis?

Examples:

1. is the most abundant monosaccharide in nature
2. (fruit sugar)

Naturally occurring monosaccharides have _____; however, _______ monosaccharides are especially common.

Pure monosaccharides are:

Answer 18

simple sugar

single

no

Glucose (or blood sugar)

Fructose

three to seven carbon atoms

five- and six-carbon

water-soluble, white, crystalline solids

Question 19

Disaccharide

Contains ______ that are covalently linked to each other by a _____

They are:

Examples include:

_____ of a disaccharide produces two monosaccharide units.

Historically, disaccharides are classified under oligosaccharides; however, due to the _____, disaccharide is now in a class of its own.

Answer 19

two monosaccharide units

glycosidic linkage

crystalline, water-soluble substances

sucrose (table sugar) and lactose (milk sugar)

Hydrolysis

size of the group and physiological significance

Question 20

Oligosaccharide

Contains ______ units that are covalently bonded to each other by
______

_____ are seldom encountered in biochemical systems

Usually found associated with _____ in complex molecules that have both structural and regulatory functions

Complete hydrolysis of an oligosaccharide produces _______

For example, a
______ yields three monosaccharide units, while a _________
produces six monosaccharide units

Answer 20

three to ten monosaccharide

glycosidic linkages

“Free” oligosaccharides

proteins and lipids

several monosaccharide molecules

trisaccharide

hexasaccharide

Question 21

Polysaccharide

Contains _______ covalently bonded to each other by _____

Number of monosaccharide units present in a polysaccharide varies from a few hundred units
to more than a million units

Polysaccharides also undergo ______ under appropriate conditions

Examples include

Answer 21

more than ten monosaccharide units

glycosidic
linkages

hydrolysis to monosaccharides

starch and glycogen (or animal starch)

Question 22

The term monosaccharide is from the Latin word for ______

Answer 22

saccharum means sugar

Question 23

Based on the type of carbonyl group present, they are either _____

An _____ contains an aldehyde functional group (thus, they are polyhydroxy aldehydes)

A ______ contains a ketone functional group (hence, they are polyhydroxy ketones)

Answer 23

aldoses or ketoses

aldose

ketose

Question 24

Structurally, most biochemically important monosaccharides have a chain of ____, with a carbonyl carbon group at either the terminal carbon ____ or the carbon adjacent
to it _____

If the carbonyl group involves C1, the monosaccharide is an ____

If it involves C2, the monosaccharide is a _____

Answer 24

3 to 7 carbon
atoms

(C1)

(C2)

aldose

ketose

Question 25

More often, monosaccharides are classified by both their _______ and the ______ This combined approach requires three descriptors: 1. _____, indicating whether the compound is an aldehyde or a ketone 2. ____________indicating the number of carbon atoms 3. The suffix ______, indicating a carbohydrate Examples: A six-carbon monosaccharide with an aldehyde functional group is an ______ A five-carbon monosaccharide with a ketone functional group is a _______

Answer 25

number of carbon atoms type of carbonyl function group present (aldose or ketose) Aldo or keto Tri-, tetr-, pent-, hex-, or hept- -ose aldohexose ketopentose

Question 26

______ are the smallest monosaccharides that can exist There are two trioses, which also serve as reference structures for aldoses and ketoses that contain more than 3 carbons:

Answer 26

Trioses Glyceraldehyde – an aldotriose Dihydroxyacetone – a ketotriose

Question 27

For aldoses with more than one chiral center, the ________ determines the D or L designation The configurations about the other chiral centers present are accounted for by ______ to each set of D and L enantiomers

Answer 27

chiral center farthest from the aldehyde group assigning a different common name

Question 27

WRITE. The Fischer projection formulas of all D aldoses containing three, four, five, and six carbon atoms.

Question 28

It begins with ______ at the very top and proceeds downward through the tetroses, pentoses, and hexoses The number of possible aldoses ______ each time an additional carbon atom is added because the _____ is a chiral center D-glyceraldehyde has only _____ chiral center Tetroses have ____ chiral centers Pentoses have _____ chiral centers Hexoses have ____ chiral centers

Answer 28

D-glyceraldehyde doubles new carbon atom one two three four

Question 29

A major difference between glyceraldehyde and dihydroxyacetone is that ______ Therefore, there are no D and L forms for dihydroxyacetone This reduces by half (compared with aldoses) the number of stereoisomers possible for ketotetroses, ketopentoses, and ketohexoses An aldohexose has _____ chiral carbon atoms, but a ketohexose has only _____

Answer 29

dihydroxyacetone does not have a chiral carbon atom four three

Question 30

Nearly all naturally occurring monosaccharides are ______ They are important energy sources for the human body. ______, which can be produced in the laboratory, cannot be used by the body as energy sources because the enzymes of the human body are specific for D isomers

Answer 30

D isomers D isomers L monosaccharides

Question 31

Aldotetroses have ____ chiral centers and ____ carbon There are only four (2n = 2^2) possible aldotetroses (two pairs of enantiomers) Two of the possible aldotetroses are____, while the other two are ____ The D sugars are called: The L sugars, called L-__________ are the enantiomers of the D aldotetroses

Answer 31

4 2 D sugars L sugars D-erythrose and D-threose L-erythrose and L-threose,

Question 32

aldopentoses have _____ carbon atoms ____ chiral centers There are eight (2n = 2^3) possible aldopentoses (four pairs of enantiomers) Four of the possible aldotetroses are D sugars, while the other four are L sugars

Answer 32

3

Question 33

____ is an important structural component of RNA

Answer 33

D-Ribose

Question 34

______ is produced by most plants

Answer 34

D-Arabinose

Question 35

____ is found in wood

Answer 35

D-xylose

Question 36

Aldohexoses have ____ carbons and ____ chiral centers There are sixteen (2n = 2^4) possible aldohexoses (eight pairs of enantiomers) Eight of these are D sugars, while the other eight are L sugars ______, which is the most important sugar biomedically, is a D-aldohexose

Answer 36

6 and 5 D-Glucose

Question 37

Biochemically Important Monosaccharides: D-glyceraldehyde and dihydroxyacetone are the simplest monosaccharides Their phosphorylated forms (_______) are important intermediates in glycolysis, which is a biochemical pathway that converts glucose to ______ D-Glyceraldehyde is _____, but dihydroxyacetone is ______

Answer 37

D-glyceraldehyde and dihydroxyacetone D-glyceraldehyde 3-phosphate and dihydroxyacetone phosphate two molecules of pyruvate chiral not (i.e., achiral, no chiral center)

Question 37

Ketoses have one less chiral center than aldoses of the same molecular formula because the carbonyl group is at _____ As a result, there are only four D ketohexoses, rather than eight _______, which is the most common naturally occurring ketose, is a ketohexose

Answer 37

C2 rather than C1 D-Fructose

Question 38

Known by three other names ____, particularly ripe grapes (20-30% glucose by mass), are a good source of glucose – hence, it is called ______ D-glucose is optically active and in aqueous solution rotates plane-polarized light clockwise (to the right) – hence the name ______ The term _______ is due to the fact that blood contains dissolved glucose Human cells use _____ as a primary source of energy Normal concentration of glucose in human blood is around ______ (1 dL = 100 mL); however, the actual blood glucose concentration is ______

Answer 38

Ripe fruits grape sugar dextrose blood sugar D-glucose 70-100 mg/dL dependent on the time that has elapsed since the last meal was eaten

Question 38

Of all simple sugars,______ is the most abundant in nature the most important from a human nutritional standpoint and the most important biomedically

Answer 38

D-glucose

Question 39

Biochemically Important Monosaccharides: _____ An aldopentose If carbon 3 (C3) and its attached –OH and –H groups are removed from the structure of D-glucose, the resulting structure will be that of:

Answer 39

D-ribose

Question 39

Biochemically Important Monosaccharides: ______ Seldom encountered as a free monosaccharide; however, it is a component of numerous biochemical substances Synthesized from ______ for use in lactose (milk sugar), which is a disaccharide consisting of one glucose unit and one galactose unit It is called ______ because it is a component of glycoproteins found in brain and nerve tissue Also present in chemical markers that distinguish various _______ ****************** A comparison of the Fischer projection formulas for D-galactose and D-glucose shows that the two monosaccharides differ only in the configuration of –OH and –H on one carbon (at carbon 4 or C4) Therefore, D-galactose, and D-glucose are ____ at _____

Answer 39

D-galactose glucose in the mammary glands brain sugar blood types (e.g., ABO blood group – A, B, AB, and O) epimers C4

Question 39

_______ are pancreatic hormones that play important roles in regulating the glucose concentration in blood Proper functioning of the human body requires the glucose concentration in blood to be maintained within its normal range ______ is a condition due to abnormal functioning of the hormonal control process for blood glucose levels

Answer 39

Insulin and glucagon Diabetes mellitus

Question 40

Most important ketohexose biochemically Known by two other names Called _____ because of its ability to rotate plane-polarized light counterclockwise, although it is a D-isomer Also known as ______, because D-fructose is found in many fruits and is present in honey in equal amounts with glucose Considered the sweetest tasting of all sugars Used as a ______, not because it has fewer calories per gram than other sugars but because less is needed for the same amount of sweetness In humans, D-Fructose is the primary source of energy of ______

Answer 40

D-Fructose two other names: 1. levulose 2. fruit sugar dietary sugar spermatozoa

Question 41

The structures of D-fructose and D-glucose are identical from ______ Their differences in ______ are due to the _______

Answer 41

carbon 3 (C3) to carbon 6 (C6) carbon 1 (C1) and carbon 2 (C2) presence of a ketone group at C2 of fructose and of an aldehyde group at C1 of glucose

Question 42

D-Ribose have the component of _____ and energy-rich compounds, such as ______ ______ is a reduced form of D-ribose and is a component of DNA When the oxygen atom attached to carbon 2 of D-ribose is removed and replaced by a hydrogen atom (i.e., reduction), the resulting molecule is 2-deoxy-D-ribose

Answer 42

ribonucleic acid (RNA) adenosine triphosphate (ATP) 2-deoxy-D-ribose