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Biological Chemistry > BioChem (CarbsA) > Flashcards

BioChem (CarbsA) Flashcards

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1
Q

Are the most abundant class of organic biomolecules on Earth

A

Carbohydrates

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2
Q

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

A

75%

Carbohydrates

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3
Q

Play structural and metabolic roles in plants and animals

A

Carbohydrates

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4
Q

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

A

glucose

CO2

H2O

photosynthesis

starch

cellulose

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5
Q

______ is the major carbohydrate source for humans and animals

A

Dietary intake of plant materials

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6
Q

The average human diet should ideally be about ____

A

two-thirds carbohydrate by mass

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7
Q

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

A

amino acids

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8
Q

most important carbohydrate

A

Glucose

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9
Q

is the major metabolic fuel of mammals

A

Glucose

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10
Q

a universal fuel of the fetus

A

Glucose

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11
Q

Is the precursor of other carbohydrates in the body

What are these 3:

Galactose for synthesis of:

A

Glucose

glycogen
ribose
deoxyribose

lactose in milk,
in glycolipids
in glycoproteins and
proteoglycans

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12
Q

Functions of carbohydrates in humans

A
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13
Q

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

A

Oxidation of carbohydrates

Glycogen

carbon atoms

Ribose and deoxyribose

Carbohydrates linked to lipids (glycolipids)

Carbohydrates linked to proteins (glycoproteins)

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14
Q

Examples of diseases associated with carbohydrate metabolism:

A

Diabetes mellitus

Galactosemia

Glycogen storage diseases

Lactose intolerance

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15
Q

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

A

Glycobiology

Glycome

Glycomics

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16
Q

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 ________.

A

polyhydroxy aldehydes, polyhydroxy ketones, or both

compound

hydrolysis

polyhydroxy aldehyde

polyhydroxy ketone

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17
Q

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

A

polyhydroxy aldehyde or polyhydroxy ketone units (or saccharide units)

Monosaccharide

Disaccharide

Oligosaccharide

Polysaccharide

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18
Q

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:

A

simple sugar

single

no

Glucose (or blood sugar)

Fructose

three to seven carbon atoms

five- and six-carbon

water-soluble, white, crystalline solids

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19
Q

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.

A

two monosaccharide units

glycosidic linkage

crystalline, water-soluble substances

sucrose (table sugar) and lactose (milk sugar)

Hydrolysis

size of the group and physiological significance

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20
Q

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

A

three to ten monosaccharide

glycosidic linkages

“Free” oligosaccharides

proteins and lipids

several monosaccharide molecules

trisaccharide

hexasaccharide

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21
Q

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

A

more than ten monosaccharide units

glycosidic
linkages

hydrolysis to monosaccharides

starch and glycogen (or animal starch)

22
Q

The term monosaccharide is from the Latin word for ______

A

saccharum means sugar

23
Q

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)

A

aldoses or ketoses

aldose

ketose

24
Q

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 _____

A

3 to 7 carbon
atoms

(C1)

(C2)

aldose

ketose

25
Q

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 _______

A

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

26
Q

______ 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:

A

Trioses

Glyceraldehyde – an aldotriose

Dihydroxyacetone – a ketotriose

27
Q

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

A

chiral center farthest from the aldehyde group

assigning a different common name

27
Q

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

A
28
Q

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

A

D-glyceraldehyde

doubles

new carbon atom

one

two

three

four

29
Q

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 _____

A

dihydroxyacetone
does not have a chiral carbon atom

four

three

30
Q

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

A

D isomers

D isomers

L monosaccharides

31
Q

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

A

4

2

D sugars

L sugars

D-erythrose and D-threose

L-erythrose and L-threose,

32
Q

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

A

3

33
Q

____ is an important structural component of RNA

A

D-Ribose

34
Q

______ is produced by most plants

A

D-Arabinose

35
Q

____ is found in wood

A

D-xylose

36
Q

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

A

6 and 5

D-Glucose

37
Q

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 ______

A

D-glyceraldehyde and dihydroxyacetone

D-glyceraldehyde 3-phosphate and dihydroxyacetone
phosphate

two molecules of pyruvate

chiral

not (i.e., achiral, no chiral center)

37
Q

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

A

C2 rather than C1

D-Fructose

38
Q

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 ______

A

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

38
Q

Of all simple sugars,______ is the most abundant in nature

the most important from a human nutritional standpoint

and the most important biomedically

A

D-glucose

39
Q

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:

A

D-ribose

39
Q

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 _____

A

D-galactose

glucose in the mammary glands

brain sugar

blood types (e.g., ABO blood group – A, B, AB, and O)

epimers

C4

39
Q

_______ 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

A

Insulin and glucagon

Diabetes mellitus

40
Q

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 ______

A

D-Fructose

two other names:
1. levulose
2. fruit sugar

dietary sugar

spermatozoa

41
Q

The structures of D-fructose and D-glucose are identical from ______

Their differences in ______ are due to the _______

A

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

42
Q

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

A

ribonucleic acid (RNA)

adenosine
triphosphate (ATP)

2-deoxy-D-ribose

43
Q
A
44
Q
A
45
Q
A

Biological Chemistry (3 decks)

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