4. carbohydrates

carbohydrates

the most abundant class of bioorganic molecules on Earth

75%

carbohydrates constitute this percentage by mass of dry plant materials

photosynthesis

green plants produce carbohydrates via this

carbon dioxide from the air, water from the soil

reactants in photosynthesis

sunlight

energy source in photosynthesis

in the form of cellulose, in the form of starch

2 main uses of plants for the carbohydrates they produce

structural elements

carbohydrates serve as ___________ in the form of cellulose

energy reserves

carbohydrates serve as __________ for the plants in the form of starch

plant materials

the major carbohydrate source for humans and animals

2/3

the average human diet should ideally be about _________ carbohydrate by mass

oxidation

carbohydrate __________ provides energy

glycogen

carbohydrate storage, in the form of _______, provides a short-term energy resreve

carbon atoms

carbohydrates supply ___________ for the synthesis of other biochemical substances

dna and rna molecules

carbohydrates form part of the structural framework of ______________

cell membranes

carbohydrates linked to lipids are structural components of _____________

cell-cell and cell-molecule recognition processes

carbohydrates linked to proteins function in a variety of ______________

CnH2nOn

most simple carbohydrates have empirical formulas that fit this general formula

Cn(H2O)n

an early observation by scientists was that the general formula can be written like this

hydrate of carbon

the basis for the term "carbohydrate"

not correct

the hydrate viewpoint is (correct/not correct)

carbohydrate

used to refer to an entire family of compounds, only some of which have the formula CnH2nOn

carbohydrate

is a polyhydroxy aldehyde, a polyhydroxy ketone, or a compound that yields polyhydroxy aldehydes or polyhydroxy ketones upon hydrolysis

glucose

this carbohydrate is a polyhydroxy aldehyde

fructose

this carbohydrate is a polyhydroxy ketone

glucose

fructose

large number of functional groups present

striking structural feature of carbohydrates

each

in glucose and fructose, a functional group is attached to ________ carbon atom

monosaccharides, disaccharides, oligosaccharides, polysaccharides

carbohydrates are classified on the basis of molecular size as these 4:

monosaccharide

is a carbohydrate that contains a single polyhydroxy aldehyde or polyhydroxy ketone unit

monosaccharide

this cannot be broken down into simpler units by hydrolysis reactions

monosaccharide

classification of both glucose and fructose

3-7 carbon atoms

number of carbon atoms of naturally occurring monosaccharides

5 and 6 carbon species

number of carbon atoms of naturally occurring monosaccharides that are especially common

pure monosaccharides

are water-soluble, white, crystalline solids

disaccharide

is a carbohydrate that contains 2 monosaccharide units covalently bonded to each other

sucrose, lactose

2 examples of disaccharides

table sugar

sucrose other name

milk sugar

lactose other name

disaccharide

hydrolysis of this produces 2 monosaccharide units

oligosaccharide

is a carbohydrate that contains 3 to 10 monosaccharide units covalently bonded to each other

free oligosaccharides

these oligosaccharides are seldom encountered in biochemical systems

oligosaccharides

are usually found associated with proteins and lipids in complex molecules that have both structural and regulatory functions

oligosaccharide

complete hydrolysis of ___________ produces several monosaccharide molecules

trisaccharide

produces three monosaccharide units

hexasachharide

produces six monosaccharide units

polysaccharide

is a polymeric carbohydrate that contains many monosaccharide units covalently bonded to each other

few hundred units to more than a million units

the number of monosaccharide units present in a polysaccharide varies from a _____________________

polysaccharides, disaccharides, oligosaccharides

these 3 undergo hydrolysis under appropriate conditions to produce monosaccharides

cellulose, starch

2 naturally occurring polysaccharides that are very prevalent in the world of plants

cellulose

paper in textbooks is usually this polysaccharide

cellulose

polysaccharide in cotton in clothing

cellulose

polysaccharide in wood used in home construction

starch

is a component of many types of foods, including bread, pasta, potatoes, rice, corn, beans, and peas

left-handed form, right-handed form

molecules that possess handedness exist in these 2 forms

mirror images

handedness in molecules

mirror image

the reflection of an object in a mirror

all

_______ objects have mirror images

objects with superimposable mirror images, objects with nonsuperimposable mirror images

2 classes of objects on the basis of their mirror images

superimposable mirror images

are images that coincide at all points when the images are laid upon each other

superimposable mirror images

a dinner plate with no design features have these mirror images

nonsuperimposable mirror images

are images where not all points coincide when the images are laid upon each other

nonsuperimposable mirror images

human hands are these mirror images

4

the structural requirement for handedness is the presence of a carbon atom that has ___________ different groups

tetrahedral

the structural requirement for handedness is the presence of a carbon atom that has 4 different groups bonded to it in a ________ orientation

single bonds

the tetrahedral orientation requirement is met only if the bonds to the four different groups are all ____________

chiral center

the handedness-generating carbon atom

chiral center

an atom in a molecule that has four different groups bonded to it in a tetrahedral orientation

chiral

a molecule that contains a chiral center

chiral molecule

is a molecule whose mirror images are not superimposable

chiral molecule

this molecule has handedness

achiral molecule

is a molecule whose mirror images are superimposable

achiral molecule

this molecule does not possess handedness

bromochloroiodomethane

the simplest example of a chiral organic molecule

never

carbons with double bonds are _______ chiral

chiral

chiral/achiral

multiple bond

a carbon atom involved in a __________ cannot be a chiral center since it has fewer than four groups bonded to it

single bonds

to have four groups present, all bonds about the chiral center must be _____________

like groups

a carbon atom that has two ____________ bonded to it cannot be a chiral center since it does not meet the requirement of four different groups

can be

carbon atoms in a ring system, if not involved in multiple bonding, (can be/cannot be) chiral centers

two substituents are different, two halves of the ring from the chiral center are different

chirality in a ring system occurs when these 2 conditions are met

chiral

chiral/achiral

achiral

chiral/achiral

more than one

organic molecules may contain _____________ chiral center

different responses

in human body chemistry, right-handed and left-handed forms of a molecule often elicit _____________ within the body

r-thalidomide

sleep inducing thalidomide

s-thalidomide

teratogenic thalidomide

biologically active

sometimes both chiral forms are ________, each giving a different response

greater

sometimes both chiral forms elicit the same response, but one form's response is many times __________ than that of the other

biochemically active

sometimes, only one of the two chiral forms is _____________

right-handed form

the body's response of this form of epinephrine is 20 times greater than its response to the other

monosaccharides

these are the simplest type of carbohydrate and the building block for more complex types of carbohydrates

right-handed

monosaccharides are almost always (left-handed/right-handed)

right-handed

plants produce only (left-handed/right-handed) monosaccharides

amino acids

are the building blocks of proteins

left-handed

amino acids are always (left-handed/right-handed)

phocomelia

side effect of thalidomide

phocomelia

extremities resemble those of a seal

phocomelia

hands and feet are present but the intervening arms and legs are absent