Carbohydrates - PowerPoint PPT Presentation

Loading...

PPT – Carbohydrates PowerPoint presentation | free to download - id: 80b9ea-N2I0N



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Carbohydrates

Description:

Carbohydrates Pensacola High School IB Chemistry 3 Version 1.12 1 Carbohydrates Contain Carbon, Hydrogen and Oxygen Can be characterized as Monosaccharides ... – PowerPoint PPT presentation

Number of Views:50
Avg rating:3.0/5.0
Slides: 31
Provided by: lsc95
Learn more at: http://phsibsupport.org
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Carbohydrates


1
Carbohydrates
  • Pensacola High School
  • IB Chemistry 3

Version 1.12
1
2
Carbohydrates
  • Contain Carbon, Hydrogen and Oxygen
  • Can be characterized as
  • Monosaccharides
  • Disaccharides
  • Polysaccharides
  • Includes sugars, starches, cellulose,

2
3
Carbohydrates
  • Carbohydrates are produced in green plants in the
    presence of chlorophyll and sunlight in a process
    known as photosynthesis.
  • They serve as food sources for living organisms
    and provide the structural support for plants.
  • Many carbohydrates are large polymers composed of
    repeating units of simple sugars.

3
4
Types of Carbohydrates
Carbohydrates have the following basic
composition
  • Monosaccharides - simple sugars with multiple -OH
    groups. Based on number of carbons (3, 4, 5, 6),
    a monosaccharide is a triose, tetrose, pentose or
    hexose.
  • Disaccharides - Two monosaccharides linked by a
    covalent bond.
  • Oligosaccharides - a few monosaccharides linked
    by covalent bonds
  • Polysaccharides - polymers consisting of chains
    of multiple monosaccharide or disaccharide units.

4
5
Carbohydrates
  • Monosaccharides
  • Single (simple) sugars
  • Contain C, H, and O in a 121 ratio
  • Quick energy sources

Examples Glucose C6H12O6 Fructose
C6H12O6 Galactose C6H12O6
Fructose
Glucose
glucose
5
fructose
6
Monosaccharides
  • Empirical formula is CH2O
  • Both open chain and ring structures are possible
  • Mulitple structural isomers are possible
  • Multiple chiral carbon atoms lead to optical
    isomers
  • Monosaccharides generally have between 3 and 6
    carbon atoms
  • The most common monosaccharides are
  • Five carbons C5H10O5 - called pentoses
  • Six carbons C6H12O6 - called hexoses
  • Monosaccharide straight chains have at least one
    carbonyl group CO.
  • If the carbonyl group is at the end it is an
    aldose sugar. If it is within the chain it is a
    ketose sugar

6
7
Monosaccharides
  • Aldoses (e.g., glucose) have an aldehyde group at
    one end.

Ketoses (e.g., fructose) have a ketone group,
usually at C2.
7
8
Optical Isomers D and L Forms
  • D or dextrorotatory L or levorotatory are
    designations for optical isomers that are based
    on the configuration about the single asymmetric
    C in glyceraldehyde.
  • The lower representations are Fischer Projections.

8
9
Sugar Nomenclature
  • For sugars with more than one chiral center, D
    and L refer to the asymmetric C farthest from
    the aldehyde or keto group.
  • Most naturally occurring sugars are D isomers.

9
10
Steroisomers
  • D L sugars are mirror
  • images of one another.
  • They have the same
  • name, e.g., D-glucose
  • L-glucose.
  • Other stereoisomers
  • have unique names,
  • e.g., glucose, mannose,
  • galactose, etc.
  • The number of stereoisomers is 2n, where n is the
    number of asymmetric centers.
  • The 6-C aldoses have 4 asymmetric centers. Thus
    there are 16 possible stereoisomers (8 D-sugars
    and 8 L-sugars).

10
11
Ring Structures
  • Pentoses and hexoses can form ring structures as
    the ketone or aldehyde reacts with a distal OH.
  • Glucose forms an intra-molecular hemiacetal, as
    the C1 aldehyde C5 OH react, to form a
    6-member ring known as a pyranose ring,

These representations of the cyclic sugars are
called Haworth projections.
11
12
Fructose Ring Structures
Fructose may form either
  • a 6-member pyranose ring, by reaction of the C2
    keto group with the OH on C6, or
  • a 5-member furanose ring, by reaction of the C2
    keto group with the OH on C5.

12
13
Monosaccharides
Some examples of pyranose ring structures for
hexose sugars. The ring is not actually planar
but exists in boat and chair conformers
13
14
Sugar Derivatives
  • An Amino sugar is a sugar in which an amino
    group substitutes for a hydroxyl. An example is
    glucosamine.
  • The amino group may be converted to an amide, as
    in N-acetylglucosamine.

14
15
Anomers of Glucose
  • Cyclization of glucose produces a new asymmetric
    center at C1. The 2 stereoisomers are called
    anomers, a b.
  • Haworth projections represent the cyclic sugars
    as having essentially planar rings, with the OH
    at the anomeric C1
  • a (OH below the ring)
  • b (OH above the ring).

15
16
Glycosidic Bonds
  • The anomeric hydroxyl groups of two sugars can
    join together, splitting out water to form a
    glycosidic bond.
  • Two glucose molecules combine to form a
    disaccharide known as maltose.

16
17
Disaccharides
  • Double sugars
  • Good source of energy
  • Break down into simple sugars

Sucrose (glucose fructose) Lactose (glucose
galactose)
Other disaccharides include -- Sucrose, common
table sugar, has a glycosidic bond linking
the anomeric hydroxyls of glucose fructose.
-- Because the configuration at the anomeric C
of glucose is a (O points down from ring),
the linkage is a(1?2). The full name of
sucrose is a-D-glucopyranosyl-(1?2)-b-
D-fructopyranose.) -- Lactose, milk sugar, is
composed of galactose glucose, with b(1?4)
linkage from the anomeric OH of galactose. Its
full name is b-D-galactopyranosyl-(1? 4)-a-D-
glucopyranose
H
H
17
18
Disaccharides
  • Compare the structures of these three common
    disaccharides

H
H
  • Sucrose is an a (1-4) link between D-Glucose and
    D-Fructose
  • Lactose is an a (1-4) link between two D glucose

18
19
Polysaccharides
  • 3 or more sugars linked together
  • Complex sugars
  • Important for energy storage

Examples Starch- (plants) found in leaves,
tubers Glycogen- (animals) found in the liver
and muscles Cellulose- (plants) make up cell
walls
Starch
19
20
Polysaccharides - Starches
Reducing end
Amylose
  • Plants store glucose as amylose or amylopectin.
    Both are glucose polymers collectively called
    starch.
  • Amylose is a glucose polymer with a (1?4)
    linkages.
  • The end of the polysaccharide with an anomeric C1
    that is not involved in a glycosidic bond is
    called the reducing end.
  • Glucose storage in polymer form minimizes osmotic
    effects.

20
21
Amylopectin
Amylopectin
  • Amylopectin is a glucose polymer with mainly
    a(1?4) linkages, but it also has branches formed
    by a (1?6) linkages. Branches are generally
    longer than those shown in the diagram above.
  • The branches produce a compact structure
    provide multiple chain ends at which enzyme
    activity can occur.

21
22
Glycogen
Glycogen
  • Glycogen, the glucose storage polymer in animals,
    is similar in structure to amylopectin found in
    plants
  • Glycogen has more a (1?6) branches than
    amylopectin
  • The ability to rapidly mobilize glucose is more
    essential to animals than to plants.
  • The highly branched structure permits rapid
    glucose release from glycogen stores, e.g., in
    muscle during exercise.

22
23
Starch and Cellulose
Amylose
Cellulose
  • The essential difference between amylose starch
    and cellulose is in the glycosidic link between
    the saccharide units. Amylose has a(1-4) links.
    Cellulose has b(1-4) links.

23
24
Cellulose
  • Cellulose is the major building component of
    plant cell walls
  • Long chain of glucose molecules would be expected
    to be a great source of energy, but humans lack
    the necessary enzyme to digest cellulose
  • The Endosymbiotic Protist in cow guts DOES have
    the enzyme

24
25
Dietary Fiber
  • Dietary fiber is mainly plant material that is
    not hydrolyzed by enzymes secreted by the human
    digestive tract but may be digested by microflora
    in the gut.
  • Examples of dietary fiber include cellulose,
    hemicellulose, lignin and pectin.
  • Dietary fiber may be helpful in the prevention of
    conditions such as diverticulosis, irritable
    bowel syndrome, constipation, obesity, Crohns
    disease, hemorrhoids and diabetes mellitus.

26
Carbohydrate Functions Energy Sources
  • During metabolism animals break down
    carbohydrates to carbon dioxide and water vapor.
  • Monosaccharides and dissaccharides break down
    quickly and provide quick energy sources.
  • Starches take longer to metabolize but the end
    products are the same.
  • Human beings cannot break down cellulose, since
    we lack the appropriate enzyme to breakdown the b
    1-4 linkage


26
27
Carbohydrate Functions Storage
  • The main storage polysaccharides are starches and
    glycogen. While plants use starch as their
    storage polysaccharides, animals use glycogen.
  • When the body has a high glucose concentration,
    the pancreas releases insulin, which converts
    glucose into glycogen and stores it in the liver.
  • When the glucose concentration is low, the
    hormone glucagon converts glycogen back into
    glucose.
  • Glycogen is the primary energy reserve in human
    beings . Metabolism of glucose provides the
    energy necessary for our bodies to function and
    carry out daily activities.
  • When it is broken down into glucose and oxidized,
    ultimately to CO2 and H2O, through cellular
    respiration, large amounts of energy are
    released.


27
28
Carbohydrate Functions Structure
  • Cellulose is a major component of plant cell
    walls. It is a polymer of b-D-glucose and forms
    a very strong fiber, which is excellent building
    material in plants.
  • Cows and other ruminants have enzymes that break
    down cellulose. In humans it is primarily bulk or
    roughage.
  • Chitin is a structural polysaccharide found in
    the exoskeletons of some insects.
  • Chitin is a leather like structural substance
    that eventually hardens when it is shed.
  • Chitin is often used in medicine for sutures
    because it is both strong and flexible, but it
    also decomposes over time.


28
29
Carbohydrate Functions Precursor Molecules
  • Carbohydrates are precursors for the synthesis of
    certain biomolecules.
  • Carbohydrates (ribose) form part of the skeletons
    of nucleic acids, DNA and RNA.
  • The carbon skeletons of carbohydrates serve as
    raw material for the synthesis of other small
    organic molecules, such as amino acids and fatty
    acids.
  • Disaccharides provide building material for
    structures that protect the cell or whole
    organism.


29
30
The End
  • .

30
About PowerShow.com