Transcript Lecture 6 part 2 Carbohydrates

Lecture 7
Carbohydrates
Page43
• Carbohydrates are compounds containing
carbon, hydrogen and oxygen, with hydrogen
and oxygen present in the same ration as in
water ie H2O. They include sugars (eg glucose,
fructose, sucrose) and starches (eg amylose,
amylopectin).
3.4 Monosaccharides are the simplest carbohydrates
• Carbohydrates range from small sugar
molecules (monomers) to large polysaccharides
– Sugar monomers are monosaccharides, such as
glucose and fructose
– These can be hooked together to form the
polysaccharides
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• Common carbohydrates:
– Sugar
– Starch
• Naming:
– Normally have “sacchar-” or “-ose” in their name
– Ex: glucose, dextrose
Carbohydrates
• Hydrophilic molecules
• General formula (CH2O)n
n = # of carbon atoms
Ex: glucose
n=6
C6H12O6
• 2:1 ratio of hydrogen to oxygen
3.4 Monosaccharides are the simplest carbohydrates
• The carbon skeletons of monosaccharides vary
in length
– Glucose and fructose are six carbons long
– Others have three to seven carbon atoms
• Monosaccharides are the main fuels for cellular
work
– Monosaccharides are also used as raw materials to
manufacture other organic molecules
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Carbohydrate Monomers
• Monosaccharide = simple sugar
– Glucose (blood sugar)
– Fructose (fruits)
– Galactose (component of lactose – milk)
– Ribose (RNA)
– Deoxyribose (DNA)
Glucose
(an aldose)
Fructose
(a ketose)
Structural
formula
Abbreviated
structure
Three representations of the ring form of glucose
Simplified
structure
Carbohydrates
• Contain carbon, hydrogen, and oxygen
• Their major function is to supply a source of
cellular food
• Examples:
– Monosaccharides or simple sugars
Figure 2.14a
3.5 Cells link two single sugars to form disaccharides
• Two monosaccharides (monomers) can bond to
form a disaccharide in a dehydration reaction
– An example is a glucose monomer bonding to a
fructose monomer to form sucrose, a common
disaccharide
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Glucose
Glucose
Glucose
Glucose
Maltose
Important disaccharides
• Disaccharides = sugars composed of two
monosaccharides
– Sucrose (table sugar) = glucose + fructose
– Lactose (milk sugar) = glucose + galactose
– Maltose (malt beverages & germinating wheat)
= glucose + glucose
Carbohydrates
• Disaccharides or double sugars
Figure 2.14b
• Polysaccharides = long chains of glucose
(MW 500,000 ~ glucose MW= 180)
– Glycogen (animal energy storage)
– Starch (plant product)
– Cellulose (plant product)
3.7 Polysaccharides are long chains of sugar units
• Polysaccharides
• are polymers of monosaccharides
– They can function in the cell as a storage molecule
or as a structural compound
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3.7 Polysaccharides are long chains of sugar units
• Starch is a storage polysaccharide composed of
glucose monomers and found in plants
• Glycogen is a storage polysaccharide composed
of glucose, which is hydrolyzed by animals when
glucose is needed
• Cellulose is a polymer of glucose that forms
plant cell walls
• Chitin is a polysaccharide used by insects and
crustaceans to build an exoskeleton
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3.7 Polysaccharides are long chains of sugar units
• Polysaccharides are hydrophilic (water-loving)
– Cotton fibers, such as those in bath towels, are
water absorbent
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Starch granules in
potato tuber cells
Glycogen
granules
in muscle
tissue
STARCH
Glucose
monomer
GLYCOGEN
CELLULOSE
Cellulose fibrils in
a plant cell wall
Hydrogen bonds
Cellulose
molecules
Starch
• Energy storage polysaccharide of plants
• Created during photosynthesis
Starch granules in
potato tuber cells
STARCH
Glucose
monomer
Glycogen
• Polysaccharide for energy storage
• Long, branching glucose polymer
• Made in liver, muscle, brain, uterus, and
vaginal cells
Glycogen
granules
in muscle
tissue
GLYCOGEN
Carbohydrates
• Polysaccharides or polymers of simple sugars
PLAY
Polysaccharides
Figure 2.14c
Cellulose
• Structural polysaccharide of plants
• Gives strength to the plant cell wall
– Wood, cotton, paper
• Most abundant organic compound on earth
• Humans have no enzymes to digest
cellulose
• Cellulose is present in the diet, however it
cannot be digested, thus no nutrients are
received from it
• It is beneficial – it can swell with water and
help move other materials thru the
intestine
• “fiber”, “roughage”, “bulk”
CELLULOSE
Cellulose fibrils in
a plant cell wall
Hydrogen bonds
Cellulose
molecules
Carbohydrates
• Source of energy that can be quickly mobilized
• Carbs are digested/converted to glucose,
glucose is used to produce ATP (energy source
for the cell)
• Carbohydrates can have other functions
outside of energy
Conjugated Carbohydrates
• Conjugated = covalently bound to proteins
and/or lipids
• Glycolipid = carbohydrate + lipid
• Glycoprotein = carbohydrate + protein
– Roles on the external surface of the cell’s
membrane (receptors, signals)
– Component of mucus
• Protect the GI tract, traps particles in the respiratory
tract, prevents infections
Proteoglycans
• Macromolecule with a dominant carbohydrate
and a smaller protein component
– Gel that holds cells and tissues together
– Lubricates joints
– Rubbery, tough texture of cartilage
– Gelatinous filler in the umbilical cord and eye
Cellular respiration generates ATP energy for
cells
– Cellular respiration breaks down glucose molecules
and stores their energy in ATP
– Some energy lost as heat (2nd law of thermodynamics)
C6H12O6
Glucose
+
O2
6
Oxygen gas
Figure 6.3
6
CO2
Carbon
dioxide
+
6
H2O
Water
+
ATPs
Energy
When glucose is converted to carbon dioxide
•
It loses hydrogen atoms, which are added to
oxygen, producing water
Loss of hydrogen atoms
(oxidation)
C6H12O6 +
6 O2
6 CO2
Glucose
6 H2O
+
Energy
(ATP)
Gain of hydrogen atoms
(reduction)
Figure 6.5A
+
– Glucose loses hydrogen atoms = oxidization
(oxidation is loss)
– Oxygen gains hydrogen atoms = reduction
(reduction is gain)
– “OIL RIG”
Loss of hydrogen atoms
(oxidation)
C6H12O6 +
6 O2
6 CO2
Glucose
6 H2O
+
Energy
(ATP)
Gain of hydrogen atoms
(reduction)
Figure 6.5A
+
Thank you