Cell Chemistry (III)
Functional Groups
Polysaccharides
Lipids
KNOW & Be Able to Identify
These Functional Groups
Polysaccharides
 Examples of polysaccharides
 Glycogen: In animal cells (meats)
 Starch: In plant cells
 Cellulose: In plant cells
 Composition of polysaccharides
 Glucoses (several) joined by covalent bonds
 Polysaccharides are POLYMERS of Glucose
 The bonds between the many glucose molecules
are synthesized by a type of chemical reaction
called --- ???
 These bonds can be broken by a type of
chemical reaction called --- ???
Glycogen: A Polysaccharide
Significance of Polysaccharides in
Physiology (I)
 Polysaccharides function as stored fuel, in both plant
cells and animal cells.
 Any excess fuel that is not burned (or --- ?? is
stored, first, in the form of glycogen, a
polysaccharide, and then in the form of
triglycerides (or neutral fats) in adipocytes.
 In humans, the organs and tissues rich in glycogen
are: Liver cells (Hepatocytes) and muscle cells
 In animal cells, there is a limit to the amount of
glycogen that can be stored by ---? and ---? When
the glycogen storage capacity is filled, all additional
fuels are metabolized to triglycerides and stored in
fat cells, also called --- ?
Significance of Polysaccharides in
Physiology (II)
 What is the advantage of storing fuel?
 When monosaccharides are not available (as in
hours after a meal or during fasting), the cells
can --- ?? the polysaccharides/oligosaccharides
of the disaccharides to get the monosaccharides.
 Fill-in blank spaces with correct term
 Polysaccharide --??-- Monosaccharides
 Glycogen --?? ???
 What happens to Cellulose consumed by
humans and animals? Can cells burn or --- ??
polysaccharides?
LIPIDS
 Fatty acids, triglycerides,
phospholipids, steroids and
eicosanoids are all examples of lipids.
 Significance of lipids:
 They function as fuels, stored fuel,
structural components of cell membranes
and hormones.
Fatty Acids
 Chemistry
 Contain even # of C atoms
 Most contain 16 to 20 C atom
 Examples: Palmitate (C16), Stearate (C18)
Oleate (C18, 1db)
 Contain a carboxyl group at one end
 May be classified as:
 1)
 2)
Saturated (meaning??)
Unsaturated (meaning ??)
 Property:
 Characterized as amphipathic, meaning that one
small region is ---? While the other region is ---??
Significance of Free Fatty Acids
 Free fatty acids (FFAs) are, with Glycerol,
building blocks of triglycerides (or fats)
 Margarine is a significant dietary source
of FFAs
 Using dehydration synthesis reaction (or
condensation reaction), cells covalently
bind three free fatty acids (FFA), one to
each C atom of glycerol.
 Illustrated in next slide
Synthesis of Triglycerides
Triglyceride Composition &
Synthesis
 As illustrated in previous slide, a
triglyceride consists of:
 Three FFA covalently bonded to
 One Glycerol
 The FAs are covalently linked by a
chemical reaction called ---?
 Their chemical property:
Hydrophobic
Significance of Triglycerides in
Physiology
 Triglycerides are “stored fuel”. When
hepatocytes and muscle cells can no longer
store glycogen, the excess fuel is stored as
triglycerides in cells called adipocytes.
 Adipocytes form a type of connective
tissue called adipose tissue.
 There is no limit to the amount of
triglyceride that can be stored by this tissue
YOU Should be able to
1. Draw the chemical structure of a FFA
2. Be able to tell the difference between
saturated and unsaturated FFA
 Questions
1. Complete hydrolysis of a triglyceride
yields what product/ or products?
2. Complete oxidation of a FFA by cellular
respiration yields what product or
products?
Triglycerides or triacylglycerols
 They are commonly known as fats
 In humans and other vertebrates
triglycerides are stored in adipocytes.
 Adipocytes are cells that form a type of
connective tissue called adipose tissue
 When ---?? storage capacity of --?? and -?? is reached, all excess fuel is stored as
triglycerides
Remember that:
 Preferred fuels: Monosaccharides
 When not immediately available cells
hydrolyze polys to get monos
 When no more monos are available
cells start using free fatty acids
(FFA).
 Fill-in the blank spaces with correct term
 To get FFAs, cells must --- triglycerides
to --- + ---??
Significance of phospholipids in
physiology
 They are structural components of all
cell membranes
 The plasma membrane (PM), the ER,
the membranes around the
mitochondria and the lysosomes are
composed of a phopholipid bilayer
(plus cholesterol and proteins)
 Phospholipids are amphipathic
Phospholipids:Chemistry
 Property: Amphipathic
 Composition




Glycerol
2 fatty acids
Phosphate group
“X” group attached to phosphate
 Phospholipids are structurally closest
to what other lipid ---??
Structure of a Phospholipid and a
Steroid
Steroids
Cholesterol
Androgens (i.e., testosterone)
Estrogens (i.e.,
Glucocorticoids (i.e.,
Mineralocorticoids
(like Aldosterone)
Vitamin D
Significance of Steroids in
Physiology
 Cholesterol is the classic example of a
steroid
 It is the starting material for
synthesis of androgens-(male
hormones), estrogens (female
hormones), glucocorticoids, bile
acids, bile salts and Vit. D
 Chemical property: Amphipathic
Some Questions ??
 Assume that this is a gene: ….-5’-ATGCAATCAGTC-….
1. What is the sequence of the complementary strand?
2. These two strands would be joined by what bonds
…Assume that the 3-’strand is the gene.
1. What is the sequence of the mRNA from that gene?
2. How many codons are there in that mRNA?
 Write each codon on a separate line in your notes
3. What would be the corresponding seqence of the
anticodons?
4. Which RNA has anticodons?
5. According to the genetic code, what is the AAS of the
peptide from that gene?
The end
Functional groups
Polysaccharides
Lipids