BCH 451 TEST III EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS VERIFIED LATEST UPDATE GRADED A++
START LIPIDS
Define lipids
water insoluble organic molecules that typically consist of a hydrocarbon portion (often a
chain) attached to a polar group)
Lipids are ____________ and _________ diverse
structurall and functionally diverse
Name 5 lipid functions:
1) Structural components of biological membranes
2) Barriers (compartmentalize metabolites/pH/metabolic pathways)
3) Energy storage molecules
4) Vitamins
5) Chemical signals (regulation of hormones and signal transduction)
Define fatty acids. Will the head be charged at pH = 7?
long aliphatic hydrocarbon tail attached to a polar -COOH head group. FA will be
charged at pH = 7, and neutral below 4.5
How do fatty acids differ from one another?
a. length of hydrocarbon tails
b. number of C=C double bonds
c. position of double bonds in the hydrocarbon chain
d. number of branches and their position in the hydrocarbon chain
,Describe the "partitions" of a fatty acid
See notes pg 2
Fatty acid= fatty acyl group + carbonyl
Fatty acid= Hydrocarbon tail + polar head group
Aliphatic tails vary in:
1) length
2) # of C--C
3) Positions of double bonds in tail (cis versus trans bond)
4) # of branches
Why do fatty acids possess an even number of C's? Which coenzyme is used in
lipid synthesis?
Fatty acids are assembled with 2 Carbon acyl groups so they have even number of c's
in tail. coenzyme A is the coenzyme that transfers an acyl group to the growing fatty
acid chain
What is the typical length of an aliphatic tail? Even or odd number of carbons?
Why?
typically 12-20 carbons and always an even number of carbons because fatty acids are
synthesized with 2-carb units
Define "saturated FA
Tail carbons possess the maximum number of hydrogens
What are FA with no C--C double bonds?
What are FA with C--C double bonds?
,one C--C db?
multiple C--C db?
Saturated FA
Unsaturated FA
monosaturated
polysaturated
Describe the difference between cis and trans double bonds and which occurs
most prevalently in naturally occurring FAs
Cis = Carbons on same side across db; Trans= C's on opposite side across db. Cis
more prevalent
What are the consequences of fatty acid tail length
lengthening the hydrocarbon tail; higher melting point
Draw a saturated and unsaturated fatty acid
-indicate the fatty acyl group, the hydrocarbon tail, and the carboxyl
Describe the makeup of triacylglyerol (are they hydrophilic or phobic?) and draw
one
-3 fatty acid chains joined by ester bonds to glycerol; very hydrophobic
The less saturated a try glycerol, the ________ the Tm.
higher
What is the most abundant lipid in most biological membranes?
Glycerophospholipids
how are Glycerophospholipids similar to triacylglycerols?
, Glycerophospholipids have 2 FA chains instead of 3, and they have a linked phosphate
group with attached variable functional group
What are the variable regions of glycerophospholipids?
the length of the fatty acid chain, its saturation, and the functional group of the attached
functional group to the phosphate (which can change the chemistry of the polar head
group)
What is the second most abundant lipid in animal and plant membranes?
Sphingolipids
Draw sphingosine. What is it in the structure of a sphingolipid? How many
carbons are found in this lipid?
The backbone. 27 carbons
At what position can variable groups be attached to a sphingostine molecule?
Attached functional groups at C1, replacing the OH, and at C2, replacing the amine
group, add variability to the sphingosine's structure
Where are sphingolipids important in the body?
the membranes of nerve cell membranes and myelin sheaths (cerebrosides,
gangliosides, and sphingomyelins)
How many rings and carbon atoms are found in cholesterol?
4 rings and 27 carbons
What do steroids have in common? What is the structural significance of this
common structure?
All steroids have basic 4 ring structure with 3 six membered rings and 1 five membered
ring. the four ring structure makes the steroids flat planes
COMPLETE SOLUTIONS VERIFIED LATEST UPDATE GRADED A++
START LIPIDS
Define lipids
water insoluble organic molecules that typically consist of a hydrocarbon portion (often a
chain) attached to a polar group)
Lipids are ____________ and _________ diverse
structurall and functionally diverse
Name 5 lipid functions:
1) Structural components of biological membranes
2) Barriers (compartmentalize metabolites/pH/metabolic pathways)
3) Energy storage molecules
4) Vitamins
5) Chemical signals (regulation of hormones and signal transduction)
Define fatty acids. Will the head be charged at pH = 7?
long aliphatic hydrocarbon tail attached to a polar -COOH head group. FA will be
charged at pH = 7, and neutral below 4.5
How do fatty acids differ from one another?
a. length of hydrocarbon tails
b. number of C=C double bonds
c. position of double bonds in the hydrocarbon chain
d. number of branches and their position in the hydrocarbon chain
,Describe the "partitions" of a fatty acid
See notes pg 2
Fatty acid= fatty acyl group + carbonyl
Fatty acid= Hydrocarbon tail + polar head group
Aliphatic tails vary in:
1) length
2) # of C--C
3) Positions of double bonds in tail (cis versus trans bond)
4) # of branches
Why do fatty acids possess an even number of C's? Which coenzyme is used in
lipid synthesis?
Fatty acids are assembled with 2 Carbon acyl groups so they have even number of c's
in tail. coenzyme A is the coenzyme that transfers an acyl group to the growing fatty
acid chain
What is the typical length of an aliphatic tail? Even or odd number of carbons?
Why?
typically 12-20 carbons and always an even number of carbons because fatty acids are
synthesized with 2-carb units
Define "saturated FA
Tail carbons possess the maximum number of hydrogens
What are FA with no C--C double bonds?
What are FA with C--C double bonds?
,one C--C db?
multiple C--C db?
Saturated FA
Unsaturated FA
monosaturated
polysaturated
Describe the difference between cis and trans double bonds and which occurs
most prevalently in naturally occurring FAs
Cis = Carbons on same side across db; Trans= C's on opposite side across db. Cis
more prevalent
What are the consequences of fatty acid tail length
lengthening the hydrocarbon tail; higher melting point
Draw a saturated and unsaturated fatty acid
-indicate the fatty acyl group, the hydrocarbon tail, and the carboxyl
Describe the makeup of triacylglyerol (are they hydrophilic or phobic?) and draw
one
-3 fatty acid chains joined by ester bonds to glycerol; very hydrophobic
The less saturated a try glycerol, the ________ the Tm.
higher
What is the most abundant lipid in most biological membranes?
Glycerophospholipids
how are Glycerophospholipids similar to triacylglycerols?
, Glycerophospholipids have 2 FA chains instead of 3, and they have a linked phosphate
group with attached variable functional group
What are the variable regions of glycerophospholipids?
the length of the fatty acid chain, its saturation, and the functional group of the attached
functional group to the phosphate (which can change the chemistry of the polar head
group)
What is the second most abundant lipid in animal and plant membranes?
Sphingolipids
Draw sphingosine. What is it in the structure of a sphingolipid? How many
carbons are found in this lipid?
The backbone. 27 carbons
At what position can variable groups be attached to a sphingostine molecule?
Attached functional groups at C1, replacing the OH, and at C2, replacing the amine
group, add variability to the sphingosine's structure
Where are sphingolipids important in the body?
the membranes of nerve cell membranes and myelin sheaths (cerebrosides,
gangliosides, and sphingomyelins)
How many rings and carbon atoms are found in cholesterol?
4 rings and 27 carbons
What do steroids have in common? What is the structural significance of this
common structure?
All steroids have basic 4 ring structure with 3 six membered rings and 1 five membered
ring. the four ring structure makes the steroids flat planes
