Biochemistry Exam 4
What is amylose?
(a1--4)Glc Linear left handed spiral
What is amylopectin?
(a1-->4)Glc with (a1-->6) every 24-30 residues -2nd component of starch - up to 1,000,000 residues
What is are the bonds in Glycogen
(a1-->4)Glc with (a1-->6) every 8-12 residues -up to 50,000
What are the bonds in cellulose?
(b1-->4)Glc -Linear -Up to 15,000 residues
What are the bonds in chitin?
(b1-->4)GlcNAc
What are some of the structural and functional differences between homopolysaccharides and heteropolysaccharides?
*Homo -Contains only a single monomeric species. -Fuel storage: starch, glycogen -Structural elements: Chitin (animal exoskeleton) and Cellulose (Plant cell wall). *Hetero - Contains two or more species. - Extracellular support: Peptidoglycan ( Bacterial cell envelope) and matrix.
What physical changes allow scientist to determine the melting points of DNA strands with different nucleotide compositions.
- Increase UV absorption found in ssDNA -This is the hyperchromatic effect.
What types of non-covalent interactions contributes to the stability of the double helix?
-Base Stacking -Hydrogen Bonding
Which bonds and interactions are affected during denaturation of DNA?
-H-bonds and Base Stacking -NO covalent bonds are broken.
What is the steps in naming carbohydrates?
-Nonreducing end to the left - alpha or beta position of the bond -Five or six member ring - Carbon bond is indicated in parenthesis with arrow
What are some of the functions of various nucleotides and polynucleotides in living cells?
-Serve as structural components of enzyme co-factors -Alter the equilibria of chemical reactions. -Carry metabolic energy -Serve as intracellular signaling molecules.
Number 26
........
What chemical property of glycosaminoglycans contributes to their role as lubricants?
............
What are the similarities and differences between cellulose and chitin?
.............
Which of the following are reducing sugars? Maltose, Lactose, Sucrose?
.............
What is the minimum length of mRNA required to code a polypeptide chain of 80 amino acid residues?
240 nucleotides.
What percentage of starch is amylose?
50%
Definition of Peptidoglycan.
A major component of bacterial cell walls. Generally consists of parallel heterpolysaccarides cross linked by short peptides.
How does the R-group of Serine make it a good amino-acid for connecting to a carbohydrate moiety?
A sugar residue at the reducing end of the linker can be joined by its anomeric carbon to the hydroxyl of the serine residue.
What bases are found in DNA?
A-T G-C
Which of chargaffs rules was the most important clue leading to the model postulated by watson and crick?
A-T C-G
What bases are found in RNA?
A-U G-C T can occasionally be found in RNA
What is the compound that consists of ribose linked by an N-B-glycosidic bond to N-9 of Adenine?
Adenosine
What is needed to have reducing power?
Aldehyde
What are the two components of starch?
Amylose and Amylopectin
Where is starch stored?
Chloroplast and amyloplast.
Describe the common features and differences of maltose and sucrose.
Common: -Disaccarides Differences: Maltose has two (α1-->4) linked D-glucose units. sucrose has (α1<-->2ß) linked D-glucose and D-Fructose.
Describe the common features and differences of cellulose and glycogen.
Common: -Polymers of D-glucose Difference: -In glycosidic linkage (ß1-->4) Cellulose. (α1-->4) Glycogen.
Which bonds must be broken to convert one "chair" form of D-glucose to the other?
Conversion between chair confirmations does NOT require bond breakage. This the critical distinction between CONFIGURATION and CONFORMATION.
Where is glycogen stored?
Cytosol of liver and skeletal muscle in glycogen granules.
T or F? A-form and B-form of DNA are right handed helices but z-form DNA is a left handed helix found only in ssDNA.
False
T or F? GqC pairs with three glycosdic bonds.
False
T or F? Nucleotide sequence has little or no affect on which form DNA takes.
False
T or F? The Dideoxy method of sequencing DNA can be used on B-DNA but not Z-DNA
False
T or F? The phosphodiester bonds that link adjacent nucleotides are uncharged under physiological conditions.
False
T or F? The two strands of DNA are aligned as parallel strands.
False
What contributes to the structural rigidity of cellulose?
Glucose polymers are stabilized by hydrogen bonding.
What is maltose?
Glucose+Glucose
What is another name for polysaccharides?
Glycans
Does glycogen or amylopectin have a higher degree of branching? Which one is more compact?
Glycogen
What type of carbohydrate is Heprin?
Glycosaminoglycan
What are the most important noncovalent bonds or interactions in cellulose?
Hydrogen bonding between neighboring chains.
How does lysozyme act as a first defense against bacterial infection?
Lysozyme kills bacteria by hydrolyzing the (B1-->4) glycosidic bond between N-acetylglucosamine and N-acetylmuramic acid. Thus allowing cellular swelling.
what is the disaccaride produced when amylase breaks down starch?
Maltose
Suggest a convenient way to determine the rate of hydrolysis of sucrose by an enzyme preparation extracted from the lining of the small intestine.
Measure the change of the optical rotation with time.
Definition of glycolipids.
Membrane lipids in which the hydrophillic head groups are oligosaccarides.
What is GlcNAc?
N-acetylglucosamine
Do ketoses have reducing power?
NO
Does sucrose have reducing power?
NO
Is D-2-deoxygalactose the same chemical as D-2-deoxyglucose?
NO glucose and galactose differ at C-4.
What are the constituents and bonds of nucleosides?
Nitrogenous base + Pentose sugar Glycosyl bonds: N-1 of pyrimidines to C1 N-9 of Purines to C1
What are the constituents and bonds of nucleotides?
Nitrogenous base+ Pentose Sugar+ Phosphate Glycosyl Bonds: N-1 of pyrimidines to C1 N-9 of Purines to C1 Phosphate esterified to 5`Carbon
Definition of glycoproteins.
One or several oligosaccarrides of varying complexity joined covalently to a protein.
What type of linkages connect oligosaccharides to proteins?
PG 255
How does penicillin combat bacterial infections?
Penicillin kill bacteria by preventing synthesis of the cross-links, leaving the cell too weak to resist osmotic lysis.
Why is RNA sensitive to alkaline hydrolysis?
RNA can undergo base catalysis because of the free hydroxyl group on the 2`Carbon.
Are free bases soluble in water?
Relatively insoluable.
What are the functions of DNA?
Storage and transmission of genetic information
Lactose exists in two anomeric forms, but no anomeric forms of sucrose have been reported. why?
Sucrose has no free anomeric carbon to undergo mutarotation.
Which bonds in α-D-glucose must be broken to change its configuration to ß-D-glucose?
The bond between C-1 and the hydroxyl on C-5.
What is reduced and what is oxidized in the reaction between a monosaccharide and a ferric ion?
The carbonyl carbon is oxidized to a carboxyl group, the cupric ion is reduced.
Which bonds must be broken to convert D-glucose to D-Mannose?
The hydrogen or the OH on the C-2.
What contributes to the mucus properties of some carbohydrates such as heperin?
The negative charge at physiological pH makes it highly polar and highly hydrated.
Explain why, in the food industry an equimolar mixture of D-glucose and D-fructose formed by hydrolysis of sucrose is called invert sugar.
The optical rotation of the mixture is negative "inverted" related to that of the sucrose solution.
How does cellulose interact to form a rigid structure?
The straight chains interact via hydrogen bonds.
T or F? A form DNA is shorter and has a larger diameter then the B-form DNA
True
T or F? A pyrimidine in one strand of DNA always hydrogen bonds with a purine in the opposite strand.
True
T or F? All the monosaccaride unites of DNA lack on OH at C2
True
T or F? B-form DNA predominates in aqueous solution: dehydration favors the A form.
True
T or F? Deoxyribose is bound to the nitrogenous base at C1.
True
T or F? Hyaluronan is a heteropolysaccharide?
True
T or F? Palindromic sequences can potential form cruciform structures.
True
T or F? The phosphodiester bonds that link adjacent nucleoties join the 3` hydroxyl of one nucleotide to the 5` hydroxyl of the next.
True
What are the two types of acidic sugars?
Uronic (oxidized at carbon 6) Aldonic (oxidation of carbonyl carbon)
Is DNA soluble in water?
Yes
what is a glycoside?
a carbohydrate in which the -OH of the anomeric carbon is replaced by -OR
Maltose chemical name
a-D-glycopyranosyl-(1-->4)-D-glycopyranose
Sucrose chemical name?
a-D-glycopyranosyl-(1<-->2)-b-D-Fructofuranoside
what composes the backbone of DNA and RNA?
alternating phosphate and pentose residues.
What makes an amino sugar?
amino group at C-2
Definition of proteoglycans.
are macromolecules of the cell surface or the extra-cellular matrix in which one or more glycosaminoglycan chains are joined covalently to a membrane protein or a secreted protein.
Lactose Chemical name?
b-D-glactopyranosyl-(1-->4)-b-D-glycopyranose
What type of linkages does cellulose have?
beta
Why is cAMP a second messager?
cAMP transmits an extracellular signal into an intracellular signal.
Where is cellulose found?
in the cell walls of plants
What does Heprin do?
inhibits blood clotting.
what is the function of tRNA
it is can adaptor molecule that translates information from mRNA into specific amino acid sequences.
Are proteoglycans mainly carbohydrates or protein?
mainly carbohydrates.
is glycoproteins mainly carbohydrates or mainly protein?
mainly protein.
What makes a sugar acidic?
one or more carboxyl groups at C-1 and C-6
What is the function of rRNA
protein synthesis
what is the function of mRNA
to carry genetic transcript to the ribosome for translation.