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Biochemistry > Chapter 10 (Exam 1 - in depth) > Flashcards

Chapter 10 (Exam 1 - in depth) Flashcards

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1
Q

Why are carbohydrates named?

A

Because many have the formula Cn(H2O)n.

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2
Q

What can carbohydrates be covalently linked with?

A

Proteins and lipids.

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3
Q

What functions do carbohydrates fulfill?

A

Energy source and energy storage.
Structural component of cell walls and exoskeletons.
Informational molecules in cell-cell signaling.
Cellular identification.

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4
Q

What are monosaccharides?

A

Aldehydes or ketones that contain 2+ alcohol groups.

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5
Q

What are the smallest monosaccharides composed of?

A

3 carbons.

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6
Q

What is the basic nomenclature for naming carbohydrates?

A

Number of carbon atoms in the carbohydrate + -ose.
Example: three carbon = triose.

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7
Q

What are the common functional groups?

A

All carbohydrates initially had a carbonyl functional group.
Aldehydes = aldose.
Ketones = ketose.

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8
Q

What are the many isomeric forms monosaccharides exist in?

A

Isomers, constitutional isomers, stereoisomers, enantiomers, and diastereoisomers.
Epimers, anomers, diastereoisomers.

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9
Q

What are isomers?

A

Have the same molecular formula but different structure.

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10
Q

What are constitutional isomers?

A

Differ in the order of attachment of atoms.

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11
Q

What are enantiomers?

A

Stereoisomers that are nonsuperimposable mirror images.

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12
Q

What are stereoisomers?

A

Atoms are connected in the same order but differ in spatial arrangement.

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13
Q

What are diastereoisomers?

A

Isomers that are not mirror images.

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14
Q

What are epimers?

A

Differ at one of several asymmetric carbon atoms.

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15
Q

What are anomers?

A

Isomers that differ at a new asymmetric carbon atom formed on ring closure.

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16
Q

What are the common monosaccharides?

A

D-Ribose, D-Deoxyribose, D-Glucose, D-Mannose, D-Galactose, D-Fructose

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17
Q

What are the common carbohydrates in biochemistry?

A

Ribose, Glucose, Galactose, Mannose, Fructose.

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18
Q

What is ribose?

A

Standard 5-carbon sugar.

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19
Q

What is glucose?

A

Standard 6-carbon sugar.

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20
Q

What is galactose?

A

Epimer of glucose.

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21
Q

What is mannose?

A

Epimer of glucose.

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22
Q

What is fructose?

A

Ketose form of glucose.

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23
Q

What are D and L isomers of a sugar called?

A

Enantiomers.

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24
Q

What are most hexoses in living organisms?

A

D stereoisomers.

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25
What form does L-arabinose occur in?
The L form.
26
What are D-Mannose and D-galactose?
Both epimers of D-glucose. Each epimer differs from D-glucose in the configuration at one chiral center.
27
Where do D-Mannose and D-galactose vary at?
More than one chiral center and are diastereomers, but not epimers.
28
How do many common sugars exist in cyclic forms?
Chemical basis for ring formation is that an aldehyde can react with an alcohol to form a hemiacetal, whereas a ketone can react with an alcohol to form a hemiketal.
29
What do pentoses and hexoses readily undergo?
Intramolecular cyclization.
30
What is the anomeric carbon?
New chiral center that the former carbonyl carbon becomes.
31
What determines if the anomer of a monosaccharide is alpha or beta?
The position of the group when the former carbonyl oxygen becomes a hydroxyl group.
32
When is the configuration of a monosaccharide alpha?
If the hydroxyl group is on the opposite side (trans) of the ring as the CH2OH moiety.
33
When is the configuration of a monosaccharide beta?
If the hydroxyl group is on the same side (cis) of the ring as the CH2OH moiety.
34
Do pentoses and hexoses readily undergo intramolecular cyclization?
Yes.
35
What are 6-membered oxygen-containing rings called?
Pyranoses, after the pyran ring structure.
36
What are 5-membered oxygen-containing rings called?
Furanoses, after the furan ring structure.
37
What side is the anomeric carbon usually drawn on?
The right side.q
38
What does fructose form?
The pyranose form, which predominates when fructose is free in solution, and a furanose form, commonly seen in fructose derivatives.
39
What does a solution of glucose contain?
One-third alpha anomer, two-thirds beta anomer, and about 1% open chain.
40
Why does the free open chain of glucose react with oxidizing agents?
Because the 2 anomeric forms are in equilibrium that passes through an open chain form.
41
What are reducing sugars?
Sugars that react with oxidizing agents.
42
What are nonreducing sugars?
Sugars that do not react with oxidizing agents.
43
What is an O-glycosidic bond?
Bond formed between the anomeric carbon atom and a hydroxyl group of another molecule.
44
What is the glycoside?
Produce of an O-glycosidic bond.
45
What is a N-glycosidic bond?
Bond formed between the anomeric carbon atom and an amine.
46
What do carbohydrates form?
Ester linkages to phosphates.
47
When does phosphorylation of sugars occur?
Routinely during metabolism.
48
What are the common disaccharides?
Sucrose, lactose, and maltose.
49
What do enzymes on the outer surface of intestinal epithelium do?
Cleave common disaccharides.
50
What do sucrase, lactase, and maltase cleave?
Sucrase cleaves sucrose (table sugar). Lactase cleaves lactose (milk sugar). Maltase cleaves maltose.
51
How many units do oligosaccharides consist of?
5 - 15 units typically.
52
Where are oligosaccharides not commonly found?
Free in cells.
53
What are oligosaccharides usually attached to?
Proteins.
54
What is a glycoprotein?
Protein with small oligosaccharides attached.
55
What type of proteins are glycoproteins?
About half of mammalian proteins.
56
How is a carbohydrate attached to amino acids on the protein?
Via its anomeric carbon.
57
How can attachments to proteins be linked?
N-linked (through asparagine) or O-linked (through serine or threonine).
58
Where are O-linked sugars and N-linked sugars attached?
O-linked sugars: added in Golgi. N-linked sugars: starts in ER and then completed in the Golgi.
59
What do oligosaccharides function as?
Markers: - Identity markers - Destination markers.
60
What are natural carbohydrates usually found as?
Polymers.
61
What can polysaccharides be?
Homopolysaccharides (one monomer unit). Heteropolysaccharides (multiple monomer units). Linear (one type of glycosidic bond). Branched (multiple types of glycosidic bonds).
62
Why do polysaccharides do not have a defined molecular weight?
This is in contrast to proteins because, unliked proteins, no template is used to make polysaccharides. Polysaccharides are often in a state of flux; monomer units are added and removed as needed by the organism.
63
What types of homopolysaccharides?
Unbranched and branched.
64
What are heteropolysaccharides?
Two monomer types, unbranched, and multiple monomer types, branched.
65
What is glycogen?
A branched homopolysaccharide of glucose.
66
What do glucose monomers form?
alpha1 --> 4 linked chains. There are branch points with alpha1 --> 6 linkers every 8 - 12 residues.
67
What is the molecular weight of glycogen?
Reaches several millions.
68
What does glycogen function as?
Main storage polysaccharide in animals.
69
Where is glycogen mostly found?
In muscles and liver.
70
What are the common homopolymers of glucose?
Glycogen, starch, and cellulose.
71
What is starch?
Mixture of 2 homopolysaccharides of glucose.
72
What is amylose?
Unbranched polymer of alpha1 --> 4 linked residues.
73
What is amylopectin?
Branched like glycogen, but the branch points with alpha1 --> 6 linkers occur every 24 - 30 residues.
74
What is the molecular weight of amylopectin?
Up to 200 million.
75
What is starch in plants?
The main storage polysaccharide.
76
Why are glycogen and starch insoluble?
Due to their high molecular weight and often form granules in cells.
77
What do granules contain?
Enzymes that synthesize and degrade these polymers.
78
What do glycogen and amylopectin have?
One reducing end, but many nonreducing ends.
79
When does enzymatic processing occur?
Simultaneously in many nonreducing ends.
80
What is cellulose?
A linear homopolysaccharide of glucose.
81
What do glucose monomers in cellulose form?
Beta1 --> 4 linked chains.
82
What type of structure does cellulose have?
Tough and water insoluble.
83
What is the most abundant polysaccharide in nature?
Cellulose.
84
What is cotton?
A nearly pure fibrous cellulose.
85
Why is cellulose a difficult substrate to act upon?
The fibrous structure and water insolubility.
86
Why do most animals not use cellulose as a fuel source?
They lack the enzyme to hydrolyze Beta1 --> 4 linkages.
87
What secretes cellulase and why?
Fungi, bacteria, and protozoa. Allows them to use wood as a source of glucose.
88
How do ruminants and termites live?
Symbiotically with microorganisms that produce cellulase and are able to absorb the freed glucose into their bloodstreams.
89
What do Beta1,4 linkages favor?
Straight chains, which are optimal for structural purposes.
90
What do Alpha1,4 linkages favor?
Bent structures, which are more suitable for storage.
91
What is the structure of bacterial cell walls.
Linear polysaccharide chains are cross-linked by short peptides, pentaglycines, and tetrapeptides.
92
What do bacterial cell walls consist of?
Peptidoglycans.
93
What do bacteria cell walls contain?
D-amino acids. The cross-links of them are made by a mechanism different from the regular protein sythesis.
94
What is Glycopeptide transpeptidase?
Enzyme involved in the formation of cross-links.
95
What does Penicillin react with?
The active center of transpeptidase, and form an inactive complex, which is indefinitely stable. Penicillin is irreversible suicide inhibitor of transpeptidase.
96
What is Chitin?
Linear homopolysaccharide of N-acetylglucosamine.
97
What do N-acetylglucosamine monomers form?
Beta1 --> 4 - linked chains.
98
What does chitin form?
Extended fibers that are similar to those of cellulose.
99
Where is chitin found?
In cell walls in mushrooms and in exoskeletons of insects, spiders, crabs, and other arthropods.

Biochemistry (18 decks)

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