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77 terms

Cell Biology Ch.3

Cell Bio Test
STUDY
PLAY
The right-handed Watson-Crick helix is the _________, the main form of DNA in cells
B-DNA
There are two other biologically active double helical structures
A-DNA and Z-DNA
_________ has a right handed helical configuration that is thicker and shorter than B-DNA
A-DNA
__________ is a left handed double helix that is a zigzag pattern that has a longer, thinner sugar-phosphate backbone
Z-DNA
RNA structure also depends on __________, but this pairing is usually between complementary regions within the same RNA strand and is much less than with DNA
base pairing
Of the various RNA species (rRNA, mRNA, tRNA), the secondary and tertiary structures are only well understood for _________ molecules
tRNA
_________ are long-chain polymers of sugars and sugar derivatives
Polysaccharides
Two major forms of polysaccharides are:
1. Storage polysaccharides (starch & glycogen)
2. Structural polysaccharides (cellulose)
Many polysaccharides may contain a single type of _________ monomeric unit, but some may have an alternating pattern of two kinds
repeating
Repeating units that form polysaccharides are simple sugars called
monosaccharides
What are the 2 categories of sugars
Aldosugars and Ketosugars
________ is a category of sugars with a terminal carbonyl group
Aldosugars
_________ is a category of sugar with an internal carbonyl group
Ketosugars
Within the 2 general categories of sugars, the sugars are named generically according to the number of carbon atoms they contain (most have 3 to 7)
Triose (3 carbons)
Tetrose (4 carbons)
Pentose (5 carbons)
Hexose (6 carbons)
Heptose (7 carbons)
The most common monosaccaride is
D-glucose (aldohexose)
The formula CnH2nOn is characteristic of sugars because these compounds were originally thought of as
Hydrates of carbon (Cn(H20)n
keeping with the general rule for numbering carbon atoms in organic molecules, the carbons of glucose are numbered beginning with the most _________ end of the molecule (aldehyde group)
oxidized
Glucose has 16 possible stereoisomers, so it has how many assymetric carbons?
4
The _______ projection shows glucose as a linear molecule; however, in reality glucose exists in the cell is a dynamic equilibrium between linear and a ring form, which is more predominate since it is the more energetically stable structure
Fischer
The Formation of the ring structure results in two alternative forms of glucose, depending on the spatial orientation of the hydroxyl group on carbon #1
alpha-D-glucose has the hydroxyl group at C1 pointing down
while B-D-glucose has it pointing up in the Haworth projection
_________ and _________ are polymers composed of alpha-D-glucose and cellulose is a polymer of beta-D-glucose
Starch and Glycogen
Two monosaccharide units linked covalently through glycosidic bond
Disaccharides
The characteristic bond linking two sugars
Glycosic Bond
________ bond: the hydroxyl group on the carbon atom 1 of glucose is in the alpha configuration
alpha glycosidic
_________ bond: the hydroxyl group on carbon atom 1 of glucose is in the beta configuration
beta glycosidic
List 3 common disaccharides
Maltose
Lactose
Sucrose
Each of those 3 disaccharides are formed by a ____________
condensation reaction
Glycosidic bond type (a or B) determines the properties of __________
polysaccharides
Starch in plant cells and glycogen in animal and bacterial cells are both what?
Storage Polysaccharides
These polysaccharides may also contain alpha C__ to C__ linkages along the backbone, giving rise to branched side chains
1 : 6
Glycogen is highly __________, with alpha C1 to C6 linkages occurring once every 8 to 10 glucose units
branched
Glycogen is stored in the ________ as a source of glucose to maintain normal blood sugar levels; whereas, in _______ it serves as fuel source to generate ATP for muscle contracion
Liver : Muscle
Starch occurs both as unbranched _________ and as branched _________
amylose : amylopectin
Starch also has C__ to C__ linkages, but less frequent, once every 12 to 25 glucose units
1 : 6
Starch deposits in plants are usually about _____% amylose and _____% amylopectin
10-30 : 70-90
Cellulose is __________ 1/4 bond
Starch is __________ 1/4 bond
Beta-glycogen
alpha-glycogen
_______ makes up more than half of the carbon in many plants

Polymer of glucose, but the repeating monomer is B-D-glucose and the linkage is therefore:

Mammals do not have an enzyme that hydrolyzes a B C1 to C4 linkage; therefore, we cannot utilize cellulose as a ___________
Cellulose


B C1 to C4

Food Source
The cell wall of many bacteria contains two kinds of sugars, which are?
N-acetlyglucosamine (GlcNAc)
N-acetyluramic acid (MurNAc)
Repeating units in bacteria cell walls are linked to a ____________ bond for the polysaccharide
beta C1 to C4
Polysaccharide structure depends on ________
glycosic bonds
a bonds: starch and glycogen: 1.) a (1-4): unbranched; 2) a (1-6): branched
B bonds: cellulose
Because the linkage difference the two classes of polysaccharides have different secondary structures:
Both glycogen and starch (alpha linkages) spontaneously coil into loose helices
Cellulose (beta linkage) forms rigid, linear rods
Lipids are ________
Macromolecules
________ are a heterogenous (chemically and functionally) group of cellular components that resemble each other more in terms of solubility than in chemical structure
Lipids
The distinguishing feature of lipids is their __________ nature
hyrdrophobic
Some lipids are __________; having both a polar and a non-polar region
amphipathic
Lipids play what three main rolls in cells?
1. energy storage
2. Membrane structure
3. biological functions such as signal transduction
What are the six main classes of lipids?
1. Fatty acids
2. Triacylglycerols
3. Phospholipids
4. Glycolipids
5. Steroids
6. Terpenes
____________:Long, unbranched hydrocarbon chain with a carboxyl group at one end
Fatty acids
Fatty acids can be either ________ or ________
saturated or unsaturated
_________: form straight chains that pack tightly with no double bonds
Saturated fatty acids
_________: bend or kink and are unable to pack tightly, and they contain one or more double bonds
Unsaturated fatty acids
Fatty acid molecules are _________
amphipathic
Fatty acids usually contain ____ to ____ carbons per chain, with ____ and ____ most common
12 to 24 : C16, C18
Because fatty acids are highly reduced, they yield a great deal of _______ when oxidized and thus an efficient form for energy storage
energy
Fatty acids are the building blocks for several classes of ________
lipids
_____________: consist of a glycerol molecule with three fatty acids linked to it
Triacylglycerols (also called triglycerides)
Triacylglyrcerols are synthesized in a stepwise manner
Monoacylglycerols contain ________
Diacylglycerols contain _________
Triacylglycerols contain _________
1. one esterified fatty acid
2. two esterified fatty acids
3. three esterified fatty acids
The three fatty acids need not be ________

The ________ of the fatty acid chain can vary as well as the saturation state
identical

length
The main function of triaglycerols is to _________
store energy
In animal, triacylglycerols containing mainly saturated fatty acids are usually ____________ at room temperature and are called ________

In plants, the triacylglycerols are unsaturated (making their packing less compact), and are ________ at room temperature (vegetable oil)
solids : fats

Liquids
___________ are structurally similar to triacylglycerols in some chemical details, but differ strikingly in their properties and role in the cell
Phospholipids
Phospholipids can be classified into which 2 groups
Phosphoglycerides
Sphingolipids
Phospholipids are _________
amphipathic
Phospholipids are crucial for _________ structure in all membranes
lipid bilayer
A _______________ consists of a molecule of phosphatidic acid (a glycerol esterified to two fatty acids and a phosphate group) with a small polar alcohol
Phosphoglyceride
_______________ are the predominant phospholipids present in most membranes
Phosphoglycerides
The combination of a highly polar head and two long nonpolar chains gives the phosphoglycerides their amphipathic nature critical for membrane ______________
bilayer formation
The length and degree of unsaturation of fatty acid chains in membrane phospholipids profoundly affect membrane
Fluidity
____________ are based not on glycerol, but on the amine alcohol sphingosine, which contains a long hydrocarbon chain with a single site unsaturation near the polar end
Sphingolipids
____________ forms an amide bond to a long-chain fatty acid through its amino group
Sphingosine
The properties of of sphingolipids are determined by the __________
R-groups
_________ are derivatives of a four-membered ring structure called phenathrene, which makes them distinct from other lipids
Steroids
Steroids are only found in ________ cells
eukaryotic
Most common steroids in animal cells is ________: amphipathic molecule with polar head and a nonpolar hydrocarbon body and tail (4-membered ring and hydrocarbon side chain)
Cholesterol
Cholesterol is found primarily in
membranes
Steroids are __________ with a variety of functions
lipids
Cholesterol is the starting point for the synthesis of all __________ hormones
steroid: have roles in development behavior