Cell Biology Ch.3

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Cell Bio Test

The right-handed Watson-Crick helix is the _________, the main form of DNA in cells


There are two other biologically active double helical structures


_________ has a right handed helical configuration that is thicker and shorter than B-DNA


__________ is a left handed double helix that is a zigzag pattern that has a longer, thinner sugar-phosphate backbone


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


_________ are long-chain polymers of sugars and sugar derivatives


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 units that form polysaccharides are simple sugars called


What are the 2 categories of sugars

Aldosugars and Ketosugars

________ is a category of sugars with a terminal carbonyl group


_________ is a category of sugar with an internal carbonyl group


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)


Glucose has 16 possible stereoisomers, so it has how many assymetric carbons?


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


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


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


Each of those 3 disaccharides are formed by a ____________

condensation reaction

Glycosidic bond type (a or B) determines the properties of __________


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


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


_______ 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 ___________


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 ________


________ are a heterogenous (chemically and functionally) group of cellular components that resemble each other more in terms of solubility than in chemical structure


The distinguishing feature of lipids is their __________ nature


Some lipids are __________; having both a polar and a non-polar region


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 _________


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


Fatty acids are the building blocks for several classes of ________


_____________: 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



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


___________ are structurally similar to triacylglycerols in some chemical details, but differ strikingly in their properties and role in the cell


Phospholipids can be classified into which 2 groups


Phospholipids are _________


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


_______________ are the predominant phospholipids present in most membranes


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


____________ 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


____________ forms an amide bond to a long-chain fatty acid through its amino group


The properties of of sphingolipids are determined by the __________


_________ are derivatives of a four-membered ring structure called phenathrene, which makes them distinct from other lipids


Steroids are only found in ________ cells


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 is found primarily in


Steroids are __________ with a variety of functions


Cholesterol is the starting point for the synthesis of all __________ hormones

steroid: have roles in development behavior

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