1-Uworld Carbs, Nucleotides, and Lipids

what are triglycerides?

triglycerides are energy-storage lipids that are comprised of a glycerol backbone that is joined to three fatty acids by ester linkages

what happens when energy is needed?

when energy is needed, the ester linkages are hydrolyzed, releasing free fatty acids and free glycerol

the free fatty acids are transported where?

the free fatty acids are transported to the mitochondria and eventually oxidized by Beta-oxidation

what happens to the free glycerol?

the free glycerol is metabolized into dihydroxyacetone phosphate to enter glycolysis or gluconeogenesis

what do ester hydrolysis reactions produce?

ester hydrolysis reactions produce 3 fatty acids and 1 glycerol

what factor decreases the stability of the DNA double helix during denaturation?

hydrogen bonds are disrupted

How is the DNA double helix arranged?

the sugar-phosphate backbone (linked by phosphodiester bonds) lies on the outside and the nitrogenous bases (paired by the hydrogen bonds) lie on the inside

during double helix formation what takes place?

complementary strands of DNA anneal through the creation of hydrogen bonds between nitrogenous bases

once the double helix is formed, what is required to denature the duplex?

energy is required to denature the duplex into 2 separate strands

what charge does the sugar-phosphate backbone have?

the sugar-phosphate backbone is negatively charged

what does additional heat do to the helix?

additional heat separates the helix completely

what does increasing the temperature during the melting step do?

Increasing the temperature during the melting step provides the heat energy necessary to break the hydrogen bonds between bases and separate the double helix

How are base pairs arranged in the double helix?

The base pairs in the double helix are “stacked” almost on top of each other

what happens when the DNA helix denatures during melting?

base stacking is interrupted, not enhanced, when the DNA helix denatures during melting

what is primarily responsible for the stability of the double helix structure?

stacking interactions, which are due to hydrophobic effects and nonpolar van der Waals forces between the bases

why do hydrophobic effects decrease during the melting step?

because hydrophobic bases are exposed to water

In aqueous solution, hydrophobic effects do what?

Hydrophobic effects force hydrophobic bases toward the double helix interior and away from the polar solvent (water)

in contrast, the hydrophilic negatively charged phosphates do what?

the hydrophilic, negatively charged phosphates in the backbone can hydrogen bond with water molecules

what do covalent phosphodiester bond do

covalent phosphodiester bonds of the sugar-phosphate backbone maintain the structure of the single-stranded DNA

are phosphodiester bonds affected when double helix separated during denaturation?

no

what do hydrogen bonds do during the formation of DNA double helix?

hydrogen bonds form between bases and release energy

how is heat energy used in a DNA melting reaction?

Heat energy provided in a DNA melting reaction is used to disrupt interactions that contribute to DNA double helix structure: hydrogen bonding, base stacking, and hydrophobic effects

what do carbohydrates on the outer surface of the cell do?

carbohydrates on the outer surface of the cell can act as markers for cell recognition and signaling