Nucleotides

Question 1

What are the functions on nucleotides in biological systems?

Answer 1

energy metabolism (ATP)
enzyme cofactors (NAD+)
etc…

Question 2

What components nucleotides are made of?

Answer 2

Nitrogenous base , Five-carbon sugar , Phosphate group

Question 3

nucleoside and nucleobase.

Answer 3

side - Pyrimidines (C,U,T) , purines (A,G) , pentose sugar - ribose deoxyribose

base - pyrimidines , purines

Question 4

Two main types of nucleobases: purines and pyrimidines. What are the most common nucleobases
from each class?

Answer 4

pyr - Cytosine (DNA and RNA) , Thymine (DNA) , Uracil (RNA)

purine - Adenine and guanine in RNA and DNA

Question 5

Nomenclature of nucleotides and nucleosides, one-letter and three-letter codes for ribo- and
deoxyribo-nucleotides.

Answer 5

Ribo-nucleotides:

Adenosine monophosphate (AMP): A, AdoMP
Guanosine monophosphate (GMP): G, GuaMP
Cytidine monophosphate (CMP): C, CytMP
Uridine monophosphate (UMP): U, UMP
Deoxyribo-nucleotides:

Deoxyadenosine monophosphate (dAMP): dA, dAMP
Deoxyguanosine monophosphate (dGMP): dG, dGMP
Deoxycytidine monophosphate (dCMP): dC, dCMP
Deoxythymidine monophosphate (dTMP): dT, dTMP

Question 6

What are phosphodiester bonds?

Answer 6

bonds that link successive nucleotides in linear polymers

Question 7

What is backbone of nucleic acid? What nucleotide components it is made of?

Answer 7

In DNA and RNA, the backbone is composed of alternating sugar and phosphate groups that are linked together by phosphodiester bonds.

Question 8

Directionality of DNA/RNA backbone.

Answer 8

meaning that it has a 5’ end and a 3’ end. The 5’ end of the backbone refers to the carbon atom of the sugar molecule that is attached to the phosphate group at the fifth position, while the 3’ end refers to the carbon atom of the sugar molecule that is attached to the phosphate group at the third position.

Question 9

What makes DNA more stable under physiological conditions compared to RNA?

Answer 9

w/ hydrolysis of RNA: RNA is unstable under alkaline conditions (pH > 7)

Question 10

How many strands are usually in DNA? In RNA?

Answer 10

double stranded / single stranded

Question 11

What are Watson-Crick base pairs?

Answer 11

Watson-Crick base pairs refer to the specific pairing of nitrogenous bases that forms the rungs of the DNA double helix. The nitrogenous bases that make up the rungs of the DNA ladder are adenine (A), thymine (T), cytosine (C), and guanine (G).

Question 12

How many H-bonds are there between A and T? G and C?

Answer 12

A pairs with T/U (2H)

G pairs with C (3H)

Question 13

What is Chargaff’s rule?

Answer 13

the amount of adenine (A) in DNA is equal to the amount of thymine (T), and the amount of cytosine (C) is equal to the amount of guanine (G).

Question 14

What is in common and what is different between DNA and RNA?

Answer 14

common: Both are composed of nucleotides, which consist of a sugar molecule, a phosphate group, and a nitrogenous base.

diff: The sugar molecule in DNA is deoxyribose, while the sugar molecule in RNA is ribose.

Question 15

What is denaturation of DNA? What is the reverse process?

Answer 15

hyperchromic effect - base composition / length of DNA / pH

• not uniform

must fix these conditions to reverse this process

Question 16

Biological roles and composition.

Answer 16

membrane structure and integrity
storage of energy
insulation
etc…

Question 17

What are fatty acids? What are the two main types of fatty acids that are present in living organisms
(saturated vs. unsaturated)? What type are the double bonds in the unsaturated fatty acids.

Answer 17

Saturated fatty acids: These fatty acids have no double bonds between the carbon atoms in the chain.

Unsaturated fatty acids: These fatty acids have one or more double bonds in the carbon chain

Question 18

Standard nomenclature of fatty acids? What does 18:1(delta9) mean? You are expected to be able to
draw the formula of fatty acid if you are given its standard name, like 18:1(delta9), and opposite

Answer 18

In the nomenclature 18:1(delta9), “18” refers to the total number of carbon atoms in the chain, and “1” refers to the number of double bonds. The “delta9” notation indicates that the first double bond is located between the ninth and tenth carbon atoms, counting from the carboxyl group end of the chain.

Question 19

What happens with the melting points of fatty acids as the number of double bonds in them increases
(assumin that the number of carbons is the same)?

Answer 19

As the number of double bonds in fatty acids increases (assuming that the number of carbons in the chain is the same), the melting point of the fatty acid decreases

Question 20

What causes kinked conformation in
the fatty acid?

Answer 20

presence of one or more double bonds in the carbon chain.

Question 21

Which tryacylglycerols are called oils and
which ones are called fats?

Answer 21

solid triacylglyarols are fats

liquid “ are oils

Question 22

structural lipids

Answer 22

polar
double layer of lipids
ampipathic : nonpolar tails and polar heads
variability

Question 23

glycerophopholipids?

Answer 23

primary consituents of cell membranes

L-glycerol - 3 - phosphate

• 2 fatty acids attached
• unsaturayed FA connected to C2

Question 24

What is the backbone of sphingolipids?

Answer 24

NOTTTT GYCEROLLL

it is sphingosine

FA is joined to shingosine via amide linkage

Question 25

What is cholesterol and what are the biological functions of cholesterol? Which organisms can
synthesize it and which cannot?

Answer 25

transported via blood vessels

deposits and clogs artieries

is a sterol

Question 26

What are steroid hormones? What are they synthesized from?

Answer 26

oxidized derivatives of sterols

more polar than cholesterol