2.8 Nucleic Acids

Question 1

What are the 2 types of nucleic acids?

Answer 1

• DNA (deoxyribonucleic acid)

- RNA (ribonucleic acid)

Question 2

What does DNA do?

Answer 2

stores genetic information in the cell and in the organism

Question 3

What does a cell do with the information stored in it by DNA?

Answer 3

the cell replicates and transmits this information when the cell copies itself as well as when the organism reproduces

Question 4

What is a nucleotide?

Answer 4

a molecular complex of 3 subunits

• phosphate (phosphoric acid)
• pentose sugar
• nitrogen-containing base

Question 5

What do nucleotides in DNA contain?

Answer 5

the sugar deoxyriose

Question 6

What do nucleotides in RNA contain?

Answer 6

the sugar ribose

Question 7

What are the 4 different types of bases in DNA?

Answer 7

adenine
thymine
guanine
cytosine

Question 8

Which how many rings can a base in DNA have?

Answer 8

adenine and guanine: 2

thymine and cytosine: 1

Question 9

What are the 4 different types of bases in RNA?

Answer 9

adenine
uracil
guanine
cytosine

Question 10

Why are they called bases?

Answer 10

their presence raises the pH of a solution

Question 11

How is the sequence of DNA most often referred?

Answer 11

in terms of the bases present

Question 12

What is a strand?

Answer 12

a linear molecule formed by nucleotides that have a backbone made up of alternating phosphates and sugars with the bases projecting to one side of the backbone

Question 13

What is the sequence of the bases in human DNA called?

Answer 13

the human genome

Question 14

What is the human genome expected improve?

Answer 14

• genetic counselling
• gene therapy
• medicines to treat the causes of many human illnesses

Question 15

What is a double helix?

Answer 15

the structure of DNA resulting from 2 strands twisting about each other

Question 16

In DNA, how are the 2 strands held together?

Answer 16

by hydrogen bonds between the bases

Question 17

What are the upright (sides) of the ladder of DNA made of?

Answer 17

alternating phosphate and sugar molecules

Question 18

What are the rungs of the ladder of DNA made of?

Answer 18

complementary paired bases

Question 19

What are always the complementary base pairings?

Answer 19

adenine and thymine
guanine and cytosine

*complementary bases have shapes that fit together

Question 20

What do complementary base pairings allow DNA to do?

Answer 20

replicate in a way that ensures the sequence of bases will remain the same

Question 21

What do the base sequences of specific sections of DNA contain?

Answer 21

a code that specifies the sequence of amino acids in the proteins of the cell

Question 22

How many strands does RNA have and how is it formed?

Answer 22

single -stranded

formed by complementary base pairing with one DNA strand

Question 23

What is mRNA?

Answer 23

messenger RNA

carries the information from the DNA strand to the ribosome where it is translated into the sequence of amino acids specified by the DNA

Question 24

What is the heredity information stored by the DNA?

Answer 24

the sequence of its bases, which determines the primary structure of the cell’s proteins

Question 25

What is ATP?

Answer 25

adenosine triphosphate a nucelotide composed of the nitrogen-containing base adenine and the 5-carbon sugar ribose (together called ribose) and 3 phosphate groups *a common and universal energy "currency" of the cells in living systems

Question 26

Why is ATP a high-energy molecule?

Answer 26

because of the energy stored in the chemical bonds of the phosphates the last two phosphate bonds are unstable and easily broken

Question 27

What is the chemical work of ATP?

Answer 27

supplies energy needed to synthesize macromolecules (anabolism) that make up the cell and therefore, the organism

Question 28

What is the transport work of ATP?

Answer 28

supplies energy needed to pump substances across the plasma membrane

Question 29

What is the mechanical work of ATP?

Answer 29

supplies energy needed to permit muscles to contract, cilia and flagella to beat, chromosomes to move *in most cases, ATP is the immediate source of energy for these processes

Question 30

In cells, what usually happens to the terminal phosphate bond?

Answer 30

it is hydrolyzed, leaving the molecule ADP and a molecule of inorganic phosphate P

Question 31

What happens when ATP is converted to ADP + P?

Answer 31

the amount of energy released (about 7.3 kcal per mole) is sufficient for a particular biological function and little energy is wasted

Question 32

What do cells use the energy released by ATP breakdown for?

Answer 32

to synthesize macromolecules such as carbohydrates and proteins

Question 33

What do muscle cells use the energy released by ATP breakdown for?

Answer 33

muscle contraction

Question 34

What do nervous cells use the energy released by ATP breakdown for?

Answer 34

the conduction of nerve impulses

Question 35

What happens after ATP breaks down?

Answer 35

it is rebuilt by the addition of P to ADP with an input of energy

Question 36

Why is glucose broken down in a step-wise fashion during cellular respiration?

Answer 36

so that the energy of glucose is converted ti that of ATP molecules in mitochondria *only 39% of the free energy of glucose is transformed to ATP, the rest is lost as heat

Question 37

What do ATP molecules serve as?

Answer 37

small "energy packets" suitable for supplying energy to a wide variety of a cell's chemical reactions

Question 38

What happens when cells require energy?

Answer 38

- they 'spend' ATP - reactions in the cell that need energy require ATP - the more active the organism, the greater the demand for ATP

Question 39

What is an endergonic reaction? Give an example.

Answer 39

creation of ATP from ADP and P requires input of energy from other sources ie. cellular respiration

Question 40

What is an exergonic reaction? Give an example.

Answer 40

hydrolysis of ATP releases previously stored energy, allowing the change in free energy to do work and drive other processes ie. protein synthesis, nerve conduction, muscle contraction

Question 41

In cells, how does ATP carry energy?

Answer 41

between exergonic and endergonic reactions *when a phosphate group is removed by hydrolysis, ATP releases the appropriate amount of energy for most metabolic reactions