2.8 Nucleic Acids Flashcards
What are the 2 types of nucleic acids?
- DNA (deoxyribonucleic acid)
- RNA (ribonucleic acid)
What does DNA do?
stores genetic information in the cell and in the organism
What does a cell do with the information stored in it by DNA?
the cell replicates and transmits this information when the cell copies itself as well as when the organism reproduces
What is a nucleotide?
a molecular complex of 3 subunits
- phosphate (phosphoric acid)
- pentose sugar
- nitrogen-containing base
What do nucleotides in DNA contain?
the sugar deoxyriose
What do nucleotides in RNA contain?
the sugar ribose
What are the 4 different types of bases in DNA?
adenine
thymine
guanine
cytosine
Which how many rings can a base in DNA have?
adenine and guanine: 2
thymine and cytosine: 1
What are the 4 different types of bases in RNA?
adenine
uracil
guanine
cytosine
Why are they called bases?
their presence raises the pH of a solution
How is the sequence of DNA most often referred?
in terms of the bases present
What is a strand?
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
What is the sequence of the bases in human DNA called?
the human genome
What is the human genome expected improve?
- genetic counselling
- gene therapy
- medicines to treat the causes of many human illnesses
What is a double helix?
the structure of DNA resulting from 2 strands twisting about each other
In DNA, how are the 2 strands held together?
by hydrogen bonds between the bases
What are the upright (sides) of the ladder of DNA made of?
alternating phosphate and sugar molecules
What are the rungs of the ladder of DNA made of?
complementary paired bases
What are always the complementary base pairings?
adenine and thymine
guanine and cytosine
*complementary bases have shapes that fit together
What do complementary base pairings allow DNA to do?
replicate in a way that ensures the sequence of bases will remain the same
What do the base sequences of specific sections of DNA contain?
a code that specifies the sequence of amino acids in the proteins of the cell
How many strands does RNA have and how is it formed?
single -stranded
formed by complementary base pairing with one DNA strand
What is mRNA?
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
What is the heredity information stored by the DNA?
the sequence of its bases, which determines the primary structure of the cell’s proteins
What is ATP?
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
Why is ATP a high-energy molecule?
because of the energy stored in the chemical bonds of the phosphates
the last two phosphate bonds are unstable and easily broken
What is the chemical work of ATP?
supplies energy needed to synthesize macromolecules (anabolism) that make up the cell and therefore, the organism
What is the transport work of ATP?
supplies energy needed to pump substances across the plasma membrane
What is the mechanical work of ATP?
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
In cells, what usually happens to the terminal phosphate bond?
it is hydrolyzed, leaving the molecule ADP and a molecule of inorganic phosphate P
What happens when ATP is converted to ADP + P?
the amount of energy released (about 7.3 kcal per mole) is sufficient for a particular biological function and little energy is wasted
What do cells use the energy released by ATP breakdown for?
to synthesize macromolecules such as carbohydrates and proteins
What do muscle cells use the energy released by ATP breakdown for?
muscle contraction
What do nervous cells use the energy released by ATP breakdown for?
the conduction of nerve impulses
What happens after ATP breaks down?
it is rebuilt by the addition of P to ADP with an input of energy
Why is glucose broken down in a step-wise fashion during cellular respiration?
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
What do ATP molecules serve as?
small “energy packets” suitable for supplying energy to a wide variety of a cell’s chemical reactions
What happens when cells require energy?
- they ‘spend’ ATP
- reactions in the cell that need energy require ATP
- the more active the organism, the greater the demand for ATP
What is an endergonic reaction? Give an example.
creation of ATP from ADP and P requires input of energy from other sources
ie. cellular respiration
What is an exergonic reaction? Give an example.
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
In cells, how does ATP carry energy?
between exergonic and endergonic reactions
*when a phosphate group is removed by hydrolysis, ATP releases the appropriate amount of energy for most metabolic reactions
