Chapter 2: Nucleic acids Flashcards
What does RNA stand for?
Ribonucleic acid
What does DNA stand for?
Deoxyribonucleic acid
What does DNA do?
it carries genetic information
What monomers are DNA and RNA made of?
Nucleotides
What are the three components that make up nucleotides?
a pentose sugar, a phosphate group and a nitrogen-containing organic base
What are the five types of organic base?
Cytosine, Adenine, Guanine, Thymine, Uracil
How can two nucleotides be joined together?
by a condensation reaction, that forms a phosphodiester bond between the pentose sugar and phosphate molecule
What is RNA?
a singe stranded polynucleotide, where the pentose sugar is ribose
What are the organic bases of RNA?
Adenine, Guanine, Cytosine and Uracil
What is the function of RNA?
Transferring genetic information from DNA to ribosomes
Who discovered the structure of DNA?
James Watson and Francis Crick, in 1953
What are the bonds between the organic bases of two DNA strands?
hydrogen bonds
What base always joins to Adenine on DNA?
Thymine
What base always joins to Guanine?
Cytosine
What are DNA bases said to be, because of their pairings?
Complementary
What are the phosphate and deoxyribose often called in the DNA structure?
The structural backbone of the DNA molecule
What is the structure the DNA strand form when bonded to each other?
a double helix structure
How does the phosphodiester backbone make DNA stable?
It protects the more chemically reactive organic bases inside the double helix.
How do the hydrogen bases between base pairs make DNA stable?
they form bridges between the phosphodiester backbones.
How many hydrogen bonds are between Guanine and Cytosine bases?
Three hydrogen bonds
How many hydrogen bonds are between Thymine and Adenine bases?
Two hydrogen bonds
Why is DNA more stable the more G-C bonds there are?
G-C have three hydrogen bonds, thus more strength
Why is DNA’s stable structure an adaptation for DNA’s function?
It allow DNA to be passed on generation without significant change by mutations. (unrepaired mutations are rare)
The phosphodiester backbone protects the bases from outside chemicals and forces
What is the benefit of the hydrogen bonds in the DNA’s function?
They can easily broken for DNA replication.
How does DNA’s large structure benefit its function?
So it can carry a large amount of genetic information.
What is the benefit of base pairing to DNA replication?
It allows information to be transferred to mRNA.
What are the two main stages of Cell division?
Nuclear division and cytokinesis
What is Nuclear Division?
The process by which the nucleus divides, there are two types mitosis and meiosis.
What is Cytokinesis?
It follows nuclear division and is the process by which the whole cell divides.
How are Zygotes formed?
by cellular fusion
What is the universally accepted model for DNA replication?
Semi-conservative replication
What are the four requirements for semi-conservative replication
Free floating DNA of all bases; both strands of DNA molecule ; DNA polymerase; a source of energy.
Whats the function of DNA helicase in semi-conservative replication?
to separate the two strands by breaking hydrogen bonds between complementary bases
What happens after the DNA strands have been split (by DNA helicase) in semi- conservative replication?
free nucleotides bind to their complementary bases
What is the function of DNA polymerase in semi-conservative replication?
to form the phosphodiester bonds between the nucleotides that have been paired with their complementary bases.
What is the result of semi-conservative replication?
Two identical strands of DNA half of each retaining the original DNA material
What does ATP stand for and what is its purpose?
Adenosine triphosphate is used as the main source of energy to carry out processes within cells.
What are the three parts of ATP?
- Adenine- an organic base
- ribose- a pentose sugar
- phosphates- a chain of three phosphate groups
What does ATP store energy?
the bonds between the three phosphate groups are weak, so have low activation energy. when broken they release a considerable amount of energy.
What is the word equation for the production of ATP?
ATP + (H2O) → ADP+ Pi + (energy)
What is the reaction that breaks down ATP?
hydrolysis
What enzyme catalyses the break down of ATP?
ATP hydrolase
What reaction uses ADP and Pi to form ATP?
a condensation reaction
What enzyme catalyses the formation of ATP from ADP and Pi?
ATP synthase
What three ways can ATP be synthesised?
in photosynthesis (photophosphorylation); during respiration (oxidative phosphorylation);
the transfer of phosphate groups from donor molecules to ADP (substrate- level phosphorylation)
Why is ATP a good energy donor over Glucose?
it provides immediate energy, when glucose is slower to break down.
Why is ATP a better immediate energy?
it releases less energy than glucose so is more manageable quantities; the hydrolysis is a single reaction that releases immediate energy.
Why is ATP needed in metabolic processes?
ATP provides energy to build macromolecules.
Why is ATP needed for movement?
it provides the energy for muscle contraction.
Why is ATP needed for active transport?
it provides the energy to change the shape of carrier protiens
Why is ATP needed for secretion?
Its used to form lysosomes for cell secreation
Why is ATP needed for activation of molecules?
the Pi released during the hydrolysis of ATP can be used to phosphorylate other compounds, lowering their activation energy.
What is a dipolar molecule?
When a molecule had both negative and positive poles.
What affect does the hydrogen bonds between water molecules have?
It causes them to stick together.
Why does water have a large specific water capacity?
It takes more energy to break the bonds between each water molecule, so it takes more energy to heat a given mass of water.
What is the advantages of waters large specific water capacity for organisms?
It acts as a buffer to sudden temperature variations.
What is the benefit of waters latent heat of vaporisation to organisms?
Evaporation causes cooling, because the bodies heat is used to evaporate the water.
What is cohesion?
the tendency of molecules to stick together eg. Water
What is the benefit of the water’s large cohesive forces?
the hydrogen bonds cause the strong cohesive forces that allows the water to be pulled through the xylem vessel
What is the force of cohesive forces at water’s surface called?
surface tension
Why is water important in the metabolism?
it can be used in hydrolysis to break down molecules; chemical reactions can take place in an aqueous medium; water is a raw material in photosynthesis.
Why is water an important solvent?
it readily dissolves other substances.
Why is evaporation of water beneficial to organisms?
it cools organisms, so they can control their temperature
What is the benefit of water being transparent?
It allows light to pass through, so aquatic plants can photosynthesise; the light rays can penetrate the fluid that fills the eye.
Where are inorganic compounds most commonly found?
in a solution in the cytoplasm of cells and in body fluids.
