3.1.2 Nucleic Acids Flashcards
Name the 4 bases found in DNA, name the bonds that form between them
Adenine , Thymine, Guanine ,Cytosine. Hydrogen bonds
which bases are purines
Adenine and Guanine (think of PURE SILVER Ag)
which bases are pyrimidines
Cytosise, Thymine and Uracil
Describe the complementary base pairing rule found in DNA
Adenine to Thymine (2 H bonds) Cytosine to Guanine (3 H bonds). Adenine also can bind to Uracil (2 h bonds)
Why does a purine always pair with a pyrimidine in the DNA molecule?
Purines are double ring structures and pyrimidines are single ring structures. The purine-pyrimidine pair ensures that the “rungs” of the DNA ladder are always the same length
Which molecules make up the ‘backbone’ of a polynucleotide?
Phosphates and pentose sugars
Which enzyme separates the strands in DNA replication
DNA Helicase
State the role of DNA polymerase
Joins nucleotides together by condensation reactions that form phosphodiester bonds
Why is DNA replication known as ‘semi conservative’?
Because the orginal DNA molecule is split in two and half of each new molecule comes from the original. Each new DNA molecule has consists of 1 “parent” and 1 “new” strand
State 3 differences between RNA and DNA
RNA is single-stranded, has U instead of T as a base, has ribose as a sugar (not deoxyribose) and is smaller
Describe the structure and function of tRNA
tRNA is a single stranded polynucleotide that coils and binds to itself to form a clover-leaf structure. It has a sequencd of 3 exposed bases called the anticodon that will bind to the mRNA codon and also contains a site for the attachment of a specific amino acid. Its function is to bring a specific amino acid to the ribosome during protein synthesis
Describe DNA replication
uDNA helicase breaks the hydrogen bonds, unzipping the DNA, then free nucleotides bind to the exposed bases via complementary base pairing. Then DNA polymerase makes phosphodiester bonds to join the backbone of the new strand. In reality one strand is synthesied continuously and one is synthesied in chucks called okazaki fragments that are then joined by DNA ligase.
What is ATP made of?
Adenine, ribose and three phosphates (adenione and ribose together = adenosine)
Explain how ATP is adapted for it’s role and state one disadvantage of ATP
energy is released in small, manageabe amounts (compared to e.g. glucose), energy is released immediately. BUT it cannot be stored so has to be continuously produced where it is needed
Name 5 processes that ATP is required for
metabolic processes (building molecules), movement, active transport, secretion of substances, activation of molecules
Water is dipolar. What do we mean by dipolar?
One end of the molecule has a slight positive charge, the other end is slightly negative
Why is water important for living things?
It is used in metabolism (condensation/ hydrolysis), it is a solvent for many substances, water potential has to be at the right level so cells don’t shrivel or burst due to osmosis
How does ATP release energy to a cell?
ATP undergoes hydrolysis to form ADP + Pi, releasing energy. Its important to note the overall reaction releases energy not just the breaking of the phospate to
What enzyme makes the majority of ATP in the cell. Briefly describe how it works
ATP synthase. This enzyme uses proton gradients across a membrane. Protons flow through the enzyme making it spin. The spinning releases ATP formed on the surface of th enzyme
What properties of water provide stable aquativ environments?
High specific heat capacity provides thermally stable environments. The fact that ice has a lower density than water means that freezing bodies of water are insulated by a layer of ice forming on top (like a pond in winter)
What properties of water are crucial for transpiration. Explain
cohesion - water molecules stick together. Adhesion - water molecules stick to the walls of the xylem. The cohesion tension theory explains that as water molecules evaporate from the leaves of plants the cohesion-tension created pulls on the column of water molecules below in the xylem causing transpiration.
what famous DNA experiment does this picture show
the meselson stahl experiment
Briefly describe the meselson-stahl experiment
Bacteria grown on heavy N-15 so all the DNA was “heavy”. Bacteria transferred to N-14 medium and divided every 20 minutes. After 1 division all the DNA was “intermediate” and after 2 divisions 50% of the DNA was “light” and 50% “intermediate”.
Draw a few molecules of water showing the bonding between them
