1.2 (2) - Nucleic Acids Flashcards
Structure of RNA and DNA DNA replication ENergy and ATP Water and its functions
What is a nucleic acid?
A complex organic substance present in living cells whose molecule consists of many nucleotides.
What are the 3 components of a DNA nucleotide?
- Phosphate group
- Pentose sugar
- Organic nitrogenous base (adenine, thymine, guanine, cytosine)
What are the 3 components of a RNA nucleotide?
- Phosphate group
- Pentose sugar
- Organic nitrogenous base (adenine, uracil, guanine, cytosine)
What bond joins nucleotides together?
Phosphodiester bond
Through what reaction are the bonds between the nucleotide’s components formed?
Condensation reaction
Describe RNA
- Single-stranded polynucleotide chain
- Pentose sugar is always a ribose sugar
- Uses A, G, C and U nitrogenous bases
- Takes 3 forms:
- Transfer (tRNA)
- Messenger (mRNA)
- Ribosomal (rRNA)
Describe DNA
- Forms a double-stranded pair of extremely long polynucleotide chains
- Pentose sugar is always a deoxyribose sugar
- Uses A, G, C and T nitrogenous bases
- Stable molecule that is better suited to long-term storage of DNA because:
- 2 strands of RNA are bonded together by hydrogen
bonds between complementary base pairs - Phospholipid backbone is relatively unreactive and
protects the more reactive bases
- 2 strands of RNA are bonded together by hydrogen
What are some functional adaptations of DNA?
- Hereditary molecule
- Highly stable molecule
- Very large molecule
What is the method of DNA replication called?
Semi-conservative replication
What does ‘semi-conservative replication’ imply?
Every time DNA is copied, half is kept and half is made new
Explain the stages of semi-conservative replication
1) DNA helicase breaks H bonds between polynucleotides
2) DNA unwinds into 2 strands
3) Each exposed strand acts as a template so that free, complementary nucleotides can bind to specific bases
4) The free nucleotides join via a condensation reaction - DNA polymerase joins the new nucleotides together
5) The template strand and the new strand of DNA rejoin via hydrogen bonds and re-coil
6) Each new DNA molecule contains one of the original DNA strands (half the original DNA)
What is ATP?
An immediate source of energy used to power cellular processes
What kind of molecule is ATP?
Phosphorylated molecule (phosphates are added)
What does ATP stand for?
Adenosine triphosphate
What are the 3 components of an ATP molecule?
- Adenine base
- Ribose sugar
- 3 phosphate groups (joined together by 2 phosphoanhydride bonds)
What happens when ATP is hydrolysed?
It can turn into ADP with 1 Pi group
What enzyme catalyses the hydrolysis reaction that causes ATP to turn into ADP?
ATP hydrolase
What can happen to the Pi released during the hydrolysis of ATP?
It can phosphorylate other compounds, which can make them more reactive
By what reaction does the resynthesis of ADP and Pi undergo?
Condensation
What enzyme catalyses the condensation reaction between ADP and Pi, to make ATP?
ATP synthase
What are some of the uses of ATP?
It’s used in:
- Metabolic processes - Muscle movement - Active transport - Secretion of lysosomes - Activation of molecules (phosphorylating them makes them more reactive)
What are 5 useful properties of water?
- Dipolar molecule
- Water and hydrogen bonding
- High specific heat capacity
- High latent heat of vaporisation
- Cohesion and surface tension
What do we mean when we say that water is ‘dipolar’?
Even though the molecule has an overall negative charge, the Hs have a slight +ve charge and the O has a slight -ve charge, meaning it’s got +ve and -ve poles
What is the significance of water and hydrogen bonding?
Hydrogen bonds form important forces that cause water molecules to stick together, giving it its unusual properties
What is the significance of water having a high specific heat capacity?
Because water molecules stick together it takes more energy to separate them, so water has a high boiling point
What is the significance of water having a high latent heat of vaporisation?
The H bonds between water molecules means that lots of energy is needed to evaporate 1g of water
What is the significance of water molecules being cohesive/having surface tension?
Water molecules stick together (cohesion) - because of its H bonds, water has large cohesive forces that allow it to be pulled through tubes (eg. xylem)
When water meets the air, it tends to be pulled back to the water rather than escaping from it (the force is called surface tension). This ST means that water is strong enough to support small insects because it acts like a skin
Why is water important in organisms?
- Used in metabolism - used and produced in hydrolysis and condensation reactions
- It’s a solvent - can dissolve:
- gases
- waste products (eg. urea)
- inorganic ions
- enzymes
Where do you find organic ions?
In solution in the cytoplasm and body fluids (some at high concs and other at low concs)
What is the role of inorganic ions?
Each type of ion has a specific role, depending on its properties
