Nucleic Acids Flashcards
(27 cards)
Structure of a nucleotide
Organic base , pentose sugar , phosphate
How do nucleotides join together?
Condensation reaction between the phosphate group of 1 nucleotide and the pentose sugar of the adjacent nucleotide
Linked by phosphodiester bonds
Structure of DNA
Double stranded: 2 anti parallel polynucleotide strands
The 2 stands twist to form a double helix
Strands are joined together by hydrogen bonds
Deoxyribose sugar , base , phosphate
Why is DNA a stable molecule
Strong phosphodiester bonds in the sugar phosphate backbone
Many hydrogen bonds
How is the structure of DNA related to its function
Stable molecule so rarely mutates
2 polynucleotide strands are only joined with weak hydrogen bonds so they can separate during protein synthesis and DNA replication
2 polynucleotide strands so both can act as a template strand
Structure of RNA
Single, short chain
Pentose sugar = Ribose
Organic bases = A , G , C , U
Function of mRNA
Transfers genetic information from DNA to the ribosomes
Function of rRNA
Ribosomes are made up of protein and rRNA
Function of tRNA
Directly used in protein synthesis
Semi-conservative replication
DNA Helu case causes the 2 polynucleotide strands of DNA to separate by breaking the hydrogen bonds that join the complementary bases together
Free nucleotides bind specifically to their complementary bases
DNA polymerase joins the bases through phosphodiester bonds
Two identical molecules of DNA are formed - each molecule retains half of the original DNA material
High heat capacity of water
Definition
Importance in living organisms
Because water molecules stick together, it makes more energy to separate them than would be needed if they didn’t bond to one another
Water therefore acts as a buffer against sudden temperature variations, making aquatic environments temperature stable
High latent heat of vaporisation of water
Definition
Importance in living organisms
Hydrogen bonding between H2O molecules means that it requires a lot of energy to evaporate 1 gram of H2O
Evaporation of H2O such as sweat in the body of mammals is an effective way of cooking because body heat is used to evaporate the H2O
Water as a solvent
Definition
Importance in living organisms
Water readily dissolves other substances
Gases e.g. oxygen & carbon dioxide
Wastes e.g. ammonia & urea
Inorganic ions & small hydrophilic molecules e.g. amino acids, monosaccharides, ATP, enzymes
Water as a cohesive molecule
Definition
Importance in living organisms
The tendency of molecules sticking together
Xylem vessels in plants need this for the transpiration stream
Surface tension of water
Definition
Importance in living organisms
When water molecules meet air they tend to be pulled back into the body of water, rather than escaping from it
Can support small organisms e.g. pond skaters
Water as a metabolite
Definition
Importance in living organisms
Involved in chemical reactions
Used to break down molecules by hydrolysis, produced in condensation reactions
The 4 types of inorganic ions
Iron ions
Phosphate ions
Hydrogen ions
Sodium ions
Example of an iron ion and its use
Haemoglobin
Oxygen transport
Phosphate ions used for?
Structural role in DNA
Storing energy in ATP
Hydrogen ions used for?
Determining pH of solutions
-> functioning of enzymes
Sodium ions used for?
Transportation of glucose & amino acids across the cell membrane
( Co-transport ) (( Ileum ))
5 Roles of ATP
- Short term store of chemical potential energy that releases energy through a single reaction
- Breakdown of ATP releases a small, manageable amount of energy that is ideal for fuelling “energy requiring reactions”
- The breakdown of glucose would produce more energy than is usually required, less energy will be lost as heat
- Cannot be stored and so has to be continuously made within the mitochondria of cells that need it
- Cells e.g. muscle fibres, small intestine, which require more energy for movement & active transport possess many large mitochondria
ATP in metabolic processes
ATP provides the energy required to build up macromolecules from their basic units
e.g. starch from glucose
ATP in movement
ATP provides the energy required for muscle contraction
