Chapter 2: Nucleic Acids Flashcards
What are nucleic acids?
Nucleic acids are a group of important molecules, most commonly DNA and RNA. They are information carrying molecules.
What are ribosomes made from and where are they found?
Ribosomes are molecules made from RNA and proteins which transfer information from DNA to ribosomes.
What are the 3 components of a nucleotide?
1) A pentose sugar
2) A phosphate group
3) A nitrogen-containing organic base
What is the reaction which forms nucleotides?
Condensation reaction
What is the bond which forms between two nucleotides joined to each other?
Phosphodiester bond
What are the 4 DNA organic bases? Why do they pair together?
Adenine Thymine Cytosine Guanine The base pairs are complementary
What are the 4 RNA organic bases?
Adenine Guanine Cytosine Uracil
Describe the structure of DNA:
- Two DNA strands curled in a double helix formation. - Sugar and phosphate form a ‘sugar-phosphate backbone’. - Opposite bases are joined by hydrogen bonds.
Who worked out the structure of DNA?
James Watson Francis Crick (Following the work of Rosalind Franklin)
What is the function of DNA and where is it found?
DNA is a hereditary material which is responsible for passing genetic information between cells and generations.
How is DNA adapted to carry out its function?
- Very stable structure
- 2 seperate strands joined by hydrogen bonds (so they can separate during replication)
- Extremely large molecule
- Base pairs ‘protected’ by helica cylinder
- Base pairing makes DNA replicatin and transfer of information easier and more efficient
Define nuclear division:
The process by which he nucleus divides. This includes mitosis and meiossis.
Define cytokinesis:
The process following nuclear division in which the whole cell divides.
What is semi-conservative DNA replication?
Repliation of a double stranded molecule of nucleic acid, separating into single strands which serve as a replicaion template for the formation of another complementary strand onto each original strand.
What are the four requirements for semi-conservative replication?
- Four types of nucleotide (A,T,C,G)
- Both strands of the DNA molecule act as a template
- The enzyme DNA polymerase
- A source of chemical energy
Outline the process of semi-conservative replication:
1) The enzme DNA helicase breaks hydrogen bonds between base pairs
2) Double helix separates
3) Each exposed polynuleotide strand acts as a template for the complementary nucleotide
4) The enzyme DNA polymerase joins nucleotides together in a condensation reaction.
5) Each new DNA molecule contains one new and one old strand.
It is called semi-conservative replication as only half of the original DNA has ben saved.
What is ATP?
A phosphorylated macromolecule which is the main energy source in both animal and plant cells.
What are the three parts of an ATP moleule?
- Adenine: Nitrogen containing organic base
- Ribose: A sugar moleule with a pentose sugar which acts as a backbone
- Phosphates: A chain of three phosphate groups
What is the equation for the release of energy via the hydrolysis of ATP?
ATP + (H2O) —–> ADP + Pi + (energy)
What features of ATP make it a suitable source of energy for living organisms?
- It has a low activation energy so is easily broken down
- It is unstable so is easily broken down
- It releases energy in small, manageable amounts
- It releases energy in a single, simple reaction
- It is an immediate energy source (isn’t stored)
- It is soluble so can be used in cells
What reacton takes place to break down ATP?
Hyrolysis catalysed by ATP hydrolase
What reaction takes place to synthesise ATP?
Condensation with the enzyme ATP synthase
Where does ATP synthesis occur?
- In chlorophyll-containing plant cells durng photosynthesis (phosphorylation)
- In plant and animal cells during respiration (oxidative phosphorylation)
- In plant and animal cells during the transfer of phosphate groups between cells (substrate-level phosphorylation)
Name and describe 5 energy-requiring processes where ATP is used:
1) Metabolic processes: building of marcromolecules
2) Movement: energy for muscle contraction (i.e. filaments sliding across each other)
3) Active transport: energy changes shape of carrier protiens and allows molecules to move against concentration gradient
4) Secretion: ATP forms lysosomes which secrete cell products
5) Activation of molecules: Pi can phosphorylate other compounds and lower their activation energy. Pi is released during the hydrolysis of ATP
What is water?
Water is a major component of cells, a metabolite and a solvent for many metabolic reactions
Why is water described as dipolar?
Oxygen has a slight negative charge while hydrogen has a slight positive charge
How do different water molecules bond to each other?
The positive pole of one binds to the negative pole of another forming a hydrogen bond. It is a fairly weak bond but appears srong when there are many of them
Describe the specific heat capacity of water:
The SHC of water is relatively high since the water molecules stick together. This means it takes a lot of energy to raise the temperature of it. This is due to the hydrogn bonds.
Water, therefore, acts as a buffer against suden temperature change in an aquatic habitat and inside organisms
Describe the latent heat of vaporisation of water:
The LHV of water is also relatively large as lots of energy is required to evaporate a gram of water. This means that mammals can sweat to provide a cooling effect without the issue of evaporation.
Define cohesion:
The tedency of molecules to stick to one another (e.g. water)
Why is water so cohesive?
Many hydrogen bonds
Give an example of the cohesion of water:
Xylem vessels
Define surface tension:
A force on the surfae film of a quid caused by the attraction of the particles
Give an example of a use for the high surface tension of water:
Habitat fo small organisms such as pond skaters
Why is water important to livng organisms?
It is the main constituent of all organisms
How is water used in reactions (metabolism)
- It is used in molecule break down and building (hydrolysis and condensation)
- Many chemicl reactions take place in it
- It is a raw material for photosynthesis
Give 2 examples of water as a solvent:
1) Removal of waste products such as ammonia and urea
2) Gases such as oxygen and carbon dioxide dissolve in water
Why is water useful in photosynthesis (other than being a raw material)?
It is transparent so aquatic plants can photosynthesise in it
Inorganic ions ocur in a range of concentrations in a water-based solution. Give 5 examples of functions of inorganic ions:
Iron ions in haemoglobin- oxygen transportation
Phosphate ions- structural role in DNA molecules and store energy in ATP
Hydrogen ions- pH
Sodium ions- co transport
Sodium and potassium ions- action potential (nerve impulse)
