nucleic acids- chpater 2 Flashcards
what are the components make up the nucleotide structure
-pentose sugar
-a phosphate group
-a nitrogen containing organic base= cytosine, thymine, uracil, adenine, guanine
how are the components of the nucleotide structure joined together
a condensation reaction
what may the two mononucleotides join together between
the deoxyribose sugar and the phosphate group of another by condensation reaction
what bond is formed in the condensation reaction of two mononucleotides
a phosphodiester bond
what makes up the ribonucleic acid structure
-polymer made up of nucleotides
-single, relatively short, polynucleotide chain
what is the pentose sugar always
always ribose
what are the organic bases for RNA
guanine, cytosine and uracil
what are 3 functions of RNA
- transferring genetic information from DNA to ribosomes
-ribosomes themselves are made up of proteins and another type of RNA
-RNA is also involved in protein synthesis
who worked out the structure of DNA
watson and crick
what is the pentose sugar for DNA
deoxyribose
what are the organic bases for DNA
adenine, thymine, guanine and cytosine
what is DNA made up of
two strands of nucleotides (polynucleotides) that are extremely long and joined by hydrogen bonds
what do the bases on the two strand attached by
hydrogen bonds
what does adenine pair with
thymine
what does guanine pair with
cytosine
why is DNA a stable molecule (long answer)
-the phosphodiester backbone protects the more chemically reactive organic bases inside the double helix
-hydrogen bonds link the organic base pairs-forming bridges between the phosphodiester uprights. As there are three hydrogen bonds between cytosine and guanine, the higher the proportion of C-G pairings, the more stable the DNA molecule.
how many hydrogen bonds are between cytosine and guanine
3
how many hydrogen bonds are between adenine and thymine
2
why is it good good that DNA is very stable
it passes from generation to generation without significant change
why is it good that there are two separate strands in DNA
as they’re only joined by hydrogen bonds it allows them to separate during DNA replication and protein synthesis
why is it good that DNA molecules are extremely large
carries an enormous amount of genetic information
why is it good that there are base pairs within the helical cylinder of the deoxyribose-phosphate backbone
means the genetic information is somewhat protected from being corrupted by outside chemical and physical forces
why is it good that DNA has base pairings
leads to DNA being able to replicate and transfer information as mRNA
what two stages happens in cell divison
nuclear division and cytokinesis
what is nuclear division
process by which the nucleus divides, mitosis and meiosis
what is cytokinesis
follows nuclear division and is the process by which the whole cell divides
what are the four requirements for semi-conservative replication to take place
-four types of nucleotides
-both strands of DNA molecule
-the enzymes DNA polymerase
-a source of energy to drive the process
describe how semi-conservative replication takes place
- the enzyme DNA helicase breaks the hydrogen bonds linking the base pairs of DNA. The two strands separate and unwind
- each exposed polynucleotide then acts as a template to which complimentary free nucleotides bind to their specific base pair
- nucleotides are joined together in a condensation reaction by the enzyme DNA polymerase
- each of the new DNA molecules contains one of the original DNA strands that is half the original DNA. Hence the term semi-conservation replication
what is the structure of ATP
a phosphorylated macromolecules which has 3 parts
what are the 3 parts of ATP and describe them
- adenine- nitrogen containing organic base
- ribose- a sugar molecule with a 5-carbon ring structure (pentose) that acts as a backbone to which the other parts are attached
- phosphates- a chain of 3 phosphate groups
describe how ATP is used in metabolic processes
energy needed to build up macromolecules from their basic units
describe how ATP is used in movement in cells
provides energy for muscle contraction
ATP provides the energy for the filaments of muscle to slide past one another
describe how ATP is used in active transport
provides energy to change the shape of the carrier proteins in plasma membranes
describe how ATP is used in secretion
ATP is needed to form the lysosomes necessary for the secretion of cell products
how is ATP used in the activation of molecules
inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds in order to make them more reactive, lowering the activation energy in enzyme-catalysed reactions e.g. addition of phosphate to glucose molecules at the start of glycolysis
what are 5 processes ATP is used in
metabolic processes, movement, active transport, secretion, activation of molecules
what type of reaction is the conversion of ATP to ADP and why is this good
reversible which therefore energy can be used to add inorganic phosphate
why is the conversion of ATP to ADP catalysed by
ATP synthase
what type of reaction is ATP to ADP
condensation reaction
where does the synthesis of ATP occur (three ways)
- in chlorophyll containing plant cells during photosynthesis (photophosphorylation)
- in plant and animal cells during respiration (oxidative phosphorylation)
- in plant and animal cells when phosphate groups are transferred from donor molecules to ADP (substrate-level phosphorylation)
what is good about the bonds between the phosphate groups
the bonds are unstable and so have a low activation energy which means they are easily broken and when they are broke they release a considerable amount of energy
what is the reaction from ATP to ADP
ATP + H2O 🡪 ADP + Pi + E
Adenosine triphosphate + water 🡪 adenosine diphosphate + inorganic phosphate + energy
what type of reaction is ATP to ADP and why
hydrolysis and water is used
what enzyme is used yo catalyse the hydrolysis reaction of ATP to ADP
ATP hydrolase
what type of energy source is ATP
immediate source of energy not good long term
do cells store large quantities of ATP
no as it is formed rapidly
where is ATP made
within the mitochondria and cannot be stored so is constantly made
why is ATP a better immediate energy source than glucose
- each ATP molecule releases less energy than glucose so the energy is released in smaller, more manageable quantities rather than the much greater and less manageable release of energy from a glucose molecule
- the hydrolysis of ATP to ADP is a single reaction that releases immediate energy, the breakdown of glucose is a long series of reactions and therefore the energy release takes longer
what is the structure of a water molecule (dipolar)
made up of two atoms of hydrogen and one of oxygen
what is the charges within a water molecule
-overall no charge
-oxygen has a slight negative charge
-hydrogen has slight positive charge
how is the hydrogen bonding formed in a water molecule
-the positive pole of one water molecule will be attracted to the negative pole of another water molecule
-each bond is fairly weak although they form important forces that cause the water molecule to stick together
why is the boiling point in water higher than expected
as the water molecules stick together so it takes more energy to separate them
what does water acts as against temperature variations
a buffer which makes the aquatic environment a temperature-stable one
explain latent heat of vaporisation in water and explain why sweat is effective
-hydrogen bonding between water molecules means it requires a lot of energy to evaporate
-evaporation of water such as sweat is therefore very effective means of cooling because heat is used to evaporate the water
what forces does water have
large cohesive forces
what does large cohesive forces mean for water
allows it be pulled through a tube (xylem)
what is surface tension
-where water molecules meet air they tend to be pulled back into the boys rather than escaping
-means that the water surfaces acts like a skin and is strong enough to support small organisms (eg pond skater)
what is the importance of water in metabolism
-used to break down many complex molecules by hydrolysis
-chemical reactions take place in an aqueous medium
-water is a major raw material in photosynthesis
what is the importance of water as a solvent
water readily dissolved other substances
-gases i.e oxygen and carbon dioxide
-wastes i.e oxygen and carbon dioxide
-inorganic ions and small hydrophilic molecules i.e amino acids, monosaccharides and ATP
-enzymes, whose reactions take place in solution
why is it good water is not easily compressed
so provides support
why is it good that water is transparent
means aquatic plants can photosynthesis and also light rays penetrate the jelly like fluid of the eye
why is water good at evaporation
cools organisms and allows them to control their temperature
where are inorganic ions found
in organisms where they occur in solution in the cytoplasm of cells and in body fluids
what do inorganic ions perform
perform a range of function which are related to their own properties
i.e iron found in haemoglobin where they transport oxygen
