(1) biological molecules: Nucleic Acids Flashcards
What is ATP, and what is it made of?
Adenosine Triphosphate = nucleotide derivative
adenine: nitrogen containing base
ribose: pentose sugar ( 5 carbon) - acts as backbone to which other parts are attached
phosphate: 3 groups, inorganic and do not contain any carbon atoms
How does ATP store energy?
in the triphosphate group, the bonds between them are unstable and enable low activation energy, meaning they are easily broken. When broken, it releases a considerable amount of energy
How is ATP made from ADP?
ADP + Pi + E -> ATP + H2O
inorganic phosphate group added to convert ADP to ATP (phosphorylation)
Anabolic reaction: small molecule to large molecule
Condensation reaction (water is removed)
catalysed by the enzyme ATP synthase
How is the synthesis of ATP a reversible reaction?
ATP = recycled
hydrolysis reaction: water is used to convert ATP to ADP, where reaction is catalysed the the enzyme ATP hydrolase,
catabolic reaction: large molecule into small molecule
by breaking one of the bonds between an inorganic phosphate groups, a small amount of releases to the surroundings
Why is ATP considered as an immediate energy source?
Only one bond has to be hydrolyses to release energy
What are the properties of ATP?
- energy is released in small amounts (no energy is wasted, cells do not overheat from wasted heat energy)
- ATP can be reformed, as it is a reversible reaction
- immediate reaction: only one bond broken/hydrolysed to release energy
- can transfer energy to another molecule through phosphorylation, making other compounds more reactive
Structure of water: how is it a dipolar molecule?
different charged regions:
O2 ha a greater affinity for electrons because of its +ve charge in the nucleus’ allowing electrons to be attracted to it at having a slightly negative charge
H= slightly positive
why is water a very stable structure?
the attractive forces between the molecules is a hydrogen bond and all though it is weak, many bonds cause H2O molecules to stick together and the numerous hydrogen bonds make it very stable
properties of water:
specific heat capacity
hydrogen bonds between molecules mean they stick together so more energy/heat is needed to break them apart
e.g acts as a buffer against sudden temperature changes and makes environment a stable temperature one
properties of water
high latent heat of vaporisation
hydrogen bonding between molecules meaning it
requires a lot of energy to evaporate 1g of water
e.g body heat is used to evaporate water, produces sweat as a cooling effect
properties of water:
cohesion
the tendency molecules to stick together and with waters hydrogen bonding, water has large cohesive forces
allow water to be pulled up a xylem vessel e.g
Properties of water:
surface tension
produced by cohesion where air molecules meet water, supports organisms e.g pond skaters
properties of water:
solvent
readily dissolved other substances [gases, wastes (ammonia, urea)]
dissolves inorganic ions and small hydrophilic materials such as amino acids and monosaccharides
properties of water
transparent
allows aquatic plants to gain sunlight in order to use for photosynthesis
what is the role of iron ions as a component of haemoglobin?
haemoglobin = protein that transports oxygen in human blood from lungs to tissues of the body, consisting of 4 subunits with each unit having a heme group with 1 iron atom which is able to bond to one oxygen molecule, each haemoglobin can bond up to 4 O2 molecules
what is the role of sodium ions in co-transport of glucose and amino acids
the process of co-transport allows small molecules to move into the cell from, an area of low to high concentration. Na+ ions move down the concentration gradient using a co-transport protein. 2 Na+ and a glucose molecule must bind before they can be transported across the membrane.
what are the role of phosphate ions as components of DNA and ATP
-it’s the bonds between phosphate groups that store energy in ATP.
-the phosphate groups in DNA and RNA allow nucleotides to join up to form polynucleotides.
role of hydrogen ions and ph
(H+) help control pH in digestion. Hydrogen ions are also important for maintaining the low pH of the gastric juices within the stomach which is important for digestion
what are nucleotides?
nitrogen containing organic substances that form the basis of the nucleic acids DNA and RNA
what are the purine bases? ( 2 ring)
adenine
guanine
what are the pyrimidine bases? (1 ring)
thymine
cytosine
uracil
how are nucleotides formed?
the sugar and base join together by a condensation reaction, creating a nucleoside and one molecule of water
phosphoric acid joins the nucleoside forming a phosphoester bond between the OH group on the acid and the OH group on carbon 5 of the sugar
creating a nucleotide and water
how are polynucleotides formed?
2 nucleotides join in a condensation reaction creating a phosphodiester bond between the OH group on the phosphate group of one nucleotide and the OH group on carbon 3 of the other nucleotide
what is chargraff’s rule?
the % quantity of adenine = thymine
% quantity of guanine = cytosine
how is DNA packaged?
in eukaryotic cells, packaged in chromosomes in nucleus
2m of DNA in cell which needs to be tightly coiled and folded
associated w histones (proteins) together form chromatin (makes chromosomes)
what are the characteristics of DNA?
bases A T G C
2 sugar phosphate backbones
complementary base pairs join to form a double helix shape
made of deoxyribose sugar
what are the characteristics of RNA
bases A U G C
one sugar phosphate backbone only
only has one strand: it can bend and change shape in order for base pairs to join up
these shapes make tRNA, mRNA, rRNA
what is the process of DNA replication?
- helicase enzyme separates the 2 DNA strands (point that they were separated is called the replication fork)
- each strand is kept part by SBB proteins (single strand binding)
- formation of new strands is catalysed by DNA polymerase
- DNA polymerase reads the parent strand in a 3’ to 5’ direction and builds the leading strand in a 5’ to 3’ direction towards the replication fork
- in contrast the lagging strand is built in a 3’ to 5’ direction away from the replication fork
it grows discontinuously in small sections called okazaki fragments - the okazaki fragments are joined toether by DNA ligase
- the DNA helix continues to unwind and separate
the leading strand grows continuously towards the replication fork while the lagging strand grows discontinuously away from the fork
what was the meselson-stahl experiment?
objective: To investigate the mode of DNA replication
Isotope Labeling: They used heavy isotopes of nitrogen (^15N) to label the DNA in E. coli. The bacteria were grown in a medium containing ^15N as the sole nitrogen source. This incorporation of ^15N into the DNA made it distinguishable from DNA containing the more common lighter isotope, ^14N.
Transfer to Lighter Isotope Medium: The labeled bacteria were then transferred to a medium containing the lighter isotope of nitrogen (^14N) and allowed to undergo several rounds of replication
what were the expected outcomes for the M-S experiment?
Conservative: If DNA replicated conservatively, after one round of replication, one set of DNA molecules would consist entirely of ^14N DNA and the other set entirely of ^15N DNA.
Semi-conservative: If DNA replicated semi-conservatively, after one round of replication, each DNA molecule would consist of one strand of ^15N-labeled DNA and one strand of newly synthesized ^14N DNA.
Dispersive: In a dispersive replication scenario, the DNA strands would contain mixed fragments of ^14N and ^15N.
