(1) biological molecules: Nucleic Acids

Question 1

What is ATP, and what is it made of?

Answer 1

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

Question 2

How does ATP store energy?

Answer 2

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

Question 3

How is ATP made from ADP?

Answer 3

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

Question 4

How is the synthesis of ATP a reversible reaction?

Answer 4

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

Question 5

Why is ATP considered as an immediate energy source?

Answer 5

Only one bond has to be hydrolyses to release energy

Question 6

What are the properties of ATP?

Answer 6

1. energy is released in small amounts (no energy is wasted, cells do not overheat from wasted heat energy)
2. ATP can be reformed, as it is a reversible reaction
3. immediate reaction: only one bond broken/hydrolysed to release energy
4. can transfer energy to another molecule through phosphorylation, making other compounds more reactive

Question 7

Structure of water: how is it a dipolar molecule?

Answer 7

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

Question 8

why is water a very stable structure?

Answer 8

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

Question 9

properties of water:
specific heat capacity

Answer 9

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

Question 10

properties of water
high latent heat of vaporisation

Answer 10

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

Question 11

properties of water:
cohesion

Answer 11

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

Question 12

Properties of water:
surface tension

Answer 12

produced by cohesion where air molecules meet water, supports organisms e.g pond skaters

Question 13

properties of water:
solvent

Answer 13

readily dissolved other substances [gases, wastes (ammonia, urea)]
dissolves inorganic ions and small hydrophilic materials such as amino acids and monosaccharides

Question 14

properties of water
transparent

Answer 14

allows aquatic plants to gain sunlight in order to use for photosynthesis

Question 15

what is the role of iron ions as a component of haemoglobin?

Answer 15

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

Question 16

what is the role of sodium ions in co-transport of glucose and amino acids

Answer 16

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.

Question 17

what are the role of phosphate ions as components of DNA and ATP

Answer 17

-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.

Question 18

role of hydrogen ions and ph

Answer 18

(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

Question 19

what are nucleotides?

Answer 19

nitrogen containing organic substances that form the basis of the nucleic acids DNA and RNA

Question 20

what are the purine bases? ( 2 ring)

Answer 20

adenine
guanine

Question 21

what are the pyrimidine bases? (1 ring)

Answer 21

thymine
cytosine
uracil

Question 22

how are nucleotides formed?

Answer 22

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

Question 23

how are polynucleotides formed?

Answer 23

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

Question 24

what is chargraff’s rule?

Answer 24

the % quantity of adenine = thymine
% quantity of guanine = cytosine

Question 25

how is DNA packaged?

Answer 25

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)

Question 26

what are the characteristics of DNA?

Answer 26

bases A T G C
2 sugar phosphate backbones
complementary base pairs join to form a double helix shape
made of deoxyribose sugar

Question 27

what are the characteristics of RNA

Answer 27

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

Question 28

what is the process of DNA replication?

Answer 28

1. helicase enzyme separates the 2 DNA strands (point that they were separated is called the replication fork)
2. each strand is kept part by SBB proteins (single strand binding)
3. formation of new strands is catalysed by DNA polymerase
4. 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
5. 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
6. the okazaki fragments are joined toether by DNA ligase
7. 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

Question 29

what was the meselson-stahl experiment?

Answer 29

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

Question 30

what were the expected outcomes for the M-S experiment?

Answer 30

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.