2 nucleic acids (concepts) Flashcards Preview

A Level Biology > 2 nucleic acids (concepts) > Flashcards

Flashcards in 2 nucleic acids (concepts) Deck (15):
1

nucleotides made up of... (3)

pentose sugar
phosphate group
nitrogenous base

2

RNA structure (4)

single-stranded
shorter
ribose sugar
AUGC

3

DNA structure (4)

double-stranded, alpha double helix, 2 polynucleotide chains (H bonds present between specific comp base pairs)
longer
deoxyribose sugar
ATGC

4

DNA is stable bc... (2)

phosphodiester backbone protects the more chemically reactive organic bases inside the double helix

hydrogen bonds link the base pairs forming bridges (rungs) between phosphodiester uprights - the higher the proportion of C-G pairings, the more stable the DNA due to the 3 H bonds between them

5

DNA adapted to carry out functions by... (5)

very stable, rarely mutates

2 strands joined by hydrogen bonds, can separate for DNA rep/protein synth

very large molecule, lots of genetic info carried

sugar phosphate backbone protects the more chemically reactive bases from outside chem/phys forces from corruption

base pairing leads to DNA being able to replicate and transfer info as mRNA

6

2 stages of cell division

nuclear division (nucleus divides - mitosis/meiosis)
cytokinesis (the whole cell divides)

7

requirements for semi-conservative replication (4)

the four types of nucleotide, with bases of ATGC
both strands of DNA molecule
DNA polymerase (helicase, ligase, gyrase)
a source of chemical energy to drive the process

8

semi-conservative replication (4)

DNA helicase breaks the H bonds joining the complementary bases together in the polynucleotide strands and causes the 2 polynucleotide strands of the DNA double helix to unwind and separate

each exposed polynucleotide strand acts as a template to which complementary free nucleotides that have been activated, get attracted to and bind to it by specific base pairing (A to T, G to C)

adjacent nucleotides are joined together by phosphodiester bonds in condensation reactions by DNA polymerase

two identical molecules of DNA are formed with half original DNA and half new DNA = semi-conservative replication

9

3 parts of ATP

adenine base
ribose sugar
3 phosphate groups

10

when ATP is synthesised (3)

photophosphorylation (in photosynthesis)

oxidative phosphorylation (in respiration)

substrate-level phosphorylation (when phosphate molecules are transferred from donor molecules to ADP)

11

ATP better immediate energy source because... (2)

each molecule releases less energy than a glucose molecule - smaller more manageable quantities.

hydrolysis of ATP to ADP is a single reaction but glucose breakdown is a long series of reactions -
releases immediate energy.

12

ATP is used for... (5)

metabolic processes - energy to build macromolecules from basic units e.g. starch from glucose

movement - energy for muscle contraction for muscle filaments to slide past each other and shorten length of a muscle fibre

active transport - energy to change shape of carrier proteins in plasma membs allowing molecules to be moved across a conc grad

secretion - needed to form lysosomes for the secretion of cell products

activation of molecules - Pi released used to phosphorylate other compounds to make them more reactive, lowering Ea in enz-cat reactions e.g. addition of phosphate to glucose in glycolysis

13

structure of water (2)

dipolar (delta -ve O and delta +ve H)

hydrogen bonds (+ve pole of one molecule attracts -ve pole of another)

14

importance of water to living organisms (7)

metabolism: metabolite in met reactions
break down complex molecules by hydrolysis
chemical reactions take place in aq medium
major raw material in photosynthesis

solvent: in which metabolic reactions occur
readily dissolves gases (co2, o2), wastes (ammonia, urea), inorganic ions & small hydrophillic molecules (aa's, monosaccharides, ATP), enz (whose reactions take place in solution)

evaporation:
cools organisms for temp control
latent heat of vaporisation (requires a lot of energy to evaporate 1g of water: cooling effect w little loss of water through evap)(sweat is an effective means of cooling as body heat evaporates the water)

incompressible:
support e.g. hydrostatic skeleton of earthworm, turgor pressure in herb plants

transparent:
aq plants can photosynthesise, light rays penetrate jelly-like fluid and reach retina

specific heat capacity (water molecules stick together, takes more energy to separate them - takes more energy to heat a given mass of water: acts as a buffer against sudden temp changes for aquatic envs & buffers organisms against sudden temp changes as they are mostly water

cohesion & surface tension (the tendency of molecules to stick together: supports columns of water in tube-like transport cells of plants/water pulled up the xylem vessels) & (where water meets air, water pulled back into the body of water: water surface acts as a skin, strong enough to support pond skaters)

15

roles of inorganic ions (1+5)

occur in sol in cytoplasm of cells and in body fluids and part of larger molecules in organisms, some in high concs, some in low

each ion has specific role dep on its properties:
e.g. iron in haemoglobin for o2 transport
e.g. phosphate in DNA as structural role
e.g. phosphate in ATP as energy storing
e.g. hydrogen in pH and functioning of enz
e.g. sodium in co-transport of glucose and aa's across plasma membs