Nucleic acids

Question 1

What are the 2 purine bases

Answer 1

Adenine and guanine

Question 2

What are the pyrimidine bases

Answer 2

cytosine and thymine/uracil

Question 3

What is a nucleotide

Answer 3

monomer of nucleic acids with a pentose sugar a nitrogenous base and a phosphate group

Question 4

What are the components of a nucleotide

Answer 4

a phosphate group
A nitrogenous base
Pentose sugar

Question 5

what are chemoautotrophic organisms

Answer 5

Organisms that use energy from oxidation of electron donors eg bacteria

Question 6

What is the structure of ATP

Answer 6

three phosphate groups
Base
Ribose sugar

Question 7

What are the roles of ATP

Answer 7

metabolic processes like building proteins from amino acids
Movement - muscle contraction
Active transport -changing shape of carrier proteins

Question 8

What are the advantages of ATP

Answer 8

only 1 enzyme is needed to release the energy in ATP
Releases energy in small amounts
Common source of energy in most chemical reactions

Question 9

where does ATP transfer energy

Answer 9

from energy rich compounds e.g glucose to cellular reactions

Question 10

what are the issues with energy transfer from glucose

Answer 10

energy transfers are inefficient so energy is lost through heat
energy release from glucose is uncontrollable so it would produce enough heat to destroy a cell

Question 11

what is the structure of DNA

Answer 11

2 polynucleotide strands wound round each other to form a double helix
deoxyribose sugar and phosphate groups are on the outside of the molecule and form the backbone
the two strands are antiparalell

Question 11

how many hydrogen bonds are between cytosine and guanine

Answer 11

3

Question 12

how many hydrogen bonds are between adenine and thymine

Answer 12

2

Question 13

why is DNA suited for its functions

Answer 13

it is a large molecule so it carries alot of genetic info
two strands can seperate as they are held together by hydrogen bonds
backbone protects the genetic information inside

Question 14

what is the structure of RNA

Answer 14

a single polynucleotide
contains the sugar ribose
has uracil instead of thymine

Question 15

what are the 3 types of RNA

Answer 15

messenger-mRNA
transport-tRNA
ribosomal-rRNA

Question 16

What is mRNA

Answer 16

synthesised in the nucleus and carries genetic code from DNA to ribosomes in the cytoplasm

Question 17

what is rRNA

Answer 17

found in cytoplasm and made up of large complex molecules
made up of proteins and ribosomal rna
site of translation of genetic code onto protein

Question 18

what is tRNA

Answer 18

transfer RNA
small single stranded molecule that folds so that base sequences form complementary pairs
carries the anticodon
transports specific amino acids to the ribosomes in protein synthesis

Question 19

what is an anticodon

Answer 19

groupf of three bases on a tRNA molecule that corellates with the specfic amino acid being carried

Question 20

what is the functions of DNA

Answer 20

replication and protein synthesis

Question 21

when is DNA replicated

Answer 21

during interphase in the nucleus

Question 22

what is conservative replication

Answer 22

parental double helix remains intact and a whole new double helix is made

Question 23

what is semi conservative replication

Answer 23

parental double helix seperates into 2 strands which each act as a template for a new strand

Question 24

What is dispersive replication

Answer 24

two new double helicies contain fragments from both strands of the parental double helix

Question 25

What is a gene

Answer 25

a section of DNA on s chromosone which codes for a specific polypeptide

Question 26

What are the characteristics of the genetic code

Answer 26

three bases encode each amino acid so the code is a triplet code Stop codons Code is universal Non overlapping because each base only occurs in one triplet

Question 27

What is an Extron

Answer 27

coding region in the nucleotide sequence of DNA and pre-mRNA that remains present in the final nature mRNA after introns removed

Question 28

What is an intron

Answer 28

non coding nucleotide sequence in DNA and pre mRNA that is removed from pre MRNA to produce mature mRNA

Question 29

What happens in translation

Answer 29

the sequence of codons on the mRNA is is used to generate a specific sequence of amino acids forming a polypeptide

Question 30

Where does translation occur

Answer 30

on a ribosome

Question 30

What is each ribosome made up of

Answer 30

two subunits Larger one has two sites of attachment of tRna molecules Smaller subunit binds to mRNA

Question 31

What are the three stages of translation

Answer 31

initiation Elongation Termination

Question 32

what happens in initation

Answer 32

a ribosome attaches to start codon at one end of the mRNA molecule

Question 33

what happens in elongation

Answer 33

the two amino acids are sufficiently close for a ribosomal enzyme to catalyse the formation of a peptide bonds between them

Question 34

what happens in termination

Answer 34

sequence repeats until a stop codon is reached

Question 35

what is amino acid activation

Answer 35

once tRNA is released from the ribosome it is free to collect another amino acid from the cytoplasm , energy from ATP is needed to attach the amino acid to the tRNA

Question 36

what is post translational modification

Answer 36

polypeptides on the ribosome are are transported through the cytoplasm to the golgi and can be folded in to secondary, tertiary or quaternary structure e.g haemoglobin- 4 polypeptides combined

Question 37

what are the functions of proteins in living organisms

Answer 37

hormones, enzymes,antibodies

Question 38

what is the difference between DNA and RNA

Answer 38

rna has uracil Instead of thymine rna single stranded DNA double stranded rna has ribose sugar DNA has deoxyribose

Question 39

how does ATP release energy

Answer 39

when energy is required ATPase hydrolyses the bonds between the 2nd and 3rd phosphate group to create adenosine diphosphate which is an exergonic reaction and releases 30.6 kj of energy