Unit 1 .5 nucleic acids and their functions

Question 1

what are nucleotides made out of?

Answer 1

one or more phosphate group (A)
pentose sugar
an organic base which contains nitrogen (C)

Question 2

what is ATP?

Answer 2

Major currency of the cell - provides energy for most reactions in most cells.

Question 3

Diagram of ATP

Answer 3

Phosphate group = represented by W
Pentose Sugar = ribose , represented by Y
Z = organic base called adenine
Bond X = formed by condensation reaction

Question 4

To release energy from ATP

Answer 4

ATPase breaks the bond between the middle and terminal phosphate group ; this releases energy. ASP and Pi = formed too

Question 5

Reversible reaction?

Answer 5

ADP and Pi can reform ATP molecules but energy = needed. Energy comes from the breakdown of glucose during respiration or from protons of light during photosynthesis

Question 6

what does ATP provide energy for?

Answer 6

metabolic processes - to build large, complex molecules from smaller , simpler molecules e.g synthesis of DNA from nucleotides
Active transport - to change the shape of carrier proteins in cell membranes to allow molecules and ions to be transported against a concentration gradient
Movement - for muscle contraction
Nerve transmission - sodium potassium pumps actively transport sodium and potassium ions across the axon cell membrane
Secretion - the packaging and transport of secretory products into vesicles in cells

Question 7

Advantages of using ATP energy

Answer 7

the hydrolysis of ATP to ADP involves a single reaction that releases immediate energy
only 1 enzyme (ATPase) is needed to release energy from ATP, while many are needed in the case of glucose
ATP releases energy in small amounts when and where needed, whereas glucose contains large amounts of energy that may not be needed immediately.
ATP = soluble and easily transported
common source of energy for many different chemical reactions

Question 8

what are the 2 types of nucleic acids?

Answer 8

Dexoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)

Question 9

diagram of nucleotides

Answer 9

CIRCLE = PHOSPHATE GROUP
PENTAGON = PENTOSE SUGAR
RECTANGLE = ORGANIC BASE CONTAINING NITROGEN

Question 10

what do DNA nucleotides have?

Answer 10

pentose sugar deoxyribose and the bases adenine, thymine, cytosine or guanine.

Question 11

what do RNA nucleotides have?

Answer 11

pentose sugar ribose and the bases adenine, uracil, cytosine and guanine

Question 12

what are Adenine and Guanine?

Answer 12

purine bases with a double ring structure

Question 13

what are thymine, uracil and cytosine?

Answer 13

pyrimidine bases with a single ring structure

Question 14

what bonds with what?

Answer 14

Pyrimidine base must bond with a purine base
adenine bonds with thymine or uracil (2H bonds)
cytosine bonds with guanine (3H bonds)

Question 15

what is DNA?

Answer 15

Double stranded polymer of nucleotides or polynucleotide

Question 16

how is DNA structured?

Answer 16

4 different bases each contain nitrogen - adenine, guanine, cytosine and thymine
purine bases bond with pyrimidine bases by hydrogen bonding
Adenine bonds w thymine and guanine bonds w cytosine - complimentary base pairing
base
base pairing links 2 polynucleotide chains
polynucleotide chains = antiparallel to each other
molecule = twisted to form a double helix
shape = maintained by hydrogen bonding

Question 17

where is DNA is found ?

Answer 17

the nucleus of eukaryotic cells

Question 18

what has the 2 functions?

Answer 18

replication and protein synthesis

Question 19

What is RNA

Answer 19

a single stranded polynucleotide
contains pentose sugar ribose
contains organic bases adenine, guanine, cytosine and uracil
doesn’t contain base thymine
much shorter than DNA

Question 20

What are the different types of RNA?

Answer 20

mRNA (messenger RNA)- long single stranded molecule. synthesised in the nucleus and carries the genetic code from the DNA to the ribosomes in the cytoplasm
rRNA (ribosomal RNA) - found in the cytoplasm and is a component part of ribosomes. Ribosomes = made of rRNA and protein and are synthesised in the nucleolus of the nucleus. Ribosomes = site of protein synthesis by a process called translation)
tRNA (transfer RNA)-small single stranded molecule folded into shape of a clover leaf. Each tRNA molecule has an amino acid attachment site CCA. at opposite end of tRNA molecule = triplet of bases called an anticodon. tRNA molecules transport amino acids to the ribosomes. anticodon bases form a complex with complimentary bases on the mRNA molecule. allows translation to take place

Question 21

DNA replication?

Answer 21

hydrogen bonds holding the base pairs together break and 2 halves of the DNA molecule seperate
DNA unwinds
as DNA strands seperate the enzyme DNA polymerase catalyses addition of free nucelotides to the exposed bases; each chain acts as a template so that free nucleotides can be joined to their complimentary bases
process results in the formation of 2 identical DNA molecules ; each made up of one newly synthesised chain and 1 chain from the original molecule

Question 22

what did meselson and stahil propose?

Answer 22

the semi conservative hypothesis of DNA replication. where each DNA strand at as a template for new DNA. each strand = composed of an original strand and a newly synthesised strand.

Question 23

what requires the transcription of a gene into a mRNA molecule from the original DNA template?

Answer 23

Protein synthesis

Question 24

what is Transcription?

Answer 24

Where DNA doesn’t leave the nucleus and accts as a template for the production of mRNA. This is then copied from a specific region of DNA to a cistron ( gene and codes for a specific polypeptide)

Question 25

Transcription?

Answer 25

The DNA unwinds and unzips at a particular region to be copied ; catalysed by an enzyme called helicase (breaks h bonds between complimentary bases)
the enzyme RNA polymerase attaches to the DNA at the beginning of the sequence
to be copied.
Only one of the DNA strands acts as the template to be copied.
Transcription occurs when free RNA nucleotides align themselves opposite
complimentary nucleotides on the DNA strand.
RNA polymerase moves along the DNA forming bonds that add nucleotides one at a
time to the RNA.
This results in the synthesis of a molecule of mRNA alongside the unzipped portion of
DNA.
Behind the RNA polymerase the DNA strands re-join to reform the double helix.
The mRNA carries the DNA code out of the nucleus through a nuclear pore to the
cytoplasm and attaches itself to a ribosome.

Question 26

Translation?

Answer 26

The ribosome acts as a framework moving along the mRNA, reading the code.
mRNA contains triplet codes or codons. Each codon codes for a different amino
acid.
tRNA (transfer RNA) molecules attach to specific amino acid molecules and carry
them to the mRNA molecule.
Complimentary anticodon - codon bases align and are held by together by the
ribosome at an attachment site; a codon-anticodon complex is formed.
Peptide bonds are formed between adjacent amino acids by condensation
reaction.

Question 27

If anticodon = CCC ?

Answer 27

amino acid glycine will attach to the other end of the tRNA molecule
CCC anticodon will combine with a GGG codon on the mRNA molecule
mRNA codon GGG translates into the amino acid glycine

Question 28

initiaion?

Answer 28

ribosome attaches to a start codon at 1 end of the mRNA molecule

Question 29

Elongation?

Answer 29

2 amino acids = close enough together for a peptide bond to form between them ; a new amino acid = added to polypeptide chain

Question 30

Termination?

Answer 30

amino acids = added until ribosome reaches a stop codon. Ribosome detaches from the mRNA molecule and polypeptide = released.

Question 31

what does a start stop codon do?

Answer 31

tells the ribosome where to start and stop reading the genetic code.