Nucleic Acids

Question 1

What is a monomer?

Answer 1

Molecule that when repeated makes up a polymer

Question 2

What is a nucleotide?

Answer 2

Molecule consisting of a five-carbon sugar, a phosphate group and a nitrogenous base

Question 3

What is a polynucleotide?

Answer 3

Large molecule containing many nucleotides

Question 4

What are Nucleotides? (Detailed)

Answer 4

Phosphate esters of pentose sugar, where a nitrogenous base is linked to the c1 (carbon 1 atom) of the sugar residue, and a phosphate group linked to either the c5 or c3 of the sugar residue, by covalent bonds formed by condensation reaction

Question 5

What is a double helix?

Answer 5

Shape of DNA molecule, due to coiling of the two sugar-phosphate backbone strands into a right-handed spiral configuration

Question 6

What is the monomer of nucleic acids?

Answer 6

Nucleotides

Question 7

What is the polymer formed by joining nucleotides?

Answer 7

Nucleic acids (DNA and RNA)

Question 8

Name of RNA and DNAs pentose sugar?

Answer 8

RNA-ribose

DNA-deoxyribose

Question 9

When do nucleotides become phosphorylated nucleotides?

Answer 9

What they contain more than one phosphate group. Example- ADP (adenosine diphosphate)

Question 10

What is ATP?

Answer 10

A phosphorylated nucleotide. It is an energy-rich end-product of most energy releasing biochemical pathways, and is used to drive most energy requiring metabolic processes in cells

Question 11

What can nucleotides help regulate?

Answer 11

Many metabolic pathways

Question 12

What may nucleotides be components of?

Answer 12

Coenzymes

Question 13

Difference between nucleotide and nucleoside?

Answer 13

Nucleotide- nitrogenous base, pentose sugar, phosphate group

Nucleoside- nitrogenous base, pentose sugar

Adenosine is a nucleoside

Question 14

Where is DNA usually found?

Answer 14

Nuclei of all eukaryotic cells, within cytoplasm of prokaryotic cells and also inside some viruses

Question 15

Structure of DNA

Answer 15

Polymer as it is made up of repeating monomeric units called nucleotides
Consists of 2 polynucleotide strands
Two strands run in opposite direction (antiparallel)
Each nucleotide consists of phosphate group, deoxyribose and one of 4 nitrogenous bases
Covalent bond between sugar residue and the phosphate group in nucleotide is also called phosphodiester bond
Long so they can carry a lot of encoded genetic information

Question 16

What bases in DNA are purine and which are pyrimidine?

Answer 16

Purine - adenine or guanine (two rings)

Pyrimidine - thymine or cytosine (one ring)

Question 17

How are the 2 antiparallel DNA strands joined?

Answer 17

Hydrogen bonding
A-T with 2 hydrogen bonds
G-C with 3 hydrogen bonds
Purine always pairs to pyrimidine, giving equal sized rungs on the DNA ladder
Can then twist into the double helix to give it stability

Question 18

What do hydrogen bonds allow?

Answer 18

Allow the molecule to unzip during transcription and replication

Question 19

Describe how DNA is antiparallel?

Answer 19

The two strands of DNA run in opposite directions. One strand starts with 5’ and ends in 3’ and the other starts with 3’ and ends in 5’

Question 20

Why does DNA need to be very stable?

Answer 20

So the coded information within the base sequence is protected

Question 21

How is DNA organised in Eukaryotic cells?

Answer 21

Majority of DNA content is in nucleus
DNA is wound around his tone proteins
Each chromosome is one DNA molecule
Also a loop of DNA in mitochondria and chloroplasts

Question 22

How is DNA organised in prokaryotic cells?

Answer 22

In a loop in the cytoplasm, not in a nucleus
Not wound around his tone proteins
Naked

Question 23

What is DNA polymerase?

Answer 23

Enzyme that catalyses the formation of DNA from activated deoxyribose nucleotides, using single stranded DNA as a template

Question 24

What is helicase?

Answer 24

Enzyme that catalyses the breaking of hydrogen bonds between the nitrogenous base pairs of bases in the DNA molecule

Question 25

What's semi conservative replication?

Answer 25

How DNA replicates, resulting in two new molecules, each of which contains one old strand and one new strand. One old strand is conserved in each new molecule

Question 26

Why does a DNA need to be copied? And when is it replicated?

Answer 26

So each new daughter cell relieves a full set of instructions. The replication takes place during interphase

Question 27

To make a new copy of itself, each DNA molecule...

Answer 27

- unwinds-double helix is untwisted, catalysed by a gyrase enzyme - unzips-hydrogen bonds between the nucleotide bases are broken. Catalyses by DNA helicase and results in 2 single strands of DNA with exposed nucleotide bases

Question 28

What happens after unzipping?

Answer 28

Free phosphorylated nucleotides bond to complementary exposed bases. DNA polymerase catalyses addition of new nucleotides in the 5' to 3' direction. Leading strand is synthesised continuously whereas lagging strand is in fragments that are later joined by ligament enzymes Hydrolysis of activated nucleotides supplies energy to make phosphodiester bonds between sugar residue and one nucleotide and the phosphate group of the next molecule

Question 29

How loops of DNA undergo semi conservative replication?

Answer 29

A bubble sprouts from the loop and this unwinds and unzips and then complementary nucleotides join to the exposed nucleotides. Eventually the whole loop is copied

Question 30

How could mutations occur in DNA replication?

Answer 30

The wrong nucleotide may be inserted | This could change the genetic code

Question 31

How are mutations limited?

Answer 31

Enzymes that proofread and edit out such incorrect nucleotides, reducing the rate that mutations are produced

Question 32

What do you call different versions of the same gene?

Answer 32

Alleles

Question 33

What's a gene?

Answer 33

A length of DNA that codes for a polypeptide or a length of RNA that is involved in the regulation gene expression

Question 34

What's a polypeptide?

Answer 34

A polymer made up of many amino acid units joined together by peptide bonds.

Question 35

What is a protein?

Answer 35

A large polypeptide of 100 or more amino acids

Question 36

What's transcription?

Answer 36

The process of making messenger RNA from a DNA template

Question 37

What's translation?

Answer 37

Formation of a protein, at ribosomes, by assembling amino acids into a particular sequence according to the coded instructions carried from DNA to ribosome by mRNA

Question 38

How is RNA different to DNA?

Answer 38

``` The 5 carbon sugar is ribose Uracil replaces thymine Single stranded Shorter 3 forms of RNA (messenger RNA. Transfer RNA and ribosomal RNA) ```

Question 39

What decides a proteins 3D shape?

Answer 39

It's primary polypeptide chain

Question 40

Why is the genetic code described as Universal Degenerate Non-overlapping

Answer 40

1) in almost all living organisms and same triplet of DNA bases codes for the same amino acid 2) almost all amino acids have more than one base triplet 3) it is read starting from a fixed point in groups of 3 bases

Question 41

Describe transcription

Answer 41

Gene unwinds and unzips Hydrogen bonds between complementary nucleotides bases break Enzyme RNA polymerase catalyses the formation of temporary hydrogen bonds between RNA nucleotides and their complementary unpaired DNA bases. U replaces T Length of RNA is complementary to template DNA strand therefore called the coding strand mRNA passes out of nucleus, through nuclear envelope and attaches to ribosome

Question 42

Describe translation

Answer 42

tRNA molecules bring amino acids and find their place where the anticodon binds by temporary hydrogen bonds to complementary codon on mRNA molecule. Ribosomes moves along length of mRNA. Reads each code. Two amino acids adjacent to each other form peptide bond between each other ATP is needed for polypeptide synthesis Amino acid sequence is ultimately determined by gene After polypeptide assembled. mRNA breaks down and can be recycled New polypeptide is folded correctly into its 3D shape to carry out its function. It's aided by chaperone proteins