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Biology Unit 3 AOS 1 - What is the role of nucleic acids and proteins in maintaining life? > Chapter 1 - The relationship with nucleic acids and proteins > Flashcards

Chapter 1 - The relationship with nucleic acids and proteins Flashcards

1
Q

What are nucleic acids?

A

Large biomolecules that store and transmit genetic information required for protein synthesis.

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2
Q

What is deoxyribonucleic acid (DNA)?

A

A nucleic acid that carries instructions for production of RNA and proteins.

Contains a deoxyribose sugar (with one less oxygen compared to ribose in RNA)

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3
Q

What is ribonucleic acid (RNA)?

A

A nucleic acid that plays a major role in protein synthesis.

Contains a ribose sugar.

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4
Q

What are the 3 main types of RNA and their functions?

A
  1. mRNA (messenger RNA) - carries a copy of the genetic code/information from DNA to the ribosome
  2. tRNA (transfer RNA) - delivers amino acids from the cell’s cytoplasm to the ribosome, pairing with the complementary code carried by the mRNA
  3. rRNA (ribosomal RNA) - forms ribosomes, where protein synthesis occurs
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5
Q

What are nucleotides?

A

Monomers that make up nucleic acids

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6
Q

What are the components of a nucleotide?

A
  1. Phosphate group
  2. Pentose sugar (deoxyribose in DNA, ribose in RNA)
  3. Nitrogenous base (Adenine (A), Guanine (G), Cytosine (C), and Thymine (T) in DNA, or Uracil (U) in RNA)
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7
Q

What are the two significant ends of a nucleotide?

A

1) 5’ end, which contains phosphate group attached to 5th carbon of the sugar

2) 3’ end, which contains hydroxyl (-OH) group linked to 3rd carbon in the sugar

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8
Q

Key bonds in nucleic acids

A

Phosphodiester bonds between adjacent nucleotides (creating phosphate-sugar backbone) and hydrogen bonds between complementary nitrogenous bases (which stabilise DNA structure).

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9
Q

How are nucleotide strands formed?

A

Through condensation polymerisation, nucleotides link via phosphodiester bonds, releasing water and forming-sugar phosphate backbone.

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10
Q

Key features of DNA

A
  • Double stranded helix
  • Anti-parallel strands
  • Hydrogen bonds between complementary base pairs
  • Ladder-like structure (made from sugar-phosphate backbone)
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11
Q

How many hydrogen bonds hold Adenine and Thymine base pairs together?

A

Two

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12
Q

How many hydrogen bonds hold Guanine and Cytosine together?

A

Three

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13
Q

What is the central dogma of molecular biology, and in which way does it flow?

A

Description of how genetic material flows within a cell:

DNA ⇄ RNA → Protein

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14
Q

What is the genetic code?

A

Information stored in DNA as a triplet code within sections called
genes.

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15
Q

What is a gene?

A

A section of DNA that codes for a protein or functional RNA molecule (such as tRNA)

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16
Q

What is upstream of a gene?

A

DNA region towards the 5’ of the coding strand of the gene

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17
Q

What is downstream of a gene

A

DNA region towards the 3’ end of the codon strand of a gene

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18
Q

What is a promoter region?

A

The promoter region is where RNA polymerase attaches to the gene to initiate transcription

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19
Q

What is RNA polymerase?

A

An enzyme that synthesises an RNA strand from a DNA template during transcription

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20
Q

What base sequence in the promoter region does RNA polymerase identify and bind to?

A

TATA AA base sequence.

Some promoter regions also contain CAAT box, which works together with TATAAA box for RNA polymerase to latch on.

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21
Q

Why is genetic code said to be unambiguous?

A

Each codon specifies for only one amino acid

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22
Q

Why is genetic code said to be degenerate?

A

Most amino acids can be coded for by more than one codon

23
Q

Why is genetic code said to be
universal?

A

The same codons code for the same amino acids in all living organisms

24
Q

What is the start codon for translation?

25
What are the stop codons for translation?
UAA, UAG, UGA
26
What is the template strand?
The strand of DNA used to produce a complementary mRNA strand during transcription
27
What is the coding strand?
The strand of DNA that is complementary to the template strand (Almost identical to mRNA strand, but Thymine bases in DNA are swapped to Uracil bases in mRNA)
28
What are exons?
DNA regions that are coding segments
29
What are introns (also known as spacer DNA)?
DNA regions that are non-coding segments, and are spliced out of mRNA during RNA processing
30
What is gene expression?
The process by which information in a gene is used to synthesise a protein
31
What is transcription
Production of single-stranded mRNA from DNA.
32
Where does transcription occur in eukaryotic cells?
The nucleus.
33
What are the steps of transcription?
1. Initiation: RNA polymerase binds to the promoter and unwinds DNA, breaks hydrogen bonds. 2. Elongation: RNA polymerase synthesizes mRNA using complementary base pairing. 3. Termination: RNA polymerase reaches a stop signal and releases the mRNA.
34
What is the product of transcription?
Pre-MRNA
35
How many base pairs does RNA polymerase cover?
~30 at a time, and forms transcription bubble of ~15 uncoiled base pairs
36
What are the three processes in RNA processing (in order)
1. Addition of a 5' methyl (CH3) cap 2. Addition of a poly-A (up to 250 adenine bases) tail at 3' end 3. Splicing (removal) of introns by spliceosomes
37
Where does RNA processing occur
RNA processing is only in eukaryotes, occurs in nucleus.
38
What is translation?
The process of building a polypeptide chain from amino acids, guided by the sequence of mRNA codons, occurs in the cell cytoplasm
39
What structures are involved in translation?
mRNA: Carries the genetic code. tRNA: Brings amino acids to the ribosome. Ribosome: Provides the site for protein synthesis. Amino acids: Linked together to form a polypeptide.
40
How does gene expression differ in prokaryotes?
- No nucleus: transcription and translation occur simultaneously - No mRNA processing - Contain operator regions which regulate transcription by allowing repressor proteins to bind and prevent RNA polymerase from binding to promoter region
40
What are the steps of translation
Initiation: Ribosome assembles upstream of start codon (AUG). AUG signals the start of translation. Elongation: tRNA brings amino acids, which are joined by peptide bonds. The first amino acid added is methionine Termination: Ribosome reaches stop codon (UAA, UAG or UGA), and releases polypeptide.
41
What is a proteome?
The complete set of proteins in an organism.
42
What is a frame shift mutation?
Genetic mutation involving the insertion or deletion of one or more nucleotides, shifting the start of where codons are read/grouped into threes
43
What is a point mutation?
Genetic mutation where a single nucleotide is swapped for another
44
What are the 4 levels of protein structure?
1. Primary Structure 2. Secondary Structure 3. Tertiary Structure 4. Quaternary Structure
45
What is primary structure of a protein?
Sequence of amino acids in a polypeptide
46
What is secondary structure of a protein? List three examples.
Natural local bending and twisting of the polypeptide due to the interactions of adjacent amino acids in the polypeptide chain. Includes α-helix (alpha helix), β-pleated sheets, and random coiling
47
What is an α-helix (alpha helix) structure?
Right hand spiralling of polypeptide with side chains pointing outwards. Caused by repulsion of side chains. Held together tightly by hydrogen bonds.
48
What is a β-pleated (beta pleated) sheet structure?
A secondary structure where proteins appear as folded sheets in a zig zag pattern, due to alternating hydrophobic and hydrophilic side chains
49
What is tertiary structure of a protein? Give three examples.
1. Disulfate bonding- bridges form between two cystine amino acids 2. Weak ionic and hydrogen bonding 3. Hydrophobic reactions
50
What is quaternary structure in a protein?
For proteins that consist of more than a single polypeptide chain, quaternary structure describes the way multiple polypeptides join together to form a protein.
51
In which direction does RNA polymerase move across the DNA template?
3' to 5' direction.
52
Which end does RNA polymerase add nucleotides to mRNA?
3' end.
53
How is the structure of an operon different to eukaryotic genes?
Operons contain a common promoter and operator. Eukaryotic genes have no operon, but have a longer upstream region where regulation can occur instead.

Biology Unit 3 AOS 1 - What is the role of nucleic acids and proteins in maintaining life? (3 decks)

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