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Block 1 > DNA, RNA And Proteins > Flashcards

DNA, RNA And Proteins Flashcards

1
Q

What is the role of macromolecules?

A

If organic (carbon-containing) they are crucial for most biological functions e.g. nucleic acids (DNA + RNA), proteins, carbohydrates + lipids

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2
Q

What is the function of nucleic acids such as DNA and RNA?

A

Information storage + transmission

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3
Q

What are the functions of proteins?

A 
Enzymatic catalysis
Antibodies
Hormonal signalling
Structural proteins
Contractile proteins
Gas transport
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4
Q

What is the function of carbohydrates?

A

Energy source

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5
Q

What are the functions of lipids?

A

Energy source
Membrane components
Hormonal signalling

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6
Q

Why are DNA, RNA and proteins special?

A

All molecules conform to physical + chemical laws but through their complex behaviour, nucleic acids + the proteins they encode display properties appearing to transcend those laws - ‘life’

E.G. proteins are cellular components with precise structures defined by sequence info - many are highly specific catalysts (enzymes) that allow the large no. of chemical reactions necessary for life to occur simultaneously in cells

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7
Q

What are Deoxyribose Nucleic Acid (DNA) and Ribose Nucleic Acid (RNA) made up of?

A

Polymers of nucleotides

Nucleotides consist of a sugar (deoxyribose/ribose), phosphate + a variable ‘base’ which forms the sequence - in DNA this encodes AA sequences of proteins + RNA involved in translating this DNA code

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8
Q

What are proteins made up of?

A

Polymers of 20 different kinds of AAs

AAs form a sequence that determines the protein shape + thus, its function

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9
Q

How are nucleotides structured within DNA?

A

The 4 bases pair via H-bonds according to simple rules where A pairs with T (U in RNA) + G pairs with C

Nucleotides connected to sugar-phosphate backbone

The 2 DNA strands run in opposite directions

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10
Q

The molecular properties of DNA allow it to perform its 2 great functions. What are they?

A
  1. To control information on what proteins to make

2. To pass that information on to daughter cells

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11
Q

What is the structure of DNA?

A

Bases stack in centre of helix forming an uncharged core with H-bond donors/acceptors (recognised by proteins/drugs in sequence-specific manner)

-vely charged sugar-phosphate backbones not equally spaced forming major + minor grooves (relevant to protein/drug binding too)

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12
Q

Explain the central dogma of molecular biology.

A

Info in DNA conserved with high fidelity by DNA REPLICATION

During gene expression, info is passed from DNA to mRNA in TRANSCRIPTION

Info passes from mRNA to protein via TRANSLATION (3 bases = 1AA)

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13
Q

How does semi-conservative DNA replication occur?

A

Each strand acts as a sequence template for DNA synthesis leading to 2 DNA helices

Replication passes on exact sequence of bases to both daughter DNA helices but only 1 strand (1/2 the original DNA helix) is passed onto new helix hence the term ‘semi-conservative’

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14
Q

What is the mechanism of DNA replication?

A

Hydrolysis of nucleoside triphosphates provides energy for incorporation of each new nucleotide into DNA polymer

DNA polymerase can only go 5’ to 3’ direction so goes directly in leading strand and in short stretches (Okazaki fragments) in the lagging strand

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15
Q

What is the mechanism of transcription?

A
  1. RNA polymerase separates DNA helix + binds to template strand at the promoter
  2. RNA polymerase moves along strand 5’ to 3’ producing complementary RNA nucleotides
  3. RNA polymerase terminates at stop codon + complementary mRNA strand has been produced
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16
Q

What is the mechanism of translation?

A
  1. mRNA strand binds to small ribosomal subunit which is joined at start codon by first tRNA carrying AA methionine which binds to codon via anticodon
  2. Small + large ribosomal subunits interlock around mRNA strand
  3. A 2nd tRNA arrives at adjacent binding site of ribosome binding to the next mRNA codon via its anticodon
  4. 1st AA detaches from tRNA + joined to 2nd AA by a peptide bond
  5. Ribosome moves 1 codon further along mRNA where 1st tRNA detaches as another arrives
  6. Chain elongates until stop codon is reached + components separate
17
Q

What is a ribosome?

A

A RNA enzyme/ribozyme made mostly of rRNA with its substrate being aminoacyl-tRNA + its template for protein synthesis (translation) being mRNA

18
Q

What type of reactions do proteins not catalyse?

A

Their own synthesis

19
Q

What is the structure of transfer RNA (tRNA)?

A

Complex cross-shaped structure formed by base-pairing between nucleotides

AA joined to RNA at 3’ end far from anticodon

20
Q

What enzyme loads the correct amino acid onto each tRNA?

A

Aminoacyl tRNA synthetase

21
Q

What is the structure of amino acids?

A

Amino + carboxyl group at opposing ends (both groups ionized at pH 7)

α-carbon atom

R side chain (20 different varieties)

22
Q

How are peptide bonds formed?

A

Condensation reaction where H2O is removed from 2 AAs to form a planar amide bond (CO=NH) which is chemically very stable

23
Q

What are the different types of amino acids? Give examples of each.

A
  • Small: Gly, Ala
  • Nucleophilic: Ser, Thr, Cys
  • Hydrophobic: Val, Leu, Ile, Met, Pro
  • Aromatic: Phe, Tyr, Trp
  • Acidic: Asp, Glu
  • Amide: Asn, Gln
  • Basic: His, Lys, Arg
24
Q

What are the 3 types of intramolecular forces?

A
  1. Electrostatic attractions
  2. Hydrogen (H) bonds
  3. Van der Waals/hydrophobic attractions
25
Q

How are amino acids arranged in an α-helix?

A

Right-handed helical structure where each AA gives 100o turn in helix

NH group from 1 AA forms a H-bond with the CO group of the AA 4 residues earlier

26
Q

How are ß-sheets formed?

A

ß-strands formed by AAs in an extended conformation -> H-bonds between adjacent ß-strands formed ß-sheets

27
Q

What are the 2 types of ß-sheet?

A

Parallel: strands run in same direction

Antiparallel: strands run in opposite direction

28
Q

What is a protein motif?

A

Super 2ndary structure where a set of 2ndary structure elements are found together in different proteins

Often have same function in different proteins e.g. DNA binding (not always the case)

29
Q

What is a protein domain?

A

Structure within a protein that can fold + function independently of the rest of the polypeptide chain

Often found in multiple proteins + many proteins contain multiple domains

30
Q

What are the levels of protein structure?

A
  1. Primary: AA sequence of polypeptide
  2. Secondary: arrangement of α-helices, ß-strands + loop regions
  3. Tertiary: overall shape when AA side chains included
  4. Quaternary: multiple polypeptide chains + non-polypeptide elements
31
Q

Give a good example of a quaternary structure.

A

Haemoglobin (Hb) as it has 4 near-identical polypeptide chains + 4 haem groups

32
Q

What is myoglobin similar to?

A

A single polypeptide chain of Hb with 1 haem

Block 1 (54 decks)

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