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MCAT- jules 2020 > B/B biomolecules > Flashcards

B/B biomolecules Flashcards

1
Q
  • functional RNA
  • not translated
A

non-coding RNA

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2
Q

the study of heritable changes in DNA activity that are not caused by changes in DNA sequence

  • main mechanisms: DNA methylation and histone modification
A

Epigenetics

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3
Q

all ____ amino acids are optically _____

A

chiral, active

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4
Q

what type of amino acids are found in proteins?

A

L-aminio acids

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5
Q

nonpolar amino acids. categories include AAs with alkyl or aromatic R groups

A

Hydrophobic

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6
Q

polar amino acids. categories include neutral, basic, and acidic R groups

A

hydroPHILIC amino acids

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7
Q

What are the hydrophobic/nonpolar alkyl amino acids?

A
  1. G - glycine
  2. A - alanine
  3. V -valine
  4. L - leucine
  5. I - isoleucine
  6. M - methionine
  7. P - proline
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8
Q

what are the hydrophobic/nonpolar aromatic AAs?

A
  1. W - Tryptophan
  2. F - Phenylalanine
  3. Y - Tyrosine

aromatic groups can absorb UV light. The more protein the more UV stored.

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9
Q

what are the hydrophilic neutral AAs?

A
  1. S - Serine
  2. T - Threonine
  3. N - Asparagine
  4. Q - Glutamine
  5. C - Cysteine

every AA in this group has an OH or SH in the side chain and are able to form hydrogen bonds

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10
Q

what are the hydrophilic basic AAs?

A
  1. R - Argenine
  2. K - Lysine
  3. H - histidine

All have a Nitrogen in the side chain

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11
Q

what are the hydrophilic acidic (negatively charged) AAs?

A

Aspartate/Aspartic acid (D)

Glutamate/Glutamic Acid (E)

both have a second carboxyl (-COOH) group in the side chain

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12
Q

what is pI?

A

isoelectric point

  • the point along the pH scale where the amino acid has a net charge of 0 (zero)
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13
Q

what type of bonds join amino acids together?

A

Peptide bonds (which are essentially amide bonds)

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14
Q

how can a peptide bond be cleaved by hydrolysis?

A

via a strong acid or proteolysis (protease cuts a specific bond)

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15
Q

What bonds are present in primary protein structure?

A

Since the primary structure is just the sequence of amino acids, covalent bonds link amino acids together. The types of covalent bonds used are peptide and disulfide bonds.

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16
Q

How is the secondary structure of a protein formed?

A
  • 2’ structure is formed due to the attractive and repulsive forces of interactions between main chains of neighboring amino acids. This forms recurring structural patterns.
  • 2’ structure depends primarily on H bonds
  • structural pattern examples: a helix and b-sheet.
  • B-sheet occurs with H bonding between neighboring chains rather than within the same polypeptide (like a-helix).
  • parallel B sheet = H bonded strands run in same direction forming bent/weaker H bonds
  • antiparallel B-sheets = H bonded strands that run in opposite directions forming linear/stronger H bonds
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17
Q

what type of bonds are depended upon by 3’ and 4’ protein structure?

A
  • peptide bonds of AA sequence & H-bonds of 2’ structure
  • Ionic and hydrophobic interactions and disulfide bonds ***
18
Q

explain the special properties of Histidine (H)

A
  • found in both protonated and unprotonated forms in the body
  • useful around the sites of enzymes to stabilize or destabilize a reaction
19
Q

explain the special properties of glycine (G)

A
  • NOT chiral
  • NOT optically active
  • very small and flexible
  • acts as a helix breaker bc the small R group supports other confirmations
20
Q

explain the special properties of Cysteine

A
  • forms a reversible disulfide bond upon oxidation and becomes cysTINE
  • CystEine is ~oxidized~ (LEO) to become cysTINE (TINEy –> loss of electrons makes it smaller) -S-S-
21
Q

what is an opetator?

A
  • a SEQUENCE of DNA
  • bound by a transcription factor protein
22
Q

what is a promotor?

A
  • a SEQUENCE of DNA
  • bound by a RNA polymerase
23
Q

what are general transcription factos (GTFs)

A
  • class of proteins that bind to specific DNA sites to ~activate~ transcription
24
Q

what are activators?

A

a type of DNA binding PROTEIN that enhances the interaction between RNA polymerase and a [articular promoter by encouraging transcription

25
Q

what is an enhancer?

A
  • a DNA SITE bound by activators in order to loop the DNA to bring a specific promoter to the initiation complex
  • cis-acting : act on the same chromosome as they are located
  • don’t act on promoter regions themselves
26
Q

what is a repressor?

A
  • PROTEIN that binds to the operator that stops RNA pol. movement and stop transcription/gene expression
  • if inducer is present, can react with repressor to make it detach from operator and let gene be transcribed
27
Q

what is a silencer?

A
  • region of DNA bound by repressor proteins to silence gene expression
28
Q

what must happen during Post-Transcriptional Regulation?

A
  • pre-mRNA is modified before it leaves the nucleus
  • only EXONS are present in finished mRNA
  • introns are spliced out since they are non-coding RNA segments via a spliceosome
  • 5’ cap that protects mRNA from exonucleases, promotes ribosome binding, and regulated nuclear export of mRNA
  • poly A tail on 3’ end to help with transcription termination
29
Q

What is non-coding RNA (ncRNA)?

A
  • a functional RNA molecule that is not translated into protein.
  • has vital functions in the cell as RNA (many participate in transcription/translation)
30
Q

what is Ribosomal RNA (rRNA)?

A
  • help make up the ribosome, used in translation
31
Q

what is MicroRNA (miRNA)

A
  • functions in transcriptional and post-transcriptional regulation of gene expression by base pairing with complementary sequences within mRNA molecules
32
Q

what are transfer RNAs (tRNAs)

A
  • link codons in mRNA strand with corresponding amino acids for polypeptides
33
Q

what are small nucleolar RNAs (snoRNAs)?

A
  • small RNA molecules that guide covalent modifications of rRNA, tRNA, and snRNA through methylation or pseudouridylation
34
Q

what are small nuclear RNAs (snRNAs)?

A
  • main function: processing of the pre-mRNA in the nucleus
  • also aid in regulation of transcription factors or RNA polymerase II and maintaining telomeres
35
Q

Oncogenes

A
  • proto-oncogenes code for proteinst aht normally detect cell growth & differentiation then something happens to make them oncogenes via:
    1. deletion or point mutation 2. gene amplification/increased mRNA stability 3. chromosomal rearrangement
36
Q

What are tumor supressors?

A

genes whose protein products either have a halting effect on the regulation of the cell cycle or can promote apoptosis

  • act as big stop signs/safety checks to stop mistakes in cell division
  • Two types: DNA repair proteins and Cell Cycle Repressor proteins

ex of tumor supressor: p53 protein (holds cell hostage between G1–>S)

37
Q

What is a point mutation?

A

when one DNA base is replaced with another which leads to a change in one RNA nucleotide and sometimes a change in an amino acid

38
Q

what is a frameshift mutation?

A
  • when a DNA base is added to or removed from the gene sequence. Shifts the translational reading frame
  • have the most significant effect on the final protein
39
Q

what is a nonsense mutation? a missense mutation?

A

nonsense: when the mutation leads to the RNA sequence codon being a STOP codon
missense: changes one amino acid to another. can either be consercative (AA is same type as original) or non-conservative

40
Q

What is the difference between a transition point mutation and a transversion point mutation?

A

transition: substituting purine for purine or pyrimidine for pyrimidine (ex: A–> G or C—> T)
transversion: switiching a purine for a pyrimidine or vice versa

41
Q
A

MCAT- jules 2020 (6 decks)

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