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Bio 12 (1st half) > Protein Synthesis > Flashcards

Protein Synthesis Flashcards

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1
Q

What is Protein Synthesis?

A

the process of making new proteins

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2
Q

Where are the instructions for synthesizing proteins found?

A

in DNA

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3
Q

What are Genes?

A

sequences of DNA that code for protein

protein synthesis is how genes are expressed

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4
Q

What are the two stages of Protein Synthesis?

A

Transcription and Translation

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5
Q

Describe Transcription

A

the first stage of protein synthesis

the DNA template carrying the protein code is “transcribed” into mRNA (messenger RNA)

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6
Q

What does the enzyme RNA Polymerase do?

A

RNA Polymerase attaches to the Promoter and begins breaking apart hydrogen bonds at the promoter site

similar to helicase in DNA Replication

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7
Q

What is a Promoter?

A

the beginning region of the gene that allows for protein attachment

like a airport landing pad for RNA Polymerase

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8
Q

Describe the TATA Box

A

the TATA Box is a promoter sequence that is very common (found in 25% of human genes)

( 5’ - TATAAA - 3’ )

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9
Q

What bond to the complimentary base on the DNA template?

A

Free RNA nucleotides hydrogen bond to the complimentary base on the DNA Template

RNA does not contain Thymine

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10
Q

What base is used in RNA, that replaces Thymine?

A

Uracil

it’s identical to thymine but has an extra methyl group on its base
(still a pyrimidine)

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11
Q

How does RNA join the RNA Nucleotides together?

A

by forming the sugar-phosphate backbone

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12
Q

Describe the 5’ Cap

A

a 5’ cap is added to the first RNA nucleotide prevent degradation

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13
Q

Describe the Poly (A) Tail

A

a long strand of adenosine nucleotides

the tail protects the RNA from being degraded at the 3’ ends
(similar to telomeres)

also allows for transport across the nuclear envelope (security pass)

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14
Q

What is Polyadenylation?

A

the process of adding a poly (a) tail

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15
Q

What happens after the RNA strand is formed?

A

helicase breaks the RNA-DNA hydrogen bonds,

this frees the RNA strand from the nucleus

this RNA strand is called mRNA

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16
Q

Why is mRNA called mRNA?

A

it is a messenger that transports the protein instructions from the nucleus to the cytoplasm (where protein is made)

O ———————————————AAA
5’ Cap mRNA poly (a)
tail

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17
Q

What happens to mRNA before leaving the nucleus?

A

it undergoes RNA Splicing

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18
Q

What are Introns

A

sequences of RNA that don’t get converted into protein

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19
Q

What are Exons?

A

RNA sequences that code for proteins

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20
Q

What is RNA Splicing?

A

The process of removing Introns, leaving behind the Exons

Exons are then spliced (glued) together to form the final translated form of the mRNA Strand

O————————— AAA + Introns
Exons

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21
Q

Where does RNA Splicing take place?

A

at the Spliceosomes

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22
Q

What are Spliceosomes?

A

molecules containing a combination of RNA and Proteins, (similar to ribosomes)

located within the nucleus

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23
Q

Describe Translation

A

the second and final stage of protein synthesis

where the mRNA code is used to make new proteins

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24
Q

What organelle is responsible for performing Translation?

A

the Ribosomes

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25
Q

Where does Translation Occur?

A

anywhere ribosomes are found

in the cytoplasm

or

along the Rough ER

26
Q

What is the ratio that the Ribosomes are composed of?

A

one third protein

two thirds rRNA (ribosomal RNA)

27
Q

Where is rRNA synthesized?

A

in the nucleolus

rRNA is assembled into ribosomes in the cytoplasm

28
Q

What are the two subunits that Eukaryotic Ribosomes contain?

A

40S subunit (small)

60S subunit (large)

29
Q

What is the 40S subunit responsible for?

A

attaching and reading the mRNA

30
Q

What is the 60S subunit responsible for?

A

recruiting tRNA and amino acids

31
Q

How does mRNA enter the ribosome?

A

through the 40S, 5’ end first

32
Q

How do ribosomes read mRNA?

A

three nucleotides at a time

(codon)

33
Q

What is a Codon?

A

a three letter sequence of mRNA

34
Q

Describe the Start Codon

A

translation doesn’t occur until the ribosome reaches the start codon

the start codon is always AUG, which codes for Methionine

35
Q

What is 5’ Untranslated Region?

A

everything before the start codon
(5’ UTR)

36
Q

When does translation stop?

A

translation stops when the ribosome reaches a Stop Codon
(UGA, UAA, or UGA)

37
Q

What is the 3’ Untranslated Region?

(3’ UTR)

A

everything in between the stop codon and the Poly(A) Tail

38
Q

What is the coding region?

A

the region between the 5’ UTR and the 3’ UTR, containing all Exons

using the coding region, the 60S recruits tRNA (transfer RNA)

39
Q

What does tRNA contain?

A

Anti-Codons at one end, and a the matching Amino Acid at the other

40
Q

What are Anti-Codons

A

a three nucleotide sequence that complements the mRNA codon

A + U and G + C

41
Q

Describe how Codons correspond with amino acids

A

Each codon (except stop codons) correspond with a single amino acid

some amino acids can be coded for by multiple codons

42
Q

Where do the tRNA transfer the amino acids?

A

once in the ribosome, the tRNA transfer the amino acid to the growing polypeptide

polypeptide: a group of amino acids

43
Q

How are proteins synthesized?

(direction)

A

Proteins are synthesized from the
N-Terminus (amino end) to the
C-Terminus (carboxyl end)

44
Q

What happens once the stop codon has been reached?

A

the ribosome detaches and the new protein is released in the cytoplasm

45
Q

How many Amino Acids are used by humans and how do they differ?

A

there are 20 amino acids used by humans

they differ in their R-Group (side chain)

46
Q

What does the Amino Acid Composition affect in a protein?

A

A proteins :

shape,
hydrophobicity
charge,
solubility
enzymatic abilities

47
Q

What is Methionine?

A

the first amino acid in every protein

always first because it is coded for by the AUG start codon

48
Q

What is so special about Proline?

A

it causes the N-C-C backbone to kink

49
Q

Describe the Essential Amino Acids

A

there are 8 essential amino acids that can’t be synthesized by the body

they have to be acquired by protein in our diet

non-essential amino acids can be produced in the body

50
Q

What are the three ways Mutations can be classified as to whether they :

A

help the organism - advantageous

harm the organism- deleterious

have no effect - silent /neutral

51
Q

Mutations can also be classified by whether a nucleotide is :

A

added - insertion

removed - deletion

changed - substitution

52
Q

Describe Missense Mutations

A

substitution mutations where the change in the nucleotides alter one of the amino acids in a protein

53
Q

Describe Nonsense Mutations

A

substitution mutations where the new nucleotide causes an amino acid to be replaced by a stop codon

54
Q

Describe Frameshift Mutations

A

insertion or delete mutations that cause all subsequent amino acids to be altered

55
Q

How is gene expression controlled?

A

it is controlled by a result of genetics and the environment

as well as the genes themselves
(genetic code)

56
Q

What is Epigenetics?

A

the study of how gene expression is altered through factors other than the DNA Code

57
Q

What happens when Gene Expression is increased?

A

higher rate of protein synthesis

58
Q

What happens when Gene Expression is decreased?

A

lower rate of protein synthesis

59
Q

What is the most common way gene expression is decreased?

A

through Methylation

Methylation —> the process of adding a methyl group to DNA so that RNA polymerase can’t easily attach

60
Q

Explain what Epigenetics explains

A

that all cells in an individual contain identical DNA,

epigenetics is what makes each cell type distinct from the other

Bio 12 (1st half) (5 decks)

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