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BIOCHEM LEC > TRANSLATION > Flashcards

TRANSLATION Flashcards

1
Q

the process of protein synthesis

A

translation

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2
Q
  • Synthesis of proteins in ribosomes
  • Uses mRNA as a template; and
  • tRNA as an adapter molecule carries the amino acids to the growing polypeptide chain
A

translation

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3
Q

TRANSLATION

uses ____ as template

A

mRNA

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4
Q

TRANSLATION

requires a ____

A

genetic code

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5
Q

TRANSLATION

Used to identify the specific amino acid sequence

A

genetic code

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6
Q

TRANSLATION

Any ____ in the nucleotide sequence may result in an incorrect amino acid being inserted into the protein -> disease or even death

A

alteration

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7
Q

The genetic code is a “____” that identifies the correspondence between a sequence of nucleotide bases and a sequence of amino acids.

A

dictionary

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8
Q

Each individual “word” in the code is composed of three nucleotide bases called

A

codons

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9
Q

STOP CODONS

A

UAG
UGA
UAA

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10
Q

There are a total of ____ codons

A

64

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11
Q

____ codons code for amino acids

A

61

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12
Q

____ stop codons that terminate translation

A

3

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13
Q

Start or initiating codon

A

AUG

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14
Q

Start or initiating codon (AUG) for EUKARYOTES

A

METHIONINE

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15
Q

Start or initiating codon (AUG) for PROKARYOTES

A

N-formylmethionine

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16
Q

CHARACTERISTICS OF THE GENETIC CODE

Multiple codons may code for the same amino acid

A

degenerate

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17
Q

CHARACTERISTICS OF THE GENETIC CODE

A specific codon always codes for the same amino acid

A

unambiguous

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18
Q

CHARACTERISTICS OF THE GENETIC CODE

The codons are read in a continuing sequence of nucleotide triplets until a translation codon is reached

A

nonoverlapping

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19
Q

CHARACTERISTICS OF THE GENETIC CODE

It has been conserved from very early stages of evolution with only slight differences in the manner in which the code is translated

A

universal

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20
Q

COMPONENTS REQUIRED FOR TRANSLATION

All the ____ that eventually appear in the finished protein must be present at the time of protein synthesis. If one ____ is missing, translation stops at the codon specifying that ____

A

AMINO ACID

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21
Q

COMPONENTS REQUIRED FOR TRANSLATION

at least 50 tRNA species

A

HUMANS

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22
Q

COMPONENTS REQUIRED FOR TRANSLATION

at least 30 tRNA species

A

BACTERIA

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23
Q

COMPONENTS REQUIRED FOR TRANSLATION

The carboxyl group of the amino acid is in an ____ with the 3′-hydroxyl of the ribose portion of the A nucleotide in the –CCA sequence at the 3′-end of the tRNA.

A

ESTER LINKAGE

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24
Q
  • a 3-base nucleotide sequence which pairs with a specific codon on the mRNA
  • This codon specifies the insertion into the growing polypeptide chain of the amino acid carried by that tRNA.
A

ANTICODON

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25
* **Required** for the **attachment** of **amino acids** to their **corresponding tRNA** * **Covalent attachment** of the **alpha-carboxyl group** of an **amino acid** to the **A** in the **–CCA sequence** at the **3’ end** of its **corresponding tRNA**
aminoacyl-tRNA sequence
26
are **large complexes of protein** and ribosomal RNA (rRNA), in which rRNA predominates
ribosomes
27
# **RIBOSOMES** prokaryotes
50S & 30S
28
# **RIBOSOMES** eukaryotes
60S and 40S
29
S means
svedberg
30
determines the **accuracy** of **translation** by insuring **correct base-pairing** between the **mRNA codon** and the **tRNA anticodon**
small ribosomal subunit
31
catalyzes **formation of the peptide bonds** that **link** **amino acid residues** in a protein
large ribosomal unit
32
* **binds** an **incoming** aminoacyl-tRNA as directed by the codon currently occupying this site. * This codon specifies the **next amino acid** to be **added** to the growing peptide chain.
A site
33
**occupied** by **peptidyl-tRNA** (tRNA that **carries** the **chain of amino acids** that **has already been synthesized**)
P site
34
**occupied** by the **empty tRNA** as it is about to **exit the ribosome**
E site
35
# **Codon Recognition by the tRNA** follows the rules of ____ and ____ binding, that is, the mRNA codon is read **5′→3′** by an **anticodon** pairing in the **opposite (3′→5′) orientation**
complementary and antiparallel binding
36
STEPS IN **TRANSLATION**
initiation elongation termination
37
* **Assembly** of the components of translation * **Two** ribosomal subunits * **mRNA** * Before initiation, aminoacyl-tRNA synthetases attach amino acids to their respective tRNAs (charging) * Requires **hydrolysis** of **ATP -> AMP** * **Proofreading** is **possible** to **remove incorrect** amino acids * **Initiation factors** (IF-1, IF-2, IF-3, eIF) * **GTP** (and **ATP** for **eukaryotes**)
initiation
38
# **INITIATION** In **eukaryotes**, the ____ **binds close to the cap** structure at the **5’-end of the mRNA** and **moves 5’ - 3’** along the mRNA **until it encounters the initiation codon** (AUG).
small (40s) ribosomal unit
39
# **INITIATION** Initiation codon is **recognized** by a
special initiator tRNA
40
# **INITIATION** In **both** **prokaryotic** and **eukaryotic** cells, this **N-terminal Met** is usually ____ **before translation is completed**
removed
41
* A **cyclic process** on the ribosome in which **one amino acid at a time is added** to the growing peptide chain * Requires **elongation factors** * Steps: 1. Binding of aminoacyl tRNA to the A site 2. Peptide bond formation catalyzed by peptidyl transferase 3. Translocation of the ribosome on the mRNA 4. Expulsion of the deacylated tRNA from the P- and E-sites
ELONGATION
42
* Occurs when **one of the three termination codons moves into the A site** * Results in the **release of the newly synthesized protein** and **dissociation of the ribosomes and mRNA**
termination
43
* In **most cases**, **accurate base pairing** is **required** only in the **first two nucleotide positions** of an mRNA codon * Allows a **single tRNA** to **recognize more than one** codon
tRNA wobble hypothesis
44
**Addition** of a **single amino acid** to the polypeptide chain **requires cleavage** of **four high-energy bonds** from ATP and GTP: * tRNA aminoacylation: **ATP -> AMP** * Loading tRNA onto ribosome: **GTP -> GDP** * Translocation: **GTP -> GDP**
energy requirement
45
tRNA aminoacylation
ATP -> AMP
46
Loading tRNA onto ribosome
GTP -> GDP
47
Translocation
GTP -> GDP
48
**Post-translational Modifications**
**Removal** of **excess** amino acids **Phosphorylation** **Glycosylation** **Hydroxylation** **Proteins** that are **defective** or destined for rapid turnover are **marked for destruction** by **ubiquitin** and degraded by proteasomes
49
**Proteins** that are **defective** or destined for rapid turnover are **marked for destruction** by ____ and degraded by proteasomes
ubiquitin
50
* Amanita **phalloides** (**death cap**) * **Alpha-amanitin** -> **inhibits** RNA polymerase II * Presents with **GI** symptoms, **acute liver failure**, and may be **fatal**
amanita mushroom poisoning
51
# **AMANITA MUSHROOM POISONING** inhibits RNA pol II
alpha-amanitin
52
# **AMANITA MUSHROOM POISONING** also known as **death cap**
amanita phalloides
53
* **Exotoxin** of **Corynebacterium diphtheriae** * **Inactivates** the eukaryotic elongation factor **EF-2**, **preventing translocation** * Results in **local tissue destruction** and **pseudomembrane formation**
diphtheria toxin
54
**binds** to the **BETA subunit** of **prokaryotic RNA pol** (selectively toxic) -> **prevents chain growth** beyond 3 nucleotides **Antitubercular** drug
rifampicin
55
* **Antineoplastic** * **Intercalates** between the DNA bases and **inhibits** **transcription initiation** and **elongation**
dactinomycin (actinomycin D|)
56
**Bind** to **30s subunit** and **interferes** with **initiation**
streptomycin aminoglycosides
57
**Prevents binding** of **aminoacyl-tRNA to the A site**
tetracycline
58
**Inhibits** prokaryotic peptidyltransferase
chloramphenicol
59
**Bind** to the **50S** and **inhibits translocation**
clindamycin macrolides
60
* Any **permanent heritable change** in the DNA base sequence of an organism * Has the **potential to change the base sequence of mRNA** and the amino acid sequence of proteins
mutation
61
# **POINT MUTATION** **purine**-**purine** or **pyrimidine**-**pyrimidine**
TRANSITION
62
# **POINT MUTATION** **purine**-**pyrimidine** or **pyrimidine**-**purine**
TRANSVERSION
63
# **POINT MUTATION** * **New** codon codes for **same** amino acid * **No effect** on protein
SILENT MUTATION
64
# **POINT MUTATION** * **New** codon codes for **different** amino acid * **Variable effects** on protein
MISSENSE MUTATION
65
# **POINT MUTATION** * **New** codon is a **stop** codon * **Shorter** than normal, usually **non-functional** protein
NONSENSE MUTATION
66
* **Deletion** or **addition** of **bases** that should **not be multiples of three** * **Shorter** than normal, usually **non-functional** protein
FRAME SHIFT MUTATION
67
* **Loss of large areas** of chromosomes during **unequal cross over** in meiosis * **Loss of function** * Protein **shorter** than normal or **entirely missing**
LARGE SEGMENT DELETION
68
* Splice site is **lost** * Variable effects ranging from **addition** or **deletion** of a **few amino acids** to **deletion** of an **entire exon** * Examples: - **Tay-Sachs**, **Gaucher**, **Beta-thalassemia**
SPLICE DONOR OR ACCEPTOR
69
* **Expansions** in **coding regions** cause protein product to be **longer** than normal and **unstable** * Diseases often show **anticipation** in **pedigree** * Examples: * **Huntington Disease** * **Fragile X Syndrome** * **Myotonic Dystrophy**
THIRD REPEAT EXPANSION

BIOCHEM LEC (33 decks)

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