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PSIO303 Integrative Cellular Physiology > Block 1 - Making Parts (L6-7) > Flashcards

Block 1 - Making Parts (L6-7) Flashcards

1
Q

The nucleus has — that codes for —- proteins.

A

DNA, 30,000

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2
Q

How is DNA typically stored?

A

in a dispersed form called chromatin, where the nucleic acids are spooled around histone proteins

the chromatin supercoils into chromosomes during cell division

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3
Q

What are the components of DNA?

A
  1. deoxyribose sugar
  2. phosphate
  3. on of the four bases: adenine, thymine, guanine, and cytosine
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4
Q

What are the differences between nucleosides, nucleotides, and nucleic acids?

A

nucleoside: base and sugar
nucleotide: nucleoside and phosphate
nucleic acids: a sequence of linked nucleotides

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5
Q

What are the bases vs. the nucleosides?

A

bases: adenine, thymine, guanine, and cytosine

nucleosides: adenosine, thymidine, guanosine, and cytidine

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6
Q

Each strand of DNA contains info for…

A

replicating the other strand and protein structure

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7
Q

What are the two processes needed for protein synthesis?

A

transcription (DNA to mRNA)
translation (mRNA to protein)

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8
Q

What are the base pairs?

A

AU/AT and GC

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9
Q

What two things are different about RNA structure than DNA structure?

A

RNA has a ribose instead of a deoxyribose, and uracil instead of thymine

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10
Q

Where does transcription take place?

A

the nucleus

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11
Q

Why does mRNA move out of the nucleus while DNA stays in the nucleus?

A

RNA is not as resistant to hydrolysis

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12
Q

What are the steps of transcription?

A
  1. DNA strands unwind and separate
  2. DNA strand containing the specific gene serves as a template strand
  3. RNa nucleotides are matched to complementary DNA bases
  4. mRNA molecule is complete and DNA rewinds
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13
Q

During transcription, DNA is read in the —– direction and RNA is made in the ——- direction.

A

DNA read in the 3’-5’ direction
RNA made in the 5’-3’ direction

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14
Q

What does RNA polymerase do?

A

location where the new bases are added to the template strand and form the new mRNA strand

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15
Q

Describe RNA splicing

A

introns (parts that are not the protein’s code) are removed and exons (parts that code the protein) are joined together to make the complete mRNA

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16
Q

Where does translation occur?

A

ribosomes in the cytoplasm

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17
Q

mRNA has 3 letter segments called —– that…

A

3 letter segments called codons,
code for an amino acid

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18
Q

tRNA has 3 letter segments called —– that…

A

3 letter segments called anticodons,
are complimentary to the mRNA codon

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19
Q

What bond connects the amino acids during translation?

A

peptide bonds

20
Q

The DNA in every cell is…

A

the same

21
Q

How is gene expression regulated?

A

different types of cell express different genes, which causes specialization (the genes are the same, just different ones are expressed)

22
Q

What is the promotor in translation?

A

DNA sequence upstream of (before) the start of a gene where the RNA polymerase binds

23
Q

What are transcription factors?

A

proteins that bind to the promotor to augment the binding of RNA polymerase (control if that gene is able to be transcribed)

24
Q

Where does transcription start?

A

the start codon of the coding sequence (not the promoter region, that’s just where the RNA polymerase binds)

25
Q

What are the 5 control points for protein?

A
  1. transcriptional control
  2. RNA processing control
  3. RNA transport control
  4. translation control
  5. protein activity control
26
Q

It is important to control protein synthesis because faults can cause…

A

defective proteins which lead to many disorders

27
Q

Mutant sodium channels that have defective inactivation can cause…

A

hyperkalemic periodic paralysis, long QT syndrome, and inherited epilepsy

28
Q

Do all proteins turnover at the same rate?

A

No - different proteins have different rates, and the same protein can even have different turnover rates in different tissues

29
Q

What is the half-life?

A

time to decay to half of its initial value

30
Q

What is a common way to study protein synthesis and degradation?

A

labeled methionine incorporation:

incubate cells with 3H-methionine and measure the incorporation into the target protein, then immunoprecipitate using an antibody that binds the target, separate with electrophoresis, and look for radioactivity from the 3H

31
Q

What is pulse-chase?

A

more accurate way to study protein synthesis and degradation
1. pulse - incubate cells with 3H-methionine to allow incorporation into the target protein
2. chase - incubate cells with nonradioactive methionine and watch the disappearance of the labeled target protein

32
Q

Proteins are degraded by —— which is compartmentalized in two ways:

A

proteolysis, compartmentalized by lysosomes or proteasomes

33
Q

What are lysosomes? Describe their composition.

A

membrane-bound compartments with various hydrolases, including proteases, and a low pH

34
Q

Contrast the things that lysosomes and proteasomes degrade.

A

lysosome: long-lived cytosolic proteins, integral membrane proteins in secretory and endosomal vesicles

proteasome: short-lived cytosolic proteins, ER membrane proteins

35
Q

What allows lysosomes and endosomes to have a low pH?

A

proton pumps called V-ATPase shift H+ into them via primary active transport

36
Q

How are proteins headed for the lysosomes tagged?

A

single molecule of ubiquitin (mono-uniquitination)

37
Q

Lysosomes degrade both…

A

extracellular materials taken in by endocytosis, and cellular material shifted in via cytoplasmic vesicles

38
Q

What is autophagy? What are the steps?

A

cell mechanism for disposing of large particles
1. envelopment
2. sealing
3. merging with a lysosome
3. resulting residual body

39
Q

What is crinophagy? How does it occur?

A

process for the degradation of secretory proteins that have gone beyond their “shelf life”

lysosomes fuse with old secretory vesicles and degrade their contents

40
Q

What is inside lysosomes, and how does it get there?

A

they contain many different hydrolytic enzymes

precursors are tagged with mannose-6-phosphate in the golgi, trans golgi receptors divert the enzyme precursors to endosomes and lysosomes where they are activated

41
Q

What is the basic structure of a proteasome?

A

protein subunits assemble into a proteolytic machine, and proteolysis sites line the inside of the narrow chamber

regulatory complexes guard the openings to allow access only to selected, unfolded polypeptides

42
Q

What do proteasomes degrade?

A

key substrates, abnormal and misfolded proteins, and some degrade antigens

(always in response to signaling cascades or at specific transitions in the cell cycle)

43
Q

Describe the detailed structure of a proteasome

A
  • main core and a cap at each end
  • core is the 20S proteasome, which has 28 subunits arranged in 4 7-member rings (alpha are the top and bottom, beta are the middle two)
  • proteolytic sites on the beta rings face the inner chamber
44
Q

How are unneeded or damaged proteins marked for destruction by a proteasome?

A

covalent attachment of chains of a small protein called ubiquitin (polyubiquinated)

45
Q

How do proteins and ubiquitin link?
Describe the link and the process

A

side chain amino acid groups of lysine on the target protein covalently link to the C-terminus of uniquitin (a glycine)

  • ubiquitin activating enzyme (E1), ubiquitin conjugating enzyme (E2), and ubiquitin protein ligase (E3)
  • one ATP is hydrolyzed for every ubiquitin molecule attached to the target protein
46
Q

Describe the ubiquitin conjugation mechanism

A
  1. E1 activates ubiquitin
  2. E2 carries ubiquitin
  3. E3 attaches ubiquitin to the substrate
  4. mono (lysosome) poly (proteasome)

PSIO303 Integrative Cellular Physiology (16 decks)

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