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all io > Cell Bio > Flashcards

Cell Bio Flashcards

1
Q

Total protein produced by genes in lifetime

A

About 100,000 proteins

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2
Q

What are functiona of microRNA, small interefering RNA, small nuclear RNA

A

MiRNA are formed in cytoplasm from pre-miRNA regulate gene expression and block translation siRNA cause degradation of mRNA and also regulate gene expression snRNA helps in splicing of mRNA

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3
Q

RNA polymerase

A

Synethesize mRNA from DNA
Does not require primer
1) binds to promoter region
2) breaks H-bonds and uncoils DNA
3) adds new nucleotide by breaking p bonds of old nucleotide and from this energy does make covalent bonds to new nucleotide
4) at termination points it gets removed and thus mRNA . H bonds of mRNA break Both dna strands attach back because they have high affinity

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4
Q

RNA polymerase enzymes

A

RNA polymerase I: most rRNA (5.8S, 18S, 28S)

  • RNA polymerase II: mRNA
  • RNA polymerase III: rRNA (5S),

RNA door name meer

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5
Q

2 RNA polymerase inhibitors

A

RNA Polymerase Inhibitors

  • Rifampin
  • Inhibits bacterial RNA polymerase
  • Used to treat tuberculosis
  • Actinomycin D
  • Used as chemotherapy
  • Inhibits RNA polymerase
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6
Q

Promoters

A 
Non-transcribed DNA portion where RNA and transcription factors attach 
e-g Promoters
* Very common eukaryotic promoter
TATA Box
* TATAAA
Binds transcription factors (TFIID)
*CCAAT sequence
CAAT Box
GC Box
GGGCGG
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7
Q

Silencer

Enhancer

A

Silencers
• DNA sequence that decreases rate of transcription
*Binds transcription factors called repressors
*^Repressors prevent RNA polymerase binding

Enhancers
DNA sequences that increase rate of transcription
Binds transcription factors called activators

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8
Q

Untranslated regions of mRNA

A 
Portions of mRNA at 5’ and 3’ ends
**Not translated into protein
*5’ UTR upstream from coding sequence
•Recognized by ribosomes to initiate translation
•3' UTR found following a stop codon
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9
Q

• Three key modifications to mRNA before leaving nucleus

A 
1)• 5’ capping
Addition of 7-methylguanosine to 5’ end
Distinguishes mRNA from other RNA
2)• Splicing out of introns 
Occurs during transcription
Introns always have two nucleotides at either end 3' splice site: AG 5’ splice site:GU
• 3’ polyadenylation
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10
Q

Chain initiating and chain terminating codons

A

C i= AUG

C t= UAA UAG UGA

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11
Q

mRNA splicing(process)

A

RNA Splicing
•primary transcript combines with snRNPs (small nuclear ribonucleoproteins)
• snRNPs and mRNA forms “spliceosome”
• Loop of mRNA with intron is formed (“lariat”)
• Lariat released → removes intron

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12
Q

How many proteins are formed from 1 gene

A 
Alternative Splicing
• Allows many proteins from same gene
• DNA: Exon1 – Exon 2 – Exon 3 – Exon 4 … Exon 10
• Protein 1: Exon1 – Exon 3 – Exon 7
• Protein 2: Exon 2 – Exon 5 - Exon 10
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13
Q

How transcription terminates

Enzyme

A

3’ Polyadenylation

• Occurs at termination of mRNA transcription
• Triggered by specific DNA/RNA sequences
• “Polyadenylation signal:” AAUAAA
• AAUAAA followed by 10-30 nucleotides then CA
Leads to termination of
transcription
3’ Polyadenylation
3’ Polyadenylation

• Enzyme: Poly-A polymerase (PAP)
Adds ~200 adenosine nucleotides to 3’3’ end mRNA

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14
Q

Nucleotides are formed in which way

A

New nucleotides are always arranged from 5’ prime to 3’ prime

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15
Q

3 main lipids of lipid bilayer

Composition of Outer and inner leaflet of c.m

A

Phospholipid+cholesterols+sphingolipids

Outer leaflet=phosphotidyl choline+sphingolmyelin
Inner leaflet= phosphotidyl (serine+ethanolamine)

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16
Q

What can pass through cm

A

Lipid soluble substances i-e 02,CO2, alcohol etc

17
Q

How cell knows if ATP is depleted

A

When ATP breaks into cAMP and cAMP activates glycogen splitting enzyme phosphorylase that break glycogen into glucose

18
Q

peroxisomes 2 differences from lysosomes 2 enzymes 2 functions

A

Either self replicatory or made from SER instead of golgi apparatus and have oxidases instead of hydrolases

Oxidase make H2O2 catalase that’s also an oxidase

Half of alcohol —> acetaldehyde
Catabolize large chain fatty acids

19
Q

Whats the only mean of transportation of macromolecules such as proteins

A

Pinocytosis

Phagocytosis occurs when cells engulf large bodies such as whole cells, bacteria etc

20
Q

Coated pits and clathrin

A

Group of receptors concentrated at a point are called coated pits

Catherin are fibrillar proteins that start pinching inward along with the help of actin and myosin

21
Q

Glycocalyx and it’s function

A

Glycocalyx is negatively charged glycoprotein and glycoprotein that us present around cell membrane it is mainly composed of carbohydrates .it differentiate cm from other intercellular membranes and acts as barrier

22
Q

Gap junction

A

Also called as nexus Allow the movement of ions and chemicals b/w cells present in heart and basal epithelial cells of intestinal mucosa
Each gap junction has two halves each half is surrounded by 6 protein subunits called connexins

23
Q

Desmosomes

Hemidesmosomes

A

Desmosomes are also called as macula adherens they combine cell to cell by intermediate filaments they function like tight junctions

H… are cell to extracellular matrix junctions by intermediate filaments

24
Q

What are the adherens junction and focal junction

Where they are present

A

They connect actin filaments of one cell to other by some transmembrane proteins called cadherins
Present in intercalated discs of heart and epidermis of skin

Connect actin filaments of cell to extracellular matrix by proteins called integrins present in epithelial lining

25
Q

Tight juction and proteins involved

A

Proteins involved: Occludin Claudin JAMs Cingulin Symplekin Function: Strength and stability to tissues ,Formation of blood­brain barrier

Present in Epithelial lining of intestinal mucosa and renal tubule

26
Q

Number of cells produces and dies every single day

A

10 million

27
Q

How is apoptosis inactivated and when activates

A

Normally caspases are inhibited by Apoptosis inhibiting Factor(AIF)
When cell recieves stimulus for apoptosis mitochondria release two proteins cytochrome c and SMAC they inactivate AIF and them smac and aif combine to form apoptosome which activate caspases
“”second mitochondria-derived activator of caspases (SMAC)

28
Q

Necrosis

A

Unprogramed death of cells common causes are injury cancer inflammation and infection

29
Q

Process of necrosis

A

Damage to cell membrane causes leakage of intracellular material this alters its environment ca is released from mitochondria and induces release of toxic material which activates lysosomes and hence cell dies cell components are ingested by neibours

30
Q

Reaction of neighbouring tissue after necrosis

A

Neighbouring tissue react to cell membrane derivative like arachindonic acid and hence cause dilation and permeability of vessels histamine is released which causes pain and inflammation
|^T—> redness

31
Q

Secretions produced by lysosomes

A

perforin, granzymes, melanin and serotonin
Lysosomes in the cytotoxic T lymphocytes and natural killer (NK) cells secrete perforin and granzymes, which destroy both viral-infected cells and tumor cells. Perforin is a pore-forming protein that initiates cell death. Granzymes belong to the family of serine protease
Melanocytes produce melanin
serotonin, which is a vasoconstrictor substance and inflammatory medi

32
Q

Microtubules

A

They are hollow tubular structures made of tubulin dimer
Give support strength and shape to the cell
Act as channels for movement of besicles secretion and orgenelles
For structures like cillia and flegella
Form spindle fibers

33
Q

Intermediate filaments

Microfilaments

A

Fibrous proteins are arranged around nucleus and periphery in the form of network
They give shape and connect cells through desmosomes

Fine long threads made of actin and myosin
Give strength and resistance against pulling forces and contraction

34
Q

Total codons

A 
Total=64
61 for amino acids 3 stop codons
Initiating codon(AUG)=methionine

all io (13 decks)

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