neetpg | Anatomy2Medicine
Collagen

Collagen

  Collagen   Most abundant protein in the human body.   Extensively modified by  posttranslational modification. Organizes and strengthens extracellular matrix.   Type I Most common (90%)—Bone (made by osteoblasts), Skin, Tendon, dentin, fascia, cornea, late wound repair Type I: bone.   ↓ production in osteogenesis imperfecta type I.   Type II Cartilage (including hyaline), […]

Cell Organelles

Cell organelles

Cell organelles   Rough endoplasmic reticulum   Site of synthesis of secretory (exported) proteins and of N-linked oligosaccharide addition to many proteins.   Nissl bodies (RER in neurons)—synthesize peptide neurotransmitters for secretion. Free ribosome   unattached to any membrane   site of synthesis of cytosolic and organellar proteins.   Mucus-secreting goblet cells of the small […]

Cyclins

Cell cycle phases Cyclins CDKs

action of cyclins and cyclin-dependent kinases (CDKs) of which there are several. The activity of the CDKs is dependent on interaction with cyclins. However, the presence of CDK inhibitory proteins, CIPs, results in inhibition of the activity of CDKs. CIPs bind and inhibit CDK1, 2, 4, and 6 complexes. Thus, an increase in the activity […]

protein synthesis

Protein synthesis

Protein synthesis   Initiation   Initiated by GTP hydrolysis   initiation factors (eukaryotic IFs) help assemble the 40S ribosomal subunit with the initiator tRNA and are released when the mRNA and the ribosomal 60S subunit assemble with the complex.   Eukaryotes: 40S + 60S →80S (Even). PrOkaryotes: 30S + 50S → 70S (Odd). ATP—required for […]

RNA processing

RNA processing

  RNA processing (eukaryotes)   Initial transcript is called heterogeneous nuclear RNA (hnRNA). hnRNA is then modified and becomes mRNA.   The following processes occur in the nucleus following transcription:   Capping of 5′ end (addition of 7-methylguanosine cap) Polyadenylation of 3′ end (≈ 200 A’s) Splicing out of introns Capped, tailed, and spliced transcript […]

RNA

RNA

  DNA/RNA/protein synthesis direction DNA and RNA are both synthesized 5′ → 3′.   The 5′ end of the incoming nucleotide bears the triphosphate (energy source for bond). The triphosphate bond is the target of the 3′ hydroxyl attack.   Drugs blocking DNA replication often have modified 3′ OH, preventing addition of the next nucleotide […]

t RNA

t RNA

Structure 75–90 nucleotides   2º structure, cloverleaf form anticodon end is opposite 3′ aminoacyl end.   All tRNAs, both eukaryotic and prokaryotic, have CCA at 3′ end along with a high percentage of chemically modified bases. (Remember : CCA Can Carry Amino acids. )   The amino acid is covalently bound to the 3′ end […]

Angelman syndrome

Angelman syndrome Chr 15, normally active maternal (AngelMan = maternal) allele deleted. MR, seizures ataxia, inappropriate laughter (“happy puppet”). Other parent’s allele inactivated / imprinted by methylation can also be from uniparental disomy (2 copies of chr from 1 parent). Prader-Willi syndrome = paternal counterpart (“happy puppet”).

DNA damage

DNA repair

  DNA repair Single strand       Nucleotide excision repair   Specific endonucleases release the oligonucleotide-containing damaged bases; DNA polymerase and ligase fill and reseal the gap, respectively. Repairs bulky helix-distorting lesions. Defective in xeroderma pigmentosum, which prevents repair of pyrimidine dimers because of ultraviolet light exposure.     Base excision repair   Base-specific […]

ALPORT

Alport

Alport’s syndrome Defects in type IV collagen synthesis   most common form X-linked recessive   Hereditary nephritis,   deafness +/- ocular disturbances (type IV collagen important in BM of kidney, ears, eyes)   Exam MCQ Alport syndrome is due to the mutation in the genes encoding Type I collagen Type II collagen Type III collagen […]