Usmle Cell Biology

Front 1

Function of lamins and role in mitosis?

Back 1

Lamins attach chromatin to the inner membrane and participate in nuclear assembly and disassembly during mitosis.

Front 2

What signal activates lamins to initiate nuclear disassembly?

Back 2

Phosphorylation of lamins by lamin-kinase during prophase.

Front 3

Role of nucleolus in ribosome production?

Back 3

The nucleolus is the site of ribosomal RNA synthesis and ribosome assembly.

Front 4

The 2 major residues in histone protein structure, and why they are important/present?

Back 4

Arginine and Lysine, both are positively charged, and provide the charge attraction to bind negatively charged DNA which is coiled about the histones.

Front 5

30nm chromatin fiber?

Back 5

Heterochromatin, solenoid fibers, highly compacted, transcriptionally inactive. Represents 10% of chromatin in typical cell, and entire Barr Body

Front 6

10nm chromatin fiber

Back 6

Euchromatin, transcriptionally active, 90% of chromatin in typical cell.

Front 7

Sites of ribosomal synthesis, transport, and assembly.

Back 7

Ribosome = rRNA + Protein. 2 subunits 60s and 40s. 60s is synthesized in Nucleolus, 40s in nucleus, transported to cytoplasm via nuclear pores.

Front 8

Polysome

Back 8

A cluster of ribosomes on the same mRNA all translating to protein in the 5' to 3' direction.

Front 9

Rough ER

Back 9

continuous w/ nuclear envelope, synthesizes proteins destined for Golgi, Secretion, Lysosome, Membrane. Prominent in secretory cells.

Front 10

Smooth ER

Back 10

continuous w/ RER
biosynthesis of phospholipids, triglycerides, sterols, steroid hormones,

Front 11

Non biosynthetic functions of the SER

Back 11

Detoxification, increases water solubility of compounds for excretion, via (phase 1) Hydroxylation (p450) and (Phase 2) Conjugation w/ polar carbohydrate moieties.

Front 12

What does Microsomal mean, what is its importance to detoxification, and pharmacology?

Back 12

Microsomal refers to the cell lysate fraction containing SER, only microsomal enzymes of detoxification are inducible, this includes all CYP450 and a single Conjugation glucoronyl transferase (phase 2)

Front 13

SERs relation to Glycogen Degradation and Gluconeogenesis.

Back 13

Glucose-6-Phosphatase removes -P from G-6-Ps which have been cleaved from glycogen, it is an integral membrane protein of the SER. Key/Rate controlling step in gluconeogensis.

Front 14

Role of the Golgi in protein sorting.

Back 14

Trans golgi is the site of carbohydrate moiety addition and manipulation in post-translational modification. Determines secretory, lysosomal, plasma membrane destination of proteins.

Front 15

Hyperproinsulinemia and its organelle level dysfunction

Back 15

failure of a Golgi peptidase to cleave and subsequently target preproinsulin, resulting in elevated proinsulin, similar Cx to DM.

Front 16

How are proteins targeted to the lysosome for degradation and recycling?

Back 16

Phosphorylation of mannose residues by N-acetylglucosaminidase-phosphotransferase

Front 17

What is the function of the lysosome, and where are its components made and sorted?

Back 17

Membrane bound organelle which contains numerous degradative enzyemes, pH 5.0 hydrolases, key functions include degradation of sphingolipids and glycoproteins, and nucleotides. Enzymes are synthesized in RER, and targeted to lysome in the golgi by -P of mannose residues.

Front 18

Young child < 10 y/o, skeletal abnormalities, restricted joint movements, retardation. Histology shows large inclusion bodies in fibroblasts, and extracellular degradation?

Back 18

I-Cell disease, deficiency in N-Acetylglusamine-phosphotransferase, no M-6-P on hydrolase enzymes, secreted instead of targeted to lysosome (which accumulate undegraded glyco-conjugates)

Front 19

What diseases are caused by deficiency in sphingolipid breakdown within the lysosome?

Back 19

Gauchers, Nieman-Pick, Tay-Sachs

Front 20

Function of the peroxisome?

Back 20

synthesis and degradation of hydrogen peroxide, B-Ox of VLCFA > C24, phospholipid exchange, including generation of phosphatidyl-choline. Peroxisomes have CATALASE.

Front 21

Diseases associated w/ accumulation of bile-acid precursors, d/t a deficiency in peroxisomal degradation of VLCFA.

Back 21

1. Zellweger's, Cerebrohepatorenal, syndrome.
2. neonatal adrenoleukodystrophy
3. infantile refsum disease
4. hyperpipecolatemia.

Front 22

What is unique about the synthesis of peroxisome enzymes vs. lysosome enzymes?

Back 22

Peroxisomal enzymes are synthesized on free polysomes and targeted directly to the peroxisome (golgi is not involved)

Front 23

What is the significance of phosphatidylserine (PS) position on the lipid bilayer membrane

Back 23

PS normally only found on inner-membrane, if found on outer membrane signifies apoptotic process.

Front 24

Differences between inner and outer membrane of the mitochondria?

Back 24

Outermembrane is highly permeable, w/ lots of porins. Inner membrane is relatively impermeable d/t high cardiolipin content. Inner membrane forms cristae, which contain channels responsible for ETC and OxPhos.

Front 25

Important mitochondrially inherited diseases which affect males more than females?

Back 25

Leber's optic neuropathy, pearson marrow-pancreas syndrome, male infertility mitochondrial.

Front 26

What cytoskelatal process is responsible for contractile and motility within a cell?

Back 26

Microfilament, actin-myosin treadmilling.

Front 27

What filament forms the core of a microvilli?

Back 27

Actin filaments

Front 28

What cytoskeletal filament anchors tight junctions at the zonula adherens?

Back 28

Microfilaments-actin

Front 29

What are the 3 major Type II intermediate filaments, and where are they found?

Back 29

Desmin - Sketal muscle, cardiac, and GIT smooth muscle.
Vimentin - fibroblasts, -cytes, vasc smooth musc.
GFAP - astrocytes and schwann cells

Front 30

What are the motor molecules associated with microtubule function?

Back 30

Dynein - retrograde transport
Kinesin - anerograde transport
Found in true cillia and flagella and are used in mitotic chromatid seperation

Front 31

calcium ion dependant adhesion molecules, which dimerize across cell membranes to other cells?

Back 31

cadherins

Front 32

the molecule which links the cytoplasmic portion of ca+ ion dependant adhesion molecules which dimerize across cell membranes to actin filaments?

Back 32

catenin

Front 33

calcium independant cell adhesion molecule that is part of the hemidesmosome _____?
Binds to which ECM components?

Back 33

Integrins bind to fibronectin and laminins and play important roles in leukocyte adhesion and migration

Front 34

What is the drug and it's MOA thta is used to prevent inflammatory cell migration in the treatment of gout.

Back 34

Colchicine prevents microtubule polymerization and prevents neutrophil migration

Front 35

Which two drugs are utilized as an anticancer therapy because they inhibit formation of the mitotic spindle?

Back 35

Vincristine and Vinblastine

Front 36

Two major molecules of the junction which acts as a barrier to diffusion?

Back 36

occludins and claudins

Front 37

zonula adherins has which calcium dependant adhesion molcule?

Back 37

cadherins which bind to actin filaments

Front 38

desmosomes are composed of which adherence molecule

Back 38

cadherins which bind to IF tonofilaments

Front 39

adherence to basal lamina, type 4 collagen via fibronectin and laminin?

Back 39

hemidesmosomes

Front 40

auto antibodies against hemidesmosomes?

Back 40

bullous pemhigoid, often drug induced, spares the oral mucosa

Front 41

autoantibodies against desmosomes?

Back 41

pemphigus vulgaris, involves the oropharynx and skin ruptures easily, leaves dark spots

Front 42

which major cell types and locations have microvilli

Back 42

1. columnar epithelia of the large and small intestine
2. proximal tubule of the kidney
3. columnar epithelium of the respiratory lining

Front 43

why is kartageners associated with chronic respiratory infections and infertility?

Back 43

defect in in dynein resulting in dysfunctional 2:9 organization and non functional cillia used by sperm and pseudostratified cilliated columnar respiratory epithelium.

Front 44

simple columnar epithelium

Back 44

found in small and large intestine

Front 45

simple squamous epithelium

Back 45

endothelium of blood vessels, mesothelium of serous membrane, and epithelium of renal glomerular capsule

Front 46

pseudostratified columnar epithelium

Back 46

nasal cavity, trachea, bronchi, epididymis

Front 47

transitional epithelium

Back 47

ureter and bladder, transitional because cell shape transitions from cuboidal to squamous based on bladder distention

Front 48

stratified squmous epithelium

Back 48

oral cavity, pharynx, esophagus (non keratinizing) skin (keratinizing)

Front 49

simple cuboidal epithelium

Back 49

renal tubules and secretory cells of salivary acinar glands

Front 50

stratified cuboidal epithelium

Back 50

ducts of salivary glands

Front 51

which salivary gland is pure serous?

Back 51

parotid