Usmle Step 1 Biochemistry Part 4

Front 1

Steps in protein synthesis?

Back 1

Initiation, elongation, termination.

Front 2

Protein synthesis: Initiation.

Back 2

A ribosome attaches to the mRNA and stars to code the FMet codon (AUG, GUG or UUG).

Front 3

Protein synthesis: Elongation.

Back 3

tRNA brings the corresponding amino acid to each codon as the ribosome moves down the mRNA strand.

Front 4

Protein synthesis: Termination.

Back 4

Reading of the final mRNA codon which ends the synthesis of the peptide chain and releases it.

Front 5

What are the protein post translational modifications?

Back 5

Trimming, Covalent alterations, proteasomal degradation.

Front 6

Posttranslational modification: Trimming.

Back 6

Removal of N- or C- terminal pro-peptides from zymogens togenerate mature proteins.

Front 7

Posttranslational modification: Covalent alterations.

Back 7

Phosphorylation, Glycosylation, Hydroxylation.

Front 8

Posttranslational modification: Proteosomal degradation.

Back 8

Attachment of ubiquitin to defective proteins to tag them for break down.

Front 9

Enzyme regulation methods?

Back 9

Enzyme concentration alterations, covalent modification, proteolytic modification, allosteric regulation, pH, temperature and transcriptional regulation.

Front 10

What are the cell cycle phases?

Back 10

G1, S phase, G2, Mitosis.

Front 11

What are the cells that remain in the G0 phase and regenerate from stem cells?

Back 11

Neurons, skeletal and cardiac muscles, RBCs.

Front 12

What are the cells that enter the G1 state from G0 when stimulated?

Back 12

Stable cells: Hepatocytes, Lymphocytes.

Front 13

What are the cells that never go to G0 and divide rapidly with a short G1?

Back 13

Labile cells: Bone marrow, gut epithelium, skin, hair follicles.

Front 14

Where in the cell are N-Linked oligosaccharides added to proteins?

Back 14

RER.

Front 15

What do Nissl-bodies synthesize?

Back 15

Enzymes and peptide neurotransmitters.

Front 16

Cells rich in RER?

Back 16

Mucus secreting goblet cells of the small intestine and anti-body secreting plasma cells.

Front 17

Cell site where steroid synthesis and detoxification of drugs and poisons take place?

Back 17

SER.

Front 18

Cells rich in SER?

Back 18

Hepatocytes, steroid hormone producing cells of the adrenal cortex are rich in cells.

Front 19

Failure of addition of mannose-6-phosphate to lysosome proteins, enzymes are secreted outside the cell instead of being targeted to the lysosome.

Back 19

I-cell desease also refered to as mucolipidosis II (ML II).

Front 20

Coarse facial features, clouded corneas, restricted joint movement, and high plasma levels of lysosomal enzymes. Often fatal in children.

Back 20

I-cell disease.

Front 21

Kartagener's syndrome.

Back 21

Immotile cilia due to dynein arm defect. Results in male and female infertility, bronchiectasis and recurrent sinusitis.

Front 22

Plasma membrane composition?

Back 22

Asymmetric fluid bilayer. Cholesterol 50%, phospholipids 50%, sphingolipids, glycolipids and proteins.

Front 23

Major component of RBC membranes, of myelin, bile and surfactant.

Back 23

Phosphatidylcholine.

Front 24

Where is the ATP site on a sodium pump?

Back 24

Cytoplasm side.

Front 25

How many K and how many Na does a sodium pump move for each ATP?

Back 25

3 Na+ go out and 2 K+ come in.

Front 26

How does Ouabain work?

Back 26

Inhibits the sodium pump. Binds to K+ site.

Front 27

What drugs inhibit the Na+ K+ ATPase causing an increase in cardiac contractility.

Back 27

Cardiac glycosides.