Ch. 1 - The Cell as a Unit of Health and Disease Flashcards

Question

Describe the process of miRNA trasncription

Answer 1

miRNA genes are transcribed, producing a primary miRNA (pri-miRNA) pri-miRNA is progressivley processed through various steps, including trimming by the enzyme DICER, produces mature single-stranded miRNAs of 21 to 30 nucleotides in length.

Answer 2

The mature single-stranded miRNA associate with RNA-induced Silencing Complex (RISC) The miRNA-RISC either form a perfect match or imperfect match A perfect match miRNA-RISC causes the target mRNA to be cleaved, ultimately silencing the gene An imperfect match miRNA-RISC binds to target mRNA and represses tranlsational, ultimately silencing the gene

Answer 3

All mRNAs contain a so-caled "seed sequence" in their 3' untranslated region (UTR) that determines the specificity of miRNA binding and gene silencing (post-translational silencing)

Answer 4

Small Interfering RNAs (siRNAs) are short RNA sequences that can be introduced experimentally into cells. They are miRNAs that are made in the laboratory siRNAs serve as substrates for DICER and interact with the RISC complex in a manner analogous to miRNAs They are useful to knockdown target genes in the lab and as a potential therapeutic strategy (i.e. knockdown oncogenes)

Answer 5

Long Noncoding RNA There are 10-20 fold more lncRNAs than mRNAs lncRNAs modulate gene expression in many ways They can bind regions of chromatin, restricting RNA polymerase access to coding genes within the region. Example: XIST Many enhancers are sites of lncRNA synthesis, and these lncRNA appear to often increase transcription from gene promoters through a variety of mechanisms

Answer 6

Transcribed from the X chromosome, XIST is an lncRNA that plays a role in physiologic X chromosome inactivation in females. The gene responsible for XIST is able to avoid inactivation.

Answer 7

Rough ER synthesizes new proteins destined for the plasma membrane or secreted proteins using membrane embedded ribosomes These proteins are assembled in the Golgi apparatus Proteins intended for the cytosol are sythesized by free ribosomes in the cytosol

Answer 8

Smooth ER are abundant in cells that produce lots of Steroid Hormones and Lipoproteins like the gonads and liver -- lipids Smooth ER also used for modification of hydrophobic compounds (i.e. drugs) into water-soluble molecules for excretion - Conjugation - liver

Answer 9

Lysosomes are intracellular organelles that contain degradative enzymes that permit the digestion of a wide range of macromolecules including proteins, polysaccharides, lipids, and nucleic acids

Answer 10

Proteasomes are a specialized kind of grinder that selectively chews up denatured proteins Release peptides in the process In some cases the peptides generated canbe presented in the context of Class I Major Histocompatibility (MHC) Molecules - Antigen presentation in the context of intracellular pathogens (i.e., virally infected cells) required proteasomes and MHC Class I molecules

Answer 11

**A small organelle that plays a specialized role in the breakdown of fatty acids, generating hydrogen peroxide in this process.

Answer 12

Structures that shuttle internalized material to the appropriate intracellular sites Or they direct newly synthesized materials to the cell surface or targeted organelle/

Answer 13

Structural proteins responsible for many functions - Cell movement of organelles and proteins - Movement of cell in its environment - Maintain basic cellular shape and intracellular organization (which are vital to maintaining cell polarity)

Answer 14

Powerhouse of the cell Most ATP that powers teh cell is made through oxidative phosphorylation in the mitochondria They also serve as an important source of metabolic intermediates that are needed for anabolic metabolism They are sites of syntehsis of certain macromolecules (e.g., heme) They contain important sensors of cell damage that can initiate and regulate the process of programmed cell death

Answer 15

PTI is membrane lipid that occupies mostly the inner membrane (cytosolic) leaflet Can be phosphorylated to serve as an electrostatic scaffold for intracellular proteins Can be hydrolyzed by phospholipase C to generate second messengers in the cytosol like IP3 and DAG

Answer 16

A membrane lipid that is normally restricted to the inner (cytosolic) leaflet where it confers a negative charge involved in electrostatic protein interactions **When it flips to the extracellular surface (which happens in cells undergoing apoptosis (programmed cell death), it becomes an "eat me" signal for phagocytes **It also serves as a cofactor for Platelets when clotting blood

Answer 17

Membrane bound molecuels that are preferentially expressed on the extracellular surface. Glyoclipids are important in cell-cell and cell-matrix interactions (including inflammatory cell recruitment and sperm-egg interactions)

Answer 18

Phosphatidylethanolamine is a membrane lipid found mostly on the inner leaflet of the cell membrane

Answer 19

Aggregates of proteins and cholesterol that have similar solubilities Allows collections of proteins to come together for cell signaling Nonrandom distribution of lipids and membrane proteins effects cell-cell and cell-matrix interactions, intracellular signaling, and generation of specialized membrane regions involved in the secretory or endocytic pathways

Answer 20

Most proteins are integral or transmembrane proteins - They have one or more hydrophobic alpha helical segment that traverse the lipid bilayer - They have positively charged aminoacids in their cytoplasmic domains, which anchor the proteins to the negatively charged head groups of membrane phospholipids. Proteins may be synthesized in the cytosol and postranslationally attached to prenyl groups (e.g. farnesyl, related to cholesterol) or fatty acids that insert into the CYTOSOLIC SIDE of the plasma membrane Insertion into the membrane may occur through glycosylphosphatidylinositol (GPI) anchors on the EXTRACELLULAR SURFACE surface of the membrane Peripheral membrane proteins may noncovalently associate with true transmembrane proteins