practice q's - foundation Flashcards
which of the following mechanisms terminates a signal transduction pathway?
activation of protein phosphatases
which of the following receptors is located inside the cell?
nuclear hormone receptors
define cell
smallest structural & functional unit capable of carrying out life processes
what is a cell membrane & what is its composition?
A thin, pliable, semipermeable membrane that envelops the cell and separates cytoplasm from ECF.
Composition:
Proteins (55%)
Lipids (42%)
Carbohydrates (3%)
explain the structure of the cell membrane
Lipid bilayer: Hydrophilic portion (Phosphate) & Hydrophobic (lipid)
Proteins-
Integral proteins: Through and through
Peripheral proteins: Attached only at the surface
Glycocalyx
What are the Important functions of Glycocalyx?
The carbohydrate moieties attached to the outer surface of the cell;
- Repel negatively charged substances.
- Attaches to the glycocalyx of the other cells.
- Acts as receptor substances for the binding of hormones.
- Plays a role in immune reactions.
What are Vaults?
Barrel-shaped tiny organelles
Size – 3 times the size of a ribosome
Composed of:
- Protein
- Vault RNA (vRNA)
Functions:
- Intracellular transport; helps transport molecules like RNA and proteins within the cell.
- Multi-drug resistance: involved in removing harmful substances, contributing to drug resistance
the term “glycocalyx” refers to
the negatively charged carbohydrate layer on the outer cell surface
glycocalyx: loose negatively charged carbohydrate coat on outside of surface of cell membrane
- combination of proteins or lipids and “glyco” portion almost always protrudes outside of the cell
what are mRNA and what is their role?
long, single RNA strands that are suspended in cytoplasm, composed of several 100-1000 RNA nucleotides in unpaired strands
carry genetic code to cytoplasm for controlling the type of protein formed
role of transfer RNA
transports activated amino acids to the ribosomes
role of ribosomal RNA
forms ribosomes
micro RNAs (miRNAs) role + how they’re formed
regulate gene expression by binding to complementary region of RNA & repressing translation or promoting mRNA degradation before it can be translated by the ribosome
formed in the cytoplasm from pre-miRNAs and processed by enzyme dicer
which of the following is true for both pinocytosis and phagocytosis?
involves recruitment of actin filaments
involve movement of the plasma membrane so require requirement of actin & other cytoskeleton elements
acid lipases
enzyme responsive for hydrolysis (breakdown) of cholesteryl esters & triglycerides
localized to lysosomes
include: nucleases, proteases, & polysaccharide-hydrolyzing enzymes
where are membrane proteins synthesized and where does most of their post-translational modification occur?
synthesized: rough ER
post-translational modification: Golgi apparatus
The observation that abnormal cleavage of mannose residues from glycoproteins causes an autoimmune disease in mice supports the role of this structure in the normal immune response
glycocalyx
- glycocalyx has different sugars attached and one of these sugars can be mannose so cleaved off = glycocalyx doesn’t work properly
glycocalyx functions:
- cell-cell interactions
- cell-ligand interactions
- immune response
where does initiation of translation take place?
cytosol
ribosomes are either floating freely in cytosol or attached to rough ER
no matter where ribosome ends up, translation ALWAYS starts in the cytosol b/c thats where mRNA comes out after the nucleus
- after that, if protein is determined to stay in the cytosol, it stays there but if it needs to go to the ER, Golgi, membrane, or outside, it gets a special tag and goes!
where does protein condensation/packaging occur?
Golgi apparatus
where does gene transcription occur?
transcription = DNA to mRNA
all transcription events occur in nucleus regardless of final destination of protein product
which of the following proteins is most likely to be the product of a proto-oncogene?
growth factor receptor
Redundancy” or “degeneration” of the genetic code occurs during which of the following steps of protein synthesis?
translation
mRNA to amino acids
where things can go wrong b/c in transcription, everything is exact replica of parent genome so its not wrong
Which of the following events does not occur during the process of mitosis?
replication of the genome
happens during S phase, which is BEFORE mitosis
why does fragmentation of nuclear envelope occur in mitosis?
nuclear envelope breaks down so that spindle fibers (made of microtubules) can reach & attach to chromosomes to pull them apart - mitotic spindle forms outside the nucleus in the cytoplasm
happens during prometaphase
Which of the following characteristics of a biological membrane is most influenced by its cholesterol content?
fluidity
The appearance of which of the following distinguishes eukaryotic cells from lower units of life?
nucleus
how do you determine what’s error and what’s correction when calculating gain?
correction is how has been fixed b/w before and after feedback mechanism
error is what’s left to be fixed
ex.
100 → 150 before control system
100 → 125 after control system
150-125= -25 (brought it down) → correction
150-125= +25 (what still needs to be fixed) → error
gain = correction/error
