propels substances along surface of cell. found in respiratory tract
what is flagellum?
propels entire cell. only cells in body w/flagella r SPERM
what r the 3 types of membrane junctions btwn cells?
tight junctions, desmosomes, and gap junctions
what is a tight junction?
keeps cells close together so nothing can pass in btwn. proteins fuse to keep substance from passing. Ex btwn cells lining digestive tract.
what is a desmosome?
adjacent cells r held together by linking proteins to keep cells from coming apart. found on cells with pull/tension/force. Ex. heart muscle, skin
what is a gap junction?
cells connected by cylindrical proteins. allows comm btwn cells. Ex. heart muscle 9allows flow of ions btwn cells)
describe the cytoplasm.
material btwn plasma and nuclear membrane. contains cytosol (intracellular fluid) and organelles
what r the organelles of the cytoplasm?
cytoskeleton, ribosomes, ER, Golgi apparatus, lysosomes, mitochondria
what is the cytoskeleton?
network of proteins that provide strength & structural support. composed of filaments
what r the 3 types of filaments the cytoskeleton is made up of?
microfilaments aka actin filaments, intermediate filaments, and microtubules
what r ribosome?
responsible for protein synthesis
2 types: free and fixed
what is the ER?
endoplasmic reticulum - a netwk of intracellular membranes. a site for synthesis of proteins, lipids, and carbs.
diff btwn smooth and rough ER?
smooth - no ribosomes; lipid and carb synthesis
rough - fixed ribosomes on outer surface; protein synthesis
what is purpose of Golgi Apparatus?
packages & modifies molecules from ER for secretion (exocytosis), incorporation into the plasma membrane, or use w/i the cell (lysosome)
vesicles containing digestive enzymes
perform cleanup and recycling function - fuse w/damaged organelles or endocytic vesicles to digest contents and release nutrients
what is the mitochondria?
responsible for energy (ATP) production. process of energy production = aerobic respiration
describe the nuclear envelope
double membrane layer. surrounds nucleus. has nuclear pores
what is the purpose of nuclear pores?
allows communication btwn nucleus and cytoplasm
what is chromatin?
the uncondensed form of a chromosome, which holds DNA
what is a chromosome?
the condensed form of a chromatin
what happens in nucleoli?
ribosome assembly. mature ribosomes move to cytoplasm thru nuclear pores
what is the purpose of cell division?
req'd for growth of organism and replacement of worn-out cells
what are the two major steps of cell division?
interphase and mitosis
Interphase is composed of what smaller phase?
G1, G0, S, and G2
describe G1 phase
period of cell growth
describe G0 phase
non-dividing phase. cells may exit cell cycle.
describe S phase
DNA replication (double helix uncoils, each strand serves as template 4synthesis of complementary strand, each new double helix has 1 old &1 new strand)
describe G2 phase
growth and final preparation for mitosis and cell division
what is mitosis?
chromatin condenses into chromosomes; duplicated DNA molecules condense into pair of sister chromatids; nuclear membrane breaks down; spindle fibers form
chromosomes align at equator
sister chromatids separate and move to opposite poles
"reversal" of prophase (spindle disappears, nuclear envelope reforms, chromosomes decondense into chromatin)
cytoplasmic division by contractile ring @ cleavage furrow
what r the 2 phases of gene expression and protein synthesis
transcription and translation
what is gene expression and protein synthesis?
process where info in DNA (genes) is use to direct protein synthesis
what is transcription?
DNA -> mRNA; occurs in nucleus. one strand of DNA (template strand) is used to guide synthesis of mRNA
pre-mRNA is synthesiszed by which enzyme?
what is RNA processing?
pre-mRNA is processed to form a mature mRNA
where is mRNA exported from/to in transcription?
from nucleus to cytoplasm
mRNA -> protein; occurs @ribosome (in cytoplasm). 3 stages
what is a codon?
3 bases in mRNA which specify an amino acid => genetic code
what r the 3 stages of translation?
initiation, elongation, and termination
describe stage 1 of translation
initiaion: ribosome assembles on mRNA. tRNA carrying 1st aa binds mRNA/ribsome complex @P-site. binding occurs btwn the codon in the mRNA & the anticodon in the tRNA
what r the 3 sites of the ribsome?
E, P, and A
describe 1st part of stage 2 of translation
elongation: tRNA carrying next aa arrives @adjacent binding site in ribosome (A site)aa's @ P & A sites joined by peptide bond thru dehydration synthesis.
describe 2nd part of stage 2 of translation
tRNA in P site releases its aa. ribosome moves down mRNA by 3 bases (tRNA in Psite moves into Esite, & then exits ribosome; new codon occupies Asite & is ready 2get next tRNA). steps rpt til stop codon in mRNA
summary of mvmt of tRNAs during stage 2 of translation