Unit 4 : Cell Communication & Cell Cycle Flashcards
Animal Cells communicate by:
Direct contact (gap junctions)
Secreting local regulators (growth
factors, neurotransmitters)
Long distance (hormones)
3 types of cell signaling
Reception
Transduction
Response
Reception
Detection of a signal molecule (ligand) coming from outside the cell
Transduction
Convert signal to a form that can bring about a cellular response
Response
Specific cellular response to the signal molecule
Reception (Full concept)
Binding between signal molecule (ligand) + receptor is highly
specific.
Types of Receptors: Plasma membrane receptor & Intracellular receptors
Ligand binds to receptor protein→protein changes SHAPE →initiates transduction signal
Plasma Membrane Receptor
water-soluble ligands
Intracellular receptors
(cytoplasm, nucleus)
small or hydrophobic ligand molecules
Eg. testosterone or nitric oxide (NO)
Transduction (full concept)
Cascades, Protein kinase, Phosphorylation cascade
Cascades…
of molecular interactions relay signals from receptors → target molecules
Protein kinase
enzyme that phosphorylates and
activates proteins at next level
Phosphorylation cascade
enhance and amplify
signal
Second Messengers
small, nonprotein molecules/ions that can relay signal inside cell
Ex: cyclic AMP (cAMP), calcium
ions (Ca2+), inositol triphosphate
(IP3)
cAMP
cAMP = cyclic adenosine monophosphate
GPCR → adenylyl cyclase (convert ATP → cAMP) → activate protein kinase A
Response (full concept)
Regulate protein synthesis by turning on/off genes in nucleus (gene expression)
Regulate activity of proteins in cytoplasm
Signal Transduction Pathway
Problems/Defects
Diabetes
Cholera
Autoimmune disease
Cancer
Neurotoxins, poisons, pesticides
Drugs (anesthetics, antihistamines, blood pressure meds)
Cholera
Disease acquired by drinking contaminated water (w/human feces)
Bacteria (Vibrio cholerae) colonizes lining of small intestine and **produces toxin which modifies G-protein involved in regulating salt & water secretion
G protein stuck in active form → intestinal cells secrete salts, water
Infected person develops
profuse diarrhea and could die
from loss of water and salts
Viagra
Used as treatment for erectile dysfunction
Inhibits hydrolysis of cGMP → GMP
Prolongs signal to relax smooth muscle in artery walls; increase blood flow to penis
Apoptosis
CELL SUICIDE
Cell is dismantled and digested
Triggered by signals that activate cascade of “suicide” proteins (caspase)
WHY? Protect neighboring cells from damage
Animal development & maintenance
May be involved in some diseases (Parkinson’s, Alzheimer’s)
Cell Cycle
life of a cell from its formation until it
divides into 2 cells
Functions of Cell Division
Reproduction, Growth &
Tissue Repair
Genome
all of a cell’s genetic info (DNA)
Prokaryote
single, circular chromosome
Eukaryote
More than one linear chromosomes
Eg. Human:46 chromosomes, mouse: 40, fruit fly: 8
Each chromosome must be duplicated (replicated) before cell division
Duplicated chromosome = 2 sister chromatids attached by a centromere
Somatic Cells
Body cells
Diploid (2n): 2 of each type of
chromosome
Divide by mitosis
Humans: 2n = 46
Gametes
Sex cells (sperm/egg)
Haploid (n): 1 of each type of
chromosome
Divide by meiosis
Humans: n = 23
Phases of the Cell Cycle
The mitotic phase alternates with interphase: G1 → S → G2 → mitosis → cytokinesis
Interphase
(90%+ of cell cycle)