chapter 11-12: cell signaling Flashcards
1
Q
extracellular layer of molecules
A
- cross-linked network of long filaments of biomolecules embedded in a stiff surrounding material
- withstand tension
- withstand compression
- provide structure
2
Q
primary plant cell walls
A
- primary cell walls made of polysaccharide structures
- both strong cables and gelatinous substances
- strong cables made of cellulose - crosshatch network
- gelatinous substance - pectin - keep cell wall moist
- makes endo / exocytosis difficult
3
Q
expansins (plants)
A
- disrupt hydrogen bonds in primary cell wall to allow growth
4
Q
secondary cell wall (plants)
A
- made of waxes and lignin
- mature plants have these between plasma membrane and primary cell wall
- leaves = waxes (protect against losing gases + water)
- woody tissue = lignin (withstands gravity + wind)
5
Q
extracellular matrix (animals)
A
- network of protein polymers and saccharide + protein polymers
- can assemble into strong rope-like fibers (collagen) or gelatinous networks (proteoglycans)
6
Q
middle lamella
A
- made of gelatinous pectins and is continuous with the primary cell wall
- made of carbohydrates
- connects adjacent plant cells
7
Q
membrane proteins
A
- connect animal cells
- 3 main types (2 categories): anchoring or joining junctions & communicating junctions
8
Q
anchoring / joining junctions
A
- provide stability / flexibility (desmosomes)
- some make water tight seals (tight junctions)
9
Q
communicating junctions
A
- gap junctions
- continuous cytoplasm, rapid signaling, and coordination of cellular processes
10
Q
tight junctions
A
- water tight seals
- between skin cells
- membrane proteins bind to one another to form a tight junction
- do not want osmosis
11
Q
desmosomes
A
- form secure adhesion
- linking of cell membrane proteins, cytosolic anchoring proteins, and the cytoskeleton
- without these, a handshake could rip our skin cells apart
12
Q
gap junctions
A
- create continuous cytoplasm
- between cells of same tissue
- water, ion, and small molecules (amino acids and nucleotides) can pass freely down their concentration gradient
13
Q
plasmodesmata
A
- communication channels between cells through cell walls
- sends molecules back and forth
- form a continuous network of cytoplasm (the symplast)
- ions, water, small molecules can travel through
14
Q
antigens
A
- proteins or carbohydrates on surface of cell dependent on tissue and organism the cell comes from
- immune system cells can recognize foreign cells based on antigens using antibodies
15
Q
studying cell adhesion of proteins using antibodies
A
- isolate membrane proteins from cells
- create antibodies to specific proteins
- purify antibodies so only one type of antibody is present in test solution
- apply antibodies to cell cultures and observe results
16
Q
cell signaling
A
- ligand binds to receptor
- transduction
- response
17
Q
phosphorylation
A
a phosphate group is added by a protein kinase; protein changes shape and binding site is revealed
18
Q
phosphatases
A
remove phosphate groups from proteins
19
Q
allosteric sites can be modified by reversible covalent bonding of what molecule
A
phosphate
20
Q
components of a signal transduction pathway
A
- signal = ligand
- receptor = protein
- response to signal
- initiated by shape change of receptor - signal flips a molecular switch
- signal may be transduced and amplified by other cellular molecules
- ultimately causes some change in target cell
21
Q
receptor proteins
A
- highly specific for their ligands
- binding is reversible
- ligand not changed by binding
- receptor alternates between active and inactive conformations
22
Q
intracellular receptor
A
nonpolar signal can diffuse directly across the lipid bilayer of the cell membrane to encounter its receptor in the cytosol or nucleus
23
Q
transmembrane proteins
A
polar signal cannot diffuse through cell membrane so receptor is embedded into the membrane
24
Q
NLS tag is needed to…
A
enter nucleus, where it effects protein making
25
G-protein coupled receptors
- when signal binds to receptor, GEF adds GTP and activates G protein
- inactive form of G protein has GDP bound
- activated by exchange of GDP and GTP
- active G protein can move through cell membrane and activate protein
26
receptor tyrosine kinases
- kinase adds a phosphate
- change 3-D structure of proteins
- shape change can reveal a binding site so protein can then activate next protein in pathway
- receptor turned off by a phosphatase
27
signal transduction types
1. kinase cascades - add / remove phosphate
2. using secondary messengers - cleave off part of molecule; change molecule conformation
28
why is signaling amplified
- larger cellular response
- more molecules impacted
- multiple response can be elicited simultaneously
29
secondary messenger cAMP
- cAMP
- adenylyl cyclase transforms ATP into cAMP
- odorant molecules
- fight or flight response
30
secondary messenger PIP2
- DAG + IP3
- when activated, phospholipase C cleaves PIP, releasing the secondary messengers IP3 and DAG
31
DAG can initiate
exocytosis
32
multicomponent signal transduction pathways provide:
1. opportunities for feedback
2. signal amplification
3. interactions inside one cell between multiple signals and signal pathways
33
regulation of signal transduction
- cytoplasmic concentration of Ca2+; increase is transient
- protein kinases, G proteins, cAMP regulated by enzymes
- balance between enzymes that activate transducers and enzymes that inactivate them determines the cellular response to a signal
