CELL & MOLECULAR BIOLOGY (BIOL
300) ACTUAL EXAM 4 NOTES TO PASS YOUR
EXAM (2025-2026) VIRGINIA
COMMONWEALTH UNIVERSITY
,Exam 4
Part 1: Cell signaling
A. Cells must receive and adapt to signals from their environment
a. Cells must “communicate” their needs
i. Important signaling molecule is epinephrine. (adrenaline)
1. Flight or fight
2. One-way cells communicate
b. Cells receive signals and convert them to a cellular response similar to a cell
phone
i. Uses receptor proteins
1. extracellular signals in and intracellular signaling out
2. Like a cell phone
a. Radio signals in and sound out
B. Signaling Cascades
a.
i. Controls everything that we do
ii. Think relay race- cascade event
iii. Very important diagram
a. Cells can receive signals over different distances
i. 4 major groups
1. Endocrine
a. Long distance signaling
b. Produces hormones
c. In bloodstream and gets everywhere
, 2. Paracrine
a. Local signaling
i. Stays in same tissue/organ
b. Not in blood stream
3. Synaptic
a. Uses neurons
b. Neurotransmitters talks to postsynaptic cell
c. Fastest signaling
4. Contact-dependent
a. Cells must touch
b. Membrane-bound signal molecules
c. Signals affect cell fate (differentiation) during development
i. Example
1. Unspecified epithelial cells -> cell
specialization and lateral inhibition ->
Membrane-bound inhibitory signal protein
(delta), receptor proteins (notch), nerve cell
developing from epithelial cell, Inhibited
epithelial cell
b. Examples of hormone signaling molecules
i.
ii. Story: all signalling are molecules and are hormones , action is
everywhere, all in the bloodstream. Estrogen and testosterone can affect
the skeleton, skin, hair, growth, ect.
c. Examples of paracrine signaling molecules
, i.
C. One signaling molecule can induce different responses on different target cells
a. Affects different response Because it talks to a bunch of different cell types
b. Acetylcholine is the signaling molecule that talks to many different cell types
(many cell signaling)
i. Has many jobs
ii. Affects: heart pace(decreases heart rate) , salivary gland(secretion), and
skeletal muscle cells (contraction)
D. Cell Signaling is complex
a. Survive
i. Cells need to talk to other cells to survive
ii. Cancer cells can survive without cell signaling or talking to other cells
b. Grow and divide
c. Differentiate
d. Die -> apoptotic cell
E. One signal can have multiple response times
a. Phosphorylation
i. Turning proteins on and off
ii. Fast (<sec to min)
b. Transcription and translation
i. Making more proteins
ii. Slow (min- hrs)
F. Signals can be received on the cell membrane or by intracellular receptors
a. Intracellular receptors
i. 4th class receptor
ii. Bind to DNA and control how we express our genes
b. Cell surface receptors
i. To go through membrane need to small and hydrophobic
300) ACTUAL EXAM 4 NOTES TO PASS YOUR
EXAM (2025-2026) VIRGINIA
COMMONWEALTH UNIVERSITY
,Exam 4
Part 1: Cell signaling
A. Cells must receive and adapt to signals from their environment
a. Cells must “communicate” their needs
i. Important signaling molecule is epinephrine. (adrenaline)
1. Flight or fight
2. One-way cells communicate
b. Cells receive signals and convert them to a cellular response similar to a cell
phone
i. Uses receptor proteins
1. extracellular signals in and intracellular signaling out
2. Like a cell phone
a. Radio signals in and sound out
B. Signaling Cascades
a.
i. Controls everything that we do
ii. Think relay race- cascade event
iii. Very important diagram
a. Cells can receive signals over different distances
i. 4 major groups
1. Endocrine
a. Long distance signaling
b. Produces hormones
c. In bloodstream and gets everywhere
, 2. Paracrine
a. Local signaling
i. Stays in same tissue/organ
b. Not in blood stream
3. Synaptic
a. Uses neurons
b. Neurotransmitters talks to postsynaptic cell
c. Fastest signaling
4. Contact-dependent
a. Cells must touch
b. Membrane-bound signal molecules
c. Signals affect cell fate (differentiation) during development
i. Example
1. Unspecified epithelial cells -> cell
specialization and lateral inhibition ->
Membrane-bound inhibitory signal protein
(delta), receptor proteins (notch), nerve cell
developing from epithelial cell, Inhibited
epithelial cell
b. Examples of hormone signaling molecules
i.
ii. Story: all signalling are molecules and are hormones , action is
everywhere, all in the bloodstream. Estrogen and testosterone can affect
the skeleton, skin, hair, growth, ect.
c. Examples of paracrine signaling molecules
, i.
C. One signaling molecule can induce different responses on different target cells
a. Affects different response Because it talks to a bunch of different cell types
b. Acetylcholine is the signaling molecule that talks to many different cell types
(many cell signaling)
i. Has many jobs
ii. Affects: heart pace(decreases heart rate) , salivary gland(secretion), and
skeletal muscle cells (contraction)
D. Cell Signaling is complex
a. Survive
i. Cells need to talk to other cells to survive
ii. Cancer cells can survive without cell signaling or talking to other cells
b. Grow and divide
c. Differentiate
d. Die -> apoptotic cell
E. One signal can have multiple response times
a. Phosphorylation
i. Turning proteins on and off
ii. Fast (<sec to min)
b. Transcription and translation
i. Making more proteins
ii. Slow (min- hrs)
F. Signals can be received on the cell membrane or by intracellular receptors
a. Intracellular receptors
i. 4th class receptor
ii. Bind to DNA and control how we express our genes
b. Cell surface receptors
i. To go through membrane need to small and hydrophobic
