lOMoARcPSD|14985576
Week 0
Why are smaller cells are more effective than larger cells?
- Larger cell needs to eat more, needs more energy, produces more waste
- All these are limiting factors on how quickly a cell can get things in and out
- Cells are small because it is better to have many cells taking up the same volume than 1
big cell that requires more food, energy etc.
Discuss how a signal can lead to both short- and long-term responses
Signaling:
- Receptor activation(signal binds to receptor and activates it)→ signal transduction(signal
transmitted to interior of cell by transduction pathway, usually a chain reaction) →
response(ok nothing crazy) → termination(response terminated so new signals can be
received)
- In multicellular organisms, when the two cells are far apart, the signaling molecule is
transported by the circulatory system. When they are close, the signaling molecule
simply moves by diffusion. When they are close together, the signaling molecule is not
released from the signaling cell at all.
- Endocrine signaling- signaling by means of molecules that travel through the
bloodstream
- FUN FACT: The endocrine system is a chemical messenger system consisting of
hormones, the group of glands of an organism that carry those hormones directly into
the circulatory system to be carried towards distant target organs, and the feedback
loops of homeostasis that the hormones drive
- Paracrine signaling- the signaling molecule can simply move by diffusion between the
two cells involved, does not require circulatory system: the signal is usually a small,
water-soluble molecule such as a growth factor.
- Other short distance responses: neurotransmitters, neurons/muscle cells
- Growth factors, and histamine are examples of paracrine chemical agents released in small
amounts that act locally on neighboring cells.
Describe the mechanism of action for a receptor tyrosine kinase pathway
- A signal molecule binds to the extracellular portion of two receptors, causing the
receptors to bind with each other
- This partnering of two similar or identical molecules is called dimerization. Dimerization
activates the cytoplasmic kinase domains of the paired receptors, causing them to
phosphorylate each other at multiple sites on their cytoplasmic tails
- The addition of these phosphate groups provides places on the receptor where other
proteins bind and become active.
Receptor kinases
bind bind signaling
molecules,
dimerize,
phosphorylate each
Downloaded by Clare Kemmy ()
, lOMoARcPSD|14985576
o and activate intracellular signal molecules.
Define the role of kinases and phosphatases in cell
signaling pathways
- A kinase is an enzyme that catalyzes the transfer
of a phosphate group from ATP to a substrate.
- A kinase transfers a phosphate group from ATP to
a protein, typically activating the
protein(phosphorylation).
- A phosphatase removes a phosphate group from
a protein, typically deactivating the
protein(dephosphorylation). -
- PHOSPHORYLATION DOES NOT ALWAYS
MEAN ACTIVATION.
Week 1
Distinguish the potential for differentiation of
totipotent, pluripotent, and multipotent stem cells
- Totipotent- A fertilized egg (ZYGOTE) that can
give rise to a complete organism
- The fertilized egg is totipotent because it can
differentiate into both the inner cell mass and
supporting membranes, and eventually into an
entire organism.
- The cells of the inner cell mass(embryonic stem cells) are pluripotent because they can
give rise to any of the three germ layers, and therefore to any cell of the body.They
cannot on their own give rise to an entire organism.
- Cells further along in differentiation are multipotent; these cells can form a limited
number of types of specialized cell; cells in the germ layer bc they can only give rise to
cells in the specified germ layer
- BASIC RUNDOWN OF THE 3:
● totipotent can form ALL CELL TYPES in an organism (zygote)
● Pluripotent can generate ALL DIFFERENT TYPES of cells in the
body(embryonic stem cells)
● multipotent can produce some or all of the MATURE CELL TYPES within a
particular tissue (neural progenitor cells)
Describe the different types of cell-cell junctions
- Cell junctions- A complex of proteins in the plasma membrane where a cell makes
contact with another cell or the extracellular matrix.
- The skin is a community of cells organized into two layers—the epidermis and
dermis—that together provide protection for the underlying tissues of the body.
Downloaded by Clare Kemmy ()
, lOMoARcPSD|14985576
Define microtubule, microfilament, and intermediate filament.
- provide internal support for cells
- Microtubules and microfilaments enable the movement of substances within cells as well
as changes in cell shape.
- Microtubule- A hollow, tubelike polymer of tubulin dimers that helps make up the
cytoskeleton.
- Microfilament- A helical polymer of actin monomers, present in various locations in the
cytoplasm, that helps make up the cytoskeleton.
- Intermediate filament- ONLY ANIMAL CELLS HAVE THIS: A polymer of proteins,
which vary according to cell type, that combine to form strong, cable-like filaments that
provide animal cells with mechanical strength.
- In addition to providing structural support, microtubules and microfilaments enable the
movement of substances within cells as well as changes in cell shape.
Downloaded by Clare Kemmy ()
, lOMoARcPSD|14985576
Explain how motor proteins actively move material around the cell
- Plus ends of microtubules and microfilaments assemble quickly, while the minus end
assembles slower and this is due to the concentration of of tubulin and actin in that
region of the cell.
- Dynamic instability:The plus ends of microtubules undergo cycles of rapid disassembly
followed by slow assembly.
- Microtubules and microfilaments have some capacity to lengthen and shorten by
polymerization and depolymerization BUT motor proteins amplify this!
- Kinesin transports cargo toward the plus end of microtubules, while dynein carries its
load away from the plasma membrane toward the minus end. Both powered by ATP.
Explain how cell-cell junctions and the extracellular matrix (ECM) contribute to cells’
ability to form tissues and organs
- Cell adhesion molecule- A cell-surface protein that attaches cells to one another and to
the extracellular matrix.
- Cadherins are calcium-dependent adherence proteins, that connect cells to other cells.
- Integrins are transmembrane proteins that connect cells to the extracellular matrix.
- Adherens junction- actin microfilaments are attached to the plasma membrane by
cadherins. Cell communication through the cadherins in the adherens junction of one
cell which attach to the cadherins in the adherens junctions of adjacent cells.
- Desmosomes- A button-like point of adhesion that holds the plasma membranes of
adjacent cells together, cadherins are the primary cell adhesion molecules.
- Hemidesmosome- allows for attachment of epithelial cells to the extracellular matrix,
integrins are the primary cell adhesion molecules
- Tight junctions- junctional complex that establishes a seal between cells so that the
only way a substance can travel from one side of a sheet of epithelial cells to the other is
by moving through the cells by a cellular transport mechanism.
- Gap junction- A type of connection between the plasma membranes of adjacent animal
cells that permits materials to pass directly from the cytoplasm of one cell to the
cytoplasm of another.
- Plasmodesmata- Connections between the plasma membranes of adjacent plant cells
that permit molecules to pass directly from the cytoplasm of one cell to the cytoplasm of
another.
Downloaded by Clare Kemmy ()
Week 0
Why are smaller cells are more effective than larger cells?
- Larger cell needs to eat more, needs more energy, produces more waste
- All these are limiting factors on how quickly a cell can get things in and out
- Cells are small because it is better to have many cells taking up the same volume than 1
big cell that requires more food, energy etc.
Discuss how a signal can lead to both short- and long-term responses
Signaling:
- Receptor activation(signal binds to receptor and activates it)→ signal transduction(signal
transmitted to interior of cell by transduction pathway, usually a chain reaction) →
response(ok nothing crazy) → termination(response terminated so new signals can be
received)
- In multicellular organisms, when the two cells are far apart, the signaling molecule is
transported by the circulatory system. When they are close, the signaling molecule
simply moves by diffusion. When they are close together, the signaling molecule is not
released from the signaling cell at all.
- Endocrine signaling- signaling by means of molecules that travel through the
bloodstream
- FUN FACT: The endocrine system is a chemical messenger system consisting of
hormones, the group of glands of an organism that carry those hormones directly into
the circulatory system to be carried towards distant target organs, and the feedback
loops of homeostasis that the hormones drive
- Paracrine signaling- the signaling molecule can simply move by diffusion between the
two cells involved, does not require circulatory system: the signal is usually a small,
water-soluble molecule such as a growth factor.
- Other short distance responses: neurotransmitters, neurons/muscle cells
- Growth factors, and histamine are examples of paracrine chemical agents released in small
amounts that act locally on neighboring cells.
Describe the mechanism of action for a receptor tyrosine kinase pathway
- A signal molecule binds to the extracellular portion of two receptors, causing the
receptors to bind with each other
- This partnering of two similar or identical molecules is called dimerization. Dimerization
activates the cytoplasmic kinase domains of the paired receptors, causing them to
phosphorylate each other at multiple sites on their cytoplasmic tails
- The addition of these phosphate groups provides places on the receptor where other
proteins bind and become active.
Receptor kinases
bind bind signaling
molecules,
dimerize,
phosphorylate each
Downloaded by Clare Kemmy ()
, lOMoARcPSD|14985576
o and activate intracellular signal molecules.
Define the role of kinases and phosphatases in cell
signaling pathways
- A kinase is an enzyme that catalyzes the transfer
of a phosphate group from ATP to a substrate.
- A kinase transfers a phosphate group from ATP to
a protein, typically activating the
protein(phosphorylation).
- A phosphatase removes a phosphate group from
a protein, typically deactivating the
protein(dephosphorylation). -
- PHOSPHORYLATION DOES NOT ALWAYS
MEAN ACTIVATION.
Week 1
Distinguish the potential for differentiation of
totipotent, pluripotent, and multipotent stem cells
- Totipotent- A fertilized egg (ZYGOTE) that can
give rise to a complete organism
- The fertilized egg is totipotent because it can
differentiate into both the inner cell mass and
supporting membranes, and eventually into an
entire organism.
- The cells of the inner cell mass(embryonic stem cells) are pluripotent because they can
give rise to any of the three germ layers, and therefore to any cell of the body.They
cannot on their own give rise to an entire organism.
- Cells further along in differentiation are multipotent; these cells can form a limited
number of types of specialized cell; cells in the germ layer bc they can only give rise to
cells in the specified germ layer
- BASIC RUNDOWN OF THE 3:
● totipotent can form ALL CELL TYPES in an organism (zygote)
● Pluripotent can generate ALL DIFFERENT TYPES of cells in the
body(embryonic stem cells)
● multipotent can produce some or all of the MATURE CELL TYPES within a
particular tissue (neural progenitor cells)
Describe the different types of cell-cell junctions
- Cell junctions- A complex of proteins in the plasma membrane where a cell makes
contact with another cell or the extracellular matrix.
- The skin is a community of cells organized into two layers—the epidermis and
dermis—that together provide protection for the underlying tissues of the body.
Downloaded by Clare Kemmy ()
, lOMoARcPSD|14985576
Define microtubule, microfilament, and intermediate filament.
- provide internal support for cells
- Microtubules and microfilaments enable the movement of substances within cells as well
as changes in cell shape.
- Microtubule- A hollow, tubelike polymer of tubulin dimers that helps make up the
cytoskeleton.
- Microfilament- A helical polymer of actin monomers, present in various locations in the
cytoplasm, that helps make up the cytoskeleton.
- Intermediate filament- ONLY ANIMAL CELLS HAVE THIS: A polymer of proteins,
which vary according to cell type, that combine to form strong, cable-like filaments that
provide animal cells with mechanical strength.
- In addition to providing structural support, microtubules and microfilaments enable the
movement of substances within cells as well as changes in cell shape.
Downloaded by Clare Kemmy ()
, lOMoARcPSD|14985576
Explain how motor proteins actively move material around the cell
- Plus ends of microtubules and microfilaments assemble quickly, while the minus end
assembles slower and this is due to the concentration of of tubulin and actin in that
region of the cell.
- Dynamic instability:The plus ends of microtubules undergo cycles of rapid disassembly
followed by slow assembly.
- Microtubules and microfilaments have some capacity to lengthen and shorten by
polymerization and depolymerization BUT motor proteins amplify this!
- Kinesin transports cargo toward the plus end of microtubules, while dynein carries its
load away from the plasma membrane toward the minus end. Both powered by ATP.
Explain how cell-cell junctions and the extracellular matrix (ECM) contribute to cells’
ability to form tissues and organs
- Cell adhesion molecule- A cell-surface protein that attaches cells to one another and to
the extracellular matrix.
- Cadherins are calcium-dependent adherence proteins, that connect cells to other cells.
- Integrins are transmembrane proteins that connect cells to the extracellular matrix.
- Adherens junction- actin microfilaments are attached to the plasma membrane by
cadherins. Cell communication through the cadherins in the adherens junction of one
cell which attach to the cadherins in the adherens junctions of adjacent cells.
- Desmosomes- A button-like point of adhesion that holds the plasma membranes of
adjacent cells together, cadherins are the primary cell adhesion molecules.
- Hemidesmosome- allows for attachment of epithelial cells to the extracellular matrix,
integrins are the primary cell adhesion molecules
- Tight junctions- junctional complex that establishes a seal between cells so that the
only way a substance can travel from one side of a sheet of epithelial cells to the other is
by moving through the cells by a cellular transport mechanism.
- Gap junction- A type of connection between the plasma membranes of adjacent animal
cells that permits materials to pass directly from the cytoplasm of one cell to the
cytoplasm of another.
- Plasmodesmata- Connections between the plasma membranes of adjacent plant cells
that permit molecules to pass directly from the cytoplasm of one cell to the cytoplasm of
another.
Downloaded by Clare Kemmy ()
