Cytoplasm
Cell differentiation
The first zygotic cellular divisions produce cells called blastomeres as part of early embryos
inner cell mass, these give raise to all tissue types of the fetus.
Explanted to tissue culture cells of the inner cell mass called embryonic stem cells. Leads way
to a process called differentiation, which is where cells express sets of genes that mediate
specific cytoplasmic activities becoming a specialized tissue with functions.
,Plasma membrane
Cell membrane / plasmalemma that envelops eukaryotic cells consists of phospholipids,
cholesterol, and proteins with oligosaccharides chains covalently linked to phospholipids and
proteins. The functions include behaving as a selective barrier regulating the materials that pass
in and out of the cell and facilitate the transport of specific molecules. One important role of the
cell membrane is to keep the constant ion content of cytoplasm which differs from extracellular
fluid.
The membrane proteins also perform a number of specific recognition and signaling functions.
Between the interior of the cell and extracellular macromolecules there lies the continuum. The
inter-grin is a protein that is linked to both the cytoskeleton and ECM components and allows
continuous exchange of influences in both directions between cytoplasm and ECM.
Membranes range from 7.5 to 10 nm in thickness and are visible in electron microscope.
Membrane phospholipids are amphipathic, consisting of two non-polar (hydrophobic) long chain
fatty acids linked to a charged polar that bears a phosphate group. Most stable when organized
into a bilayer with hydrophobic fatty acid chains located in the middle region away from water
and hydrophilic polar heads facing the water.
Some of the layer's lipids are known as glycolipids, including the oligosaccharide chains that
extend outward from the cell surface and contribute to a delicate cell surface coating called the
gkycocalyx.
, Proteins are major constituents of membranes (~50%). Integral proteins are incorporated
directly within the lipid bilayer, whereas peripheral proteins are bound to one of the two
membranes' surface, mostly cytoplasmic side.
Transmembrane proteins and membrane transport
Plasma membrane is a site where materials are exchanged between a cell and its environment.
Most small molecules cross the membrane by these following methods:
● diffusion- transport small, non polar molecules directly through the lipid bilayer.
Lipophilic (fat -soluble) molecules diffuse through membranes readily, water very slowly
● Channels - multipass proteins forming transmembrane pores through which ions or
small molecules pass selectively. Cells open and close for some ions. Water molecules
cross the plasma membrane through proteins called aquaporins
● Carrier - transmembrane proteins that bind small molecules and translocate them
across the membrane via conformational changes
Membrane pumps are enzymes engaged in active transport, utilizing energy from the hydrolysis
of adenosine triphosphate (ATP) to move ions and other solutes across membranes against
often steep concentration gradients. Since they consume ATP pumps they are referred to as
ATPases.
Cell differentiation
The first zygotic cellular divisions produce cells called blastomeres as part of early embryos
inner cell mass, these give raise to all tissue types of the fetus.
Explanted to tissue culture cells of the inner cell mass called embryonic stem cells. Leads way
to a process called differentiation, which is where cells express sets of genes that mediate
specific cytoplasmic activities becoming a specialized tissue with functions.
,Plasma membrane
Cell membrane / plasmalemma that envelops eukaryotic cells consists of phospholipids,
cholesterol, and proteins with oligosaccharides chains covalently linked to phospholipids and
proteins. The functions include behaving as a selective barrier regulating the materials that pass
in and out of the cell and facilitate the transport of specific molecules. One important role of the
cell membrane is to keep the constant ion content of cytoplasm which differs from extracellular
fluid.
The membrane proteins also perform a number of specific recognition and signaling functions.
Between the interior of the cell and extracellular macromolecules there lies the continuum. The
inter-grin is a protein that is linked to both the cytoskeleton and ECM components and allows
continuous exchange of influences in both directions between cytoplasm and ECM.
Membranes range from 7.5 to 10 nm in thickness and are visible in electron microscope.
Membrane phospholipids are amphipathic, consisting of two non-polar (hydrophobic) long chain
fatty acids linked to a charged polar that bears a phosphate group. Most stable when organized
into a bilayer with hydrophobic fatty acid chains located in the middle region away from water
and hydrophilic polar heads facing the water.
Some of the layer's lipids are known as glycolipids, including the oligosaccharide chains that
extend outward from the cell surface and contribute to a delicate cell surface coating called the
gkycocalyx.
, Proteins are major constituents of membranes (~50%). Integral proteins are incorporated
directly within the lipid bilayer, whereas peripheral proteins are bound to one of the two
membranes' surface, mostly cytoplasmic side.
Transmembrane proteins and membrane transport
Plasma membrane is a site where materials are exchanged between a cell and its environment.
Most small molecules cross the membrane by these following methods:
● diffusion- transport small, non polar molecules directly through the lipid bilayer.
Lipophilic (fat -soluble) molecules diffuse through membranes readily, water very slowly
● Channels - multipass proteins forming transmembrane pores through which ions or
small molecules pass selectively. Cells open and close for some ions. Water molecules
cross the plasma membrane through proteins called aquaporins
● Carrier - transmembrane proteins that bind small molecules and translocate them
across the membrane via conformational changes
Membrane pumps are enzymes engaged in active transport, utilizing energy from the hydrolysis
of adenosine triphosphate (ATP) to move ions and other solutes across membranes against
often steep concentration gradients. Since they consume ATP pumps they are referred to as
ATPases.
