CAS BI 105 Lecture Notes - Lecture 5: Ultimate Tensile Strength, Elastin, Integrin
14 Dec 2017
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MULTICELLULARITY
The Extracellular matrix is a network of proteins that is secreted form cells. It provides:
-support and helps organize cell — it allows cells to move or stain in place
-signals to cells to guide function and development
-strength and rigidity to tissues (cartilage, bone, skin)
The major proteins are called integrins, which are membrane anchoring proteins.
The proteins in ECM are either:
-adhesive proteins — such as fibronectin and lain. provide organization by sticking
components of the ECM together and cells to ECM.
-structural proteins — such as collagen (long braids of fibers, stretch marks), which gives the
tissues strength and elasticity.
Proteins of ECM:
-Firbonectin — connects cells to ECM, organizes components
-Laminin — connects cells to ECM, organizes components. Found in the top layers of skin
especially.
-Collagen — provides tensile strength in deep skin, organs, bones, cartilage. 25% of total
protein mass in our body is collagen and 75% of protein in the skin is collagen. Leather is
essentially dried collagen. How is collagen made? cells produce individual collagen fibers and
organize them in triple helices which form larger collagen fibers. Loss of collages is caused
by rapid growth of any body site (stretch marks during pregnancy).
-Elastin — forms elastic fibers for stretch and recoil. It is found in skin, some cartilage and
blood vessels. When subjected to a stretching force, the elastin proteins elongate but remain
attached to each other via crosslinks. Elastin is especially important anywhere that is subject
to frequent stretch, such as arteries. Loss of elastin is sped up by toxins and UV damage
(loss of elastin create wrinkles).
ECM also contains polysaccharides called proteoglycans which are repeated disaccharide units
attached to a central protein. These weave together and bind water, creating a gel that cushions
cells and organs.
Cells can attach to each other and the ECM through anchoring junctions which are divided into:
-tights junctions — tight like a zip thereby preventing material from leaking between the cells.
They are made by membrane proteins.
-desmosomes — form pores across two membranes
-gap junctions — a small gap occurs between the plasma membranes of cells connected by
these junctions
-Adhering junctions — connect cells to ECM through integrins (like buttons)
-integrins are a group of cell - surface receptor proteins that create connections between
cells and the ECM. They are composed of two nonidentical subunits which promote a
strong association between the cytoskeleton and the ECM.
A Tissue is a group of cells having similar function. Humans have 200 cell types and 4 tissue
types. All organs are comprised of 1, 2, 3 or 4 tissue types and they are:
1. Epithelial — covers everything (skin)
2. Connective — joins things (like muscle to bone, or skin to deeper structures) and supports
them.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The extracellular matrix is a network of proteins that is secreted form cells. Support and helps organize cell it allows cells to move or stain in place. Signals to cells to guide function and development. Strength and rigidity to tissues (cartilage, bone, skin) The major proteins are called integrins, which are membrane anchoring proteins. Adhesive proteins such as bronectin and lain. provide organization by sticking components of the ecm together and cells to ecm. Structural proteins such as collagen (long braids of bers, stretch marks), which gives the tissues strength and elasticity. Firbonectin connects cells to ecm, organizes components. Laminin connects cells to ecm, organizes components. Found in the top layers of skin especially. Collagen provides tensile strength in deep skin, organs, bones, cartilage. 25% of total protein mass in our body is collagen and 75% of protein in the skin is collagen.
