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Cell&Tissue Physiology, Cell Membrane Potential - Coggle Diagram
Cell&Tissue Physiology
Epitheliel tissue
This is the tissue that is on the external surface of human bodies, lines the cavities (lumen) as well as lines organs.
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Epithelial tissue protects the body (has protective boundaries) but also allows for easy diffusion in some cases (with fewer layers)
Every epithelial cells has transmembrane proteins that faciliate adjoining with adjacent cells, called cell junctions
Tight junction -- located near the apical membrane on the lateral membrane on two cells, this transmembrane protein prevents leaks through the extracellular matrix of ions and molecules.
Gap junction -- located on the lateral membrane (no height in particular), this transmembrane protein channel connects the cytoplasms of the two adjacent cells to allow for the movement of small ions and and molecules across. One gap junction is made of 2 connexons, which are made of connexins.
Anchoring junctions -- these are junctions that connect teh cell and anchor it to the extracellular matrix, or to the adjacent cell
Cell to cell
desmosomes
has a plaque, which attaches to the intermediate filaments found in the cytoskeleton of the cell. Transmembrane proteins extend and overlap with the same subunit from the other cell
adherens
has a plaque, which attaches to the actin filaments found in the cytoskeleton of the cell. Transmembrane proteins extend and overlap with the same subunit from the other cell
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Epithelial cells produce basal lamina, which is made up of grlycoproteins and collagen, in the basal membrane area. The connective tissue below secretes reticular lamina, which together for the basement membrane. This seperates the tissues as well as holds them together.
Different tissues are made up of different types of cells, and have different structures for their different functions. The following are the 4 major types of tissue in vertebrates
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Connective tissue
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Types
Dense connective tissue
This has a high amount of collagen in its extracellular matrix giving it high tensile strength (resistant to tearing). Has all resident cells, with fibroblasts being the most abundant. Tendons and ligments are made up of this.
Cartilage
Its less dense than bone, and more flexible, which gives more bouyancy and movement in water.
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Has no reticular fibers, some elastic fibers and predominantly collagen fibers.
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Common in sharkes, skates and sturgeon
Cells called chondrocytes produce a polysaccharide called chondroitin sulfate which combined with gournd substance proteins to form proteoglycans.
Bone
ECM
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Protein fibers
Collagen is found in the lamellae, also hardened by using intermittened hydroxyapitite. Reticular fibers are found the marrow tissue.
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Loose connective tissue
This is the most abundant connective tissue in vertebrates, it holds the organs in place
Primary protein fiber is collagen, and has all resident cells but fibroblasts are in most abundance
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Blood
has most of the resident cells (except adipocytes), the ground substance is plasma, and there are no protein fibers
Other cells
Leukocytes (white blood cells, have a nucleus)
Erythrocytes
Red blood cells, do not have a nucleus
Platelets
Fragments of cells, no nucleus
Muscle tissue
Responds to stimuli trhough movement, which is contraction (unique to animals), and done through the overlap of myosin and actin filaments.
Types
Skeletal
Striated, long cylindrical cells that are not branched, are voluntary, and are mutlinucleated.
Cardiac
Straited, intercalated discs that are uninucleated and involuntary. Branched
Smooth
Not striated or intercalated discs, fusiform (spindle shaped), and involuntary
Nervous tissue
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Glial cells (glia) support the neurons, with nutrition, upkeep/application and mylination
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Cell Membrane Potential
The Fluid Mosiac Model
Proteins, carbohydrates float in a sea of phospholipids in the cell membrane. The phospholipids are fluid
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Sphingolipid
Ceramide
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Sphingosine is an 18carbon with an unsaturated hydrocarbon. It serves as the backbone instead of glycerol
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Glycosphingolipid
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Ganglioside
Ceramide + 3 sugars, one being salic acid
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Membrane fluidity
Fluidity is the movement of phospholipids laterally, rotationally, or flipping (less common)
Need fluidity for the membrane to: Proteins need to move so they can meet and interact with other proteins/molecules, allowing things like cell signaling and membrane remodeling to occur.
Too much fluidity is bad though, it allows for leakages and thus not tight security of what gets in and out
Increased fluidity:
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Shorter fatty acid tails of phospholipids (so that there are less hydrophobic interactions (Van Der Waals interactions)), and so its easier to detach, more fluid
Unsaturated fatty acid tails (these have kinks, prevent tighter packing, and thus are more fluid (again less interactions fro less tight packing)
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Fluidity buffer
Cholesterol
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Increasing cholesterol decreases permability -- less permeability.
↑ Cholesterol → ↓ membrane permeability, because cholesterol fills gaps between phospholipids, making it harder for small molecules/ions to pass through the bilayer.
The shortcomings of the fluid mosaic model is that it describes surface diversity but not spatial diversity in the plasma membrane
Lipid rafts form, and contain longer chained phospholipids. They are wider, and because they have longer chained phospholipids they are less fluid than the surrounding
The longer width allows for long transmembrane proteins to be present (can form more interactions -- hydrophobic- -- with the chains beside and thus are more stable structurally)
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roteins that take up cytoskeleton for strutural reasons are also part of the lipid raft (and do not move)
surroundings can move and push lipid rafts towards eahcother and they can merge, or split apart.
Membrane proteins
The plasma membrane holds transmembrane and peripheral proteins, which essentially determine the membrane's function
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The fluid mosaic model tells us about the proteins and other particles in the membrane, and while the phosphlipids are most abundant and give the structural integrity: proteins give the function of the membrane
Membrane asymmetry
When teh monolayers of the membrane are not similar to eachother, and serve different functions and purpose.
This is seen in the plasma membrane, but not in the endoplasmic reticulum
This is high phosphotadylserine and phosphotadylcholine on the inner membrane, cauinging a negative charge and charge difference.
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