The Cell Membrane PDF

8/27/24, 8:21 PM Platform | Study Fetch The Cell Membrane (00:00:13 - 00:00:31)The cell membrane is a layer that separates the cell interior from the external environment. It has many important functions including: Regulatin...

8/27/24, 8:21 PM Platform | Study Fetch The Cell Membrane (00:00:13 - 00:00:31)The cell membrane is a layer that separates the cell interior from the external environment. It has many important functions including: Regulating what substances get in or out of the cell Protecting the cell from the external environment Selective Permeability of the Cell Membrane (00:00:31 - 00:00:44) The cell membrane has selective permeability This means it allows certain substances to pass through while blocking others Composition of the Cell Membrane (00:00:44 - 00:01:21) The cell membrane is composed of: Phospholipid bilayer Provides structure and barrier to the cell membrane Amphipathic - has a polar head group and two hydrophobic tails Allows the membrane to associate with both the aqueous external and internal layers, while having a hydrophobic inner layer Provides a stable yet flexible membrane Glycolipids Cholesterol Proteins Glycoproteins (00:01:21 - 00:01:37) The phospholipid bilayer is selectively permeable This means it allows certain substances to pass through while blocking others (00:01:37 - 00:01:51) The lipid bilayer is selectively permeable This allows for a stable yet flexible membrane Permeability of the Cell Membrane (00:01:51 - 00:02:05) The permeability of the cell membrane depends on the polarity and size of the particles Small particles, like gases, can generally pass through the cell membrane Small and nonpolar particles can pass through the cell membrane very quickly (00:02:05 - 00:02:26) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bca8ab287f54e41f2a7/document?go=note 1/5 8/27/24, 8:21 PM Platform | Study Fetch Small and polar particles can also pass through the cell membrane, but at a slower rate Large nonpolar particles, like cholesterol and steroid hormones, can also pass through the cell membrane, but more slowly Large polar particles, like proteins, are not permeable to the cell membrane Membrane Molecules (00:02:38 - 00:02:51) The cell membrane has several structural components, including: Glycolipids Cholesterol Glycoproteins (00:02:51 - 00:03:04) Cholesterol provides rigidity and flexibility to the plasma membrane, depending on the temperature or torsion the cell membrane is exposed to The amount of cholesterol can change the fluidity of the cell membrane (00:03:04 - 00:03:17) The cell can adjust the fluidity of the cell membrane to cope with mechanical or temperature stresses (00:03:17 - 00:03:28) Membrane proteins associate with the lipid bilayer in many different ways Membrane Proteins (00:03:28 - 00:03:41) Transmembrane proteins form helices that are embedded in the plasma membrane Proteins can also be linked to lipids, which can then be embedded in the plasma membrane This allows the protein to stay attached to the plasma membrane (00:03:41 - 00:03:57) Many transmembrane proteins associate with other proteins, keeping those proteins bound to the cell membrane (both internal and external) (00:03:57 - 00:04:15) Transmembrane proteins get embedded in the membrane during translation, in the endoplasmic reticulum (ER) After being embedded in the ER, they are then shuttled through the Golgi and out to the cell surface (00:04:15 - 00:04:26) Lipid-linked proteins undergo post-translational modification in the Golgi, where the lipids are added to the peptides This allows the lipid-linked proteins to be embedded in the plasma membrane (00:04:26 - 00:04:37) Protein-associated proteins are anchored to the cell membrane by a single embedded protein, with multiple other proteins associating on top of that (00:04:37 - 00:04:58) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bca8ab287f54e41f2a7/document?go=note 2/5 8/27/24, 8:21 PM Platform | Study Fetch There are many different types of membrane proteins, including: Carrier proteins Ion channels Cell surface receptors (00:04:58 - 00:05:08) Protein channels, carrier proteins, and ion channels allow for the movement of ions across the cell membrane Ion Channels and Membrane Transport (00:05:08 - 00:06:55) Ion Channels Ligand-gated Ion Channels: Open in response to an external signal For example, a presynaptic neuron sends a signal to a postsynaptic neuron, inducing the opening of ligand- gated ion channels Mechanically-gated Ion Channels: Opened by mechanical stimuli, such as pressure on nerve endings in the skin This causes the cell to become polarized Voltage-gated Ion Channels: Found in the heart and other excitable tissues Open in response to changes in the cell's voltage potential Leak Channels: Always open, help maintain ion equilibrium across the cell membrane Membrane Transport Proteins ATP-powered Transport: Use ATP to actively transport materials across the membrane Can transport nutrients, glucose, neurotransmitters, etc. Anchor Proteins: Provide stability and allow cells to connect and anchor to each other and the extracellular matrix Important for signal transduction and cell-cell communication Receptors: Embedded in the cell membrane Crucial for signal transduction and cellular responses to external stimuli (00:05:08 - 00:05:21) (00:05:21 - 00:05:33) https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bca8ab287f54e41f2a7/document?go=note 3/5 8/27/24, 8:21 PM Platform | Study Fetch (00:05:33 - 00:05:48) (00:05:48 - 00:06:02) (00:06:02 - 00:06:18) (00:06:18 - 00:06:30) (00:06:30 - 00:06:55) The Cell Membrane (00:06:55 - 00:07:06)The cell membrane is a crucial structure that allows cells to coordinate their activities and communicate with each other. It contains recognition proteins that enable cells to identify themselves, recognize if they are infected with a virus, and perform other important functions. Cell membrane allows for: Coordination of cell activities Cell-cell communication Self-recognition Identification of infected cells (00:07:06 - 00:07:19)The cell surface is coated with a carbohydrate layer called the glycocalyx. This layer provides protection for the cell surface against mechanical damage. Glycocalyx: Carbohydrate layer on cell surface Provides mechanical protection for cell (00:07:19 - 00:07:41)The glycocalyx is also important for cell-cell recognition and identification of specific cell types. Carbohydrate tags are added to the glycocalyx, and if the correct tags are not present, it can indicate something is wrong with the cell. The glycocalyx can also help white blood cells squeeze through narrow spaces and coat them when they extravasate. Glycocalyx functions: Cell-cell recognition Identification of cell types Carbohydrate tags indicate cell health Aids white blood cells in extravasation (00:07:41 - 00:07:55)The extracellular matrix (ECM) provides mechanical support and binds adjacent cells together. Extracellular matrix (ECM): Provides mechanical support Binds cells together (00:07:55 - 00:08:12)The ECM is integrally associated with the cell membrane and works closely with it to provide structural support for the cell layers. The integrins in the cell membrane mediate this interaction with the ECM. https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bca8ab287f54e41f2a7/document?go=note 4/5 8/27/24, 8:21 PM Platform | Study Fetch Integrins: Integral membrane proteins Mediate interaction between cell membrane and ECM Provide structural support for cell layers https://www.studyfetch.com/platform/studyset/66cd116dd279f5220d947c66/material/66ce6bca8ab287f54e41f2a7/document?go=note 5/5