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Biology Chapter 7
Membrane Structure and Function
| Term | Definition |
|---|---|
| Plasma(cell) Membrane | Called Fluid Mosaic Model because membrane is a fluid structure with a "mosaic" of various proteins embedded in or attached to a double layer of phospholipids(call bilayer). Is also a semipermeable(selective) membrane. 2 Main Parts... 1.Fluid.. 2.Mosaic |
| Semipermeable | Allows some substances to cross more easily than others |
| Factors That Matter in Permeability | Size, charge, and polarity |
| Fluid | 40% of the plasma(cell) membrane is a bilayer of phopholipids and cholesterol(animal cell only). Phospholipids and cholesterol give bilayer fluidity |
| Amphipathic (Amphi = Both) | Has both a hydrophilic and hydrophobic region. Ex: phopholipids |
| Cholesterol | Helps maintain fluidity of Animal cell membranes at cooler temperatures |
| Unsaturated Fatty Acids | Helps maintain fluidity of Plant cell membranes at cooler temperatures |
| Mosaic | 60% of the plasma(cell) membrane is a collection of different proteins that differ in sizes and shapes often clustered in groups that are embedded in the fluid bilayer. *Different membranes have different proteins. |
| Integral Proteins | Proteins that penetrate the hydrophobic interior of the lipid bilayer |
| Transmembrane Protein | Integral proteins that span the membrane from surface to surface(span the whole distance across the bilayer). Most abundant protein in the bilayer |
| Peripheral Proteins | Proteins that are not embedded in lipid bilayer; loosely bound to the surface of the membrane, often to the exsposed parts of the integral proteins |
| Functions of Membrane Proteins | 1. Channel proteins(a transport protein).. 2. Carrier proteins(a transport protein).. 3. Enzymatic activity.. 4. Cell-to-cell recognition |
| Channel Proteins(A transport protein) | Function by having a hydrophilic channel that certain molecules or ions use as a tunnel through the membrane. Acts as a gateway |
| Carrier Proteins(A transport protein) | Hold onto their passengers and change shape in a way that shuttles them across the membrane. Have very specific shapes |
| Enzymatic Activity | Some proteins can function as enzymes |
| Cell-to-Cell Recognition | Glycolipids and glycoproteins function as cell surface receptors, they receive stimuli. Also help in the recognition of self vs. nonself by acting as feelers for other cells membrane proteins, which are unique to each cell |
| Glycolipid | A carbohydrate chain bound to a lipid(phospholipid) in the bilayer |
| Glycoprotein | A carbohydrate chain bound to a protein on the bilayer |
| Gradients | Measured difference of some property from one area compared to another. Two main differences... 1. Concentration gradient.. 2. Electrical gradient |
| Concentration Gradient | Difference in concentration of some solute. Can be measured in percent(%) or molarity(M) |
| Electrical(chemical) Gradient | Differences in net positivity or net negativity |
| Extra-Cellular Fluid(ECF) vs. Cytosol | The cell is constantly exchanging things between the cytosol and the fluid outside the cell which is called extra-cellular fluid(ECF) |
| Transport Processes | 1. Passive Transport.. 2. Active Transport |
| Passive Transport | Movement with the gradient(High to Low) and so does not require ATP. Will establish equilibrium by random movement, don't always use a protein |
| Active Transport | Movement against the gradient(Low to High) and so requires energy source(ATP). Will not establish equilibrium and will increase the gradient because movement is directional. Requires a membrane transport protein(called "pumps") |
| Types of Passive Transport Processes | 1. Simple diffusion.. 2. Osmosis |
| Simple Diffusion | Random movement of molecules from regions of higher concentration to regions of lower concentration. H to L. Substances diffuse down a concentration gradient |
| Factors which Determine Rate of Diffusion | 1. Temperature.. 2. Size of Molecules.. 3. Molecular Phase.. 4. Molecular Composition.. 5. Size of Gradients |
| Temperature Effect on Diffusion | As temperature increases, rate of diffusion increases |
| Size of Molecule Effect on Diffusion | As size of molecule increases, rate of diffusion decreases |
| Molecular Phase Effect on Diffusion | Three molecular phases: solid, liquid, and gas. Solid substance(slowest). Gaseous substance(fastest) |
| Molecular Composition Effect on Diffusion | Three Molecular Compositions: Nonpolar Covalent, Polar Covalent, and Ionic. Nonpolar covalent substance diffuses fastest because hydrophobic, Polar covalent is Medium because hydrophilic, and Ionic is slowest because hydrophilic |
| Size of Gradient Effect on Diffusion | The greater the difference in gradient, the faster the rate of diffusion. As the gradient decreases with diffusion, rate of diffusion decreases |
| Osmosis | Diffusion of water. Random movement of water from areas of high water content(low solute content) to areas of low water content(high water content). |
| Aquaporins | Channel protein that allows water to pass through the phospholipid bilayer because diffusion is to slow without this |
| Hypertonic Solution | Solutions that have a higher solute concentration and lower water content when compared to second solution |
| Hypotonic Solution | Solutions that have a lower solute concentration and a higher water content when compared to a second solution. |
| Isotonic Solution | The concentration of solutes and water content are equal in two compared solution |
| Osmoregulation | Control of water balance and solute concentrations |
| Animal Cell in Hypertonic Solution | Water travels from cell to the outside, causing the cell to shrivel(Crenate) |
| Crenate | The shriveling of a cell, because it was in a hypertonic solution |
| Animal Cell in a Hypotonic Solution | Water travels from outside to the inside of the cell, causing the cell to burst(Lysis) |
| Lysis | The bursting of a cell, because it was in a hypotonic solution |
| Animal Cell in a Isotonic Solution | Water stays put. This is the normal tonicity for an animal cell |
| Contractile Vacoule | Protozoans, such as the paramecium and amoeba, can live in hypotonic solutions and prevent lysis by using this to pump out water |
| Plant Cell in a Hypertonic Solution | Water travels from the inside of the cell to the outside, causing the cell to shrivel up inside the cell wall(plasmolysis), which remains unchanged |
| Plasmolysis | When the plasma membrane pulls away from the cell wall, because it was in a hypertonic solution |
| Plant Cell in a Hypotonic Solution | Water travels from the outside to the inside of the cell, causing the plasma membrane to push up against the cell wall(turgid). This is the normal tonicity of a plant cell |
| Turgid | When the plasma membrane presses up against cell wall, causing a high turgor pressure. Happens when cell is placed in a hypotonic solution. This allows the cell to grow and expand |
| Plant Cell in a Isotonic Solution | Water stays put, causing the inside of the cell to have a low turgor pressure(flaccid). Cell inside looks wilted |
| Flaccid | When there is a low turgor pressure in a cell, causing it to appear wilted. Happens when cell is placed in isotonic solution |
| Carrier Facilitated Diffusion(CFD) | Diffusion that occurs with the help of membrane transport proteins for molecules that are slow movers in simple diffusion. Rate of diffusion is increased by CFD. Can be the only way across the bilayer for some substances. Ex: glucose and ions transport |
| Types of Active Transport | 1. Electrogenic Pumps.. 2. Cotransport Pumps.. 3. Bulk Transport |
| Active Transport | Movement against concentration gradients(L to H) using carrier protein(pumps). Requires ATP |
| Electrogenic Pumps | Transport proteins that generate voltage across a membrane. Creates electrochemical gradient |
| Voltage | Electrical potential energy by a separation of opposite charge |
| Electrochemical Gradient | A concentration(chemical) gradient and an electrical(voltage) gradient where one side of the membrane has a difference in charge and concentration of ions than the other side of the membrane. Source of potential energy |
| Membrane Potential | Voltage across a membrane causing a difference in the voltage from one side of the membrane vs. the other |
| Types of Electrogenic Pumps | 1. Proton Pump.. 2. Sodium-Potassium Pump |
| Proton Pump | Pumps H+ ions(protons) from a low content to a high content |
| Sodium-Potassium Pump(Na+/K+) | Primes nerve cells to fire an impulse, this process uses 1/3 of all your cell's ATP |
| Cotransport Pump | A. Works with other pump which has actively transported a substance across the membrane and has created a gradient... B. As the molecule diffuses back through another(second) cotransport pump, energy is released |
| Cotransport Pump Continuation | C. Energy is harnessed to drive the active transport of the second solute in tandem with the first solute across the membrane.(Occurring at the same time as part B) |
| Bulk Transport | When molecules are too large to or there are to many to pass through the membrane, they are packaged in bulk in vesicles. The two types of bulk transport are... 1. Endocytosis.. 2. Exocytosis |
| Endocytosis | The plasma membrane pinches in to create a vesicle. The three types of endocytosis are... 1. Phagocytosis.. 2. Pinocytosis.. 3. Receptor Mediated Endocytosis |
| Phagocytosis | Engulfment of solid materials. Creates a vesicle called a endocytic vesicle. "cellular eating" |
| Pinocytosis | Engulfment of liquid materials. "cellular drinking" |
| Receptor Mediated Endocytosis | Using cell surface receptors to collect molecules which cluster to a spot and then are pinched inward |
| Exocytosis | Vesicles fuse with plasma membrane and secrete or release molecules |
Created by:
TimBiology1
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