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Description
Flashcards by emma_moran, updated more than 1 year ago
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Created by emma_moran
almost 12 years ago
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| Question | Answer |
| What model best explains the plasma membrane? | Fluid mosaic model |
| What is the phospholipid bilayer composed of? | Phospholipids, cholesterol and glycolipids |
| Is cholesterol polar? | Weakly amphipathic- OH group is polar and the rest is non polar |
| How does cholesterol attach to phospholipids? | It forms a hydrogen bond with the polar heads of the phospholipids |
| Roles of membrane proteins | Form the glycocalyx, required for the detection of 'self' in immunity, aids in cell-cell adhesion |
| What are the functions on the plasma membrane? | Regulates what enters and exists the cell which controls pH and charge, cell recognition, cell signalling from hormones, enzymatic functions and aids in cell linking and cross talk |
| What determines the fluidity of the membrane? | The double bonds within lipids |
| What effect does cholesterol have on the first few hydrocarbon groups of the phospholipids? | It immobilises them which makes the bilayer less deformable and decreases its permeability to small water soluble molecules. |
| What is a feature of intracellular membranes? | They contain less cholestrol |
| Why is it necessary for the membrane to be fluid? | Allows interactions to occur within the plasma membrane and allows the movement of membrane components required for cell movement, growth, division, secretion and the formation of cellular junctions |
| What is the purpose of selective permeability of plasma membranes? | It allows the cell to build concentration gradients, pH can be regulated and electrical gradients are built (inside of cell is more -ve) creating membranes potentials |
| What molecules are permeable to the lipid bilayer? | Non-polar molecules such as oxygen, carbon dioxide and hormones |
| What molecules are impermeable to the lipid bilayer? | Ions such as NA+ and large molecules such as glucose |
| Which types of transport across the plasma membrane are passive? | Diffusion, osmosis and facilitated diffusion |
| Which types of transport across the plasma membrane are active? | Primary active transport and secondary active transport |
| Which types of transport across the plasma membrane are vesicular? | Endocytosis, phagocytosis, pinocytosis, trancytosis |
| What is diffusion? | The movement of substances down their own concentration gradient either through the lipid bilayer or through membrane channels. |
| What is facilitated diffusion? | The movement of substances down their own concentration gradient via channel or carrier proteins. |
| What is osmosis? | The diffusion of water through a semi-permeable membrane |
| What are the transmembrane proteins channels that osmosis occurs through called? | Aquaporins |
| What are the two types of pressures present in osmosis called? | Hydrostatic pressure and osmotic pressure |
| What happens to red blood cells if they are placed in a hypertonic solution? | They will shrivel because more water will leave the red blood cells than enter via osmosis |
| What happens if red blood cells are placed in a isotonic solution? | They will remain the same because the same amount of water will be entering and leaving the cells via osmosis |
| What happens if red blood cells are placed in a hypotonic solution | The red blood cells will burst because more water will enter the cells than leave via osmosis |
| How can you relive cerebral edema (water on the brain)? | Infusion of hypertonic solution |
| What is primary active transport? | Movement of a substance against its concentration gradient. ATP is required to change the shape of the carrier protein, pumping the substance across |
| What is secondary active transport (co-transport)? | Energy stored in a Na+ or H+ gradient is used to drive other substances across |
| Who is given the drug digitalis? | Patients with heart failure |
| How does digitalis work? | It slows the sodium potassium pump, allowing Na+ accumulation. This slows the Ca2+/Na+ antiporters causing Ca2+ levels to increase in the heart. This increases the strength of heart contractions. |
| What is vesicular transport used for? | Endocytosis (bringing substances into the cell) and Exocytosis (expelling from the cell). |
| What are the three types of endocytosis? | Phagocytosis, receptor mediated endocytosis and pinocytosis |
| In which cells is exocytosis important? | Nerve cells (neurotransmitters) and secretory cells (digestive enzymes and hormones) |
| What is trancytosis? | A combination of endocytosis and exocytosis. It is common in endothelial cells. |
| What are tight junctions? | Formed by the fusion of integral proteins of adjacent cells and prevent anything passing through the extracellular space between them |
| What are adherens junctions? | Plaque which attaches to membrane proteins and microfilaments of the cytoskeleton . Often form adhesion belts. Resists separation in contractile activities such as peristalsis |
| What are desmosomes and hemidesmosomes? | They are anchoring junctions held together by linker protein filaments called cadherins or integrins extending from plaques. They distribute tension and prevent tearing. |
| Where are desmosomes and hemidesmosomes usually found? | Skin and heart muscle |
| What are gap junctions? | The adjacent cells are connected by hollow cylinders called connexons made of transmembrane proteins |
| Where are gap junctions found? | In electrically excitable tissues for synchronisation such as heart and smooth muscle |
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