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Biology Chapter 3
3A, 3B, 3C
| Question | Answer |
|---|---|
| plasma membrane | the phospholipid bilayer and embedded proteins which separate the intracellular environment from the extracellular environment. its is selectively permeable |
| selective permeability | a property of cell membranes that ensures only specific substances pass across them. Also known as semipermeable |
| The main components of the plasma membrane | phospholipids |
| phospholipids | the main molecule of which membranes are composed. They have a phosphate head and two fatty acid tails |
| phospholipid bilayer | a double layer of amphiphilic molecules that forms the primary component of cell membranes |
| Phospholipids have a | phosphate head and two fatty acid tails. The phosphate head and fatty acid tails are chemically very different from each oth |
| phosphate head | the hydrophilic subunit of a phospholipid, made of a glycerol and phosphate group • negatively charged, making it hydrophilic (‘water-loving’) and polar. |
| fatty acid tail | the hydrophobic lipid subunit of a phospholipid, made of long chains of carbon and hydrogen • uncharged, hydrophobic (‘water-fearing’), and nonpolar. |
| amphipathic | describes molecules with both hydrophilic and hydrophobic components, makes the membrane stable |
| protein | a class of biomacromolecule made of amino acid monomers folded into a 3D shape, consisting of carbon, hydrogen, oxygen, nitrogen, and sometimes sulphur |
| 3 types of proteins: | Integral protein – proteins that are a permanent part of the membrane Transmembrane protein – integral proteins that span the entire bilayer Peripheral protein – are temporarily attached to the plasma membrane |
| functions of proteins | Transport Catalysis Communication Adhesion |
| carbohydrate | Usually in chains that extend outside the cell, rooted in the membrane to lipids (glycolipids) or proteins (glycoproteins) |
| functions of a carbohydrate | Aid with cell-cell communication, signalling, recognition of self or non-self (foreign) molecules, and adhesion |
| cholesterol | A lipid steroid that embeds itself between the fatty acid tails of the phospholipid bilayer in animal cells. Cholesterol is replaced with similar molecules in other kingdoms, but all are functionally similar |
| functions of cholesterol | Regulates the fluidity of the membrane. At higher temperatures, the cholesterol keeps phospholipids bound together. At lower temperatures, cholesterol disrupts the fatty acid tails, stopping phospholipids from becoming a solid boundary |
| fluid mosaic model | the theory of how the plasma membrane is structured, explains that 1) molecules that make up the membrane are not held static in one place and 2) many different types of molecules are embedded in the plasma membrane. |
| fluid part explained | because phospholipids continually move laterally (side to side) in the membrane. Occasionally, phospholipids may ‘flip-flop’ between the two layers of the plasma membrane |
| mosaic part explained | comes from the proteins and carbohydrates embedded in the membrane |
| passive transport | the movement of molecules through a semipermeable membrane and down the concentration gradient, without an input of energy |
| diffusion | the passive movement of molecules from areas of high concentration to areas of low concentration (down the concentration gradient) |
| What types of molecules can freely diffuse across the plasma membrane? | Polarity – nonpolar, uncharged, or hydrophobic molecules (e.g. O2, H2, CO2. lipids) Size – small molecules like water are able to slip through the lipids in the phospholipid bilayer. |
| Will the nonpolar, small molecules diffuse into or out of the cell? | Molecules diffuse into or out of the cell depending on their concentration on either side of the plasma membrane. Once equilibrium is reached, solute moves equally in both directions |
| facilitated diffusion | a type of passive transport where molecules move through a phospholipid bilayer with the aid of a membrane protein |
| protein used in facilitated diffusion | protein channel or a carrier protein. |
| Osmosis | the passive transport of a solvent (typically water) through a semipermeable membrane from a region of low solute (high solvent) to a region of high solute (low solvent) |
| why is water movement increased? | by protein channels known as aquaporins. |
| tonicity | a measure of the relative concentration of solutes on either side of a semipermeable membrane, described as hypertonic, hypotonic, or isotonic |
| hypertonic | describes a solution with a higher solute concentration when compared to another solution |
| isotonic | describes a solution with the same solute concentration as another solution |
| hypotonic | describes a solution with a lower solute concentration when compared to another solution |
| turgid | describes plant cells that are swollen and firm from water uptake |
| plasmolysed | describes plant cells with weak and sagging plasma membranes from water loss |
| lyse | to cause a cell plasma membrane to burst or break |
| active transport | movement of molecules across a semipermeable membrane that requires energy agaisnt their concentarion gradient |
| protein-mediated active transport | a type of active transport which involves using membrane proteins to move molecules across a membrane against their concentration gradient. |
| bulk transport | a type of active transport that uses vesicles to move large molecules or groups of molecules into or out of the cell. |
| why do we need active transport? | despite being a differnce in solute concentrationthe cell may still require to function optimally – so it must somehow draw into the cytosol, against its concentration gradienr |
| The process of active transport occurs in the following three steps: | 1 Binding – the target molecule for transport binds to a specific protein pump 2 Conformational change – energy released causes a change in the protein pump. 3 Release – the target molecule is pushed through the protein and released |
| where does the energy come from? | This energy comes from breaking the bond between the second and third phosphate ions in the ATP molecule |
| what molecules does bulk transport move? | large molecules or groups of molecules – such as amino acids, proteins, signalling molecules, or pathogens – into or out of the cell using vesicles. |
| There are two types of bulk transport | exocytosis and wndocytosis |
| exocytosis | a type of bulk transport that moves large substances out of the cell |
| endocytosis | a type of bulk transport that moves large substances into the cell |
| Exocytosis pre process | proteins are made at ribosomes located on the surface of the rough endoplasmic reticulum, sorted, packaged, and modified at the Golgi apparatus, and then transported by vesicles to the plasma membrane for exocytosi |
| exocytosis process | 1 Vesicular transport – a vesicle containing secretory products is transported to the plasma membrane 2 Fusion – the membranes of the vesicle and cell fuse 3 Release – the secretory products are released from the vesicle and out of the cell. |
| whyis fusion possible | as the phospholipid bilayer is fluid it and can fuse with the phospholipid bilayers of a vesicle. |
| Endocytosis process | Fold – membrane folds inwards to form a cavity fills with extr fluid and molecules. Trap – membrane cont folding back until the ends meet and fuse. Bud – the vesicle pinches off from the membrane. transported to the appropriate location or lysosom |
| phagocytosis | endocytosis of solid material or food particles |
| pinocytosis | endocytosis of liquid or dissolved substances |
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