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M1 S1.3 Transport a
Module 1 Section 1.3 Lessons A- D Proteins Transport Across Cell Membranes
| Question | Answer |
|---|---|
| Cell Membranes | Separates internal environment of the cell from external environment. It is selectively permeable, and regulates the entrance and exit of molecules into and out of the cell. water, carbon dioxide, oxygen, and glucose, can easily pass through this screen |
| Phospholipid bilayer | Phospholipid bilayer has fluid consistency, similar to oil, allowing lipid molecules to move freely. Exchanges take place is between inside of cell and outside environment. This is how most cells get food & eliminate waste products of metabolic reactions. |
| rate of diffusion | Determined by many factors including temperature, type of molecules and permeability. |
| Proteins | Proteins in membrane serve different functions, depending on structure & location. Proteins may be peripheral (on inside surface of membrane, held in place by cytoskeleton) or integral (embedded in the membrane but can move laterally back and forth). |
| carrier protein | A protein that allows the molecule to enter, combines with the molecule, and changes the shape to allow the molecule to exit the other side of the cell membrane. |
| channel protein | channels (channel proteins), through which a particular molecule or ion can move freely across the membrane. |
| receptor protein | have a specific shape that allows a certain molecule, such as a hormone, to bind to it. This may cause the protein to change shape and create a cellular response. |
| Enzymatic proteins | catalyze (speed up) specific metabolic reactions. |
| Cell recognition proteins | composed of carbohydrate chains that give individual cells a unique fingerprint that facilitates adhesion between cells, cell-to-cell recognition, and reception of signal molecules. Cells foreign fingerprints attacked by blood cells-responsible immunity. |
| carbohydrates | Carbohydrate chains attached to membrane lipids & proteins on cell's outer surface. These glycolipids & glycoproteins give each cell unique fingerprint, allowing cells to adhere, to receive signals from various molecules, and to recognize other cells. |
| fluid-mosaic model | Protein molecules are randomly distributed throughout the plasma membrane. The membrane's phospholipid bilayer has a fluid consistency, similar to oil, and lipid molecules have freedom to move. |
| glycolipids | Fats that have attached carbohydrate (sugar) chains |
| glycoproteins | Proteins that have attached carbohydrate (sugar) chains |
| phospholipids | Main constituent of plasma membrane. Hydrophilic (water-loving) heads of molecule face outside and inside of cell. Hydrophobic (water-fearing) tails face each other in inner part of membrane. Phospholipids with carbohydrate (sugar) chains- glycolipids. |
| selectively permeable | The plasma membrane is selectively permeable because some substances can move freely across it while others can not. There are two ways for molecules to pass through a plasma membrane—one is active, the other is passive. |
| concentration gradient | molecules follow their concentration gradient when they move from area where concentration is high to area where their concentration is low. |
| diffusion | movement of molecules from an area of high concentration (more solute than solvent) to an area of lower concentration (less solute than solvent.) Simple diffusion only works for very small, uncharged molecules such as O2, CO2, and H2O. |
| facilitated diffusion/transport | the movement of a molecule from an area of high concentration to an area of lower concentration (diffusion), with the aid of a protein channel or carrier. For larger molecules or charged ions (e.g., amino acids, glucose, Na+, and K+) |
| hypertonic solutions | cells shrink or shrivel up due to the movement of water out of the cell. an environment with more solute and less water than inside the cell. |
| crenation | The shrinkage of an animal cell placed in hypertonic solution When a plant cell is placed in this solution, the plasma membrane pulls away from the cell wall |
| plasmolysis | a shrinking of the cytoplasm due to osmosis. |
| hypotonic | cause cells to swell or even burst due to the intake of water. |
| isotonic solutions | equilibrium—equal con of molecules. Same solute/water, inside/outside cell. Iso same as tonicity concent of solute in solution. Concentrations = no net gain/loss water by cell. water st moves in/out cell,no net move of water/change cell vol.same size |
| lysis | the build-up of pressure in the cell, can cause it to burst |
| osmosis | diffusion of water thru semi-permeable membrane. W moves fr area high water con (low solute con) to low(or high solute c.)Cells affected by osmosis. water concen of solution surrounding cell determines direction of water flow, either into or out of cell. |
| osmotic pressure | the force that moves the water in either direction. |
| Cell environments | depending on the concentration of solutes outside the cell is either isotonic solutions, hypotonic solutions, and hypertonic solutions. |
| cholesterol | This lipid, with its four-fused-rings structure, and related steroids are found in the plasma membrane. They stiffen and control the fluidity of the membrane. |
| concentration gradient | passive transport depends on a concentration difference (called a 'gradient') and on the permeability of the cell membrane |
| passive transport | movement of biochemicals/molecules across membranes,w no chemical energy. Passive transport dep concentration difference ('gradient') + permeability of cell membrane, which in turn is dependent on organization/characteristics of membrane lipids/proteins. |
| turgor pressure | necessary for cells to maintain their shape. When plants wilt, it is from the loss of water from the cells, lessening turgor pressure. |
| active transport | transport solute x cell's membrane against concentration gradient. Ions/molecules mov across cell'smembrane accum inside/outside cell. carrier proteins+energy ATP. Energy for carrier change shape-transport mol x membrane. Proteins to pump sub x con grad. |
| endocytosis | requires the use of a cell's ATP energy to alter the shape of the membrane surface (called invagination) to allow large molecules into the cell. 2 main types: phagocytosis and pinocytosis (Receptor mediated endocytosis) |
| exocytosis | involves movement of materials out of cell. requires ATP energy-create vesicle/ vacuole migrate-membrane's inner surface-fuse w cell membrane. Energy needed to alter membrane shape-allow vesicle merge w cell membrane&force its contents to outside of cell. |
| Endocytosis (entering the cell) and exocytosis (exiting the cell) | the two methods of active transport that allow macromolecules to move through the plasma membrane using a vesicle. Basically, they are swallowed up and spit out by the plasma membrane itself. |
| phagocytosis | Allows large particles into the cell In the human body, various white blood cells engulf debris such as bacteria and worn out red blood cells through the process of phagocytosis. |
| pinocytosis | Allows liquid and very small particles into the cell It's by this process that the villi of the small intestine are able to absorb small nutrient particles. |
| Receptor mediated endocytosis | receptor protein shaped to fit/bind w vitamin, peptide hormone or lipoprotein. receptors at coated pit-forms vesicle-carries subs cell. More eff pinocytosis, receptor-mediated endocytosis selective-inv uptake, transfer-exchange-substances bt cells. |
| Sodium-potassium pump | Protein that pumps out sodium and allows back potassium |
| How is active transport different from facilitated transport? | Active transport molecules AGAINST concentration gradient. Facilitated transport w concentration gradient. Moving molecules against gradient requires energy. Therefore, active transport requires chemical energy where as facilitated transport doesnt. |
| surface area | Surface area affects cell's ability to move molecules in-out. As cell larger and radius increases, volume increases, surface area to volume ratio decreases &cell less efficient. greater surface-area-to-volume ratio -cell more eff transp mole xcell. |
| Larger cells | less effective at moving materials across the membrane because they have a lesser surface-area-to-volume ratio than smaller cells. Therefore, larger cells are not able to function at their optimal level of efficiency. |
| volume | The lower the volume, compared to the surface area, the more efficient the cell. Volume= 4/3 m3 a greater surface-area-to-volume ratio makes a cell more efficient. |
| surface | Nutrients enter a cell and wastes exit a cell at its surface; therefore, the amount of surface affects the ability to get material in and out of the cell. |
| Prokaryotic cells | smallest cells, For example, an Escherichia coli bacteria |
| eukaryotic cells | Mammalian red blood cells are among the smallest eukaryotic cells. |
| amoeba | a relatively large single celled organism, |
| Metabolic processes | all chem processes at cellular level keep cell, whole organism alive. Protein synth, respir, digest, waste removal-ex of metabolic processes. Molecules inside-outside cell, such as carbs, enzymes, hormones, nucleic acids must interact and react together. |
| Enzymatic protein | A protein that allows chemical reactions to take place inside a cell. |
| Hypertonic solution | When a solution contains a higher concentration of solute to solvant on the inside of the cell. |
| Hypotonic solution | When a solution contains a higher concentration of solvent to solute on the inside of the cell. |
| Isotonic solution | Equal amounts of solvent and solute inside and outside of the cell |
| Describe why a donor's cells are sometimes rejected from a recipient's body. | The cells donated have a different cellular fingerprint (i.e., different sugar chains) from those of the recipient. The recipient's body cannot recognize the glycoproteins and glycolipids, and the immune system attacks the foreign cells. |
| What special mechanism maintains a higher than normal sodium ion concentration on one side of certain cell membranes and a higher than normal potassium ion concentration on the other side of the cell membranes? | The sodium/potassium pump |
| Distinguish between phagocytosis and pinocytosis. | Phagocytosis is the endocytosis of large particles. Pinocytosis is the endocytosis of liquid and very small particles. |
| A biochemist working on a banana leaf is studying plant's cells. Chemist finds concentration of phosphates inside cells is 125 mg/L while phosphates outside cell is only 15 mg/L. A. In which direction would you predict phosphate molecules will move? | A. Phosphate molecules will move out of the cells because the concentration of the phosphates is much greater inside the cell. |
| B. The chemist finds that the cells are actually accumulating more and more phosphates. What method of transport is at work? Explain. | B. Active Transport. During active transport, ions and molecules moving across the plasma membrane are accumulating either inside or outside the cell |
| What is the rate of diffusion determined by? | size—smaller molecules can slip by polar heads of phospholipids but larger molecules cannot shape—carrier proteins are specifically shaped to carry only certain molecules • concentration—gradient betw outside/inside of cell, greater rate of diffusion |
| What is the rate of diffusion determined by? (continued) | charge (+/–)—ions/molecules charged cannot easily pass thr membrane, unless facilitated.• lipid solubility—molecules -steroid hormones testosterone/estrogen cons lipid soluble can move easily thru lipid bilayer. |
| What is the rate of diffusion determined by? (continued) | • temperature—the rate of diffusion increases as the temperature increases because the particles are moving faster (kinetic molecular theory) |
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