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62 Cards in this Set
- Front
- Back
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What cell membrane molecules are amphipathic? |
Phospholipids SK |
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Why are cellular membranes considered to be "fluid"? |
The hydrophilic regions of a protein has maximum contact with water in the cytosol and extracellular fluid. SK |
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How does cholesterol help membranes resist changes in fluidity when temperature changes? |
It restrains phospholipid movement and also hinders the close packing of phospholipids in order to lower the temperature required for the membrane to solidify. SK |
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Why are cellular membranes considered to be a “mosaic”?
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Protein molecules bob in a fluid bilayer of phospholipids, but are not randomly distributed in the membrane. SK |
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What are the two major types of membrane proteins? |
Integral proteins and peripheral proteins SK |
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List the six major functions of membrane proteins. |
Transport Enzymatic Attachment to the cytoskeleton and extracellular matrix Cell-cell recognition Intercellular joining Signal transduction SK |
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How do cells recognize each other? |
By binding to molecules, that often contain carbohydrates, on the extracellular surface of the plasma membrane
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What type of molecules can cross the cell membrane easily, without help from membrane proteins? |
Nonpolar SK |
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Explain the difference between channel and carrier proteins. |
Channel proteins -- have a hydrophlilic channel that certain molecules or atomic ions use as a tunnel through the membrane.
Carrier proteins -- hold onto their passengers, change shape, and shuttles them across. SK |
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Why is diffusion considered to be a form of passive transport? |
Because the cell doesn't have to expend energy to make it happen.
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What happens to a cell placed in an isotonic solution? |
Nothing will happen to the cell because in an isotonic environment the cell volume is stable.
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What happens to a cell place in a hypertonic solution? |
The cell looses water, shrivels, and probably dies.
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What happens to a cell placed in a hypotonic solution? |
The water will enter the cell, causing the cell to swell and burst (lyse)
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Describe how ATP powers active transport. |
It supplies the energy for most active transport.
One way is by transferring its terminal phosphate group directly to the transport protein. SK |
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What two forces drive the diffusion of ions across a membrane? |
A chemical force and an electrical force.
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What is the name for the combination of these two forces? |
The electrochemical gradient SK |
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Electrogenic pumps are transport proteins that generates a voltage across a membrane. What are the major electrogenic pumps found in animal cells and plant cells? |
Sodium-potassium pump - animals
proton pump - plants, fungi, and bacteria SK |
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How do larger molecules generally move across the cell membrane? |
In bulk by mechanisms that involve packaging in vesicles. SK |
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How is receptor-mediated endocytosis differ from pinocytosis? |
Receptor-mediated endocytosis -- enables cell to acquire bulk quantities of specific substances, even though those substances may not be very concentrated in the extracellular matrix. Pinocytosis -- not specific for the substances it transfers, any and all solutes are taken into the cell. SK |
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What are two ways cells can communicate locally? |
growth factors, paracrine signaling
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What two ways do cells communicate with long-distance signaling? |
Hormones (endocrine signaling) Synaptic signaling SK |
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Describe the three stages of cell signaling |
1) Reception: the target cell's detection of a signaling molecule coming from outside the cell 2) Transduction: a step or series of steps that converts the signal to a form that can bring about a specific cellular response. Usually requires a signal transduction pathway. 3)The transduced signal finally triggers a specific cellular response. Response may be any imaginable cellular activity. SK |
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Active transport |
Type of membrane traffic that requires the cell to expend energy to pump a solute across a membrane against its gradient.
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Amphipathic |
It has both a hydrophilic region and a hydrophobic region. SK |
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ATP |
Contains the sugar ribose, with the nitrogenous base adenine and a chain of three phosphate groups bonded to it. It is also one otf the nucleoside triphosphates used to make RNA. Used for energy.
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Bulk transport |
Large molecules and larger particles generally cross the membrane in bulk by mechanisms that involve packaging in vesicles.
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carrier proteins |
Proteins that hold onto their passengers and change shape in a way that shuttles them across the membrane.
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Cell recognition |
A cells ability to distinguid one type of neighboring cell from another.
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Channel proteins |
Proteins that provide corridors that allow specific molecules or ions to cross the membrane.
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Cholesterol |
A steroid important to a cell membrane.
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Concentration gradient |
the region along which the density of a substance increases or decreases.
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Cotransport |
A mechanism that a single ATP-powered pump that transports a specific solute that can indirectly drive the active transport of several other solutes. SK |
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Diffusion |
Results in the net movement of a substance from a region where it is more concentrated to a region where it is less concenrated SK |
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Electrochemical gradient |
The diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane (chemical force) and the ion's tendency to move relative to the membrane potential (an electrical force).
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Endocytosis |
Cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane.
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Exocytosis |
The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane.
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Facilitated diffusion |
The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure.
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Fluid mosaic model |
Envisions the membrane as a mosaic of protein molecules bobbing laterally in a fluid bilayer of phospholipids.
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Hydrophilic |
Having an affinity for water. (likes water)
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Hydrophobic |
No affinity for water. (Forms droplets in water, doesn't like water)
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Hypertonic |
Referring to a solution that will case the cell to loose water when it surrounds a cell.
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Hypotonic |
When surrounding a cell, a solution that will cause the cell to take in water. (swell)
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Integral proteins |
Has hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with the hydrophilic regions in contact with aqueous solution on one or both sides. Transmembrane protein.
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Isotonic |
When a solutions surrounds a cell and causes no net movement of water in or out of the cell. SK |
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Local cell signaling |
Synaptic signaling - nervous system paracrine signaling - cells simultaneously receive and resond to the molecules of growth factor produced by a nearby cell. SK |
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Long-distance cell signaling |
Endocrine signaling - hormones (chemicals) released and travel via circulatory system to other part of body. SK |
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Membrane potential |
The difference in electrical charge (voltage) across a cell's plasma membrane due to the differential distribution of ions.
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Membrane proteins |
Proteins that make up the membrane
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Osmosis |
The diffusion of free water molecules across a selectively permeable membrane
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Passive transport |
The diffusion of a substance across a biological membrane with no expenditure of energy.
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Peripheral proteins |
A protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer.
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Phagocytosis |
A type of endocytosis in which large particulate substances substances or small organisms are taken up by a cell.
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Phospholipids |
A lipid made up of glycerol joinedto two fatty acids and a phosphate group. Has a hydrophilic head and hydrophobic tail.
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Pinocytosis |
A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.
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Plasma membrane |
The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell's chemical composition.
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Reception |
The binding of a signaling molecule to a receptor protein, activating the receptor by causing it to change shape.
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Receptor-mediated endocytosis |
The movement of specific molecules into a cell by the inward budding of vesicles containing proteins with receptor sites specific to the molecules being taken in.
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Response |
The change in a specific cellular activity brought about by a transduced signal from outside the cell.
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Selectively permeable |
It allows some substances to cross it more easily than others. SK |
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Six major functions of membrane proteins |
Transport Enzymatic Attachment to the cytoskeleton and extracellular matrix Cell-cell recognition Intercellular joining Signal transduction SK |
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Transduction |
The conversion of a signal from outside the cell to a form that can bring about a specific cellular response SK |
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Transport proteins |
A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane SK |
