Chapter 5 Flashcards
What does amphipathic mean?
Example of molecule that is?
Has both hydrophilic and hydrophobic regions
Phospholipids
What is the membrane held by?
Hydrophobic interactions
In which direction can lipids and proteins in the membrane move
Laterally
Unless protein is attached to cytoskeleton or ECM
At what temperatures do membranes remain fluid?
More fluid as temperature increases unless it’s full of unsaturated hydrocarbons. These have kinks that cannot pack close together. So they are more fluid in general
What does cholesterol do to membrane fluidity?
Reduced membrane fluidity at moderate temperatures by reducing phospholipid movement, but at lower temperatures it hinders solidification by disrupting the regular packing of phospholipids.
What are the two membrane proteins
Integral proteins: protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on one or both sides of membrane.
Peripheral proteins: a protein loosely bound to the surface of a membrane or to part of integral protein and not embedded in the lipid bilayers.
What are the 6 functions of membrane proteins?
- transport-through channel or shuttle
- Enzymatic activity- enzyme with active site (binding place)
- Signal transduction- binding site with specific shape that send signals to cell.
- Cell-cell recognition- so,e glycoproteins have identification tags.
- Intercellular joining-junctions
- Attachment to cytoskeleton and ECM- maintain cell shape, coordinate IN and EC changes
Describe the role of glycolipids and glycoproteins?
Proteins that recognize other molecules that bind to them by their short carbohydrate chain. This happens in extracellular surface of the plasma membrane.
Ex: blood groups are differentiated by glycoproteins at the surface of RBC
What are some things that flow in and out of the cell
What things have a hard time crossing the plasma membranes bilayer?
Oxygen, carbon dioxide, metabolic waste, sugars. Ions, amino acids
Polar molecules and ions have difficulty
Transport proteins?
A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.
Ex: channel proteins have hydrophilic channel
Aqua porins
Channel proteins that allow passage of water molecules.
Carrier proteins
Hold onto their passengers and change shape I’m a way to shuttle them across
Passive transport
Diffusion of a substance across a membrane with no energy used
Diffusion and osmosis
Movement of a substance from an area of high concentration to an area of low concentration.
Diffusion of free water across a selectively permeable membrane.
In a solution with two solutes, both will move ______ their concentration gradient?
Down
Tonicity
The ability of a solution surrounding a cell to cause that cell to grow/ lose water
Isotonic solution
A solution that when near a surrounding cell causes no net movement of water.
Hypertonic solution
A solution that when near a surrounding cell causes the cell to lose water. (More solutes on the outside)
(Crenation if cell)(shrinkage)
Hypotonic solution
A solution that when near a surrounding cell causes water to rough into the cell. (Can lyse cell) (burst)
Osmoregulation
Regulation of solute concentrations and water balance by a cell or organism
Plasmolysis
A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell walls, occurs when the cell looses water to hypertonic solution.
Facilitated diffusion
Passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific trans membrane transport proteins, requiring no energy.
(Ions)
Ions channels are_____ and only open in response to an _____
Gated.
Electrical stimulus
Active transport
The movement of substances across a cell membrane against its concentration or electrochemical gradient, mediates by species transport proteins and requiring energy.
- carrier proteins
- ATP
Membrane potential
The difference of electrical charge across a cells plasma membrane due to the differential distribution of ions (cytoplasm more negative)
Electrochemical gradient
The diffusion gradient of an ion, which is affected by both the concentration difference of the ion across the membrane and the ions tendency to move relative to the membrane potential
- chemical force
- electrical force
Electrogenic pump
Example of
An active transport protein that generates voltage across a membrane while pumping ions.
Proton pump: An active transport protein in a cell ,embrace that uses ATP to transport hydrogen ions out of the cell against gradient.
Cotransport and example
The coupling where a substance moves against concentration gradient by pairing with a substance that moves with theirs.
Ex: sucrose enters paint cells by coupling to hydrogen
Bulk transport
Large molecules such as proteins and polysaccharides generally cross the membrane in bulk, packaged in vesicles.
Exocytosis
Cell secretes certain biological molecules by the fusion of vesicles with the membrane.
Endocytosis
Cell takes in molecules by forming new vesicles from the plasma membrane.
Pinocytosis
Cell continually fills droplets of extracellular fluids into tiny vesicles . It is non specific in what it transports.
Receptor mediated endocytosis
Specialized type of pinocytosis that enables cell to acquire bulk quantities of specific substances. In plasma membrane are proteins with receptor sites. Solutes nine to these and receptor proteins cluster into coated pits which form the vesicles.
Local signalling
Pacacrine:Cell secretes chemicals to specific target cells.
Synaptic signalling: Specific with nerve cells
Long distance signalling
Endocrine: uses hormones that travel through fluids in the body and act on specific cells to change cells functionality.
3 stages of cell signalling
- Reception-target cells detection of a signalling molecule. Chemical signal is detected when the signalling molecule binds to a receptor protein.
- Transduction- converts signal to a doe, that can bring about cellular response. Uses relay molecules.
- Response- transducer signal triggers cellular response
Ligand
A molecule that bonds specifically to another molecule, usually a larger one.
G protein-coupled receptor
A signal receptor protein in the plasma membrane that responds to the binding of a signalling molecule by activating a G Protein. Does this by changing GDP to GTP( like ATP). Activated G protein translocates along cell membrane to an enzyme.
Ligand-gated ion channel
A membrane receptor with a region that can act as a “gate” for ions when the receptor assures a certain shape.
Intracellular receptor proteins
Proteins in cytoplasm or nucleus of target cells. To reach a signalling molecule they go through the membrane. Molecules do this if they are hydrophobic
Protein kinase
An enzyme that transfers phosphate groups ATP to a protein.
-many relay molecules are this.
Phosphorylation cascade
A series of chemical reactions during cell signaling mediated by enzymes (kinases), in which each kinase in turn phosphylates and activates another.
(Adding phosphoryl group)
Describe the pathway of signal transduction
- A relay molecule activities protein kinase 1
- Active protein kinase activates protein kinase 2
- Active protein kinase 2 phosphorylates a protein that brings about the cells response to the signal.
- Protein phosphates catalyze the removal of phosphate groups from proteins, making them inactive.
Protein phosphatases
Enzymes that can rapidly remove phosphate groups form proteins.
Provide mechanisms for turning off signal
Second messengers
A small, non protein, water soluble molecule or ion, such as ca2+ or cyclic AMP that relays a signal to a cells interior in response to a signalling molecule bound by a single receptor protein.
