Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
86 Cards in this Set
- Front
- Back
Any amphipathic phospholipid has a ____ and a ____.
|
-polar (hydrophilic) head
-nonpolar (hydrophobic) tail |
|
automatically, if you add an amphipathic lipid to water, they will form a:
|
membrane with hydrophobic tails on the inside and hydrophilic heads on the outside (near the water)
|
|
Carbohydrate tails will be found on the ____ of membranes because ____.
|
-outside
-because they function as transport molecules |
|
_____ is another lipid found in membranes.
|
Cholesterol
|
|
Cholesterol found within a membrane has a two fold purpose:
|
1. makes membrane more rigid if too fluid
2. makes membrane more fluid if too rigid |
|
3 main components of cell membranes
|
1. amphipathic lipids
2. cholesterol 3. protein |
|
Unsaturated lipids have ____ bonds and make membranes more ____ by ____.
|
-double bonds
-fluid -by disrupting the structure |
|
Heating up a membrane makes it more ____.
|
-fluid ("melts it")
|
|
Two important types of protiens:
|
1. Extrinsic (peripheral)
2. Intrinsic (integral) |
|
Extrinsic Proteins
|
-sit on outside of membrane
-bound to membrane -polar in order to bind to polar heads of membrane |
|
When embedded deep within the hydrophobic tails of the membrane, INTRINSIC proteins undergo _____ interactions.
|
-hydrophobic
|
|
When part of the INTRINSIC protein is near the polar heads of the membrane, it undergoes _____ interactions.
|
-polar
|
|
Membranes in our cells are ____, meaning they are selective to a few different kinds of molecules.
|
-semi permeable
|
|
Why do molecules go through membranes?
|
-because there is an imbalance of molecules on either side of the membrane
|
|
Thermodynamically, it is favorable to go through the membrane from high concentration to low concentration.
|
Simple Diffusion
|
|
Sometimes, despite thermodynamically good conditions, a protein is needed to aid in the process of movement across a membrane.
|
Facilitated Diffusion
|
|
For both passive facilitated diffusion and passive simple diffusion, what are the energy requirements?
|
-no energy needed
-spontaneous event that does not require any outside energy -energy is actually given off(exogonic -along gradient |
|
The movement of molecules through the membrane
|
Transport
|
|
Transport - proteins act as ____.
|
-ports
|
|
Types of Ports
|
1. uniport
2. coport a) symport b) antiport |
|
Any amphipathic phospholipid has a ____ and a ____.
|
-polar (hydrophilic) head
-nonpolar (hydrophobic) tail |
|
automatically, if you add an amphipathic lipid to water, they will form a:
|
membrane with hydrophobic tails on the inside and hydrophilic heads on the outside (near the water)
|
|
Carbohydrate tails will be found on the ____ of membranes because ____.
|
-outside
-because they function as transport molecules |
|
_____ is another lipid found in membranes.
|
Cholesterol
|
|
Cholesterol found within a membrane has a two fold purpose:
|
1. makes membrane more rigid if too fluid
2. makes membrane more fluid if too rigid |
|
Two Processes of Transport
|
1. Passive Transport
-no energy required -gives off energy(exergonic) -spontaneous event -follows [ ] gradient (high to low) 2. Active Transport -requires energy (endergonic)to move against [ ] gradient |
|
Two Types of Passive Transport
|
a) Simple Diffusion
-follows [ ] gradient b) Facilitated Diffusion -involves a carrier protein -still moves with [ ] gradient |
|
Two Types of Active Diffusion
|
a) Primary
-energy used directly: Na/K pump b) Secondary -coupled to primary: glucose symport with Na ion driven by Na/K pump |
|
Active Transport
|
-requires energy to move against a [ ] gradient
-presence of carrier protein -involves pumps -channel gated |
|
Types of Channels
|
1. Voltate-gated
2. Ligand-gated (molecule-gated) 3. Pores |
|
Steps of Primary Active Transport (Na-K Ion Pump)
|
1. ATP hydrolysis to ADP
2. Conformational change of membrane protein allows bound Na to exit cell 3. K binds to membrane protein 4.-Conformational change allows bound K to leave cell -Hydrolysis of phosphate bound to protein |
|
Net movement of pumping process
|
-transports 3 Na ions out of cell for ever 2 K ions transported into cell
-ie. 3 positive charges out and 2 negative charges in -maintains cell potential (maintains voltage between sides) |
|
There are sites on membrane protein for sodium to bind but they are only active when:
|
-a phosphate group is added to the acid group on the protein
-ie. phosphate activates sodium receptors |
|
Secondary Active Transport
|
-energy is used in a secondary step
-you must have something undergoing a primary active transport first |
|
Endocytosis
|
-process by which materials are brought into the cell when portions of a cell membrane are pinched off into the cell
|
|
Example of Endocytosis
|
-process by which LDL delivers cholesterol into the cell
-LDL receptors on cell membrane surface -LDL binds -cell membrane engulfs LDL & pushes it within cell -LDL particle is broken down & releases contents (triglycerides) within cell -cholesterol has gained access to inside of cell |
|
Oversupply of cholesterol inhibits:
|
-synthesis of LDL receptor proteins on cell membrane surface
|
|
Exocytosis
|
-the process by which materials exit the cell by the pinching off of part of the cell membrane
|
|
Allosteric
|
-the property of multisubunit proteins such that a conformational change in one subunit induces a change in another subunit
|
|
Kinase
|
-an enzyme that transfers a phosphate group to some other molecule (it phosphorylates)
|
|
Receptor Proteins
|
-portion on outside of cell
-usually has a polysaccharide -can recognize foreign molecule, bind to it and then do something to it -must transmit info. from outside of cell to inside -does this via change in conformation of cell |
|
Enzyme
|
-on portion of receptor protein that is inside of cell
-when change in conformation occurs, the receptor protein directly activates the enzyme |
|
Enzymes come in two flavors:
|
1. Active - phoshorylated
2. Inactive - not phosphorylated |
|
G protein
|
-bound to portion of receptor protein that is on inside of cell
-always bound to receptor either in active (GTP) or inactive (GDP) form |
|
Inactive form of G protein
|
-GDP = guanidine diphosphate
|
|
Active form of G protein
|
-GTP = guanidine triphosphate
-made upon phosphorylation of GDP |
|
G protein can stimulate the production of another messenger:
|
-secondary messenger, which is inside the cell
-cAMP, IP3, DAG, Ca2++ |
|
Primary Receptor
|
-hormone that binds to receptor protein on outside of cell
|
|
Secondary Receptor
|
-hormone that binds to receptor on inside of cell
-directly stimulates another enzyme |
|
Unique characteristic of the active form of G protein (GTP)
|
-it is its own enzyme
-it can shut itself off: the enzyme built into its own subunit hydrolyzes it to GDP to turn off signal transduction |
|
Adenylate Cyclase
|
-produces secondary messenger, cAMP, when bound to G protein
|
|
Adenylate Cyclase is only active when:
|
-it is bound to G protein
|
|
cAMP
|
-a kinase
-has pairs of subunits: c & r -causes phosphorylation of ATP to ADP - |
|
cAMP:
a) c subunit b) r subunit |
a) c subunit catalyzes
b) r subunit acts as receptors |
|
phosphotase
|
-enzyme that helps dephosphorylate
|
|
kinase
|
-enzyme that helps phosphorylate
|
|
Activation of protein by replacement of GDP with GTP results in production of ___.
|
phospholipase
|
|
Calcium is bound to its own carrier protein:
|
-calmodulin: picks up calcium ion and transports it around
|
|
Holoenzyme
|
-total enzyme
|
|
Apoenzyme
|
-protein: active site, etc.
-an enzyme that consists of polypeptide chains alone |
|
Coenzyme
|
-coreactant
-actual reactant -prosthetic group or co-factor |
|
Enzymes: Structure
|
1. Holoenzyme
2. Apoenzyme 3. Coenzyme 4. Metal ions |
|
Metal Ions
|
-M++: usually co-factors, no heavy metals
|
|
Subdivisions of Coenzymes: two different states
|
a) prosthetic group - enzyme that is bound firmly to protein
b) cofactor - enzyme that is loosley bound to protein |
|
Co-factors can be metal ions:
|
calcium, magnesium, manganese
|
|
What determines the rate of a chemical reaction?
|
1. Temperature
2. pH 3. Concentration of Enzyme 4. Concentration of Substrate |
|
First Order Reaction Rates
|
-rate of reaction is directly related to concentration of reactants
|
|
Zero Order Reaction Rates
|
-rate of reaction is constant (plateau)
|
|
Plateau results from:
|
-the occurence of saturation
(hyperbolic curve) |
|
Saturation
|
-the molecule cannot go any faster than rate at plateau
|
|
Induced Enzyme Concentration
|
-when concentration of enzyme in body is low, a signal sent to brain causes production of more enzyme and vice versa
|
|
Three things that must happen for two molecules to react:
|
1. collision
2. collisions must be of proper orientations 3. collisions must have sufficient energy to undergo bond making/breaking |
|
Competitive Inhibition
|
-substrate & competitive inhibitor both fit into active site
-higher substrate [ ] to yield same rate as noncompetitive inhibition -max. rate is the same |
|
Noncompetitive Inhibition
|
-inhibitor does not fit into active site
-must bind somewhere else on molecule |
|
Oxidation
|
-loss of protons (H+)
|
|
Reduction
|
-gain of protons (H+)
|
|
coenzyme A
|
-identify active form of co-A by sulfer group
-active form is also attached to fatty acid group -sulfer reacts with a fatty acid to make acyl-coA |
|
Dehydrogenases
|
-enzymes that can catalyze oxidation/reduction reactions
|
|
NAD+
|
-oxidized form
|
|
NADH
|
-reduced form
|
|
FAD+
|
-oxidized form
|
|
FADH
|
-reduced form
|
|
NAD removes ___ H ions at a time while FAD removes ___ H ions at a time.
|
-one
-two |
|
FAD is used to remove:
|
-a double bond
-removing an H ion on each side of double bond -lipid metabolism needs double bond formation |
|
Molecule which has an "energetic" bond
|
ATP
|
|
ATP
|
-if you chop off a phosphate group, you get energy
-sometimes ATP gives off only one phosphate group but usually it gives off two |