Which statement is FALSE? a. according to the fluid mosaic model of membrane str
ID: 204156 • Letter: W
Question
Which statement is FALSE?
a. according to the fluid mosaic model of membrane structure, the plasma membrane consists primarily of a bilayer of mobile phospholipid molecule studded with an ever-changing mosaic pattern of proteins.
b. if 2 similar molecules can both combine wwith the same carrierm the presence of one of these molecules may decrease the rate of entry of the other
c. endocytosis can be accomplished by phagocytosis and pinocytosis
d. the sodium-potassium pump indirectly offers the energy source for glucose transport across interstinal cell
e. Carrier molecules alwasy require energy to accomplish transport of substance across the membrane.
2. Assume a hypothetical postsynaptic neuron has three presynaptic inputs: X, Y and Z. Also assume that presynaptic neuron Z is excitatory.
2a) If presynaptic neuron X is stimulated, the postsynaptic cell membrane becomes slightly hyperpolarized. What kind of a synapse is involved between presynaptic neuron X and the postsynaptic neuron?
a) Excitatory synapse.
b) Inhibitory synapse.
c) It could be either an excitatory or an inhibitory synapse.
d) Collateral axoaxonic.
e) Insufficient information is given to know what kind of synapse is involved.
2b: If presynaptic neuron Y is stimulated, the postsynaptic cell membrane becomes slightly depolarized. What kind of synapse is involved between presynaptic neuron Y and postsynaptic neuron?
a) Excitatory synapse.
b) Inhibitory synapse.
c) It could be either an excitatory or an inhibitory synapse.
d) Collateral axoaxonic.
e) Insufficient information is given to know what kind of synapse is involved.
3. choose the statement that is incorrect.
a. hormones are long-range chemical mediators secreted by endocrine glands into the blood, which carries them to distant target organs.
b. Once a steroid hormone binds with its intracellular receptor, the hormone receptor complex binds with a specific hormone response element on DNA, thereby activating a particular gene.
c. the same chemical messenger may be either a hormone or a neurotansmitter, depending on its sourse and mode of delivery to the target issue.
d. steroid hormones are derived from cholesterol
e. with dorn regulation, one hormone induces the loss of another hormone's receptors.
Explanation / Answer
1) The correct option is e. Carrier molecules always require energy to accomplish transport of substance across the membrane.
The carrier molecules has a process for the transport of molecules across the membrane that is facilitated diffusion. Faciliated difffuison is the process of transport of molecules into and out of the cell without the requirement of energy.
2.a) The correct option is a. Excitatory synapse.
An excitatory synapse is a synapse in which an action potential in presynaptic neuron, which increase the probability of an action potential occurring in post synaptic cell.
2.b) The correct option is a. Excitatory synapse.
it is also an example of excitatory synapse. Neurons from networks through which nerve impulses move, each neuron after making numerous connection with other cell.
3) The correct option is e. with down regulation, one hormone induces the loss of another hormone's receptors.
Down regulation of receptors occurs when receptors have been chronically exposed to an excessive amount of neurotransmitters, whether endogenous or drugs. This results in ligand-induced desensitization or internalization of that receptor. This causes loss of same receptor.
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