2025 BIO 251 Exam 1 New Latest Version Best
Studying Material with All Questions and
Correct Answers
The influx of calcium into the axon terminal of a chemical synapse is responsible for which of
the following? ------------- Correct Answer ------------ release of neurotransmitter from the axon
terminal
What creates the DNA backbone? ------------ Correct Answer ------------- deoxyribose sugar and
phosphate
How many amino acids are there? ------------ Correct Answer ------------- our bodies use 20
different amino acids to make the peptides and proteins in our bodies
How is protein formed? ------------ Correct Answer ------------- amino acids are linked together
by a peptide bond (more than 50 amino acids)
The depolarization phase (phase 1) of the action potential is generated by a rapid ____________.
------------- Correct Answer ------------ opening of sodium channels
Which of the following accurately describes afferent neurons? ------------- Correct Answer -------
----- They transmit information from the periphery to the CNS
On what portion of the neuron do action potentials propagate? ------------- Correct Answer --------
---- axon
What type of cell produces the myelin covering the axons of neurons in the central nervous
system, i.e., the brain and spinal cord? ------------- Correct Answer ------------ oligodendrocyte
Which statement best describes how graded potentials determine whether an action potential will
be generated or not? ------------- Correct Answer ------------ when an excitatory depolarization
reaches threshold at the axon hillock
Communication across a chemical synapse is initiated by the release of a neurotransmitter from
the __________ region of a neuron. ------------- Correct Answer ------------ axon terminal
The neurotransmitter that is released from the presynaptic neuron must diffuse across the
_____________ to reach its receptor on the postsynaptic neuron. ------------- Correct Answer ----
-------- synaptic cleft
Differences in the rate of opening between fast and slow gated ion channels is caused by
______________. ------------- Correct Answer ------------ G protein activity slightly slowing the
opening of slow channels
,Regarding the transport of ions across cell membranes, what type of on channels behave as
though they are always open and constantly allows ions to move across the membrane? -----------
-- Correct Answer ------------ leak channels
The concentration gradient for sodium across the axon membrane of neurons is such that the net
movement for sodium is directed _______________, thereby causing the cell's membrane
potential to become more ___________. ------------- Correct Answer ------------ inward : positive
The repolarization phase (phase 2) of action potentials in neurons is due primarily to
___________. ------------- Correct Answer ------------ potassium flow out of the cell
During which of the following states of the action potential are the gated sodium channels closed
and incapable of opening? ------------- Correct Answer ------------ during the absolute refractory
period
How can action potentials relay information about the intensity of a stimulus, such as
distinguishing between a warm and hot skin temperature? ------------- Correct Answer ------------
due to the frequency of action potentials
As an action potential is propagated away from the axon hillock, why does propagation continue
in only one direction? ------------- Correct Answer ------------ The region just behind the action
potential is in the absolute refractory period
True or False. The binding of a neurotransmitter to its receptor at an inhibitory synapse produces
a depolarization of the membrane potential of the post-synaptic neuron, thus bringing it close to
threshold. ------------- Correct Answer ------------ False
The basic units of life which are capable of carrying out their own life functions are
___________. ------------- Correct Answer ------------ cells
Which body tissue is specialized to form a barrier between the body and the external
environment; this tissue also lines hollow organs within the body? ------------- Correct Answer ---
--------- epithelial tissue
What body tissue is specialized for generating and transmitting electrical signals? -------------
Correct Answer ------------ nervous
Total body water is composed of ____________. ------------- Correct Answer ------------ both
intracellular (ICF) and extracellular (ECF) fluid
Which of the following compartments contain most of the water found in the human body? ------
------- Correct Answer ------------ intracellular fluid (ICF)
Homeostasis is a term which describes the proceses whereby the body ____________. ------------
- Correct Answer ------------ maintains a constant internal environment
, Which of the following statements about homeostasis is FALSE? ------------- Correct Answer ----
-------- The primary mechanism to maintain homeostasis is positive feedback.
In most homeostasis mechanisms, a __________ detects a change in a regulated variable and
sends that information to a(n) ____________ which relays signals to a(n) ______________,
usually a muscle or a gland, to bring about a change in the body. ------------- Correct Answer -----
------- sensor : integrating center : effector
Direct communication between cells in contact with one another is accomplished through
__________. ------------- Correct Answer ------------ gap junctions
Which of the following is NOT a type of membrane transport protein? ------------- Correct
Answer ------------ an intracelluar receptor for a chemical messenger
What is the mode of action of a chemical messenger that is released into the bloodstream so that
it can affect target cells throughout the body? ------------- Correct Answer ------------ endocrine
Transporting a substance against its concentration gradient, i.e., from low concentration to high
concentration, requires ____________. ------------- Correct Answer ------------ a transporter that
uses metabolic energy
When molecules are passively transported across a membrane, the direction of their movement is
dictated by the molecule's tendency to move ____________. ------------- Correct Answer ----------
-- from higher concentration to lower concentration
Which of the following transport mechanisms requires energy?
A) facilitated diffusion only
B) primary active transport only
C) secondary active transport only
D) both primary and secondary active transport
E) both primary active transport and facilitated diffusion ------------- Correct Answer ------------
D) both primary and secondary active transport
What type of ion channels continually remain in their open configuration and allow ions to
constantly move across the membrane? ------------- Correct Answer ------------ leak channels
Which of the following cell membrane transport mechanisms is passive?
A) the symporter for the cotransport of glucose with sodium (Na+)
B) transport of sodium (Na) and potassium (K*) across the membrane by the Nat+/ K+ pump
(Na+/K+ ATPase)
C) movement of sodium (Na+) through ion channels
D) the antiporter for the countertransport of hydrogen ions with sodium
E) movement of calcium via a Ca-ATPase (Ca2+ pump) ------------- Correct Answer ------------
C) movement of sodium (Nat) through ion channels
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