Cell Signaling
Which of the following is true of G protein-coupled receptors (GPCRs)?
a. they phosphorylate proteins directly
b. they form dimers upon ligand binding
c. they use second messengers to relay signals
d. they bind DNA directly
C. they use second messengers to relay signals
The trp operon is an example of a __________ operon, turned off when tryptophan is abundant
Repressible
_________________ _ feedback loops help maintain homeostasis by counteracting changes from a set point.
Negative
The refractory period ensures that action potentials only travel in ________ direction along the axon.
one
The _______________ ear contains the cochlea, responsible for converting sound waves to nerve signals.
inner
Second messengers such as ____________ and ___________ are crucial in many intracellular signaling pathways.
cAMP and Ca2+
Which of the following occurs due to DNA methylation?
A. Increased transcription
B. Decreased transcription
C. Enhanced mRNA stability
D. Increased histone acetylation
B. Decreased transcription
Water-soluble hormones require _________________ ____ to transmit their signal inside the cell.
membrane receptors
What is the immediate result of Na⁺ influx during an action potential?
A. Repolarization
B. Hyperpolarization
C. Depolarization
D. Resting potential maintenance
C. Depolarization
Which receptor type is primarily responsible for detecting mechanical pressure?
A. Chemoreceptor
B. Mechanoreceptor
C. Thermoreceptor
D. Photoreceptor
B. Mechanoreceptor
Which step in a signal transduction pathway most often amplifies the signal?
A. Ligand binding
B. G protein activation
C. Phosphorylation cascade
D. Transcriptional response
C. Phosphorylation Cascade
What would happen to the lac operon if lactose is present but the repressor is mutated and cannot bind the operator?
A. The operon will stay off
B. The operon will be expressed
C. CRP will bind and repress the operon
D. RNA polymerase cannot bind
B. The operon will be expressed
Which hormone helps regulate calcium levels by increasing uptake in bones?
A. Calcitonin
B. Parathyroid hormone (PTH)
C. Aldosterone
D. Glucagon
A. Calcitonin
Which part of the neuron receives incoming signals from other neurons?
a. axon
b. axon terminal
c. dendrites
d. myelin sheath
C. Dendrites
Which structure in the retina is responsible for high-acuity color vision?
A. Optic nerve
B. Rod cells
C. Fovea
D. Iris
C. Fovea
Intracellular receptors typically act as _________________ _______ when bound to steroid hormones.
Transcription Factors
In eukaryotes, gene regulation at the transcription level often involves enhancers binding____________ _____________.
Transcription factors
A person with hypersecretion of cortisol may have dysfunction in which part of the hormone cascade?
A. Posterior pituitary
B. Anterior pituitary
C. Adrenal medulla
D. Thyroid gland
B. Anterior pituitary
At a chemical synapse, neurotransmitters are released from the ________________ of the presynaptic neuron.
Axon Terminal
In skeletal muscle contraction, Ca²⁺ binds to ______________, which exposes binding sites on actin.
Troponin
Compare signal transduction through RTKs versus GPCRs.
RTKs dimerize and phosphorylate target proteins; GPCRs activate G proteins and second messengers.
Describe how alternative splicing can increase protein diversity from a single gene.
Alternative splicing allows different combinations of exons to be joined together from the same premRNA, producing multiple distinct proteins from a single gene.
Explain how the hypothalamus and anterior pituitary interest to control hormone cascades
The hypothalamus releases releasing hormones that stimulate the pituitary to release tropic hormones affecting other glands
Briefly describe the steps involved in transmitting an action potential along a neuron's axon.
The neuron is first depolarized when voltage-gated Na⁺ channels open and Na⁺ enters. This depolarization triggers nearby channels to open, propagating the signal down the axon. K⁺ channels then open to repolarize the membrane. In myelinated axons, the signal "jumps" between nodes of Ranvier in a process called saltatory conduction.
Describe the sliding filament model of muscle contraction and the role of ATP.
Myosin binds actin and pulls it; ATP detaches and resets myosin for further contraction.