Practise AP Biology 2.5 questions by comparing membrane transport, explaining ion and water balance, and identifying how vesicles move large particles or molecules.
To investigate whether red blood cells of animals lose the ability to take in glucose from their environment as they age, scientists collected red blood cells from guinea pigs that ranged in age from one day old to seven months old. Scientists incubated an equal number of red blood cells in separate culture dishes that contained a 300 nM solution of radioactively labeled glucose. The amount of radioactively labeled glucose present inside the red blood cells of each group was measured over time.
Describe a difference between passive transport and active transport.
Questions 43-48
Figure 1. Model of synapse
Researchers investigating the regulation of neurotransmitter release from presynaptic neurons proposed a model
(Figure 1) in which CDK5, a protein expressed in axon terminals, inhibits the movement of synaptic vesicles to the
presynaptic membrane.
To test their model, the researchers used a modified version of green fluorescent protein (GFP*). In slightly
alkaline conditions, GFP* exhibits a bright green fluorescence. In acidic conditions, GFP* exhibits no fluorescence.
Using standard techniques, the gene encoding GFP* is easily introduced into living cells. By engineering the
expression of GFP* in laboratory-cultured nerve cells, the researchers found that a bright green fluorescence was
exhibited only when a presynaptic neuron was given a certain stimulus.
Based on the model, which of the following best
explains why a bright green fluorescence was
observed following stimulation of a presynaptic
neuron?
GFP* synthesis was activated when a gene
taken up by the neuron was switched on.
GFP* stored in the cytoplasm of the neuron
was packaged into synaptic vesicles.
GFP* contained in synaptic vesicles moved
into the synaptic cleft by exocytosis.
GFP* present in the synaptic cleft was
reabsorbed by endocytosis into the neuron.