The PSII reaction center, also known as P680, ____.
1. absorbs light most strongly at 680nm
2. reflects light most strongly at 680nm
3. absorbs light most weakly at 680nm
4. absors light most strongly at 700nm
A. 1
How do Na+ ions enter a neuron when an action potential is initiated?
A. a voltage-gated Na+ channel
What lines the plasmodesmata?
B. the plasma membrane
What process is responsible for organelle turnover in the cell and carries out the regulated destruction of the cell's own organelles for the purpose of recycling the components of which they are made?
D. autonomy
What is the reason that C3 plants must open their stomata even when the climate is hot and dry?
a. to take in CO
b. to take in CO2 c. to take in water
d. to let CO2 out of the leaf
e. to take in O2
b. to take in CO2
With what structure is the RER often seen to be continuous, as seen by its association with ribosomes?
B. the outer membrane of the nuclear envelope
What integral membrane protein family made of two membrane-spanning chains (α and β) is involed in attaching cells to their extracellular microenvironment?
D. integrins
Which property appears to be most important in allowing cells to spread from a primary tumor into the rest of the body?
B. decreased adhesion
Lysosomal enzymes are transported from the trans golgi complex in vesicles coated with wht protein?
D. clathrin
What is caused by the inability of NA+ ion channels to open for several milliseconds after their inactivation?
E. a refractory period
What determines the direction of the Rubisco-catalyzed reaction?
C. the CO2/O2 ratio available to the enzyme
What is the distinguishing characteristic of a P-type pump?
D. It must be phosphorylated during the cycle
In general, diseases that result from a deficiency of a single lysosomal enzyme are called ___.
B. lysosomal storage disorder
Photoautotrophs include
E. all of the above
What explains the fact that plants lack the specialized junctions seen in animal cells?
D. the presence of the cell wall
How did the evolution of photosynthesis set the stage for the evolution of aerobic respiration?
A. Photosynthesis produces a waste product (oxygen) that let to the evolution of aerobic respiration.
How is a nerve impulse usually transmitted across a synapse from a presynaptic to a postsynaptic cell?
E. via a neurotransmitter
A new type of communication system has been discovered that conists of thin, highly elongated tubules capable of conducting cell-surface proteins, cytoplasmic vesicles and calcium signals from one cell to another. This system is referred to as ___.
C. tunneling nanotypes
All collagen family members consist of ___ chains arranged in a ___.
E. 3, triple helix
Which of the models below suggests that the Golgi cisternae are transient structures that form at the cis face of the stack by fusion of membranous carriers from the ER and that each cisterna travels through the Golgi complex from the cis to the trans end of the stack, changing in composition as it progresses?
E. the cisternal maturation model
What are the two sites within a cell at which protein synthesis is generally thought to occur?
C. cytosolic surface of RER and free ribosomes
Where are the enzyme that synthesize carbohydrates located?
C. stroma
A cellular phenomenon called RNA interference is a process in which cells produce small RNAs called ___ bind to specific mRNAs and inhibit the translation of these mRNAs into proteins.
A. siRNAs
Which coated vesicles move materials in a retrograde direction from the golgi stack backwards towards the ER?
B. COPI-coated vesicles
A tissue has been briefly labeled with radiolabeled amino acids. It is then transferred to a medium containing unlabeled amino acids. This can be done several times with different tissues samples for carying periods of time.
D. pulse-chase
In chloroplasts, a proton gradient is established with a higher concentration of protons found in the ___ and a lower concentration in the ___.
E. thylakoid lumen, stroma
The initial product of carbon fixation contains __ carbons, but it breaks down into two compounds containing carbons.
D. 6,3
_____ is a process that strengthens certain synapses by repeated neuron stimulation over a short time period
A. long term potentiation
The degradation of the extracellular matrix, along with cell surface proteins, is accomplished mostly by the enzyme famiy called ____.
A. matrix metalloproteinases
The light-driven splitting of a water molecule is known as _____.