Describe how the concentration of $Ca^{2+}$ in the sarcoplasmic reticulum of a muscle cell changes before, during, and after the cell is excited by a nerve impulse (action potential).

Given that $\int_{-1}^3 f(x) \space dx = 5$ and $\int_{-1}^3 g(x) \space dx = -2$, evaluate the following integrals.
a. $\int_{-1}^3 [f(x) + g(x)] \space dx$
b. $\int_{-1}^3 [g(x) - f(x)] \space dx$
c. $\int_{-1}^3 [3f(x) - 2g(x)] \space dx$

Read the editorial carefully. Use the tips for analyzing an editorial to help you answer the questions below. ATTITUDES TOWARD WATER RESTRICTIONS: Action on Tuesday by the State Water Resources Control Board to restrict lawn watering and home car-washing... barely raised eyebrows in-state. That's because most urban agencies had already imposed those kinds of limits more than a year ago. Californians responded initially with big water savings but let the hoses and sprinklers run again toward the end of last year, as the Sierra snow began to fall... This winter was a bit wetter than last, but that's not saying much. There has been too little precipitation to replenish the reservoirs and aquifers that water users have been drawing down during the dry times. There's enough water for the coming year and the year after that besides - but not at the current rate of use, and certainly not if wet winters don't resume. Stored water is a kind of bank account meant to get users through an arid year or two, but it cannot be expected to preserve the state through an extended drought like one that afflicted Australia for a decade and a half beginning in the 1990 s... In this fourth year of drought here. Californians must begin using water as though they are still at the front end of that sort of cataclysm. Australia responded to the so-called millennium drought by permanently changing the way it produces and delivers water... California has dabbled in such things for decades, but it's now evident that the state must do Australian-style rethinking and move quickly to Australia-style action. Source: Los Angeles Times. How would you frame a response to this editorial? What points would you make and how would you support them?

Why are mitochondria called the powerhouse of the cell?

Explain how a fuel-cell breathalyzer works.

Points at which the graphs of r=f(

$$\theta$$

) and r=g(\theta) intersect must be determine carefully. Solving f(\theta)=g(\theta) identifies some-but perhaps not all-intersection points. The reason is that the curves may pass through the same point for different values of

$$\theta$$

. Use analytical methods and a graphing utility to find all the intersection points of the following curves. r=1-sin

$$\theta$$

and r=1+cos

$$\theta$$

Review. The first stage of a Saturn V space vehicle consumed fuel and oxidizer at the rate of $1.50 \times 104$ kg/s with an exhaust speed of $2.60 \times 103$ m/s. (a) Calculate the thrust produced by this engine. (b) Find the acceleration the vehicle had just as it lifted off the launch pad on the Earth, taking the vehicle’s initial mass as $3.00 \times 106$ kg.

Suppose that the annual household income in a small Midwestern community is normally distributed with a mean of $\$ 55,000$ and a standard deviation of $\$ 4,500$.

a. What is the probability that a randomly selected household will have an income between $\$ 50,000$ and $\$ 65,000$ ?

b. What is the probability that a randomly selected household will have an income of more than $\$ 70,000$ ?

c. What minimum income does a household need to earn to be in the top $5 \%$ of incomes? What maximum income does a household need to earn to be in the bottom $40 \%$ of a. incomes?

Complete the following sentences: Electrons in the external circuit flow from the $_____$ electrode to the $_____$ electrode. Negative ions move in the salt bridge from the $_____$ half-cell to the $_____$ half-cell.

where is dna found in a prokaryotic cell

Earth formed ___________ years ago.

Derive an expression for the volume of a hexagonal unit cell.

Solve the given problems.

An analysis of temperature records for Sydney, Australia, indicates that the average daily temperature (in ${ }^{\circ} \mathrm{C}$ ) during the year is given approximately by $T=17.2+5.2 \cos \left[\frac{\pi}{6}(x-0.50)\right]$, where $x$ is measured in months ( $x-0.5$ is Jan. 15, etc. ). What is the daily time rate of change of temperature on March 1? (Hint: 12 months $/ 365$ days $=0.033$ month/day $-d x / d t$.)

Is the cell membrane selectively permeable or semipermeable?