Describe three features distinguishing prokaryotic cells from eukaryotic cells: (a) _____ (b) _____ (c) _____

An electric catfish can generate a significant potential difference using stacks of special cells called electrocytes. Each electrocyte develops a potential difference of $110 \mathrm{mV}$. How many cells must be connected in series to give the 350 V a large catfish can produce?

Write three ways in which cancer cells differ from normal cells.

Fura-2 is not effective for the study of calcium levels in intact, living cells. On the basis of how Fura-2 is depicted on p. 410, why is it ineffective?

Word Issue How many chromosomes will each cell have if a dog's $(2 n=78)$ cells go through meiosis and mitosis, respectively?

Phenylalanine is required for the production of many bodily proteins, but none of your cells are capable of synthesizing this essential amino acid. What type of metabolic pathway must be responsible for providing phenylalanine to your cells? How would your diet affect the amount of phenylalanine that is available?

A solar cell, 3.0 cm square, has an output of 350 mA at 0.80 V when exposed to full sunlight. A solar panel that delivers close to 1.0 A of current at an emf of 120 V to an external load is needed. How many cells will you need to create the panel? How big a panel will you need, and how should you connect the cells to one another? How can you optimize the output of your solar panel?

A solar cell, $3.0 \mathrm{~cm}$ square, has an output of $350 \mathrm{~mA}$ at $0.80 \mathrm{~V}$ when exposed to full sunlight. A solar panel that delivers close to $1.3 \mathrm{~A}$ of current at an emf of $120 \mathrm{~V}$ to an external load is needed. How many cells will you need to create the panel? How big a panel will you need, and how should you connect the cells to one another?

Given these events:

(1) Bipolar cells depolarize.

(2) Glutamate release from presynaptic terminals of photoreceptor cells decreases.

(3) Light strikes photoreceptor cells.

(4) Photoreceptor cells are depolarized.

(5) Photoreceptor cells are hyperpolarized.

Choose the arrangement that lists the correct order of events, starting with the photoreceptor cells in the resting, nonactivated state.

a. 1,2,3,4,5

b. 2,4,3,5,1

c. 3,4,2,5,1

d. 4,3,5,2,1

e. 5,3,4,1,2

a. What is a machine? b. In what three ways can machines make work easier? c. How does a screwdriver make work easier?

Identify ten devices that use cells or batteries. What types of cells or batteries are used in each device? Are the cells or batteries used the best choice? Explain.

_____________ Vessel element A. the main phloem cells B. phloem cells that surround sieve tube elements C. xylem cells arranged end to end on top of one another

Brutus, a champion weightlifter, raises 240 kg of weights a distance of 2.35 m. a. How much work is done by Brutus lifting the weights? b. How much work is done by Brutus holding the weights above his head? c. How much work is done by Brutus lowering them back to the ground? d. Does Brutus do work if he lets go of the weights and they fall back to the ground? e. If Brutus completes the lift in 2.5 s, how much power is developed?

Choose the best answer.

Which of these cells in a flowering plant is apt to be nonliving?

a. parenchyma

b. collenchyma

c. sclerenchyma

d. epidermal cells

e. guard cells