Biology: Concepts and Investigations

Mariëlle Hoefnagels

Chapter 5

Photosynthesis - all with Video Answers

Educators

Chapter Questions

Problem 1

Photosynthesis takes place in plants, algae, and some microbes. How does it affect a meat-eating animal?

Sulav Pokhrel

Sulav Pokhrel

Numerade Educator

Problem 2

What color would plants be if they absorbed all wavelengths of visible light? Why?

Sulav Pokhrel

Numerade Educator

Problem 3

Define these terms and arrange them from smallest to largest:
a. thylakoid membrane
b. chloroplast
c. reaction center
d. photosystem
e. electron transport chain

Sulav Pokhrel

Numerade Educator

Problem 4

Determine whether each of the following molecules is involved in the light reactions, the carbon reactions, or both, and explain how: $\mathrm{O}_{2}$ $\mathrm{CO}_{2},$ carbohydrate, chlorophyll $a,$ photons, NADPH, ATP, $\mathrm{H}_{2} \mathrm{O}$.

Kevin Barayuga

Numerade Educator

Problem 5

The light reactions described in this chapter are sometimes called "noncyclic photophosphorylation" because the electron transport chain that generates ATP does not return the electrons to chlorophyll. Some photosynthetic bacteria, however, generate ATP by cyclic phosphorylation. In these cells, light energy boosts chlorophyll's electrons, which pass through an electron transport chain and then return to the chlorophyll molecule. Would the light reactions of cyclic photophosphorylation produce ATP? NADPH? $\mathrm{O}_{2}$ ? Explain your
answers.

Joanna Quigley

Numerade Educator

Problem 6

Of the many groups of photosynthetic bacteria, only cyanobacteria use chlorophyll a. How does this observation support the hypothesis that cyanobacteria gave rise to the chloroplasts of today's plants and algae?

Sulav Pokhrel

Numerade Educator

Problem 7

One of the first investigators to explore photosynthesis was Flemish physician and alchemist Jan van Helmont. In the early 1600 s, he grew willow trees in weighed amounts of soil, applied known amounts of water, and noted that in 5 years the trees gained more than 45 kg. but the soil had lost only a little weight. Because he had applied large amounts of water, van Helmont concluded (incorrectly) that plants grew solely by absorbing water. What is the actual source of the added biomass? Explain your answer.

Sulav Pokhrel

Numerade Educator

Problem 8

One of the classic experiments in photosynthesis occurred in 1771 , when Joseph Priestley found that if he placed a mouse in an enclosed container with a lit candle, the mouse would die. But if he also added a plant to the container, the mouse could live. Priestley concluded that plants "purify" air, allowing animals to breathe. What is the biological basis for this observation?

Sulav Pokhrel

Numerade Educator

Problem 9

In $1941,$ biologists exposed photosynthesizing cells to water containing a heavy oxygen isotope, designated $^{18} \mathrm{O}$. The " labeled" isotope appears in the $\mathrm{O}_{2}$ gas released in photosynthesis, showing that the oxygen came from the water. Where would the $^{18}$ O have ended up if the researchers had used $^{18} \mathrm{O}$ -labeled $\mathrm{CO}_{2}$, instead of $\mathrm{H}_{2} \mathrm{O} ?$

Noah Boudrie

Numerade Educator

Problem 10

How does photorespiration counteract photosynthesis?

Sulav Pokhrel

Numerade Educator

Problem 11

When vegetables and flowers are grown in greenhouses in the winter, their growth rate greatly increases if the $\mathrm{CO}_{2}$ concentration is raised to two or three times the level in the natural environment. What is the biological basis for the increased rate of growth?

Sulav Pokhrel

Numerade Educator

Problem 12

Over the past decades, the $\mathrm{CO}_{2}$ concentration in the atmosphere has increased.
a. Predict the effect of increasing carbon dioxide concentrations on photorespiration.
b. Scientists suggest that increasing $\mathrm{CO}_{2}$ concentrations are leading to higher average global temperatures. If temperatures are increasing, does this change your answer to part (a)?

Josee Pacheco

Numerade Educator

Problem 13

How is the CAM pathway adaptive in a desert habitat?

Sulav Pokhrel

Numerade Educator

Problem 14

Explain how $C_{4}$ photosynthesis is based on a spatial arrangement of structures, whereas CAM photosynthesis is temporally based.

Kevin Barayuga

Numerade Educator

Problem 15

Explain why each of the following misconceptions about photosynthesis is false:
a. Only plants are autotrophs.
b. Plants do not need cellular respiration because they carry out photosynthesis.
c. Chlorophyll is the only photosynthetic pigment.

Noah Boudrie

Numerade Educator