#Question id: 11393
#Unit 9. Diversity of Life Forms
Given that the enzymes that catalyze nitrogen fixation are inhibited by oxygen, what are two ʺstrategiesʺ that nitrogen-fixing prokaryotes might use to protect these enzymes from oxygen?
1. couple them with photosystem II (the photosystem that splits water molecules)
2. package them in membranes that are impermeable to all gases
3. be obligate anaerobes
4. be strict aerobes
5. package these enzymes in specialized cells or compartments that inhibit oxygen entry
#Question id: 4358
#Unit 3. Fundamental Processes
Which of the following mechanisms is used to coordinate the expression of multiple, related genes in eukaryotic cells?
#Question id: 2529
#Unit 2. Cellular Organization
Cell walls commonly are classified into two major types. This classification is based not on structural or biochemical differences;
A) primary walls and
B) secondary walls
i) walls formed during cell growth
ii) walls that are formed after cell enlargement stops
iii) multilayered walls that are strengthened and waterproofed by lignin
iv) Usually they are thin and simple, but some times may be thick and multilayered, such as those found in collenchyma or in the epidermis
v) highly specialized in structure and composition, reflecting the differentiated state of the cell
Which of the following is the correctly represents features of primary and secondary walls?
#Question id: 13185
#Unit 10. Ecological Principles
#Question id: 1325
#Unit 4. Cell Communication and Cell Signaling
What is the main purpose of gap junctions?