Enzymes, some hormones, and structural molecules like keratin and collagen are examples of ______________.
a. carbohydrates
b. nucleic acids
c. proteins
d. lipids
Answer: c. proteins
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Copies of chromosomes linked together at their centromeres at the beginning of meiosis are appropriately called what kind of chromatids?
A) Sister B) Daughter C) Homologous D) Mother
Of these events, the first to occur when a motor neuron stops sending an impulse to a muscle is _____.
A. the pumping of calcium ions out of the cytoplasm and back into the sarcoplasmic reticulum B. the release of myosin heads from the thin filament C. thin filaments slide back to their relaxed positions D. proteins on the thin filaments block actin's myosin-binding sites E. all of these events occur simultaneously
The earliest oxygenic phototrophs are thought to be
A. purple sulfur bacteria. B. green nonsulfur bacteria. C. purple nonsulfur bacteria. D. cyanobacteria. E. green nonsulfur bacteria AND purple nonsulfur bacteria.
Sponges feed on attached algae
Indicate whether the statement is true or false