Brown algae lack true roots but have similar structures called ____ that anchor them to their substrate
a. stipes
b. blades
c. holdfasts
d. thalli
e. rhizoids
ANSWER: c
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Polar and charged molecules typically cross the cell membrane by way of ____
a. simple diffusion b. osmosis c. filtration d. active transport e. facilitated diffusion
Most of these problems are accepted by the vast majority of reputable scientists as being
anthropogenic, or human-caused. Select the exception.
a. global warming b. decline in Atlantic cod size at maturity c. desertification of the Everglades d. background extinction rate e. deformities among whooping cranes
Scientists can determine the size of DNA fragments through a process known as gel electrophoresis. In this process, DNA is loaded into a gel submerged in a liquid buffer through which an electric current is run. Large DNA molecules move slower and can be observed at the top of the gel, whereas smaller DNA fragments move faster (and are seen at the bottom of the gel). Based on what you know about the properties of DNA, how is the electric current arranged in this process?
a. Since DNA is negatively charged, the positive end is placed at the top of the gel, and the negative end is placed at the bottom of the gel. b. Since DNA is negatively charged, the negative end is placed at the top of the gel, and the positive end is placed at the bottom of the gel. c. Since DNA is positively charged, the negative end is placed at the top of the gel, and the positive end is placed at the bottom of the gel. d. Since DNA is positively charged, the positive end is placed at the top of the gel, and the negative end is placed at the bottom of the gel. e. Since DNA is uncharged, the placement of the positive end and negative end does not matter.
Most Gram-positive bacterial cells exhibit which of the following characteristics?
A) Thick layer of peptidoglycan without teichoic acids and large periplasmic space B) Thick layer of peptidoglycan with teichoic acids and small periplasmic space C) Thin layer of peptidoglycan without teichoic acids and large periplasmic space D) Thin layer of peptidoglycan with techoic acids and a small periplasmic space