Cell Biology & Metabolism Answer Key (Q1-16)

As the outer boundary of a cell, the plasma membrane plays an important role in maintaining the distinctive chemistry of living cells. In 1895 Charles Overton suggested that membranes must be made of lipids because hydrophobic substances readily entered and left cells. What component of membranes allows water-soluble molecules to move across them?

• Starches.

• Phospholipids

• Proteins.

• Ribonucleic acids.

• Fatty acids.

Davson and Danielli assumed that the proteins associated with membranes were hydrophilic just as their individual amino acid building blocks were. Singer and Nicolson knew that many proteins associated with membranes were very hydrophobic. What type of R-groups would be most likely to be found on the surface of an integral membrane protein?

• Ones with amine groups

• Polar

• Non-polar

• Ones with carboxylic acids

• Ones that make di-sulfide bonds

When mouse and human cells are experimentally fused, their respective proteins are confined to their own halves of the newly formed hybrid cell’s plasma membrane. After about 40 minutes however, the mouse and human proteins are totally intermingled and distributed randomly. Why are the proteins able to mix in this way?

• Because proteins are found only imbedded in the hydrophobic middle of plasma membranes.

• Because unlike “flip flopping”, lateral movement occurs very easily in plasma membranes.

• Because unlike human and yeast proteins, human and mouse proteins are indistinguishable.

• Because unlike their hydrophobic interiors, the exterior of plasma membranes are hydrophobic.

• Because proteins are distributed in an even layer on both the interior and exterior surface of plasma membranes.

Tags

NGSS.HS-LS2-3

Which of the following is the smallest unit of biological structure that meets the functional requirements of being alive?

• Organ.

• Organelle.

• Cell.

• Macromolecule.

• Cilia.

Cells were first described by Robert Hooke in 1665. Most cells can be easily visualized with light microscopes but which of the following kinds of microscopes are necessary to visualize things at a molecular level?

• Stereo optic microscopes.

• Oil immersion microscopes.

• Convex lens microscopes.

• Dissecting microscopes.

• Electron microscopes.

The earliest living things on earth are likely to have been structurally similar to present-day prokaryotes. Which of the following features that nuclei, chloroplasts and mitochondria have in common suggest that they may have each been free-living organisms that were incorporated into those primitive cells billions of years ago?

• All three have centrioles and store information in polypeptides.

• All three have centrioles and store information in nucleic acids.

• All three play similar roles and appear to share a common ancestor.

• All three have double membranes and their own set of nucleic acids.

• All three are roughly the same size and have integral membrane proteins.

Tags

NGSS.HS-LS4-1

A 1937 book by Edouard Chatton may be the first to use the terms “prokaryote” and “eukaryote”. What is the primary difference between prokaryotic and eukaryotic cells?

• Prokaryotes have lysosomes, eukaryotes do not.

• All eukaryotes are multi-cellular, prokaryotes are all unicellular.

• Eukaryotes use mitochondria to make ATP, prokaryotes use chloroplasts.

• Prokaryotes have smooth endoplasmic reticulum, eukaryotes have rough.

• Eukaryotes have internal membrane bound compartments, prokaryotes do not.

The nucleus is the information storage center of eukaryotic cells. What molecules does it harbor that causes it to have that distinction?

• Ribosomes.

• Mitochondria.

• Nucleic acids.

• Proteins.

• Glycosylated proteins.

The special form of diffusion in which water moves across a semipermeable membrane that has pores which are too small for a solute to pass through is illustrated in the image below. What is the name of this process?

• Facilitated transport.

• Tonicity.

• Osmosis.

• Active transport.

• Exocytosis.

Extractions of the DNA from eukaryotic cells usually yields a substance that is about equal part nucleic acid and tightly associated proteins that play a role in the packaging of DNA into chromosomes. What is that complex of protein and nucleic acids called?

• Ribosomes.

• Centriole bodies.

• Chromatin.

• Nucleolus.

• Histone attractors.