Living systems are incredibly in diverse in size, shape, environment, and behavior. It is estimated that there are between 10 million and 100 million different species. Despite this wide variety of organisms, it remains difficult to define what it means to say something is alive. Which of the following can be described as the smallest living unit?
A virus is a living organism
False, a virus lacks full machinery required to copy itself and is therefore not considered a living organism
Cells of different types can have different chemical requirements
A human white blood cell is larger than a Paramecium cell
False, A human white blood cell is about 10 mm in diameter. The single-celled paramecium is roughly 10 times that size
The flow of genetic information is controlled by a series of biochemical reactions that result in the production of proteins, each with its own specific order of amino acids. Choose the correct series biochemical reactions from the options presented here
replication, transcription, translation
Proteins are important architectural and catalytic components within the cell, helping to determine its chemistry, its shape, and its ability to respond to changes in the environment. Remarkably, all of the different proteins in a cell are made from the same 20_____. By linking them in different sequences, the cell can make protein molecules with different conformations and surface chemistry, and therefore different functions.
Changes in DNA sequence from one generation to the next may result in offspring that are altered in fitness compared with their parents. The process of change and selection over the course of many generations is the basis of___________
What unit of length would you generally use to measure a typical human cell?
Uses a light microscope with an optical component to take advantage of the different refractive indexes of light passing through different regions of cell
Employs a light microscope and requires that samples be fixed and stained in order to reveal cellular details
Requires the use of two sets of filters. The first filter narrows the wavelength range that reaches the specimen and the second blocks out all wavelengths that pass back up to the eyepiece except for those emitted by the dye in the sample
Scans the specimen with a focused laser beam to obtain a series of two-dimensional optical sections, which can be used to reconstruct an image of the specimen in three-dimensions. The laser excites a fluorescent dye molecule, and the emitted light from each illuminated point is captured through a pinhole and recorded by a detector
Has the ability to resolve cellular components a small as 2 nm
Requires coating the sample with a thin layer of a heavy metal to produce three-dimensional images of the surface of a sample
The __________ __________ is made up of two concentric membranes and is continuous with the membrane of the endoplasmic reticulum
The nucleus, an organelle found in eucaryotic cells, confines the __________, keeping them separated from other components of the cell.
Which of the following organelles has both an outer and an inner membrane
Mitochondria contain their own genome, are able to duplicate, and actually divide on a different timeline from the rest of the cell. Nevertheless, mitochondria cannot function for long when isolated from the cell because they are
Photosynthesis enables plants to capture the energy from sunlight. In this essential process, plants incorporate the carbon from CO2 into high-energy __________ molecules, which the plant cell mitochondria use to produce ATP
The cell constantly exchanges materials by bringing nutrients in from the external environment and shuttling unwanted by-products back out. Which term describes the process of by which external materials are captured inside vesicles and brought into the cell?
____________ are fairly small organelles that provide a safe place within the cell to carry out certain biochemical reactions that generate harmful, highly reactive oxygen species. These chemicals are both generated and broken down in the same location
The cytoskeleton provides support, structure, motility, and organization, and it forms tracks to direct organelle and vesicle transport. Which of the cytoskeletal elements listed below is the thickest?
Despite the differences between eukaryotic and prokaryotic cells, procaryotes have proteins that are distantly related to eukaryotic actin filaments and microtubules. What is likely to be the most ancient function of the cytoskeleton?
Protozoans are single-celled eukaryotes with cell morphologies and behaviors that can be as complex as those of some multi-cellular organisms
Animal, plant, fungal, and bacterial cells all possess cell walls
False, The outermost layer in animal cells is the plasma membrane.
Primitive plant, animal, and fungal cells probably acquired mitochondria after they diverged from a common ancestor
False, The mitochondria in modern plant, animal, and fungal cells are very similar, implying that these lines diverged after the mitochondrion was acquired by the ancestral eucaryote
Biologists cannot possibly study all living species. Instead, they try to understand cell behavior by studying a select subset of them. Which of the following characteristics are useful in an organism chosen for use as a model in laboratory studies?
amenability to genetic manipulation, ability to grow under controlled conditions, rapid rate of reproduction
Many of the mechanisms that cells use for maintenance and reproduction were first studied at the molecular detail in bacteria. Which bacterial species had a central role in advancing the field of molecular biology?
Brewer's yeast, apart from being an irreplaceable asset in the brewery and in the bakery, is an experimental organism used to study eukaryotic cells. However, it does face some limitations. Which of the processes below cannot be studied with yeast
A. thaliana, or Arabidopsis, is a common weed. Biologists have selected it over hundreds of thousands of other flowering plant species to serve as a experimental model organism because____________.
it can reproduce in 8-10 weeks
Drosophila melanogaster is a/an_______. This type of animal is the most abundant of all animal species, making it an appropriate choice as an experimental model
Zebrafish (Danio rerio) are especially useful in the study of early development because their embryos ________
You wish to explore how mutations in specific genes affecting sugar metabolism might alter tooth development. Which organism is likely to provide the best model system for your studies and why?
Mice, Mice are likely to provide the best model system. Mice have teeth and have long been used as a model organism. Mice reproduce relatively rapidly and the extensive scientific community that works with mice has developed techniques to facilitate genetic manipulations. E. coli (a bacterium) and Arabidopsis (a plant) do not have teeth. Horses like sugar and have big teeth, but they would not be a good model organism. There is not an extensive scientific community working on the molecular and biochemical mechanisms of cell behaviors in horses; they are expensive and have a long reproduction time, which makes genetic studies costly and slow; and tools for genetic manipulation (other than traditional breeding) have not been developed.
In what way does a fungal cell structurally resemble a plant cell, rather than an animal cell?
rigid cell wall
What principal organelle does a plant cell contain that a fungal cell does
formation of the endoplasmic reticulum
how the actin cytoskeleton contributes to cell shape
how cells decode their genetic instructions to make proteins
how mitochondria get distributed to cells during cell division