Chapter 1

Question 1

Function of cell wall

Answer 1

Provides structural support to a cell; permits a cell to have turgor pressure and a particular shape; protects a cell from drying out; Animal cells do NOT have a cell wall

Question 2

Function of Plasma membrane

Answer 2

A selectively permeable barrier that allows a cell to control what substances flow in and out of the cell.

Question 3

Function of Ribosomes

Answer 3

A multisubunit complex of RNA and proteins that uses an RNA template to direct synthesis of a protein.

Question 4

Function of Flagellum

Answer 4

A rod shaped structure that rotates to move a cell forward. Not all prokaryotes have a flagellum. Some protozoans have a flagellum or flagella (more than one). The sperm of animals and some plants have a flagellum.

Question 5

Function of Mitochondrion

Answer 5

An organelle that generates much of a cell’s ATP by the processes of oxidative respiration: citric acid cycle, e- transport, proton electrochemical gradient, ATP.

Question 6

Function of Peroxisome

Answer 6

An organelle for chemical reactions that generate reactive oxygen species such as hydrogen peroxide, which is then degraded in the peroxisome.

Question 7

Function of Lysosome

Answer 7

An organelle for intracellular digestion of food particles brought into the cell by endocytosis or digestion of damaged mitochondria. In plants, the equivalent organelle is called a vacuole.

Question 8

Function of Endoplasmic reticulum (ER)

Answer 8

-Secreted proteins are synthesized into the lumen of the ER.

Question 9

Function of Golgi apparatus

Answer 9

An organelle that chemically modifies materials and sorts materials delivered to it by vesicles coming from the ER.

Question 10

Function of Intermediate filament

Answer 10

A static protein filament that strengthens a cell mechanically to protect the cell from compression and tension forces.

Question 11

Function of Microtubule

Answer 11

A dynamic (grows and shrinks) protein filament that provides ‘tracks’ on which vesicles can be moved in one direction. Microtubules also help separate chromosomes during mitosis.

Question 12

Function of Actin filament

Answer 12

Another type of dynamic protein filament that provides a cell with the ability to contract

Question 13

Function of Nucleus

Answer 13

An organelle that stores most of a cell’s genetic information, and is where the first step of genetic expression happens: transcription, making RNA copies of selected genes (coding portions of the DNA).

Question 14

Function of Nucleolus

Answer 14

A distinct region, in the nucleus, where parts of ribosomes are assembled.

Question 15

Function of Centrosome with centrioles

Answer 15

A site where microtubule growth is initiated. Plants do

NOT have centrosomes. Centrioles are a short array of microtubules.

Question 16

Function of Extracellular matrix

Answer 16

Fibers and other materials that are secreted, by a cell, and form a cell wall (plants) or gel-like matrix (animals).

Question 17

Make a labeled sketch of a prokaryotic cell and a eukaryotic cell that shows the fundamental organization.

Answer 17

See Panel 1-2

Question 18

All cells share very similar “machinery for the most basic functions”

Answer 18

1) glycolysis and citric acid cycle are at the core of metabolism for generating ATP and intermediates for biosynthesis of amino acids, sugars (saccharides/carbohydrate), nucleotides and lipids;
2) the bulk of cell structure is in macromolecules: proteins built from amino acids, nucleic acids built from nucleotides, polysaccharides built from monosaccharides, and phospholipids that make up all the membrane bilayers;
3) DNA (deoxyribonucleic acid) is the genetic information; genes are copied into RNA (ribonucleic acid); RNA copies are used by ribosomes to direct synthesis of proteins; many different proteins are then the mechanisms that account for cell behaviors;
4) a selectively permeable membrane (lipid bilayer plus embedded proteins) separates the inside of the cell from the outside, and in eukaryotes separates the internal compartments called organelles.

Question 19

If the resolution of the unaided human eye is ~ 0.2 mm (200 um), then a) what magnification is needed to see a typical plant or animal cell?

Answer 19

a typical plant or animal cell ~ 10X to 100X magnification;

light microscopy and
often thin sections and dyes, or individual cells in culture

Question 20

If the resolution of the unaided human eye is ~ 0.2 mm (200 um), then a) what magnification is needed to see a typical prokaryotic cell?

Answer 20

a typical prokaryotic cell ~ 1000X; light microscopy of cells in culture; if on plant or animal tissue, then need a thin section and a dye or probe specific to the bacteria

Question 21

If the resolution of the unaided human eye is ~ 0.2 mm (200 um), then a) what magnification is needed to see a mitochondrion?

Answer 21

~ 1000X; fluorescence microscopy with a fluorescent probe specific to mitochondria; or electron microscopy of thin sections at ~ 10,000X to see internal structure of mitochondria

Question 22

If the resolution of the unaided human eye is ~ 0.2 mm (200 um), then a) what magnification is needed to see a chloroplast?

Answer 22

chloroplasts are little bigger than mitochondria, ~ 100X - 1000X; light microscopy of thin leaves; chloroplasts have much of a pigment called chlorophyll that reflects green light, so chloroplasts appear green and no dyes or probes are needed

Question 23

If the resolution of the unaided human eye is ~ 0.2 mm (200 um), then a) what magnification is needed to see a ribosome?

Answer 23

~ 100,000X; transmission electron microscopy of thin sections

Question 24

If the resolution of the unaided human eye is ~ 0.2 mm (200 um), then a) what magnification is needed to see the plasma membrane?

Answer 24

~ 100,000X; transmission electron microscopy of thin

sections

Question 25

If the resolution of the unaided human eye is ~ 0.2 mm (200 um), then a) what magnification is needed to see a DNA fiber?

Answer 25

~ 100,000X; transmission electron microscopy of isolated DNA or thin sections with a probe specific to DNA

Question 26

If the resolution of the unaided human eye is ~ 0.2 mm (200 um), then a) what magnification is needed to see the surface details of a cell?

Answer 26

~ 1000X; scanning electron microscopy

Question 27

If the resolution of the unaided human eye is ~ 0.2 mm (200 um), then a) what magnification is needed to see microtubules?

Answer 27

~ 1000X; fluorescence microscopy with a fluorescent probe specific
to microtubules

Question 28

If the resolution of the unaided human eye is ~ 0.2 mm (200 um), then a) what magnification is needed to see the location of a specific protein in a cell?

Answer 28

~ 1,000,000X; transmission electron microscopy of thin sections stained with a probe specific to the protein

Question 29

Imagine you have engineered a fluorescent protein that is secreted, so you can watch, using a microscope, as it is synthesized and secreted out of the cell.

You start with the gene turned off [not being expressed].

You give the cell a signal that turns the gene on [expression starts].

Choose which compartments will fluoresce and place them in order of first to last to fluoresce. Compartments: extracellular matrix, vesicles, endoplasmic reticulum, mitochondria, nucleus, golgi apparatus, cytosol, lysosome

Answer 29

Endoplasmic reticulum, vesicles, golgi apparatus, extracellular matrix

A protein that will be secreted is first synthesized directly into the lumen of the endoplasmic reticulum.

The protein is then gathered into a vesicle. The vesicle moves (using a motor protein that ‘walks’ along a microtubule) to the cis-face of the golgi apparatus, fuses with it, and releases its contents into the lumen of the cis-face.

The protein is then gathered into a vesicle that moves to the next sac (cisternae) in the stack, fuses, and releases contents.

The process continues moving the protein sequentially through the stack of sacs until gathered into a vesicle budding off the trans-face.

The vesicle then moves to the plasma membrane, where it fuses and releases the protein into the extracellular matrix.

Question 30

Imagine you have engineered a fluorescent protein that is secreted, so you can watch, using a microscope, as it is synthesized and secreted out of the cell. You give the cell a signal that turns the gene on [expression starts] AND a chemical that prevents vesicles from forming.
List the cell compartment(s) that you expect will fluoresce.

Answer 30

Endoplasmic reticulum. As above, the protein is synthesized directly into the lumen of the endoplasmic reticulum. However, the chemical prevents vesicles from forming, so the next step in the flow of the secretion pathway is blocked. The protein accumulates inside the endoplasmic reticulum.
Knowing the flow, chain of events, of a process helps predict the consequence of a drug, ecological molecule or mutation that alters an interface (step) in the chain of events (pathway). At least the consequence at the cellular level, but then one needs to know what cell behavior the process influences, and how the cell behavior contributes to organ function to figure out the consequence to the individual.

Question 31

Which of the following do you expect to find in all cells, prokaryotes and eukaryotes?

Enzymes for glycolysis Proteins
Polysaccharides
Chlorophyll Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) Macromolecules Transcription
Translation
Lipids
Nucleus
ATP
Membrane-bound organelles Microtubules
Plasma membrane
Endoplasmic reticulum

Answer 31

Enzymes for glycolysis Proteins
Polysaccharides
Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA) Macromolecules Transcription
Translation
Lipids
ATP
Plasma membrane

Question 32

Cdc2 is a protein needed by yeast cells to complete cell division. Yeast cells with a mutant allele that encodes a nonfunctional Cdc2 fail to divide. Researchers inserted, into the mutant yeast genome, a human gene encoding the human equivalent to Cdc2. The transgenic yeast divided normally.

Does this result surprise you?

Answer 32

It surprised me when I was first learning biology. There is much shared by all eukaryotes, including many of the genes encoding proteins that regulate the events of
cell division. The genes and proteins between two species are not identical, but have much similarity and often the same function.
All eukaryotes, and prokaryotes, use the same genetic code, which is the relation between RNA sequence (copy of DNA) and amino acid sequence. So DNA from a gene in one eukaryote moved into another eukaryote will be transcribed and translated properly.
Eukaryote genes can also be properly expressed in prokaryotes if the introns are removed.

Question 33

You are watching a eukaryotic cell with a microscope. You notice numerous spherical objects (diameter ~ 0.1 to 1 um) moving in a line in one direction: towards the plasma membrane.

How can these cellular objects be organized in a line and moving in one direction?

Answer 33

Vesicles and other organelles bounce around the cell randomly, unless attached (binding) to a motor protein that uses ATP to do the work of ‘walking’ in one direction along a microtubule or actin filament. The fact that the objects are in a line, and moving in one direction, suggests motor proteins walking on the same filament are actively moving the objects.

Question 34

What are the arguments that all living cells evolved from a common ancestor cell? Imagine the very early days of evolution of life on Earth. Would you assume that the primordial ancestor cell was the first and only cell to form?

Answer 34

There are many lines of evidence for a common ancestor. Analyses of modern-day living cells show an amazing degree of similarity in the basic components that make up the inner workings
of otherwise vastly different cells. Many metabolic pathways, for example, are conserved from one cell to another, and the compounds that make up nucleic acids and proteins are the same in all living cells, even though it is easy to imagine that a different choice
of compounds (e.g., amino acids with different side chains) would have worked just as well. similarly, it is not uncommon to nd that important proteins have closely similar detailed structures in procaryotic and eucaryotic cells. Theoretically, there would be many different
ways to build proteins that could perform the same functions. The evidence overwhelmingly shows that most important processes were “invented” only once and then became ne-tuned during evolution to suit the particular needs of specialized cells.
It seems highly unlikely, however, that the rst cell survived to become the primordial founder cell of today’s living world. As evolution is not a directed process with a purposeful progression, it is more
likely that there were a vast number of unsuccessful
trial cells that replicated for a while and then became extinct because they could not adapt to changes in the environment or could not survive in competition with other types of cells. we can therefore speculate that the primordial ancestor cell was a “lucky” cell that ended up in a relatively stable environment in which it had a chance to replicate and evolve.

Question 35

Which of the following statements are correct? Explain your answers.
A. The hereditary information of a cell is passed on by its proteins.

Answer 35

A. False. The hereditary information is encoded in the cell’s DNA, which in turn specifies its proteins.

Question 36

Which of the following statements are correct? Explain your answers.
C. Plants are composed of prokaryotic cells.

Answer 36

C. False. Plants are composed of eucaryotic cells that
contain chloroplasts as cytoplasmic organelles. The chloroplasts are thought to be evolutionarily derived from procaryotic cells.

Question 37

Which of the following statements are correct? Explain your answers.

D. All cells of the same organism have the same number of chromosomes (with the exception of egg and sperm cells).

Answer 37

D. True. The number of chromosomes varies from one organism to another, but is constant in all cells of the same organism.

Question 38

Which of the following statements are correct? Explain your answers.

E. The cytosol contains membrane-enclosed organelles, such as lysomes.

Answer 38

E. False. The cytosol is the cytoplasm excluding all organelles.

Question 39

Which of the following statements are correct? Explain your answers.

F. Nuclei and mitochondria are surrounded by a double membrane.

Answer 39

F. True. The nuclear envelope is a double membrane, and mitochondria are surrounded by both an inner and an outer membrane.

Question 40

Which of the following statements are correct? Explain your answers.

G. Protozoans are complex organisms with a set of specialized cells that form tissues, such as flagella, mouthparts, stinging darts, and leglike appendages.

Answer 40

G. False. Protozoans are single-cell organisms and therefore do not have different tissues. They have a complex structure, however, that has highly specialized parts.

Question 41

Which of the following statements are correct? Explain your answers.

H. Lysosomes and peroxisomes are the site of degradation of unwanted materials.

Answer 41

H. Somewhat true. Peroxisomes and lysosomes contain enzymes that catalyze the breakdown of substances produced in the cytosol or taken up by the cell. One can argue, however, that many of these substances are degraded to generate food molecules, and as such are certainly not “unwanted.”

Question 42

What organelles contain genetic information?

Answer 42

Mitochondria, and plastids in plants, also have some genetic information.

Question 43

What selects what goes in and out of the nucleus?

Answer 43

Nuclear pores, which are part of the nuclear envelope, are protein complexes that select what substances go in and out of the nucleus

Question 44

What is included in the endomembrane system?

Answer 44

• The endomembrane system includes the ER, the Golgi apparatus, the vesicles, endosomes and lysosomes.
• The ER plus the membranes and compartments that receive materials from vesicles are part of the endomembrane system.

Question 45

What moves materials synthesized by the ER?

Answer 45

Materials synthesized at the ER are moved to their destinations by way of vesicles.

Question 46

Where are materials sorted by the Golgi apparatus sent to?

Answer 46

Materials are sorted into new vesicles that are then delivered to the plasma membrane or endosomes.