Module 3: In & Around Cells

Question 1

Magnification

Resolution

Answer 1

Magnification: the process of enlarging the apparent size of something.

Resolution: the ability of a microscope to distinguish detail.

Question 2

What is the difference between objective and ocular lenses?

Answer 2

Objective forms the initial image, while the ocular lens magnifies it and collects it.

Question 3

What is the best way to avoid breaking a slide when using a compound light microscope?

Answer 3

Start viewing the specimen at low magnification, use coarse and then fine focus to see the image clearly, and then switch to higher magnification.

Once you are at higher magnification, do not focus using the coarse focus knob, only the fine focus knob.

Question 4

Describe the structure and function of the iris diaphragm on a compound light microscope.

Answer 4

Adjusts the amount of light passing through the specimen.

Question 5

What is the relationship between magnification and:

a) The diameter of field of view?

b) The amount of light needed to illuminate a specimen?

c) The depth of focus (i.e., the depth of the specimen that is in focus at any one time)?

Answer 5

a) As you magnify the image, the diameter of the field of view decreases

b) as you increase magnification, the amount of light you need stays the same

c) as you increase magnification, the depth of focus remains unchanged.

Question 6

What is the purpose of the condenser in a compound light microscope?

Answer 6

Condenser is a set of lenses that focuses the light through the specimen into the objective lens.

Question 7

Why should you never use tissues or cloth to clean microscope lens?

Answer 7

Both tissues and cloth can scratch the objective lens; you should only use Kimwipes or other texturally-similar products.

Question 8

When you are beginning your examination of a specimen, do you start focusing at the highest or lowest level of magnification? Why?

Answer 8

Low, because the microscope is parfocal (stays in focus when magnification/focal length is changed).

You need to find highest resolving power at low magnification in order to see an image at higher magnification.

It also avoids slide breakage.

Question 9

If you are examining a specimen using a 10X ocular lens and a 10X objective lens, how much would the specimen be magnified?

Answer 9

100X

Question 10

You have determined for a particular microscope there are 20 ocular micrometer units per 1 mm under 40X magnification. If you examine a specimen using the 10X ocular and 10X (as in part a) and it is 5 ocular micrometer units long, what is its length in mm?

Answer 10

2.5 mm

Question 11

You want to view a cross section of a cell at extremely high magnification greater than 200 000 times. What tool would you use?

a) Confocal microscope
b) Transmission electron microscope
c) Light microscope
d) Scanning electron microscope
e) Dissecting microscope

Answer 11

b) Transmission electron microscope

Question 12

You want to view the surface of a particular cell at magnifications above 1500 times. What tool would you use?

a) Confocal microscope
b) Transmission electron microscope
c) Light microscope
d) Scanning electron microscope
e) Dissecting microscope

Answer 12

c) Light microscope

Question 13

What is the advantage of electron microscopes over light microscopes, and what feature of the former devices makes this possible?

Answer 13

Electron microscopes use beams of electrons, which have much smaller wavelengths. The smaller wavelengths ensure that objects that are very close can be distinguished (as close as 0.00000001 mm) and, thus, we can achieve up to 250 000 times magnification.

Question 14

Microfilaments

Microtubules

Intermediate filaments

Answer 14

Microfilaments are responsible for cell locomotion and the cell’s structural characteristics.

Microtubules serve as intracellular highways for transporting vesicles and organelles; they are also required for cellular locomotion via flagella and cilia.

Intermediate filaments are rope-like structures that anchor organelles and intercellular junctions called desmosomes. They are specialized for bearing tension.

Question 15

Why might the electrical current from the flow of ions across a membrane flatten out?

Answer 15

The electrical current flattens out when all the gramicidin molecules are in use to transport ions in the membrane.

Question 16

If you place an animal cell in a hypotonic solution, you would expect the cell to:

a) Remain the same.
b) Shrivel.
c) Lyse.
d) Become flaccid.

Answer 16

c) Lyse (break down into smaller pieces)

Question 17

Active transport requires:

a) Specific membrane proteins.
b) Changes in conformation.
c) ATP.
d) All of the above.

Answer 17

d) All of the above.

Question 18

List the structures that make up a prokaryotic cell

Answer 18

Cell membrane controls what enters or leaves the cell.

Cytoplasm contains enough proteins and other molecules for the cell’s functions.

The nucleoid region where DNA is contained in a single, condensed, circular chromosome.

Plasmids (small circular pieces of chromosome in most prokaryotes) that help prokaryotes adapt to unusual circumstances.

Ribosomes help produce the proteins within the cytoplasm.

Cell wall surrounds the plasma membrane and functions to protect and give shape to the cell.

Flagella are thin extensions of the cell and lack a membrane covering. They rotate to provide locomotion. (Not all prokaryotes have flagella.)

Cytoskeletons are long thin protein fibres inside the cell. The cytoskeleton fibres help with cell division and help maintain cell shape.

Question 19

Eukaryotic cells can be divided into what 2 parts?

Answer 19

1. The nucleus, which contains the DNA.
2. The cytoplasm, which includes everything between the nucleus and the plasma membrane.

Question 20

Which of the following organelles would you find in a plant cell: mitochondria, nucleus, SER, chloroplast, lysosome, central vacuole?

Answer 20

Mitochondria, nucleus, SER, chloroplast, central vacuole (Note: Lysosomes are not found in plant cells).

Question 21

Morphology

Answer 21

The overall shape and appearance of an organism and its component parts.

Question 22

What is one feature that eukaryotic cells have that prokaryotic cells do not?

Answer 22

A membrane-bound nucleus.

Question 23

What are the 3 phylogenic domains?

Answer 23

Bacteria, Archaea, and Eukarya.

Question 24

What do all prokaryotic cells contain?

Answer 24

A plasma membrane, a chromosome containing DNA, and protein-synthesizing ribosomes.

Question 25

Nucleoid

Answer 25

A dense, centrally located region in prokaryotic cells that contains DNA but is not surrounded by a membrane.

Question 26

How does DNA fit into prokaryotic cells?

Answer 26

By supercoiling with the help of enzymes.

Question 27

Plasmid

Answer 27

A small, usually circular, DNA molecule independent of the cell’s main chromosomes that help the cell to adapt to unusual circumstances.

Present in prokaryotes and some eukaryotes.

Question 28

What is a flagellum in prokaryotic cells?

Answer 28

A long projection that extends from the cell and rotates to help the cell “swim” through an aqueous environment.

Question 29

Fimbria

Answer 29

A long needle-like projection from a cell that helps it stick to non-living surfaces or other cells.

Can contribute to infections by “gluing” bacteria to tissues.

Question 30

What are 3 main differences between prokaryotic and eukaryotic cells?

Answer 30

1. Eukaryotic cells are generally larger.
2. Chromosomes in eukaryotic cells are enclosed within a membrane-bound nucleus; in prokaryotic cells they are in a loosely defined nucleoid region.
3. The cytoplasm in eukaryotic cells is compartmentalized into a larger number of distinct organelles than in prokaryotic cells.

Question 31

What are 2 structures that occur in animal cells but not plant cells?

What are 3 structures that occur in plant cells but not animal cells?

Answer 31

Animal cells have:
1. Centrosomes
2. Lysosomes

Plant cells have:
1. Cell wall
2. Chloroplast
3. Vacuole

Question 32

Lysosomes

Answer 32

Organelles that contain enzymes to digest macromolecules via hydrolysis.

Question 33

Peroxisomes

Answer 33

Organelles that contain enzymes that detoxify reactive molecules.

Question 34

Plastid

Answer 34

A category of organelles found in algal and plant cells.

Chloroplasts are a mature proplastid.

Question 35

Amyloplast

Answer 35

A type of plastid organelle used to store starch in plants.

Question 36

Chromoplast

Answer 36

A type of plastid organelle used to store pigments in petals and other plant tissues.

Question 37

Organelles move in the cell by using which of the following filaments: actin, intermediate or microtubules?

Answer 37

All three.

Question 38

The cells associated with the lining of the respiratory tract of animals function to sweep mucus and fluid out of the lungs. Would you expect these cells to have cilia or flagella? Why?

Answer 38

Cilia. They beat back and forth and can effectively change the motion of materials outside the cell. The action of flagella is a whip-like motion, which propels the cell but may not disturb its external environment as much.

Question 39

Name the organelle:

•Bound by a double membrane
• Inner membrane is folded into cristae
• ATP is made here
•Contains its own genetic material

Answer 39

Mitochondria

Question 40

Name the organelle:

•Stack of flat, membrane-bounded sacs
• Involved in secretion
• Involved in modifying proteins and lipids

Answer 40

Golgi body

Question 41

Name the organelle:

• Roughly spherical
• Bound by a single membrane
• Filled with enzymes, mainly catalase (breaks down H2O2)
•Involved with oxidation of fatty acids

Answer 41

Peroxisomes

Question 42

What is the major protein in:
1. Microfilaments
2. Intermediate filaments
3. Microtubules?

Answer 42

1. Microfilaments: actin
2. Intermediate filaments: keratin
3. Microtubules: α and β tubulin

Question 43

Second Messengers

Phosphorylation Cascades

Answer 43

Second Messengers: A nonprotein signalling molecule produced/activated inside a cell in response to stimulation on the cell surface.

Phosphorylation Cascades: a sequence of signaling pathway events where one enzyme phosphorylates another, causing a chain reaction leading to the phosphorylation of thousands of proteins

Question 44

Explain what is meant by a phosphorylation cascade.

Answer 44

A phosphorylation cascade is a type of signal transduction pathway in which a series of molecules are phosphorylated in turn.

Question 45

Generally speaking, how can two different cells respond differently to the same signal molecule?

Answer 45

Different cells possess different collections of proteins that allow for alternate signal transduction pathways and, as such, variable responses.

Question 46

Which of the following statements about tight junctions is not true?

a) Tight junctions are found in animal tissues.

b) Tight junctions are often found in tissues lining internal cavities and organs.

c) Tight junctions seal adjoining cells.

d) Tight junctions allow for communication and coordination between adjacent cells.

e) Tight junctions can prevent leakage of extracellular fluid across a layer of epithelial cells.

Answer 46

d) Tight junctions allow for communication and coordination between adjacent cells.