(Unit 2) Chapter 6: A Tour of the Cell Flashcards
1
Q
What is as fundamental to the living systems of biology as the atom is to chemistry?
A
Cell
2
Q
True or False:
All organisms are made of cells
A
True
3
Q
When were microscopes invented?
A
1590, refined during the 1600s
4
Q
Describe how a light microscope (LM) works (2)
A
Visible light is passed through the specimen and then through glass lenses
The lenses refract the light in such a way that the image of the specimen is magnified as it is projected into the eye or others
5
Q
Define:
Refract
A
Bend
6
Q
Define:
Magnification
A
The ratio of an object’s image size to its real size
7
Q
Define:
Resolution
A
A measure of the clarity of the image; It is the minimum distance two points can be separated and still be distinguished as two points
8
Q
What is resolution also known as?
A
Resolving power
9
Q
What are three important parameters in microscopy?
A
Magnification
Resolution
Contrast
10
Q
Define:
Contrast
A
Accentuate differences in parts of the sample
11
Q
The light microscope cannot resolve detail finer than about ___ __________ or ___ __________
A
0.2 micrometres
200 nanometres
12
Q
Cell walls were first seen by who? When?
A
Robert Hooke, in 1665
13
Q
Define:
Organelles
A
Membrane-enclosed compartments
14
Q
Describe how an electron microscope (EM) works
A
Instead using light, it focuses a beam of electrons through the specimen or onto its surface
15
Q
Resolution is inversely related to the ____________ of the _________ a microscope uses for imaging, and ________ beams have much _______ wavelengths than _______ _____
A
Wavelength Radiation Electron Shorter Visible light
16
Q
1 cm = __^__ m = ___ inch
A
10^-2
0.4
17
Q
1 mm = __^__ m
A
10^-3
18
Q
1 micrometre = __^__ mm = __^__ m
A
10^-3
10^-6
19
Q
1 nm = __^__ micrometre = __^__ m
A
10^-3
10^-9
20
Q
Describe:
Brightfield (unstained specimen) in light microscopy
A
Passes light directly through specimen, unless cell is naturally pigmented or artificially stained the image has little contrast
21
Q
Describe:
Brightfield (stained specimen) in light microscopy
A
Staining with various dyes enhances contrast
22
Q
What do most staining procedures require the cells to be?
A
Require that cells be fixed (preserved)
23
Q
Describe:
Phase-contrast in light microscopy
A
Enhances contrast in unstained cells by amplifying variations in density within specimen
24
Q
What is phase-contrast especially useful for?
A
Especially useful for examining living, unpigmented cells
25
Describe:
| Differential-interference-contrast (Nomarski) in light microscopy
Like phase-contrast microscopy, uses optical modifications to exaggerate differences in density, making the image appear almost 3-D
26
Describe:
| Fluorescence in light microscopy
Shows the locations of specific molecules in the cell by tagging the molecules with fluorescent dyes or antibodies
27
What do the fluorescent dyes in fluorescence light microscopy do?
Absorb ultraviolet radiation and emit visible light
28
Describe:
| Confocal in light microscopy
A fluorescent "optical sectioning" technique that uses a pinhole aperture to eliminate out-of-focus light from a thick sample, creating a single plane of fluorescence in the image
29
In confocal light microscopy, capturing sharp images at many different planes, a ___ construction can be created
3-D
30
Define:
| Ultrastructure
The cellular anatomy revealed by an electron microscope
31
Describe how scanning electron microscope (SEM) works
Electron beam scans the surface of the sample, which is usually coated with a thin film of gold
The beam excites electrons on the surface, and these secondary electrons are detected by a device that translates the pattern of electrons into an electronic signal to a video screen
32
What is a scanning electron microscope (SEM) useful for?
SEM is especially useful for detailed study of the surface of a specimen
33
What is the resulting image of SEM?
An image of the specimen's topography; SEM has great depth of field, results in an image that appears 3-D
34
Describe how a transmission electron microscope (TEM) works
Aims an electron beam through a very thin section of the specimen
Specimen has been stained with atoms of heavy metals which attach to certain cellular structures, enhancing the electron density in some parts of the cell
The electrons passing through the specimen are scattered more in the denser regions, so fewer are transmitted
35
What does the image of transmission electron microscope (TEM) display?
The pattern of transmitted electrons
36
Instead of using glass lenses, what does the TEM use?
Electromagnets as lenses, to bend the paths of the electrons ultimately focusing the image onto a screen for viewing or onto photographic film
37
What is an advantage of electron microscopes?
They reveal many organelles and other subcellular structures that are impossible to resolve with the light microscope
38
What is an advantage of light microscopes and a disadvantage of electron microscopes?
Light microscopes can study living cells, as the specimen preparation in electron microscopy kills the cells
39
Define:
| Cytology
The study of cell structure
40
Define:
| Biochemistry
The study of the molecules and chemical processes (metabolism) of cells
41
Define:
| Cell Fractionation
A useful technique that takes cells apart and separates the major organelles and other subcellular structures from one another; the instrument used is a centrifuge
42
What is a centrifuge?
An instrument, which spins test tubes holding mixtures of disrupted cells at various speeds
43
What is the purpose of cell fractionation?
Enables researchers to prepare specific cell components in bulk and identify their functions, a task that would be far more difficult with intact cells
44
What do the forces of a centrifuge create?
Causes a fraction of the cell components to settle to the bottom of the tube, forming a pellet
45
At lower speeds in a centrifuge, the pellet consists of ______ components
Larger
46
List the basic features that all cells have in common (4)
```
Bounded by selective barrier (plasma membrane)
A semifluid, jellylike substance enclosed by the membrane which organelles and other components are found (cytosol)
Contain chromosomes (carry genes in the form of DNA)
Have ribosomes (tiny complexes that make proteins according to instructions from the genes)
```
47
What is the major difference between prokaryotic and eukaryotic cells?
Location of their DNA
48
In an _________ cell, most of the DNA is in an organelle called the _______
Eukaryotic
| Nucleus
49
Where does the word eukaryotic come from?
Greek, eu for true, and karyon for kernel referring to the nucleus
50
Where does the word prokaryotic come from?
Greek, pro for before, and karyon for kernel
51
In a ___________ cell, the DNA is concentrated in a region that is not membraned-enclosed, called the ________
Prokaryotic
| Nucleoid
52
True or False:
| Eukaryotic cells are generally much larger than prokaryotic cells
True
53
What functions as a selective barrier at the boundary of every cell?
Plasma membrane
54
How does the plasma membrane function? (3)
Acts as a selective barrier that allows sufficient passage of oxygen, nutrients, and wastes to service the entire cell
55
____ is proportional to the linear dimension squared, whereas volume is proportional to the linear dimension _____. Thus a smaller object has a great ratio of:
Area
Cubed
Surface area to volume
56
True or False:
| Larger organisms have larger cells than smaller organisms
False, larger organisms generally do not have more cells than smaller organisms - simply more cells
57
What organelles are present in animal cells but not plant cells? (3)
Lysosomes
Centrosomes, with centrioles
Flagella (present in some plant cells)
58
What organelles are present in plant cells but not animal cells? (4)
Chloroplasts
Central vacuole
Cell wall
Plasmodesmata
59
Describe/state the function of and which cells they exist in:
Flagellum
```
Locomotion organelle present in some animal cells; composed of a cluster of microtubules within an extension of the plasma membrane
Animal cells (but present in some plant sperm)
```
60
Describe/state the function of and which cells they exist in:
Centrosome
Region where the cell's microtubules are initiated; contains a pair of centrioles (function unknown)
Animal cells
61
```
Describe/state the function of and which cells they exist in:
Endoplasmic Reticulum (ER)
```
Network of membranous sacs and tubes; active in membrane synthesis and other synthetic and metabolic processes; has rough (ribosome-studded) and smooth regions
Both plant and animal cells
62
What are the rough and smooth regions of the endoplasmic reticulum known as?
Rough ER
| Smooth ER
63
Describe/state the function of and which cells they exist in:
Nuclear envelope
Double membrane enclosing the nucleus; perforated by pores; continuous with ER
Both plant and animal cells
64
Describe/state the function of and which cells they exist in:
Nucleolus
Structure involved in production of ribosomes; a nucleus has one or more nucleoli
Both plant and animal cells
65
Describe/state the function of and which cells they exist in:
Chromatin
Material consisting of DNA and proteins; visible as individual chromosomes in a dividing cell
Both plant and animal cells
66
What does the nucleus comprise of? (3)
Nuclear envelope
Nucleolus
Chromatin
67
Describe/state the function of and which cells they exist in:
Plasma membrane
Membrane enclosing the cell
| Both plant and animal cells
68
Describe/state the function of and which cells they exist in:
Ribosomes
Complexes (small brown dots) that make proteins; free in cytosol or bound to rough ER or nuclear envelope
Both plant and animal cells
69
Describe/state the function of and which cells they exist in:
Golgi apparatus
Organelle active in synthesis, modification, sorting, and secretion of cell products
Both plant and animal cells
70
Describe/state the function of and which cells they exist in:
Lysosome
Digestive organelle where macromolecules are hydrolysed
| Animal cells
71
Describe/state the function of and which cells they exist in:
Mitochondrion
Organelle where cellular respiration occurs and most ATP is generated
Both plant and animal cells
72
Describe/state the function of and which cells they exist in:
Peroxisome
Organelle with various specialized metabolic functions; produces hydrogen peroxide as a by-product, then converts it to water
Both plant and animal cells
73
Describe/state the function of and which cells they exist in:
Microvilli
Projections that increase the cells surface area
| Both plant and animal cells
74
Describe/state the function of and which cells they exist in:
Cytoskeleton
Reinforces cell's shape, functions in cell movement; components are made of protein
Both plant and animal cells
75
What does the cytoskeleton include? (3)
Microfilaments
Intermediate filaments
Microtubules
76
Describe/state the function of and which cells they exist in:
Cell wall
Outer layer that maintains cell's shape and protects cell from mechanical damage; made of cellulose, other polysaccharides, and protein
Plant cells
77
Describe/state the function of and which cells they exist in:
Plasmodesmata
Channels through cell walls that connect the cytoplasms of adjacent cells
Plant cells
78
Describe/state the function of and which cells they exist in:
Chloroplasts
Photosynthetic organelle; converts energy of sunlight to chemical energy stored in sugar molecules
Plant cells
79
Describe/state the function of and which cells they exist in:
Central vacuole
Prominent organelle in older plant cells; functions include storage, breakdowns of waste products, hydrolysis of macromolecules; enlargement of vacuole is a major mechanism of plant growth
Plant cells
80
What contains most of the genes in the eukaryotic cell?
Nucleus
81
Besides the nucleus, where else are genes located? (2)
Some genes are located in the mitochondria and chloroplasts
82
The nuclear envelope is a ______ membrane. Describe this structure (3)
Double
Two membranes - each a lipid bilayer - separated by a space of 20-40 nm
Envelope is perforated by pore structures that are about 100 nm in diameter
At the lip of each pore, the inner and outer membranes of the nuclear envelope are continuous
83
What encloses the nucleus?
Nuclear envelope; It encloses and separates its contents from the cytoplasm
84
An intricate _______ structure called a ____ _______ lines each pore and plays what role?
Protein
Pore complex
Regulates the entry and exit of macromolecules
