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My Packs: AP Biology > (Unit 2) Chapter 6: A Tour of the Cell > Flashcards

(Unit 2) Chapter 6: A Tour of the Cell Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is as fundamental to the living systems of biology as the atom is to chemistry?

A

Cell

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2
Q

True or False:

All organisms are made of cells

A

True

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3
Q

When were microscopes invented?

A

1590, refined during the 1600s

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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

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5
Q

Define:

Refract

A

Bend

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6
Q

Define:

Magnification

A

The ratio of an object’s image size to its real size

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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

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8
Q

What is resolution also known as?

A

Resolving power

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9
Q

What are three important parameters in microscopy?

A

Magnification
Resolution
Contrast

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10
Q

Define:

Contrast

A

Accentuate differences in parts of the sample

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11
Q

The light microscope cannot resolve detail finer than about ___ __________ or ___ __________

A

0.2 micrometres

200 nanometres

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12
Q

Cell walls were first seen by who? When?

A

Robert Hooke, in 1665

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13
Q

Define:

Organelles

A

Membrane-enclosed compartments

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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

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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
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16
Q

1 cm = __^__ m = ___ inch

A

10^-2

0.4

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17
Q

1 mm = __^__ m

A

10^-3

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18
Q

1 micrometre = __^__ mm = __^__ m

A

10^-3

10^-6

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19
Q

1 nm = __^__ micrometre = __^__ m

A

10^-3

10^-9

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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

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21
Q

Describe:

Brightfield (stained specimen) in light microscopy

A

Staining with various dyes enhances contrast

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22
Q

What do most staining procedures require the cells to be?

A

Require that cells be fixed (preserved)

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23
Q

Describe:

Phase-contrast in light microscopy

A

Enhances contrast in unstained cells by amplifying variations in density within specimen

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24
Q

What is phase-contrast especially useful for?

A

Especially useful for examining living, unpigmented cells

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25
Q

Describe:

Differential-interference-contrast (Nomarski) in light microscopy

A

Like phase-contrast microscopy, uses optical modifications to exaggerate differences in density, making the image appear almost 3-D

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26
Q

Describe:

Fluorescence in light microscopy

A

Shows the locations of specific molecules in the cell by tagging the molecules with fluorescent dyes or antibodies

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27
Q

What do the fluorescent dyes in fluorescence light microscopy do?

A

Absorb ultraviolet radiation and emit visible light

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28
Q

Describe:

Confocal in light microscopy

A

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

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29
Q

In confocal light microscopy, capturing sharp images at many different planes, a ___ construction can be created

A

3-D

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30
Q

Define:

Ultrastructure

A

The cellular anatomy revealed by an electron microscope

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31
Q

Describe how scanning electron microscope (SEM) works

A

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

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32
Q

What is a scanning electron microscope (SEM) useful for?

A

SEM is especially useful for detailed study of the surface of a specimen

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33
Q

What is the resulting image of SEM?

A

An image of the specimen’s topography; SEM has great depth of field, results in an image that appears 3-D

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34
Q

Describe how a transmission electron microscope (TEM) works

A

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
Q

What does the image of transmission electron microscope (TEM) display?

A

The pattern of transmitted electrons

36
Q

Instead of using glass lenses, what does the TEM use?

A

Electromagnets as lenses, to bend the paths of the electrons ultimately focusing the image onto a screen for viewing or onto photographic film

37
Q

What is an advantage of electron microscopes?

A

They reveal many organelles and other subcellular structures that are impossible to resolve with the light microscope

38
Q

What is an advantage of light microscopes and a disadvantage of electron microscopes?

A

Light microscopes can study living cells, as the specimen preparation in electron microscopy kills the cells

39
Q

Define:

Cytology

A

The study of cell structure

40
Q

Define:

Biochemistry

A

The study of the molecules and chemical processes (metabolism) of cells

41
Q

Define:

Cell Fractionation

A

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
Q

What is a centrifuge?

A

An instrument, which spins test tubes holding mixtures of disrupted cells at various speeds

43
Q

What is the purpose of cell fractionation?

A

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
Q

What do the forces of a centrifuge create?

A

Causes a fraction of the cell components to settle to the bottom of the tube, forming a pellet

45
Q

At lower speeds in a centrifuge, the pellet consists of ______ components

A

Larger

46
Q

List the basic features that all cells have in common (4)

A 
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
Q

What is the major difference between prokaryotic and eukaryotic cells?

A

Location of their DNA

48
Q

In an _________ cell, most of the DNA is in an organelle called the _______

A

Eukaryotic

Nucleus

49
Q

Where does the word eukaryotic come from?

A

Greek, eu for true, and karyon for kernel referring to the nucleus

50
Q

Where does the word prokaryotic come from?

A

Greek, pro for before, and karyon for kernel

51
Q

In a ___________ cell, the DNA is concentrated in a region that is not membraned-enclosed, called the ________

A

Prokaryotic

Nucleoid

52
Q

True or False:

Eukaryotic cells are generally much larger than prokaryotic cells

A

True

53
Q

What functions as a selective barrier at the boundary of every cell?

A

Plasma membrane

54
Q

How does the plasma membrane function? (3)

A

Acts as a selective barrier that allows sufficient passage of oxygen, nutrients, and wastes to service the entire cell

55
Q

____ is proportional to the linear dimension squared, whereas volume is proportional to the linear dimension _____. Thus a smaller object has a great ratio of:

A

Area
Cubed
Surface area to volume

56
Q

True or False:

Larger organisms have larger cells than smaller organisms

A

False, larger organisms generally do not have more cells than smaller organisms - simply more cells

57
Q

What organelles are present in animal cells but not plant cells? (3)

A

Lysosomes
Centrosomes, with centrioles
Flagella (present in some plant cells)

58
Q

What organelles are present in plant cells but not animal cells? (4)

A

Chloroplasts
Central vacuole
Cell wall
Plasmodesmata

59
Q

Describe/state the function of and which cells they exist in:
Flagellum

A 
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
Q

Describe/state the function of and which cells they exist in:
Centrosome

A

Region where the cell’s microtubules are initiated; contains a pair of centrioles (function unknown)
Animal cells

61
Q 
Describe/state the function of and which cells they exist in:
Endoplasmic Reticulum (ER)
A

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
Q

What are the rough and smooth regions of the endoplasmic reticulum known as?

A

Rough ER

Smooth ER

63
Q

Describe/state the function of and which cells they exist in:
Nuclear envelope

A

Double membrane enclosing the nucleus; perforated by pores; continuous with ER
Both plant and animal cells

64
Q

Describe/state the function of and which cells they exist in:
Nucleolus

A

Structure involved in production of ribosomes; a nucleus has one or more nucleoli
Both plant and animal cells

65
Q

Describe/state the function of and which cells they exist in:
Chromatin

A

Material consisting of DNA and proteins; visible as individual chromosomes in a dividing cell
Both plant and animal cells

66
Q

What does the nucleus comprise of? (3)

A

Nuclear envelope
Nucleolus
Chromatin

67
Q

Describe/state the function of and which cells they exist in:
Plasma membrane

A

Membrane enclosing the cell

Both plant and animal cells

68
Q

Describe/state the function of and which cells they exist in:
Ribosomes

A

Complexes (small brown dots) that make proteins; free in cytosol or bound to rough ER or nuclear envelope
Both plant and animal cells

69
Q

Describe/state the function of and which cells they exist in:
Golgi apparatus

A

Organelle active in synthesis, modification, sorting, and secretion of cell products
Both plant and animal cells

70
Q

Describe/state the function of and which cells they exist in:
Lysosome

A

Digestive organelle where macromolecules are hydrolysed

Animal cells

71
Q

Describe/state the function of and which cells they exist in:
Mitochondrion

A

Organelle where cellular respiration occurs and most ATP is generated
Both plant and animal cells

72
Q

Describe/state the function of and which cells they exist in:
Peroxisome

A

Organelle with various specialized metabolic functions; produces hydrogen peroxide as a by-product, then converts it to water
Both plant and animal cells

73
Q

Describe/state the function of and which cells they exist in:
Microvilli

A

Projections that increase the cells surface area

Both plant and animal cells

74
Q

Describe/state the function of and which cells they exist in:
Cytoskeleton

A

Reinforces cell’s shape, functions in cell movement; components are made of protein
Both plant and animal cells

75
Q

What does the cytoskeleton include? (3)

A

Microfilaments
Intermediate filaments
Microtubules

76
Q

Describe/state the function of and which cells they exist in:
Cell wall

A

Outer layer that maintains cell’s shape and protects cell from mechanical damage; made of cellulose, other polysaccharides, and protein
Plant cells

77
Q

Describe/state the function of and which cells they exist in:
Plasmodesmata

A

Channels through cell walls that connect the cytoplasms of adjacent cells
Plant cells

78
Q

Describe/state the function of and which cells they exist in:
Chloroplasts

A

Photosynthetic organelle; converts energy of sunlight to chemical energy stored in sugar molecules
Plant cells

79
Q

Describe/state the function of and which cells they exist in:
Central vacuole

A

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
Q

What contains most of the genes in the eukaryotic cell?

A

Nucleus

81
Q

Besides the nucleus, where else are genes located? (2)

A

Some genes are located in the mitochondria and chloroplasts

82
Q

The nuclear envelope is a ______ membrane. Describe this structure (3)

A

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
Q

What encloses the nucleus?

A

Nuclear envelope; It encloses and separates its contents from the cytoplasm

84
Q

An intricate _______ structure called a ____ _______ lines each pore and plays what role?

A

Protein
Pore complex
Regulates the entry and exit of macromolecules

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