Chapter 6 Flashcards
1
Q
What are all organisms made out of?
A
Cells
2
Q
What are cells?
A
- The basic structural and functional unit of every organism
- The simplest collection of matter that can be alive
3
Q
What is cell structure correlated to?
A
Cellular function
4
Q
How are all cell structures related?
A
All cells are related by their descent from earlier cells
5
Q
Scientists use what to visualize cells?
A
microscopes
6
Q
What occurs in a light microscope?
A
-visible light is passed through a specimen and then through glass lenses
-the lenses refract(bend) the light, so that the image is magnified
7
Q
What are the 3 important parameters of microscopy?
A
magnification, resolution, contrast
8
Q
Magnification
A
the ratio of an object’s image size to its real size
9
Q
Resolution
A
the measure of the clarity of the image or the minimum distance of 2 distinguishable points
10
Q
Contrast
A
visible differences in parts of the sample
11
Q
Light microscopes can magnify effectively to about
A
1,000 times the size of the actual specimen
12
Q
Most sub-cellular structures, including organelles(membrane enclosed compartments) are too small to be resolved by
A
a light microscope
13
Q
What are the 2 types of electron microscopes(EMs)?
A
Scanning electron microscopes and transmission electron microscopes
14
Q
Scanning Electron Microscopes (SEMs)
A
focus on a beam of electrons onto the surface of a specimen, providing images that look 3D
15
Q
Transmission Electron Microscopes (TEMs)
A
-focus on a beam of electrons through a specimen
-used mainly to study the internal structure of cells
16
Q
What forms of microscopy provide sharper images of 3-dimensional tissues and cells?
A
Confocal microscopy and deconvolution microscopy
17
Q
What is cell fractionation?
A
-process of taking cells apart and separating the major organelles from one another
-enables scientists to determine the functions of organelles
18
Q
Centrifuges
A
fractionate cells into their component parts
19
Q
What are the basic features of all cells(prokaryotes and eukaryotes)?
A
-plasma membrane
-semifluid substance called cytosol
-chromosomes(carry genes in the form of DNA)
-ribosomes(make proteins)
-ATP
20
Q
Prokaryotic cells are characterized by having
A
-no nucleus
-DNA in an unbound region called the nucleoid
-no membrane-bound organelles
-cytoplasm bound by the plasma membrane
21
Q
Eukaryotic cells are characterized by having
A
-DNA in a nucleus that is bounded by a membranous nuclear envelope
-membrane-bound organelles
-cytoplasm in the region between the plasma membrane and nucleus
-generally much larger than prokaryotic cells
22
Q
Mycoplasmas
A
-the smallest bacteria
-1.0 um in diameter
23
Q
What is the average size in diameter of most bacteria?
A
1-5 um
24
Q
What is the average size of eukaryotic cells?
A
10-100 um in diame
25
As the surface area of a cell increases by a factor of n2
the volume increases by a factor of n3
26
Which cells have a greater surface area relative to volume?
small cells
27
What is the plasma membrane?
-selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell
28
What is the general structure of a biological membrane?
a double layer of phospholipids
29
What does the nucleus contain?
-most of the DNA in a eukaryotic
-most of the cell's genes
-usually the most conspicuous organelle
30
What does the nuclear envelope do?
encloses the nucleus, separating it from the cytoplasm
31
What is the nuclear membrane made up of?
a double membrane; each membrane consists of a lipid bilayer
32
What do ribosomes do?
use information from the DNA to make proteins
33
Pores
regulate the entry and exit of molecules from the nucleus
34
Nuclear lamina
-composed of proteins
-maintains the shape of the nucleus
35
Chromosomes
composed of a single DNA molecule associated with proteins(in the nucleus)
36
Chromatin
-DNA and proteins of chromosomes
-condenses to form discrete chromosomes as a cell prepares to divide
37
What is the nucleolus?
-the site of ribosomal RNA (rRNA) synthesis
-located within the nucleus
38
Ribosomes
particles made up of ribosomal RNA and protein
39
Where do ribosomes carry out protein synthesis?
-in the cytosol(free ribosomes)
-on the outside of the endoplasmic reticulum or nuclear envelope(bound ribosomes)
40
What are the components of the endomembrane system?
-nuclear envelope
-endoplasmic reticulum (ER)
-golgi apparatus
-lysosomes
-vacuoles
-plasma membrane
-either continuous or connected via transfer by vesicles
41
What are the tasks of the endomembrane system?
-synthesis of proteins and their transport into membranes and organelles or out of the cell
-metabolism and movement of lipids
-detoxification of poisons
42
Endoplasmic reticulum (ER)
-accounts for more than half of the total membrane in many eukaryotic
-ER membrane is continuous with the nuclear envelope
43
What are the 2 distinct regions of the ER?
smooth ER, rough ER
44
Smooth ER
lacks ribosomes
45
Rough ER
surface is studded with ribosomes
46
What does the smooth ER do?
-synthesizes lipids
-metabolizes carbohydrates
-detoxifies drugs and poisons
-stores calcium ions (in muscles)
47
What does the rough ER do?
-bound ribosomes secrete glycoproteins
-distributes transport vesicles, proteins surrounded by membraned
-is a membrane factory for the cell
48
what are glycoproteins?
proteins covalently bonded to carbohydrates
49
What does the golgi apparatus consist of?
flattened membranous sacs called cisternae
50
What are the functions of the golgi apparatus?
-modifies products of the ER
-manufactures certain macromolecules
-sorts and packages materials into transport vesicles
51
cis face
"receiving" side of golgi apparatus
52
trans face
"shipping" side of golgi apparatus
53
What is a lysosome?
a membranous sac of hydrolytic enzymes that can digest macromolecules
54
What can lysosome enzymes do?
-can hydrolyze proteins, fats, polysaccharides, and nucleic acids
-work best in the acidic environment inside the lysosome
55
Phagocytosis
engulfing of a cell by some cells, forming a food vacuole
56
Lysosomes fuse with
the food vacuole and digests the molecules
57
Autophagy
use of enzymes to recycle the cell's own organelles and macromolecules
58
Vacuoles
derived from endoplasmic reticulum and goli apparatus; seen in plant or fungal cells
59
Contractile vacuoles
-found in many freshwater protists
-pump excess water out of cells
60
Central vacuoles
-found in many mature plant cells
-hold organic compounds and water
61
Mitochondria
-the sites of cellular respiration( a metabolic process that uses oxygen to generate ATP)
62
What is the site of photosynthesis?
chloroplasts (found in plants and algae)
63
What are the similarities between mitochondria, chloroplasts and bacteria?
-enveloped by a double membrane
-contain free ribosomes and circular DNA molecules
-grow and reproduce somewhat independently in cells
64
What is the endosymbiont theory?
-an early ancestor of eukaryotic cells engulfed a non-photosynthetic prokaryotic cell, which formed an endosymbiont relationship with its host
-the host cell and endosymbiont merged into a single organism, a eukaryotic cell with a mitochondrion
-at least one of these cells may have taken up a photosynthetic prokaryote, becoming the ancestor of cells that contain chloroplasts
65
What is nearly in all eukaryotic cells?
mitochondria
66
What types of membranes does a mitochondria have?
-a smooth outer membrane
-inner membrane folded into cristae(presenting a large surface area for enzymes that synthesize ATP)
67
What does the inner membrane create?
2 compartments:
-intermembrane space
-mitochondrial matrix(some metabolic steps of CR are catalyzed here)
68
What do chloroplasts contain?
green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis
69
Chloroplast structure includes
-thylakoids
-stroma
70
Thylakoids
membranous sacs, stacked to form a granum
71
Stroma
internal fluid
72
Chloroplasts is one group of plant organelles called
plastids
73
What are peroxisomes?
specialized metabolic compartments bounded by a single membrane, oxidative organelles
74
What do peroxisomes produce?
hydrogen peroxide (H2O2) and convert it to water
75
What do peroxisomes perform?
reactions with many different functions
-convert the fatty acids in seeds to sugars
76
What is the cytoskeleton?
-a network of fibers extending throughout the cytoplasm
-organizes the cell's structures and activities, anchoring many organelles
77
What protein structures is a cytoskeleton composed of?
-microtubules
-microfilaments
-intermediate filaments
78
What does the cytoskeleton help with?
-support the cell and maintain it's shape
-interacts with motor proteins to produce motility
-regulate biochemical activities
79
Molecular transport
vesicles can travel along "monorails" provided by the cytoskeleton
80
Microtubules
-maintain cell shape
-cell motility
-chromosome movements in cell division
-organelle movements
(grow from a centrosome near nucleus)
81
Microfilaments
-maintain cell shape
-changes in cell shape
-muscle contraction
-cytoplasmic streaming
-cell motility
-cell division
82
Intermediate filaments
-maintain cell chape
-anchorage of nucleus and certain organelles
-formation of nuclear lamina
83
What is a centrosome?
"mircotubule-organizing center"
-in animal cells, has a pair of centrioles(each with 9 triplets of microtubules arranged in a ring(9+0))
84
Differences between Cilia and Flagella
-beating patterns
-cilia occur in large numbers on cell surface
-flagella are much longer(10-200 um; they share the same diameter)
-usually only 1 or a few flagella per cell
85
What do microtubules control?
the beating of cilia and flagella(locomotor appendages of some cells)
86
Common structure between Cilia and Flagella
-a core of microtubules sheathed by the plasma membrane
-a basal body that anchors the cilium or flagellum
-a motor protein called dynein, which drives the bending movements of a cilium or flagellum(9+2)
87
How can dynein "walking" move flagella and cilia?
-dynein arms alternatively grab, move, and release the outer microtubules
-protein cross-links limit sliding
-forces exerted by dynein arms cause doublets to curve, bending the cilium or flagellum
88
What are microfilaments?
solid rods about 7 nm in diameter, built as a twisted double chain of actin subunits
89
What is the structural role of microfilaments?
to bear tension, resisting pulling forces within the cell; they form a 3D network called the cortex just inside the plasma membrane to help support the cell's shape
90
Microvilli
core made up of bundles of microfilaments(in intestinal cells)
91
Microfilaments that function in cellular motility contain what protein in addition to actin?
myosin
92
Actin filaments are arranged parallel to one another in
muscle cells
93
Thicker filaments composed of myosin
interdigitate with the thinner actin fibers
94
What drives amoeboid movement?
localized contraction brought about by actin and myosin
95
Pseudopodia
-cellular extensions
-extend and contract through the reversible assembly and contraction of actin subunits into microfilaments
96
What drives parallel myosin and actin filaments past each other(contraction)?
"walking of myosin projections
97
What causes contractions in the cell?
interaction of actin filaments with myosin
98
What is a result of actin-myosin interactions and sol-gel transformations in plant cells?
cytoplasmic streaming
99
What is cytoplasmic streaming?
-a circular flow of cytoplasm within cells
-speeds distribution of materials within the cell
100
Are intermediate filaments larger than microfilaments?
yes but they are smaller than microtubules
101
Intermediate filaments support
-cell shape
-fix organelles in place
-bearing tension
102
Which is the more permanent cytoskeleton fixture?
intermediate filaments
103
Extracellular structures external to the plasma membrane
-cell walls of plants
-the extracellular matrix (ECM) of animal cells
-intercellular junctions
104
What does the cell wall in plants do?
-distinguishes plant cells from animal cells
-protects plant cell
-maintains its shape
-prevents excessive uptake of water
105
True or False: Prokaryotes, fungi, and some protists also have cell walls
True
106
What are plant cell walls made up of?
-cellulose fibers
-polysaccharides
-proteins
-may have multiple layers
107
Primary cell wall
relatively thin and flexible
108
Middle lamella
thin layer between primary walls of adjacent cells
109
Secondary cell wall(in some cells)
added between the plasma membrane and the primary cell wall
110
Plasmodesmata
channels between adjacent plant cells
111
What are animal cells covered by?
extracellular matrix(ECM)
112
What is the ECM made up of?
glycoproteins such as collagen, proteoglycans, and fibronectin
113
ECM proteins bind to receptor proteins in the plasma membrane called
integrins
114
Functions of ECM
-support
-adhesion
-movement
-regulation
115
Intercellular junctions
facilitate physical contact between neighboring cells in tissues, organs, or organ systems
116
What are the types of intercellular junctions?
-Plasmodesmata
-Tight junctions
-Desmosomes
-Gap junctions
117
What are plasmodesmata? And what do they allow?
-channels that perforate plant cell walls
-allow water, small solutes and sometimes proteins and RNA pass from cell to cell
118
At tight junctions
membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid(interlocking of proteins binds lipid portion of membrane)
119
What do desmosomes do?(anchoring junctions)
fasten cells together into strong sheets
120
What do gap junctions provide?(communicating junctions)
cytoplasmic channels between adjacent cells(connexons form protein channels, allows molecules to pass for (rapid)communication; allow ions to pass; coordinated contractions in heart muscle)
121
What is attached to the cytoskeleton to resist stretching and twisting?
cell adhesion molecules + intercellular cement(on dense areas)
122
Macrophage's ability to destroy bacteria involves
the whole cell, coordinating components such as the cytoskeleton, lysosomes, and plasma membrane
