Chapter 7 Flashcards
1
Q
What is microscopy?
A
An instrument used to see objects that are too small to be seen by the naked eye
2
Q
When were microscopes invented?
A
In 1590 and was further refined during the 1600s
3
Q
When were cells first seen by Robert Hooke?
A
1665
4
Q
What is a light microscope (LM)?
A
A light microscope uses focused light and lenses to magnify a specimen, usually a cell.
5
Q
What is resolution?
A
A measure of the clarity of the image. The minimum distance between two points that can be separated and still be distinguished at different points.
6
Q
What is magnification?
A
The ratio of an object’s image size to its actual size
7
Q
What is contrast?
A
The difference in brightness between the light and dark areas of an image.
8
Q
What is the electron microscope (EM)?
A
Electron microscopy (EM) is a technique for obtaining high resolution images of biological and non-biological specimens.
9
Q
What is the scanning electron microscope (SEM)?
A
A scanning electron microscope (SEM) scans a focused electron beam over a surface to create an image. The electrons in the beam interact with the sample, producing various signals that can be used to obtain information about the surface topography and composition.
10
Q
What is a brightfield (Unstained specimen) (LM)?
A
Where light passes straight through the specimen unless the cell is naturally pigmented or artificially stained.
11
Q
What is a brightfield (stained specimen) (LM)?
A
Staining with various dyes which enhances contrast. This requires that cells be fixed thereby killing them
12
Q
What is a phase-contrast (LM)?
A
Variations in density within the specimen are amplified to enhance contrast in unstained cells. This is useful for living cells.
13
Q
What is the differential interference contrast (LM)?
A
Similar to phase-contrast where optical modifications are used to exaggerate differences in density. This image appears almost 3D
14
Q
What is fluorescence (LM)?
A
Where the locations of specific molecules in the cell can be revealed by labelling the molecules with fluorescent dyes or antibodies.
15
Q
What is confocal (LM)?
A
Using a lazer an optical sectioning technique eliminates out-of-focus light from a thick sample creating a single plane of fluorescence in the image. This allows for a 3D construction to be formed.
16
Q
What is deconvolution (LM)?
A
Images through deconvolution software which digitally removes out-of-focus light and re-assigns it to its source creating a much sharper 3D image.
17
Q
What is super resolution (LM)?
A
Where sophisticated equipment is used to light up individual florescent molecules and record their position. Combining information from many molecules in different places breaks the limit of resolution resulting in a super sharp image.
18
Q
What does LM stand for?
A
Light micrograph
19
Q
What does SEM stand for?
A
Scanning electron micrograph
20
Q
What does TEM stand for?
A
Transmission electron micrograph.
21
Q
What is the transmission electron micrograph?
A
Used to study the internal structure of the cells. It aims an electron beam through a very thin section of the specimen allowing scientists to observe features such as structure.
22
Q
What is cytology?
A
The study of cell structure
23
Q
What is cell fractionation?
A
Used to seperate cell components based on size and density. It takes cells apart and separates major organelles and other sub cellular structures from one another.
24
Q
What is the centrifuge?
A
A machine with a rapidly rotating container that applies centrifugal force to its contents, typically to separate fluids of different densities (e.g. cream from milk) or liquids from solids.
25
What does cell fractionation allow for?
It enables researchers to prepare specific cell components in bulk and identify their functions.
26
What is a prokaryotic cell?
Cells that do not have a true nucleus or membrane-bound organelles
27
What is a eukaryotic cell?
Eukaryotic cells are cells that contain a nucleus and organelles, and are enclosed by a plasma membrane.
28
What are the types of prokaryotic cells?
Bacteria and Archea
29
What are the types of eukaryotic cells?
Protists, Fungi, animals and plants.
30
What is a cytosol?
the aqueous component of the cytoplasm of a cell, within which various organelles and particles are suspended.
31
What are chromosomes?
Chromosomes are thread-like structures in which DNA is tightly packaged within the nucleus.
32
What are ribosomes?
Ribosomes carry out protein synthesis. Ribosomes can be found floating within the cytoplasm or attached to the endoplasmic reticulum
33
Where does DNA sit in prokaryotic cells?
Concentrated in a region that is not membrane-enclosed called the nucleoid
34
Where does DNA sit in Eukaryotic cells?
In the nucleus which is bounded by a double membrane
35
What is the cytoplasm?
The interior of the cell
36
Which cells are bigger prokaryotic or eukaryotic cells?
Eukaryotic cells
37
What is a plasma membrane and its function?
A selective barrier that allows the passage of enough oxygen, nutrients, and wastes to service the cell.
38
Do larger organisms have larger cells or just more cells?
More cells as we want the surface area of cells as cell exchange a lot of material with their surroundings
39
What is the endoplasmic reticulum (ER)?
An organelle consisting of a network of membranes within the cytoplasm of eukaryotic cells that is important in protein synthesis and folding and is involved in the transport of cellular materials.
40
What is the smooth ER?
The smooth ER functions by the synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons, and storage of calcium ions. It is called smooth ER because it does not have ribosomes on its outer surface.
41
What is the rough ER?
Its main function is to produce proteins. It is made up of cisternae, tubules and vesicles. It is called the rough ER because its outer surface contains ribosomes.
42
What is the nuclear envelope?
The nuclear envelope surrounds the nucleus with a double membrane with multiple pores. The pores regulate the passage of macromolecules like proteins and RNA, but permit free passage of water, ions, ATP and other small molecules.
43
What is the nucleous?
It a collection of ribosomal RNA and proteins along with ribosomal genes and processing enzymes. The role of the nucleolus is to process RNA into ribosomes.
44
What is the chromotin?
The function of chromatin is to efficiently package DNA into a small volume to fit into the nucleus of a cell and protect the DNA structure and sequence.
45
What is the Golgi apparatus?
An organelle which has major functions of modifying, sorting and packaging of proteins for secretion. It is also involved in the transport of lipids around the cell, and the creation of lysosomes. The sacs or folds of the Golgi apparatus are called cisternae.
46
What is the lysosome in the cell?
Digestive organelles where macromolecules are hydrolysed.
47
What is the mitochondrion in the cell?
The organelle where cellular respiration occurs and most ATP is generated.
48
What is peroxisome in the cell?
An organelle with various specialised metabolic functions; produces hydrogen peroxide as a by-product and then converts it to water.
49
What is the microvilli?
Projections that increase the cell's surface area
50
What is the cytoskelleton?
This reinforces the cells shape and functions in cell movement
51
What are microfilaments?
Microfilaments assist with cell movement and are made of a protein called actin. Actin works with another protein called myosin to produce muscle movements, cell division, and cytoplasmic streaming. Microfilaments keep organelles in place within the cell.
52
What are Intermediate filaments?
The most important function of intermediate filaments is to provide mechanical support for the plasma membrane where it comes into contact with other cells or with the extracellular matrix. Unlike microfilaments and microtubules, intermediate filaments do not participate in cell motility.
53
What are Microtubles?
Microtubules are hollow, fibrous shafts whose main function is to help support and give shape to the cell. They also serve a transportation function, as they are the routes upon which organelles move through the cell.
54
What is the centrosome?
The region where the cells microtubes are initiated. It contains a pair of centrioles.
55
What is the flagellum?
A motility structure present in some animal cells. A flagellum is a whip-like structure that allows a cell to move
56
What is the central vacuole?
A predominant organelle in older plant cells. Its functions include storage, the breakdown of waste products, and hydrolysis of macromolecules. Enlargement of the vacuole is a major mechanism of plant growth.
57
Is all the DNA in the cell located in the nucleus?
No it is also located in the mitochondria and chloroplasts.
58
What encloses the nucleus?
The nuclear envelope which separates its contents from the cytoplasm.
59
What is the nuclear envelope perforated by?
Pore structures
60
What is the pore complex?
An intricate protein structure that lines each pore of the nuclear envelope and plays an important role in the cell by regulating the entry and exit of proteins and RNAs as well as large macromolecules.
61
What is the nuclear lamina?
A netlike array of protein filaments that maintain the shape of the nucleus by mechanically supporting the nuclear envelope
62
What is the nuclear matrix?
A framework of protein fibres extending throughout the nuclear interior.
63
What do the nuclear lamina and matrix do?
They may help organise the genetic material so it functions efficiently.
64
What is the chromatin?
The complex of DNA and proteins making up chromosomes.
65
How many chromosomes does a typical human cell have in its nucleus?
46
66
What is the nucelolus?
A small body in the nucleus of a cell that contains protein and RNA and is the site for the synthesis of ribosomal RNA and for the formation of ribosomal subunits.
67
Where is rRNA synthesised?
in the nucelolus
68
Where are free ribosomes suspended in the cell?
In the cytosol
69
Where the the bound ribosomes in the cell?
attached to the outside of the endoplasmic reticulum or nuclear envelope.
70
True to False? free and bound ribosomes are structurally identical.
True
71
What do free ribosomes do?
The proteins from these ribosomes usually make enzymes that catalyse the first steps of sugar
72
What do bound ribosomes do?
Generally make proteins that are destined for insertion into membranes for packaging within certain organelles such as lysosomes or for export from the cell
73
What tasks does the endomembrane system carry out?
The synthesis of proteins, transport of proteins into membranes and organelles
or out of the cell, metabolism and movement of lipids, and detoxification of poisons.
74
What is the endoplasmic reticulum (ER)?
An organelle consisting of a network of membranes within the cytoplasm of eukaryotic cells that is important in protein synthesis and folding and is involved in the transport of cellular materials.
75
True or False the endoplasmic reticulum accounts for all of the total membrane in eukaryotic cells.
False it accounts for over half.
76
When is smooth ER in cells used and where?
In the sex reproductive organs and the liver because it can synthesise sex hormones and detoxify drugs and poisons.
77
What disorder is smooth ER linked to?
Drug and alcohol overdose and addiction as these drugs in the liver increase the number of smooth ER cells in the liver increasing the tolerance to the drug meaning more of the drug is needed to have an effect.
78
What is the endoplasmic reticulum ER made up of?
A membranous system of interconnected tubules and flattened sacs called cisternae. The membrane of the ER encloses a continuous compartment called the ER lumen (or cisternal space). Rough ER, which is studded on its outer surface with ribosomes, can be distinguished from smooth ER in the electron micrograph (TEM).
79
What are most secretory proteins?
Glycoproteins.
80
What are glycoproteins?
Proteins with carbohydrates covalently bonded to them.
81
Where and how are the carbohydrates attached to proteins?
They are attached to the proteins in the ER lumen by enzymes built into the ER membrane.
82
How do secretory proteins leave depart the ER in the cell?
Wrapped in the membranes of vesicles that bud like bubbles to from a specialised region called the transitional ER
83
Whats an easy way to think of the golgi apparatus?
As a warehouse for receiving, sorting, shipping, and even some manufacturing.
84
What occurs in the Golgi Apparatus?
Products of the ER such as proteins are modified, stored, then sent to other destinations. It is especially extensive in cells specialised for secretion.
85
What does the Golgi Apparatus consist of?
A group of associated, flattened membranous sacs (Cisternae) aka stacks.
86
What does the cis face of the Golgi Apparatus do?
It is located near the ER. Transport vesicles move material to this site by fusing with the Golgi Apparatus of this face.
87
What does the trans face of the Golgi Apparatus do?
This 'face' gives rise to vesicles that pinch off and travel to other sites. This site faces the plasma membrane.
88
True or False? Products of the ER stay the same during their transit between the cis face and the trans face of the Golgi Apparatus.
False, they are usually modified during this transit.
89
True or False? The Golgi Apparatus can manufacture some macromolecules.
True!
90
What does research suggest the model of the Golgi Apparatus look like?
Its been suggested the central regions of the cisternae may remain in place while the outer ends are more dynamic.
91
True or False? A Golgi stack can sort the products and target them for various parts of the cell.
True.
92
What is a lysosome?
A membranous sac of hydrolytic enzymes that many eukaryotic cells use to digest (hydrolyse)
93
What are Lysosomal enzymes?
Lysosomal enzymes degrade (break down) macromolecules (large molecules) and other materials (such as bacteria) that have been taken up by the cell during the process of endocytosis.
94
If a lysosome breaks open or leaks its contents what effect does this have on the released enzymes?
The released enzymes are then not very active because the cytosol has a near neutral pH. If the leakage is big enough a large number of lysosomes can actually destroy the cell through self-digestion.
95
What is the lysosomal membrane?
The lysosomal membrane, which has a typical single phospholipid bilayer, controls the passage of material into and out of lysosomes, by its permeability and ability to fuse with digestive vacuoles or engulf cytosolic material.
96
What are hydrolytic enzymes?
Any enzyme that catalyses the hydrolysis (add water) of a chemical bond.
97
How is the hydrolytic enzymes and the lysosomal membrane made?
By the rough ER and then transferred to the Golgi apparatus for further processing.
98
How are the proteins of the inner surface of the lysosomal membrane and the digestive system spared from destruction?
Apparently the 3-Dimensional shapes of these proteins protect vulnerable bonds from enzymatic attack.
99
How do lysosomes carry out intracellular digestion?
In various ways. The food vacuole fuses with a lysosome whose enzymes (hydrolytic) digest the food in the cell. Digestion products then pass into the cytosol and become nutrients for the cell.
100
What is the phagocytosis?
Phagocytosis is the process by which a cell uses its plasma membrane to engulf a large particle, giving rise to an internal compartment called the phagosome.
101
What is the food vacuole?
Food vacuoles are membrane-bound sacs within a cell, which contain food matter to be digested. These can be thought of as intracellular “stomachs,” where food is stored while it is broken down and its nutrients are extracted.
102
Which human cells carry out phagocytosis?
Macrophages a type of white blood cell that helps defend the body by eating and destroying bacteria and other invaders.
103
What is autophagy?
Where lysosomes recycle intracellular materials. The damaged organelle becomes surrounded by a double membrane and the a lysosome fuses with the outer membrane of the vesicle. Then the hydrolytic enzymes digest the organelle compartments and they are released into the cytosol for reuse. This allows the cell to constantly renew itself.
104
What happens to people with diseases that lack the functioning hydrolytic enzyme normally present in the lysosomes?
The lysosomes become engorged with indigestible material which begins to interfere with other cellular activity's.
105
What is Tay-Sachs disease?
Where a lipid-digesting enzyme is missing or inactive and the brain becomes impaired by an accumulation of lipids in the cells. Although these type of diseases are quite rare.
106
Where are vacuoles derived from?
Large vesicles derived from the endoplasmic reticulum and the Golgi apparatus.
107
True or False, The vacuole membrane is selective in transporting solutes
True
108
What are contractile vacuoles?
A contractile vacuole is a sub-cellular structure involved in osmoregulation. It is found predominantly in protists and in unicellular algae.
109
How can vacuoles help protect a plant from herbivores?
By storing compounds that are poisonous or unpalatable to animals.
110
What is a central vacuole in a plant?
The central vacuole is a large vacuole found inside of plant cells. The central vacuole stores water and maintains turgor pressure in a plant cell. It also pushes the contents of the cell toward the cell membrane, which allows the plant cells to take in more light energy for making food through photosynthesis.
111
True or False? The central vacuole of a plant is usually the smallest compartment of the cell.
False, it is usually the largest.
112
In eukaryotic cells which organelles are involved in the conversion of energy to allow cells to do work?
The mitochondria and chloroplasts
113
What does the mitochondra do?
This is the site for cellular respiration, the metabolic process that uses oxygen to drive the generation of ATP by extracting energy from sugars, fats, and other fuels.
114
What do the chloroplasts do in terms of energy transfer?
Chloroplasts found in plants and algae are the sites of photosynthesis which converts solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from carbondioxide and water.
115
True or False, Chloroplasts and the mitochondria have similar evolutionary origins.
True
116
What is the endosymbiont theory?
That an early ancestor of eukaryotic cells engulfed an oxygen-using non-photosynthetic prokaryotic cell. Eventually the engulfed cell formed a relationship with the host cell in which it was enclosed, becoming an endosymbiont. Over the course of evolution the host cell and its endosymbiont merged into a single organism, a eukaryotic cell with a mitochondrion. One of these cells may have taken up a photosynthetic prokaryotic becoming the ancestor of eukaryotic cells that contain chloroplasts.
117
What is a endosymbiont?
An endosymbiont is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship.
118
What are the organelles in eukaryotic cells that convert energy to forms that cells can use for work?
The mitochondria and chloroplasts
119
What are mitochondria the sites of?
Cellular respiration
120
What are chloroplasts the site of?
Photosynthesis
121
True or False? The mitochondria and chloroplasts have similar evolutionary origins.
True
122
What does autonomous mean?
Somewhat independant
123
True or False? The mitochondria and chloroplasts are not autonomous.
False
124
True or False? The mitochondria is found in only some eukaryotic cell.
False, it is found in nearly all eukaryotic cells including those of plants, animals, fungi, and most unicellular eukaryotes.
125
Which is more common, a single large mitochondria in the cell or hundreds or even thousands of smaller mitochondria?
hundreds or even thousands of smaller mitochondria
126
What factor influences how many mitochondria a cell has?
The cells level of metabolic activity, foe example cells that move or contract have proportionally more mitochondria per volume than less active cells.
127
Is the outer membrane of the mitochondria smooth or soft?
Smooth
128
What Is the inner membrane of the mitochondria like?
It in convoluted (complex) with foldings (cristae)
129
What is cristae?
A cristae is a fold in the inner membrane of a mitochondrion and it gives the inner membrane its characteristic wrinkled shape, providing a large amount of surface area for chemical reactions to occur on.
130
What are the two compartments of the inner membrane?
The inter-membrane space and the mitochondrial matrix.
131
What do some of the enzymes in the mitochondrial matrix do?
Catalyse some of the steps of cellular respiration
132
What do some of the enzymes in the inner-membrane space do?
Proteins that function in respiration for example the enzyme that makes ATP are built into the inner-membrane space
133
What pigment do chloroplasts contain?
The green pigment chlorophyll
134
Where are chloroplasts found?
In leaves and other green organs of plants and in algae
135
What sits in between the contents of a chloroplast and the cytosol?
By an envelope consisting of two membranes separated by a very narrow inter-membrane space
136
What are thylakoids?
Flattened interconnected sacs inside chloroplasts.
137
What is a granum?
A stack of thylakoids
138
What is the stroma?
The fluid outside the thylakoids which contains the chloroplast DNA and ribosomes as well as many enzymes
139
What are the 3 compartments of the chloroplast space and what do they enable?
The inter-membrane space, the stroma, and the thylakoid space. This organisation enables the chloroplast to convert light energy to chemical energy during photosynthesis.
140
True or False, the shape of chloroplasts is changeable, they grow and occasionally pinch in two
True
141
How does the mitochondria, chloroplasts and other organelles typically move around the cell?
Along tracks of the cytoskelleton
142
What family do chloroplasts belong to?
The plastids
143
What is amyloplast?
A colourless organelle that stores starch (amylose)
144
What is chromoplast?
A plastic that has pigments that give fruits and flowers their orange and yellow hues.
145
What is the perioxisome?
A specialized metabolic compartment bounded by a single membrane. They contain enzymes that remove hydrogen atoms from various substrates and transfer them to oxygen producing hydrogen peroxide as a by-product.
146
What are a few functions of the peroxisome reactions?
1. Some use oxygen to break fatty acids down into smaller molecules that are transported to mitochondria and used for fuel for cellular respiration
2. Peroxisomes in the liver detoxify alcohol and other harmful compounds by transferring hydrogen from the poisonous compounds to oxygen.
147
Is hydrogen peroxide H2O2 toxic or safe?
toxic but the organelle also contains an enzyme that converts H202 to water.
148
What are glyoxysomes?
Specialized peroxisomes that are found in the fat-storing issues of plant seeds. They contain enzymes that initiate the conversion of fatty acids to sugar which the emerging seedling uses as a source of energy and carbon until in can produce its own sugar by photosynthesis.
149
How do peroxisomes grow larger?
By incorporating proteins made in the cytosol and ER as well as lipids made in the ER and within the peroxisome itself. They may increase in number by splitting in two when they reach a certain size
150
What is the cytoskeleton?
A network of fibres extending throughout the cytoplasm. Through a series of intercellular proteins, the cytoskeleton gives a cell its shape, offers support, and facilitates movement through three main components: microfilaments, intermediate filaments, and microtubules.
151
What are the three types of molecular structures of the eukaryotic cytoskeleton?
Microtubules, microfilaments, and intermediate filaments.
152
What is the main and most obvious function of the cytoskeleton?
To give mechanical support to the cell and maintain its shape. This is especially important for animal cells, which lack walls.
153
How is the cytoskeleton stabilized?
By a balance between opposing forces exerted by its elements.
154
Which is more dynamic? A cytoskeleton or an animal skeleton?
The cytoskeleton, however, It can be quickly dismantled in one part of the cell and reassembled in a new location, changing the shape of the cell
155
What does the term cell motility include?
both changes in cell location and movements of cell parts. Cell motility generally requires interaction of the cytoskeleton with motor proteins.
156
What is an easy way to view to cytoskeleton?
The cytoskeleton is like the structure of the building, the motor proteins are the workers transporting the materials (organelles) around to building for construction.
157
Which is biggest, microtubules, microfilaments, or intermediate filaments.
Microtubules
158
What is the function of microtubles?
Maintenance of cell shape, cell motility (as in cilia or flagella); chromosome movements in cell division; organelle movements
159
What is the function of microfilaments?
Maintenance of cell shape; changes in cell shape; muscle contraction; cytoplasmic streaming in plant cells; cell motility (as in amoeboid movement); division of animal cells
160
What is the function of intermediate filaments?
Maintenance of cell shape (tension- bearing elements); anchorage of nucleus and certain other organelles; formation of nuclear lamina
161
What is the function of microtubles?
Maintenance of cell shape, cell motility (as in cilia or flagella); chromosome movements in cell division; organelle movements. They guide vesicles from the ER to the Golgi apparatus and from the Golgi to the plasma membrane. Microtubules are also involved in the separation of chromosomes during cell division
162
What are microtubules made up of?
Globular proteins called tubulin. Each tubulin protein is a dimer, a molecule made up of two sub- units. A tubulin dimer consists of two slightly different polypeptides, α-tubulin and β-tubulin.
163
How do microtubules grow in length?
By the addition of tubulin dimers
164
What is the plus end of the microtubules?
The end that can accumulate or release tubulin dimers at a much higher rate than the other, thus growing and shrinking significantly during cellular activities.
165
What do microtubules grow out of?
A centrosome
166
What is the centrosome?
A region that is often located near the nucleus, Within the centrosome is a pair of centrioles, each composed of nine sets of triplet microtubules arranged in a ring
167
What do centrosomes help with?
Centrosomes with centrioles may help organize microtubule assembly in animal cells, Although many other eukaryotic cells lack centrosomes with centrioles and instead organize microtubules by other means.
168
What are flagella?
A flagellum is a whip-like structure that allows a cell to move.
169
What are cilia?
Cilia are little appendages that stick out from eukaryotic cells. They whip back and forth and help cells move around in cellular fluids. They also help particles move past the cell.
170
How are most unicellular eukaryotes propelled through water?
By cilia or flagella that act as locomotor appendages, and the sperm of animals, algae, and some plants have flagella.
171
What does the ciliated lining of the trachea do?
Sweeps mucus containing trapped debris out of the lungs
172
In a woman’s reproductive tract, the cilia lining the oviducts does what?
Helps move an egg towards the uterus.
173
What kind of motion does a flagella have?
Undulating motion like the tail of a fish
174
What kind of motion does a cilia have?
Alternating power and recovery strokes, much like the oars of a racing crew boat
175
If a cilium can act as a signal-receiving “antenna” for the cell they are generally what?
nonmotile aka, not capable of movement.
176
What is a basal body?
Basal bodies are barrel-like microtubular structures located near the cell surface that provide the template for the nine-fold symmetry upon which the cilium and flagellum is assembled.
177
How does the microtubule assembly produce the bending movements of flagella and motile cilia?
Bending involves large motor proteins called dyneins . A typical dynein protein has two “feet” that “walk” along the microtubule of the adjacent doublet, using ATP for energy. One foot maintains contact, while the other releases and reattaches one step farther along the microtubule. If the doublets were not held in place, the walking action would make them slide past each other. Instead, the movements of the dynein feet cause the microtubules—and the organelle
as a whole—to bend.
178
The outer doublets and two central microtubules are held together by what?
Flexible cross-linking proteins
179
What are microfilaments?
Thin solid rods. They are also called actin filaments because they are built from molecules of actin, a globular protein. A microfilament is a twisted double chain of actin subunits
180
True or False? Microfilaments seem to be present in all eukaryotic cells.
True
181
What is the structural role of microfilaments in the cytoskeleton?
To bear tension (pulling forces)
182
True or False? In some kinds of animal cells, such as nutrient-absorbing intestinal cells, bundles of microfilaments make up the core of microvilli, delicate projections that increase the cell’s surface area
True
183
Microfilaments are well known for their role in what?
Cell motility
184
What is myosin?
A fibrous protein which forms (together with actin) the contractile filaments of muscle cells and is also involved in motion in other types of cell.
185
What is pseudopodia?
A temporary protrusion of the surface of an amoeboid cell for movement and feeding.
186
What is cytoplasmic streaming?
A circular flow of cytoplasm within cells. It is the movement of the fluid substance (cytoplasm) within a plant or animal cell. The motion transports nutrients, proteins, and organelles within cells.
187
What are Intermediate filaments?
Intermediate filaments are only found in the cells of some animals, including vertebrates. Specialized for bearing tension. each type is constructed from a particular molecular subunit belong- ing to a family of proteins whose members include the keratins.
188
Even when our cells die can intermediate filaments still exist?
Yes, for example the outer layer of our skin consists of dead skin cells full of keratin filaments
189
Chemical treatments that remove microfilaments and microtubules from the cytoplasm of living cells leave a web of intermediate filaments that retains its original shape. Why do the intermediate filaments remain?
Such experiments suggest that intermediate filaments are especially sturdy and that they play an important role in reinforcing the shape of a cell and fixing the position of certain organelles.
