Chapter 3- The cell Flashcards
1
Q
Spontaneous generation
A
The idea that life can arise from nonliving matter. Aristotle stated that living organisms could come from nonliving material if the material contained “vital heat” (pneuma). He used the fact that animals could appear in new environments that they hadn’t been before, like fish in a puddle of water. The theory persisted until the 17th century
2
Q
Redi’s research on spontaneous generation
A
Refuted that idea that maggots spontaneously generate on meat left in the open air. He left meat in open jars and left more meat in covered jars. Maggots only appeared in the uncovered jars that were exposed to air and could be accessed by flies
3
Q
Spallanzani’s research on spontaneous generation
A
Preformed hundreds of experiments using heated broth. Contrary to Needham’s results, heated but sealed flasks were clear, and did develop microorganisms unless they were exposed to air. This suggests that microbes could be introduced from the air. Needham argued that spontaneous generation came from a life force that had been destroyed by the boiling in the experiment.
4
Q
How did Pasteur’s research disprove spontaneous generation?
A
He created swan neck flasks, which had long and twisted necks. He boiled broth in the flasks. The design of these flasks allowed air to be exchanged between the inside and outside of the flasks, but prevented any microorganisms from entering through the air, as they would be trapped in the neck of the flask. The broth in the flasks remained sterile unless the necks were broken- if the necks were broken, the broth would become cloudy. This disproved spontaneous generation, because any “life source” other than microorganisms would still have access to the broth. This was also the basis of germ theory, because Pasteur suggested that if microbes could cause food spoilage, they could also cause disease
5
Q
Matthias Schleiden
A
A German botanist who observed plant tissues under a microscope and observed that the tissues were composed of cells. Plant cells are easier to visualize because they are separated by thick cell walls.
6
Q
Theodor Schwann
A
German physiologist who realized the similarities between plant and animal tissues. He had the idea that cells were the fundamental components of both plant and animal tissues
7
Q
How was modern cell theory discovered?
A
Two Polish scientists Remak and Virchow published research stating that cells derived from other cells as a result of cell division, and that all cells arise from other cells. These are the 2 main tenets of cell theory.
8
Q
Endosymbiotic theory
A
The idea that mitochondria and chloroplasts arose as a result of prokaryotic cells establishing a symbiotic relationship within a eukaryotic host. Mitochondria and chloroplasts have their own DNA which is closely related bacteria in DNA sequence and chromosome structure. Mitochondrial and chloroplast ribosomes are also similar to bacterial ribosomes in structure rather than being similar to the eukaryotic ribosomes of the host cells. These organelles also reproduce through binary fission, like bacteria, rather than through mitosis, which is how eukaryotic cells reproduce.
9
Q
How did eukaryotes evolve from prokaryotes (3 steps)
A
- Infoldings of the plasma membrane of an early cell brought about membrane bound components like the nucleus and the endoplasmic reticulum
- The ancestral eukaryote consumed aerobic bacteria that evolved into mitochondria
- The early eukaryote consumed photosynthetic bacteria that evolved into chloroplasts
10
Q
Germ theory of disease
A
States that diseases may result from microbial infection. Fracastoro was a proponent of this in the 16th century, but it was not widely accepted until the 19th century
11
Q
Semmelweis’s research and the germ theory
A
An obstetrician observed that pregnant women were more likely to die when examined by doctors and medical students, who frequently performed autopsies and then examined patients without washing their hands. He proposed that physicians were somehow transferring the causative agent of disease. When physicians washed their hands, the mortality rate dropped drastically.
12
Q
Snow’s research and the germ theory
A
John Snow’s research represented the first epidemiological study. He conducted a study to determine the source of cholera outbreaks and traced it to two water sources that had been contaminated by sewage. Therefore, he determined that cholera bacteria were transmitted via drinking water and that disease could be transmitted through contaminated items.
13
Q
Lister’s research and germ theory
A
Lister was a British surgeon who attempted to determine the cause of postsurgical infections (50% of surgical patients died from postsurgical infections). Lister promoted handwashing and cleanliness during surgery, and began using a carbolic acid spray as a disinfectant and antiseptic during surgery. These techniques later became standard medical practice
14
Q
Koch’s research and the germ theory
A
He proposed postulates based on the idea that the cause of a specific disease could be attributed to a specific microbe. Using these postulates, Koch identified the causative pathogens of anthrax, tuberculosis, and cholera. The “one microbe, one disease” concept marked a shift from miasma theory to germ theory
15
Q
Basic fundamental components of the cell (4)
A
- Cytoplasm
- Plasma membrane- contains the cytoplasm
- One or more chromosomes that contain the genetic blueprints of the cell
- Ribosomes
16
Q
Cytoplasm
A
A gel like substance composed of water and dissolved chemicals needed for growth. Contained in the plasma membrane
17
Q
Ribosomes
A
Organelles used for the production of proteins
18
Q
Two main categories of cells
A
- Prokaryotic
- Eukaryotic
19
Q
Prokaryotic cells
A
Lack a nucleus surrounded by a nuclear membrane. They usually have a single circular chromosome located in a nucleoid. They are classified within the domains as Archaea and Bacteria
20
Q
Eukaryotic cells
A
Have a nucleus surrounded by a nuclear membrane that contains multiple rod shaped chromosomes. All plant and animal cells are eukaryotic and eukaryotes are classified in the domain Eukarya.
21
Q
Cell morphology
A
The shape of the cell. In prokaryotes, there are 6 possible cell morphologies.
22
Q
6 prokaryotic cell shapes
A
Coccus, bacillus, vibrio, coccobacillus, spirillum, and spirochete
23
Q
Prokaryotic cell arrangements (6)
A
- Coccus- single coccus
- Diplococcus- pair of two cocci
- Tetrad- grouping of 4 cells arranged in a square
- Streptococcus- chain of cocci
- Bacillus- single rod
- Streptobacillus- chain of rods
24
Q
Cell wall
A
Found in most prokaryotes and some eukaryotes, it maintains the cell morphology in most prokaryotic cells. It also protects the cell from changes in osmotic pressure
25
Osmotic pressure
Occurs because of differences in the concentration of solutes on each side of the plasma membrane. Water can pass through the semipermeable membrane, but solutes like salts and sugars can't.
26
Osmosis
Diffusion of water that occurs when solute concentration on each side of the membrane is unequal. Water moves from high to low concentration of solutes until the concentration is equal on both sides.
27
Isotonic medium
The solute concentration inside and outside the cell are equal- there's no net movement of water
28
Hypertonic medium
The solute concentration outside the cell is higher than the concentration inside the cell. Water diffuses out of the cell into the external environment. Cells become dehydrated and crenate.
29
Hypotonic medium
The solute concentration outside the cell is lower than the concentration inside the cell. Water diffuses into the cell. Cells without a cell wall are prone to lysis in this environment.
30
Tonicity
The degree to which a cell is able to withstand changes in osmotic pressure
31
Plasmolysis
Occurs in cells with a cell wall in place of crenation. The plasma membrane contracts and detaches from the cell wall. There is a decrease in interior volume but the cell wall remains intact, so the cell can maintain its shape for a period of time.
32
Prokaryotic chromosomes
They are usually circular, haploid (unpaired), and not bound by a complex nuclear membrane. In prokaryotes, DNA and DNA associated proteins are concentrated in the nucleoid region of the cell
33
Nucleoid associated proteins (NAPs)
Proteins that interact with prokaryotic DNA and assist in the organization and packaging of the chromosome. They are similar in function to histones in eukaryotic cells
34
Plasmids
Contain extrachromosomal DNA, which is not part of the chromosomes. Plasmids are small, circular, double stranded DNA molecules. Plasmids are most commonly found in bacteria, and they benefit the survival of the organism because they contain genes that code for antibiotic resistance
35
How do ribosomes differ between the 3 domains?
Prokaryotic cells contain 70s ribosomes (a measure of size) while eukaryotic cells contain ribosomes with a size of 80s. Bacterial and archaeal ribosomes are the same size but have different proteins and rRNA molecules
36
Inclusions
Cytoplasmic structures that store excess nutrients in a polymerized form. This keeps osmotic pressure under control. Some structures store glycogen and starches. Found in prokaryotic cells that live in unstable environments
37
Volutin (metachromatic) granules
Inclusions that store polymerized inorganic phosphate that can be used in metabolism and assist in the formation of biofilms
38
Sulfur granules
An inclusion that are found in sulfur bacteria of the genus Thiobacillus. They store elemental sulfur that is used for metabolism
39
Polyhydroxybutyrate (PHB)
A type of inclusion that is surrounded by a phospholipid monolayer embedded with protein
40
Magnetosomes
Inclusions of magnetic iron oxide or iron sulfide surrounded by a lipid layer. This allows for movement by aligning cells with a magnetic field
41
Carboxysome inclusions
Have outer shells made of thousands of protein subunits. They are filled with the Rubisco enzyme and carbonic anhydrase, which are used for carbon metabolism. Prokaryotic cells use these inclusions to compartmentalize the enzymes used for certain chemical reactions
42
Endospores
Structures that protect the bacterial genome in a dormant state when environmental conditions are unfavorable. They allow bacteria to survive without food and water for a period of time, as well as to survive harsh conditions like extreme temperatures and radiation. The bacteria that causes anthrax is a gram positive bacteria capable of forming endospores, which allows it to survive for decades- endospores are difficult to kill
43
Sporulation
The process by which vegetative cells transform into endospores. It can begin when nutrients are depleted or when the environment becomes unstable
44
Steps of sporulation (6)
1. DNA of the cell replicates
2. Membranes form around the DNA to form a septum that separates the DNA from the host cell
3. Forespore forms additional membranes, separating the chromosomes from the cell by a second membrane. This is the core of the endospore.
4. Protective cortex forms around the spore- composed of calcium and dipicolinic acid
5. Protein coat forms around the cortex while the DNA of the host cell disintegrates
6. Spore is released once the mother cell disintegrates
45
Germination
When endospores enter a vegetative state. This occurs when living conditions of the cell improve. After germination, the cell becomes metabolically active and can carry out all of its normal functions.
46
Cell envelope
Structures that enclose the cytoplasm and internal structures of the cell
47
Plasma membrane
All cells have a plasma membrane. It is selectively permeable and its structure is described using the fluid mosaic model. In eukaryotic cells, the membrane is a phospholipid bilayer that is formed with ester linkages and proteins. Phospholipids and proteins can move laterally in the membrane, and they also move between the two layers
48
Fluid mosaic model
The ability of membrane components to move within the membrane. The components (lipids and proteins) of the membrane have a mosaic-like composition
49
How are archaeal membranes different from bacterial and eukaryotic membranes?
Archaeal membrane phospholipids are formed with ether linkages. Also, the phospholipids have branched chains in contrast to the straight chains in bacterial and eukaryotic membranes. Some archaeal membranes are a bilayer, but others have lipid monolayers.
50
Functions of cell surface proteins
Cell to cell communication, and sensing environmental conditions and pathogenic virulence factors.
51
Glycoproteins/glycolipids
The carbohydrates (sugars) associated with the phospholipids or membrane proteins. Glycoprotein and glycolipid complexes extend out from the surface of the cell so that the cell can interact with the environment. The complexes differ between domains, so they can be used to characterize species. Different types of cells are distinguished by the structure and arrangement of glycolipids and glycoproteins. They can also act as cell surface receptors
52
Simple diffusion
Molecules moving from a higher concentration to a lower concentration across the plasma membrane. Small molecules like carbon dioxide can cross the membrane in this way
53
Facilitated diffusion
Cross the membrane from high to low concentration with the help of membrane channels or carrier molecules. This is how charged or large molecules cross the membrane
54
Active transport
When cells cross the membrane moving from low to high concentrations, against their concentration gradients. Uses structures called pumps that require ATP to work
55
Group translocation
As a molecule moves into a cell against its concentration gradient, it is chemically modified so it doesn't require assistance to be transported. An example is the bacterial phosphotransferase system, which adds phosphate ions to glucose upon entry to the cell.
56
Photosynthetic membrane structures
Some prokaryotic cells, like cyanobacteria, have membrane structures that can perform photosynthesis. Their membrane fold in, and contain photosynthetic pigments like chlorophylls
57
Main function of the cell wall
To protect the cell from harsh conditions in the outside environment
58
Peptidoglycan
The main component of bacterial cell walls. The structure of peptidoglycan looks like a meshwork. Each layer contains long chains of alternating molecules of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). Peptide bridges connect NAG and NAM in each layer, which gives the layers two dimensional tensile strength. Peptidoglycan is made inside of the cell and is then exported and assembled in layers, giving the cell its shape.
59
How does peptidoglycan structure differ between gram positive and gram negative bacteria?
In gram negative bacteria, there are tetrapeptide chains extending from each NAM unit that are directly cross linked. In gram positive bacteria, the tetrapeptide chains are linked by pentaglycine cross bridges.
60
How is peptidoglycan targeted when fighting infection?
Peptidoglycan is unique to bacteria. Therefore, some antibiotic drugs interfere with peptidoglycan synthesis, which makes the cell wall weaker and makes bacterial cells more susceptible to osmotic pressure. Some cells in the immune system can recognize bacterial pathogens by detecting peptidoglycan in the cell. The cells then engulf and destroy the bacterial cell.
61
Teichoic acids
Gram positive cell walls contain many layers of peptidoglycan. The peptidoglycan layers are embedded with teichoic acids. TAs extend through the peptidoglycan layer and make peptidoglycan more rigid, enhancing its stability. It also allows pathogenic bacteria to bind to proteins on the surface of host cells, allowing them to cause infection. The family Mycobacteriaceae contain mycolic acids in their cell wall
62
How is the structure of gram negative cells different from the structure of gram positive cells?
Gram negative cells have a thinner layer of peptidoglycan and a more complex cell envelope. In the periplasmic space between the cell wall and the plasma membrane, there is a gel like matrix. There is also a second lipid bilayer (the outer membrane) that is external to the peptidoglycan layer. Murein lipoprotein attaches the outer membrane to the peptidoglycan. There is an outer leaflet of the outer membrane that contains lipopolysaccharide (LPS)
63
Lipopolysaccharide (LPS)
Composes the outer leaflet of the outer membrane in gram negative cells. It is an endotoxin in infections, causing fever, hemorrhage, and septic shock. LPS molecules are made of Lipid 1, a core polysaccharide, and an O side chain of sugar-like molecules. The composition of the O side chain varies between different species and strains of bacteria. Parts of the O side chains act as antigens and can be detected with serological or immunological tests to diagnose infection with a specific type of bacteria.
64
How does the archaeal cell wall differ from that of bacteria?
Archaeal cell walls don't contain peptidoglycan- they contain pseudopeptidoglycan- NAM is replaced with a different subunit. In some archaea, cell walls contain glycoproteins or polysaccharides. A few archaea don't have any cell walls.
65
Glycocalyx
A sugar coat. The two types are capsules and slime layers. They allow cells to adhere to surfaces, which allows for biofilms to be formed. Biofilms are advantageous to bacterial survival in multiple ways, and are how bacteria typically exist in nature.
66
Capsule
An organized layer located outside of the cell wall and composed of polysaccharides or proteins. A capsule can make bacteria more pathogenic because it makes it difficult for certain white blood cells to engulf and kill the microbe. Capsules are also difficult to stain for microscopy.
67
Slime layer
A less tightly organized layer that is loosely attached to the cell wall and can be easily washed off. These layers are made of polysaccharides, glycoproteins, or glycolipids.
68
How are biofilms advantageous to bacterial survival?
Biofilms hold water like a sponge, preventing them from drying out. They protect the cells from predation and also prevent antibiotics and disinfectants from working.
69
S-layer
A type of cell envelope structure that is composed of structural proteins and glycoproteins. The S-layer is found outside the cell wall in bacteria. In archaea, it acts as a cell wall. In prokaryotic cells, the S-layer seems to help the cell withstand osmotic pressure and interact with the host immune system.
70
Fimbriae
Short, bristle like protein appendages that project from the cell surface. There are hundreds of fimbriae on one cell. They allow cells to attach to surfaces and to other cells, which is important for infection and virulence in pathogens, as well as biofilm formation
71
Pili
Long protein appendages that are less numerous than fimbriae. The F pilus helps bacterial cells to transfer DNA, like when bacteria share genes to gain other traits. Pili can also help the cell to attach to surfaces
72
Flagella
Stiff spiral filaments composed of flagellin protein subunits that extend outward from the cell and spin. They act as propellers in bacteria and help cells to move in aqueous environments. It's composed of a basal body that is embedded in the membrane and a hook region that connects the basal body to the filaments. Different types of bacteria have different flagella arrangements
73
Monotrichous
A bacteria with one flagellum that is typically located at one end of the cell
74
Amphitrichous
Cells that have a flagellum or tufts of flagella at each end
75
Lophotrichous
Cells that have a tuft of flagella at one end of the cell
76
Peterichous
Flagella that cover the entire surface of a bacterial cell
77
What environmental signals do bacteria respond to?
Light (phototaxis), magnetic fields (magnetotaxis), and chemical gradients (chemotaxis) most commonly
78
How do bacteria purposefully move toward/away from something?
The lengths of runs (rotating in a counterclockwise direction to move forward) is increased and the length of tumbles are decreased. Tumbling helps with orienting the bacteria toward an attractant, but it means that flagella are splayed out while rotating clockwise, which prevents significant forward movement. When no chemical gradient exists, overall movement is more random and the lengths of runs and tumbles are more equal
79
Cytoskeleton
In eukaryotic cells, an internal network that supports transport of intracellular components and helps maintain cell shape. It is made of microfilaments, intermediate filaments, and microtubules. It holds organelles in place, provides a network over which materials can be transported, and provides structural support. Transport vesicle move throughout the cell via the cytoskeletal network
80
Cell morphologies in eukaryotic cells
There are many possible shapes- spherical, oval, cube, cylinder, flat, lenticular, fusiform, crescent, ring, polygonal. Some cells are irregular in shape and some can change shape. The shape is influenced by many factors, including the physical pressure exerted by the environment, the organization of the cytoplasm, and its primary function
81
Nucleus
Having a nucleus is a unique characteristic of eukaryotic cells. The nucleus is bound by a membrane and contains the cell's genome, which is usually organized in linear chromosomes. This means that the nucleus controls the cell and plays a role in reproduction and heredity. The DNA is highly organized and condensed using histones to fit inside the nucleus
82
Coenocytes
Cells whose nuclei divide, but whose cytoplasm do not
83
Nuclear envelope
Another name for the nuclear membrane. It consists of two lipid bilayers that come into contact with each other. Each membrane has unique proteins on its inner and outer surfaces. The nuclear envelope has protein complexes called nuclear pores, which control the movement of materials into and out of the nucleus
84
Nuclear lamina
A meshwork of intermediate filaments that is found outside the nuclear envelope membranes. It is responsible for determining the shape the nucleus
85
Mitosis
The process of clonal reproduction in eukaryotic cells. This is an asexual process because a single parent creates two identical daughter cells. This is different from binary fission because the cell's chromosomes are replicated and divided among the daughter cells. The two phases are interphase and the mitotic phase
86
Interphase
The cell is undergoing normal growth processes and DNA is replicated to prepare for cell division. The cell is not dividing at this point. The 3 stages are G1, S, and G2
87
Mitotic phase of mitosis
Duplicated chromosomes are aligned, separated, and move to opposite poles of the cell. The chromosomes are then divided into 2 daughter cells. Consists of karyokinesis and cytokinesis
88
Karyokinesis
The nuclear division part of the mitotic phase of mitosis- consists of prophase, prometaphase, metaphase, anaphase, and telophase. These steps result in the division of the cell nucleus
89
Cytokinesis
The second portion of the mitotic phase. It involves the physical separation of the cytoplasmic components into the two daughter cells
90
Meiosis
Sexual reproduction of microorganisms. It involves 2 separate nuclear divisions and creates 4 genetically distinct gametes. Each gamete contains half the number of chromosomes found in the original cell and forms a diploid cell during fertilization
91
Nucleolus
A region of the nucleus where ribosomal RNA (rRNA) biosynthesis occurs. It's also the site where ribosome assembly begins. rRNA and proteins form preribosomal complexes in the nucleolus and are transported into the cytoplasm, where ribosomal assembly is completed.
92
80s ribosomes
Contain a small 40s subunit and a large 60s subunit. Ribosomes in eukaryotic cells that are not associated with organelles are 80s. Mitochondria and chloroplasts have 70s ribosomes that are the same size as those found in prokaryotic cells.
93
Free ribosomes vs membrane bound ribosomes
Describe the location of eukaryotic ribosomes in the cell. Free ribosomes are found in the cytoplasm and synthesize water soluble proteins. Membrane bound ribosomes are found attached to the rough ER and make proteins for insertion into the cell membrane or proteins destined for export from the cell
94
How are the differences between eukaryotic and prokaryotic ribosomes clinically relevant?
Certain antibiotics target only eukaryotic ribosomes or only prokaryotic ribosomes. Human cells are eukaryotic, so they won't be harmed by antibiotics that destroy prokaryotic ribosomes. However, negative side effects can occur because mitochondria contain prokaryotic ribosomes.
95
Endomembrane system
A series of membranous tubules, sacs, and flattened disks that synthesize many cell components and move materials around in the cell. It's composed of some organelles and the connections between them. This is specific to eukaryotic cells, which need a system to transport materials that can't be dispersed by diffusion. These cells are large and need extra help to transport things
96
Endoplasmic reticulum
An interconnected array of tubules and cisternae (flattened sacs) with a single lipid bilayer. Composed of the rough endoplasmic reticulum and the smooth endoplasmic reticulum- each section synthesizes different molecules
97
Lumen of the ER
Spaces inside of the cisternae (flattened sacs)
98
Rough endoplasmic reticulum
Studded with ribosomes bound on the cytoplasmic side of the membrane. These ribosomes make proteins for the plasma membrane. Once they are synthesized, the proteins are inserted into the membrane of the RER. Newly synthesized proteins are packaged in transport vesicles, which bud off the RER and bring proteins to the small membrane or the Golgi apparatus.
99
Transport vesicles
Single lipid, bilayer, membranous spheres with hollow interiors that are used to carry molecules
100
Smooth endoplasmic reticulum
Appears smooth because it doesn't have ribosomes. It synthesizes lipids, is responsible for carbohydrate metabolism, and detoxifies toxic compounds within the cell
101
Golgi apparatus
A series of membranous discs (dictyosomes), that each have a single lipid bilayer and are stacked together. Enzymes in the Golgi apparatus modify lipids and proteins transported from the ER to the Golgi and can add carbohydrate components to them. This produces glycolipids, glycoproteins, or proteoglycans. Glycolipids and glycoproteins can be inserted into the plasma membrane and are used for signal recognition by other cells.
102
How do transport vesicles move through the Golgi apparatus?
Transport vesicles that leave the ER fuse with the Golgi apparatus on its receiving (cis) face. The proteins are modified in the Golgi apparatus. Transport vesicles containing the modified proteins leave the Golgi apparatus on the outgoing (trans) face. The outgoing vesicles will eventually fuse with the plasma membrane or the membrane of other organelles
103
Exocytosis
The process by which secretory vesicles (membranous sacs) release their contents to the cell's exterior. All cells have constitutive secretory pathways where secretory vesicles continuously transport soluble proteins out of the cell. Some cells have regulated secretion pathways, where substances are only released in response to certain signals and events
104
Lysosomes
Organelles of the endomembrane system that contain digestive enzymes. They can break down food, cellular debris, microorganisms, or immune complexes. The enzymes are contained in the lysosomes so they won't harm the rest of the cell
105
Peroxisomes
Membrane bound organelles that are not part of the endomembrane system. They form independently in the cytoplasm from when peroxin proteins are synthesized by free ribosomes, and these proteins are then incorporated into existing peroxisomes. Peroxisomes produce hydrogen peroxide to break down molecules like uric acid, amino acids, and fatty acids. They also contain catalase (an enzyme) which degrades hydrogen peroxide. They also play a role in lipid synthesis. The peroxisomes of certain organisms are specialized to meet their functional needs
106
Microfilaments
Composed of 2 intertwined strands of actin. Each one is composed of actin monomers that form filamentous cables. Actin filaments work together with motor proteins like myosin to allow for muscle contraction. In ameboid organisms, actin can exist in a stiff and polymerized gel form and a fluid unpolymerized soluble form. Actin is used for movement in these organisms
107
Pseudopodia
Temporary extensions of the cytoplasmic membrane. They are produced by the forward flow of soluble actin filaments into the pseudopodia. They are followed by the gel cycling of actin filaments, allowing for cell motility. To form pseudopodia, the cytoplasm extends outward and the remaining cytoplasm moves forward, making the cell move forward
108
Functions of microfilaments
Cellular movement (like with pseudopodia), cytoplasmic streaming (circulation of cytoplasm in the cell), cleavage furrow formation during cell division, and muscle movement in animals. Microfilaments are dynamic and can polymerize and depolymerize in response to cellular signals and interactions with other parts of the cell
109
Components of the internal cytoskeleton (3)
1. Microfilaments
2. Intermediate filaments
3. Microtubules
110
Intermediate filaments
Cytoskeletal filaments that act as cables within the cell. They are composed of strands of polymerized subunits that are made up of a wide variety of monomers. They maintain the position of the nucleus, form the nuclear lamina, and anchor the cells together in animal tissues. Desmin is an intermediate filament found in desmosomes, which joins muscle cells together
111
Nuclear lamina
The lining/layer found just inside the nuclear envelope
112
Microtubules
Cytoskeletal filaments composed of tubulin dimers (alpha and beta tubulin). They form hollow tubes that are the framework of the cytoskeleton. They are dynamic and can assemble and disassemble rapidly. Microtubules work with motor proteins like dynein and kinesin to move organelles and vesicles around inside the cytoplasm. They are also the main components of flagella and cilia in eukaryotic cells
113
Centrosomes
Produce the mitotic spindle that separates chromosomes during mitosis and meiosis. The mitotic spindle organizes microtubules at either end of the cell. Centrosomes are composed of pairs of centrioles
114
Mitochondria
The organelle where aerobic cellular respiration occurs. It has its own (bacterial) genome and 70s ribosomes. The bacterial genome supports the endosymbiotic theory
115
Structure of the mitochondria
The mitochondria has two lipid membranes. The outer membrane is derived from the eukaryotic host cell's membrane, while the inner membrane is derived from the bacterial plasma membrane. The electron transport chain for aerobic respiration uses integral proteins embedded in the inner membrane. Invaginations of the inner membrane (cristae) increase surface area for the location of biochemical reactions. Folding patterns of the cristae differ among various types of eukaryotic cells
116
Mitochondrial matrix
Corresponds to the location of the original bacterium's cytoplasm. It contains metabolic enzymes, mitochondrial DNA, and 70s ribosomes
117
What is the purpose of chloroplasts?
Photosynthesis
118
Structure of chloroplasts
Contains 3 membranes: outer, inner, and thylakoid. The stroma is located inside the outer and inner membranes, It is a gel like fluid that makes up most of the chloroplast. The thylakoid system floats in the stroma. It is a collection of folded membrane sacs where the photosynthetic pigment chlorophyll is found and the light reactions of photosynthesis occur. In plants, the thylakoids are arranged in stacks (grana), while in algae, they are free floating
119
How are eukaryotic plasma membranes different from prokaryotic plasma membranes?
Eukaryotic membranes contain sterols like cholesterol that change membrane fluidity. Also, some eukaryotic cells contain specialized lipids like sphingolipids. They play a role in maintaining membrane stability and are involved in signal transduction pathways and cell to cell communication
120
Endocytosis
The uptake of matter through folding in of the plasma membrane and vesicle formation. This is a unique ability of eukaryotic cells. Includes phagocytosis and pinocytosis
121
Phagocytosis
Particles or other cells are enclosed in a pocket (folding in) within the membrane, which pinches off from the membrane to form a vacuole that surrounds the particle, located inside of the cell
122
Pinocytosis
Small, dissolved materials and liquids and taken into the cell through small vesicles.
123
Receptor mediated endocytosis
A type of endocytosis initiated by specific molecules called ligands, once the ligands bind to receptors on the cell membrane. This is how peptide and amine derived hormones use to enter cells, as well as some viruses and bacteria
124
Exocytosis
Vesicles fuse with the membrane and eject their contents out of the cell. This is how the cell removes waste products and releases chemical signals that are received by other cells
125
In eukaryotic cells, what is the cell wall made of>
Cellulose in fungi and plants, agar, carrageenan and other materials in protists and algae, and chitin in fungi. Cell walls stabilize the structure of the cell and protect it from environmental stress
126
Extracellular matrix
A sticky secretion of carbohydrates and proteins in the space between adjacent cells. It helps to maintain shape and provide stability for cells without cell walls. The mass of the matrix is mostly formed by proteoglycans. Its strength is provided by fibrous proteins like collagen. Proteoglycans and collagen are attached to integrin proteins, which interact with transmembrane proteins in the plasma membrane. Some protein components form a basement membrane that ECM components adhere to.
127
What is the significance of the extracellular matrix?
It allows cells to withstand external stress and transmits signals from the outside of the cell to the inside. There is more ECM in connective tissue, and it gives different tissues distinct properties. Pathogens attach themselves to the host cell's extracellular matrix to establish infection
128
How are eukaryotic flagella different from prokaryotic flagella?
Eukaryotic flagella are more flexible and whip-like. They are composed of 9 parallel pairs of microtubules that surround a central pair of microtubules. The parallel microtubules use dynein motor proteins to bend the flagellum
129
Cilia
Unique to eukaryotes, shorter than flagella and cover the entire surface of the cell. They are structurally similar to flagella. A structure called a basal body is located at the base, which is composed of an array of triplet microtubules embedded in the plasma membrane. Cilia use a rapid, flexible waving motion, and they can sweep particles past or into cells
