Chapter 6 - A Tour of the Cell Flashcards
1
Q
Light Microscope (LM)
A
- An optical instrument with lenses that refract (bend) visible light to magnify images of specimens
- Visible light is passed through a specimen and then through a glass lens
- Can magnify effectively to about 1,000 times the size of the actual specimen
- Various techniques enhance contrast and enable cell components to be stained or labeled
- Most subcellular structures, including organelles, are too small to be resolved by an LM
- Recent advances in light microscopy
- Confocal microscopy and deconvolution microscopy provide sharper images of three-dimensional tissues and cells
- New techniques for labeling cells improve resolution
2
Q
The three impotant parameters of microscopy are…
A
- Magnification: the ratio of an object’s image size to its real size
- Resolution: the measure of the clarity of the image, or the minimum distance of two distinguishable points
- Contrast: visible differences in parts of the sample
3
Q
Magnification
A
The ratio of an object’s image size to its real size
4
Q
Resolution
A
The measure of the clarity of the image, or the minimum distance of two distinguishable points
5
Q
Contrast
A
Visible differences in parts of a sample.
6
Q
Organelle
A
Any of several membrane-enclosed structures with specialized functions, suspended in the cytosol of eukaryotic cells.
7
Q
Electron Microscope (EM)
A
- A microscope that uses magnets to focus an electron beam on or through a specimen, resulting in a practical resolution of a hundredfold greater than that of a light microscope using standard techniques.
- Two basic types of EMs are used to study subcellular structures
- Scanning electron microscopes (SEMs)
- Transmission electron microscopes (TEMs)
8
Q
Transmission Electron Microscope (TEM)
A
- A type of electron microscope used to study the internal structure of thin sections of cells
- Focuses a beam of electrons through a specimen
9
Q
Scanning Electron Microscope (SEM)
A
- A type of electron microscope used to study the fine details of cell surfaces
- Focuses a beam of electrons onto the surface of a specimen, providing images that look 3-D
10
Q
Cell Fractionation
A
- The disruption of a cell and separation of its parts by centrifugation at successively higher speeds
- Enables scientists to determine the functions of organelles
11
Q
Centrifuge
A
- An instrument used in cell fractionation which spins test tubes holding mixtures of disrupted cells at a series of increasing speeds. At each speed, the resulting force causes a fraction of the cell components to settle to the bottom of the tube, forming a pellet. At lower speeds, the pellet consists of larger components, and at higher speeds smaller components.
12
Q
Cytology
A
- The study of cell structure
- Cytology and Biochemistry help correlate cell function with structure
13
Q
Biochemistry
A
- The study of the chemical processes (metabolism) of cells
- Biochemistry and Cytology help correlate cell function with structure
14
Q
The basic features of all eukaryotic cells and prokaryotic cells
A
- Plasma membrane
- Cytosol
- Chromosomes
- Ribosomes
15
Q
Cytosol
A
The semifluid portion of the cytoplasm.
16
Q
Cytoplasm
A
- The contents of the cell bounded by the plasma membrane
- In eukaryothes, the portion exclusive of the nucleus
17
Q
Chromosome
A
- A cellular structure carrying genetic material
- found in the nucleus of eukaryotic cells
- Each chromosome consists of one very long DNA molecule and associated proteins
- Found in the nucleoid region in bacterial cells
- A bacterial chromosome usually consists of a singular circular DNA molecule and associated proteins
18
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
19
Q
Nucleoid
A
A non-membrane-bounded region in a prokaryotic cell where the DNA is concentrated
20
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 the nucleus
21
Q
Plasma Membrane
A
- The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell’s chemical composition
- Allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell
- The general structure of a biological membrane is a double layer of phospholipids
- The boundary that separates the living cell from its surroundings
- Exhibits selective permeability, allowing some substances to cross it more easily than others
22
Q
As the surface area of a cell increases by a factor of n2, the bolume increases by a factor of…
A
- n3
- Metabolic requirements set upper limits on the size of cells, so the surface area to volume ratio of a cell is critical
- Small cells have a greater surface area relative to volume
23
Q
Parts of a eukaryotic cell present in animal cells but not in plant cells:
A
- Lysosomes
- Centrosomes, with centrioles
- Flagella (present in some plant sperm)
24
Q
Parts of an Animal Cell
A
25
Q
Parts of a plant cell:
A
26
Q
Parts of a eukaryotic cell present in plant cells but not in animal cells:
A
- Chloroplasts
- central vacuole
- Cell wall
- Plasmodesmata
27
Q
Nucleus
A
- Contains most of the cell’s genes and is usually the most conspicuous organelle
28
Q
Ribosome
A
- A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm
- Particles made of ribosomal RNA and protein
- consists of a large and a small subunit
- In eukaryotic cells, each subunit is assembled in the nucleolus
- Carry out protein synthesis in two locations
- In the cytosol (free ribosomes)
- On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)
29
Q
Nuclear envelope
A
- In a eukaryotic cell, the double membrane that surrounds the nucleus, perforated with pores that regulate traffic with the cytoplasm. The outer membrane is continuous with the endoplasmic reticulum.
- The nuclear membrane (the double membrane) consists of two lipid bilayers
30
Q
Nuclear Lamina
A
The shape of the nucleus is maintained by the nuclear lamina, which is composed of protein.
31
Q
Chromatin
A
- The complex of DNA and proteins that makes up eukaryotic chromosomes.
- When the cell is not dividing, chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope
- Chromatin condenses to form discrete chromosomes as a cell prepares to divide
32
Q
Nucleolus
A
- A specialized structure in the nucleus consisting of chromosomal regions containing ribosomal RNA (rRNA) genes along with ribosomal proteins imported from the cytoplasm
- The site of rRNA synthesis and ribosomal subunit assembly
33
Q
Components of the Endomembrane System:
A
- The collection of membranes inside and surrounding a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles
- Includes:
- Nuclear envelope
- Endoplasmic reticulum
- Golgi apparatus
- Lysosomes
- Vacuoles
- Plasma membrane
34
Q
Vesicle
A
A membranous sac in the cytoplasm of a eukaryotic cell.
- Transport vesicle: Carries molecules produced by the cell
35
Q
Endoplasmic Reticulum (ER)
A
- An extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions
- Accounts for more than half of the total membrane in many eukaryotic cells
36
Q
Smooth Endoplasmic Reticulum (Smooth ER)
A
- The portion of the endoplasmic reticulum that is free of ribosomes.
- Functions
- Synthesizes lipids
- Metabolizes carbohydrates
- Detoxifies drugs and poisons
- Stores calcium ions
37
Q
Rough Endoplasmic Reticulum (Rough ER)
A
- The portion of the endoplasmic reticulum with ribosomes attached
- Functions
- Has bound ribosomes which secrete glycoproteins
- Distributes transport vesicles
- Is a membrane factory for the cell
38
Q
Golgi Apparatus
A
- An organelle in eukaryotic cells consisting of stacks of flat membranous sacs called cisternae that modify, store, and route products of the endoplasmic reticulum and synthesize some products, notably noncellulose carbohydrates
- Functions
- Modifies products of the ER
- Manufactures certain macromolecules
- Sorts and packages materials into transport vesicles
40
Q
Phagocytosis
A
- A type of endocytosis in which large particulate substances or small organisms are taken up by a cell.
- It is carried out by some protists and by certain immune cells of animals
- In mammals, mainly microphages, neutrophils, and dendritic cells
- When a cell engulfs another cell it forms a food vacuole
41
Q
Autophagy
A
When lysosomes use enzymes to recycle the cell’s own organelles and micromolecules
45
Q
Central Vacuole
A
- In a mature plant cell, a large membranous sac with diverse roles in growth, storage, and sequestration of toxic substances
- Hold organic compounds and water
46
Q
Mitochondrion
A
- An organelle in nearly all eukaryotic cells that serves as the site of cellular respiration
- Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix
- Uses oxygen to break down organic molecules and synthesize ATP
- Enveloped by a double membrane
- The smooth outer membrane and inner membrane are folded into cristae, which presents a large surface area for enzymes that synthesize ATP
- The inner membrane creates two compartments: Intermembrane space and mitochondrial matrix
- Contain free ribosomes and circular DNA molecules
- Grow and reproduce somewhat independently in cells
47
Q
Chloroplast
A
- An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide to water
- Contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis
- Structure
- Thylakoids
- Stroma
- Enveloped by a double membrane
- Contain free ribosomes and circular DNA molecules
- Grow and reproduce somewhat independently in cells
48
Q
Peroxisome
A
- An organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen (O2), producing and then degrading hydrogen peroxide (H2O2).
- Produce hydrogen peroxide and convert it to water
- Specialized metabolic compartments counded by a single membrane
- Perform reactions with many different functions
- How peroxisomes are related to other organelles is still unknown.
50
Q
The Endosymbiont Theory
A
- An early ancestor of eukaryotic cells engulfed a nonphotosynthetic prokaryotic cell, which formed an endosymbiont relationship with its host
- The host cell and the 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
52
Q
Thylakoid
A
- A flattened, membranous sac inside a chloroplast.
- Often exist in stacks called grana that are interconnected
- Their membranes contain molecular “machinery” used to convert light energy into chemical energy
53
Q
Granum
A
- A stack of membrane-bounded thylakoids in the chloroplast.
- Function in the light reactions of photosynthesis
55
Q
Stroma
A
- The dense fluid within the chloroplast surrounding the thylakoid membrane and containing ribosomes and DNA
- Involved in the synthesis of organic molecules from carbon dioxide and water
56
Q
Cytoskeleton
A
- A network of microtubules, microfilaments, and intermediate filiments that extend throughout the cytoplasm and serve a variety of mechanical, transport, and signaling functions
- Organizes the cell’s structures and activities, anchoring many organelles
- Helps support hte cell and maintain its shape
- Interacts with motor proteins to produce motility
- Inside the cell, vesicles can travel along “monorails” provided by the cutoskeleton
- Recent evidence suggests that the cutoskeleton may help regulate biochemical activities
57
Q
Motor Protein
A
A protein that interacts with cytoskeletal elements and other cell components, producing ovement of the whole cell or parts of the cell.
58
Q
Microtubule (Tubulin Polymer)
A
- A hollow rod composed of tubulin proteins that makes up part of the cytoskeleton in all eukaryotic cells and is found in cilia and flagella.
- Wall consists of 13 columns of tubulin molecules
- The thickest component of the cytoskeleton
- Diameter: 25 nm with 15-nm lumen
- 200 nm to 25 microns long
- Main functions
- Maintenance of cell shape (compression-resisting “girders”)
- Cell motility (as in cilia or flagella)
- Chromosome movements in cell division
- Organelle Movements
59
Q
Microfilament (Actin Filament)
A
- A cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and acting alone or with myosin to cause cell contraction
- Structure: two intertwined strands of actin, each a polymer of actin subunits
- The thinnest component of the cytoskeleton
- Diameter: 7 nm
- Main functions:
- Maintenance of cell shape (tension-bearing elements)
- They form a 3-D netrork called the cortex just inside the plasma membrane to help support the cell’s shape
- Changes in cell shape
- muscle contraction
- cytoplasmic streaming
- cell motility (as in pseudopodia)
- Cells that do this contain the protein myosin in addition to actin
- cell division (cleavage furrow formation)
- Maintenance of cell shape (tension-bearing elements)
- Bundles of microfilaments make up the core of microvilli of intestinal cells
60
Q
Intermediate filament
A
- A component of the cytoskeleton that includes filaments intermediate in size between microtubules and microfilaments
- More permanent cytoskeleton fixtures than microtubules and microfilaments
- Structure: fibrous proteins supercoiled into thicker cables
- Diameter: 8-12 nm
- Protein subunits: One of several different proteins (such as keratins), depending on cell type
- Main functions
- Maintenance of cell shape (tension bearing elements)
- Anchorage of nucleus and certain other organelles
- Formation of nuclear lamina
61
Q
Centrosome
A
- A structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division
- A centrosome has two centrioles each with nine triplets of microtubules arranged in a ring
62
Q
Centriole
A
A structure in the centrosome of an animal cell composed of a cylinder of microtubule triplets arranged in a 9 + 0 pattern.
63
Q
Flagellum
A
- A long cellular appendage specialized for locomotion. Like motile cilia, eukaryotic flagella hace a core with nine outer doublet microtubules and two inner single microtubules (the “9 + 2” arrangement) ensheathed in an extension of the plasma membrane.
- Prokaryotic flagella have a different structure
- Moves like a snake
- Flagella and celia share a common structure
- 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 that bending movements of a cilium or flagellum
64
Q
Cilium
A
- A short appendage containing microtubules in eukaryotic cells.
- A motile cilium is specialized for locomotion or moving fluid past the cell
- It is formed from a core of nine outer doublet microtubules and two inner single microtubules (the “9 + 2” arrangement) ensheathed in an extension of the plasma membrane
- Moves like oars
- A primary cilium is usually nonmotile and plays a sensory and signaling role
- It lacks the two inner microtubules (the 9 + 0 arrangement)
- Celia and flagella share a common structure
- 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 that bending movements of a cilium or flagellum
65
Q
Basal Body
A
- A eukaryotic cell structure consisting of a “9 + 0” arrangement of microtubule triplits.
- May organize the microtubule assembly of a cilium or flagellum and is structurally very similar to a centriole
66
Q
Dynein
A
- In cilia and flagella, a large motor protein extending from one microtubule doublet to the adjacent doublet
- ATP hydrolysis drives changes in dynein shape that lead to bending of cilia and flagella
- how dynein moves flagella and celia
- dynein arms alternately grab, move, and release the outer microtubules
- Protein cross-links limit sliding
- Forces exerted by dynein arms causes doublets to curve, bending the cilium or flagellum
68
Q
How muscle cells work:
A
- In muscle cells, thousands of actin filaments are arranged parallel to one another. Thicker filaments composed of myosin interdigitate with the thinner actin fibers.
- Localized contraction brought about by actin and myosin also drives amoeboid movement
72
Q
Cell Wall
A
- A protective layer external to the plasma membrane in the cells of plants, prokaryotes, fungi, and some protists.
- Polysaccharides such as cellulose (in plants and some protists), chitin (in fungi), and peptidoglycan (in bacteria) are important structural components of cell walls.
- Plants
- The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water
- Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein
- Plant cell walls have multiple layers
- Primary cell wall
- Middle lamella
- Secondary cell wall (in some cells)
73
Q
Primary Cell Wall
A
In plants, a relatively thin and flexible layer that surrounds the plasma membrane of a young cell.
74
Q
Middle Lamella
A
In plants, a thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young cells.
75
Q
Secondary Cell Wall
A
In plant cells, a strong and durable matrix that is often deposited in several laminated layers around the plasma membrane and provides protection and support
76
Q
Plasmodesma
A
An open channel through the cell wall that connects the cytoplasm of adjacent plant cells, allowing water, small solutes, and some larger molecules (proteins and RNA) to pass between the cells.
77
Q
Extracellular Matrix (ECM)
A
- The meshwork surrounding animal cells, consisting of glycoproteins, polysaccharides, and proteoglycans synthesized and secreted by the cells
- ECM is made up of glycoproteins such as
- Collagen
- Proteoglycans
- fibronectin
- ECM proteins bind to receptor proteins in the plasma membrane called integrins
- Functions of the ECM
- Support
- Adhesion
- Movement
- Regulation
78
Q
Collagen
A
- A glycoprotein in the extracellular matrix of animal cells that forms strong fibers, found extensively in connective tissue and bone
- The most abundant protein in the animal kingdom
79
Q
Proteoglycan
A
- A large molecule consisting of a small core protein with many carbohydrate chains attached, found in the extracellular matrix of animal cells
- A proteoglycan may consist of up to 95% carbohydrate
80
Q
Fibronectin
A
An extracellular glycoprotein secreted by animal cells that helps them attach to the extracellular matrix
81
Q
Integrin
A
In animal cells, a transmembrane receptor protein with two subunits that interconnects the extracellular matrix and the cytoskeleton
82
Q
Intercellular Junctions
A
- Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact, and intercellular junctions facilitate this contact
- The types of intercellular Junctions
- Plasmodesmata
- Tight junctions
- Desmosomes
- Gap junctions
83
Q
Tight Junction
A
- A type of intercellular junction between animal cells that prevents the leakage of material through the space between cells
- Membranes of neighboring cells are pressed together
84
Q
Desmosome
A
- Anchoring junction
- A type of intercellular junction in animal cells that functions as a rivet, fastening cells together.
85
Q
Gap Junction
A
- Communicating junction
- A type of intercellular junction in animal cells, consisting of proteins surrounding a pore that allows the passage of materials between cells.
