Chapter 7 Inside the Cell Flashcards
Differential centrifugation
Procedure for separating cellular components according to their size and density by spinning a cell homogenate in a series of centrifuge runs. After each run, the supernatant is removed from the deposited material (pellet) and spun again at progressively higher speeds.
Why is differential centrifugation important?
Because it allowed researchers to isolate particular cell components and analyze their chemical composition
What is the difference between Differential centrifugation and electron microscopy?
Differential centrifugation splits cells into parts that are analyzed independently and electron microscopy gives a fixed “snapshot” of the cell or organism being observed.
These gate-like structures extend through both inner and outer nuclear membranes, they connect the inside of the nucleus with the cytosol
Nuclear Pore
true or false
Passage though the nuclear pore is selective
true
Most ribosomal RNAs are manufactured in the ______________ where they bind to proteins to form _________________, which are exported to the ______________.
nucleolus;ribosomes;cytoplasm
Explain the inbound and outbound traffic of the nuclear envelope.
messenger RNAs carry information required to manufacture protein out to the cytoplasm. Nucleoside triphosphates that act as building blocks for DNA & RNA enter the nucleus
Nuclear pore
An opening in the nuclear envelope that connects the inside of the nucleus with the cytoplasm and through which molecules such as mRNA and some proteins can pass.
A large complex of dozens of proteins lining a nuclear pore, defining its shape and transporting substances through the pore.
Nuclear Pore Complex
Virus
A tiny intracellular parasite that uses host cell enzymes to replicate; consists of a DNA or RNA genome enclosed within a protein shell (capsid). In enveloped viruses, the capsid is surrounded by a phospholipid bilayer derived from the host cell plasma membrane, whereas nonenveloped viruses lack this protective covering.
Nuclear localization signal (NLS)
A short amino acid sequence that marks a protein for delivery to the nucleus.
Name 3 cytoskeleton elements
1) Actin Filaments
2) Intermediate Filaments
3) Microtubules
In animal cells, _________________ is often the most abundant of all proteins.
actin
How does actin filament form?
when individual actin molecules polymerize
What is treadmilling?
the addition and deletion of actin subunits
Why does actin filaments tend to grow at the plus end?
because polymerization occurs fastest there
What is myosin?
a motor protein
What is the structure of actin filaments?
strands in a double helix with a + and - end
What are the subunits of actin filaments?
Actin
What are the functions of actin filaments?
1) maintain cell shape by resisting tension (pull)
2) move cells via muscle contraction or cell crawling
3) divide animal cells in two
4) move organelles and cytoplasm in plants, fungi, and animals
What happens when the “head” region of myosin protein interacts with ATP?
Myosin attaches to actin and it changes shape. The movement cause the actin filaments to slide.
___________ serve purely as a structural role in eukaryotic cells.
intermediate filaments
Tubulin dimers polymerize to form the large, hollow tube called a ___________.
microtubules
What is the structure of intermediate filaments?
Fibers wound into thick cables
What are the subunits of intermediate filaments?
keratin or vimentin or lamin
What are the functions of intermediate filaments?
1) maintain cell shape by resisting tension (pull)
2) anchor nucleus and some other organelles
What is the structure of microtubules?
a hollow tube
What are the subunits of microtubules?
a- and b- tubulin dimers
What are the functions of microtubules?
1) maintain cell shape by resisting compression (push)
2) move cells via flagella or cilia
3) move chromosomes during cell division
4) assist formation of cell plate during plant cell division
5) move organelles
6) provide tracks for intracellular transport
Actin Filament
A long fiber, about 7 nm in diameter, composed of two intertwined strands of polymerized actin protein; one of the three types of cytoskeletal fibers. Involved in cell movement. Also called a microfilament. Compare with intermediate filament and microtubule.
Name a class of proteins whose major function is to convert the chemical energy of ATP into motion. Includes dynein, kinesin, and myosin.
Motor protein
What is the division of the cytoplasm to form two daughter cells. Typically occurs immediately after division of the nucleus by mitosis or meiosis.
Cytokinesis
Cytoplasmic Streaming
The directed flow of cytosol and organelles that facilitates distribution of materials within some large plant and fungal cells. Occurs along actin filaments and is powered by myosin.
Cell Crawling
A form of cellular movement involving actin filaments in which the cell produces bulges (pseudopodia) that stick to the substrate and pull the cell forward. Also called amoeboid motion.
Intermediate Filaments
A long fiber, about 10 nm in diameter, composed of one of various proteins (e.g., keratins, lamins); one of the three types of cytoskeletal fibers. Form networks that help maintain cell shape and hold the nucleus in place. Compare with actin filament and microtubule.
Microtubules
A long, tubular fiber, about 25 nm in diameter, formed by polymerization of tubulin protein dimers; one of the three types of cytoskeletal fibers. Involved in cell movement and transport of materials within the cell. Compare with actin filament and intermediate filament.
Centrosome
Structure in animal and fungal cells, containing two centrioles, that serves as a microtubule-organizing center for the cell’s cytoskeleton and for the spindle apparatus during cell division.
Centrioles
One of two small cylindrical structures, structurally similar to a basal body, found together within the centrosome near the nucleus of a eukaryotic cell.
A _______________ is like a delivery truck that carries transport vesicles along microtubule tracks.
kinesin molecule
Any one of a class of motor proteins that use the chemical energy of ATP to transport vesicles, particles, or chromosomes along microtubules.
Kinesin
Bacterial flagella are mad of a protein called _______________; eukaryotic flagella mare constructed from _________________.
flagellin;microtubules(tubulin)
Bacterial flagella move the cell by ___________ and eukaryotic move the cell by________________.
rotating like a ships propeller; undulating (they whip back and forth)
Bacterial flagella are mad of a protein called _______________; eukaryotic flagella mare constructed from _________________.
flagellin;microtubules(tubulin)
Bacterial flagella move the cell by ___________ and eukaryotic move the cell by________________.
rotating like a ships propeller; undulating (they whip back and forth)