Biology Chapter 6: A Tour of the Cell
Desmosomes are
(anchoring junctions) fasten cells together into strong sheets
Gap junctions are
(communicating junctions) provide cytoplasmic channels between adjacent cells
In terms of cellular function, what is the most important difference between prokaryotic and eukaryotic cells?
Eukaryotic cells are compartmentalized, which allows for specialization.
Which of the following is present in a prokaryotic cell?
Ribosomes
Which of the following groups is primarily involved in synthesizing molecules needed by the cell?
Ribosomes, rough endoplasmic reticulum, and smooth endoplasmic reticulum
Functions of microtubules
Shaping the cell Guiding movement of organelles Separating chromosomes during cell division
What is the functional connection between the nucleolus, nuclear pores, and the nuclear membrane?
Subunits of ribosomes are assembled in the nucleolus and pass through the nuclear membrane via the nuclear pores.
Cytoplasmic streaming is
a circular flow of cytoplasm within cells
The extracellular matrix of the animal cell has all of the following molecular components except __________.
a middle lamella
Dynein
a motor protein that drives the bending movement of cilium or flagellum
Pseudopodia are
cellular extensions
Extracellular components and connections between cells help ___________ _________ __________.
coordinate cellular activities
Microfilaments form a 3-D network called the _______.
cortex
Inside the cell, vesicles can travel along tracks provided by the ________.
cytoskeleton
Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through ________ _________ _________.
direct physical contact
Forces exerted by dynein arms cause
doublets to curve, bending the cilium or flagellum
Both cilia and flagella use a motor protein called _____.
dynein
microtubules bind with ________
dynein
Three types of cell junctions are common in _________ tissues.
epithelial
Intermediate filaments are ______ with diameters in a middle range.
fibers
ECM can regulate a cell's behavior by communication with a cell through______.
integrins
ECM proteins bind to
integrins
Thicker filaments composed of myosin ___________ with the thinner actin fibers
interdigitate
The network of fibers that organizes structures and activities in a cell __________.
is the cytoskeleton
Cortex is located...
just inside the plasma membrane and is used to help support the cell's shape
Intermediate filaments range in diameter from 8-12 nanometers, __________ than microfilaments but _________ than microtubules.
larger smaller
Protein cross-links
limit sliding
Plant cell walls are made
of cellulose fibers embedded in other polysaccharides and protein
Cells are small because __________.
of the geometric relationship between surface and volume
Cytoskeleton
organizes the cell's structures and activities anchoring many organelles
In muscle cells, thousands of actin filaments are arranged _______ to one another.
parallel
In _____ _____, actin-myosin interactions and sol-gel transformations drive cytoplasmic streaming.
plant cells
water in plants move through ___________________.
plasmodesmata
The four types of cell junctions are:
plasmodesmata tight junctions desmosomes gap junctions
The cell wall
protects the plant cell, maintains its shape, and prevents excessive uptake of water
Cells crawl along a surface by extending ____________ and moving toward them
pseudopodia
Integrins are
receptor proteins in the plasma membrane that the ECM proteins bind to.
The function of the rough endoplasmic reticulum (RER) is __________.
to synthesize proteins that are secreted as glycoproteins
Through plasmodesmata,
water and small solutes (and sometimes proteins and RNA) can pass from cell to cell
Cilia and flagella share a common structure:
1) A core of microtubules sheathed by the plasma membrane 2) A basal body that anchors the cilium or flagellum 3) A motor protein called dynein, which drives the bending movements of a cilium or flagellum
___________ ________ are more permanent cytoskeleton fixtures than the other two classes.
Intermediate filaments
Plant cell walls may have multiple layers:
Primary cell wall Middle lamella Secondary cell wall
Middle lamella is
a thin layer between primary walls of adjacent cells
Prokaryotes, fungi, and some unicellular eukaryotes also have _____ _____
cell walls
Bundles of microfilaments make up
the core of microvilli of intestinal cells
Microtubules are the _________ of the three components of the cytoskeleton
thickest
Cytoskeleton is composed of
three types of molecular structures
There are three types of cell junctions in animal cellls
tight junctions desmosomes gap junctions
The cytoskeleton helps
to support the cell and maintain its shape
Both cilia and flagella posses
1) A core of microtubules sheathed by the plasma membrane
Microfilaments are
solid rods about 7 nm in diameter, built as a twisted double chain of actin subunits
Cytoplasmic streaming also
speeds up the distribution of materials within the cell.
Most cells __________ and ________ materials that are external to the plasma membrane.
synthesize secrete
Your intestine is lined with individual cells. No fluids leak between these cells from the gut into your body. Why?
The intestinal cells are bound together by tight junctions.
The cytoskeleton is
a network of fibers that organizes structures and activities in the cell
Microfilaments are also called______ filaments which are the ________ components
actin thinnest
Secondary cell wall (in some cells) is
added between the plasma membrane and the primary cell wall
Localized contraction brought about by actin and myosin also drives _________ ____________.
amoeboid movement
The cell wall is
an extracellular structure that distinguishes plant cells from animal cells
Both cilia and flagella have a ______ _______ that anchors the cilium or flagellum
basal body
The structural role of microfilaments is to _______ _________, resisting pulling forces within the cell
bear tension
The main difference between cilia and flagella differs in their __________ ________.
beating patterns
Intermediate filaments support
cell shape and fix organelles in place
Animal cells lack _____ _____ but are covered by an elaborate _____________ _________ (_ _ _)
cell walls extracellular matrix (ECM)
Fact::
cells by secretion have the ability to change their surroundings
In animal cells, the centrosome has a pair of _________, each with nine triplets of microtubules arranged in a ring
centrioles
In animal cells, microtubules grow out from a __________ near the nucleus
centrosome
Plasmodesmata are
channels between adjacent plant cells
Plasmodesmata are
channels that perforate plant cell walls
Mechanical signaling may occur through cytoskeletal changes, that trigger _________ _______ in the cell.
chemical signals
Microtubules control the beating of ______ and _____.
flagella cilia
The ECM around a cell can influence the activity of _____ in the nucleus.
gene
The ECM is made up of
glycoproteins such as collagen, proteoglycans, and fibronectin
Dynein arms alternately _____, _____, and _______ the outer microtubules
grab move release
Microtubules are _______ rods about 25nm in diameter and about 200nm to 25 microns long
hollow
Observing a fluorescent micrograph cell with intermediate filaments would help you identify the cell as a __________.
human skin cell
Microfilaments function in cell motility including __________.
muscle contraction, amoeboid movement, and cytoplasmic streaming in plants
Microfilaments that function in cellular motility contain the protein ________ in addition to actin
myosin
microfilaments bind with ________
myosin
cytoskeleton is a
network of fibers extending throughout the cytoplasm
The region of a bacterial cell that contains the genetic material is called the __________.
nucleiod
Plasmodesmata is the only type of cell junction in ______ ___.
plant cells
Dye injected into a plant cell might be able to enter an adjacent cell through __________.
plasmodesmata
Primary cell wall is
relatively thin and flexible
Microfilaments are built as a twisted double chain of ______ subunits
actin
A protein that ultimately functions in the plasma membrane of a cell is most likely to have been synthesized __________.
in the rough endoplasmic reticulum
The walls of plant cells are largely composed of polysaccharides and proteins that are synthesized __________.
in the rough endoplasmic reticulum and in the Golgi apparatus
At tight junctions
membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid
flagella and cilia are
microtubule-containing extensions that project from some cells
motors go through ____________.
microtubules
The three type of molecular structures that compose the cytoskeleton are
microtubules microfilaments intermediate filaments
Fact:
microtubules and microfilaments are polar and have directional movement
The cytoskeleton interacts with ______ ______ to produce motility
motor proteins
