CHAPTER 7 A TOUR OF THE CELL
Chapter 6 ( A Tour of the Cell
Student Guided Notes
Overview: The Fundamental Units of Life
• The cell is the simplest collection of matter that can be alive.
• Cells are an organism’s basic units of ___________________________.
• Evolution is the unifying biological theme.
Concept 6.1 Biologists use microscopes and the tools of biochemistry to study cells
• In a light microscope (LM), ___________________________________________________________ __________________________________________________________________________________.
○ Magnification is __________________________________________________________________.
○ Resolution is a measure of image clarity, _______________________________________________
________________________________________________________________________________.
• An electron microscope (EM) _________________________________________________________ ___________________________________________________________________________________.
• Scanning electron microscopes (SEMs) are useful for studying _______________________________ ___________________________________________________________________________________.
• Transmission electron microscopes (TEMs) are used to study ________________________________
___________________________________________________________________________________
• Although EMs reveal organelles that are impossible to resolve with LMs, the methods used to prepare cells for viewing under an EM kills them.
• Cytology combined with biochemistry, ___________________________________________________ ___________________________________________________________produced modern cell biology.
Cell biologists can isolate organelles to study their functions.
• Cell structure and function can by studied by cell fractionation, a technique _________________
______________________________________________________________________________.
○ A centrifuge spins test tubes holding mixtures of disrupted cells.
○ The resulting forces cause a fraction of the cell components to settle to the bottom of the tube, forming a pellet.
Concept 6.2 Eukaryotic cells have internal membranes that compartmentalize their functions
Prokaryotic and eukaryotic cells differ in size and complexity.
• All cells are surrounded by a ______________________________.
• The semifluid substance within the membrane is the cytosol.
• All cells contain chromosomes and all cells have ribosomes.
○ In a eukaryotic cell, most of the DNA is in the _______________________________________.
○ In a prokaryotic cell, the DNA is concentrated in the __________________________________.
• The interior of a prokaryotic cell and the region between the _________________________ and the _____________________________________ of a eukaryotic cell is the cytoplasm.
• The logistics of carrying out cellular metabolism set limits on cell size.
• The plasma membrane functions as a __________________________________________________
__________________________________________________________________________________ __________________________________________________________________________________.
• As a cell increases in size, its volume increases faster than its_________________________________.
Internal membranes compartmentalize the functions of a eukaryotic cell.
• A eukaryotic cell has extensive and elaborate internal membranes, which partition the cell.
○ These membranes also participate directly in metabolism.
• Each type of membrane has a unique combination of lipids and proteins for its specific functions.
Concept 6.3 The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes
• The nucleus contains ______________________________________________________________.
• The nucleus is separated from the cytoplasm by a double membrane called the ____________________ ______________________________ .
○ The envelope is perforated by pores.
The nuclear side of the envelope is lined by the nuclear lamina, _____________________________ __________________________________________________________________________________.
• The DNA and associated proteins are organized into _______________________________________.
○ Each chromosome contains _________________________________________________________
_______________________________________________________________________________.
• Each eukaryotic species has a characteristic number of chromosomes.
○ A typical human cell has ________ chromosomes.
• In the nucleus is ____________________________________________________________________.
• In the nucleolus, ribosomal RNA (rRNA) is synthesized and assembled with proteins to form ribosomal subunits.
• The nucleus directs protein synthesis by _________________________________________________.
Ribosomes are protein factories.
• Ribosomes, containing rRNA and protein carry out ________________________________________.
• Free ribosomes _____________________________________________________________________.
Bound ribosomes are attached to the ___________________________________ or __________________________________.
○ Bound ribosomes synthesize proteins that are ___________________________________________
_______________________________________________________________________________.
Concept 6.4 The endomembrane system regulates protein traffic and performs metabolic functions in the cell
Many of the internal membranes are part of the endomembrane system, which includes ___________
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
• The tasks include _____________________________________________________________________
___________________________________________________________________________________ __________________________________________________________________________________.
• These membranes are either directly continuous or connected via ______________________________.
The endoplasmic reticulum manufactures membranes and performs many other biosynthetic functions.
• The endoplasmic reticulum (ER) includes a network of membranous tubules and sacs called _____________________________________ that separate the __________________________ ___________________________________.
• There are two regions of ER.
○ Smooth ER looks smooth because ____________________________________________________.
○ Rough ER looks rough because ______________________________________________________.
• Smooth ER is rich in enzymes and plays a role in a variety of metabolic processes, including
____________________________________________________________________________________
___________________________________________________________________________________.
• In the smooth ER of the liver, enzymes help _______________________________________________
___________________________________________________________________________________.
• Rough ER is especially abundant in cells that ______________________________________________.
• Most secretory polypeptides are glycoproteins.
• Secretory proteins are packaged in ____________________________________________.
• Rough ER is also a ____________________________________ factory for the cell.
The Golgi apparatus is the shipping and receiving center for cell products.
• Many transport vesicles from the ER travel to the Golgi apparatus for modification of their contents.
• The Golgi apparatus is a center of ______________________________________________________ _________________________________________________________________________________.
• The Golgi apparatus consists of flattened membranous sacs—cisternae—that look like a stack of pita bread.
• One side of the Golgi apparatus, the cis face, ___________________________________________.
• Golgi products that will be secreted depart from the _______________________________________.
○ Transport vesicles from the Golgi may have external molecules that recognize “docking sites” on the surface of specific organelles or on the plasma membrane.
Lysosomes are digestive compartments.
• A lysosome is ______________________________________________________________________
__________________________________________________________________.
○ Some lysosomes arise by __________________________________________________________ _______________________________________________________________________________.
• Lysosomes carry out intracellular digestion in a variety of circumstances.
○ Amoebas eat by _________________________________________________________________.
○ Human macrophages help defend the body by ___________________________________________
__________________________________________________________.
• Lysosomes can play a role in _________________________________________________________ ______________________________________________. This recycling, or ___________________________________, renews the cell.
• In people who have Tay-Sachs disease, a _________________________________________________ is missing or inactive, and the brain becomes impaired by ____________________________________ __________________________________________________________________________________.
Vacuoles have diverse functions in cell maintenance.
• Food vacuoles are formed by ____________________________________________ and fuse with _______________________________.
• Contractile vacuoles, found in freshwater protists, __________________________________________.
• In plants and fungi, vacuoles carry out enzymatic hydrolysis, like animal lysosomes do.
• A large central vacuole is found in ______________________________________________________.
○ The vacuolar membrane is selective in its transport of solutes into the central vacuole.
• The functions of the central vacuole include ________________________________________________
____________________________________________________________________________________
___________________________________________________________________________________.
Concept 6.5 Mitochondria and chloroplasts change energy from one form to another
• Mitochondria are the sites of __________________________________________________________
___________________________________________________________________________________.
Chloroplasts, found in plants and algae, are the sites of _____________________________________
___________________________________________________________________________________.
Mitochondria and chloroplasts have a similar evolutionary origin.
• The endosymbiont theory states that ____________________________________________________
___________________________________________________________________________________
• There is considerable evidence to support the endosymbiont theory for the origin of mitochondria and chloroplasts.
○ Each mitochondrion or chloroplast has two membranes.
○ Mitochondria and chloroplasts contain ribosomes and __________________________________.
○ Mitochondria and chloroplasts grow and reproduce as ____________________________________.
Mitochondria convert chemical energy within eukaryotic cells.
• Almost all eukaryotic cells have mitochondria.
○ The number of mitochondria is correlated with __________________________________________.
○ Mitochondria have a smooth outer membrane and a convoluted inner membrane with infoldings called ___________________________.
○ The inner membrane encloses the _____________________________________________________ __________________________________________________________________.
Chloroplasts capture light energy and convert it to chemical energy.
• Chloroplasts contain the green pigment ___________________________________.
• Inside the innermost membrane is a fluid-filled space, the stroma, in which float __________________
___________________________________________________________________________________.
○ In some regions, thylakoids are stacked like ____________________________________________.
• The chloroplast belongs to a family of plant structures called plastids.
○ Amyloplasts are __________________________________________________________________.
○ Chromoplasts ____________________________________________________________________.
The peroxisome is an oxidative organelle.
• Peroxisomes contain enzymes that transfer ________________________________________________
_______________________________, producing __________________________________________ as a byproduct.
• Some peroxisomes use oxygen to ________________________________________________________.
• The H2O2 formed is toxic, but peroxisomes contain _________________________________________ ___________________________________________________________________________________.
Concept 6.6 The cytoskeleton is a network of fibers that organizes structures and activities in the cell
The cytoskeleton provides support, motility, and regulation.
• The cytoskeleton is _________________________________________________________________
_________________________________________________________________________________ ________________________________________________________________________________.
• The cytoskeleton provides anchorage for many organelles and enzymes.
• The cytoskeleton also plays a major role in cell motility.
○ ________________________________ bring about movements of cilia and flagella.
Three main types of fibers make up the cytoskeleton: ________________________________________, ____________________________________, and ____________________________________________.
• Microtubules are the thickest of the three types of fibers; microfilaments (or ___________________ filaments) are the thinnest; and intermediate filaments are fibers with diameters in a middle range.
• Microtubules are ___________________________________________________________________.
• Microtubules shape and support the cell and serve as tracks to guide motor proteins.
• In many animal cells, microtubules grow out from a _________________________near the nucleus.
• Within the centrosome is a pair of centrioles, each with ____________________________________
_________________________________________________________________________________.
• Although centrosomes with centrioles may help organize microtubule assembly in animal cells, they are not essential for this function.
• A specialized arrangement of microtubules is responsible for the beating of _____________________ and ____________________________________.
○ The sperm of ____________________________, _____________________________ , and some _______________________have flagella.
○ Cilia lining the trachea _____________________________________________________________ ________________________________________________________________________________.
• Cilia usually occur in large numbers on the cell surface and there are usually just one or a few flagella per cell.
• The cilium or flagellum is anchored in the cell by a ________________________________________, __________________________________________________________________________________.
• Each outer doublet also has pairs of ___________________________________________________ that are responsible for the bending movements.
• Microfilaments or ________________________________ are _______________________________.
• The structural role of microfilaments in the cytoskeleton is to ________________________________.
• Microfilaments are important in cell motility, especially in ______________________________ cells.
○ In muscle cells, thousands of actin filaments are arranged parallel to one another; actin and myosin work together for muscle contraction.
• In plant cells, actin-myosin interactions drive cytoplasmic streaming, which creates_______________
__________________________________________________________________________________.
• Intermediate filaments are larger than microfilaments but smaller than microtubules, built from
__________________________________________________________________________________ __________________________________________________________________________________.
• __________________________________________ are more permanent fixtures of the cytoskeleton.
Concept 6.7 Extracellular components and connections between cells help coordinate cellular activities
Plant cells are encased by cell walls.
• In plants, the cell wall ________________________________________________________________
___________________________________________________________________________________ ___________________________________________________________________________________.
• The basic design of cell walls consists of ______________________________.
• A young plant cell secretes a relatively thin and flexible wall called the __________________________.
• Between the primary walls of adjacent cells is a middle lamella, a thin layer with sticky polysaccharides called __________________________________ that _______________________________________.
• When a plant cell stops growing, it ____________________________________________________or by adding a secondary cell wall.
○ __________________________ consists mainly of secondary walls.
The extracellular matrix of animal cells provides support, adhesion, movement, and regulation.
• Though lacking cell walls, animal cells do have an elaborate extracellular matrix (ECM).
• The primary constituents of the ECM are _______________________________________________
_________________________________________________________________________________
• In many cells, fibronectins in the ECM connect to ________________________________, ________ ___________________________________________________________________________________
___________________________________________________________________________________.
• The ECM can regulate cell behavior.
○ The ECM can influence the activity of genes.
Intercellular junctions help integrate cells into higher levels of structure and function.
• Plant cells are perforated with plasmodesmata, ____________________________________________
___________________________________________________________________________________.
• Animals have three main types of intercellular links.
• In tight junctions, _____________________________________________________________
_____________________________________________________________________________.
• Desmosomes (or anchoring junctions) ______________________________________________.
• Gap junctions (or communicating junctions)_________________________________________
_____________________________________________________________________________.
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