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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