Chapter 7 - Inside the Cell
signal recognition particle
*Step 2* The signal sequence binds to a _________ _______ _________ (SRP) - a complex of RNA and protein. The attached SRP causes protein synthesis to stop.
rough ER, SRP
*Step 3* The ribosome + signal sequence + SRP complex moves to the _______ _____ membrane, where it attaches to the ______ receptor. -Think of the SRP as a key that is activated by an ER signal sequence. The SRP receptor in the ER membrane is the lock
SRP, translocon
*Step 4* Once the lock (the receptor) and key (the SRP) connect, the ______ is released and protein synthesis continues through a channel called the ___________.
ER signal sequence
*Step 5* The growing protein is fed into the ER lumen, and the ____ ________ ________ is removed.
Golgi apparatus, trans
1.Proteins bound for different destinations carry distinct tags that serve as molecular zip codes. 2 Proteins are sorted in the _______ ________ when they bind to different receptors. 3. Transport vesicles bud off the ________ face of the Golgi apparatus and travel to their destinations. 4. Cytosolic and membrane proteins cause transport vesicles to attach and fuse at destinations.
fimbria, attachment
A _________ is a needlelike projection that extends from the plasma membrane of some bacteria and promotes ___________ to other cells or surfaces. -These structures tend to be more numerous than flagella and may be all over the cell.
flagellum
A prokaryotic ___________ is assembled from many different proteins at the cell surface of certain species. The feature that is common to both archaeal and bacterial flagella is a molecular motor embedded in the plasma membrane. -The proteins that comprise these motors and filaments differ between the two groups, but their functions are the same - to rotate a long rigid filament to propel the cell through water. -At top speed, flagellar movement can drive a bacterial cell through water at 60 cell lengths per second.
phagocytosis
A second pathway that involves recycling material brought in from the outside of the cell is called _______________.
plus
After repeated rounds of this contraction cycle, the myosin progressively moves toward the _________ end of the actin filament. -This type of movement resembles the arms of a sailor hauling in a rope.
cytoskeleton
All bacterial species, for example, contain protein fibers that are essential for cell division. Some species also have protein filaments that help maintain cell shape. -Protein filaments such as these form the basis of the __________.
reduction-oxidation reactions
Although different types of cells from the same individual may have distinct types of peroxisomes, these organelles all share a common function: Peroxisomes are centers for ________-__________ ___________.
centrosome
Although plant cells typically have hundreds of sites where microtubules start growing, most animal and fungal cells have just one site that is near the nucleus, called the ____________.
storage
Although some vacuoles contain hydrolases and play a similar role to the lysosome of animal cells, most of the vacuoles in plant and fungal cells act as ___________ depots.
carbohydrate
Although the composition of the eukaryotic cell wall varies among species and even among types of cells in the same individual, the general plan is similar: -Rods or fibers composed of a __________ run through a stiff matrix made of other polysaccharides and proteins.
ribosomes
Among the genes present in mitochondrial DNA are those that encode RNAs for mitochondrial ________. -These (________) are smaller than those found in the cytosol, yet they still function to produce some of the mitochondrial proteins. (most proteins found in mitochondria are produced from ribosomes in the cytosol)
organelle
An __________ is a membrane-bound compartment inside the cell that contains enzymes or structures specialized for a particular function.
lysosomes
Animal cells contain organelles called ___________ that function as recycling centers
centrioles
Animal centrosomes contain two bundles of microtubules called ____________. -Although additional microtubues emanate from these centrosomes in animals, they do not grow directly from the centrioles.
late endosome
As proton pumps continue to lower the early endosome's pH, it undergoes a series of processing steps that cause it to mature into a _________ _________.
lumen
As the proteins are being manufactured, they move to the interior of the sac-like component of the rough ER. -The interior of the rough ER, like the interior of any sac-like structure in a cell or body, is called the ___________.
cell wall
Because the cytoplasm contains a high concentration of solutes, it is hypertonic relative to the surrounding environment in most habitats. -Under these conditions, water enters the cell via osmosis and makes the cell's volume expand. -In most bacteria and archaea, this pressure is resisted by a stiff _______ ______.
macromolecular
Biologists often refer to ribosomes, along with other multicomponent complexes that perform specialized tasks, as "_________ machines"
cell division
Both mitochondria and chloroplasts also grow and divide independently of ______ _______.
Bacteria, Archaea, Eukarya
But according to *phylogeny*, or evolutionary history, organisms are divided into three broad domains called: 1. __________ 2. __________ 3. __________
autophagy
Cells are also involved in recycling large structures and organelles that exist within the cytoplasm through a process called ____________. -During autophagy, portions of the cytoplasm, including damaged organelles marked for destruction, are enclosed within an internal membrane to form an autophagosome. Like the phagosome, this vesicle is also delivered to a lysosome.
eukaryotes, prokaryotes
Cells are divided into two fundamental types: __________ and ___________.
separated, efficient, localized
Compartmentalization also offers two key advantages: 1. Incompatible chemical reactions can be ___________. For example, new fatty acids can be synthesized in one organelle while excess or damaged fatty acids are degraded and recycled in a different organelle. 2. Chemical reactions become more __________. First, the substrates required for particular reactions can be __________ and maintained at high concentrations within organelles. -When substrates are used up in a particular part of the organelle, they can be replaced by substrates that have only a short distance to diffuse. -Second, groups of enzymes that work together can be clustered within or on the membranes of organelles instead of floating free in the cytosol. When the product of one reaction is the substrate for a second reaction, clustering the two enzymes increases the speed and efficiency of both reactions.
synthesize, poisonous
Depending on the type of cell, these enzymes may ____________ lipids needed by the organism or break down lipids and other molecules that are ____________.
two
Each mitochondrion has ________ membranes.
mitochondrial DNA
Each mitochondrion has many copies of a small, circular or, in some species, linear chromosome called _____________ _________ that is independent of the nuclear chromosomes.
larger
Eukaryotic cells are much _________ on average than bacteria and archaea.
endoplasmic reticulum
Eukaryotic ribosomes are not only scattered free in the cytosol, but are also associated with an organelle called the _______ _________.
endomembrane system
Even though lysosomes are physically separated from the Golgi apparatus and the endoplasmic reticulum, these various organelles jointly form a key functional grouping referred to as the _________ ___________.
smooth ER
For example, the _______ _____ is the manufacturing site for phospholipids used in membranes.
pulse-chase
George Palade and colleagues did pioneering research on the secretory pathway using a _______-_______ experiment to track protein movement.
organelles
How are the problems associated with a low surface-area-to-volume-ratio overcome in eukaryotic cells? -The answer lies in their numberous ________.
vesicles, cis
How do proteins get from the ER to the Golgi apparatus? -proteins are transported in _______ that bud off from the ER, move away, fuse with the membrane on the _____ face of the Golgi apparatus, and dump their cargo inside.
movement
In addition to providing structural support, actin filaments are involved in _________.
plasmids
In addition to their chromosomes, prokaryotic cells may contain from one to about a hundred small, usually circular, supercoiled DNA molecules called __________.
cell crawling
In addition, the movement called ______ _______ occurs when groups of actin filaments grow, creating bulges in the plasma membrane that extend and move the cell. (Amoebae, slime molds)
calcium
In addition, the smooth ER functions a reservoir for ___________ ions that can be released to trigger a wide array of activities inside the cell.
actin
In animal cells, _________ is often the most abundant of all proteins - typically it represents 5-10% of the total protein in teh cell.
plasma membrane
In animal cells, actin filaments are particularly abundant just under the ________ _______. They are organized into long, parallel bundles or dense, crisscrossing networks in which actin filaments are linked to one another by other proteins. -Help stiffen the cell and define its shape
peroxisome
In animals and plants, the products of these (red-ox) reactions often include hydrogen peroxide (H2O2), which is highly reactive. If hydrogen peroxide escaped from the __________, it would quickly react with and damage DNA, proteins, and cellular membranes.
cytosol
In effect, the huge volume inside a eukaryotic cell is compartmentalized into small binds. -Because eukaryotic cells are subdivided, the __________ - the fluid portion between the plasma membrane and these organelles - is only a fraction of the total cell volume.
smooth ER
In electron micrographs, parts of the ER that are free of ribosomes appear smooth and even. -Appropriately, these parts of the ER are called the ____________ ________.
nucleus
In eukaryotes, the cytoplasm consists of everything inside the plasma membrane excluding the ________.
required, adapt
In many cases the genes carried by plasmids are not _________ under normal conditions; instead, they help cells ________ to unusual circumstances, such as the sudden presence of a poison in the environment.
Golgi apparatus
In most cases the proteins that leave the rough ER must first pass through the _______ _______ before they reach their final destination.
cisternae
In most eukaryotes, the Golgi apparatus consists of dozens of stacks of discrete flattened, membranous sacs called ____________, which are stacked on top of each other like pancakes.
phagosome
In phagocytosis, the plasma membrane of a cell surrounds a smaller cell or food particle and engulfs it, forming a structure called a _______. This structure is delivered to a lysosome, where it is taken in and digested.
myosin
In several cases, actin's role in movement depends on the protein ___________.
folding
In the lumen of the rough ER, newly manufactured proteins undergo _________ and other types of processing.
cytoplasm
Inside the plasma membrane, all the contents of a cell (except the nucleus in Euk's) are collectively termed the __________.
thylakoids
Instead, a third membrane forms an independent network of hundreds of flattened, sac-like structures called ____________ throughout the interior.
chromosome, ribosomes
Like mitochondria, each chloroplast contains copies of its own circular __________ and small __________ that manufacture some, but not all, of the organelle's proteins.
double membrane
Like the mitochondrion, the chloroplast is surrounded by a _________ ________.
prokaryotic
Members of the Bacteria and Archaea are __________; members of the Eukarya - including algae, fungi, plants, and animals - are eukaryotic.
microtubule-organizing center
Microtubules originate from a structure called the ______-______ ______ (MTOC) -Their plus ends grow outward, radiating throughout the cell.
cristae
Mitochondrion -The outer membrane defines the organelle's surface, while the inner membrane forms a series of sac-like ___________.
messenger RNA
Molecules called ________ _______s carry the information required to manufacture proteins.
chloroplast
Most algal and plant cells possess an organelle called the _____________, in which sunlight is converted to chemical energy during photosynthesis.
DNA, proteins
Most bacterial and archaeal species have a single, circular chromosome that consists of a large _______ molecules associated with _______.
inner,
Most of the enzymes and molecular machines responsible for synthesizing ATP are embedded in the ______ membrane or suspended in the matrix. Depending on the type of cell, the number of mitochondria can range from one to over a million.
grana
Most thylakoids are arranged in interconnected stacks called ________.
mitochondrial matrix
Motochondria -The solution enclosed within the inner membrane is called the ___________ ___________.
motor protein
Myosin is a _______ _______: a protein that converts the chemical energy in ATP into the kinetic energy of mechanical work.
RNA , ribosomes, subunits
Nucleolus -Where the _______ molecules found in ___________ are manufactured and the large and small ribosomal ________are assembled.
nuclear envelope
Nucleus -Among the largest and most highly organized of all organelles, it is enclosed by a unique structure - a complex double membrane called the ________ ________.
early endosome
Once receptor binding occurs, the plasma membrane folds in and pinches off to form an endocytic vesicle. These vesicles then drop off their cargo in an organelle called the ________ __________. -the activity of proton pumps in the membrane of this organelle acidifies its lumen, which causes the cargo to be released from their receptors. -Many of these emptied cargo receptors are then repackaged into vesicles and returned to the plasma membrane.
receptor-mediated
One pathway originating at the plasma membrane is called _______-_______ endocytosis. -As its name implies, the sequence of events begins when particles outside the cell bind to receptors on the plasma membrane.
chromosome
Plasmids contain genes but are physicallly independent of the cellular __________.
endoplasmic reticulum
Portions of the nuclear envelope extend into the cytoplasm to form an extensive membrane-enclosed factory called the _________ __________.
nuclear localization signal
Pretty much all proteins that can go in the nucleus need a specific sequence of amino acids. -This sequence came to be called the _________ __________ __________ (NLS)
membranes, organelles
Ribosomes are *not* surrounded by ____________, so they are not classified as ______________.
protein
Ribosomes are observed in all prokaryotic cells and are found throughout the cell interior. It is not unusual for single cell to contain 10,000 of them, each functioning as a ________-manufacturing center.
genes
Segments of DNA that contain information for building functional RNAs, some of which may be used to make polypeptides, are called ________.
ribosomal RNA
Several types of RNA molecules are produced, each distinguished by size and function. -For example, ________ ______s are manufactured in the nucleolus, where they bind to proteins to form ribosomes.
exocytosis
Some transport vesicles go to the plasma membrane, where they will secrete its contents to the outside. -This process is called _________.
actin filaments
Sometimes called microfilaments because they are the cytoskeletal element with the smallest diameter, _________ ________ are fibrous structures made of the globular protein actin.
vesicles, cargo
The /cis/ side of a Golgi apparatus receives the _________ containing rough ER products, referred to as ________.
nuclear envelope
The ER membrane is continuous with the _________ __________.
plasma membrane
The ________ ________ consists of a phospholipid bilayer and proteins that either span the bilayer or attach to one side.
trans
The _________ side of the Golgi apparatus ships the cargo out to other organelles or the cell surface.
cytoskeleton, protein
The ___________: -This extensive system of ________ fibers gives the cell its shape and structural stability. -It is also involved in moving the materials withing the cell as well as the cell itself.
vacuole
The cells of plants, fungi, and certain other groups lack lysosomes. Instead, they contain a prominent organelle called a ________. -Compared with the lysosomes of animal cells, the (____)'s of plant and fungal cells are large - in plants, sometimes taking up as much as 80% of the cell's volume.
edges, interior
The chromosomes are arranged in the nucleus with densely packed sections concentrated at the _______ and loosely packed sections toward the ________.
transported
The common theme is that many of the rough ER pruducts are packaged into vesicles and ___________ to various distant destinations - often to the surface of the cell or beyond.
acid hydrolases
The digestive enzymes inside lysosomes are collectively called ________ ____________ because under acidic conditions, they use water to break monomers from macromolecules.
membrane
The genetic material in the nucleoid is often organized by clustering loops of DNA into distinct domains, but it is *not* separated from the rest of the cell interior by a __________.
acid hydrolases
The late endosome is the pre-lysosomal compartment introduced earlier, where the _________ _________ from the Golgi apparatus are dropped off.
nuclear
The mitochondrial DNA contains only a tiny fraction of the genes responsible for the function of the organelle - the other genes reside in the ______ DNA.
keratins
The most familiar intermediate filaments belong to a family of molecules called the ____________. -The cells of your skin and line surfaces inside your body have about 20 types of keratin. -Some cells can secrete forms of keratin - hair fingernails, toenails, etc.
chromosome
The most prominent structure inside a prokaryotic cell is the ____________, although it is often difficult to visualize by electron microscopy.
nuclear lamina
The nuclear envelope is studded with pore-like openings, and the inside surface is linked to fibrous proteins that form a lattice-like sheet called a ________ __________.
shape
The nuclear lamina stiffens the membrane and maintains organelle ________.
nucleolus
The nucleus also contains specific sites where gene products are processed and includes at least one distinctive region called the _____________, where the RNA molecules found in ribosomes are manufactured and the large and small ribosomal subunits are assembled.
storage, processing
The nucleus contains the chromosomes and functions as an administrative center for information _______ and ___________.
mitochondrion
The organelle primarily responsible for supplying ATP in animals, plants, and virtually all other eukaryotic cells is the _______________.
plasma membrane
The photosynthetic membranes observed in bacteria develop as infoldings of the _____ _____ and contain the enzymes and pigment molecules required for these reactions to occur.
stroma
The region between thylakoids and the inner membrane, called the ________, contains enzymes that use this chemical energy to produce sugars.
nucleoid
The region of the cell where the circular chromosome is located is called the ___________.
ER, shipped
The ribosomes associated with the rough ER synthesize proteins that function in the _____ or will be _______ to another destination, such as a different organelle, the plasma membrane, or secreted to the cell exterior.
ribosomes
The rough ER is named for its appearance in transmission electron micrographs. The knobby-looking structures in the rough ER are ______ that are attached to the membrane.
enzymes, lipids
The smooth ER contains ____________ that catalyze reactions involving _____________.
protein, lipid
The structure of the endoplasmic reticulum correlates closely with its function. -The rough ER has ribosomes and functions primarily as a __________-manufacturing center. -The smooth ER lacks ribosomes and functions primarily as a __________-processing center.
endocytosis
There are 3 pathways that animal cells commonly use to recycle material in the lysosome. -Two of these three pathways involve pinching off the plasma membrane to take up material from outside the cell, by a process called __________.
actin filaments, intermediate filaments, microtubules.
There are three distinct cytoskeletal elements in eukaryotic cells: __________ ___________, ___________ ___________, and ___________.
endosymbiosis
These attributes are odd compared with those of the other organelles and have led biologists to propose that mitochondria and chloroplasts were once free-living bacteria. -According to the ____________ theory, these bacteria were engulfed by the ancestors of modern eukaryotes, but were not destroyed - instead, a mutually beneficial relationship evolved.
ER signal sequence
They identified a "send-to-ER" signal, or *____ ______ _______*, that moves the growing protein and associated ribosome to the rough ER. -The ER signal sequence typically is present in the first 20 amino acid residues and is removed when protein synthesis is complete.
nucleus
This division is mostly based on cell morphology - eukaryotic cells have a membrane-bound compartment called a ___________, and prokaryotic cells do not.
cristae
Unlike mitochondria, however, chloroplasts have no _________ extending from the inner membrane into the interior.
kinesin
Vesicles move through the cell along microtubules thanks to the motor protein ___________.
peroxisomes
Virtually all eukaryotic cells contain globular organelles called ____________. -These organelles have a single membrane and originate as vesicles from the ER.
plus
When ATP is hydrolyzed by kinesin, the protein moves along microtubules in a directional manner: toward the ______ end
cis trans
When the cisternae are stacked in this way, the Golgi apparatus has a distinct polarity or sidedness. -The _____ surface is closest to the nucleus, and the ______ surface is oriented toward the plasma membrane.
larger, nucleoid, nucleus, organelles
When typical prokaryotic and eukaryotic cells are compared, three key differences stand out: 1. Eukaryotic cells are generally much ________ than prokaryotic cells. 2. Prokaryotic chromosomes are in a loosely defined ___________ region while eukaryotic chromosomes are enclosed within a membrane-bound compartment called the _________. 3. The cytoplasm of eukaryotic cells is compartmentalized into a larger number of distinct __________ compared to the cytoplasm in prokaryotic cells.
Proton pumps
________ ________ in the lysosomal membrane maintain an acidic pH in the lumen of the lysosome by importing hydrogen ions.
ribosomes, RNA, protein
____________ are complex structures composed of large and small subunits, each of which contains ______ and _______ molecules.
Microtubules
____________ are the largest cytoskeletal components in terms of diameter. -They are assembled from subunits consisting of 2 polypeptides, a-tubulin and B-tubulin, that exist as stable protein *dimers*.
