Chapter 7- Inside the Cell

7.1 Bacterial and Archaeal Cell Structures and Their Functions

Transmission electron microscope, which passes a beam of electrons through extremely thin sections of cells to visualize their internal structure
The most prominent structure inside a prokaryotic cell is the chromosome
- Segments of DNA that contain information for building functional RNAs, some of which may be used to make polypeptides, which are called genes.
The region of the cell where the circular chromosome is located is called the nucleoid
Plasmids contain genes but are physically independent of the cellular chromosome.
Ribosomes are observed in all prokaryotic cells and are found throughout the cell interior.
Protein filaments such as these form the basis of the cytoskeleton
An organelle is a compartment inside the cell-often bounded by a membrane- that contains enzymes or structures specialized for a particular function.
Bacterial organelles perform specialized tasks, including:
- storing calcium ions
- holdingcrγstals of the mineral magnetite, which function like compass needles to help cells swim in a directed way
- concentrating enzymes responsible for synthesizing complex carbon compounds from carbon dioxide.
In most bacteria and archaea, this pressure is resisted by a stiff cell wall.
A prokaryotic flagellum (plural: flagella) is assembled from many different proteins at the cell surface of certain species.
A fimbria (plural: fimbriae) is a needle-like projection that extends from the plasma membrane of some bacteria and promotes attachment to other cells or surfaces.

7.2 Eukaryotic Cell Structures and Their Functions

As a cell increases in diameter, its volume increases more than its surface area.
Because eukaryotic cells are subdivided, the cytosol-the fluid portion between the plasma membrane and 1ese organelles-is only a fraction of the total cell volume.
While prokaryotic chromosomes are in a loosely defined nucleoid region, eukaryotic chromosomes are enclosed within a membrane bound compartment called the nucleus.
- It is enclosed by a unique double-membrane structure called the nuclear envelope.
- 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 the nuclear lamina.
One of these regions, called the nucleolus, is responsible for manufacturing and processing the RNA molecules that assemble into large and small ribosomal subunits.
Portions of the nuclear envelope extend into the cytoplasm to form an extensive membrane enclosed factory called the endoplasmic reticulum (ER)
The rough endoplasmic reticulum, or more simply rough ER, is named for its appearance in transmission electron micrographs
The inside compartment of the rough ER, like the interior of any sac-like structure in a cell or body, is called the lumen.
The smooth endoplasmic reticulum or smooth ER are parts of the ER that are free of ribosomes that appear smooth and even.
Most of the proteins that leave the rough ER must pass through the Golgi apparatus before reaching their final destination.
The Golgi apparatus consists of a set of membranous compartments called cisternae.
Animal cells contain organelles called lysosomes that function as recycling center
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 endomembrane system.
The cells of plants, fungi, and certain other eukaryotes contain a prominent organelle called a vacuole.
Virtually all eukaryotic cells contain globular organelles called peroxisomes
In the leaves of plants, specialized peroxisomes called glyoxysomes are packed with enzymes that oxidize fatty acids to form a compound that can be used to store energy for the cell.
The organelle primarily responsible for supplying ATP in animals, plants, and virtually all other eukaryotic cells is the mitochondrion
- The solution enclosed within the inner membrane is called the mitochondrial matrix.
- Each mitochondrion has many copies of a small, circular-in some species,linear-chromosome called mitochondrial DNA (mtDNA) that is independent of the nuclear chromosomes.
Most algal and plant cells possess an organelle called the chloroplast, in which sunlight is converted to chemical energy during photosynthesis
A third membrane forms an independent network of hundreds of flattened, sac-like structures called thylakoids throughout the interior.
Most thylakoids are arranged in interconnected stacks called grana
The fluid-filled space surrounding grana, called the stroma, contains enzymes that use this chemical energy to produce sugars.
According to the endosymbiosis theory, these bacteria were engulfed by the ancestors of modern eukaryotes, but were not destroyed-instead, a mutually beneficial relationship evolved.
The cells of animals lack a cell wall, but are often supported by a more diffuse mixture of secreted proteins and polysaccharides that form the extracellular matrix, orECM.
Within a cell, the structure of each component correlates with its function.

7.3 Putting the Parts into a Whole

For several decades,
A technique called differential centrifugation was particularly important because it allowed researchers to isolate particular cell components and analyze their chemical composition.

7.4 Cell Systems I: Nuclear Transport

Ribosomal RNAs are manufactured in the nucleolus, where they bind to proteins to form the large and small subunits of ribosomes.
Molecules called messenger RNAs (mRNA) carry the information required to manufacture proteins.
Nuclear localization signal (NLS) is where proteins that leave the nucleus have a different signal, required for nuclear export.

7.5 Cell Systems II: The Endomembrane System Manufactures, Ships, and Recycles Cargo

George Palade and colleagues did pioneering research on the secretory pathway using a pulse chase experiment to track protein movement.
This strategy is based on two steps
- The “Pulse”: Expose experimental cells to a high concentration of a modified amino acid for a short time.
- The “Chase”: End the pulse by washing away the modified amino acid and replacing it with the normal version of the same molecule.
The cells for the experiment were grown in culture, or in vitro.
They identified a “send-to-ER” signal, or ER signal sequence, that guides the growing protein and associated ribosome to the rough ER.
The signal sequence binds to a signal recognition particle (SRP)-a complex of RNA and protein.
Because carbohydrates are polymers of sugar monomers, the addition of one or more carbohydrate groups is called glycosylation. The resulting molecule is a glycoprotein.
When exocytosis occurs, the vesicle membrane and plasma membrane make contact.
Two of these three pathways involve pinching off the plasma membrane to take up material from outside the cell-a process called endocytosis
- As its name implies, receptor mediated endocytosis is a sequence of events that begins when particles outside the cell bind to receptors on the plasma membrane.
These vesicles then drop off their cargo in an organelle called the early 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 late endosome.
A second pathway that involves recycling material brought in from 1e outside of the cell is called phagocytosis
Cells are also involved in recycling large structures and organelles that exist within the cytoplasm through a process called autophagy

7.6 Cell Systems III: The Dynamic Cytoskeleton

The cytoskeleton is a dense and complex network of fibers that helps maintain cell shape by providing structural support.
Sometimes called microfilaments because they are the cytoskeletal element with the smallest diameter, actin filaments are fibrous structures made of globular protein subunits called actin
Myosin is a motor protein-a protein that converts the chemical energy in ATP into the kinetic energy of mechanical work, just as a car’s motor converts the chemical energy in gasoline into spinning wheels.
Cytokinesis (“cell-moving”) is 1e final stage in cell division when the cytoplasm is divided to form two cells.
Cytoplasmic streaming is the directed flow of cytosol and organelles that is often seen within plant and fungal cells.
In addition, the movement called cell crawling occurs when groups of actin filaments grow, causing bulges in the plasma membrane that extend and move the cell.
There are many types of intermediate filament, each consisting of a different-though similar in size and structure-type of protein subunit
Nuclear lamins, which make up the nuclear lamina layer
Microtubules have the largest diameter of the three cytoskeletal filaments.
The eukaryotic flagellum is closely related to a structure called the cilium (plural: cilia), which is a short, hairlike projection that is also found in some eukaryotic cells
The nine doublets of the axoneme originate from a structure called the basal body.

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Chapter 7- Inside the Cell

7.1 Bacterial and Archaeal Cell Structures and Their Functions

Transmission electron microscope, which passes a beam of electrons through extremely thin sections of cells to visualize their internal structure
The most prominent structure inside a prokaryotic cell is the chromosome
- Segments of DNA that contain information for building functional RNAs, some of which may be used to make polypeptides, which are called genes.
The region of the cell where the circular chromosome is located is called the nucleoid
Plasmids contain genes but are physically independent of the cellular chromosome.
Ribosomes are observed in all prokaryotic cells and are found throughout the cell interior.
Protein filaments such as these form the basis of the cytoskeleton
An organelle is a compartment inside the cell-often bounded by a membrane- that contains enzymes or structures specialized for a particular function.
Bacterial organelles perform specialized tasks, including:
- storing calcium ions
- holdingcrγstals of the mineral magnetite, which function like compass needles to help cells swim in a directed way
- concentrating enzymes responsible for synthesizing complex carbon compounds from carbon dioxide.
In most bacteria and archaea, this pressure is resisted by a stiff cell wall.
A prokaryotic flagellum (plural: flagella) is assembled from many different proteins at the cell surface of certain species.
A fimbria (plural: fimbriae) is a needle-like projection that extends from the plasma membrane of some bacteria and promotes attachment to other cells or surfaces.

7.2 Eukaryotic Cell Structures and Their Functions

As a cell increases in diameter, its volume increases more than its surface area.
Because eukaryotic cells are subdivided, the cytosol-the fluid portion between the plasma membrane and 1ese organelles-is only a fraction of the total cell volume.
While prokaryotic chromosomes are in a loosely defined nucleoid region, eukaryotic chromosomes are enclosed within a membrane bound compartment called the nucleus.
- It is enclosed by a unique double-membrane structure called the nuclear envelope.
- 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 the nuclear lamina.
One of these regions, called the nucleolus, is responsible for manufacturing and processing the RNA molecules that assemble into large and small ribosomal subunits.
Portions of the nuclear envelope extend into the cytoplasm to form an extensive membrane enclosed factory called the endoplasmic reticulum (ER)
The rough endoplasmic reticulum, or more simply rough ER, is named for its appearance in transmission electron micrographs
The inside compartment of the rough ER, like the interior of any sac-like structure in a cell or body, is called the lumen.
The smooth endoplasmic reticulum or smooth ER are parts of the ER that are free of ribosomes that appear smooth and even.
Most of the proteins that leave the rough ER must pass through the Golgi apparatus before reaching their final destination.
The Golgi apparatus consists of a set of membranous compartments called cisternae.
Animal cells contain organelles called lysosomes that function as recycling center
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 endomembrane system.
The cells of plants, fungi, and certain other eukaryotes contain a prominent organelle called a vacuole.
Virtually all eukaryotic cells contain globular organelles called peroxisomes
In the leaves of plants, specialized peroxisomes called glyoxysomes are packed with enzymes that oxidize fatty acids to form a compound that can be used to store energy for the cell.
The organelle primarily responsible for supplying ATP in animals, plants, and virtually all other eukaryotic cells is the mitochondrion
- The solution enclosed within the inner membrane is called the mitochondrial matrix.
- Each mitochondrion has many copies of a small, circular-in some species,linear-chromosome called mitochondrial DNA (mtDNA) that is independent of the nuclear chromosomes.
Most algal and plant cells possess an organelle called the chloroplast, in which sunlight is converted to chemical energy during photosynthesis
A third membrane forms an independent network of hundreds of flattened, sac-like structures called thylakoids throughout the interior.
Most thylakoids are arranged in interconnected stacks called grana
The fluid-filled space surrounding grana, called the stroma, contains enzymes that use this chemical energy to produce sugars.
According to the endosymbiosis theory, these bacteria were engulfed by the ancestors of modern eukaryotes, but were not destroyed-instead, a mutually beneficial relationship evolved.
The cells of animals lack a cell wall, but are often supported by a more diffuse mixture of secreted proteins and polysaccharides that form the extracellular matrix, orECM.
Within a cell, the structure of each component correlates with its function.

7.3 Putting the Parts into a Whole

For several decades,
A technique called differential centrifugation was particularly important because it allowed researchers to isolate particular cell components and analyze their chemical composition.

7.4 Cell Systems I: Nuclear Transport

Ribosomal RNAs are manufactured in the nucleolus, where they bind to proteins to form the large and small subunits of ribosomes.
Molecules called messenger RNAs (mRNA) carry the information required to manufacture proteins.
Nuclear localization signal (NLS) is where proteins that leave the nucleus have a different signal, required for nuclear export.

7.5 Cell Systems II: The Endomembrane System Manufactures, Ships, and Recycles Cargo

George Palade and colleagues did pioneering research on the secretory pathway using a pulse chase experiment to track protein movement.
This strategy is based on two steps
- The “Pulse”: Expose experimental cells to a high concentration of a modified amino acid for a short time.
- The “Chase”: End the pulse by washing away the modified amino acid and replacing it with the normal version of the same molecule.
The cells for the experiment were grown in culture, or in vitro.
They identified a “send-to-ER” signal, or ER signal sequence, that guides the growing protein and associated ribosome to the rough ER.
The signal sequence binds to a signal recognition particle (SRP)-a complex of RNA and protein.
Because carbohydrates are polymers of sugar monomers, the addition of one or more carbohydrate groups is called glycosylation. The resulting molecule is a glycoprotein.
When exocytosis occurs, the vesicle membrane and plasma membrane make contact.
Two of these three pathways involve pinching off the plasma membrane to take up material from outside the cell-a process called endocytosis
- As its name implies, receptor mediated endocytosis is a sequence of events that begins when particles outside the cell bind to receptors on the plasma membrane.
These vesicles then drop off their cargo in an organelle called the early 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 late endosome.
A second pathway that involves recycling material brought in from 1e outside of the cell is called phagocytosis
Cells are also involved in recycling large structures and organelles that exist within the cytoplasm through a process called autophagy

7.6 Cell Systems III: The Dynamic Cytoskeleton

The cytoskeleton is a dense and complex network of fibers that helps maintain cell shape by providing structural support.
Sometimes called microfilaments because they are the cytoskeletal element with the smallest diameter, actin filaments are fibrous structures made of globular protein subunits called actin
Myosin is a motor protein-a protein that converts the chemical energy in ATP into the kinetic energy of mechanical work, just as a car’s motor converts the chemical energy in gasoline into spinning wheels.
Cytokinesis (“cell-moving”) is 1e final stage in cell division when the cytoplasm is divided to form two cells.
Cytoplasmic streaming is the directed flow of cytosol and organelles that is often seen within plant and fungal cells.
In addition, the movement called cell crawling occurs when groups of actin filaments grow, causing bulges in the plasma membrane that extend and move the cell.
There are many types of intermediate filament, each consisting of a different-though similar in size and structure-type of protein subunit
Nuclear lamins, which make up the nuclear lamina layer
Microtubules have the largest diameter of the three cytoskeletal filaments.
The eukaryotic flagellum is closely related to a structure called the cilium (plural: cilia), which is a short, hairlike projection that is also found in some eukaryotic cells
The nine doublets of the axoneme originate from a structure called the basal body.