Chapter 15: Intracellular Compartments and Protein Transport

chemical reactions

at any one time, a typical eukaryotic cell carries out thousands of different

incompatible

many chemical reactions are mutually

segregated

for a cell to operate effectively, the different intracellular processes that occur simultaneously must somehow be

aggregate

one way to isolate and organize chemical reactions is to _______ the different enzymes required to catalyze a particular sequences of reactions into large, multicomponent complexes

DNA replication and protein synthesis

Examples of aggregating chemical reactions are

confine different metabolic processes

Another way to isolate and organize chemical reactions is to _____________ within different membrane enclosed compartments, the organelles

organelles

membrane enclosed compartment

unique set of proteins

each organelle contains what that has to be transferred selectively from the cytosol, where they are made, to the compartment where the are used

prokaryotic cells

Cells that usually consists of a single compartment enclosed by the plasma membrane

eukaryotic cells

cells that are sub-divided by internal membranes

internal membranes

eukaryotic cells are sub-divided by

plasma membrane

prokaryotic cells are enclosed by

specialized function

membrane enclosed organelles are all distinct, each of which contain a unique set of large and small molecules that determine its

half

Organelles occupy nearly _______ the volume of a eukaryotic cell

endoplasmic reticulum membrane

In a typical mammalian cell, the area of the ___________ is 20-30 times greater than that of the plasma membrane

plasma membrane

the endoplasmic reticulum membrane is greater than the

plasma membrane

what is only a minor membrane in most eukaryotic cells

cytosol

contains many metabolic pathways; protein synthesis; the cytoskeleton

nucleus

contains main genome; DNA and RNA synthesis

endoplasmic reticulum

synthesis of most lipids; synthesis of proteins for distribution to many organelles and to the plasma membrane

golgi apparatus

modification, sorting, and packaging of proteins and lipids for either secretion or delivery to another organelle

lysosomes

intracellular degradation

endosomes

sorting of endocytosed material

mitochondria

ATP synthesis by oxidative phosphorylation

chloroplasts

ATP synthesis and carbon fixation by photosynthesis

peroxisomes

oxidation of toxic molecules

perform their function

the newly made proteins must be accurately delivered to their appropriate organelles, where they will

grow, divide, and function properly

directing newly made proteins to their correct organelle is therefore necessary for any cell to

vesicles

For the ER, some proteins stay there, but most are transported by __________ to the Golgi apparatus and then onward to the plasma membrane or other organelles

smooth and rough ER

for the Golgi apparatus, lysosomes, and the inner nuclear membrane, proteins and lipids are delivered indirectly via

Golgi apparatus

Lysosomes and the inner nuclear membrane, proteins and lipids are delivered indirectly via smooth and rough ER

mitochondria and chloroplasts

what also makes some of their own proteins

ribosomes

the synthesis of most proteins in the cell begins at ________ located in the cytosol

cytosol

the synthesis of most proteins in the cell begins at ribosomes located in the

mitochondria and chloroplast proteins

exceptions of the synthesis of proteins beginning in the cell at ribosomes are

protein sorting

the process of transporting a protein to its destination where it will function

sorting signal

a particular segment of the proteins' amino acids sequence will act as a ____________ and is involved in directing the protein to a particular organelle or location

different sorting signals

what directs proteins into the nucleus, mitochondria, chloroplasts, peroxisomes, and the ER

sorting signal

directs the protein to the organelle in which it is required

sorting signal

a protein that lacks what will remain and function in the cytosol

cytosolic protein

removal of the signal sequence from an ER protein converts it into a

ER protein

addition of a signal sequence to a cytosolic protein converts it to an

signal sequence

what is often removed from the finished protein once it has been sorted

signal patches

what is another form of targeting proteins to specific locations

amino acids

signal patches are made up of _________ that are distant to one another in the primary sequences, but come close to each other in the tertiary structure of the folded protein

primary sequence

signal patches are distant to one another in the

tertiary structure

signal patches come close to each other in the

directing proteins to the nucleus

signal patches are commonly used for

water soluble protein

when a membrane-enclosed organelle imports a ____________ to its interior, it must be transported across or through its membrane

nuclear pores

proteins moving from the cytosol into the nucleus are transported through the

selective gates

Nuclear pores function as _______ that actively transport specific macromolecules, but also allow free diffusion of smaller molecules

protein translocators

Proteins moving from the cytosol into the ER, mitochondria, or chloroplasts are transported across the organelle membrane by

translocator channels

translocator proteins form __________ through the membrane

unfolded state

protein is transported across the membrane through the translocator channel in an

transport vesicles

proteins moving onward for the ER are transported by

vesicular transport

transport of proteins synthesized in the ER move via _________ through the secretory pathway, from ER to Golgi to cell surface/lysosomes

transport vesicles

pinch off from the membrane of one organelle and then fuse with the membrane of a second

membrane lipids and proteins

what is also delivered to other organelles in other organelles by transport vesicles

nuclear envelope

encloses the nuclear DNA and defines the nuclear compartment and is formed from two membranes

inner nuclear membrane

contains proteins that act as anchoring sites for chromosomes; nuclear lamina provides structural support for nuclear envelope

nuclear lamina

what provides structural support for nuclear envelope

outer nuclear membrane

closely resembles the membrane of the ER and is continuous with it

nuclear pores

physical holes in the membrane that act as gates for molecules to travel through

into the nucleus

newly made proteins enter from the cytosol before going

out of the nucleus

RNA molecules synthesized in the nucleus and ribosomal subunits assembled in the nucleus before going

larger molecules

what cannot easily pass through to enter/exit nucleus

nuclear localization signal

a type of sorting signal that typically consists of one or two short sequences containing several positively charged amino acids

cytosolic proteins

the nuclear localization signal region of the protein is recognized by

nuclear import receptors

the cytosolic proteins that recognize the nuclear localization signal are called

fully folded conformation

nuclear pore transports proteins in their

unfolded

for mitochondria and chloroplasts, proteins are _______ before they cross the membrane

inner and outer membranes

both mitochondria and chloroplasts have

proteins

what is encoded by the nucleus and imported from the cytosol

N-terminus

proteins targeted to mitochondria and chloroplast usually have a signal sequence at their ________ that contains both hydrophobic and positively charged amino acids

import receptors

the signal sequence is recognized by specific proteins attached to the organelle membrane called

chaperone proteins

additional proteins that aid in the transport of the protein across the two membranes and help fold it back into its tertiary structure once inside

specificity

The ________ between the interaction of the signal sequence and import receptor is what directs a protein from a cytosol to the given organelle

translocator channel

translocators help to produce a

unfold

what do proteins do to enter mitochondria and chloroplasts

translocation

When proteins enter the mitochondria and chloroplasts, Each protein is unfolded as it is transported, and its signal sequence is removed after __________ is complete

lipids

what also needs to be transported into mitochondria and chloroplast to maintain their membranes

smooth ER

what is the main site of lipid synthesis in the cell

smooth ER

most of lipids membrane phospholipids are though to be import from what

lipid carrying proteins

Lipid membrane phospholipids are transported to these organelles by

peroxisomes

small, membrane-enclosed organelles that contain several enzymes that produce hydrogen peroxide and have a variety of other functions

peroxisomes

break down a variety of molecules, including toxins, alcohol and fatty acids; synthesize certain phospholipids, including those that are abundant in the myelin sheath that insulates nerve cell axons

eukaryotic cells

peroxisomes are present in all

ribosomes

peroxisomes acquire the bulk of their proteins

smooth endoplasmic reticulum

peroxisomes can be derived from

fission

peroxisomes can replicated by

short sequence of three amino acids

transport of protein from the cytosol into the peroxisome involves __________ that serve as an import signal for many peroxisomal proteins

import signals

the short sequence of three amino acids serves as _________ for many peroxisomal proteins

receptor proteins

the short sequence of amino acids is recognized by

protein translocator

the peroxisomal membrane contains what that aids in the protein transport

endoplasmic reticulum

what is the most extensive membrane system in a cell

ER

serves as an entry point for proteins destined for other organelles, as well as for itself

water soluble proteins

what kind of proteins are completely translocated across the membrane and enter the ER lumen

prospective transmembrane proteins

what kind of proteins are partly translocated across the ER membrane and become embedded in it

translated

many ER proteins are translocated as they are

rough ER

when a ribosome happens to be making a protein with an ER signal sequence, the signal sequence directs the ribosome to the ER membrane resulting in