cell bio chp. 15

What must happen in order for a cell to operate effectively?

What must happen in order for a cell to operate effectively?

the different intracellular processes that occur simultaneously must be segregated

Describe ONE WAY a cell can isolate and organize their chemical reactions:

to group the different enzymes required to catalyze a particular sequence of reactions into lare, multicomponent complexes (protein machines)

What’s another way a cell can isolate and organize their chemical reactions?

to confine different metabolic processes within different membrane-enclosed compartments, the organelles

Which cell is sub-divided by internal membranes?

eukaryotic cells; includes many small, irregularly shaped structures arranged w/o apparent order

Functions of cytosol:

contains many metabolic pathways; protein synthesis occurs; the cytoskeleton

Functions of the nucleus:

contains main genome; DNA and RNA synthesis occurs

Functions of endoplasmic reticulum:

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

Functions of the golgi apparatus

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

What do the lysosomes do?

intracellular degradation

What do endosomes do?

sort endocytosed material

The mitochondria does…?

synthesizes ATP by oxidative phosphorylation

What function does the chloroplasts have?

ATP synthesis and carbon fixation by photosynthesis

What does peroxisomes do?

oxidative breakdown of toxic molecules

Why is directing newly made proteins to their correct area important?

it’s needed for the cell to grow, divide, and function properly

What is protein sorting?

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

Where does the synthesis of most proteins in the cell begin?

at the free floating ribosomes located in the cytosol

Which interior structure produces some of its own proteins?

the mitochondria and chloroplasts

For the interior of a cell, where are the proteins delievered from?

the cytosol

What happens to the proteins in the ER?

some stay but most are transported by vesicles to the golgi apparatus and then to the plasma membrane/other organelles

What happens to the proteins and lipids in the golgi apparatus, lysosomes, and the inner nuclear membrane?

they are delivered indirectly via the smooth and rough ER

Give the three ways proteins are transported:

from the cytosol into the interior of the nucleus (through nuclear pores), cytosol into the ER, mitochondria, and chloroplasts (through protein translocators), and the ER to other components of the endomembrane system (by transport vesicles)

When an organelle imports a protein to its interior, it must be transported across/through what?

its phospholipid membrane

What are sorting signal sequences made of and what happens once its done sorting?

15-60 amino acid strand and it’s removed from the finished protein once it has been sorted (nuclear proteins keep their signal sequence)

What happens to the proteins that don’t have a signal sequence?

they remain and function in the cytosol

WHat is the term for another form of targeting proteins to specific locations that is made up of a.a that are distant from each other in the tertiary structure of the folded protein?

signal patches

The ___ encloses the nuclear DNA and is the boundary of the nuclear compartment.

nuclear envelope

The nuclear envelope is formed from:

inner nuclear membrane and outer nuclear membrane

Inner nuclear membrane:

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

Outer nuclaer membrane:

resembles the membrane of the ER

What are nuclear pores?

physical holes in the membrane that act as gates for water-soluble molecules and proteins to travel through

Traffic flow of molecules through nuclear pores into the nucleus:

newly made proteins enter from the cytosol

Traffic flow of molecules through nuclear pores out of the nucleus:

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

Because larger molecules/macromolecules can’t easily pass through to enter/exit the nucleus, they have…?

nuclear localization signal that consists of one or two short sequences containing several positively charged a.a. (lysines or arginines)

After the nuclear localization signal region of the protein is recognized by cytosolic proteins called nuclear import receptors, what happens?

the receptors bind to signal sequence and help direct the protein from the cytosol to the nuclear pore

What does the nuclear export receptors do differently than nuclear import receptors?

transports materials out of the nucleus and into the cytosol

How does a protein get transported from the cytosol into the mitochondria, chloroplasts, peroxisomes, or ER?

via special transport proteins called translocators that form translocator channels through the membrane and the protein is transported across the membrane through the channel in an unfolded state

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