Review Set 2

Front 1

2.1 What are the five basic steps needed to send a single from a neuron to a muscle cell?

Back 1

Step 1: Neuron receives information from external environment or other neurons.
Step 2: Neuron integrates, or processes, the information from all of its inputs & determines whether or not to send an output signal. This integration takes place both in time & in space.
Step 3: The neuron propagates the signal along its length at high speed. The distance may be up to several meters with rates up to 100 meters per second.
Step 4: Neuron converts this electrical signal to chemical signal & transmits to another neuron.

Front 2

2.2 What are the three main methods which proteins travel to their destinations in the cell?

Back 2

Proteins can move by gated transport, transmembrane transport, or vesicular transport. (Slide 7 from 'Traffic' lecture)

Front 3

2.3 . What is gated transport and where does it occur? Transmembrane transport? Vesicular transport?

Back 3

Gated Transport: protein traffic between CYTOSOL & NUCLEUS. The nuclear pore complexes function as selective gates that actively transport specific macromolecules and macromolecular assemblies.

Transmembrane transport: membrane-bound protein translocators directly transport specific proteins across a membrane FROM CYTOSOL into a space thats topologically distinct. The transported protein molecule usually must unfold to snake through the translocator.

Vesicular transport: membrane-enclosed transport intermediates—which may be small, spherical transport vesicles or larger, irregularly shaped organelle fragments—ferry proteins FROM E.R. TO GOLGI.

Front 4

2.4 . Distinguish between the structure and role of signal sequences and signal patches

Back 4

Signal sequences: Structure -> continuous stretch of amino acid sequence, typically 15–60 residues long. Role -> Signal sequences are necessary & sufficient for protein targeting.

Signal Patches: Structure -> a complex three-dimensional protein-folding pattern. Role -> They guide proteins to their appropriate destination, where the receptors unload their cargo. The receptors function catalytically: after completing one round of targeting, they return to be reused. Most sorting receptors recognize classes of proteins rather than just an individual protein species. They therefore can be viewed as public transportation systems dedicated to delivering groups of components to their correct location in the cell.

Front 5

2.5 . Describe the structure and function of nuclear pore complexes.

Back 5

Structure -> 4 structural building blocks: column subunits, annular subunits, lumenal subunits, and ring subunits.
Function -> Each pore complex contains one or more open aqueous channels through which small water-soluble molecules can passively diffuse. Each pore complex needs to transport about 100 histone molecules per minute. Each complex also needs to transport about 6 newly assembled large & small ribosomal subunits per minute from the nucleus, where they are produced, to the cytosol, where they are used.

Front 6

2.6 Describe in detail how nuclear import receptors function.

Back 6

Receptors that are encoded by a family of related genes. Each family member encodes a receptor protein that is specialized for the transport of a group of nuclear proteins sharing structurally similar nuclear localization signals.

Front 7

2.7 What are the roles for the RAN proteins in import?

Back 7

The import of nuclear proteins through the pore complex concentrates specific proteins in the nucleus, thereby increasing order in the cell, which must consume energy. The energy is thought to be provided by RAN. RAN is found in both the cytosol and the nucleus, and it is required for import systems.

Front 8

2.8 Describe in detail how Nuclear export receptors function.

Back 8

The nuclear export of large molecules occurs through nuclear pore complexes and depends on a selective transport system. The transport system relies on nuclear export signals on the macromolecules to be exported, as well as on complementary nuclear export receptors. These receptors bind both the export signal and nucleoporins to guide their cargo through the pore complex to the cytosol.

Front 9

2.9 Describe how RAN proteins control both import and export from the nucleus.

Back 9

RAN is found in both the cytosol and the nucleus, and it is required for both the nuclear import and export systems.

Front 10

2.10 What are three differences between nuclear import and mitochondrial import?

Back 10

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