chapter 5 section 8

Question 1

What is the proteome?

Answer 1

The full set of proteins expressed in a cell, tissue, or organism at a given time

Question 2

How does the proteome differ from the genome?

Answer 2

The genome is the full set of genes; the proteome reflects actual protein expression and activity.

Question 3

Why is the proteome more complex than the genome?

Answer 3

One gene can produce many protein variants via post-translational modifications, alternative splicing, or RNA editing

Question 4

What does the proteome reveal about a cell?

Answer 4

What the cell is actually doing at a given moment, as proteins are the agents of cellular function

Question 5

Why is the proteome considered large and dynamic?

Answer 5

Proteins are constantly synthesized, modified, assembled, delivered, and degraded, and protein composition varies by cell type and over time

Question 6

How many protein molecules are in a typical bacterial cell?

Answer 6

About 2 million per
10^-15L (approximate E. coli cell volume)

Question 7

How many protein molecules might a human liver cell contain?

Answer 7

Up to ~30 billion molecules.

Question 8

How much can protein copy numbers vary within a human cell?

Answer 8

From ~10 copies to ~100 billion copies per protein, spanning 10 orders of magnitude.

Question 9

What is required to study the proteome effectively?

Answer 9

Global purification strategies and mass spectrometry to identify and quantify proteins.

Question 10

What is the goal of proteomics?

Answer 10

To describe all proteins present in a specific cell type under defined conditions

Question 11

How are proteins separated in typical proteomics experiments?

Answer 11

Using two chromatographic methods: ion exchange (by charge) and reverse phase (by solubility).

Question 12

How are proteins identified after separation?

Answer 12

By electrospray ionization (ESI) mass spectrometry, which measures mass and abundance.

Question 13

How are MS data used to identify proteins?

Answer 13

By comparing measured masses to known protein sequences in databases