Cell Biology Chapter 3 Proteins

Question 1

Proteins are extremely important macromolecules in all what?

Answer 1

all organisms occurring nearly everywhere in the cell

Question 2

What 9 major class does protein fall into?

Answer 2

Enzymes serve as catalyst increasing the rates of chemical reactions; structural proteins-physical support and shape; motility proteins- contraction and movement; regulatory proteins- control and coordinate cell function; transport proteins- move substances in and out of cells; signaling proteins-communication between cells; receptor proteins- enable cells to respond to chemical stimuli from the environment; defensive proteins- protect against disease; storage proteins- reservoirs of amino acids

Question 3

Only what number of amino acids are used in protein synthesis? No two different proteins have the same what? What is the basic structure of every amino acid?

Answer 3

20 kinds; amino acid sequence; an alpha carbon attached to an amino group, a carboxyl group and variable side chain (R group)

Question 4

What is an R group? What depends on the nature of their R group? How are amino acids linked together stepwise?

Answer 4

unique side chain; specific properties of amino acids; into a linear polymer by dehydration (loss of water)

Question 5

As three atoms comprising H2O are removed what is formed; What type of bond is it? Because of the way it’s formed what do they have? What is the end amino and the end carboxyl group?

Answer 5

peptide bond is formed; is a covalent C-N bond; polypeptides have directionality (polarity); amino group end is called N- or amino terminus; carboxyl group is called C- or carboxyl terminus

Question 6

What is a polypeptide? What is protein synthesis? A polypeptide does not become a protein until it is?

Answer 6

the immediate product of amino acid polymerization; process of elongating a chain of amino acids; unique, stable, three-dimensional shape and is biologically active

Question 7

What is a monomeric protein? What is a multimeric protein

Answer 7

consist of a single polypeptide; consist of 2 of more polypeptides

Question 8

What is conformation and what does it need? How do the disulfide bonds form?

Answer 8

a protein is to adopt its proper shape; covalent bonds; covalent disulfide bonds form between the sulfur atoms of two cysteine residues

Question 9

Examples of noncovalent interactions

Answer 9

ionic- between charged aa side chains and other aa or molecules; hydrogen- between aa and other aa or molecules (water); van der waals- weak non-covalent interactions between nonpolar molecules; hydrophobic- nonpolar aa will associate with each other to avoid interaction with aqueous solutions

Question 10

Noncovalent bonds and interactions are required for what? What determines the overall 3D structure of a protein?

Answer 10

required for polypeptides to form multimeric proteins; determined by the interactions of R-groups

Question 11

What are chaperones? What do they not dictate and what do they increase? What do they do to prevent incorrect interactions? What do they provide?

Answer 11

specialized proteins that facilitate correct protein folding; folding, not required but do increase the efficiency of proper folding; bind to hydrophobic regions of newly synthesized proteins to prevent incorrect interactions; protected chamber providing protective environment

Question 12

4 levels of organization that describes the overall shape and structure of a protein

Answer 12

Primary structure, secondary structure, tertiary structure, and quaternary structure

Question 13

What is the primary structure how is it written and why is it important genetically?

Answer 13

amino acid sequence; written from the N-terminus to the C-terminus the direction in which the polypetide was synthesized; the sequence is specified by the order of nucleotides in the corresponding messenger RNA

Question 14

Why is the amino acid important structurally?

Answer 14

the order and identity of amino acids directs the formation of the higher-order (secondary +) structures

Question 15

What is secondary structure; What does the secondary structure of a protein describe?

Answer 15

local folding of polypeptide; local regions of structure that result from hydrogen bonding between NH and CO groups along the polypeptide backbone

Question 16

The O and N atoms are what causing them to be what? This causes the H near them to be what? These charges what and result in what?

Answer 16

highly electronegative causing them to be partially negatively charged; partially positively charged; attract themselves and result in two major patterns, the a helix and the b sheet

Question 17

H bonding in an a helix is what? H bonding in the b sheet can be either what?

Answer 17

invariably intramolecular (within the same polypeptide); intramolecular (between 2 segments of the same polypetide) or intermolecular (linking 2 different polypeptides)

Question 18

Protein regions for b sheet can interact with each other in what 2 different ways?

Answer 18

Parallel b sheet- the two interaction regions run in the same N-terminus to C-terminus direction; antiparallel b sheet- the 2 strands run in opposite N-terminus to C-terminus directions

Question 19

What is tertiary structure? What does it reflect and what does the tertiary structure result from?

Answer 19

3D- conformation; reflects the unique aspect of the amino acid sequence because it depends on interactions of the R groups; sum of hydrophobic residues avoiding water and hydrophillic residues interacting with water

Question 19

What is tertiary structure? What does it reflect and what does the tertiary structure result from?

Answer 19

3D- conformation; reflects the unique aspect of the amino acid sequence because it depends on interactions of the R groups; sum of hydrophobic residues avoiding water and hydrophillic residues interacting with water

Question 20

What is the Quaternary structure? What is the quaternary structure of protein and what does the term apply to specifically?

Answer 20

interactions between monomeric proteins to form a multimeric unit; level of organization concerned with subunit interactions and assembly; multimeric proteins

Question 21

The bonds and forces maintaining quaternary structures are what? The process of subunit formation is usually what? Molecular chaperones are required to assist what?

Answer 21

the same as those responsible for tertiary structure; spontaneous; the process

Question 22

What are motifs? When the same motif is present in different proteins what does it usually do?

Answer 22

secondary structure stretches of a helices and/or b sheet; usually serves the same purpose

Question 23

What is a domain, how long is it typically and with what? What do proteins with similar functions often share? Proteins with multiple functions usually have what?

Answer 23

discrete locally folded unit of tertiary structure with a specific function; typically 50-350 amino acids long with regions of a helices and b sheets packed together; share a common domain; separate domain for each function

Question 24

When is a higher level assembly possible? Each protein in the complex may be involved how and elaborate?

Answer 24

in the case of proteins (often enzymes) that are organized into multiprotein complexes; sequentially in a common multistep process; organizing enzymes that catalyze sequential reactions into single multi enzyme complex