Proteins

Question 1

What do proteins account for?

Answer 1

Proteins account for more than 50% of the dry mass of most cells
* They are instrumental in almost everything an organism does

Question 2

What do protein enzymes function as

Answer 2

catalysts in cells, regulating metabolism by selectively accelerating certain chemical reactions without being consumed – function repeatedly

Question 3

Catalytic cycles

Answer 3

Hydrolysis of sucrose into glucose & fructose is accelerated by sucrase

Question 4

Polypeptides

Answer 4

Polymers of proteins are called polypeptides. A protein consists of one or more polypeptides folded and coiled into a specific conformation

Question 5

What are all proteins constructed from?

Answer 5

All protein polymers are constructed from the same 20 amino acid monomers

Question 6

Proteins

Answer 6

Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins are the most structurally complex molecules are known, each type of protein has a complex three-dimensional shape

Question 7

Amino Acids

Answer 7

• Amino acids are the monomers from which protein are constructed
• Amino acids are organic molecules with both carboxyl and amino groups

Question 8

The R group

Answer 8

The physical and chemical properties of the R group determine the unique characteristics of a particular amino acid

Question 9

First R group

Answer 9

• One group of amino acids has nonpolar hydrophobic R groups

Question 10

Second R group

Answer 10

• Another group of amino acids has polar, hydrophilic R groups

Question 11

Third R group

Answer 11

A third group of amino acids has functional groups that are charged (ionized) at cellular pH

Question 12

Carboxyl R group

Answer 12

Some acidic R groups have a negative charge due to the presence of a carboxyl group

Question 13

Acidic R group

Answer 13

Basic R groups have amino groups with a positive charge

Question 14

How are amino acids joined

Answer 14

• Amino acids are joined
  through a dehydration
  reaction forming
  peptide bonds
• A polypeptide chain

Question 15

What does a functional protein consist of?

Answer 15

A functional protein consists of one or more polypeptides twisted, folded, and coiled into a unique shape

Question 16

What is a groove?

Answer 16

recognises and binds to target molecules

Question 17

What does the sequence of amino acids determine?

Answer 17

a protein’s three-dimensional structure

Question 18

what does a protein’s structure determine?

Answer 18

it’s function

Question 19

What does the function of a protein depend on?

Answer 19

its ability to recognize and bind to some other molecule

Question 20

Four levels of protein structure

Answer 20

Proteins share three superimposed levels of structure: primary, secondary, and tertiary structures which organize the folding within a single polypeptide

Question 21

Primary Structure

Answer 21

• Primary structure, the sequence of amino acids in a protein, is like the order of letters in a long word

Question 22

Secondary Structure

Answer 22

Most proteins have segments of their polypeptide chains repeatedly coiled or folded
* These coils and folds are referred to as secondary structures and result from hydrogen bonds between the repeating constituents of the polypeptide backbone
* α helix structure (keratin), β pleated sheet(spider’s silk)

Question 23

Tertiary structure

Answer 23

• Tertiary structure is determined
  by interactions among various R
  groups

Question 24

What do these R-group interactions include

Answer 24

• These interactions include hydrogen, ionic bonds and hydrophobic interactions and van der Waals interactions among hydrophobic R groups

Question 25

What is the cumulative effect of these weak R-group interactions?

Answer 25

• Although these three interactions are relatively weak, their cumulative effect helps give the protein a unique shape

Question 26

Quaternary structure

Answer 26

results from the aggregation of two or more polypeptide subunits

Question 27

Example of Quaternary structure

Answer 27

• Haemoglobin is a globular protein with a quaternary structure of four polypeptide subunits

Question 28

A change in protein structure

Answer 28

Even a slight change in the primary structure can affect a protein’s conformation and ability to function

Question 29

A change in protein structure example

Answer 29

• The substitution of one amino acid (valine) for the normal one (glutamic acid) at a particular position in the primary structure of haemoglobin, the protein that carries oxygen in red blood cells, can cause sickle-cell disease, an inherited blood disorder

Question 30

Denaturation

Answer 30

• This loss of a protein’s native structure
• A denatured protein is biologically inactive

Question 31

What determines protein structure?

Answer 31

• In addition to primary structure, physical and chemical
  conditions can affect structure
• Alterations in pH, salt concentration, temperature, or
  other environmental factors can cause a protein to
  unravel