Proteins

Question 1

Proteins

Answer 1

Biopolymers that have many different functions
- enzymes
- structural
- hormones
- transport

Question 2

Amino acids

Answer 2

• amino acids are the monomers that make up proteins
• 20 different amino acids that make up proteins in humans
• Differences in Amino acids are due to R groups/side chains. These can be polar, non-polar, acidic, basic etc.

Question 3

Peptides

Answer 3

Monomers join through condensation reaction to form a peptide bond (amid functional group)

Question 4

Dipeptides

Answer 4

When two amino acids join together through condensation reaction (can be 2 possible products due to different amino and carboxyl groups)

Question 5

Tripeptide

Answer 5

When three amino acids join together through a condensation reaction

Question 6

Polypeptide

Answer 6

Many amino acids join together through condensation reactions and form a polymer (greater than 50 amino acids in a polymer is called a protein)

Question 7

Protein Structure

Answer 7

• The function of a protein is determined by its shape
• all proteins have a primary, secondary and tertiary structure, and some also have a quartenary structure.

Question 8

Primary Structure

Answer 8

The specific sequence of amino acids in the peptide chain including number, type and sequence

Question 9

Secondary structure

Answer 9

• localise folding of a protein chain due ti hydrogen bonding between the oxygen on the carbonyl group of an amino acid and the hydrogen on the amino grip of another amino acid
• Influenced by R groups but does not include interactions of R groups

Question 10

Alpha helix

Answer 10

• Molecule coils into a spiral shape due to a hydrogen bond between an oxygen on one amino acid and hydrogen four amino acids down the chain

Question 11

Beta pleated sheet

Answer 11

• Sections of the peptide chain line up parallel to each other due to hydrogen bonds between one amino acid and another on an adjacent part of the chain

Question 12

Tertiary Structure

Answer 12

• The overall 3D shape of the protein due to different functional groups in the R groups interacting, causing proteins to bond in places
• hydrogen bonds between R group functional groups
• Dipole-dipole interactions between R groups
• Ionic bonds between a negatively charged R group
• Ionic bonds between a negatively charge R group
• Covalent bonds between cysteines R groups 5 atoms (disulfide bridge)
• dispersion forces

Question 13

Quaternary Structure

Answer 13

• Two or more polypeptide chains interact to produce a larger unit

Question 14

Enzymes

Answer 14

• Enzymes are proteins that behave as biological catalysts - lowest activation energy
• Enzymes are very specific in their actions. They assist by holding molecules in the correct orientation or providing acidic or basic sites to catalyse particular steps of a reaction
• Their function is vey dependent on shape - tertiary structure. A change in tempo or pH can denature a protein by interfering with the forces within tertiary structure
• If protein folds differently > no longer correct shape > no longer functions for specific role

Question 15

Zwitterions

Answer 15

The acidic portion donates a H+ to the basic portion which accepts the H+ forming a Zwitterion. Zwitterions are neutral with positively charged side and negatively charged side.

Question 16

Isoelectric points

Answer 16

The pH of a solution at which the net charge of an amino acid is zero

Question 17

low pH solution (below isoelectric point)

Answer 17

• In presence of excess H+, hydrogen ions will attach to negative oxygen making carboxyl side neutral
  When solution pH iOS lower than isoelectric point, zwitterions become positive.

Question 18

high pH solution (above isoelectric point)

Answer 18

• In presence of excess OH-, the hydrogen ion is removed fro, the amino group making the amino side neutral.
  When solution is higher than isoelectric point, zwitterion is negative.