2.1.2 Protein and Inorganic ions

Question 1

What is the primary structure of proteins?

Answer 1

The number and sequence of amino acids in the polypeptide chain.

Question 2

What is the secondary structure of proteins?

Answer 2

The coiling or regular folding of the polypeptide chain, held together by hydrogen bonds.

Question 3

What is the tertiary structure of proteins?

Answer 3

The further folding of the polypeptide chain to form a precise, compact and geometric shape. It is held together by hydrogen bonds, disulfide bonds, ionic interactions and hydrophobic and hydrophilic interactions.

Question 4

What is the quaternary structure of proteins?

Answer 4

Proteins which contain two or more polypeptide chains.

Question 5

What are the monomers of a polypeptide chain called?

Answer 5

Amino acids.

Question 6

What are 2 types of proteins?

Answer 6

Globular proteins and fibrous proteins.

Question 7

What is the shape of a globular protein?

Answer 7

Roughly circular/spherical

Question 8

What is the shape of a fibrous protein?

Answer 8

Long and thin strands

Question 9

What determines the function of a protein?

Answer 9

The shape, so the type and number of amino acids within a polypeptide chain.

Question 10

What is the general structure of an amino acid?

Answer 10

A central carbon atom bonded to an amine group (NH2), a carboxylic acid group (COOH), a hydrogen atom and an R group.

Question 11

What is the covalent bond called that forms between an amino acid?

Answer 11

Peptide bond.

Question 12

How is a peptide bond formed?

Answer 12

A hydroxyl (-OH) is lost from the carboxylic group of one amino acid and a hydrogen atom is lost from the amine group of another amino acid. The remaining carbon atom (with the double-bonded oxygen) from the first amino acid bonds to the nitrogen atom of the second amino acid.

Question 13

What is the reaction called when the bond is formed?

Answer 13

Condensation reaction.

Question 14

What is the primary structure of a polypeptide chain determined by?

Answer 14

The DNA of the cell.

Question 15

What are the 2 types of secondary structures of a protein?

Answer 15

Alpha helix and Beta pleated sheet.

Question 16

how do alpha helix form

Answer 16

the hydrogen bonds form between every fourth peptide bond.

Question 17

how do beta pleated sheet form?

Answer 17

the protein folds so that two parts of the polypeptide chain are parallel to each other enabling hydrogen bonds to form between parallel peptide bonds.

Question 18

What are the additional bonds that can form between the R groups?

Answer 18

Hydrogen bonds, disulfide bonds, ionic bonds and weak hydrophobic interactions.

Question 19

Where do disulfide bonds form?

Answer 19

Between two cysteine R groups as they are the only amino acid with a sulfur atom.

Question 20

Where do ionic bonds form?

Answer 20

Between positively charged and negatively charged R groups.

Question 21

When do hydrogen bonds form?

Answer 21

Between strongly polar R groups.

Question 22

What is the structure of haemoglobin?

Answer 22

conjugated protein with a tertiary structure with 4 polypeptide chains. These chains are globin proteins and all contain a prosthetic haem group. The chains are held together by disulfide bonds and by hydrophobic and hydrophilic interactions.

Question 23

How does the structure of haemoglobin help its function?

Answer 23

The haem groups contain Fe 2+ ions which is able to reversibly combine with oxygen to form oxyhaemoglobin.

Question 24

What type of protein are enzymes?

Answer 24

Globular proteins.

Question 25

describe the test for the presence of proteins

Answer 25

1. add sodium hydroxide to sample
   2.add a few drops of copper (II) sulfate solution to the sample
   this is biuret reagent

Question 26

describe the positive result for protein

Answer 26

blue to lilac

Question 27

describe the strcuture and function of insulin

Answer 27

globular protein, soluble, 2 polypeptide chains held together by disilfide bonds
helps to regulate blood glucose levels

Question 28

describe the structure and function of amyalse

Answer 28

globular protein, single chain of amino acids, 2° structure has both alpha helix and beta pleeted sheets
catalyses the breakdown of starch

Question 29

describe the properties and function of collagen

Answer 29

very strong but flexible, minerals can bind to increase rigidity
found in animal connective tissue

Question 30

describe the properties and function of keratin

Answer 30

can be either flexible or hard and tough
found in external structures of animals, e.g skin, nails

Question 31

describe the properties and function of elastin

Answer 31

elastic
found in elastic connective tissue, e.g skin

Question 32

3 roles of calcium ions

Answer 32

clotting factor
cofactor for many enzymes
involved in transmission of neve impulses and insulin release

Question 33

3 roles of sodium ions

Answer 33

important for generating nerve impulses
muscle contraction
regulating fluid balance

Question 34

4 roles of potassium ions

Answer 34

important fro generating nerve impulses
muscle contraction
regulating fluid balance
activates essential enzymes needed in photosynthesis

Question 35

2 roles of hydrogen ions

Answer 35

affects pH of substances
used in photosynthesis

Question 36

role of ammonium and nitrate ions

Answer 36

source of nitrogen to form amino acids and nucleic acids

Question 37

role of hydrogencarbonate

Answer 37

acts as a buffer to help maintain blood pH

Question 38

3 roles of chloride

Answer 38

‘chloride shift’-helps to maintain pH of bllod during gas exchange
cofactor for amylase
involved in some nerve impulses

Question 39

2 roles of phosphate

Answer 39

involved in photosynthesis and respiration
need for the synthesis of many biological molecules

Question 40

role of hydroxide

Answer 40

affects pH of body