2.4 Proteins

Question 1

How are amino acids linked together?

Answer 1

condensation reactions to form polypeptides chains

Question 2

How many types of amino acids are universal to all living organisms?

Answer 2

20 different amino acids are used by the ribosomes to create polypeptides

Question 3

What do the amino acids on ribosomes all contain?

Answer 3

an amine, a carboxyl and a R group

Question 4

How are organisms capable of producing a huge range of possible polypeptides?

Answer 4

amino acids can be linked together in any sequence giving a huge range of possible polypeptides
three bases code for 1 amino acid

Question 5

What is a peptide bond?

Answer 5

the covalent bond between the amino acids

Question 6

What are polypeptides?

Answer 6

long chains of covalently bonded amino acids

Question 7

How can polypeptide chains be broken down?

Answer 7

hydrolysis reactions

Question 8

How are dipeptides formed?

Answer 8

amino acids can be covalently joined together in a condensation reaction to form a dipeptide and water

Question 9

How are peptide bonds formed?

Answer 9

formed between the amine and carboxylic acid groups of adjacent amino acids
- amine group loses a hydrogen atom (H) and the carboxylic acid loses a hydroxyl (OH) – this forms water (H2O)

Question 10

Denaturation

Answer 10

a structural change in a protein that results in loss of its biological properties

Question 11

What causes denaturation in proteins? (two factors)

Answer 11

temperature

pH

Question 12

How does temperature cause denaturation?

Answer 12

high levels of thermal enrgy may disrupt the hydrogen bonds that hold the proteins together
when the bonds are broken the protein will begin to unfold and lose its capacity to function as needed

Question 13

How does pH cause denaturation?

Answer 13

changing the pH will change the charge of the protein, which in turn will alter the protein solubility and overall shape

Question 14

Gene

Answer 14

a sequence of DNA which encodes a polypeptide sequence - three bases of the gene is needed to code for each amino acid in polypeptide

Question 15

What are the functions of protein?

Answer 15

catalysis
muscle contraction
tensile strengthening
blood clotting 
membrane transport

Question 16

What are the two three-dimensional conformations of a protein?

Answer 16

globular proteins

fibrous proteins

Question 17

What are the six examples of proteins? What is each of its function?

Answer 17

Rubisco: enzyme with an active site that catalyses the photosynthesis reactions which fixes carbon dioxide in the atmosphere, providing all the carbon needed by living organisms to make sugars and other carbon compounds
Insulin: hormone that is carried dissolved in the blood and binds specifically to insulin receptors reversibly in the cell membranes, causing the cell to absorb glucose and lower the blood glucose concentration
Immunoglobulin: antibodies that bind to antigens on pathogens, each with a different type of binding site, allowing specific immunity against many diseases
Rhodopsin: pigment that makes the rod cells of the retina light-sensitive; the rod cell sends a nerve impulse to the brain when retinal absorbs a photon of light
Collagen: structural protein with three polypeptides to form a rope-like conformation; used in skin to prevent tearing in bones to prevent fractures, and in tendons and ligaments to give tensile strength
Spider silk: structural protein used to make webs for catching preys; has very high tensile strength and becomes stronger when it’s stretched which resists breakage

Question 18

What are proteomes?

Answer 18

All of the proteins produced by a cell, tissue, or an organism
Proteome of each individual is unique because different cells make different proteins, and small differences in the amino acid sequence of proteins
Proteome reveals what is actually happening in the organism