B1.2 (proteins) (from SME, 2.3.1, AI)

Question 1

What are proteins made of?

Answer 1

Proteins are polymers made of monomers called amino acids

Question 2

What determines the shape and function of a protein?

Answer 2

The sequence, type, and number of amino acids

Question 3

List five types of proteins found in cells.

Answer 3

• Enzymes
• Cell membrane proteins
• Hormones
• Immunoproteins
• Transport proteins
• Structural proteins
• Contractile proteins

Question 4

Why are proteins crucial for life?

Answer 4

All genes code for proteins, making all reactions necessary for life dependent on proteins

Question 5

What are the building blocks of polypeptides?

Answer 5

Amino acids

Question 6

How many amino acids are commonly found in polypeptides?

Answer 6

20 amino acids

Question 7

What is the general structure of an amino acid?

Answer 7

A central carbon atom bonded to an amine group, a carboxylic acid group, a hydrogen atom, and an R group

Question 8

What is a peptide bond?

Answer 8

A bond formed when a hydroxyl group is lost from one amino acid and a hydrogen atom is lost from another

Question 9

What reaction occurs during the formation of a peptide bond?

Answer 9

Condensation reaction

Question 10

What are dipeptides and polypeptides?

Answer 10

Dipeptides are formed by two amino acids; polypeptides are formed by three or more amino acids

Question 11

What happens during hydrolysis reactions?

Answer 11

Water is added to break peptide bonds, resulting in amino acids

Question 12

True or False: All organisms use the same 20 amino acids.

Answer 12

True

Question 13

What are essential amino acids?

Answer 13

Amino acids that must be obtained through the diet

Question 14

How many amino acids can humans synthesize naturally?

Answer 14

11 amino acids

Question 15

Fill in the blank: The amino acids are usually abbreviated to _______.

Answer 15

[three letters]

Question 16

What is the significance of the R group in amino acids?

Answer 16

It determines the properties of each amino acid

Question 17

What are the hypotheses regarding the use of only 20 amino acids in proteins?

Answer 17

• Only these 20 were available at the origins of life
• They are diverse enough for wide protein functions
• All organisms share a common ancestor

Question 18

What is the Central Dogma of molecular biology?

Answer 18

All genes code for proteins, and proteins determine an organism’s characteristics

Question 19

How many possible combinations exist for a polypeptide chain of 50 amino acids?

Answer 19

20^50
1.13 x 10^65 combinations

Question 20

What is required to code for each amino acid in a polypeptide?

Answer 20

Three consecutive DNA bases

Question 21

What is the genetic code?

Answer 21

The sequence of DNA bases that codes for the amino acid sequence of polypeptides

Question 22

What is the average length of a protein?

Answer 22

300 amino acids

Question 23

Secondary protein structures are normally stabilised by hydrogen bonds created between:

Answer 23

–NH groups of peptide bonds and –C=O groups of other peptide bonds found in the same chain.

Question 24

descriptions of primary, secondary and terinart structure of peoteins

Answer 24

The primary structure describes a chain of amino acids

the secondary structure: folding into an alpha helix or beta pleated sheet,

Tertiary structure: folded chains can further coil up and create three-dimensional structures, by the R groups interacting

Quarternary: the arrangement of two or more polypeptide chains to form functional proteins.2

Question 25

r groups can be

Answer 25

polar or non polar

Question 26

fibrous proteins are insoluble because

Answer 26

they have non polar aa on the surface