1.2 Proteins

Question 1

Proteome

Answer 1

The entire set of proteins expressed by a genome

Question 2

Why is the proteome larger than the number of genes?

Answer 2

More than one protein can be expressed from a single gene due to alternative RNA splicing

Question 3

Alternative RNA splicing?

Answer 3

Alternative RNA splicing is the removal of introns from the primary transcript. The remaining exons can be either included or removed to allow for several different possible proteins to be produced from one primary transcript

Question 4

What factors can affect the set of proteins expressed by a given cell type?

Answer 4

• Metabolic activity of cell (changes with age, dormancy state etc.)
• Cellular stress (depends on extremes of temperature, pH, toxin exposure etc.)
• Response to signalling molecules such as hormones
• State of health or disease

Question 5

Non-Coding RNA Genes

Answer 5

Genes that don’t code for proteins

Question 6

Examples of non-coding RNA genes

Answer 6

Those that are transcribed to produce tRNA, rRNA and other RNA molecules that control expression of protein coding genes

Question 7

Endoplasmic Reticulum

Answer 7

Forms a network of membrane tubules continuous with the nuclear membrane

Question 8

Golgi Apparatus

Answer 8

Series of flattened membrane discs

Question 9

Lysosomes

Answer 9

Membrane-bound organelles containing a variety of hydrolases that digest proteins, lipids, nucleic acids and carbohydrates

Question 10

Vesicles

Answer 10

Transport materials between membrane compartments

Question 11

Classes of R Group

Answer 11

Basic (positively charged), acidic (negatively charged), polar and hydrophobic

Question 12

Primary Structure

Answer 12

The sequence in which the amino acids are synthesised into the
polypeptide

Question 13

Prosthetic Group

Answer 13

A non-protein unit tightly bound to a protein and necessary for its function

Question 14

What can interactions between R groups be influenced by?

Answer 14

Temperature and pH

Question 15

Ligand

Answer 15

A substance that can bind to a protein

Question 16

What increases the total membrane area in eukaryotes?

Answer 16

System of internal membranes

Question 17

What is synthesised in the ER?

Answer 17

Lipids and Proteins

Question 18

Types of Secondary Structure

Answer 18

Alpha helices, parallel or anti-parallel beta-pleated sheets, or turns

Question 19

What causes secondary structure?

Answer 19

Hydrogen bonding along the backbone of the protein strand

Question 20

Tertiary Structure

Answer 20

Tertiary structure is the folding of the polypeptide, stabilised by interactions between R groups such as LDFs, hydrophobic interactions, hydrogen bonding, disulfide bridges and ionic bonds

Question 21

Where does quaternary structure exist?

Answer 21

Proteins with two or more connected polypeptide subunits

Question 22

Ligand Binding (3 points)

Answer 22

• R groups not involved in protein folding can allow binding to ligands
• Binding sites have complementary shape to ligands
• When binding occurs, the protein changes conformation causing a functional change

Question 23

ATPase

Answer 23

Hydrolyses ATP

Question 24

Cooperativity

Answer 24

Process whereby binding of oxygen to one subunit of haemoglobin alters the affinity of remaining subunits

Question 25

Kinase

Answer 25

Catalyses the transfer of a phosphate group to other proteins

Question 26

Phosphatase

Answer 26

Catalyses the transfer of a phosphate group from other proteins

Question 27

Haemoglobin’s Affinity for Oxygen

Answer 27

Increased with decreased temperature or increased pH
Decreased with increased temperature or decreased pH