1.2 Proteins

Question 1

Define the term proteome

Answer 1

The entire set of proteins expressed by a genome

Question 2

Why is the proteome larger than the number of genes in a cell?

Answer 2

Post translational modification and alternative RNA splicing.

Question 3

State 3 functions of non-coding RNAs.

Answer 3

rRNA, tRNA and microRNA

Question 4

Explain why the proteome changes within a cell.

Answer 4

Metabolic activity, cellular stress or disease.

Question 5

Why do cells have a system of internal membranes?

Answer 5

To increase surface area for chemical reactions to happen.

Question 6

Where are cytosolic proteins made?

Answer 6

The cytoplasm.

Question 7

State the function of smooth ER

Answer 7

Lipid synthesis.

Question 8

State the function of the lysosome.

Answer 8

An organelle that contains a variety of hydrolyses that digest proteins, lipids and carbohydrates.

Question 9

Where are the signal sequences within the cell and what is their function?

Answer 9

A short stretch of amino acid that determines the location of the protein.

Question 10

State the type of bond that holds amino acids together.

Answer 10

Peptide bond.

Question 11

Discuss the chemical nature of a basic amino acid.

Answer 11

Positively charged r-group, and hydrophilic in nature.

Question 12

Discuss the chemical nature of an acidic amino acid.

Answer 12

Negativley charged r-group, and hydrophilic in nature.

Question 13

Discuss the chemical nature of a polar amino acid.

Answer 13

Polar in nature (hydroxyl group), and hydrophilic in nature.

Question 14

Discuss the chemical nature of a non-polar amino acid.

Answer 14

Non-polar in nature (Hydrocarbon), and hydrophobic in nature.

Question 15

Describe the bonding of a primary protein structure.

Answer 15

Held together by a peptide bond.

Question 16

Describe the bonding of a secondary protein structure.

Answer 16

Secondary structures are either; a helix or a beta sheeted plate.
a helix are held together by a hydrogen at every four amino acids. beta sheeted plate is when different parts of the polypeptide chain run alongside each other

Question 17

Describe the bonding of a tertiary protein structure.

Answer 17

Tertiary structures include disulphide bridges that exist between r-groups which contain sulphur.

Question 18

Describe the bonding of a quaternary protein structure.

Answer 18

Quaternary protein structures include two or more polypeptide subunits , creating a more complex protein. E.g haemoglobin.

Question 19

Name the bond that exists in a disulphide bridge.

Answer 19

Covalent bond.

Question 20

State the main difference between the quaternary structure and tertiary structure.

Answer 20

The number of subunits.

Question 21

Discuss the effect of temperature on r-group interactions.

Answer 21

High temperatures will break the polypeptide chain.

Question 22

Discuss the effect of pH on r-group interactions.

Answer 22

Ionic interactions are lost.

Question 23

Describe a ligand.

Answer 23

A molecule that can bind to a protein.

Question 24

Describe the three examples of ligand binding.

Answer 24

Enzymes, receptors and histones.

Question 25

State the effect of a ligand biding to a protein.

Answer 25

Conformational changes.

Question 26

What is allosteric regulation.

Answer 26

The biding of modulators at spatially distinct sites.

Question 27

What are positive and negative regulators.

Answer 27

Positive regulators increase a proteins affinity for a molecule, where as negative regulator decreases a proteins affinity for a molecule.

Question 28

Discuss positive and negative modulation of ATCase.

Answer 28

ATP functions as a positive modulator, where as CTP functions as a negative modulator.

Question 29

Name bonds that stabilise the tertiary protein structure.

Answer 29

London dispersion, ionic and hydrogen.

Question 30

Define co-operativity.

Answer 30

Co-operativity is when the binding of a ligand to one sub-unit increases the affinity of the remaining units for the ligand.

Question 31

Discuss co-operativity in haemoglobin.

Answer 31

The binding of oxygen to one subunit increases affinity for oxygen in the remaining subunits.