Protein Structure and Function

Question 1

What are the four levels of protein structure?

Answer 1

1) primary structure
- linear amino acid chains - sequence determined via genetics
- held together by peptide bonds
2) secondary structure
- can be alpha helix or beta sheets
- fibrilar proteins
3) tertiary structure
- multiple secondary structures
- globular proteins - myoglobin
4) quartenary structure
- multiple subunits of tertiary structures
- membrane proteins
- haemoglobin

Question 2

What are the classifications of proteins according to function?

Answer 2

> enzymes: pepsin, catalase, lipase
regulatory proteins: transcription factors
signalling proteins: hormones, growth factors
transport proteins: haemoglobin, albumin
Structural proteins:: actin, tubulin, collagen
protective proteins: chaperones, antibodies

Question 3

describe an anabolic reaction

Answer 3

> associated with growth, require energy, go from smaller molecules to more ordered molecules, endergonic

Question 4

describe catabolic reactions

Answer 4

> associated with the release of energy and energy production.
going from an ordered system to a disordered system.
breaking down larger molecules into smaller units, with the bonds being broken creating energy.
exergonic

Question 5

What is a co enzyme?

Answer 5

> a substance that works with an enzyme to initiate or aid the function of the enzyme (also known as energy carriers)
Acetyl CoA
NAD+/NADH
FAD+/ FADH2

Question 6

What is a cofactor?

Answer 6

> basically an inorganic co enzyme

• usually takes part in the reaction and is altered
• often derived from a vitamin
• metal ions also used by enzymes for catalysis
• this is why vitamins and minerals are important in diet - as cofactors

Question 7

describe enzymes and their function in the body

Answer 7

> catalyse virtually all biological reactions
usually proteins and highly efficient
characterised by their high SPECIFICITY for their substrate and the REACTION that is catalysed
- largely based on the structure of its active site to acheive this specificity
reduce the activation energy of a reaction to proceed
- involved in digestion, blood clotting, buffering of acid in the body etc.
- all affected by pH and cell stress - important to maintain internal conditions

Question 8

how are enzymes regulated?

Answer 8

> activation or inhibition can work via:
- allosteric regulation -> change in shape
- inhibitors binding to the active site
- phosphorylation
also modulated by temp, ph, substrate concentration and chemical inhibitors

Question 9

what are the different types of chemical enzyme inhibitors?

Answer 9

> Competitive: binds to the active site and competes with the substrate
non-competitive binds to a different site at the enzyme and causes a conformational change that blocks its activity
- exploited in drug design

Question 10

What are some examples of diseases cause by abnormal/dysfunctional proteins?

Answer 10

1) a deficiency of normal protein - a decreased synthesis
2) production of an abnormal protein due to mutation
3) destabilisation of proteins due to cellular stress (increased temp, ph etc)
- a loss of structure causes a loss of function
- an elevated level of certain enzymes can be indicative of pathology