Lecture one - Proteins and their classification

Question 1

Proteins facts

Answer 1

• ¾ of the body solids are proteins
• Various intracellular and extracellular functions
  (structural proteins, enzymes, carrier proteins, channels etc)
• Amino acids as principal constituents providing a framework for various functions

Question 2

Amino acids-basic backbone
Acid: donating a proton
Base: accepting a proton in water solution

Question 3

Amino acids: highly diverse

Answer 3

• Diverse structure of amino acids –> foundation of protein diversity
• Zwitterions/hybrid ions:
  containing at the same time at a given pH a positively charged (amino-residue) and negatively charged (carboxyl-residue) ion (amphoteric)

Question 4

20 amino acids are coded in the genetic code

Answer 4

Polarity, hydrophobicity, functional groups, charged or uncharged
–> determines functional behavior and interaction

Question 5

Answer 5

Question 6

Branched chain/hydrophobic vs aromatic groups

Question 7

Polar vs charged

Question 8

Sequence determines structure
Structure determines function

Answer 8

Amino acid diversity creates a multitude chemical covalent and non-covalent interactions (polarity, charge, hydrophobicity etc)

Question 9

Amino acids and protein structure:

Answer 9

Interactions determine bond angels (alpha helix vs beta sheet)
Complexity and diversity: product of combination probabilities

Question 10

Answer 10

Question 11

Metabolic functions of proteins

Answer 11

• Structural per se (cell and tissue structure, collagen, tubulin, actin)
• Structural as platform for reactions (ribosomal protein, mitochondrial protein)
• Catalytic enzymes, lowering activation energy (kinases, aminases, dehydrogenases)
• Energy production and transfer: acting as molecular motors (actin/myosin, dynein, kinesin)
  [Actin-myosin cross-bridging]
• Regulatory: hormones, signaling molecules, transcription factors, kinases, phosphatases, caspases
• Transport: hemoglobin, ferritin, thyroid-binding globulin
• Membrane structures: channels, pores, hormone receptors, pumps, carriers
• Immune system: antibodies

Question 12

Classification of proteins

Answer 12

• According to size:
  *up to 100 Amino acids: peptide
  
  • > 100: protein
  • <10: oligopeptide
• According to composition:
  *conjugated proteins: glycoproteins, lipoproteins, nucleoproteins
• According to form:
  fibrillary (collagenes, ceratines, elastines, less soluble) vs globular (many enzymes, plasmaproteins, haemoglobin, often well water soluble)
• According to families:
  *immunoglobulines

Question 13

Molecular weight-electrophoretic mobility

Answer 13

Question 14

Western Blot example

Question 15

Fibrillary/fibrous (non-soluble)

Answer 15

Highly complex proteins
Peptide chains elongated
Parallel bundled held together by cross linkages

Question 16

Collagens:

Answer 16

connective tissue, tendons, cartilage, bone
- The orientation of collagen bundles provides functional/structural stability AND flexibility

Question 17

Elastins:

Answer 17

elastic fibers of arteries, tendons, lung

Question 18

Keratins:

Answer 18

structural proteins of hair and nails

Question 19

Actin/myosin:

Answer 19

contractile proteins

Question 20

Fibrillary/fibrous (non-soluble). More info

Answer 20

Fibrils are extremely strong, capable of being stretched, then recoil (elastomeric characteristic)

• Elastomeric property: creep, adaptive to a new stretch length or adaptive to a new shorter length (eg scar)

Question 21

Scar:

Answer 21

example for elastomeric properties
Creeping of fibrous proteins in scar tissue can be observed in the progression of obesity