Polysaccarides & Lipids

Question 1

1950s - Beadle & Tatum - early ideas on gene expression

Answer 1

• Believed that 1 gene = 1 product due to experiments with fungus neurospores
• concept kept for decades*
• Later saw nematode (C. elegans) = 18000 genes vs Human genome = 26000 to 70000

Found it’s not the number of genes you have - it’s what you do with them (same w/ protein)

Question 2

Process of Gene to protein

-Glycosylation

Answer 2

1 gene -> protein -> MODIFICATION -> multiple forms of protein w/ different functions

*Modification; Glycosylation (the addition of polysaccharide chains to proteins)

Question 3

2 main forms of sugars

Answer 3

1. Hexoses (6 C form)
   
   • different groups added to carbon to give different sugars (i.e. glucose, fructose, glactose mannose)
2. Furanoses (5 C form)
   
   • i.e. pentose ring (nucleotides)

Question 4

How are polysaccharides made?

Answer 4

• Made when simple sugars are joined together
  
  • are able to join in different ways to make complicated branch structures/arrays

e.g. polysaccharides w/ branch structures found in plant cell wall are very complex & strong (i.e. chitin, glycans, starch)

Question 5

Where protein synthesis & glycosylation occurs

-glycosylation in different species

Answer 5

Proteins (synthesised in cytoplasm) -> some go to ER -> Golgi apparatus -> different possible outcomes/location

• Glycolysation starts in E.R. and continues in golgi apparatus
• The glycosylation pattern is different among species (Activity of protein often relies on glycolation pattern)

Question 6

Example of protein; Notch

Answer 6

• Notch protein has a domain inside & outside cell - is involved in cell-cell communication
  
  • outer domain interacts w/ jaggered protein on other cells
  • intracellular domain breaks off & goes to nucleus to affect gene epression (activates expression of genes in nucleus)
• Notch 1 contains series of ECF repeats (are proteins on outer domain) & these repeats are glyosylated w/ different sidechains
  
  • side chains & protein can create v. complex structure

Question 7

Importance of Glycosylation (in CNS)

-Gycoforms

Answer 7

-Critical for development of nervous system

Glycoforms: different forms of glycosylated proteins

-outer surface of eukaryotic cells coated by polysaccharide chains - helps communication b/w cells via things that bind to them - can change protein expression w/in cells

Question 8

Lipids

• what they are a major component of
• examples
• role of cholesterol in lipid bilayer

Answer 8

• principle component of membranes (regulates flow of materials into & out of cell
  e. g. cortisol, testosterone
  
  • those w/ ring structure (i.e. testosterone) function as hormones or messengers - important in development
• Cholesterol provides order to lipid bilayer