CORE IDEA 1

Question 1

Role of nuclear envelope in the synthesis of proteins

Answer 1

• Has nuclear pores which allow transport of mRNA from nucleus to ribosomes in cytoplasm and for enzymes to move from cytoplasm into the nucleus

Question 2

How are peptides present in the cisternae of of the rER secreted out of the cell

Answer 2

• Transport vesicles containing peptides bud off from rER
• Vesicles fuse with cis face of golgi apparatus
• Secretory vesicles bud off from trans face of Golgi apparatus
• Directed to cell surface membrane by micro tubules
• Where vesicle membrane fuses with CSM, releasing contents by exocytosis

Question 3

Differentiate between stem cells and somatic cells

Answer 3

• Stem cells are unspecialised whereas somatic cells are specialised cells
• Stem cells are capable of giving rise to differentiated cells whereas somatic cells are already differentiated
• cells from inner cell mass are able to give rise to specialised cells like blood cells

Question 4

Identify two classes of stem cells and account for their separate classification

Answer 4

• Fertilised egg are zygotic stem cells and inner cell mass of the blastocyst are embryonic stem cells
• Classification are based on their potency level
• Zygotic stem cells are totipotent, can give rise to all types of cells to form the whole organism
• Embryonic stem cells are pluripotent, can give rise to almost all types of cells but not the whole organism