Cell Structure and Function

Question 1

Structure of rER

Answer 1

1. Consists of networks of sheets (flattened cisternae)
2. Has ribosomes on its surface (gives the rER is ‘rough’ surface)
3. Continuous with outer membrane of the nuclear envelope

Question 2

Roles of rER

Answer 2

1. Transport proteins synthesised by ribosomes on its surface to Golgi body via vesicles
2. Modifies proteins via glycosylation in the ER lumen

Question 3

Structure of smooth ER

Answer 3

1. Consists of networks of tubules
2. Lacks ribosomes on its surface

Question 4

Roles of smooth ER

Answer 4

1. Synthesise lipids and carbohydrates
2. Detoxifies drugs and poisons (thus abundant in liver)

Question 5

Roles of Golgi body

Answer 5

1. Products of sER and rER are further modified, sorted and packaged in the Golgi body
2. Formation of lysosomes (lysosomes contains hydrolytic enzymes)
3. Synthesises polysaccharides
4. Protein modification includes phosphorylation or glycosylation
5. Phosphorylation activates/deactivates the protein while glycosylation targets the proteins for association with membranes

Question 6

Structure and role of mitochondria

Answer 6

1. Double membrane structure
2. Highly folded, giving rise to infoldings called cristae, which increases surface area, allowing more proteins involved in aerobic respiration and ATP synthesis to be embedded
3. Site of aerobic respiration for ATP synthesis

Question 7

Cell Theory

Answer 7

1. Cells are the smallest unit of life
2. All cells come from pre-existing cells
3. All living things are made up of cells

Question 8

Explain the role of the Golgi body and its link to the rough endoplasmic reticulum

Answer 8

1. The cis face of the Golgi body receives transport vesicles containing newly synthesised proteins from the rER
2. Membrane of transport vesicle fuses with membrane of cisternae at cis face of Golgi body, emptying its contents into the cisternal space for further modification, sorting, packaging and transportation of protein in the Golgi body
3. Protein modification includes phosphorylation/glycosylation. Phosphorylotion activates/deactivates protein. Glycosylation targets proteins for assocation with the membrane
4. After protein modification, matured proteins are packaged an sorted into secretory vesicles or lysosomes at the trans face, before being transported to other parts of the cell or out of the cell
5. Hydrolytic enzymes are sorted and packaged into secretory vesicles which bud off from the cisternae at the trans face of the Golgi body and forms lysosomes
6. Secretory vesicles buds off from cisternae at trans face of Golgi body and proteins are secreted out of the cell via exocytosis