Organelles and Cell Theory

Question 1

Relate structure to function of lysosomes.

Answer 1

Small spherical vesicles that contain hydrolytic enzymes surrounded by single membrane, contents are acidic and enzymes have low optimum pH
* Fuse with vesicles formed from endocytosis to digest materials to be absorbed into the cell
* Fuse with worn out organelles for degradation and recycling of material
* Trigger self digestion of cell after cell death

Question 2

Relate structure to function of Golgi apparatus.

Answer 2

Strcture:
* GA consists of a stack of flattened membrane-bound sacs: cisternae
* Forming/cis face is where transport vesicles from the ER fuse to
* Maturing/trans face is where budding of secretory vesicles occurs

Function:
* GA chemically modify, sort and package the proteins or lipids made in rER and sER
* Modifications: Glycosylation, phosphorylation
* Modified proteins sorted, packaged into secretory vesicles which bud off from
the maturing/trans face.
* Proteins inserted into cell membrane or released out of the cell via exocytosis.
* Vesicles from GA can fuse with each other to form lysosomes.

Question 3

Relate structure to function of rER.

Answer 3

Structure:
* a network of flattened membrane-bound sacs: cisternae
* ribosomes attached on cytoplasmic site

Function:
* site of protein synthesis and transport.
* proteins synthesised by ribosomes attached –> either inserted into cell membrane, secreted out of cell or packaged into lysosomes.
* Proteins synthesised are folded into their specific shapes in the ER lumen.
* Proteins packaged into transport vesicles, bud off rER and move to other parts of the cell

Question 4

Relate structure to function of sER.

Question 5

Relate structure to function of nucleus.

Answer 5

Structure:
* enclosed by double membrane
* outer membrane continuous with ERs
* nuclear pores on nuclear envelope –> function as channels for regulation of
movement of molecules between nucleus and cytoplasm.

Function:
* stores hereditary material (DNA) –> essential to provide continuity of genetic information to next generation of cells.
* DNA contains genes –> templates for protein synthesis (e.g. enzymes).
* controls and directs cell activities by regulating gene expression and protein
synthesis.

Question 6

List the features of the structure of mitochondria.

Answer 6

• Bounded by double membrane
• Outer membrane: smooth, continuous boundary
• Inner membrane: extensively folded into cristae
• Matrix: contains circular DNA and 70S ribosomes

Question 7

What is the function of mitochondria?

Answer 7

Site of cellular respiration to produce ATP.

Question 8

List the features of the structure of chloroplast.

Answer 8

• Bounded by double membrane
• Third membrane forms thylakoid
• Intermembrane space between two membranes
• Stroma: contains circular DNA and 70S ribosomes, starch grains
• Thylakoid lumen

Question 9

What is the function of chloroplast?

Answer 9

Site of photosynthesis.

Question 10

Outline the cell theory.

Answer 10

1. All living organisms are made up of cells.
2. A cell is the most basic unit of life.
3. Cells arise from pre-existing cells.