CB27 Secretion

Question 1

Explain the essential mechanisms of secretion & excretion

Answer 1

Secretion - movement of material useful to the organism from one compartment to another

Excretion - movement of material from the organism to exterior

Question 2

Describe the general features of exocytosis

Answer 2

Proteins destined for secretion, mRNA-ribosome complex docks to the rough endoplasmic reticulum. The protein is conveyed into the Golgi apparatus for modification.

During exocytosis the secretary vesicle fuses with cell membrane & releases it’s contents into extracellular matrix.

Regulated secretion - only released when given a signal
Constitutive secretion - continuously released

Question 3

Compare regulated & constitutive secretion

Answer 3

Regulated secretion - only released when given a signal
Constitutive secretion - continuously released

Question 4

Describe the three different processes of endocytosis

Answer 4

Phagocytosis - engulfing large particles

Pinocytosis - engulfing liquid

Receptor mediated endocytosis - material must bind to specific receptors on the cell to be absorbed

Question 5

Name examples of the different compounds secreted by cells

Answer 5

• Signalling compounds (e.g. Hormones, neurotransmitters)
• other active compounds (e.g. Lysozymes)
• protective barrier secretions (e.g. Mucus, serous fluid, sebum)
• extra cellular matrix & plasma membrane molecules (e.g. Membrane bound enzymes)