Organelles in the Cell: Compartmentalization

Question 1

State what the plasma membrane is made up of.

Answer 1

They consist of 3 parts: the nuclei, cytoplasm, and the (plasma) membrane.

Question 2

Explain the structure of the plasma membrane.

Answer 2

The plasma membrane is a bilayer made up of phospholipids, which is fluid at body temperature. Each phospholipid is comprised of 2 parts: the hydrophilic head, and the hydrophobic tail. When both layers are put together, the hydrophilic heads point towards the outside, and the hydrophilic tails stay inside. This occurs due to the emergent properties which arise, since the cells reside in an aqueous solution (extracellular fluid) and contain a watery solution inside of them (cytoplasm). Though forming the bilayer, it ensures the hydrophilic heads are in contact with the solution, while protecting the hydrophobic tails on the inside. Several proteins also float within the bilayer.

Question 3

List the functions of the plasma membrane.

Answer 3

It helps with:

• Ion and nutrient transport
• Recognition of environmental signals
• Cell-cell and cell-extracellular matrix adhesions

Question 4

List 3 associated pathologies with the plasma membrane.

Answer 4

• Lactose intolerance
• Malabsorption
• Cystic fibrosis

Question 5

List the special properties of the biological membranes.

Answer 5

• Maintains a unique environment inside the cell
• Creates compartments within the cell under specific conditions
• The plasma membrane interacts with the extracellular matrix
• The plasma membrane interacts with other cells

Question 6

State and explain the functions of the organelles within the nucleus.

Answer 6

The DNA contains hereditary material which regulates protein synthesis.
Nuclear pores control traffic to and from the nucleus.
Nucleolus is the production site of rRNA.
Chromatin is comprised of DNA and histones. This can further be organized into euchromatin which is actively transcribing DNA (and is pale), and heterochromatin which is “resting” (and stains quite dark).

Question 7

Describe the structure and explain the function of the nucleopore.

Answer 7

The nucleopore is essentially channels through the nuclear envelope. It helps:

• Regulate the exchange of molecules between the nucleus and cytoplasm.
• Traffic proteins and RNA.
• Establish the internal composition of nucleus.
• Play a critical role in regulating gene expression.

Question 8

State the function and pathologies of the nucleus.

Answer 8

Function:
- Storage and use of the genome
- Controlled by transcription factors
Associated Pathologies:
- Inherited genetic diseases
- Environmentally induced mutations

Question 9

List the membranous organelles

Answer 9

• Mitochrondria
• Rough ER
• Smooth ER
• Golgi Apparatus
• Endosomes
• Lysosomes
• Peroxisomes
• Proteosomes
• Transport Vesicles

Question 10

List non-membranous organelles

Answer 10

• Microtubules
• Microfilaments
• Intermediate Filaments
• Centrioles
• Ribosomes

Question 11

Describe the structure of mitochondria.

Answer 11

Generally an oval or sausage shaped in living cells, which consists of 2 layers - the (double) outer membrane, and the smooth (inner) membrane which fold to form cristae. It has 2 compartments, which is the outer compartment and the inner matrix.

Question 12

State the function and pathologies of mitochondria.

Answer 12

Function:
- Aerobic energy supply (oxidative phosphorylation)
- Has its own DNA
Associated pathologies:
- Mitochrondrial myopathies
- Myoclonic epilepsy and ragged-red fibres
- MELAS
- KSS