Unit 1: Identifying Cell Structures & Functions

Organelles Visible in Cells (Except Prokaryotes)

When observed at higher magnification (e.g., electron microscope), several organelles can be identified in the cytoplasm:

1. Mitochondria

• Function: Known as the "powerhouses of the cell."
• Role: Responsible for cellular respiration, breaking down glucose to release energy as ATP (adenosine triphosphate).

2. Ribosomes

• Location: Free within the cytoplasm or attached to the Endoplasmic Reticulum.
• Function: Sites of protein synthesis, translating genetic code from mRNA into amino acid sequences.

3. Endoplasmic Reticulum (ER)

• Rough ER (RER): Involved in protein synthesis and modification; appears rough due to ribosomes.
• Smooth ER (SER): Lacks ribosomes; involved in lipid synthesis, detoxification, and calcium storage.

4. Vesicles

• Function: Involved in transport, storage, and digestion within cells.
• Role: Varies depending on type and content.

Calculating Cell Magnification

Understanding Magnification

• Importance: Vital for observing tiny structures like cells.

Formula

• Magnification: Calculated as Image Size / Actual Size.

Example

• Image Size: 5 mm
• Actual Size: 0.005 mm
• Calculation: Magnification = 5 mm / 0.005 mm = 1000x

Specialised Cells in Plants and Animals

Specialised cells develop from generic cells via differentiation to perform specific functions.

Specialised Cells in Plants

1. Root Hair Cells

   • Function: Absorb water and minerals from the soil.
   • Specialisations: Long extensions, large vacuole.

2. Ciliated Cells

   • Location: Airways and oviducts.
   • Function: Move mucus or eggs using cilia.

3. Xylem Cells

   • Function: Transport water and minerals.
   • Specialisations: Thick walls, lignin deposits, hollow tubes.

4. Phloem Cells

   • Function: Transport sugars.
   • Specialisations: Sieve tube elements, companion cells.

5. Guard Cells

   • Function: Control stomata opening/closing for gas exchange.
   • Specialisations: Uneven cell walls.

6. Palisade Mesophyll Cells

   • Function: Photosynthesis.
   • Specialisations: Numerous chloroplasts, columnar shape.

Specialised Cells in Animals

1. Red Blood Cells

   • Function: Transport oxygen and carbon dioxide.
   • Specialisations: Biconcave shape, no nucleus.

2. Nerve Cells (Neurons)

   • Function: Transmit electrical signals.
   • Specialisations: Long axon, dendrites, synapses.

3. Muscle Cells

   • Function: Contract and relax for movement.
   • Specialisations: Contractile proteins, different types (skeletal, smooth, cardiac).

4. Sperm Cells

   • Function: Fertilize an egg cell.
   • Specialisations: Flagellum, acrosome with enzymes.

5. Egg Cells

   • Function: Support early embryo development.
   • Specialisations: Large size, haploid nucleus.

Conclusion

Specialised cells are crucial for the functioning of multicellular organisms, allowing specific tasks and contributing to the organism's health and well-being.