Cellular ultrastructure and function

Cellular ultrastructure and function

Cellular Ultrastructure Overview

• Every cell consists of various subcellular components, also called organelles, each with a specific role to play in the functioning of the cell.
• Each organelle is separated by membranes and they together make up the intricate cellular ultrastructure.
• This structure is visible through the use of electron microscopy.

Cell Membrane

• The cell membrane (plasma membrane) is a flexible yet firm barrier that encloses the cell.
• It provides protection and maintains the cell’s integrity by controlling the passage of substances into and out of the cell.
• The cell membrane is made up of a phospholipid bilayer with embedded proteins, glycoproteins and cholesterol.

Nucleus

• The nucleus is the control centre of the cell and contains the cell’s genetic material, DNA.
• It regulates cell activities such as growth, metabolism, protein synthesis and cell division.
• The nucleus is surrounded by a nuclear envelope that has nuclear pores for the transport of molecules across it.

Cytoplasm

• The cytoplasm is the watery substance in which all the organelles of the cell are suspended.
• It houses the metabolic machinery for the cell, where most of the cell’s metabolic reactions such as glycolysis occur.

Mitochondria

• Mitochondria are the primary sites of cellular respiration and hence are often referred to as the powerhouses of the cell.
• They are responsible for producing ATP, the cell’s energy currency which drives many cellular processes.

Rough Endoplasmic Reticulum

• The rough endoplasmic reticulum (RER) is characterised by ribosomes on its surface, leading to the ‘rough’ appearance.
• It plays a critical role in the synthesis and packaging of proteins.

Smooth Endoplasmic Reticulum

• The smooth endoplasmic reticulum (SER) lacks the ribosomes that give the RER its characteristic appearance.
• SER is involved in lipid synthesis, detoxification of harmful substances and calcium storage in muscle cells.

Golgi Apparatus

• The Golgi apparatus processes, sorts and packages proteins and lipids transported from the endoplasmic reticulum.
• Packed proteins and lipids are then transported in vesicles to their destinations, either inside or outside the cell.

Lysosomes

• Lysosomes serve as the cell’s digestive system, containing enzymes to break down waste materials and cellular debris.
• They can also destroy harmful bacteria, viruses and even the cell itself in a process known as autolysis.

Ribosomes

• Ribosomes are small, spherical structures where proteins are made (protein synthesis).
• They can be found free in the cytoplasm or attached to the RER.

Centrioles

• Centrioles play a key role during cell division, where they assist in the formation of the spindle fibres that separate the chromosomes.
• They are usually found near the nucleus.