iGCSE Biology (Triple) OxfordAQA

Organisation: Cell Structure

Basics of Cell Structure

• All living organisms are made up of cells, which are often called the building blocks of life.
• Cells vary greatly in terms of their shape and function, but all cells share common characteristics.
• Cells can be categorised into two primary types: prokaryotes and eukaryotes.
• Prokaryotic cells, such as bacteria, have no discernible nucleus and contain fewer organelles than eukaryotes.
• Eukaryotic cells, found in plants, animals, fungi, and protists, have a well-defined nucleus and are more complex than prokaryotes.

Components of Eukaryotic Cells

• Each eukaryotic cell has a nucleus that contains the genetic information (DNA) and is responsible for controlling cell activity.
• Cytoplasm is the cellular material outside the nucleus in which the organelles are located.
• Mitochondria are the powerhouses of the cell, generating energy for cell activities.
• Ribosomes are where proteins are synthesised as per the instructions from DNA.
• Cell membrane is a dynamic structure that controls the movement of substances in and out of the cell.

Plant Cell Structure

• Plant cells contain all the eukaryotic components but have a few additional structures.
• Chloroplasts are involved in photosynthesis, converting sunlight into glucose for energy.
• The cell wall, made primarily of cellulose, provides structure and support to the plant.
• A large vacuole, filled with cell sap, helps to maintain the cell’s shape.

Animal Cell Structure

• Animal cells contain typical eukaryotic components but lack certain features found in plant cells, such as chloroplasts, cell walls, and large vacuoles.
• Animal cells often contain small vacuoles which facilitate storage and transport processes within the cell.

Microscopy in Cell Study

• Microscopy has been pivotal in the study of cell structure and function.
• Light microscopy allows for the visualisation of cell structures like the cell membrane, nucleus and cytoplasm.
• Electron microscopy offers a much higher resolution and can reveal much smaller structures such as ribosomes and the detailed structure of the cell membrane.

Specialisation in Cells

• Cells often specialise to perform specific functions. This concept is referred to as cell differentiation.
• Some examples of specialised cells include nerve cells, muscle cells, sperm cells, and root hair cells. They have unique structures that enable them to fulfil their specific roles.

Importance of Cell Organisation

• From tissue formation to complex organisms, cells organise at various levels.
• Cells of a similar type group together to form tissues, with a common function.
• Multiple tissues come together to form organs, such as the heart or lungs.
• Multiple organs work together to form organ systems, such as the digestive system or cardiovascular system.

Remember, revisiting each of the points and understanding how they work together will ensure a strong grasp of cell structure and organisation in your biology revision.