• All living organisms are made up of cells. There are two types of cells: prokaryotic and eukaryotic. Animal and plant cells are both eukaryotic which means they have a distinct nucleus.

• Animal cells and plant cells are similar in many ways, but they have some key differences.

Common components in both animal and plant cells:

• Nucleus: Contains genetic material (DNA) and controls activities of the cell.
• Cytoplasm: A gel-like substance where most of the cellular activities occur.
• Cell membrane: Controls movement of substances in and out of the cell.
• Mitochondria: Organelles where energy is produced during respiration.
• Ribosomes: The site where proteins are made.

Structures unique to plant cells:

• Cell wall: A rigid layer mainly composed of cellulose that provides support and shape.
• Chloroplasts: Contains chlorophyll, the green substance used to carry out photosynthesis.
• Vacuole: A large central sac filled with cell sap to maintain pressure within the plant cell.

Structures unique to animal cells:

• Centrioles: These help with cell division in animal cells.

• Lysosomes: Sac-like organelles that contain enzymes that can break down waste materials and cellular debris.

• There is a concept known as the "specialisation of cells" where cells have developed certain characteristics to perform a specific function. For example, nerve cells in animals and root hair cells in plants.

• In multicellular organisms such as animals and plants, cells organise into tissues, organs, and systems. For example, muscle tissue in animals and xylem in plants.

In the context of Cell Movement Across Membranes

• The cell membrane is selectively permeable, meaning it controls which substances can pass through it.

• Some substances move across the cell membrane through diffusion. This is the movement of particles from an area of high concentration to an area of low concentration until they are evenly distributed.

• Osmosis is a specific type of diffusion involving water moves from areas of high water concentration (low solute concentration) to areas of low water concentration (high solute concentration) across a semi-permeable membrane.

• Active transport is the process by which substances are moved against a concentration gradient (from an area of low concentration to an area of high concentration) with the use of energy produced by respiration. This process is crucial for absorbing nutrients in the gut and ions from the soil in plants.

Remember, understanding the structure and functions of cells is the central part of Biology. Therefore, it's important to familiarise yourself with these concepts and be able to explain their importance.