Learn: Cells and Movement Across Membranes

Welcome!Today we'll explore the fascinating topic of cells and movement across membranes. This is an important foundation for understanding how living organisms function. Let's dive in!

What are cells?Cells are the basic building blocks of all living organisms. They are the smallest units that carry out the functions necessary for life, such as energy production and reproduction. Plant and animal cells have different structures suited to their roles.

Structure of Animal and Plant CellsAnimal cells and plant cells have many similarities, but there are some key differences. Both have a cell membrane (controls what enters and leaves the cell), cytoplasm (where chemical reactions occur), and a nucleus (contains genetic material). Plant cells also have a cell wall (provides support), chloroplasts (site of photosynthesis), and a large vacuole (stores substances and helps keep the cell rigid).

Microscope and Cell ObservationA light microscope helps us view cells and their structures. You may have observed onion cells or cheek cells under a microscope during your practicals. Remember to use the microscope carefully to focus on the cell structures clearly.

Movement Across MembranesCells must exchange substances like oxygen, carbon dioxide, and nutrients with their environment. This happens through the cell membrane using processes like diffusion, osmosis, and active transport.

DiffusionDiffusion is the movement of particles from an area of high concentration to low concentration. It is passive, meaning it doesn't require energy. For example, oxygen diffuses into cells, while carbon dioxide diffuses out. It occurs across a partially permeable membrane, such as the cell membrane.

OsmosisOsmosis is the movement of water molecules from a region of high water potential to a region of lower water potential through a selectively permeable membrane. It is a passive process and is vital for maintaining cell structure and function.

Active TransportUnlike diffusion and osmosis, active transport requires energy. It moves substances against their concentration gradient (from low to high concentration). This process often involves proteins in the cell membrane and is used to absorb nutrients like minerals in plant roots.

EnzymesEnzymes are biological catalysts that speed up chemical reactions in cells. They are proteins made of long chains of amino acids, which fold to form a specific shape. This shape gives the enzyme its active site, where the substrate binds. Enzymes work via the 'lock and key' model—only specific substrates fit into their active sites.

Review Time!Great work! You've learned about cells, movement across membranes, and enzymes. Let's test your understanding with a few final questions.