Learn: Cells and Movement Across Membranes

Welcome!Today we'll explore cells and how substances move across membranes. This is an important topic in biology, as cells are the basic building blocks of all living organisms. Let's dive in!

What are cells?Cells are the smallest structural and functional units of all living organisms. They come in two main types: animal cells and plant cells. These cells carry out essential life processes and contain specialised structures called organelles.

Parts of a cellCells have different parts with specific functions:Nucleus: Contains genetic material and controls cell activities.Cell membrane: Controls what enters and leaves the cell.Cytoplasm: Jelly-like substance where chemical reactions occur.Mitochondria: Release energy through respiration.Chloroplasts: Found in plant cells, where photosynthesis happens.Cell wall: Found in plant cells, gives strength and support.Vacuole: Found in plant cells, stores substances and helps maintain structure.

Levels of biological organisationLiving organisms are organised into several levels:Tissue: Groups of similar cells that work together.Organ: Made of tissues that perform specific functions.Organ system: Groups of organs working together.Organism: A living being made up of organ systems.

Movement across membranesSubstances move in and out of cells through the cell membrane. This happens via three main processes:Diffusion: Movement of particles from high to low concentration.Osmosis: Movement of water across a selectively permeable membrane.Active transport: Movement of substances against a concentration gradient, requiring energy.

DiffusionDiffusion is the passive movement of particles from an area of high to low concentration. For example, oxygen diffuses into cells for respiration. This process does not require energy.

OsmosisOsmosis is the movement of water across a selectively permeable membrane. Water moves from an area of high water potential to low water potential. This helps cells maintain balance.

Active transportActive transport moves substances against their concentration gradient (from low to high concentration). This process requires energy, which is provided by mitochondria in the form of ATP.

Review Time!Great work! You've learned about cells, their parts, and how substances move across membranes. Now let's test your understanding with some review questions.