## Animal Cells Rely on Isotonic Environments For Stability [block_0] 1. Animal cells are highly sensitive to their environment because they **lack the structural support of a cell wall**. 2. Water movement across the cell membrane can cause cells to swell, shrink, or remain stable depending on the surrounding solution. ![](https://cdn.sanity.io/images/w7j7fz60/production/2c155fbd6dc6f9862802919dc8ff1c14b4609d38-3000x2000.png) ## Hypotonic Solutions Cause Cells To Swell and Burst [block_5] 1. In a **hypotonic solution**, the surrounding environment has a **lower concentration of solutes** than inside the cell. 2. Water moves **into the cell** by osmosis. 3. **What happens**: The cell swells as water enters, pressure increases, and without a cell wall, the **cell membrane may rupture** (a process called **lysis**). [{"_key":"block_13","_type":"block","asset":null,"children":[{"_key":"54a000352642","_type":"span","markDefs":[],"marks":[],"text":"When "},{"_key":"a8ad052e1e89","_type":"span","markDefs":[],"marks":["strong"],"text":"red blood cells"},{"_key":"68e9bdf09f8f","_type":"span","markDefs":[],"marks":[],"text":" are placed in pure water, they "},{"_key":"747ddcef4be0","_type":"span","markDefs":[],"marks":["strong"],"text":"swell"},{"_key":"a66ff2f95e06","_type":"span","markDefs":[],"marks":[],"text":" and "},{"_key":"3234d801aebf","_type":"span","markDefs":[],"marks":["strong"],"text":"burst"},{"_key":"29f0520dbcdd","_type":"span","markDefs":[],"marks":[],"text":", leaving behind empty membranes called \"red cell ghosts\""}],"markDefs":[],"style":"normal"}] ## Hypertonic Solutions Cause Cells To Shrink and Crenate [block_17] 1. In a **hypertonic solution**, the surrounding environment has a **higher concentration of solutes** than inside the cell. 2. Water moves **out of the cell** by osmosis. 3. **What happens**: The cell loses water and **shrinks**. The cell membrane pulls away from the cytoplasm, creating a wrinkled appearance called **crenation**. [{"_key":"block_27","_type":"block","asset":null,"children":[{"_key":"TYzLq1jkpxBbhvXHi2N4d9","_type":"span","markDefs":[],"marks":[],"text":"Remember: Hypertonic solutions cause cells to shrink, while hypotonic solutions cause them to swell."}],"markDefs":[],"style":"normal"}] [{"_key":"block_24","_type":"block","asset":null,"children":[{"_key":"czv5QnE4jWWmyJTFsf24KV","_type":"span","markDefs":[],"marks":[],"text":"Red blood cells placed in a concentrated salt solution will shrink and develop a spiky appearance due to crenation."}],"markDefs":[],"style":"normal"}] ## Isotonic Solutions Is Where Cells Are Balanced and Stable [block_28] 1. In an **isotonic** solution, the concentration of solutes is **equal** inside and outside the cell. 2. Water moves in and out at the **same rate**, maintaining **equilibrium**. 3. **Why is this important**: Cells remain stable and functional, preventing swelling or shrinking. [{"_key":"block_35","_type":"block","asset":null,"children":[{"_key":"B6YuB78WQfXgiCeBjoFeda","_type":"span","markDefs":[],"marks":[],"text":"Intravenous (IV) fluids used in medical treatments are isotonic to human blood to ensure cells remain healthy."}],"markDefs":[],"style":"normal"}] [{"_key":"60dde566f4cf","_type":"block","asset":null,"children":[{"_key":"4db64c658c1c0","_type":"span","marks":[],"text":"Cells thrive in stable environments. "}],"level":1,"listItem":"bullet","markDefs":[],"style":"normal"},{"_key":"07332079aafc","_type":"block","asset":null,"children":[{"_key":"814a9aeb3210","_type":"span","marks":[],"text":"This is why your body works hard to maintain "},{"_key":"2c100046a10f","_type":"span","marks":["strong"],"text":"homeostasis"},{"_key":"0a3417300df1","_type":"span","marks":[],"text":"."}],"level":1,"listItem":"bullet","markDefs":[],"style":"normal"}] [{"_key":"block_38","_type":"block","asset":null,"children":[{"_key":"B6YuB78WQfXgiCeBjoFeeG","_type":"span","markDefs":[],"marks":[],"text":"How does the concept of isotonic solutions relate to the idea of balance in other systems, such as economic or ecological systems?"}],"markDefs":[],"style":"normal"}] ## Adaptations in Unicellular Organisms [block_39] 1. Freshwater unicellular organisms, like _Paramecium_, live in **hypotonic environments** where water constantly enters their cells. 2. Without adaptations like **contractile vacuoles**, they would burst. 3. **How contractile vacuoles work**: 1. Water enters the vacuole as solutes are pumped in, drawing water by osmosis. 2. The vacuole contracts and **expels excess water** from the cell.Contractile vacuoles require **energy** to function. ![](https://cdn.sanity.io/images/w7j7fz60/production/ff87856adcd359ff7cd8481c26d7cc92e37d12b6-751x738.jpg) [{"_key":"block_50","_type":"block","asset":null,"children":[{"_key":"B6YuB78WQfXgiCeBjoFeew","_type":"span","markDefs":[],"marks":[],"text":"Contractile vacuoles require energy to function, highlighting the trade-off between survival and energy expenditure."}],"markDefs":[],"style":"normal"}] ## The Need to Maintain Isotonic Conditions [80518583c9b2] 1. Multicellular organisms must carefully regulate the **solute concentration of their extracellular fluids** to prevent cells from swelling or shrinking. 2. **Why is this critical**: 1. Swelling or shrinking can disrupt cellular processes and organ function. 2. Organs like the brain are particularly sensitive to changes in water balance. [{"_key":"block_67","_type":"block","asset":null,"children":[{"_key":"897fc4562325","_type":"span","markDefs":[],"marks":[],"text":"Can you explain what happens to a cell in hypotonic, hypertonic, and isotonic solutions? "}],"level":1,"listItem":"bullet","markDefs":[],"style":"normal"},{"_key":"a52e51cf7465","_type":"block","asset":null,"children":[{"_key":"ca14f1c20091","_type":"span","markDefs":[],"marks":[],"text":"How do contractile vacuoles help unicellular organisms survive in freshwater environments?"}],"level":1,"listItem":"bullet","markDefs":[],"style":"normal"}]