<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    html, body {
      width: 100%;
      height: 100%;
      background: #f8fafc;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e293b;
      user-select: none;
      -webkit-user-select: none;
      display: flex;
      flex-direction: column;
    }

    .app {
      display: flex;
      flex-direction: column;
      width: 100%;
      height: 100%;
      padding: 8px 10px;
      gap: 6px;
      justify-content: space-between;
    }

    /* Interactive filter buttons */
    .nav-bar {
      display: flex;
      flex-wrap: wrap;
      gap: 4px;
      justify-content: center;
      z-index: 10;
    }

    .pill-btn {
      appearance: none;
      border: 1px solid #cbd5e1;
      background: #ffffff;
      color: #475569;
      font-size: 12px;
      font-weight: 600;
      padding: 4px 8px;
      border-radius: 9999px;
      cursor: pointer;
      box-shadow: 0 1px 2px rgba(0,0,0,0.04);
      transition: background-color 0.2s ease, border-color 0.2s ease, color 0.2s ease, box-shadow 0.2s ease;
    }
    .pill-btn:hover {
      background: #f1f5f9;
      color: #0f172a;
    }
    .pill-btn.active {
      background: #0284c7;
      border-color: #0284c7;
      color: #ffffff;
      box-shadow: 0 0 0 2px rgba(2, 132, 199, 0.25);
    }

    /* Diagram Stage */
    .stage {
      position: relative;
      flex: 1;
      width: 100%;
      min-height: 220px;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    svg {
      width: 100%;
      height: 100%;
      max-height: 330px;
      overflow: visible;
    }

    /* Regions / Component Groups */
    .comp-group {
      cursor: pointer;
      transition: opacity 0.3s ease, filter 0.3s ease;
    }
    .dimmed {
      opacity: 0.22 !important;
      filter: grayscale(40%);
    }
    .highlighted {
      opacity: 1 !important;
      filter: drop-shadow(0 0 4px rgba(2, 132, 199, 0.4));
    }

    /* Label text in SVG */
    .zone-tag {
      font-size: 11px;
      font-weight: 700;
      fill: #64748b;
      letter-spacing: 0.5px;
      text-anchor: middle;
    }

    /* Info card at bottom */
    .info-box {
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 6px 12px;
      text-align: center;
      min-height: 48px;
      display: flex;
      flex-direction: column;
      justify-content: center;
      box-shadow: 0 1px 3px rgba(0,0,0,0.05);
    }
    .info-title {
      font-size: 13px;
      font-weight: 700;
      color: #0f172a;
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      font-size: 12px;
      color: #475569;
      line-height: 1.25;
      margin-top: 2px;
    }

    /* Pin markers */
    .pin {
      cursor: pointer;
      transition: opacity 0.2s ease;
    }
    .pin-circle {
      fill: #ffffff;
      stroke: #0284c7;
      stroke-width: 2;
      box-shadow: 0 2px 4px rgba(0,0,0,0.2);
    }
    .pin-text {
      font-size: 10px;
      font-weight: 800;
      fill: #0284c7;
      text-anchor: middle;
      dominant-baseline: central;
    }
    .pin.active .pin-circle {
      fill: #0284c7;
      stroke: #ffffff;
    }
    .pin.active .pin-text {
      fill: #ffffff;
    }
  </style>
</head>
<body>
  <div class="app">
    
    <div class="nav-bar">
      <button class="pill-btn active" data-id="all" onclick="selectComponent('all')">Show All</button>
      <button class="pill-btn" data-id="bilayer" onclick="selectComponent('bilayer')">Phospholipids</button>
      <button class="pill-btn" data-id="integral" onclick="selectComponent('integral')">Integral Protein</button>
      <button class="pill-btn" data-id="peripheral" onclick="selectComponent('peripheral')">Peripheral Protein</button>
      <button class="pill-btn" data-id="cholesterol" onclick="selectComponent('cholesterol')">Cholesterol</button>
      <button class="pill-btn" data-id="glyco" onclick="selectComponent('glyco')">Glycocalyx</button>
    </div>

    
    <div class="stage">
      <svg viewBox="0 0 600 300" preserveAspectRatio="xMidYMid meet">
        <defs>
          
          <radialGradient id="headGrad" cx="35%" cy="35%" r="65%">
            <stop offset="0%" stop-color="#38bdf8"/>
            <stop offset="100%" stop-color="#0284c7"/>
          </radialGradient>
          <linearGradient id="proteinGrad" x1="0%" y1="0%" x2="100%" y2="100%">
            <stop offset="0%" stop-color="#a855f7"/>
            <stop offset="100%" stop-color="#6b21a8"/>
          </linearGradient>
          <linearGradient id="channelGrad" x1="0%" y1="0%" x2="0%" y2="100%">
            <stop offset="0%" stop-color="#581c87"/>
            <stop offset="50%" stop-color="#3b0764"/>
            <stop offset="100%" stop-color="#581c87"/>
          </linearGradient>
          <radialGradient id="periphGrad" cx="30%" cy="30%" r="70%">
            <stop offset="0%" stop-color="#34d399"/>
            <stop offset="100%" stop-color="#059669"/>
          </radialGradient>
          <linearGradient id="cholGrad" x1="0%" y1="0%" x2="100%" y2="100%">
            <stop offset="0%" stop-color="#fef08a"/>
            <stop offset="100%" stop-color="#eab308"/>
          </linearGradient>
        </defs>

        
        <text x="300" y="24" class="zone-tag">EXTRACELLULAR FLUID (OUTSIDE)</text>
        <line x1="30" y1="30" x2="570" y2="30" stroke="#e2e8f0" stroke-dasharray="4 4" stroke-width="1.5"/>

        <text x="300" y="292" class="zone-tag">CYTOPLASM (INSIDE)</text>
        <line x1="30" y1="278" x2="570" y2="278" stroke="#e2e8f0" stroke-dasharray="4 4" stroke-width="1.5"/>

        
        <g id="grp-bilayer" class="comp-group" onclick="selectComponent('bilayer')">
          
          <g stroke="#f59e0b" stroke-width="2.5" stroke-linecap="round" fill="none">
            
            
            <path d="M 38 120 Q 34 140 40 155 M 44 120 Q 48 138 42 155"/>
            <path d="M 68 120 Q 64 140 70 155 M 74 120 Q 78 138 72 155"/>
            <path d="M 98 120 Q 94 140 100 155 M 104 120 Q 108 138 102 155"/>
            <path d="M 128 120 Q 124 140 130 155 M 134 120 Q 138 138 132 155"/>
            <path d="M 158 120 Q 154 140 160 155 M 164 120 Q 168 138 162 155"/>
            <path d="M 188 120 Q 184 140 190 155 M 194 120 Q 198 138 192 155"/>
            
            <path d="M 338 120 Q 334 140 340 155 M 344 120 Q 348 138 342 155"/>
            <path d="M 368 120 Q 364 140 370 155 M 374 120 Q 378 138 372 155"/>
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            <path d="M 458 120 Q 454 140 460 155 M 464 120 Q 468 138 462 155"/>
            <path d="M 488 120 Q 484 140 490 155 M 494 120 Q 498 138 492 155"/>
            <path d="M 518 120 Q 514 140 520 155 M 524 120 Q 528 138 522 155"/>
            <path d="M 548 120 Q 544 140 550 155 M 554 120 Q 558 138 552 155"/>

            
            
            <path d="M 38 180 Q 34 160 40 155 M 44 180 Q 48 162 42 155"/>
            <path d="M 68 180 Q 64 160 70 155 M 74 180 Q 78 162 72 155"/>
            <path d="M 98 180 Q 94 160 100 155 M 104 180 Q 108 162 102 155"/>
            <path d="M 128 180 Q 124 160 130 155 M 134 180 Q 138 162 132 155"/>
            <path d="M 158 180 Q 154 160 160 155 M 164 180 Q 168 162 162 155"/>
            <path d="M 188 180 Q 184 160 190 155 M 194 180 Q 198 162 192 155"/>
            
            <path d="M 338 180 Q 334 160 340 155 M 344 180 Q 348 162 342 155"/>
            <path d="M 368 180 Q 364 160 370 155 M 374 180 Q 378 162 372 155"/>
            <path d="M 398 180 Q 394 160 400 155 M 404 180 Q 408 162 402 155"/>
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            <path d="M 458 180 Q 454 160 460 155 M 464 180 Q 468 162 462 155"/>
            <path d="M 488 180 Q 484 160 490 155 M 494 180 Q 498 162 492 155"/>
            <path d="M 518 180 Q 514 160 520 155 M 524 180 Q 528 162 522 155"/>
            <path d="M 548 180 Q 544 160 550 155 M 554 180 Q 558 162 552 155"/>
          </g>

          
          <g fill="url(#headGrad)" stroke="#0369a1" stroke-width="1.5">
            <circle cx="41" cy="112" r="12"/>
            <circle cx="71" cy="112" r="12"/>
            <circle cx="101" cy="112" r="12"/>
            <circle cx="131" cy="112" r="12"/>
            <circle cx="161" cy="112" r="12"/>
            <circle cx="191" cy="112" r="12"/>

            <circle cx="341" cy="112" r="12"/>
            <circle cx="371" cy="112" r="12"/>
            <circle cx="401" cy="112" r="12"/>
            <circle cx="431" cy="112" r="12"/>
            <circle cx="461" cy="112" r="12"/>
            <circle cx="491" cy="112" r="12"/>
            <circle cx="521" cy="112" r="12"/>
            <circle cx="551" cy="112" r="12"/>
          </g>

          
          <g fill="url(#headGrad)" stroke="#0369a1" stroke-width="1.5">
            <circle cx="41" cy="188" r="12"/>
            <circle cx="71" cy="188" r="12"/>
            <circle cx="101" cy="188" r="12"/>
            <circle cx="131" cy="188" r="12"/>
            <circle cx="161" cy="188" r="12"/>
            <circle cx="191" cy="188" r="12"/>

            <circle cx="341" cy="188" r="12"/>
            <circle cx="371" cy="188" r="12"/>
            <circle cx="401" cy="188" r="12"/>
            <circle cx="431" cy="188" r="12"/>
            <circle cx="461" cy="188" r="12"/>
            <circle cx="491" cy="188" r="12"/>
            <circle cx="521" cy="188" r="12"/>
            <circle cx="551" cy="188" r="12"/>
          </g>
        </g>

        
        <g id="grp-cholesterol" class="comp-group" onclick="selectComponent('cholesterol')">
          
          <g transform="translate(116, 134)">
            <path d="M0,0 L12,-6 L18,8 L6,14 Z" fill="url(#cholGrad)" stroke="#ca8a04" stroke-width="1.2"/>
            <path d="M12,-6 L22,0 L18,8 Z" fill="url(#cholGrad)" stroke="#ca8a04" stroke-width="1.2"/>
            <line x1="6" y1="14" x2="4" y2="24" stroke="#ca8a04" stroke-width="1.5"/>
          </g>

          
          <g transform="translate(415, 142)">
            <path d="M0,8 L10,0 L18,10 L8,18 Z" fill="url(#cholGrad)" stroke="#ca8a04" stroke-width="1.2"/>
            <path d="M10,0 L20,4 L18,10 Z" fill="url(#cholGrad)" stroke="#ca8a04" stroke-width="1.2"/>
            <line x1="0" y1="8" x2="-4" y2="18" stroke="#ca8a04" stroke-width="1.5"/>
          </g>

          
          <g transform="translate(506, 132)">
            <path d="M0,0 L12,-4 L16,8 L4,12 Z" fill="url(#cholGrad)" stroke="#ca8a04" stroke-width="1.2"/>
            <line x1="4" y1="12" x2="2" y2="22" stroke="#ca8a04" stroke-width="1.5"/>
          </g>
        </g>

        
        <g id="grp-integral" class="comp-group" onclick="selectComponent('integral')">
          
          
          <path d="M 226,92 C 220,105 214,130 214,150 C 214,170 220,195 226,208 C 238,212 254,212 260,208 C 254,195 250,170 250,150 C 250,130 254,105 260,92 C 254,88 238,88 226,92 Z"
                fill="url(#proteinGrad)" stroke="#581c87" stroke-width="2"/>
          
          <path d="M 276,92 C 282,105 286,130 286,150 C 286,170 282,195 276,208 C 288,212 304,212 310,208 C 316,195 322,170 322,150 C 322,130 316,105 310,92 C 304,88 288,88 276,92 Z"
                fill="url(#proteinGrad)" stroke="#581c87" stroke-width="2"/>
          
          <ellipse cx="268" cy="94" rx="14" ry="5" fill="url(#channelGrad)"/>
          <ellipse cx="268" cy="206" rx="14" ry="5" fill="url(#channelGrad)"/>
        </g>

        
        <g id="grp-peripheral" class="comp-group" onclick="selectComponent('peripheral')">
          
          <ellipse cx="380" cy="224" rx="30" ry="18" fill="url(#periphGrad)" stroke="#047857" stroke-width="2"/>
          
          <path d="M 362,222 Q 380,230 398,222" stroke="#a7f3d0" stroke-width="2" fill="none" stroke-linecap="round"/>
        </g>

        
        <g id="grp-glyco" class="comp-group" onclick="selectComponent('glyco')">
          
          <g stroke="#059669" stroke-width="2" fill="#ec4899">
            <line x1="242" y1="90" x2="236" y2="70"/>
            <circle cx="236" cy="70" r="5"/>
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            <circle cx="224" cy="52" r="5" fill="#f43f5e"/>
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            <circle cx="232" cy="38" r="4.5" fill="#a855f7"/>
            
            <line x1="236" y1="70" x2="252" y2="58"/>
            <circle cx="252" cy="58" r="5" fill="#f59e0b"/>
            <line x1="252" y1="58" x2="266" y2="46"/>
            <circle cx="266" cy="46" r="4.5" fill="#10b981"/>
          </g>

          
          <g stroke="#059669" stroke-width="2" fill="#06b6d4">
            <line x1="461" y1="100" x2="466" y2="78"/>
            <circle cx="466" cy="78" r="5"/>
            <line x1="466" y1="78" x2="480" y2="62"/>
            <circle cx="480" cy="62" r="5" fill="#3b82f6"/>
            <line x1="480" y1="62" x2="475" y2="44"/>
            <circle cx="475" cy="44" r="4.5" fill="#ec4899"/>
            
            <line x1="480" y1="62" x2="498" y2="56"/>
            <circle cx="498" cy="56" r="4.5" fill="#f59e0b"/>
          </g>
        </g>

        
        
        <g id="pin-bilayer" class="pin" onclick="selectComponent('bilayer')" transform="translate(68, 148)">
          <circle class="pin-circle" cx="0" cy="0" r="11"/>
          <text class="pin-text" x="0" y="0">1</text>
        </g>

        
        <g id="pin-integral" class="pin" onclick="selectComponent('integral')" transform="translate(268, 150)">
          <circle class="pin-circle" cx="0" cy="0" r="11"/>
          <text class="pin-text" x="0" y="0">2</text>
        </g>

        
        <g id="pin-peripheral" class="pin" onclick="selectComponent('peripheral')" transform="translate(380, 224)">
          <circle class="pin-circle" cx="0" cy="0" r="11"/>
          <text class="pin-text" x="0" y="0">3</text>
        </g>

        
        <g id="pin-cholesterol" class="pin" onclick="selectComponent('cholesterol')" transform="translate(126, 142)">
          <circle class="pin-circle" cx="0" cy="0" r="11"/>
          <text class="pin-text" x="0" y="0">4</text>
        </g>

        
        <g id="pin-glyco" class="pin" onclick="selectComponent('glyco')" transform="translate(242, 54)">
          <circle class="pin-circle" cx="0" cy="0" r="11"/>
          <text class="pin-text" x="0" y="0">5</text>
        </g>
      </svg>
    </div>

    
    <div class="info-box">
      <div id="infoTitle" class="info-title">Fluid Mosaic Plasma Membrane</div>
      <div id="infoDesc" class="info-desc">Tap any numbered pin or component to isolate and explore its structural role.</div>
    </div>
  </div>

  <script>
    const data = {
      all: {
        title: "Fluid Mosaic Plasma Membrane",
        desc: "Tap any numbered pin or component to isolate and explore its structural role."
      },
      bilayer: {
        title: "1. Phospholipid Bilayer",
        desc: "Hydrophilic phosphate heads face water; hydrophobic fatty acid tails form a fluid barrier."
      },
      integral: {
        title: "2. Transmembrane (Integral) Protein",
        desc: "Spans both layers; functions as channel or carrier to transport polar molecules/ions."
      },
      peripheral: {
        title: "3. Peripheral Protein",
        desc: "Attached loosely to inner surface; supports cell shape, cell signalling, and enzyme activity."
      },
      cholesterol: {
        title: "4. Cholesterol",
        desc: "Fits between tails to regulate membrane fluidity and mechanical stability across temperatures."
      },
      glyco: {
        title: "5. Glycoproteins & Glycolipids",
        desc: "Extracellular carbohydrate chains acting as cell recognition receptors and antigens."
      }
    };

    const componentIds = ['bilayer', 'integral', 'peripheral', 'cholesterol', 'glyco'];

    function selectComponent(id) {
      // Update Buttons
      document.querySelectorAll('.pill-btn').forEach(btn => {
        btn.classList.toggle('active', btn.getAttribute('data-id') === id);
      });

      // Update Info Box
      const info = data[id] || data.all;
      document.getElementById('infoTitle').textContent = info.title;
      document.getElementById('infoDesc').textContent = info.desc;

      // Update Highlights / Dims on SVG
      if (id === 'all') {
        componentIds.forEach(cId => {
          const grp = document.getElementById('grp-' + cId);
          const pin = document.getElementById('pin-' + cId);
          if (grp) grp.className.baseVal = 'comp-group';
          if (pin) pin.classList.remove('active');
        });
      } else {
        componentIds.forEach(cId => {
          const grp = document.getElementById('grp-' + cId);
          const pin = document.getElementById('pin-' + cId);
          if (cId === id) {
            if (grp) grp.className.baseVal = 'comp-group highlighted';
            if (pin) pin.classList.add('active');
          } else {
            if (grp) grp.className.baseVal = 'comp-group dimmed';
            if (pin) pin.classList.remove('active');
          }
        });
      }
    }
  </script>
</body>
</html>

The Fluid Mosaic Model of the Plasma Membrane

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta name="aspect-ratio" content="4:3">
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: system-ui, -apple-system, sans-serif;
      color: #1e2945;
      background: #f8fafc;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      padding: 12px;
      min-height: 100%;
      user-select: none;
    }

    /* Controls Header */
    .controls {
      display: flex;
      gap: 8px;
      width: 100%;
      max-width: 440px;
      background: #e2e8f0;
      padding: 4px;
      border-radius: 24px;
      margin-bottom: 8px;
    }

    .tab-btn {
      flex: 1;
      border: none;
      background: transparent;
      padding: 8px 12px;
      border-radius: 20px;
      font-size: 14px;
      font-weight: 600;
      color: #64748b;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      transition: all 0.25s ease;
    }

    .tab-btn.active.cold {
      background: #ffffff;
      color: #0284c7;
      box-shadow: 0 2px 6px rgba(2, 132, 199, 0.15);
    }

    .tab-btn.active.warm {
      background: #ffffff;
      color: #ea580c;
      box-shadow: 0 2px 6px rgba(234, 88, 12, 0.15);
    }

    /* Bilayer Stage */
    .stage {
      width: 100%;
      max-width: 440px;
      height: 250px;
      background: #ffffff;
      border-radius: 12px;
      border: 1px solid #e2e8f0;
      position: relative;
      overflow: hidden;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    svg {
      width: 100%;
      height: 100%;
    }

    /* Status Bar */
    .status-bar {
      width: 100%;
      max-width: 440px;
      margin-top: 8px;
      background: #ffffff;
      border: 1px solid #e2e8f0;
      border-radius: 8px;
      padding: 8px 12px;
      display: flex;
      align-items: center;
      justify-content: space-between;
    }

    .badge {
      display: inline-flex;
      align-items: center;
      gap: 5px;
      font-size: 13px;
      font-weight: 700;
      color: #16a34a;
      background: #dcfce7;
      padding: 3px 8px;
      border-radius: 12px;
    }

    .state-desc {
      font-size: 13px;
      font-weight: 600;
      color: #475569;
    }

    /* SVG Molecular Animations */
    .tail-warm {
      animation: tailWiggle 0.4s ease-in-out infinite alternate;
      transform-origin: center top;
    }
    .tail-warm-rev {
      animation: tailWiggleRev 0.4s ease-in-out infinite alternate;
      transform-origin: center top;
    }
    .tail-cold {
      animation: tailShiver 1.8s ease-in-out infinite alternate;
    }

    @keyframes tailWiggle {
      0% { transform: rotate(-8deg) scaleX(1.1); }
      100% { transform: rotate(8deg) scaleX(0.9); }
    }
    @keyframes tailWiggleRev {
      0% { transform: rotate(8deg) scaleX(0.9); }
      100% { transform: rotate(-8deg) scaleX(1.1); }
    }
    @keyframes tailShiver {
      0% { transform: rotate(-1deg); }
      100% { transform: rotate(1deg); }
    }

    .lipid-group {
      transition: transform 0.5s cubic-bezier(0.4, 0, 0.2, 1);
    }
  </style>
</head>
<body>

  
  <div class="controls">
    <button id="btnCold" class="tab-btn cold active" onclick="setTemp('cold')">
      ❄️ Low Temp (Cold)
    </button>
    <button id="btnWarm" class="tab-btn warm" onclick="setTemp('warm')">
      ☀️ High Temp (Warm)
    </button>
  </div>

  
  <div class="stage">
    <svg viewBox="0 0 400 240">
      <defs>
        
        <radialGradient id="headGrad" cx="35%" cy="35%" r="65%">
          <stop offset="0%" stop-color="#38bdf8" />
          <stop offset="100%" stop-color="#0284c7" />
        </radialGradient>
        
        <linearGradient id="cholsGrad" x1="0%" y1="0%" x2="100%" y2="100%">
          <stop offset="0%" stop-color="#fde047" />
          <stop offset="100%" stop-color="#d97706" />
        </linearGradient>
      </defs>

      
      <rect x="0" y="0" width="400" height="30" fill="#f0f9ff" opacity="0.8"/>
      <rect x="0" y="210" width="400" height="30" fill="#f0f9ff" opacity="0.8"/>

      
      <g id="bilayerContainer">
        
      </g>
    </svg>
  </div>

  
  <div class="status-bar">
    <span id="stateAction" class="state-desc">Wedges prevent crystalline packing</span>
    <span class="badge">✓ Optimal Fluidity</span>
  </div>

  <script>
    let currentTemp = 'cold';

    function renderMembrane() {
      const container = document.getElementById('bilayerContainer');
      const isCold = currentTemp === 'cold';

      // Spacing & offsets
      const positions = isCold
        ? [35, 75, 120, 160, 205, 245, 290, 330, 370] 
        : [25, 70, 120, 170, 215, 265, 310, 355, 385];

      const cholsIndices = [2, 6]; // Index positions of cholesterol

      let svgHtml = '';

      // Top Monolayer (Facing Up)
      positions.forEach((x, i) => {
        if (cholsIndices.includes(i)) {
          // Cholesterol Molecule
          svgHtml += `
            <g class="lipid-group" transform="translate(${x}, 58)">
              
              <circle cx="6" cy="2" r="3.5" fill="#f59e0b" />
              
              <rect x="1" y="8" width="10" height="38" rx="4" fill="url(#cholsGrad)" stroke="#b45309" stroke-width="1.2"/>
              <line x1="3" y1="18" x2="9" y2="18" stroke="#b45309" stroke-width="1"/>
              <line x1="3" y1="28" x2="9" y2="28" stroke="#b45309" stroke-width="1"/>
              <line x1="3" y1="38" x2="9" y2="38" stroke="#b45309" stroke-width="1"/>
              
              <path d="M6,46 L6,58" stroke="#d97706" stroke-width="2" stroke-linecap="round"/>
            </g>
          `;
        } else {
          // Phospholipid
          const animClass = isCold ? 'tail-cold' : (i % 2 === 0 ? 'tail-warm' : 'tail-warm-rev');
          const tailSpread = isCold ? 'M -3,0 Q -2,25 -2,52 M 3,0 Q 2,25 2,52' : 'M -3,0 Q -10,25 -5,52 M 3,0 Q 10,25 6,52';
          svgHtml += `
            <g class="lipid-group" transform="translate(${x}, 50)">
              
              <g class="${animClass}" transform="translate(0, 10)">
                <path d="${tailSpread}" fill="none" stroke="#64748b" stroke-width="2.6" stroke-linecap="round"/>
              </g>
              
              <circle cx="0" cy="0" r="9" fill="url(#headGrad)"/>
            </g>
          `;
        }
      });

      // Bottom Monolayer (Facing Down)
      positions.forEach((x, i) => {
        const botChols = [3, 5];
        if (botChols.includes(i)) {
          // Cholesterol Molecule
          svgHtml += `
            <g class="lipid-group" transform="translate(${x}, 124)">
              
              <path d="M6,2 L6,14" stroke="#d97706" stroke-width="2" stroke-linecap="round"/>
              
              <rect x="1" y="14" width="10" height="38" rx="4" fill="url(#cholsGrad)" stroke="#b45309" stroke-width="1.2"/>
              <line x1="3" y1="24" x2="9" y2="24" stroke="#b45309" stroke-width="1"/>
              <line x1="3" y1="34" x2="9" y2="34" stroke="#b45309" stroke-width="1"/>
              <line x1="3" y1="44" x2="9" y2="44" stroke="#b45309" stroke-width="1"/>
              
              <circle cx="6" cy="58" r="3.5" fill="#f59e0b" />
            </g>
          `;
        } else {
          // Phospholipid
          const animClass = isCold ? 'tail-cold' : (i % 2 === 0 ? 'tail-warm-rev' : 'tail-warm');
          const tailSpread = isCold ? 'M -3,0 Q -2,-25 -2,-52 M 3,0 Q 2,-25 2,-52' : 'M -3,0 Q -10,-25 -5,-52 M 3,0 Q 10,-25 6,-52';
          svgHtml += `
            <g class="lipid-group" transform="translate(${x}, 190)">
              
              <g class="${animClass}" transform="translate(0, -10)">
                <path d="${tailSpread}" fill="none" stroke="#64748b" stroke-width="2.6" stroke-linecap="round"/>
              </g>
              
              <circle cx="0" cy="0" r="9" fill="url(#headGrad)"/>
            </g>
          `;
        }
      });

      // Static Labels / Legend Overlay inside SVG
      svgHtml += `
        <g transform="translate(10, 18)">
          <circle cx="4" cy="4" r="4.5" fill="url(#headGrad)" />
          <text x="13" y="7.5" font-size="11" font-weight="600" fill="#475569">Phospholipid</text>
        </g>
        <g transform="translate(305, 18)">
          <rect x="0" y="0" width="8" height="9" rx="2" fill="url(#cholsGrad)" stroke="#b45309" stroke-width="0.8"/>
          <text x="13" y="7.5" font-size="11" font-weight="600" fill="#b45309">Cholesterol</text>
        </g>
      `;

      container.innerHTML = svgHtml;
    }

    function setTemp(temp) {
      currentTemp = temp;
      document.getElementById('btnCold').classList.toggle('active', temp === 'cold');
      document.getElementById('btnWarm').classList.toggle('active', temp === 'warm');
      
      const actionText = document.getElementById('stateAction');
      if (temp === 'cold') {
        actionText.textContent = 'Cholesterol wedges block tight packing';
      } else {
        actionText.textContent = 'Cholesterol restrains rapid tail motion';
      }

      renderMembrane();
    }

    // Initialize
    renderMembrane();
  </script>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Phospholipid &amp; Bilayer</title>
  <style>
    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    body {
      width: 100%;
      background: #ffffff;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
      color: #1e2945;
      display: flex;
      flex-direction: column;
      align-items: center;
      padding: 10px 8px;
      user-select: none;
    }
    .toggle-bar {
      display: flex;
      background: #f1f5f9;
      padding: 3px;
      border-radius: 999px;
      gap: 4px;
      margin-bottom: 8px;
    }
    .toggle-btn {
      border: none;
      background: transparent;
      padding: 6px 16px;
      font-size: 13px;
      font-weight: 600;
      color: #64748b;
      border-radius: 999px;
      cursor: pointer;
      transition: background-color 0.2s ease, color 0.2s ease, box-shadow 0.2s ease;
    }
    .toggle-btn.active {
      background: #0284c7;
      color: #ffffff;
      box-shadow: 0 2px 6px rgba(2, 132, 199, 0.25);
    }
    .diagram-container {
      width: 100%;
      max-width: 680px;
      display: flex;
      flex-direction: row;
      justify-content: center;
      align-items: center;
      gap: 12px;
    }
    .panel-single {
      flex: 0 0 220px;
      max-width: 220px;
      display: flex;
      flex-direction: column;
      align-items: center;
    }
    .panel-divider {
      width: 1px;
      height: 240px;
      background: repeating-linear-gradient(to bottom, #cbd5e1, #cbd5e1 5px, transparent 5px, transparent 10px);
    }
    .panel-bilayer {
      flex: 1 1 400px;
      max-width: 440px;
      display: flex;
      flex-direction: column;
      align-items: center;
    }
    svg {
      width: 100%;
      height: auto;
      display: block;
      overflow: visible;
    }
    .label-title {
      font-size: 12px;
      font-weight: 700;
      fill: #1e2945;
    }
    .label-sub {
      font-size: 10.5px;
      font-weight: 600;
      fill: #64748b;
    }
    .force-layer {
      opacity: 0;
      transition: opacity 0.3s ease;
      pointer-events: none;
    }
    .forces-active .force-layer {
      opacity: 1;
    }
    .forces-active .base-water {
      opacity: 0.3;
    }
    .base-water {
      transition: opacity 0.3s ease;
    }

    @media (max-width: 520px) {
      body {
        padding: 8px 6px;
      }
      .diagram-container {
        flex-direction: column;
        gap: 8px;
      }
      .panel-single {
        flex: 0 0 auto;
        width: 100%;
        max-width: 320px;
      }
      .panel-divider {
        width: 100%;
        height: 1px;
        background: repeating-linear-gradient(to right, #cbd5e1, #cbd5e1 5px, transparent 5px, transparent 10px);
      }
      .panel-bilayer {
        flex: 0 0 auto;
        width: 100%;
        max-width: 360px;
      }
    }
  </style>
</head>
<body>

  <div class="toggle-bar">
    <button class="toggle-btn active" id="btnStruct" onclick="setMode('struct')">Structure</button>
    <button class="toggle-btn" id="btnForces" onclick="setMode('forces')">Water &amp; Forces</button>
  </div>

  <div class="diagram-container">
    
    <div class="panel-single">
      <svg viewBox="0 0 210 240">
        <defs>
          <path id="tail-single-straight" d="M 0,0 Q -4,22 0,44 T 0,78" fill="none" stroke="#f59e0b" stroke-width="4.5" stroke-linecap="round"/>
          <path id="tail-single-kinked" d="M 0,0 Q 4,18 1,36 L 14,72" fill="none" stroke="#f59e0b" stroke-width="4.5" stroke-linecap="round"/>
        </defs>

        
        <g transform="translate(105, 18)">
          <text x="0" y="0" class="label-title" text-anchor="middle" fill="#0284c7">Hydrophilic Head</text>
          <text x="0" y="14" class="label-sub" text-anchor="middle">Polar / Phosphate</text>
          <line x1="0" y1="20" x2="0" y2="34" stroke="#0284c7" stroke-width="1.5"/>
          <circle cx="0" cy="34" r="2.5" fill="#0284c7"/>
        </g>

        
        <g transform="translate(105, 78)">
          
          <circle cx="0" cy="0" r="26" fill="#0284c7"/>
          <text x="0" y="5" font-size="12" font-weight="700" fill="#ffffff" text-anchor="middle">PO₄³⁻</text>
          
          
          <g transform="translate(-9, 25)">
            <use href="#tail-single-straight"/>
          </g>
          <g transform="translate(9, 25)">
            <use href="#tail-single-kinked"/>
          </g>
        </g>

        
        <g transform="translate(105, 202)">
          <line x1="0" y1="-14" x2="0" y2="-2" stroke="#f59e0b" stroke-width="1.5"/>
          <circle cx="0" cy="-14" r="2.5" fill="#f59e0b"/>
          <text x="0" y="10" class="label-title" text-anchor="middle" fill="#d97706">Hydrophobic Tails</text>
          <text x="0" y="24" class="label-sub" text-anchor="middle">Non-polar Fatty Acids</text>
        </g>
      </svg>
    </div>

    
    <div class="panel-divider"></div>

    
    <div class="panel-bilayer">
      <svg viewBox="0 0 380 240">
        <defs>
          
          <g id="bl-down">
            <circle cx="0" cy="0" r="11" fill="#0284c7"/>
            <path d="M -3.5,10 Q -6,24 -3,38 T -3,56" fill="none" stroke="#f59e0b" stroke-width="3" stroke-linecap="round"/>
            <path d="M 3.5,10 Q 6,22 4,34 L 11,54" fill="none" stroke="#f59e0b" stroke-width="3" stroke-linecap="round"/>
          </g>

          
          <g id="bl-up">
            <circle cx="0" cy="0" r="11" fill="#0284c7"/>
            <path d="M -3.5,-10 Q -6,-24 -3,-38 T -3,-56" fill="none" stroke="#f59e0b" stroke-width="3" stroke-linecap="round"/>
            <path d="M 3.5,-10 Q 6,-22 4,-34 L 11,-54" fill="none" stroke="#f59e0b" stroke-width="3" stroke-linecap="round"/>
          </g>

          
          <g id="water-mol-sm">
            <circle cx="0" cy="0" r="5" fill="#38bdf8"/>
            <circle cx="-4" cy="-4" r="2.6" fill="#94a3b8"/>
            <circle cx="4" cy="-4" r="2.6" fill="#94a3b8"/>
          </g>
        </defs>

        
        <rect x="10" y="6" width="360" height="52" rx="6" fill="#f0f9ff"/>
        <rect x="10" y="182" width="360" height="52" rx="6" fill="#f0f9ff"/>

        
        <g transform="translate(190, 24)">
          <text x="0" y="0" class="label-title" text-anchor="middle">Extracellular Fluid</text>
          <text x="0" y="13" class="label-sub" text-anchor="middle">Aqueous (Water)</text>
        </g>
        <g transform="translate(190, 204)">
          <text x="0" y="0" class="label-title" text-anchor="middle">Cytosol</text>
          <text x="0" y="13" class="label-sub" text-anchor="middle">Aqueous (Water)</text>
        </g>

        
        <g class="base-water">
          <use href="#water-mol-sm" x="35" y="24"/>
          <use href="#water-mol-sm" x="80" y="38"/>
          <use href="#water-mol-sm" x="300" y="38"/>
          <use href="#water-mol-sm" x="345" y="24"/>

          <use href="#water-mol-sm" x="35" y="216"/>
          <use href="#water-mol-sm" x="80" y="202"/>
          <use href="#water-mol-sm" x="300" y="202"/>
          <use href="#water-mol-sm" x="345" y="216"/>
        </g>

        
        
        <use href="#bl-down" x="32" y="68"/>
        <use href="#bl-down" x="67" y="68"/>
        <use href="#bl-down" x="102" y="68"/>
        <use href="#bl-down" x="137" y="68"/>
        <use href="#bl-down" x="172" y="68"/>
        <use href="#bl-down" x="207" y="68"/>
        <use href="#bl-down" x="242" y="68"/>
        <use href="#bl-down" x="277" y="68"/>
        <use href="#bl-down" x="312" y="68"/>
        <use href="#bl-down" x="347" y="68"/>

        
        <use href="#bl-up" x="32" y="172"/>
        <use href="#bl-up" x="67" y="172"/>
        <use href="#bl-up" x="102" y="172"/>
        <use href="#bl-up" x="137" y="172"/>
        <use href="#bl-up" x="172" y="172"/>
        <use href="#bl-up" x="207" y="172"/>
        <use href="#bl-up" x="242" y="172"/>
        <use href="#bl-up" x="277" y="172"/>
        <use href="#bl-up" x="312" y="172"/>
        <use href="#bl-up" x="347" y="172"/>

        
        <g class="force-layer">
          
          <rect x="12" y="98" width="356" height="44" rx="6" fill="#fef3c7" fill-opacity="0.85" stroke="#f59e0b" stroke-width="1.2" stroke-dasharray="4,3"/>
          
          
          <rect x="100" y="109" width="180" height="22" rx="4" fill="#ffffff" stroke="#f59e0b" stroke-width="1.2"/>
          <text x="190" y="124" font-size="10.5" font-weight="700" fill="#b45309" text-anchor="middle">Hydrophobic Exclusion (Water Excluded)</text>

          
          <g stroke="#0284c7" stroke-width="1.5" stroke-dasharray="2.5,2.5">
            <line x1="32" y1="56" x2="32" y2="40"/>
            <line x1="102" y1="56" x2="102" y2="40"/>
            <line x1="172" y1="56" x2="172" y2="40"/>
            <line x1="242" y1="56" x2="242" y2="40"/>
            <line x1="312" y1="56" x2="312" y2="40"/>
            <line x1="347" y1="56" x2="347" y2="40"/>
          </g>

          
          <g stroke="#0284c7" stroke-width="1.5" stroke-dasharray="2.5,2.5">
            <line x1="32" y1="184" x2="32" y2="200"/>
            <line x1="102" y1="184" x2="102" y2="200"/>
            <line x1="172" y1="184" x2="172" y2="200"/>
            <line x1="242" y1="184" x2="242" y2="200"/>
            <line x1="312" y1="184" x2="312" y2="200"/>
            <line x1="347" y1="184" x2="347" y2="200"/>
          </g>

          
          <rect x="125" y="38" width="130" height="18" rx="4" fill="#0284c7"/>
          <text x="190" y="51" font-size="10" font-weight="700" fill="#ffffff" text-anchor="middle">✦ Hydrogen Bonding</text>

          <rect x="125" y="184" width="130" height="18" rx="4" fill="#0284c7"/>
          <text x="190" y="197" font-size="10" font-weight="700" fill="#ffffff" text-anchor="middle">✦ Hydrogen Bonding</text>
        </g>
      </svg>
    </div>
  </div>

  <script>
    function setMode(mode) {
      const isForces = mode === 'forces';
      document.body.classList.toggle('forces-active', isForces);
      document.getElementById('btnForces').classList.toggle('active', isForces);
      document.getElementById('btnStruct').classList.toggle('active', !isForces);
    }
  </script>
</body>
</html>

BIO-2.4

Aligned learning resources

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