<!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, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
      color: #1e2945;
      background: transparent;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: space-between;
      min-height: 100%;
      padding: 10px 12px;
      user-select: none;
    }
    
    .nav-bar {
      display: flex;
      gap: 6px;
      width: 100%;
      max-width: 480px;
      margin-bottom: 8px;
    }
    .step-btn {
      flex: 1;
      padding: 6px 4px;
      font-size: 13px;
      font-weight: 600;
      border: 1px solid #cbd5e1;
      border-radius: 6px;
      background: #f8fafc;
      color: #64748b;
      cursor: pointer;
      text-align: center;
      transition: all 0.25s ease;
      white-space: nowrap;
    }
    .step-btn.active {
      background: #2563eb;
      color: #ffffff;
      border-color: #2563eb;
      box-shadow: 0 2px 4px rgba(37, 99, 235, 0.2);
    }

    .canvas-container {
      position: relative;
      width: 100%;
      max-width: 480px;
      height: 290px;
      background: #ffffff;
      border-radius: 12px;
      border: 1px solid #e2e8f0;
      overflow: hidden;
    }

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

    /* SVG Transitions */
    .smooth {
      transition: all 0.6s cubic-bezier(0.4, 0, 0.2, 1);
    }
    .fade {
      transition: opacity 0.4s ease;
    }

    /* Controls bar */
    .controls {
      display: flex;
      align-items: center;
      justify-content: space-between;
      width: 100%;
      max-width: 480px;
      margin-top: 8px;
    }
    .play-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      border-radius: 6px;
      padding: 4px 10px;
      font-size: 12px;
      font-weight: 600;
      color: #1e2945;
      cursor: pointer;
      display: flex;
      align-items: center;
      gap: 4px;
    }
    .legend {
      display: flex;
      gap: 10px;
      font-size: 11px;
      color: #475569;
      font-weight: 500;
      flex-wrap: wrap;
    }
    .legend-item {
      display: flex;
      align-items: center;
      gap: 4px;
    }
    .legend-dot {
      width: 8px;
      height: 8px;
      border-radius: 50%;
    }
  </style>
</head>
<body>

  
  <div class="nav-bar">
    <button class="step-btn active" onclick="setStep(0)">1. Binding</button>
    <button class="step-btn" onclick="setStep(1)">2. Engulfment</button>
    <button class="step-btn" onclick="setStep(2)">3. Digestion</button>
    <button class="step-btn" onclick="setStep(3)">4. Exocytosis</button>
  </div>

  
  <div class="canvas-container">
    <svg viewBox="0 0 400 270">
      <defs>
        
        <radialGradient id="nucGrad" cx="40%" cy="40%" r="60%">
          <stop offset="0%" stop-color="#818cf8"/>
          <stop offset="100%" stop-color="#4f46e5"/>
        </radialGradient>
        <radialGradient id="lysoGrad" cx="35%" cy="35%" r="65%">
          <stop offset="0%" stop-color="#34d399"/>
          <stop offset="100%" stop-color="#059669"/>
        </radialGradient>
      </defs>

      
      <path id="phagocyteBody" class="smooth" fill="#e0f2fe" stroke="#38bdf8" stroke-width="2.5"
        d="M 20,20 Q 220,15 360,20 Q 385,135 360,250 Q 200,255 20,250 Q 15,135 20,20 Z" />

      
      <g id="nucleus" transform="translate(65, 135)">
        <path fill="url(#nucGrad)" d="M -25,-40 C 5,-50 35,-20 25,5 C 40,25 20,45 -5,40 C -35,35 -40,5 -20,-10 C -40,-25 -35,-35 -25,-40 Z" />
        <text x="0" y="4" fill="#ffffff" font-size="10" font-weight="700" text-anchor="middle" opacity="0.9">Nucleus</text>
      </g>

      
      <g id="receptors" class="fade" opacity="1">
        <path d="M 360,110 L 372,110 M 372,106 L 372,114" stroke="#0284c7" stroke-width="2" stroke-linecap="round"/>
        <path d="M 360,135 L 374,135 M 374,130 L 374,140" stroke="#0284c7" stroke-width="2" stroke-linecap="round"/>
        <path d="M 360,160 L 372,160 M 372,156 L 372,164" stroke="#0284c7" stroke-width="2" stroke-linecap="round"/>
      </g>

      
      <g id="lyso1" class="smooth" transform="translate(160, 80)">
        <circle r="12" fill="url(#lysoGrad)" />
      </g>
      <g id="lyso2" class="smooth" transform="translate(165, 190)">
        <circle r="12" fill="url(#lysoGrad)" />
      </g>

      
      <ellipse id="phagosome" class="smooth" cx="300" cy="135" rx="0" ry="0" fill="#bae6fd" stroke="#0284c7" stroke-dasharray="3,3" stroke-width="1.5" opacity="0"/>

      
      <g id="enzymes" class="fade" opacity="0">
        <circle cx="232" cy="125" r="2.5" fill="#f59e0b"/>
        <circle cx="240" cy="142" r="2" fill="#f59e0b"/>
        <circle cx="225" cy="138" r="3" fill="#f59e0b"/>
        <circle cx="248" cy="128" r="2.5" fill="#f59e0b"/>
        <circle cx="236" cy="150" r="2" fill="#f59e0b"/>
      </g>

      
      <g id="bacterium" class="smooth" transform="translate(378, 135)">
        <rect x="-18" y="-9" width="36" height="18" rx="9" fill="#ef4444" stroke="#b91c1c" stroke-width="1.5"/>
        
        <path d="M -10,0 Q -5,-4 0,0 Q 5,4 10,0" stroke="#fca5a5" stroke-width="1.5" fill="none"/>
      </g>

      
      <g id="debris" class="smooth" opacity="0" transform="translate(240, 135)">
        <circle cx="-8" cy="-5" r="3" fill="#ef4444"/>
        <polygon points="5,-8 9,-3 4,-2" fill="#ef4444"/>
        <circle cx="7" cy="6" r="2.5" fill="#ef4444"/>
        <polygon points="-7,5 -3,8 -4,3" fill="#ef4444"/>
        <circle cx="0" cy="-1" r="2" fill="#ef4444"/>
      </g>

      
      <g id="labelTag" class="smooth" transform="translate(200, 248)">
        <text id="labelText" x="0" y="0" text-anchor="middle" font-size="12" font-weight="700" fill="#1e2945">Receptor Binding</text>
      </g>
    </svg>
  </div>

  
  <div class="controls">
    <div class="legend">
      <div class="legend-item"><span class="legend-dot" style="background:#ef4444"></span>Pathogen</div>
      <div class="legend-item"><span class="legend-dot" style="background:#10b981"></span>Lysosome</div>
      <div class="legend-item"><span class="legend-dot" style="background:#f59e0b"></span>Lysozyme</div>
    </div>
    <button id="playBtn" class="play-btn" onclick="togglePlay()">
      <span id="playIcon">⏸</span> Auto
    </button>
  </div>

  <script>
    let currentStep = 0;
    let timer = null;
    let isPlaying = true;

    const phagocyteBody = document.getElementById('phagocyteBody');
    const bacterium = document.getElementById('bacterium');
    const receptors = document.getElementById('receptors');
    const lyso1 = document.getElementById('lyso1');
    const lyso2 = document.getElementById('lyso2');
    const phagosome = document.getElementById('phagosome');
    const enzymes = document.getElementById('enzymes');
    const debris = document.getElementById('debris');
    const labelText = document.getElementById('labelText');
    const stepBtns = document.querySelectorAll('.step-btn');

    const steps = [
      {
        title: "1. Tracking & Binding",
        render: () => {
          phagocyteBody.setAttribute('d', 'M 20,20 Q 220,15 360,20 Q 385,135 360,250 Q 200,255 20,250 Q 15,135 20,20 Z');
          receptors.style.opacity = '1';
          bacterium.setAttribute('transform', 'translate(378, 135)');
          bacterium.style.opacity = '1';
          lyso1.setAttribute('transform', 'translate(160, 80)');
          lyso2.setAttribute('transform', 'translate(165, 190)');
          phagosome.setAttribute('rx', '0');
          phagosome.setAttribute('ry', '0');
          phagosome.style.opacity = '0';
          enzymes.style.opacity = '0';
          debris.style.opacity = '0';
        }
      },
      {
        title: "2. Pseudopodia & Phagosome",
        render: () => {
          // Pseudopodia wrapping around pathogen
          phagocyteBody.setAttribute('d', 'M 20,20 Q 220,15 340,20 Q 400,60 395,115 Q 350,135 395,155 Q 400,210 340,250 Q 200,255 20,250 Q 15,135 20,20 Z');
          receptors.style.opacity = '0';
          bacterium.setAttribute('transform', 'translate(335, 135)');
          bacterium.style.opacity = '1';
          lyso1.setAttribute('transform', 'translate(190, 95)');
          lyso2.setAttribute('transform', 'translate(195, 175)');
          phagosome.setAttribute('cx', '335');
          phagosome.setAttribute('cy', '135');
          phagosome.setAttribute('rx', '26');
          phagosome.setAttribute('ry', '20');
          phagosome.style.opacity = '1';
          enzymes.style.opacity = '0';
          debris.style.opacity = '0';
        }
      },
      {
        title: "3. Phagolysosome & Digestion",
        render: () => {
          // Closed cytoplasm membrane, lysosomes fused inside
          phagocyteBody.setAttribute('d', 'M 20,20 Q 220,15 365,20 Q 380,135 365,250 Q 200,255 20,250 Q 15,135 20,20 Z');
          receptors.style.opacity = '0';
          bacterium.setAttribute('transform', 'translate(240, 135)');
          bacterium.style.opacity = '0'; // Broken down
          lyso1.setAttribute('transform', 'translate(225, 120)');
          lyso2.setAttribute('transform', 'translate(225, 150)');
          phagosome.setAttribute('cx', '238');
          phagosome.setAttribute('cy', '135');
          phagosome.setAttribute('rx', '30');
          phagosome.setAttribute('ry', '26');
          phagosome.style.opacity = '1';
          enzymes.style.opacity = '1';
          debris.setAttribute('transform', 'translate(240, 135)');
          debris.style.opacity = '1';
        }
      },
      {
        title: "4. Exocytosis of Debris",
        render: () => {
          // Vesicle fusing with right membrane to release debris
          phagocyteBody.setAttribute('d', 'M 20,20 Q 220,15 360,20 Q 345,115 330,135 Q 345,155 360,250 Q 200,255 20,250 Q 15,135 20,20 Z');
          receptors.style.opacity = '0';
          bacterium.style.opacity = '0';
          lyso1.setAttribute('transform', 'translate(150, 80)');
          lyso2.setAttribute('transform', 'translate(155, 190)');
          phagosome.setAttribute('cx', '335');
          phagosome.setAttribute('cy', '135');
          phagosome.setAttribute('rx', '18');
          phagosome.setAttribute('ry', '18');
          phagosome.style.opacity = '0';
          enzymes.style.opacity = '0';
          debris.setAttribute('transform', 'translate(378, 135)');
          debris.style.opacity = '0.8';
        }
      }
    ];

    function setStep(index) {
      currentStep = index;
      stepBtns.forEach((btn, idx) => {
        btn.classList.toggle('active', idx === currentStep);
      });
      labelText.textContent = steps[currentStep].title;
      steps[currentStep].render();
    }

    function nextStep() {
      setStep((currentStep + 1) % steps.length);
    }

    function startAutoPlay() {
      if (timer) clearInterval(timer);
      timer = setInterval(nextStep, 3200);
      isPlaying = true;
      document.getElementById('playIcon').textContent = '⏸';
    }

    function pauseAutoPlay() {
      if (timer) clearInterval(timer);
      isPlaying = false;
      document.getElementById('playIcon').textContent = '▶';
    }

    function togglePlay() {
      if (isPlaying) pauseAutoPlay();
      else {
        nextStep();
        startAutoPlay();
      }
    }

    // Init
    setStep(0);
    startAutoPlay();
  </script>
</body>
</html>

Phagocytosis: Engulfing and Digesting Pathogens

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <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: 8px 12px;
      user-select: none;
    }

    .main-view {
      position: relative;
      width: 100%;
      max-width: 580px;
      aspect-ratio: 16 / 10;
      overflow: visible;
    }

    svg {
      width: 100%;
      height: 100%;
      display: block;
      overflow: visible;
    }

    .nav-controls {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 10px;
      margin-top: 14px;
      width: 100%;
      max-width: 580px;
      flex-wrap: wrap;
    }

    .step-btn {
      background: #f1f5f9;
      border: 1px solid #cbd5e1;
      border-radius: 20px;
      padding: 7px 16px;
      font-size: 13px;
      font-weight: 600;
      color: #334155;
      cursor: pointer;
      transition: background-color 0.25s ease, border-color 0.25s ease, color 0.25s ease;
    }

    .step-btn:hover {
      background: #e2e8f0;
      border-color: #94a3b8;
    }

    .step-btn.active {
      background: #0284c7;
      border-color: #0284c7;
      color: #ffffff;
    }

    .step-btn:focus-visible {
      outline: 2px solid #0284c7;
      outline-offset: 2px;
    }

    /* Smooth, non-flickering cell animation */
    .phagocyte-group {
      transition: transform 1s cubic-bezier(0.4, 0, 0.2, 1);
      will-change: transform;
    }

    .label-text {
      font-size: 11.5px;
      font-weight: 700;
      fill: #1e2945;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    }

    .scent-dot {
      animation: pulseDot 2.8s ease-in-out infinite alternate;
    }

    @keyframes pulseDot {
      0% { opacity: 0.25; }
      100% { opacity: 0.85; }
    }

    @media (max-width: 420px) {
      .label-text {
        font-size: 10.5px;
      }
      .step-btn {
        padding: 5px 12px;
        font-size: 12px;
      }
    }
  </style>
</head>
<body>

  <div class="main-view">
    <svg viewBox="0 0 540 330" id="chemotaxisSvg" aria-label="Phagocyte Chemotaxis and Receptor Binding Diagram">
      <defs>
        
        <radialGradient id="chemGrad" cx="82%" cy="50%" r="78%">
          <stop offset="0%" stop-color="#0284c7" stop-opacity="0.30" />
          <stop offset="45%" stop-color="#38bdf8" stop-opacity="0.16" />
          <stop offset="80%" stop-color="#e0f2fe" stop-opacity="0.08" />
          <stop offset="100%" stop-color="#ffffff" stop-opacity="0" />
        </radialGradient>

        
        <g id="yReceptor">
          <path d="M 0 0 L 0 -6 M 0 -6 L -4 -11 M 0 -6 L 4 -11" stroke="#0369a1" stroke-width="2.2" stroke-linecap="round" stroke-linejoin="round" fill="none" />
        </g>
        
        
        <g id="antigen">
          <circle cx="0" cy="0" r="2.6" fill="#e11d48" stroke="#9f1239" stroke-width="0.8"/>
        </g>
      </defs>

      
      <rect x="0" y="0" width="540" height="330" fill="url(#chemGrad)" />

      
      <g id="scentDots">
        <circle class="scent-dot" cx="420" cy="140" r="3" fill="#0284c7" style="animation-delay: 0s" />
        <circle class="scent-dot" cx="405" cy="180" r="2.5" fill="#0284c7" style="animation-delay: 0.3s" />
        <circle class="scent-dot" cx="370" cy="115" r="2.5" fill="#0369a1" style="animation-delay: 0.6s" />
        <circle class="scent-dot" cx="355" cy="195" r="3" fill="#0369a1" style="animation-delay: 0.2s" />
        <circle class="scent-dot" cx="320" cy="155" r="2" fill="#0ea5e9" style="animation-delay: 0.8s" />
        <circle class="scent-dot" cx="280" cy="125" r="2.5" fill="#38bdf8" style="animation-delay: 0.4s" />
        <circle class="scent-dot" cx="290" cy="205" r="2" fill="#38bdf8" style="animation-delay: 0.9s" />
        <circle class="scent-dot" cx="240" cy="165" r="1.8" fill="#7dd3fc" style="animation-delay: 0.5s" />
        <circle class="scent-dot" cx="200" cy="120" r="1.8" fill="#bae6fd" style="animation-delay: 1.1s" />
        <circle class="scent-dot" cx="190" cy="210" r="1.5" fill="#bae6fd" style="animation-delay: 0.7s" />
      </g>

      
      <g transform="translate(170, 302)">
        <defs>
          <linearGradient id="barGrad" x1="0%" y1="0%" x2="100%" y2="0%">
            <stop offset="0%" stop-color="#e0f2fe"/>
            <stop offset="100%" stop-color="#0284c7"/>
          </linearGradient>
        </defs>
        <rect x="0" y="0" width="200" height="7" rx="3.5" fill="url(#barGrad)" stroke="#cbd5e1" stroke-width="0.8"/>
        <text x="100" y="-6" text-anchor="middle" class="label-text" fill="#0369a1">Chemotaxis Gradient →</text>
      </g>

      
      <g id="bacteriumGroup" transform="translate(450, 165)">
        
        <rect x="-18" y="-36" width="36" height="72" rx="18" fill="#e11d48" stroke="#be123c" stroke-width="2" transform="rotate(20)" />
        
        
        <g transform="rotate(20)">
          
          <use href="#antigen" x="-18" y="-20" />
          <use href="#antigen" x="-19" y="0" />
          <use href="#antigen" x="-18" y="20" />
          
          
          <use href="#antigen" x="18" y="-15" />
          <use href="#antigen" x="18" y="15" />
          <use href="#antigen" x="0" y="-36" />
          <use href="#antigen" x="0" y="36" />
          
          
          <path d="M -6 -15 Q 0 -5, 6 -15 M -8 5 Q 0 15, 8 5" stroke="#fda4af" stroke-width="1.8" fill="none" stroke-linecap="round"/>
        </g>
      </g>

      
      <g transform="translate(450, 48)">
        <text class="label-text" text-anchor="middle" fill="#be123c">Bacterium (Pathogen)</text>
        
        <path d="M 0 5 L 0 78" stroke="#be123c" stroke-width="1.2" stroke-dasharray="2,2"/>
        <circle cx="0" cy="78" r="2.5" fill="#be123c" />
      </g>

      
      <g id="phagocyteGroup" class="phagocyte-group" transform="translate(0, 0)">
        
        <path d="M 60 70 
                 C 120 50, 170 80, 190 120 
                 C 215 145, 220 185, 185 215 
                 C 150 245, 110 265, 65 240 
                 C 20 215, 10 160, 20 115 
                 C 30 75, 45 80, 60 70 Z" 
              fill="#dbeafe" stroke="#93c5fd" stroke-width="2.5" />

        
        <path d="M 65 125 
                 C 80 105, 105 110, 105 130 
                 C 118 132, 130 145, 120 165 
                 C 108 178, 85 170, 75 160 
                 C 60 175, 45 160, 50 145 
                 C 52 135, 58 130, 65 125 Z" 
              fill="#8b5cf6" opacity="0.85" stroke="#7c3aed" stroke-width="1.5" />

        
        <circle cx="82" cy="142" r="5" fill="#7c3aed" opacity="0.4"/>

        
        <g transform="translate(193, 135) rotate(55)"><use href="#yReceptor"/></g>
        <g transform="translate(202, 162) rotate(88)"><use href="#yReceptor"/></g>
        <g transform="translate(191, 190) rotate(115)"><use href="#yReceptor"/></g>
        <g transform="translate(165, 230) rotate(145)"><use href="#yReceptor"/></g>
        <g transform="translate(145, 68) rotate(-35)"><use href="#yReceptor"/></g>

        
        <g transform="translate(70, 32)">
          <text class="label-text" text-anchor="middle">Phagocyte</text>
          <path d="M 0 5 L 0 55 L 15 75" stroke="#1e2945" stroke-width="1.2" stroke-dasharray="2,2" fill="none"/>
          <circle cx="15" cy="75" r="2.5" fill="#1e2945"/>
        </g>

        
        <g transform="translate(160, 268)">
          <text class="label-text" text-anchor="middle" fill="#0369a1">Surface Receptors</text>
          <path d="M 12 -6 L 25 -32 L 28 -36" stroke="#0369a1" stroke-width="1.2" fill="none"/>
          <circle cx="28" cy="-36" r="2.5" fill="#0369a1"/>
        </g>
      </g>
    </svg>
  </div>

  
  <div class="nav-controls">
    <button class="step-btn active" id="btn1" onclick="setStage(1)" type="button">1. Chemotaxis Tracking</button>
    <button class="step-btn" id="btn2" onclick="setStage(2)" type="button">2. Receptor Binding</button>
  </div>

  <script>
    const phagocyte = document.getElementById('phagocyteGroup');
    const btn1 = document.getElementById('btn1');
    const btn2 = document.getElementById('btn2');

    let currentStage = 1;
    let autoTimer = null;

    function setStage(stage) {
      currentStage = stage;
      if (stage === 1) {
        phagocyte.style.transform = 'translate(0px, 0px)';
        btn1.classList.add('active');
        btn2.classList.remove('active');
      } else {
        // Smoothly advance phagocyte toward bacterium and dock receptors
        phagocyte.style.transform = 'translate(210px, 2px)';
        btn2.classList.add('active');
        btn1.classList.remove('active');
      }
    }

    // Auto cycle smoothly with comfortable hold time (4.5s) for hands-free demonstration
    function startCycle() {
      autoTimer = setInterval(() => {
        setStage(currentStage === 1 ? 2 : 1);
      }, 4500);
    }

    // Stop auto-timer on manual interaction
    [btn1, btn2].forEach(btn => {
      btn.addEventListener('click', () => {
        if (autoTimer) {
          clearInterval(autoTimer);
          autoTimer = null;
        }
      });
    });

    startCycle();
  </script>
</body>
</html>

UK-GCSE-SCIENCE-BIO-HDM-02-04

Aligned learning resources

Related diagrams