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UPPCS Biology Gap Sheet: Human Digestion, Blood and Circulation.
UPPCS has asked 23 of these. 2 have not been asked yet. Lock the first list, then read the second: it holds what UPPCS has not used yet.
First, the concept
Digestion breaks food into absorbable units. Enzymes digest molecules, while bile emulsifies fats without being an enzyme. Most absorption takes place in the small intestine.
Blood transport depends on cells, plasma and pressure. Arteries carry blood away from the heart and veins return it; their names do not tell whether the blood is oxygen-rich.
✅ Already asked (23)
Digestion and liver
- Salivary amylase · Begins starch digestion in the mouth.
- Pepsin · Digests proteins in the acidic stomach.
- Trypsin · Pancreatic protease active in the small intestine.
- Bile · Made by liver and stored in gallbladder; emulsifies fat, contains no digestive enzymes.
- Small intestine · Main site of digestion and nutrient absorption; villi increase surface area.
- Secretin · Stimulates bicarbonate-rich pancreatic secretion in response to acidic chyme.
- Gastrin · Stimulates gastric acid secretion.
- Liver metabolism · Stores glycogen, forms urea and metabolises alcohol.
Blood and immunity
- Red blood cells · Carry haemoglobin; formed in red bone marrow and normally live about 120 days.
- Haemoglobin · Iron-containing protein carries oxygen and gives blood its red colour.
- Carbon monoxide binding · Forms carboxyhaemoglobin with high affinity; binding is strong but reversible.
- Carbon dioxide transport · Most CO₂ is carried as bicarbonate in blood.
- Platelets · Cell fragments from megakaryocytes help stop bleeding.
- Thrombin · Converts soluble fibrinogen to insoluble fibrin during clotting.
- Blood pH · Normal arterial blood pH is about 7.35–7.45.
- ABO discovery · Landsteiner identified the ABO blood-group system in 1900–1901.
- Rh factor · RhD is an important red-cell antigen; incompatibility can affect pregnancy.
- Interferons · Signalling proteins help cells defend against viral infection.
Heart and vessels
- Human heart chambers · Two atria and two ventricles; four chambers in total.
- Sinoatrial node · Natural pacemaker in the right atrium initiates the heartbeat.
- Blood pressure · About 120/80 mmHg is a typical resting reference; systolic precedes diastolic.
- Pulmonary vessels · Pulmonary artery carries oxygen-poor blood; pulmonary veins carry oxygen-rich blood.
- Lymph · Returns tissue fluid to blood and transports absorbed fats.
❌ Not asked yet (2)
🔒 2 items not asked yet
Digestion and liver: 1 · Heart and vessels: 1
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⚠️ O-negative is the usual universal red-cell donor; AB is the universal plasma donor. Compatibility checks still matter.
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