A-Level Biology

16:26 Topic 1 How We Study Cells You are built from about thirty trillion cells, yet you have never seen a single one. Cells are simply t… 19:33 Topic 2 Biological Molecules Suppose you have an unknown food sample. How do you tell what it is made of? Biology has a beautiful tri… 13:51 Topic 3 Enzymes Inside every cell, thousands of chemical reactions happen every second — far faster than they ever could… 14:03 Topic 4 Cell Membranes Every cell must keep the right things in and the wrong things out. That job falls to a single, astonishi… 7:20 Topic 5 Mitosis Right now, inside you, millions of cells are dividing. A cell grows, copies everything it contains, and … 9:37 Topic 6 DNA & Protein Synthesis Inside almost every one of your cells sits a molecule about two metres long, folded up so tightly you ca… 8:36 Topic 7 Transport in Plants A giant redwood lifts water more than a hundred metres into the air, every single day — and it has no he… 9:17 Topic 8 The Circulatory System Your heart beats about a hundred thousand times a day, and it never gets a day off. But here is the clev… 6:58 Topic 9 The Gas Exchange System Spread the inside of your lungs out flat and it would cover about seventy square metres — roughly half a… 8:28 Topic 10 Infectious Disease The animal that kills the most people every year is not the shark or the snake. It is the mosquito. And … 8:37 Topic 11 Immunity Catch measles once and you will almost certainly never catch it again. Your body has not become tougher,… 9:49 Topic 12 Respiration At any moment your body holds only about fifty grams of ATP. Yet over a single day you will make and spe… 8:58 Topic 13 Photosynthesis Here is something strange about a tree. Almost none of it came out of the ground. The wood, the leaves, … 9:42 Topic 14 Homeostasis Look at a day's worth of blood sugar. Three big meals go in — and the level hardly stirs. It wanders a l… 9:38 Topic 15 Nerves and Muscles Touch something hot and your hand is already moving before you feel the pain. The signal never went to y… 9:35 Topic 16 Genetics You have twenty three pairs of chromosomes. When a gamete is made, each pair lines up independently — ei… 8:23 Topic 17 Variation and Evolution In the early eighteen hundreds, almost every peppered moth in England was pale and speckled, which hid i… 8:00 Topic 18 Biodiversity About one point seven million species have been described and given a name. The best estimates say there… 8:31 Topic 19 Genetic technology Two cotton plants. Same field, same insects, same week. The one on the left is barely touched. The one o…