Respiration & Breathing

Our cells need energy… For: Movement (muscle contraction) Heat generation (37°C) Active transport (absorption in the gut) Nerve impulse transmission (brain activity)

Source of energy Our dietary intake of carbohydrate provides us with most of our energy Carbohydrates include starch and sugars Our digestive system turns these into glucose (a simple sugar) which passes into the blood and is transported to every cell in the body

Releasing energy from glucose Energy is released from glucose by a chemical reaction called respiration Respiration happens inside tiny organelles within cells called mitochondria The energy released from this reaction is used directly by the cell

Aerobic Respiration In addition to glucose, respiration needs oxygen When enough oxygen is present, the reaction is said to be aerobic (‘with air’)

Aerobic Respiration Glucose + Oxygen → Carbon dioxide + Water + ENERGY C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O + ENERGY

Diffusion In an area of high concentration, some of the particles collide with each other, lose energy and slow down. Others will escape from the concentrated area to places where there are fewer or no particles. Very few particles leave an area of low concentration to go to an area where the concentration is higher. The result is a concentration gradient, with particles diffusing from an area of high concentration to an area of low concentration. Particles in liquids and gases have kinetic energy. They move about, at speed, in all directions. kinetic energy

C0 2 Cell Blood capillary C0 2 Oxygen diffuses from blood to cell. Carbon dioxide diffuses from cell to the blood. Both move down their concentration gradients Exchange of gases: cells 0202

Exchange of gases: lungs When the blood flows through the lungs, CO 2 diffuses from the blood into the air, O 2 diffuses from the air into the blood The loss of CO 2 from the body in the breath can be detected by the following apparatus

Detecting the CO 2 produced during respiration Removes CO 2 from air Checks that CO 2 has been removed Detects CO 2 in exhaled air

Larynx Ring of cartilage Trachea Left lung Bronchus Heart Diaphragm Rib Pleural fluid Alveoli Pleural membranes Bronchiole Inner & outer intercostal muscles Structure of the lungs

The Lungs Air travels into the lungs via the nose, trachea, bronchi and bronchioles Each bronchiole ends in a sac called an alveolus The alveolus is the respiratory surface (place where air moves into the blood)

Alveoli alveolus capillary bronchiole

In the lungs, the blood will continue to take in oxygen from the alveolar air spaces, provided that there is more oxygen in the air spaces than in the blood. The oxygen diffuses across the alveolar walls into the blood. The circulation takes the oxygen-rich blood away and replaces it with blood low in oxygen.

Bronchiole Alveoli

A single alveolus Air space Alveolus wall (one cell thick) Red blood cells inside capillary

Alveoli These are ideally suited for gaseous exchange between air and blood. They have: A rich blood supply – lots of capillaries Thin ‘walls’ only one cell thick – easy to diffuse through Large surface area – space for diffusion Moist surfaces – for gases to dissolve into

Breathing The lungs cannot inhale and exhale on their own – they don’t have the muscles for this Instead, they rely on the contraction and relaxation of the intercostal muscles and the diaphragm (another large muscle)