IGCSE Breathing, Respiration and Circulatory System Notes

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Annii Hart
Biology Summary Sheet
Respiration, lungs and breathing, smoking, and the circulatory system.
Respiration and Breathing
Energy Content per gram of food (J) = 4.2 x temp. Rise x 20/ mass of food
There are two types of respiration
Aerobic Respiration
Anaerobic Respiration
Aerobic Respiration takes place in living cells, inside the mitochondria, so is not present in
bacteria or viruses.
Anaerobic Respiration takes place in skeletal muscles, (in arm or leg muscles), and in yeast
Respiration happens so that the following functions can occur
We know that respiration has occurred when
CO2 is produced breathe into limewater to tell whether it is present.
Heat is produced.
Glucose/ oxygen are used up.
Aerobic Respiration
Respiration is a process that takes place in all living cells. Respiration transfers energy from
food molecules in animals and in plants. The energy from respiration is used to make smaller
molecules from large ones, to let muscles contract, and to keep a constant muscle
temperature. Respiration releases energy from food molecules in cells.
Glucose + Oxygen CO2 + water + energy
Anaerobic Respiration
Anaerobic respiration occurs in the skeletal muscle cells. The main difference between them
is that Aerobic respiration uses oxygen, while anaerobic respiration doesn't
Glucose Lactic Acid + a little energy
You respire anaerobically when you are exercising hard, and your muscles struggle to get the
oxygen to do aerobic respiration. (the heart and lungs struggle to put oxygen in the blood, and
then pump it around the blood.
Without the oxygen, the glucose transfers to lactic acid, with a little energy. The problem is
that the lactic cid builds up, and doesn't let the muscles contract correctly, meaning that you
get a `stitch'.
This lactic acid is poisonous, and must be removed. This is done by the body moving it to the
liver, and then breaking it down using oxygen. This is called oxygen debt.

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Gas Exchange in the Alveoli
Gas Inhaled (%) Exhaled (%)
Nitrogen 78 79
Oxygen 21 16
Carbon Dioxide 0.04 4
Other (Mainly Argon) 1 1
The lungs absorb the oxygen into the blood, and remove the carbon dioxide from it, in the
To make this efficient, the alveoli must have a structure that brings the blood and the air very
close, over a large surface area.…read more

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Nasal Cavity Cleans, warms, and moistens the air you breathe.
Bronchus Carries the air to the bronchioles.
Pleural Membranes Stops the lungs from collapsing.
Heart Pumps blood around the body.
Alveoli Gets the oxygen into and carbon dioxide out of, the blood.
Ribs Protects the lungs.
Lungs Contains millions of alveoli
Intercostal Muscles Muscles between the ribs that helps you breathe.
Epiglottis Stops food entering the windpipe.
Voice Box Responsible for speech.…read more

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- 3 x more likely to die within a week
- Malnutrition from poor milk production
- Lower oxygen levels in the blood
- Higher infant mortality rate
- Less immunity to flu and diarrhoea
- More likely to become smokers when older.
Problems for the mother include
- Higher risk of miscarriage
- Reduces fertility
During labour, complications like premature detachment of the placenta and the
membranes rupturing can occur as well as bleeding. Ectopic pregnancy is more
common too.…read more

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HepaticPortal Vein Carries blood with lots of glucose.
Renal Vein Blood that is low in urea from the kidneys to the heart
Brain Responsible for memory
Vena Cava Carries deoxygenated blood to the heart
Hepatic Artery Carries blood to the liver from the heart
Aorta Main artery of the body
Pulmonary Vein Carries oxygenated blood from the lungs back to the heart
Lungs Responsible for lungs.
Heart Pumps blood around the body
Renal Artery carries blood to the kidney from the heart.…read more

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Single cell thick wall as narrow as a red blood vessel.
Oxygen and glucose leave through diffusion
Carbon dioxide enters through diffusion
Only works because the distance between the capillaries and cells are tiny.
Capillaries are always very near a cell, so the capillaries can deliver oxygenated blood
The capillaries slow down the blood flow, so that there is more time for substances to
exchange.…read more


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