Why do organisms need to exchange substances with their environment?
Some substances are needed e.g. oxygen for respiration
Sone waste substances need to be removed e.g. carbon dioxide from respiration
What does the ease of an organism exchanging substances with its environment depend on?
Its surface area to volume ratio
Why do multicellular organisms need transport systems and exchange surfaces?
They have smaller surface area to volume ratios than single celled organisms, which can rely on diffusion. This makes it difficult to supply their entire volume across their outside surface alone. Therefore they need exchange surfaces for efficient diffusion and a mass transport system to move substances to the rest of the body
What does the rate of diffusion depend on?
Distance, concentration gradient, surface area
How are alveoli adapted for efficient diffusion?
A moist lining to dissolve gases so they can diffuse faster
A good blood supply to maintain concentration gradients
Very thin walls to reduce diffusion distance
A very large total surface area
What is Fick’s Law?
Rate of diffusion is proportional to surface area * concentration difference / thickness of membrane
What is cellular respiration?
A continuous process that happens in every cell. Its purpose is to release energy by breaking down organic compounds (glucose). It is exothermic. There are two types: aerobic and anaerobic
What are the word and symbol equations for aerobic respiration?
Glucose + oxygen –> carbon dioxide + water
C6H12O6 + 6O2 –> 6CO2 + 6H2O
What are the word equation for anaerobic respiration in animals and plants?
Animals: Glucose –> lactic acid
Plants: Glucose –> ethanol + carbon dioxide
What is gas exchange?
The process of oxygen and carbon dioxide moving between the lungs and the blood
What is breathing?
The process of taking in oxygen and giving out carbon dioxide
What are platelets? How is their structure related to their function?
Small fragments of cells with no nucleus. They help the blood to clot at a wound. They can float around and clot when an accident happens
What is plasma? How is its structure related to its function?
A pale liquid that carries almost everything in the blood. It is not too viscous so it can flow easily
What are red blood cells? How is their structure related to their function?
They carry oxygen from the lungs to cells. They have a biconcave disc shape to have a large surface area for oxygen. They have no nucleus so they have more space for oxygen. They contain haemoglobin which binds to oxygen in a reversible process to form oxyhaemoglobin
What are white blood cells? How is their structure related to their function?
They kill unwanted microorganisms. Phagocytes can change shale to engulf microorganisms. Lymphocytes produce antibodies against microorganisms. Some produce antitoxins to neutralise their toxins. White blood cells multiply in an infection
What are the three types of blood vessels and their functions?
Arteries carry blood away from the heart
Capillaries exchange materials at tissues
Veins carry blood to the heart
How is the structure of arteries related to their function?
They have strong, thick, elastic walls to carry blood at high pressure. The elastic fibres allow them to stretch and spring back
How is the structure of capillaries related to their function?
They are very narrow to fit between cells. They have permeable, one cell thick walls to allow for quick diffusion. They supply food and oxygen and take away waste like CO2.
How is the structure veins of related to their function?
They have thinner walls to carry blood at lower pressure than arteries. They have a large lumen to help blood flow. They have valves to keep blood flowing in the right direction
What is the circulatory system like?
It is a double circulatory system - there are two parts: one that carries blood to the lungs and one that carries blood to the body
What is the function of the right atrium? Where does it take blood from and where does it pump it to?
It receives deoxygenated blood from the body through the vena cava and pumps it to the right ventricle through the tricuspid valve.
What is the function of the right ventricle? Where does it take blood from and where does it pump it to?
It receives deoxygenated blood from the right atrium through the tricuspid valve and pumps it to the lungs through a semi-luna valve through the pulmonary artery.
What is the function of the left atrium? Where does it take blood from and where does it pump it to?
It receives oxygenated blood from the lungs through the pulmonary vein and it pumps blood to the left ventricle through the bicuspid valve.
What is the function of the left ventricle? Where does it take blood from and where does it pump it to?
It receives oxygenated blood from the left atrium through the bicuspid valve and pumps it to the body through a semi-lunar valve through the aorta.
Why does the left ventricle have a thicker wall than the right one?
It pumps blood around the whole body at high pressure, rather than just the lungs, so it needs more muscle
How is cardiac output calculated?
Cardiac output (cm^3/min) = heart rate (bpm) * stroke volume (cm^3)
What is cardiac output?
The volume of blood ejected by the heart ventricles in one minute
How can you investigate the rate of respiration using a respirometer?
Add soda lime granules to two test tubes (to absorb CO2). Put balls of cotton wool on top of the soda limes and place woodlice on top of one and glass beads of the same mass on the other. Set up the respirometer with a manometer linking the test tubes. Leave the apparatus in a water bath. Measure the distance moved by the liquid and calculate the volume of oxygen taken in by minute. Repeat at different temperatures.