Back to AI Flashcard MakerAnatomy and Physiology /OCR Biology A - 3.1.1 - Exchange and Transport Part 1
OCR Biology A - 3.1.1 - Exchange and Transport Part 1
This deck covers key concepts related to exchange systems and transport in biology, focusing on factors affecting exchange, features of good exchange surfaces, and adaptations of the lungs.
Factors affecting exchange system
Size SA:V ratio Metabolic activity
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Key Terms
Term
Definition
Factors affecting exchange system
Size SA:V ratio Metabolic activity
How does size affect the need for an exchange system
In single-celled organisms, the cytoplasm is very close to its environment. Diffusion will supply enough O2 and nutrients to keep the cells alive and ...
How does SA:V affect the need for an exchange system
When organisms have a large SA:V their SA is large enough to supply all the cells with sufficient O2 V increases more quickly than SA so the SA:V is s...
How does metabolic activity affect the need for an exchange system
Metabolically active organisms need good supplies of O2 and nutrients to supply energy for movement and warmth so the exchange of substances need to b...
Features of a good exchange surface
Large surface area - achieved by folding walls and membranes Thin, permeable barrier - shorter diffusion distance Good blood supply - maintain steep c...
How are lungs adapted
Many alveoli - large SA:V Thin barrier - short diffusion pathway Good blood supply (capillaries) to carry dissolved gases to and from alveoli Ventilat...
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| Term | Definition |
|---|---|
Factors affecting exchange system | Size SA:V ratio Metabolic activity |
How does size affect the need for an exchange system | In single-celled organisms, the cytoplasm is very close to its environment. Diffusion will supply enough O2 and nutrients to keep the cells alive and active In multicellular organisms have several layers of cells, so there’s a longer diffusion pathway. Diffusion is too slow to enable a sufficient supply to the innermost cells |
How does SA:V affect the need for an exchange system | When organisms have a large SA:V their SA is large enough to supply all the cells with sufficient O2 V increases more quickly than SA so the SA:V is smaller in larger organisms so a specialised exchange surface is needed |
How does metabolic activity affect the need for an exchange system | Metabolically active organisms need good supplies of O2 and nutrients to supply energy for movement and warmth so the exchange of substances need to be efficient |
Features of a good exchange surface | Large surface area - achieved by folding walls and membranes Thin, permeable barrier - shorter diffusion distance Good blood supply - maintain steep concentration gradient (brings molecules to supply side and removes from demand side) |
How are lungs adapted | Many alveoli - large SA:V Thin barrier - short diffusion pathway Good blood supply (capillaries) to carry dissolved gases to and from alveoli Ventilation refreshes air in alveoli Elastic tissue to stretch/ recoil to help expel air |
Function of goblet cells | Produce mucus |
Function of cartilage | Prevent collapse of airways |
Why do the walls of alveoli contain elastic fibres | Expand (inhalation) to increase lung volume Prevent alveoli bursting Elastic fibres recoil |
Inspiration | Diaphragm contracts to move down and become flat. Displaces digestive organs downwards External intercostal muscles contract moving the ribs outward and upward Volume of thorax increases Pressure in thorax < atmospheric pressure Air is drawn in through the nasal passages, trachea, bronchi and bronchioles into lungs |
Thorax | Chest cavity Lined with pleural membranes - space between these membranes is the pleural cavity - usually filled with lubricating fluid |
Expiration | Diaphragm relaxes and is pushed up by displaced organs underneath External intercostal muscles relax and ribs fall Volume of thorax decreases Pressure in thorax > atmospheric pressure Air is moved out of the lungs |
What does the alveoli consist of | Thin, flattened epithelial cells alone with some collagen and elastic fibres |
Elastic recoil | When the elastic fibres in the alveoli return to their resting size, they help squeeze the air out |
What is the inner surface of the alveoli covered in | A thin layer of solution of water, salts and lung surfactant When O2 diffuses out of the alveoli, it first dissolves in the water before diffusing into the blood. Water can also evaporate into the air in the alveoli |
Lung surfactant | Phospholipid that coats the surfaces of the lungs Without it, watery lining of alveoli would have surface tension —> collapse |
Collagen in alveoli | Ensures alveoli aren’t deformed as they stretch (support) |
Distribution and function of capillaries | Over surface of alveoli To provide a large surface area for exchange |
Distribution and function of cartilage | In walls of bronchi and trachea To hold the airways open and provide structural support |
Distribution and function of goblet cells | In ciliated epithelium To produce and release mucus |