Organisms exchnage with their environment Flashcards
Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake
Larger organisms have a smaller surface area to volume ratio
Specialised system overcomes the long diffusion pathway in larger organisms
Describe the relationship between size of an organism and SA:V
As the size of an organism increases, the surface area to volume ratio decreases
Describe the difference between casual and correlation relationship
Correlation - where a change in one of two variables is reflected by a change in another variable - some factors may show a correlation with a disease but there may be no actual evidence to prove it is the cause of the disease
Cause - a factor which directly causes a disease in which there has to be concrete scientific evidence to back it up
Describe the process of expiration in mammals
- When the internal intercostal muscles contract, they pull the ribs downwards and inwards, while the external intercostal muscles relax
- Diaphragm muscle relaxes which moves the diaphragm up into its dome shape
- Both of these actions increase the volume of the thoracic cavity
- Pressure inside the lungs decreases below atmospheric pressure and air enters lungs via a pressure gradient
- Elastic recoil of lung tissue helps to force the air out of the lung during expiration
Describe the adaptations of alveoli as a gas exchange surface
- Shape and large number of alveoli provides a large surface area
- The fluid lining the alveolus allows gases to dissolve and diffuse across
- Only two cell layers that separate blood and air - provides a short diffusion pathway
- Extensive network of blood capillaries surrounding each alveolus provides a large surface area for absorbing oxygen and releasing carbon dioxide
Describe the process of inspiration in mammals
- External intercostal muscles contract - this pulls the ribs upwards and outwards whilst the internal intercostal muscles relax
- Diaphragm muscle contracts which pulls the diaphragm down so it flattens
- Both of these actions increase the volume of the thoracic cavity
- Pressure inside the lungs decreases below atmospheric pressure and air enters lungs via a pressure gradient
Describe the gross structure of the human gas exchange system (lungs)
Consists of a trachea which is supported by incomplete rings of cartilage that prevent it collapsing during the pressure changes which occur in ventilation
Trachea divides into two bronchi that repeatedly divide into smaller tubes, the bronchioles
Alveoli (air sacs) are present at the end of the bronchioles
Describe the adaptations that xerophytes possess for limiting water loss and efficient gas exchange
- Possess thick waxy cuticle - this provides long diffusion pathway which reduces rate of evaporation
- Hairs on the leaf surface trap a layer of still air, this becomes saturated with water vapour which reduces the water potential gradient for water loss
- Rolling up of leaves traps a layer of still air which becomes saturated with water vapour - this reduces the water potential gradient for water loss and therefore, reducing the rate of transpiration
- Reduced surface area to volume ratio of leaves e.g. pine needles reduces the surface area for water loss
Describe the adaptations of leaves of plants for gas exchange
- Leaves are thin, providing a short diffusion pathway
- Respiration and photosynthesis maintain diffusion gradients by using and producing oxygen and carbon dioxide
- Numerous mesophyll cells lining the intercellular air spaces in the leaf provide a large surface area for gaseous exchange
Describe the adaptations of the gills in fish for gas exchange
- Many gill filaments which extend into lamellae provides a large surface area for maximum gas exchange
- A short diffusion pathway is present as the blood and water are separated by a thin barrier of two cell layers, epithelial layer of gill filaments and the endothelial layer of the blood capillaries
- Counter-current system (blood and water flowing in opposite directions) ensures that blood continually meets water with a higher oxygen concentration so that a high diffusion gradient is maintained along the length of the whole lamellae
Describe how anaerobic respiration in insects helps with efficient gas exchange
Lactic acid produced in cells
This lowers the water potential of the cells and some of the water in the ends of the tracheoles move into the cells by osmosis
This enables more air to move in along the tracheoles and into the cells speeding up the diffusion of oxygen to the cells
Describe how body muscles in insects helps with efficient gas exchange
In large / very active insects e.g. bees, their muscles may contract to compress the trachea, forcing air out of them
When the muscles relax, the trachea spring back into shape and fresh air, rich in oxygen is drawn into them
This speeds up the rate of diffusion by creating a diffusion gradient
Describe the basic adaptations of insects for effective gas exchange
Tracheoles are thin - which provides a short diffusion pathway
Numerous tracheoles - which provides a large surface area for maximum diffusion
Describe the gas exchange pathway of insects
Oxygen diffuses from the air, through the spiracles, along the trachea and tracheoles to the cells
Spiracles = tiny holes on the surface of the insect
Trachea and tracheoles = tubes that deliver oxygen to the cells in insects
Describe the adaptations of single-celled organisms for gas exchange
Provides a short diffusion pathway
Which satisfies the gas exchange requirements for small organisms and ensures the removal of heat
Describe how longer-chained fatty acids and monoglycerides are absorbed
Triglycerides are reformed in the epithelial cell
They are then packaged into proteins by the Golgi body to form chylomicrons
Chylomicrons are absorbed into the lacteals (lymphatic vessels) in the villi which eventually drain into the blood
Describe the role of micelles in absorption of lipids
- Micelles contain fatty acids, monoglycerides and bile salts
- Michelles transport poorly soluble fatty acids and monoglycerides to the surface of epithelial cell where they can be absorbed
- Michelles releases the fatty acids and monoglycerides
- Fatty acids/monoglycerides absorbed into epithelial cell by diffusion
- Smaller fatty acid chains diffuse from the epithelial cells directly into the blood
Describe the co-transport mechanism of amino acids and monosaccharides
Sodium ions are actively transported from the ileum cell to the blood
This forms a diffusion gradient for sodium ions to enter cells (and with it glucose)
Glucose enters the blood by facilitated diffusion with sodium ions
Describe the adaptations of the ileum in the small intestine for absorption
It has a large surface area due to its long length and presence of villi and microvilli
Contains blood capillaries that absorb monosaccharides and amino acids therefore, maintaining a high diffusion gradient for further absorption
Lymph vessels (lacteals) in villi absorb digested lipids which also maintains a high diffusion gradient for further absorption
The wall of each villus consists of a single layer of epithelial cells providing a short diffusion pathway for absorption
Describe the hydrolysis of proteins in digestion
Endopeptidases hydrolyse the internal peptide bonds between the amino acids of proteins to form small polypeptides and peptides
Exopeptidases then hydrolyse the terminal (end) peptide bonds at either end of a polypeptide to form a dipeptide
Dipeptidases (membrane-bound enzyme) hydrolyses dipeptides into amino acids
Describe the action of bile salts in the hydrolysis of lipids
Bile salts emulsify lipids causing them to form small droplets
This increases the surface area of lipids which speeds up the hydrolysis by lipase
State some evidence for the mass flow hypothesis
Cutting the stem of a plant results in phloem sap being released indicating hydrostatic pressure in the sieve tubes
Lowering the temperature or the use of respiratory inhibitors reduces the rate of translocation indicating an active transport mechanism is involved
State some evidence against the mass flow hypothesis
Not all solutes move at the same speed, they should do if it is mass flow
In young phloem tissue, substances have been observed moving in opposite directions in the same sieve tube
Describe the use of tracers to show transport in plants
Radioactive substances e.g. mineral ions for xylem or CO2 for phloem are supplied to the leaf on a plant
After a while, you can use autoradiography to detect where the radioactive substances have moved e.g. for showing action of phloem, you will see that the photosynthetic products (radioactive glucose) are in growing regions indicating translocation
