Chapter 6 - Exchange Flashcards
What is usually the immediate environment around cells of multicellular organisms?
Tissue fluid
What is SA:V ratio?
It is the ratio between surface area and volume of an organism. Typically, in larger organisms a higher surface area : volume ratio is preferable as high surface area provides a larger area for the transport of molecules, speeding the process up
How do single celled organisms receive oxygen?
It diffuses across their memebrane from their environment
How do insects receive oxygen?
Insects have tracheae on their surface which are essentially hoes which permeate their body, allowing oxygen to enter and go through their tracheoles before diffusing into the insects cells
How do insects limit water loss whilst still absorbing oxygen?
Insects have flaps on the top of all of their trachea called spiracles which can open or shut, and therefore limit unnecessary water loss
Describe the strucure of a fish gill
A gill fish is made up of filaments, which are branch like structures coming out of a central arch. The filaments are made up of many disc-like structures called lamallae, which contain the pathways between two capillaries, and water goes between the lamellae
What is the counter-current principle?
The counter current principle is the idea that the capillary which starts with poor blood oxygen is on the opposite side of the lamellae to the side which first comes into contact with water. This is so that the side with higher oxygen levels is in contact with the water which also has the highest oxygen level, so that it can still absorb oxygen due to the diffusion gradient
How do plants absorb oxygen and release carbon dioxide?
Through the stomata, which are holes usually found on the bottom of leaves and can be opened and shut by guard cells
When and why do the guard cells open and shut?
The guard cells being open increases water loss by transpiration, therefore the stomata are only open during the day when the plant needs to absorb carbon dioxide for photosynthesis, and they shut during the night or lower light conditions to conserve water
What is the gross structure of the human lungs?
They contain nasal passages which lead to the trachea (the passage into the lungs). The trachea contains lots of cartilidge so that it doesn’t collapse when breathing in, similar to the bronchi which are the offshoots of the trachea leading into each lung. As they continue they become similar and less cartilidge heavy until they split into bronchioles, containing mostly muscular and some elastic tissue. The end of each bronchiole is alveoli, sacks which contain large amounts of capillaries on their outside and are the site of oxygen absorbtion into the blood, and contain lots of elastic tissue
Why are the lungs found inside the body?
The lungs need to be anchored by the ribcage and its assosciated muscles, and humans would lose massive amount of water were the oxygen exchange system found on the outside
What is the mechanism of inhalation?
Inhalation involves the process of the external intercostal muscles contracting as the internal relax, forcing the chest up and out, increasing its volume, as well as the diaphragm contracting, going downwards further decreasing the thorax pressure. This decrease in pressure makes atmospheric pressure higher than the thorax so air rushes into the lungs to stabilise the pressure difference. Inhalation is mostly an active process
What is the mechanism of exhalation?
The internal intercostal muscles contract and the diaphragm relaxes, decreasing the volume of the lungs and therefore increasing pressure, meaning air leaves the lungs. However, most of the expulsive force during regular breathing comes from the elastic tissue returning to its normal position and forcing air up the bronchioles, making exhalation predominantly a passive process (unless during exercise, for example, when muscles are used more and more to speed up breathing)
How are most starch and carbohydrate based compounds broken down in the digestive system?
In the duodenum lots of enzymes are released, including amylase or other relevant carbohydrases which hydrolyse the glycosidic bonds, whilst maltase breaks the glycosidic bonds present in the maltose released from the starch, and then the resultant glucose is absorbed by cotransport
How are proteins digested?
The proteins are initially hydrolysed by both exopeptidases and endopeptidases. The exopeptidases hydrolyse the amino acids from the end of the protein into dipeptides, however endopeptidases hydrolyse the proteins from further into the protein, making two smaller polypeptide chains allowing more exopeptidases to function at once. Dipeptidases then work on the dipeptides resulting in amino acids, which are also absorbed by cotransport
