Exchange Flashcards
what are the five characteristics of exchange surfaces?
- large surface area increases rate of exchange
- very thin so short diffusion pathway
- selectively permeable
- movement of environmental medium to maintain a diffusion gradient
- a transport system to maintain a diffusion gradient
how does gas exchange occur within insects?
spiracle > tracheae > tracheoles > to muscles and body tissue
what are three ways in which respiratory gases move in and out of the tracheal system by?
- along a diffusion gradient
- mass transport
- the ends of the tracheoles are filled with water
why are the ends of the tracheoles filled with water?
muscle cells carry out anaerobic respiration, produces lactate which LOWERS water potential.
water in tracheoles decrease in volume and draws air further into them. diffusion is more rapid.
what are the conditions for effective diffusion in insects?
a short diffusion pathway - which is why insects are of such small size.
how does gas exchange occur within fish?
gills > gill filaments > gill lamellae
what is the counter-current exchange principle?
blood and water in opposite directions
diffusion takes place twice
diffusion gradient maintained across entire width of gill lamellae
roughly 80% of oxygen available absorbed
if in same direction, then only 50% of oxygen available would be absorbed (as diffusion gradient would only be maintained across part of the length of the gill lamellae)
what is the structure of a plant leaf?
short, fast diffusion pathway
very large surface area in the air spaces within a leaf
what are leaf adaptations for rapid diffusion?
many stomata
numerous interconnecting air-spaces so that ready contact with mesophyll
large surface area of mesophyll
where can you find stomata?
on the bottom of the leaf, but also a few on the top
what are the adaptations of stomata?
they can open and close to control rate of gaseous exchange as well as conserve water
what are the three adaptations of insects the reduce water loss?
small SA:V ratio - to minimise area where water lost
waterproof coverings - rigid chitin skeleton covered with a waterproof cuticle
spiracles - can be closed to reduce water loss
what are xerophytes?
plants that are adapted to living in areas where water is in short supply
what are five plant adaptations to reduce water loss?
- a thick cuticle
- rolling up of leaves
- hairy leaves
- stomata in pits or grooves
- a reduced SA:V ratio of the leaves
what are the main parts of the human gas exchange system?
lungs > trachea > bronchi > bronchioles > alveoli
what is ventilation?
breathing - when air is constantly moving in and out of the lungs
what is inspiration?
inhalation - when air pressure of the atmosphere is greater than the air pressure inside the lungs, air is forced into the lungs
what is expiration?
exhalation - when the air pressure in the lungs is greater than that of the atmosphere, air is forced out of the lungs
what does the contraction of both sets of intercostal muscles lead to?
internal intercostal muscles - leads to expiration
external intercostal muscles - leads to inspiration
what are the five things that happen during inspiration?
external intercostal muscles contract
ribs upwards and outwards
diaphragm contracts (downwards), increase in volume of thorax
reduction in pressure in lungs
atmospheric pressure now greater than pulmonary pressure, air forced into lungs
what are the five things that happen during expiration?
internal intercostal muscles contract
ribs downwards and inwards
diaphragm relax (upwards), volume of thorax decreases
increase in pressure in lungs
pulmonary pressure now greater than that of the atmosphere, and so air is forced out of the lungs
what are six reasons for diffusion between the alveoli and the blood being rapid?
- rbc slowed as they pass through pulmonary capillaries, allowing more time for diffusion
- distance between the two is reduced
- walls of both alveoli and capillaries are very thin, therefore diffusion distance is short
- alveoli and pulmonary capillaries have a very large total surface area
- steep concentration gradient of gases to be exchanged is maintained
- blood flow through the pulmonary capillaries maintains a concentration gradient
what is the structure of the digestive system?
salivary glands > oesophagus > stomach > ileum (small intestine) > large intestine > rectum
pancreas secretes pancreatic juices
how does physical breakdown occur?
through chewing using teeth
muscles in stomach wall churn the food up
how does chemical breakdown occur?
carried out by enzymes, and they all function by hydrolysis.
carbohydrases hydrolyse carbohydrates
lipases hydrolyse lipids
proteases hydrolyse proteins
what is the process of carbohydrate digestion?
saliva in salivary glands contain amylase
food swallowed, enters stomach, acid denatures amylase + prevents further hydrolysis of starch
small intestines - mixes w/ pancreatic juices which contain pancreatic amylase
continues hydrolysis of any remaining starch to maltose
muscles in the intestine wall push the food along the ileum, epithelial lining produces maltase, a membrane-bound disaccharidase. maltase hydrolyses the maltose from starch breakdown to a-glucose
what do sucrase and lactase hydrolyse?
the single glyosidic bonds in sucrose and lactase molecules
sucrase - makes glucose and fructose
lactase - makes glucose and galactose
how does lipid digestion occur?
hydrolysed by lipases.
found in pancreas
form fatty acids and monoglycerides
lipids split up into micelles by bile salts (produced in liver), called emulsification, increase SA of the lipids so that the action of lipases is speeded up.
how does protein digestion occur?
hydrolysed by peptidases (proteases)
endopeptidases - hydrolyses peptide bonds in the middle
exopeptidases - on the ends
dipeptidases - between two amino acids
what are the properties of villi that increase efficiency of absorption?
- increases SA
- very thin walled, reduces diffusion distance
- contain muscles so can move, maintain diffusion gradients
- well supplied with blood vessels , maintain a diffusion gradient
- epithelial cells lining villi have microvilli, further increases SA
how are amino acids and monosaccharides absorbed?
through diffusion and co-transport
how are triglycerides absorbed?
monoglycerides and fatty acids in combination with bile salts
form micelles
micelles break down, releasing monoglycerides and fatty acids
diffuse into epithelial cells
monoglycerides and fatty acids transported ro the endoplasmic reticulum
recombined to form triglycerides
triglycerides associate with cholesterol and lipoproteins to form chylomicrons
CHYLOMICRONS ADAPTED FOR LIPID TRANSPORT
move out of epithelial cells by exocytosis
enter lymphatic capillaries called lacteals
into blood system via lymphatic vessels
triglycerides in chylomicrons hydrolysed by enzyme in endothelial cells of blood capillaries
