exchange- chapter 6 Flashcards
what is tissue fluid
the environment around the cells of multicellular organisms
why are mass transport systems needed
-to maintain diffusion gradients and bring materials to and from the cell-surface membranes
-this is because majority of cells are two far from exchange surfaces for diffusion to be enough to keep the composition relatively constant
what affects the amount of material that’s exchanged
the size and metabolic rate of
what does a high metabolic rate=
a larger surface area to volume ratio
4 examples of what needs to be exchanged
-respiratory gases
-nutrients
-excretory products
-heat
except for heat how are exchanges done
passively (diffusion and osmosis) and actively (active transport)
how to small organisms exchange efficiently across their body surface
they have a surface area that is large enough compared with their volume
what happens as organisms get larger (SA)
their volume increases at a faster rate than surface area
how do organisms over come meeting the needs of exchange in large organisms
flattened shape of specialised exchange surfaces with large area to increase surface area to volume ratio (lungs)
5 features of specialised exchange surfaces
- large surface area relative to volume
- very thin which decreases the diffusion decreases
- selectively permeable to allow selected materials to cross
- movement of the environment medium i.e air to maintain a diffusion gradient
- a transport system to ensure the movement of the internal medium i.e blood in order to maintain a diffusion gradient
how is oxygen absorbed in single celled organisms
absorbed by diffusion across the body surface
what are the internal networks of tubes called in insects
tracheae
how are the trachea supported
by strengthened rings to prevent them from collapsing
what does the tracheae divide into
smaller dead end tubes called tracheoles
where do the tracheoles extend to
throughout all the body tissues of an insect
what do spiracles do
tiny pores where gas enters and leaves the tracheae
what are the 3 ways respiratory gases move in and out of the tracheal system
- along a concentration gradient
- mass transport
- ends of tracheoles are filled with water
how do respiratory gases move in/out tracheal system by mass transport
contraction of muscles in insects can squeeze the trachea enabling mass movements of air in and out of the
how do respiratory gases move in/out of the tracheal system along a concentration gradient
low concentration at the ends of the tracheoles
how do respiratory gases move in/out of the tracheal system by the ends of tracheoles being filled with water
-major activities results in anaerobic respiration whcih produces lactate, which is soluble and lowers the water potential of the muscle cells
-water therefore moves into the cells by osmosis
-the water in the ends decreases in volume and draw air further in
3 facts about fish’s
-waterproofing and gas tight outer covering
-small surface area to volume ratio
-body surface is not adequate to supply and remove their respiratory gases
where are the gills found
behind the head of a fish
what are gills made up of
gill filaments
where are the gill lamellea found
right angles to the fillaments
what do gill lamellea do
increase the surface area of the gills
what is countercurrent flow is fish
when the flow of water over the gill lamellea and the flow of blood within them are in opposite direction
what happens when water is taken in through the mouth in a fish
its forced over the gill and out through an opening in the side of their body
what does countercurrent flow maximise
so the maximum possible gas exchange is achieved
how does the counter current exchange principle allow 80% of oxygen to be removed
- blood that is already well loaded with oxygen meets water, whcih has maximum concentration of oxygen. diffusion takes place
- blood with little oxygen meets water which has had most of its oxygen removed. diffusion takes place
what is the structure of a plant leaf and gas exchange
-no living cell is far from the external air
-diffusion takes place in the air, which means it is rapid
what is the diffusion pathway life in a plant leaf
short and rapid diffusion pathway
why is it good that leave have many small pores (stomata’s)
so no cell is far from the stomata, which makes the diffusion pathway short
why is it goof that leaves have meant numerous interconnecting air-spaces
they occur through the mesophyll so that gases can readily come into contact with mesophyll cells, increases surface area
why is it good that leaves have a large surface area of mesophyll cells
rapid diffusion
what is the stomata
minute pores that occours mainly on the leaves (especially underneath)
what is each stoma surrounded by
guard cells which can open and close the stomatal pore
what do guard cells control
the rate of gaseous exchange which is important as it also controls the amount of water loss
what does a small surface area to volume ratio limit in insects
-water loss
-minimises the area over which water is lost
what are 2 features of limiting water loss in insects
-waterproof coatings on their body
-spiracles which are the opening of the trachea at the body surface which can be closed to reduce water loss
what are xerophytes
plants that have a restricted supply or water so have evolved a range of adaptations to limit the water loss
how does a thick cuticle limit water loss
reduces the amount of water that can escape
how does rolling up of leaves reduce water loss
this traps the region of still air which becomes saturated with water vapour and so has a high water potential, this is no water potential gradient so no water loss
how do hairy leaves limit water loss
traps still and moist air next to the leaf surface, water potential gradient between inside and outside the leaf is reduced so less water is lost
how to stomata’s in pits or grooves limit water loss in plants
works by trapping moist, still air
what are the 5 ways to limit water loss in plants
- thick cuticle
- rolling up of leaves
- hairy leaves
- stomata in pits or grooves
- a reduced surface area to volume ration of leaves
what are the lungs supported+protected by
the ribcage
how are the ribs moved
by the muscles inbetween them
what are the 5 main parts of the gas exchange system
lungs, trachea, bronchi, bronchioles and alveoli
what are the lungs ventialted
by a tidal stream of air
explain the lungs as its role in a gas exchange system
pair of lobed structures made up of a series of highly branched tubules called bronchioles and end in alveoli
explain the trachea as its role in a gas exchange system
flexible airway that is supported by ring of cartilage, this prevents the trachea collapsing. The tracheal walls are made up of muscle, lined with ciliated epithelium and goblet cells
explain the bronchi as its role in a gas exchange system
two division of the trachea which are a similar structure to the trachea and they produce mucus to trap dirt particles and have cilia that move the dirt laden mucus towards the throat. Larger bronchi are supported by cartilage
explain the bronchioles as its role in a gas exchange system
series of branching subdivisions of the bronchi. Walls are made of muscle lined with epithelial cells. This muscle allows them to constrict so that they can control the flow of air in and out of the alveoli
explain the alveoli as its role in a gas exchange system
minute air-sacs with a diameter of 100um to 300um. Between the alveoli there is some collagen and elastic fibres. The alveoli are lined with epithelium. Elastic fibres allow the alveoli to stretch and they fill with air and spring back when breathing out
why is the diffusion of gases between the alveoli and the blood will be very rapid
1.Red blood cells are slowed as they pass through, allowing more time.
2.Distance between alveolar air and red blood cells is reduced as the red blood cells are flattened against the capillary walls.
3.The walls are very thin- short distance for diffusion.
4.Alveoli and pulmonary capillaries have a very large total surface area.
5.Breathing movements constantly ventilate the lungs and the action of the heart constantly circulate blood around the alveoli. Constant steep constant gradient.
6.Blood flow maintains concentration gradient
why is the volume of oxygen that has to be absorbed and the volume of carbon dioxide that has to be removed is large in mammals because of what?
-they are relatively large organisms with a large volume of living cells
-maintain a high body temperature which is related to a high metabolic and respiratory rates
explain inspiration
-The external intercostal muscles contract, while the internal intercostal muscles relax.
-The ribs are pulled upwards and outwards, increasing the volume of the thorax.
-The diaphragm muscles contract, causing it to flatten, which also increases the volume of the thorax.
-The increased volume of the thorax results in reduction of pressure in the lungs.
-Atmospheric pressure is now greater than pulmonary pressure and so air is forced into the lungs
explain expiration
-The internal intercostal muscles contract, while the external intercostal muscles relax.
-The ribs move downwards and inwards, decreasing the volume of the thorax.
-The diaphragm muscles relax and so it is pushed up again by the contents of the abdomen that were compressed during inspiration. The volume of the thorax is therefore further decreased.
-The decreased volume of the thorax increases the pressure in the lungs.
-The pulmonary pressure is now greater than that of the atmosphere, and so air is forced out of the lungs.
During normal quiet breathing, the recoil of the elastic tissue in the lungs is the main cause of air being forced out
what is the role of oesophagus
carries food from the mouth to the stomach
what is the role of the stomach
muscular sac that produces enzymes in glands. It stores and digests food especially proteins
what is role of the ileum
long muscular tube where food is further digested by enzymes that are produced by its walls and by glands. Inner walls are folded into villi which that have millions of tiny projections called microvilli, this increases the surface area. Products of digestion are absorbed into the blood stream in the Ileum
what is the role of the large intestine
absorbs water, a lot of this is from the secretions of the many digestive glands
what is the role of the rectum
final section where the faeces are stored before being removed via the anus in a process called egestion
what is the role of the salivary glands
pass their secretions which contain the enzyme amylase which hydrolyses starch into maltose
what is the role of the pancreas
large gland that produces a secretion called pancreatic juice, this contains proteases, lipase and amylase
describe physical digestion
-Food is broken down into smaller pieces by means of structures such as the teeth.
-This provides a larger surface area for chemical digestion.
-Food is churned by stomach muscles which also physically digests the food
describe chemical digestion
-Hydrolyses large, insoluble molecules into smaller soluble ones.
-Usually one enzyme hydrolyses a large molecule into sections, these are then hydrolysed into small molecules by one or more additional enzymes
describe carbohydrate digestion
-Amylase is produced in the mouth and the pancreas. This hydrolyses the alternate glycosidic bonds of the starch molecule to produce the disaccharide maltose.
-Maltose is then hydrolysed into the monosaccharide a-glucose by a second enzyme called maltase which is produced by the lining of the ileum
what is the carbohydrate digestion process
- Saliva enters the mouth from the salivary glands which contains salivary amylase. This starts hydrolysing any starch into maltose. It also contains mineral salts that help maintain the pH around neutral.
- Food is swallowed and enters the stomach, the acid denatures the amylase.
- Food is then passed into the small intestine where is mixes with pancreatic juice which contains pancreatic amylase, this continues to hydrolyse any remaining maltose. Alkaline salts produced by both the pancreas and the intestinal wall maintains the pH at around neutral.
- Muscles in the intestine wall push the food along the ileum. It’s epithelial lining produces the disaccharidase maltase (membrane-bound disaccharidase). The maltase hydrolyses the maltose from starch breakdown into a-glucose
what does sucrose hydrolyse
the single glycosidic bond in the sucrose molecule. This hydrolysis produces the two monosaccharides glucose and fructose.
what does lactase hydrolyse
the single glycosidic bond in the lactose molecule. This hydrolysis produces the two monosaccharides glucose and galactose
explain lipid digestion
-Lipases are enzymes produced in the pancreas that hydrolyse the ester bond found in triglycerides to form fatty acids and monoglycerides.
-Lipids are firstly split up into tiny droplets called micelles by bile salts produced by the liver. This is called emulsification and increases the surface area of the lipids
explain how proteins are digested
Proteins are large complex molecules that are hydrolysed by a group of enzymes called peptidases
explain endopeptidases
hydrolyse the peptide bonds between amino acids in the central region of a protein molecule forming a series of peptide molecules
explain exopeptidases
hydrolyse the peptide bonds on the end amino acids of the peptide molecules formed by endopeptidases
explain dipeptidases
hydrolyse the bond between the two amino acids of a dipeptide. Depeptidises are membrane-bound
explain the absorption of trigylcerides
- Monoglycerides and fatty acids remain with the bile salts that emulsified the lipid droplets. Micelles which are around 4-7nm in diameter.
- Movement of materials in the lumen of the ileum means the micelles come into contact with the lining of the villi of the ileum.
- Micelles break down releasing the monoglycerides and fatty acids.
These are non-polar so easily diffuse across the cell-surface membrane into the epithelial cells. - Once inside the epithelial cells, monoglycerides and fatty acids are transported to the ER where they reform triglycerides.
- Moving to the golgi apparatus the triglycerides associate with cholesterol and lipoproteins to form chylomicrons, which are special particles adapted for the transport of lipids.
- Chylomicrons move out of the epithelial cells by exocytosis.
7.They enter lymphatic capillaries called lacteals. They then pass into the blood system.
8.The triglycerides in the chylomicrons are hydrolysed by an enzyme in the endothelial cells of blood capillaries from where they diffuse into cells
what does the digestion of proteins produce
amino acids
what does the digestion of carbohydrates produce
monosaccharides such as glucose, fructose and galactose
what are the monosaccharides from carbohydrates and amino acids from proteins absorbed through
diffusion and co-transport
what is the structure of the ileum
-They increase the surface area for diffusion
-Very thin walled- reducing the distance over which diffusion takes place
-Contain muscle and so are able to move. This mixes the contents of the ileum ensuring that as the products of digestion are absorbed the new material rich with products of digestion replaces it.
-Well supplied with blood vessels maintain the diffusion gradient.
-Epithelial cells lining the villi possess microvilli which increase the surface area for absorption
