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63 Cards in this Set
- Front
- Back
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What are some things organisms exchange with the environment? |
respiratory gases, nutrients, excretory products, heat |
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How do exchanges take place? |
-Passively by osmosis or diffusion -Actively by active transport |
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How have organisms adapted themselves for exchange? |
-flattened shape so no cell is far from the surface -specialised exchange surfaces with large SA to volume ratio. |
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Characteristics of an exchange surface? |
-large SA to volume ratio -very thing so diffusion distance is shorter -selectively permeable -transport system to ensure movement and to maintain a diffusion gradient |
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What have insects evolved for gas exchange? |
Trachae which are connected to dead end tubes called tracheoles. Short diffusion distance from a tracheole to any respiring cell |
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What are the three ways gases move in and out of the tracheal system? |
-Along diffusion grad.-oxygen at end of tracheoles falls when it is used, which means the oxygen diffuses from atmosphere to end of tracheoles. CO2 grad. in opposite direction -Mass transport- contraction of muscles squeeze trachea -Water at end of tracheoles- during major activity the muscle cells around tracheoles respire anaeroblically producing lactate which is soluble n lowers WP of muscle cells. Water therefore moves into cells by osmosis. This water decreases volume in tracheoles which draws in air further |
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How do gases enter and leave the trachea? |
Through spiracles which can be opened and closed by a valve. Closed spiracles prevents water loss. |
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What is the structure of the gills and how is water moved over them? |
Made up from gill filaments which are stacked up in pile. At right angles to filaments are the lamellae which increase SA of gills. Water is taken in through mouth forced over gills and exit through openings o each side of body. |
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What is countercurrent flow? |
In the gills the water and the blood flow in opposite directions. This is to maximise gas exchange. |
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Why is a countercurrent flow good? |
-Blood that is already well loaded with oxygen meets water with its max. conc. of oxygen so oxygen moves into blood. -Blood w little oxygen meets water thats had most but not all of its oxygen removed so oxygen moves into the blood. |
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How is a leaf adapted for gas exchange? |
-Stomata, no cell is far from stomata so diffusion distance is short. -Air spaces in the mesophyll so gas can readily come into contact with cells. -Large SA of mesophyll cells for faster diffusion. |
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How can stomata control rate of gas exchange? |
They have guard cells surrounding the stomata which can open and close the pore. They are also able to limit water loss thru transpiration. |
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What three adaptions have insects developed to limit water loss? |
1) Small surface area to volume ratio- to minimise areas where water can be lost 2) Waterproof coverings- covering its outer skeleton with chitin which is covered w cuticle 3) Spiracles- can be closed to reduce water loss, but oxygen still needs to be inhaled so they are closed when at rest |
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What are xerophytes? |
Plants that have a limited water supply so adapt to limit water lost from transpiration |
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What are 5 ways that plants can limit water loss? |
1) Thick cuticle 2) Rolling up leaves 3) Hairy leaves 4) Stomata in pits 5) Reduced SA to volume ratio on leaves |
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How does a thick cuticle help reduce water loss? |
Creates a waterproof barrier. |
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How does rolling up leaves help reduce water loss? |
It traps a region of still air in the roll. It becomes saturated with water vapour so has high WP. There is no WP grad. between in and outside of leaf so no water leaves the leaf. |
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How do hairy leaves help reduce water loss? |
Traps still moist air so WP grad. in lowered so less water lost by evaporation. |
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How do stomata being in pits/grooves help reduce water loss? |
They, again, trap still moist air. |
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How does reduced SA to volume ration help reduce water loss? |
Needle leaves instead of broad flat leaves can considerably reduce water loss. It is balanced against need for photosynthesis to meet requirements of the plant. |
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Why is the amount of oxygen that needs to be inhaled and the amount of carbon dioxide exhaled so large in mammals? |
They are large organisms and have a high volume of living cells also they maintain high body temperatures and high metallic and respiratory rates. |
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Why are sites for gas exchange internal in mammals? |
-Air isn't dense enough to support and protect these structures -The body would lose a lot of water and dry out |
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Structure and function of ribcage? |
-Supports and protects lungs and are moved by intercostal muscles -Aid ventillation |
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Structure an function of the lungs? |
-Lobed structures -Made up of branched bronchi and bronchioles |
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Structure and function of Trachea? |
-Flexible airway supported by rings of cartilage, which prevent trachea from collapsing -Made of muscle lined with mucus producing goblet cells and ciliated epithelial cells |
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Structure and function of Bronchi? |
2 Divisions of the Trachea which lead to each lung |
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Structure and function of Bronchioles? |
-Subdivisions of the bronchi and are similarly structured. -Muscles can constrict and control amount of air going into alveoli |
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Structure and function of the Alveoli? |
-Gas exchange surface so has large SA -Air sacs at the end of bronchioles -Between the alveoli there are collagen and elastic fibres which allow them to stretch on inhale. |
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What is inspiration? |
When the air pressure atmosphere is greater than the pressure inside lungs so air in forced in |
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What is expiration? |
When air pressure in the lungs is greater than the pressure in the atmosphere so air is forced out of the lungs |
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Stages of inspiration? |
-External intercostal muscles contract- internals relax -Ribs are pulled upwards which increases thorax volume -Diaphragm muscle contract (flattens) -Increased volume means there is a reduction of pressure in the lungs -Atmospheric pressure is now higher than lungs so air is forced into the lungs. |
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Stages of expiration? |
-Internal intercostal muscles contract- externals relax -Ribs move downwards which decreases thorax volume -Diaphragm muscle relax (pushed up) -Decreased volume means there is an increase of pressure in the lungs -Atmospheric pressure is now lower than lungs so air is forced out the lungs. |
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How do you work out pulmonary ventilation rate? (dm^3 min^-1) |
=tidal volume (dm^3) x breathing rate (min^-1) |
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How does the structure of the alveoli allow efficient gas exchange? |
-Their walls are one cell thick-short diffusion distance -Cell is flattened-short diffusion distance -Each alveolus has a capillary- good blood supply to maintain concentration gradient -RBC are pushed against capillary wall which lengthen diffusion time. -Rounded shape-large SA to volume |
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Define digestion |
Macromolecules are broken down to monomers using physical and chemical processes |
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Define absorption |
Products of digestive are absorbed into the body |
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Define assimilation |
The use of absorbed digestive products to provide energy or materials |
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Define egestion |
Elimination of undigested food molecules |
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What is the oesophagus? |
A tube that carries food from the mouth to the stomach |
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What is the stomach? |
A muscular sac whose inner lining secretes and produces enzymes. Role is to digest food - especially proteins |
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What is the ileum? |
A long tube. Enzymes are produced in its walls which further breaks down the food. The inner walls are folded into villi which gives large SA. Microvilli increase SA furthermore. |
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What is the large intestine? |
Absorbs water. |
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What is the rectum? |
Final section of intestines. Faeces is stored here before being removed by the anus (egestion) |
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What are the salivary glands? |
Near the mouth, they secrete enzymes containing amylase which hydrolyses starch into maltose. |
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What is the pancreas? |
Large gland situated below the stomach. Produces pancreatic juice. This contains proteases, lipase and amylase. |
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Two stages of digestion? |
1) Physical breakdown 2) Chemical breakdown |
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What is physical digestion? |
The food is broken up into smaller pieces by chewing. It increases SA of the food for chemical digestion. |
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What is chemical digestion? |
Where the insoluble macromolecules are converted into their soluble subunits by hydrolysis reactions. Enzymes catalyse these reactions. Carbohydrases hydrolyse carbohydrates into monosaccharides Lipases hydrolyse lipids into glycerol and fatty acids Proteases hydrolyse proteins into amino acids |
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How is carbohydrates broken down in the body? |
1) Saliva enters the mouth through salivary gland. It contains Amylase which hydrolyses starch to maltose 2) Food enters the stomach whose acidic environment denatures amylase and prevents any further hydrolysis of starch 3) Then food travels into the small intestine where it is mixed with pancreatic juice which contains pancreatic amylase which continues to break down any starch. 4) Muscles in the intestine wall push food along ileum, the epithelial wall produces maltase (membrane-bound dissacharide) this breaks down the starch into a-glucose Also: SUCRASE hydrolyses the single glycosidic bond in sucrose molecule producing glucose and fructose. LACTASE hydrolyses the single glycosidic bond in lactose producing glucose and galactose. |
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How are lipids digested? |
They are hydrolysed by lipase. Lipases are produced in the pancreas that hydrolyse the ester bond to form fatty acids and a monoglyceride. Lipids are split up into micelles by bile salts which are produced in the liver. This is called emulsification |
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How are proteins digested? |
They are more complicated and hydrolysed by group of enzymes called peptidases (proteases). |
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What do endopeptidases break down? |
Hydrolyse the peptide bonds between the amino acids in the central region of protein creating a series of peptide molecules. They are secreted by acinar cells of the exocrine tissue in pancreas. Also in the gastric juice in the stomach. |
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What do exopeptidases break down? |
Hydrolyse the peptide bond on the terminal amino acids of the peptide molecules formed by endopeptidases. They release dipeptides and single amino acids. Secreted in the duodenum , e.g. carboxypeptidase A which converts polypeptidases into amino acids. |
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What do dipeptidases break down? |
Hydrolyse the bond between two amino acids of a dipeptide. They are membrane bound |
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How is the pancreatic juice alkali? |
The pancreas secretes hydrogen carbonate ions which make the alkaline conditions. |
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How do villi increase efficiency of absorption? |
-Increase SA for diffusion -Thin walls which reduces diffusion distance -Contain muscle so they can move, this maintains conc. grad. as it mixes contents of the ileum -Good blood supply so blood can carry molecules away to maintain conc. grad. -Microvilli increase SA |
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How are amino acids and monosaccharides absorbed? |
By diffusion, facilitated diffusion, active transport and co-transport. |
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How is diffusion used in absorbing amino acids and monosaccharides? |
As proteins and carbs are digested there is higher conc. of amino acids n glucose in small intestine than the blood. Therefore glucose n amino acids are moved into the blood. |
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When is co-transport used? |
If the conc. of substances is equal on both sides of the intestinal epithelium . Therefore co-transport is used when two molecules move in the same direction at the same time. |
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How is facilitated diffusion and active transport used? |
When glucose and amino acids along with sodium ions are moved from intestinal lumen into blood. This is known as symport which is specialised intrinsic protein found in membrane of epithelial cells. |
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Describe a symport |
1) Sodium ions are actively transported out epithelial cells by sodium-potassium pump into the blood. Takes places on a type of carrier protein on cell surface membrane 2) Maintains high conc. grad. of Na ions in lumen than inside epithelial cells. 3) Na ions diffuse into epithelial cells down conc. grad. thru different carrier-protein. The Na ions carry amino acids or glucose with them. 4) The glucose/ amino acids pass into blood plasma by facilitated diffusion 5) The Na and glucose/AAs move into cell. NA down the conc. grad. but against the glucose and AAs'. It is an indirect form of active transport as the Na's conc. grad. powers the movement of glucose/AA rather than ATP directly. |
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How are triglycerides absorbed? |
The micelles formed come into contact with epithelial cells lining in the lumen and breaks down. It releases the monoglycerides and fatty acids. They diffuse into cells and are transported to the E.R. where they are recombined with triglycerides. At the golgi apparatus, the triglycerides associate with cholesterol n lipoproteins to form structures called chylomicrons. They move out of the cells by exocytosis and enter the lacteals. They are transported into the blood stream by lymphatic vessels. |
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What are Chylomicrons? |
Specialised particles for the transport of lipids. |
