Exchange

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What are some examples of tings that need to be inerchanged between organisms and the environment?
1. Respiratory gases 2. Nutirients 3. Excretory products 4. Heat
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What are the 2 ways in which exchanges can take place?
Passively - (no metabolic energy needed) by diffusion and osmosis Actively (metabolic energ is required) by active transport
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What does the surface area have to be like for exchange to be effective?
Exchange surface must be large compared to volume
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What are the features of specialised exchnage surfaces?
1.Large surface area:volume 2.Thin for a short diffusion pathway 3.Selectively permeable to allow selected materials 4.Movement of the environmental medium to maintain a diffusion gradient 5. A transport system to maintain a diffusion gradient
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What is the benefit of single celled organisms being so small?
They have a large surface area to volume ratio
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What is a negative of single celled organisms having such a large surface area?
It conflicts with conserving water.
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What is the internal network that insects have envolved for gas exchange?
Tubes called Trachea
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What makes the trachea so strong?
They are supported by strengthened rings to prevent them for collapsing
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The trachea divide into smaller dead-end tubes called:
Tracheoles
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Tracheoles extend throughout all the bodies tissues of the insect, why is this beneficial in terms of diffusion?
It causes a short diffusion pathway between the atmospheric air and the respiring tissues
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Respiratory gases move in and out the tracheal system in three ways:
1. Along a diffusion gradient 2. Mass Transport 3. The ends of the tracheoles are filled with water
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What is mass transport in insects?
The contraction of muscles in insects can squeeze the trachea, enabling mass movements of air in and out
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What is the diffusion gradient like in an insect? (part1/2)
When cells respire oxygen is used up so concentraion at the end of the tracheoles falls causing a diffusion gradient.
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What is the diffusion gradient like in an insect? (part2/2)
CO2 is produced by cells during respiration creating a diffusion gradient in the opposite direction causing CO2 to diffuse along the tracheoles and trachea from cells to atmosphere
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Why does the ends of tracheoles being filled with water beneficial for exchange in insects? (part1/2)
During periods of major activity muscle cells around tracheoles carry out anaerobic respiration which produces lactate which is soluble and lowers the water potential of the muscle cells from the tracheoles by osmosis.
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Why does the ends of tracheoles being filled with water beneficial for exchange in insects? (part2/2)
This causes the water in the ends of the traceoles to decrease in volume and by doing so draws air further into them. Meaning the final diffusion pathway is in as rather tan liquid and so diffusion is faster
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What are the tiny pores that an insect has that causes gases to enter and leave the trachea called?
Spiracles on the body surface
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What is a negative about spiracles?
They allow there to be water loss
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What do most insects do to prveent water loss?
Keep their spiracles closed
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What are is a feature of a fish that is beneficial for gas exchange?
Waterproof and therefore gas tight outer covering
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What feature of a fish that is not beneficial for gas exchange?
It is large so has a small surface area to volume ratio
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What specialised internal gas exchange system have fish evolved?
Gills
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What are gills made up of?
Gill filaments
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What is the structure of the gill filaments?
They are stacked in a pile
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What are at right angles of the gill filaments?
The gill lamella
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What does the gill lamella provide for effective gas exchange?
Large surface area
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How do fish gain oxygen from the water?
Water is taken in through the mouth and then forced over the gills and out through an opening on each side of the body
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What is countercurrent flow in fish?
Where the flow of water over the gill lamella and the flow of blood within them are in opposite directions
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What is the countercurrent exchange principle in fish? (part 1/2)
The countercurrent flow of the blood and the water means that: 1. Blood that is loaded with oxygen meets water which has its max concentration of oxygen, this causes a diffusion of oxygen from wtaer to blood.
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What is the countercurrent exchange principle in fish? (part 2/2)
2. Blood with little oxygen meets water water which has a lot of its oxygen (but not all) removed so diffusion of oxygen from water to blood takes place.
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What percentage of oxygen in the water is absorbed because of the countercurrent excange principle?
80%
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When would a plant absorb oxygen from the external air and release carbon dioxide?
When photosynthesis is not occurring, for example when it is dark, oxygen will diffuse into the leaf as it is needed for respiration and carbon dioxide will diffuse out as a product of respiration
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In what ways in the gas exchange of a plant the same as that of insects?
1. No living cell is far from external air 2.Diffusion takes place in the gas phase which is more rapid
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Is there a short or large diffusion pathway in a plant?
Short
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What is the surface area to volume ratio like in the spas inside a leaf?
Large surface area compared to volume of living tissue
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Is there a specific transport system for gas exchange in plant?
No gas exchange simply moves through diffusion.
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Where does gaseous exchange happen in a plant?
The leaf
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What adaptations does a leaf have for rapid diffusion?
1. Many small pores called stomata and so no cells is far from stoma so diffusion pathway is short 2. Numerous interconnecting air spaces that occur throughout mesophyll so gas can come in contact with mesophyll quick 3. Large surface area of mesophy
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Which side of the leaf does the stomata mainly occur?
Underside
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What surrounds the stoma?
Guard cells
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What do the guard cells do? (in relation to gaseous exchange)
Open and close the stomatal pore so controlling the rate of gaseous exchange
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Why are guard cells important for terrestrial organisms?
Because these organisms lose water through evaporation so these organisms have adapted to balance water loss by closing stomata at tie=ms when water loss would be excessive
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What is the problem of gaseous exchange in terrestrial organisms?
It is hard to conserve water as it easily evaporates through the body surface
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What adaptations have insects made to conserve water?
1. Small surface area to volume ratio 2.Waterproof coverings of rigid outer skeleton of chitin covered with a waterproof cuticle 3. Spiracles -opening of trachea which can be closed to reduce water loss
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What is the tracheae?
An internal network of tubes found in insects. They carry air containing oxygen directly to the tissues
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Plants cannot have a small surface area to volume ratio, why?
Because photosynthesis requires a large leaf surface area for capture of light and exchange of gases
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How do plants reduce water loss?
They have a waterproof covering and have the ability to close to stomatal pores
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What are xerophytes?
Plants that are adapted to living in areas where water is in short supply
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To prevent water loss, plants make a few modifications. which are?
1. Thick cuticle 2. Rollin up leaves 3. Hairy eaves 4. Stomata in pits 5. Reduced surface area to volume ratio in leaves.
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How do rolled up leaves prevent water loss? (part 1/2)
In most leaves, stomata is confined to lower epidermis, by rolling leaves it protects the lower epidermis from outside, trapping region of air within the leaf. This region becomes saturated with water vapour so has a very high water potential.
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How do rolled up leaves prevent water loss? (part 2/2)
Because of this there is no water potential gardient between the inside and outside of leaf so water cannot diffuse out
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What is an example of a plant that has a thick cuticle?
Holly
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What is an example of a plant that has rolled leaves?
Marram grass
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How does having hairy leaves prevent water loss?
Hairs on lower epidermis traps still, moist air next to the leaf surface. This causes the water potential gradient between the inside and outside of the leaf is reduced so less water is lost.
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What is an example of a plant that has hairy leaves?
Heather plant
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How does the stomata in pits prevent water loss?
It traps moist air next to the leaf and reduces the water potential gradient
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What plant has stomata in pits?
Pine trees
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How does having a small surface area to volume ratio in leaves prevent water loss?
It slows down the rate of diffusion
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What is an example of a plant that's leaves have a small area to volume ratio?
Pine needles
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Why is the volume of carbon dioxide that needs to be removed high and volume of oxygen that needs to be absorbed high in mammals?
1. Large organisms with a large amount of living cells 2.They maintain a high body temperature so have a high metabolic and respiratory rate
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What are the specialised surfaces that mammals have evolved for efficient gas exchange?
Lungs
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What protects the lungs?
Rib cage
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How can the ribs be moved?
The intercostal muscles between them.
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What are the lungs?
A pair of lobed structures made up of a series of branched tubules called bronchioles which end in tiny sacs called alveoli
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What is the trachea?
A flexible airway supported by a ring of cartilages. They prevent the trachea from collapsing as air pressure inside falls.
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What are tracheal walls made up of?
Muscle, lined with ciliated epithelium and goblet cells
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What is the bronchi?
Two divisions of the trachea each leading to one lung.
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What do bronchi and trachea produce to trap dirt particles?
Produce mucus and have cilia that moves dirt laden mucus towards the throat
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What is another similarity between the bronchi and trachea?
They both are supported by cartilages (however the amount of cartilage reduces as bronchi gets smaller)
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What are bronchioles?
Branching sub-divisions of bronchi.
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What are the walls of a bronchiole made of? and what does this allow them to do?
Muscle lined with epithelial cells. This allows them to constrict so that they can control flow of air in and out of the alveoli
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What is the alveoli?
Minute air-sacs with a diameter between 100 and 300μm at the end of bronchioles
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What is between the alveoli?
Collagen and elastic fibres
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What is alveoli lined with?
Epithelium
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What do the elastic fibres between alveoli allow?
Allow alveoli to stretch as they fill with air when breathing in and spring back on breathing out to expel carbon dioxide
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What is the gas exchange surface of a mammal?
Alveolar membrane
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Pressure changes within the lungs are brought about by the movement of three sets of muscles:
1.Diaphragm - a sheet of muscle that separates that separates the thorax from the abdomen 2. Internal intercostal muscles - whose contraction leads to expiration 3. External intercostal muscles - whose contraction leads to inspiration
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Where do the intercostal muscles lie?
Between the ribs
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Is inspiration an active or passive process?
Active as it uses energy
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What is the process of inspiration? (part 1/2)
1. External intercostal muscles contract while the internal relaxes 2. The ribs are pulled upwards and outwards increasing the volume of the thorax 3. The diaphragm muscles contract causing it to flatten which also increases the volume of the thorax
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What is the process of inspiration? (part 2/2)
4.The increased volume of the thorax results in reduction of pressure in the lungs 5. Atmospheric pressure is now greater than pulmonary pressure and so air is forced into the lungs
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Is expiration passive or active?
Passive as it does not require much energy
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What is the process of expiration? (1/3)
1. Internal intercostal muscles contract and external relax 2.Ribs move downwards and inwards decreasing the volume of the thorax
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What is the process of expiration? (2/3)
3. The diaphragm muscles relax so it is pushed up again by the contents of the abdomen that were compressed during inspiration. The volume of the thorax further decreases 4. Decreased volume of the thorax increases the pressure in the lungs
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What is the process of expiration? (3/3)
5. The pulmonary pressure is now greater than atmospheric so air is pushed out of the lungs
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How many alveolis are there in each lung? and what is their total surface area?
300 million and their total surface area is 70m2
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What is each alveolus lined with?
Epithelial cells
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What is around each alveolus?
Network of pulmonary capillaries
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Why is diffusion between alveoli and blood very rapid? (part1/3)
1. Red blood cells are slowed as they pass through pulmonary capillaries allowing more time for diffusion 2. The distance between the alveolar air and red blood cells is reduced s the red blood cells are flattened against the capillary walls
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Why is diffusion between alveoli and blood very rapid? (part2/3)
3. The walls of alveoli and capillaries are thin so there is short pathway for diffusion 4. Alveoli and pulmonary capillaries have a large total surface area
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Why is diffusion between alveoli and blood very rapid? (part3/3)
5. Breathing movements constantly ventilate the lungs and the heart constantly circulates blood around the alveoli which ensures a steep concentration gradient 6. Blood flow through the pulmonary capillaries maintains a concentration gradient
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What is the equation for pulmonary ventilation rate?
PVR (dm3 min-1) = tidal volume (dm3) x breathing rate (min-1)
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What do glands produce?
Enzymes that hydrolyse large molecules into small ones ready for absorbption
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What are the major parts of the digestive system and what do they do? (part1/5)
Oesophagus - carries food from mouth to stomach / Stomach - muscular sac with an inner layer that produces enzymes. Its role is to store and digest food (especially proteins)
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What are the major parts of the digestive system and what do they do? (part2/5)
/ Ileum - long muscular tube. Food is further digested here by enzymes produced by its walls. The walls are folded into villi which gives a larger surface area which is further increased by microvilli on epithelial cells of villi
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What are the major parts of the digestive system and what do they do? (part3/5)
Large intestine - absorbs water / Rectum - final section of intestines. Faces is stored here before being removed by the anus in the process of egestion
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What are the major parts of the digestive system and what do they do? (part4/5)
/ Salivary glands - near the mouth where they pass secretions via the duct in the mouth. Secretions contain amylase which hydrolyzes starch into maltose
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What are the major parts of the digestive system and what do they do? (part5/5)
/ Pancreas - a large gland situated below the stomach which secretes pancreatic juice which contains proteases which hydrolyse proteins to amino acids, lipases which hydrolyses lipids to fatty acids and glycerol, and amylase to hydrolyse starch
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Digestion takes place in 2 stages:
1. Physical breakdown 2. Chemical digestion `
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What is physical breakdown in terms of digestion?
Large food is broken down into smaller pieces by structures such as the teeth and the churning movement of the stomach, this provides a large surface area for chemical digestion
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What is chemical digestion?
Chemical digestion hydrolyses large, insoluble molecules into small soluble ones. It is carried out by enzymes.
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Enzymes work by hydrolysis. What is hydrolysis?
Splitting up of molecules by adding water to chemical bonds
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Enzymes are specific what does this mean?
They only hydrolyse one type of product
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What are the 3 digestive enzymes that are really important?
1. Carbohydrases - hydrolyse carbohydrates leading to monosaccharides 2. Proteases - hydrolyse proteins to amino acids 3. Lipases - hydrolyses lipids to fatty acids and glycerol
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What is the process of carbohydrate digestion? (part1/3)
1. Salivary amylase produced in the mouth hydrolyses glycosidic bonds of starch molecule to produce maltose. At neutral pH 2 Food is swallowed & enters acidic conditions in stomach which causes amylase to denature
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What is the process of carbohydrate digestion? (part2/3)
3. Food is then passed into small intestine where it mixes with pancreatic juices which contains amylase which keeps hydrolysis starch into maltose. The alkaline salts in the pancreas creates an neutral pH for amylase to work again.
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What is the process of carbohydrate digestion? (part3/3)
4. Muscles in intestine wall push food along the ileum. The lining of the ileum produces maltase which is a membrane bound disaccharide that hydrolyses maltose from starch into alpha glucose
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Apart from maltase there are 2 other disaccharides:
Lactose and sucrose
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Where is lactose and sucrose found?
Lactose - milk Sucrose - fruit
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How is lactose and sucrose disaccharides hydrolysed?
Sucrose - sucrase hydrolyses the single glycosidic bond in sucrose which produces 2 monosaccharides: glucose & fructose Lactose - lactase hydrolyses the single glycosidic bond in lactose to produce 2 monosaccharides: glucose and galatacose
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Where is lipase produced?
Pancreas
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What does a lipase hydrolyse?
The diester bond found in triglycerides to form fatty acids and monoglycerides (a glycerol molecule with a fatty acid molecule attached)
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Lipids are firstly split up into tiny droplets called: and how are they split up?
Micelles by bile salts (emulsification, which increases the surface area of lipid so action of the enzyme is faster)
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Where are bile salts produced?
Liver
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Proteins are large molecules that are hydrolyses by a group of enzymes called peptidases. What are the different peptidases called and what do they do? (part1/2)
1. Endopeptidase - hydrolyse peptide bonds between amino acids in centre of protein forming peptide molecules 2. Exopeptidases - hydrolyses peptide bonds on the terminal amino acids of peptide molecules releasing dipeptides & single amino acids
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Proteins are large molecules that are hydrolyses by a group of enzymes called peptidases. What are the different peptidases called and what do they do? (part 2/2)
3. Dipeptidases - hydrolyse bond between 2 amino acids of a dipeptide. Dipeptidases are membrane bound as they are part of the cell surface membrane of epithelial cells lining the ileum
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Ileum is structured for absorbing products of digestion. Walls of ileum posses villi. Where exactly are they situated?
At the interface between the lumen of the intestines and the blood and other tissues of the body
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Villis properties increase efficiency of absorption by: (part 1/2)
1. Increase surface area for diffusion 2. Thin walled for short diffusion pathway 3. They contain muscles so are able to move which helps maintain diffusion gradient 4. Well supplied with blood vessels to carry away absorbed materials maintaining
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Villis properties increase efficiency of absorption by: (part 2/2)
a diffusion gradient 5. Epithelial cells of villi posses microvilli that further increase surface area
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Card 2

Front

What are the 2 ways in which exchanges can take place?

Back

Passively - (no metabolic energy needed) by diffusion and osmosis Actively (metabolic energ is required) by active transport

Card 3

Front

What does the surface area have to be like for exchange to be effective?

Back

Preview of the front of card 3

Card 4

Front

What are the features of specialised exchnage surfaces?

Back

Preview of the front of card 4

Card 5

Front

What is the benefit of single celled organisms being so small?

Back

Preview of the front of card 5
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