Exchange systems Flashcards
Surface area and size
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What does objects surface area to volume ratio describe?
Its a way to describe how close every internal part of it is
How do you work out an objects surface area to volume ratio?
SA:V ration = Surface area/volume
What does a high Surface area to Volume ratio show?
Shows that every part of the object is close to the edge
Means there is only a short distance from the edge to the middle - things can get in and out quickly
What does a low Surface area to Volume ratio show?
Means that there are parts of an object that are a long way from the edge
Means there is a longer distance from the edge to the middle - takes things a long time to get in and out
What do all organisms need to do in order to survive?
Exchange substances with the environment
Take in oxygen and nutrients and remove carbon dioxide and urea
What needs to be kept constant in organisms?
Temperature and water levels
Heat and water also need to be exchanged due to this
Without calculating the S.A:Vol ratio how can you compare them?
Can think about shape and size
In terms of organisms the larger the organism the lower the S.A:Vol ratio becomes
What is an organisms metabolic rate?
The amount of energy expended by that organism in a time period - usually daily
What is the metabolic demand in organisms?
How much oxygen and nutrients an organism needs to take in daily to respire enough to maintain the metabolic rate
What makes a organisms metabolic rate higher?
Having a greater mass - as the organism with high metabolic rates require more more efficient delivery of oxygen to cells since more respiration is necessary
What does the more efficient need of oxygen and nutrients lead to?
Multicellular organisms have evolved more complex mass transport and exchange systems
What does the rate of exchange of substances depend on?
The surface area in contact with the surroundings
What do larger organisms struggle with due to their smaller S.A:Vol ratio?
Have more difficulty in getting oxygen and nutrients they need from the environment
What do unicellular organisms have?
- Large SA:Vol ratio - surface area so large enough to absorb required substances
-Short diffusion distance - to get from outside to the centre of the cell - diffusion from environment is fast
What are the advantages and disadvantages of the aspects of a unicellular organism?
Adv - can exchange materials directly with their environment as all of the cell has surface exposed to the outside
Dis - Lose heat energy and water quickly, cannot survive extreme heat or cold
What to multicellular organisms have?
- Small SA:Vol ratio - cannot absorb enough substances to supply large volume through small outer surface
- Large diffusion distance - from outside to all cells in the centre of the organism so diffusion through outer surface is too slow to supply cells efficiently
What are the advantages and disadvantages of the aspects of multicellular organism?
Adv -Lose less energy as heat, so can survive more easily in cold environments
Dis - some cells will have no surfaces exposed to the outside so need internal mass transport systems.
In hot environments need adaptations to cool down
Why do small animals have a lower metabolic rate?
Have a greater SA:Vol ratio but lose heat more easily
Means more energy is needed and a higher metabolic rate to maintain a constant internal temperature
Per unit of body mass metabolic rate do larger animals or smaller animals have a higher rate?
Smaller animals is higher than larger animals
Why do organisms evolve?
To develop adaptations to increase or decrease their surface area to match their metabolic demands
Means organisms with similar volumes in different environments may need to adapt to have different surface areas
What challenge would animals face in a cold environment
Heat loss
Behavioural adaptations animals may make in a cold environment
Small mammals with large SA:Vol will lose heat easily so they need to eat large amounts of high energy foods (e.g nuts and seeds) to help maintain body temperature. Also hibernate during the coldest months
Physical adaptations animals may make in a cold environment
Adapted animals will have a streamlined, compact body shape giving a smaller SA:Vol ratio
Small mammals with larger SA:Vol may have thick layers of fur zoo insulate and reduce heat loss
E.g Artic fox - small ears, round head - reduce SA:Vol
What challenge would animals face in a hot environment/desert?
Overheating
Behavioural adaptations animals may make in a hot environment/desert?
Large organisms e.g hippos spend much of the day in water to help loose heat
Organisms may be nocturnal so they are most active in cooler temperatures
Physical adaptations animals may make in a hot environment/desert?
Large organisms with low SA:Vol often have large ears to increase surface area allowing more heat loss e.g elephants
E.g African bat-eared fox - large ear, more pointed nose to increase SA:Vol and heat loss
What challenge would animals face in a hot/dry desert
Water loss
Behavioural adaptations animals may make in a hot/dry desert
Organisms may be nocturnal so they are most active in cooler temperatures
Physical adaptations animals may make in a hot/dry desert
Small animals with a high SA:Vol have kidney structure adaptations so that they produce less urine to compensate for water lost through evaporation
Digestive and absorption of carbohydrates
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During digestion what do a series of enzymes do?
They hydrolyse large insoluble molecules (e.g. proteins) into smaller soluble ones (e.g. amino acids)
What does changing them to be smaller soluble molecules enable?
Can be absorbed into the blood so it can be transported around the body and used
Where does the absorption of nutrients occur?
Small intestine which has particular features to maximise the movement of substances through cells into the blood
What are the features that the small intestine have to maximise the movement of substances?
Internal walls are folded into projections called villi (~1mm in length)
Villi have thin walls (1 cell thick) to help keep the diffusion pathway short
Villi have lots of capillaries to help maintain the concentration gradient by constantly transporting absorbed nutrients away
Villi contain muscles and can move which helps them to mix in the contents of the ileum so that villi always have new material next to them to absorb nutrients. Help maintain the concentration gradient
What adaptations to epithelial cells (line the ileum) have for efficient digestion?
Microvilli (folded membrane) which increase the surface area for diffusion further
Many mitochondria to provide energy for active transport
Carrier proteins for active transport
Channel proteins for facilitated diffusion
Since enzymes are specific to one substrate what are some responsible for?
Responsible for breaking down polymers into sections which then require another enzyme to break them down further into their monomers
Where are the different enzymes made for digestion?
Made in different organs of the digestive system and are released to mix with food in different places
What do epithelial cells have?
Enzymes in their membranes to help (membrane bound enzymes) and also carrier proteins for specific proteins
What does the salivary gland produce to help in digestion?
Produces - Amylase enzyme in saliva (mouth)
Helps digest - Breaks glycosidic bonds in starch to form maltose
What does the pancreas produce to help in digestion?
Produces - Pancreatic amylase released into the small intestine
Helps digest - Breaks glycosidic bonds to hydrolyse starch to form maltose
What does the small intestine (ileum) produce to help in digestion?
Produces - Membrane bound disaccharides in cell membrane of epithelial cells
Helps digest -Breaks glycosidic bonds to hydrolyse disaccharides into monosaccharides e.g. sucrase catalyses breakdown of sucrose into glucose and fructose
What are the three membrane-bound disaccharides?
Maltase, Sucrase, Lactase
When the monosaccharides products are small enough to be transported across what?
The epithelial cell membrane through specific transporter proteins
How are glucose and galactose transported into cells?
Active transport using sodium ions through co-transporter transports
How is fructose transported into cells?
Absorbed by facilitated diffusion through a different transporter protein
Digestive and absorption of proteins
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What are peptidase and protease?
They are enzymes which breakdown proteins in a series of hydrolysis reactions
Where does protein digestion occur?
In the small intestine and the stomach
What creates the optimum pH in the stomach and what for?
Hydrochloric acid, for the enzyme pepsin which is secreted by cells which line the stomach
Where are other peptidase made and secreted?
By the pancreas into the small intestine (e.g. trypsin)
Others are membrane-bound and found within cells that line the small intestine (e.g. dipeptidases)
How are single amino acids absorbed into the blood?
Through the ileum epithelium
What is the process of proteins being absorbed into the bloodstream?
Stomach:
- Whole proteins are chewed and swallowed into the stomach
- Hydrochloric acid denatures proteins, unfolding their 3D structure to reveal the polypeptide chain
- Enzymatic by pepsin forms shorter polypeptides
Small intestine:
- In the small intestine, trypsin, chymotrypsin & protease continue enzymatic digestion, forming tripeptides, dipeptides, and amino acids
- In enterocytes, tripeptides and dipeptides are further broken down into amino acids, which are absorbed into blood
Bloodstream
What are the three different types of protease enzyme?
Endopeptidases
Exopeptidases
Dipeptidases
What do the protease enzymes do?
They each work on breaking different sections of proteins.
Either the internal bonds, terminal bonds or single peptide bonds holding dipeptides together
What does the enzyme endopeptidases do?
Internal
Hydrolyse peptide bonds within a large protein (polypeptide) to create smaller polypeptide chains
Endopeptidases create more terminal ends for exopeptidases to then work out
Digest internal peptide bonds
What does the enzyme exopeptidases do?
External
Hydrolyse terminal peptide bonds (between amino acids on the ends of a polypeptide chain) to remove individual amino acids and create smaller polypeptide chains
Digest terminal peptide bonds to release amino acids
What does the enzyme dipeptidases do?
A type of exopeptidase. These often are located on the membrane of epithelial cells lining the small intestine.
They work specifically on dipeptides to hydrolyse the peptide bond holding them together. This creates two single amino acids which can be transported through the membrane into the epithelial cells.
Diffuse toward membrane and bind to dipeptidase, dipeptides are hydrolysed into two amino acids pass into cytoplasm
How are amino acids absorbed?
Absorbed in a similar way to glucose and galactose, through active co-transport with sodium ions.
Sodium ions are actively transported out of ileum cells so that they diffuse back in down their concentration gradient with amino acids
Digestive and absorption of lipids
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What are lipases?
Enzymes which hydrolyse the ester bonds in triglycerides to form fatty acids and monoglycerides
Where are lipases made and secreted from?
Made in the pancreas and secreted into the small intestine
Where is bile salt produced and stored?
Produced in the liver
Stored in the gall bladder which are then released into the small intestine
What do bile salts do?
Help to break down large fat globules by emulsifying them into smaller droplets
This helps to speed up the action of lipase by increasing the surface area of lipids that can be exposed to the enzyme
What are micelles and how are they formed?
Formed once the lipid has been broken down by lipase the monoglycerides and the fatty acids stay attached to the bile salts and form smaller structures
(4-7nm wide) - helps in the absorption of fatty acids and monoglycerides into the blood stream
What is the first step in lipid absorption?
Micelles hit epithelial cells and breakdown allowing monoglycerides and fatty acids to diffuse across membrane because they are lipid soluble
What is the second step in lipid absorption?
Monoglycerides and fatty acids are transported to the ER where they recombine to form triglycerides again
What is the third step in lipid absorption?
Inside the golgi they bind with cholesterol and proteins and are packaged to form chylomicrons
What is the fourth step in lipid absorption?
Chylomicrons travel in a vesicle to the cell membrane and are exocytosed from epithelial cell
What is the fifth step in lipid absorption?
Chylomicrons enter lymphatic capillaries called lacteals which transport them away from the small intestine to adipose, cardiac, and skeletal muscle tissue, where the triglycerides can be hydrolysed and fatty acids used by the tissues.
Gas exchange in insects
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How have insects evolved to live on land?
Those that have evolved have microscopic air-filled piped called trachea
What does the trachea divide into?
Divide into smaller tubes called tracheoles which then continue to divide until they penetrate into individual body cells
Means that gases are directly exchanged between cells and the atmosphere - no need to transport them
How does air enter and leave the trachea?
Enters through pores on the surface of the exoskeleton called spiracles
CO2 and O2 will diffuse in/out of the spiracles down their concentration gradient
How do tracheoles having thin walls increase diffusion?
It shortens the diffusion distance of gases to cells
How do tracheoles being highly branched increase diffusion?
It increases the surface area for gas exchange
How does the fluid in the ends of the trachea where it joins tissue increase diffusion?
Gas exchange from air to liquid occurs in the tracheole which allows gases to diffuse to tissues faster
Tracheal fluid can be withdrawn into the body fluid to increase the surface area of the tracheole exposed to air
How do muscles that can pump the body and force air in/out increase diffusion?
It maintains the concentration gradient for gases
How does the fact that spiracles can be closed/not open all the time diffusion?
It prevents water loss - keeps organisms waterproof
How does ventilation occur in the insect?
Through contracting muscles between each body segment, the insect can compress the trachea and so pump gases in and out its body
What does the pumping of muscles do in ventilation?
Pumping raises pressure in the body and forces air out of the spiracles down the pressure gradient.
This can be done to increase the removal of CO2 when energy demands increase and respiration levels are highest (e.g during intense movement)
Gas exchange in fish
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What is each gill made up of and attached to?
Made up of thin plates called filaments which are attached to a bony gill arch - create a large surface area for water to flow
What are the gill filaments covered in?
Covered in lots of tiny folds called lamella which further increase the surface area of the gills
What do the lamella contain?
Have lots of blood capillaries and a thin layer of cells
Where does gas exchange happen?
Gas exchange happens in the lamellae
Water flows over them in an opposite direction to the blood
What is a concurrent flow?
Water and blood flow over and through the lamellae in the same direction
At first there is a large concentration gradient - water has a much higher O2 concentration, so diffusion occurs
As they flow along the lamellae the concentration gradient decreases until equilibrium - no more O2 diffuses into the blood
Less O2 would be absorbed into the blood overall - diffusion only happens in the first part of the lamellae
What is a countercurrent flow?
Water and blood flow over and through the lamellae in opposite directions to each other
Blood always flows next to water that has a higher oxygen concentration, so diffusion happens along the full length of the lamellae
The blood absorbs more and more O2 as it moves along
Even when the blood is highly saturated there is still a concentration gradient so more O2 can flow into the blood overall
How do thin epithelium/walls of lamellae increase diffusion?
It shortens the diffusion distance of gases from water to blood
How does there being a large number of filaments and lamellae increase diffusion?
It increases the surface area for gas exchange
How does the countercurrent flow system increase diffusion?
It maintains the concentration gradient as water is always next to blood with a lower concentration of oxygen
How does there being a large number of capillaries around the lamellae increase diffusion?
Circulation constantly removes oxygenated blood to maintain steep concentration gradient
How does the ventilation by the operculum increase diffusion?
This ensures constant fresh water flow over gills to replace lost oxygen and maintain a steep concentration gradient
What are the internal gills protected by?
They are protected by an operculum and therefore need to be actively ventilated
Where do fish take in water?
Take in water through its buccal cavity - then flows through the pharynx - then over the gill plates - leaving via the operculum on the sides of the fishes head
What are the lamellae supported by?
They are kept supported an moist by the water that is continuously pumped through the mouth and over the gills
Also ensures fresh water with O2 is always passing over the gills to maintain the concentration gradient as O2 diffuses into the blood
What are the steps of ventilation?
- Mouth open, operculum shuts
- Water enters cavity due to decreased pressure / increased volume
- Mouth closes, operculum opens
- Results in increased pressure/decreased volume
- Increased pressure forces water out over gills
Gas exchange in humans
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Where does gas exchange occur in mammals?
Takes place in the lungs - the alveoli
How are the lungs adapted?
Highly adapted to have a very large surface area in contact with the bloodstream to sustain a high rate of gas exchanged required to maintain a high metabolic rate
How does air travel to where gas exchange occurs?
Air flows in through the mouth and nose then down the trachea. The trachea then splits into two bronchi which branch off further into smaller tubes known as bronchioles. Bronchioles end in small air sacs known as alveoli. Alveoli are surrounded by capillaries; this is where gas exchanged required takes place.
What is each lung surrounded by and what does it do?
Surrounded by a membrane and the space (pleural cavity) is filed with pleural fluid
Lubricates the lungs and helps the lungs adhere to the walls of the thoracic cavity by water cohesion. Allows the lungs to expand with the chest during inhalation
Where is cartilage found in the lungs?
In the trachea and bronchus
What is the function of cartilage in the lungs?
Provides strength to trachea and bronchus, holds the airway open - prevents collapse of airway when air pressure falls
Where is surfactant found in the lungs?
Coats the surface of lungs
What is the function of surfactant in the lungs?
Phospholipid bilayer which maintains moisture but reduced the surface tension to stop alveoli collapsing when the air pressure falls
Where is smooth muscle found in the lungs?
Lining trachea - bronchioles
What is the function of smooth muscles in the lungs?
Can contracts to constrict (narrow) the airways
Where are goblet cells found in the lungs?
Lining trachea - bronchioles
What is the function of goblet cells in the lungs?
Secrete mucus which traps particles of dust and bacteria which are breathed into the lungs
Where are ciliated epithelial cells found in the lungs?
Lining trachea - bronchioles
What is the function of ciliated epithelial cells in the lungs?
Beat regularly to move mucus up the airways towards the mouth to be removed
Helps keep the airways clear and prevent infections Contain lots of mitochondria to provide energy required to move cilia.
Where is elastin (protein) found in the lungs?
Lining all airways and alveoli
What is the function of elastin in the lungs?
Allows lung tissue to stretch when breathing in and filling up the lungs, recoil when breathing out to help force air out of the lungs
Allows alveoli to return to original shape after exhaling
Where is squamous epithelium found in the lungs?
Lining alveoli
What is the function of squamous epithelium in the lungs?
Gives a short diffusion distance pathway for oxygen and carbon dioxide in the alveoli, cell layer only 0.05-0.3um wide
How does the alveolar epithelium and capillary endothelium being very thin (1 cell thick) increase diffusion?
Shortens diffusion distance of gases from alveoli to blood - only has to diffuse through two cells
How does the large number of alveoli increase diffusion?
Increases surface area for gas exchange
How does the capillaries that surround the alveoli being very narrow (7-10um) increase diffusion?
Red blood cells are slowed down to squeeze through one at a time increasing the time for diffusion
How does the large number of capillaries around alveoli increase diffusion?
Circulation constantly removes oxygenated blood to maintain steep concentration gradient
How does the constant ventilation of air in and out of the lungs increase diffusion?
Ensures concentration of oxygen in alveoli is higher and concentration of carbon dioxide is lower than blood and therefore maintains steep concentration gradient
What happens during inspiration/inhalation?
Diaphragm contracts (moves down)
External intercostal muscles contract pulling ribcage moves up and out
Increases the volume of the thoracic cavity which reduces the air pressure because there is more space
Air moves into the trachea down the pressure gradient (high to low)
Active process - requires energy
What happens during expiration/exhalation?
Diaphragm relaxes (moves up)
External intercostal muscles relax, ribcage moves in and down
Decreases volume of the thoracic cavity which increases the air pressure because there is less space
Air moves out of the trachea down the pressure gradient
Normal expiration (not forced) is a passive process.
(In forced expiration the internal intercostal muscles contract to pull the ribcage in and down even more)
Effects of lungs disease in humans
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What is ventilation rate (breathing rate)?
How many breathes per minute a person takes
What is tidal volume?
the volume within each breathe taken
What does ventilation rate and tidal volume tell you?
Can tell you about how the lungs are functioning
What is residual volume?
The volume of air that remains in the lungs to ensure they never fully deflate (always there)
How do you measure a persons lung function?
By using a spirometer to measure lung function and work out breathing rate, tidal volume and ventilation rate from it
What can a persons health and function of lungs be measured by?
By looking at their forced expiratory volume (FEV₁) and forced vital capacity (FVC)
What is Forced expiratory volume (FEV₁)?
The maximum volume of air that can be breathed out in 1 second
What is Forced vital capacity (FVC)?
The maximum volume of air it is possible to breathe forcefully out of the lungs
What do lung diseases affect?
Both ventilation and gas exchange
What do all diseases reduce?
All lung diseases reduce the rate of gas exchange in alveoli
What does the reduced rate of gas exchange mean for patients?
Less oxygen diffuses into the bloodstream, the body cells receive less oxygen which reduces the rate of aerobic respiration is reduced. So less energy is released, so lung disease patients offer suffer with tiredness or weakness in muscles
What are the two types of lung diseases?
Restrictive disease and obstructive diseases
Both affect ventilation in different ways
Whats affected in restrictive disease?
E.g Fibrosis
Make it difficult to fully breathe in (affects elastic tissue)
Severely reduces FVC as breathing in is difficult but FEV₁ is less affected because breathing out is still normal
Whats affected in obstructive diseases?
E.g Asthma
Make it difficult to breathe out as airways are blocked
FVC and FEV₁ are both much lower than normal
What is tuberculosis (TB) caused by?
- Caused by a bacteria inhaled by droplet infection
- The macrophages build a wall around the bacteria in the alveoli forming small hard lumps called tubercules
- The bacteria remain alive but dormant
- Eventually the infected tissue dies damaging the alveoli. As a result of the immune system response fibrosis also occurs
What are the effects of tuberculosis (TB)?
Reduced rate of gas exchange because:
* Damaged alveoli have a smaller surface area.
* Scar tissue is thicker, so diffusion rate is reduced as diffusion distance between alveoli and blood is increased
* Elasticity is reduced so lungs cannot expand and hold as much air as normal
Tidal volume = decreased
Ventilation rate = increased
What are the symptoms of tuberculosis (TB)?
- A persistent cough (cough up mucus and blood)
- Shortness of breath
- Fatigue
What is pulmonary fibrosis (PF) caused by?
Formation of scar tissue in the lungs after an infection or breathing in substances like asbestos
What are the effects of pulmonary fibrosis (PF)?
Reduced rate of gas exchange because:
* Scar tissue is thicker so diffusion rate is reduced as diffusion distance between alveoli and blood is increased
* Elasticity is reduced so lungs cannot expand and hold as much air as normal
Tidal volume = decreased
Ventilation rate = increased
What are the symptoms of pulmonary fibrosis (PF)?
- Dry cough
- Shortness of breath
- Chest pain
- Fatigue
- Weakness.
What is asthma caused by?
Airways become inflamed due to an allergic reaction to inhaled substances such as pollen or dust
Smooth muscle lining the bronchioles contracts and lots of mucus is produced
What are the effects of asthma?
Reduced rate of gas exchange because:
* Airways constrict severely reducing air flow in and out of the lungs so less 02 diffuses into blood
FEV₁= severely reduced
What are the symptoms of asthma?
- Wheezing
- Tight chest
- Shortness of breath
(Can be relieved by inhalers which cause bronchiole muscle to relax)
What is emphysema caused by?
Disease caused by foreign particles (from smoking or long term exposure to air pollution) being trapped in the alveoli
This causes inflammation, phagocytes arrive and they produce an enzyme which breaks down the elastin in the walls of the alveoli
What are the effects of emphysema?
Reduced rate of gas exchange because:
* Damaged alveoli have a smaller surface area
* Loss of elastin means alveoli cannot recoil as well and less air is expelled
Tidal volume = decreased
Ventilation rate = increased
FEV₁= severely reduced
What are the symptoms of emphysema?
- Shortness of breath
- Wheezing
