Topic 3 - exchange between organisms and their environment Flashcards
what is surface area to volume ratio?
the relationship between the size of an organsism or structure and its surface area to value ratio plays a significant role in the types of adaptations an organism will have.
what does a larger surface area to volume ratio mean for an organism?
a big surface for exchange of substances, but also there is a smaller distance from the outside of the organisms to the middle of it. simply they can diffuse gases across their surface area.
What does having a small surface area to volume ratio mean for exchange?
there is a further distance for gases to go, and they typically have a higher metabolic rate which demands efficient transport of waste out of cells and reactants into the cells. As a result they have adaptations to make their exchange system more efficient.
what are some adaptations to increase surface-area to volume,e ratio?
Villi and microvilli - absorption of digested food
alveoli and bronchioles - gas exchange
spiracles and tracheoles - gas exchange
gill filaments and lamelllae - gas exchange
thin wide leaves - gas exchange
many capillaries - capillary network
what is breathing?
movement of air into and out of the lungs.
what is respiration?
Chemical reaction to release energy in the form of ATP.
What is gaseous exchange?
diffusion of oxygen from the air in the alveoli into the blood and of carbon dioxide from the blood into the air in the alveoli.
What are the structures of the human gaseous exchange system?
Alveoli, bronchioles, bronchi, trachea and lungs.
what is the process of human inspiration?
the diaphragm contracts and flattens and the external intercostal muscles contract and pull the ribcage up and out.
internal intercostal muscles are relaxing.
pressure in the lungs intitially decreases
lung volume increases
air rushes in.
what is the process of human expiration?
External intercostal and diaphragm (returns to the dome shape) muscles relax
internal intercostal muscles contract and move the rib cage down and in.
Initially air pressure is higher than the outside.
lung volume decreases
air moves out of the lungs
what is pulmonary ventilation?
The total volume of air that is moved into the lungs during one minute.
pulmonary ventilation = tidal volume x ventilation rate
what is the process of gas exchange in the alveoli?
- once the gases are in the alveoli, it exchanges between the epithelium and the blood.
- alveoli are tiny air sacks, and there are 300 million in each human lung creating a large surface area to volume ratio for gas exchange.
- the alveoli epithelium cells ar even thin, to minimise diffusion distance
- each alveolus is surrounded by a network of capillaries to remove exchange gases and therefore maintains a concentration gradient.
why do terrestrial insects need an exchange system?
they have a water resistant exoskeleton
What is the insect tracheal system?
- Gas exchange in insects involves a tracheal system.
- Spiracles are round valve like openings, oxygen and carbon dioxide enter and leave via the spiracles. The trachea attach to these openings.
- The trachea is a network of internal tubes.
- the trachea tubes have rings within them to strength m the tubes and to keep them open.
- the trachea branch into smaller tubes, deeper into the abdomen of the insect called tracheoles. These extend throughout all the tissues in the insect to deliver oxygen to all respiring cells.
What are the three methods of moving gases in the tracheal system?
- Gas can exchange by diffusion, as when cells respire, they use up oxygen and produce carbon dioxide, creating a concentration gradients from the tracheoles to the atmosphere.
- The second method of gas exchange is mass transport, in which an insect contracts and relaxes their abdominal muscles to move gases on mass.
- When the insect is in flight the muscle cells start to respire anaerobically to produce lactate. This lowers the water potential of the cells, and therefore water moves from the tracheoles into the cells by osmosis. This decreases the volume in the tracheoles and as a result for air from the atmosphere is drawn in.
What are the adaptation of efficient diffusion of terrestrial insects?
- Large number of fine tracheoles - large surface area to volume ratio
- Walls of tracheoles are thin and short distance between spiracles and tracheoles - short diffusion pathway.
- Use of oxygen and production of carbon dioxide sets up steep diffusion gradients.
How do terrestrial insects limit water loss?
- Insects have a small surface area to volume ratio where water can evaporate from.
- Insects have a waterproof exoskeleton.
- Spiracles where gases enter and water can evaporate from can open and close to reduce water loss.
Why do fish have to maintain a concentration gradient?
There is 30x less oxygen in water than there is in the air.
What is the fish gill anatomy?
- There are four layers of gills on both sides of the head.
- The gills are made up of stacks of gill filaments.
- Each gill filament is covered in gill lamellae, positioned at right angles to the filament.
- This creates a rage surface area to volume ratio.
- when fish open their mouth, water rushes in and over the gills and then out through a hole in the sides of their head.
- network of capillary’s in every lamellae creating short diffusion distance.
What is the countercurrent mechanism?
Ensures constant concentration gradient.
- this is when water flows over the gills in the opposite direction to the flow of blood in the capillaries.
- countercurrent flow ensures that equilibrium is not reached.
- this ensures that a diffusion gradient is maintained across the entire length of the gill lamellae.
What are the structures in the leaf?
Palisade mesophyll
Spongy mesophyll
Stomata
What are the structures in the leaf?
Palisade mesophyll
Spongy mesophyll
Stomata
What is gas exchange in the stomata?
– Oxygen diffuses out of the stomata.
– Carbon dioxide diffuses in through the stomata.
– To reduce water loss by evaporation stomata close at night when photosynthesis wouldn’t be occurring.
What do xerophytic plants have the allows them to be adapted to survive?
They have structural features to enable efficient gas exchange to occur whilst also limiting the water loss. Due to the fact there is very minimal water available.
- leaves are curled to trap moisture and increase local humidity
- stomata in pits to trap moisture and increase local humidity
- tiny hairs to trap moisture and increase humidity
- thicker cuticle to reduce evaporation
- longer route network to reach more water
What are the adaptations for digestion and absorption?
During digestion, large biological molecules are hydrolysed into smaller molecules that can be absorbed across cell membranes.
What are the three biological molecules you need to know the digestion of?
Carbohydrates
Lipids
Proteins.
How are carbohydrates digested?
Digestion begins in the mouth, continues in the duodenum and is completed in the ileum.
There are two enzymes used to hydrolyse carbohydrates into monosaccharides: amylases and membrane bound disacharidases.
Amylase is produced by the pancreas and salivary glands. it hydrolyses polysaccharides into the disaccharide maltose by hydrolysing this glycosidic bonds.
Sucrose and lactase membrane bound enzymes that hydrolase sucrose and lactose into monosaccharides.
How are proteins digested?
Proteins are large polymer molecules that can be hydrolysed by three enzymes:
1. Endopeptidases – hydrolyse peptide bonds between amino acids in the middle of a polymer chain.
2. Exopeptidases – hydrolyse peptide bonds between amino acids at the end of a polymer chain.
3. Membrane bound dipeptidases – hydrolyse peptide bonds between two amino acids.
Protein digestion starts in the stomach continues in the duodenum and is fully digested in the ileum.
How are lipids digested?
– Lipids are digested by lipase and the action of bile salts.
– Lipase is produced in the pancreas and it can hydrolyse the ester bond in triglycerides to form the monoglycerides and fatty acids.
– Bile salts are produced in the liver and can emulsify lipids to form tiny droplets, micelles. This increases the surface area for lipase to act on.
What are the two stages in digesting lipids?
Physical - emulsification & micelle formation. Lipids are coated in bile salts to create an emulsion. many small droplets of lipids provide a larger surface area to enable the faster hydrolysis action by lipase.
Chemical - lipase. Lipase hydrolyses lipids into glycerol and fatty acids.
What is micelle?
Vehicles formed of the fatty acids, glycerol monoglycerides and bile salts.
What happens in lipids absorption?
- Lipids are digested into monoglycerides and fatty acids by the action of lipase and bile salts.
– These are tiny structures called micelles.
– When the micelles encounter the ileum epithelial cells due to the nonpolar nature of the fatty acids and the monoglycerides, they can simply diffuse across the cell surface membrane to enter the epithelial cells.
– once in the cell, they will be modified back into triglycerides inside of the endoplasmic reticulum and the Golgi body.
What is absorption in mammals like?
- In mammals, the products of digestion are absorbed across the cells lining the ileum.
- The ileum war is covered in villi which have walls surrounded by a network of capillaries and epithelial cells have even smaller microvilli.
- These features maximise absorption by increasing the surface area to volume ratio, decreasing the diffusion distance and maintaining a concentration gradient.
How are monosaccharides and amino acids absorbed?
To absorb glucose and amino acids from the lumen to the gut there must be a higher concentration in the lumen compared to the epithelial cells.
BUT
There is usually more in epithelial cells.
That is why active transport and co transport required.
What is haemoglobin?
Haemoglobin of groups of proteins found in different organisms. Haemoglobin is a protein with a quaternary structure (4 polypeptide chains). Haemoglobin and red blood cells transport oxygen.
What is the oxyhaemoglobin disassociation curve?
Oxygen is loaded in regions with a high par pressure of oxygen and is unloaded in regions of low partial pressure of oxygen. This is shown on the oxyhaemoglobin disassociation curve.
What is cooperative binding?
The cooperative nature of oxygen binding to haemoglobin is due to the haemoglobin changing shape when the first oxygen binds. This then makes it easier for the other oxygen to bind.
What is the Bohr effect?
The Bohr effect is when a high carbon dioxide concentration causes the oxyhaemoglobin curve to shift to the right. the affinity for oxygen decreases because that acidic carbon dioxide changes the shape of haemoglobin slightly.
– Low partial pressure of carbon dioxide is in the alveoli. Curve shift left increased affinity and therefore uploads more oxygen.
– High partial pressure of carbon dioxide at respiring tissues. Curve shifts to the right decreased affinity and therefore unload more oxygen.
What are the key blood vessels?
Vena cava aorta pulmonary artery and pulmonary vein.
Renal artery and renal vein (kidneys)
Pulmonary artery and pulmonary vein (lungs)
These major blood vessels are connected within the circulatory system via the arteries, arterioles, capillaries and veins.
\ what are the features of the cardiac muscle?
This walls of the heart have a thick muscular layer. This muscle is called cardiac muscle and it has unique properties: it is myogenic meaning it can contract and relax without nervous or hormonal stimulation.
It never fatigues as long as it has a supply of oxygen.
What are the coronary arteries?
- Supply the heart with oxygenated blood.
- A brunch from the aorta.
– If they become blocked cardiac muscle won’t receive oxygen therefore will not be able to respire and the cells will die. This result in my myocardial infarction.
What is the structure of an artery and why is this helpful?
Thicker than vein so that construction and dilation can occur to control volume of blood.
Thicker than veins to maintain blood pressure, the walls can stretch and recoil t in response to the heartbeat.
Thicker wall veins to help prevent the vessels bursting due to the high-pressure.
What are the structural properties of veins and why is it important?
– relatively thin so cannot control the blood flow.
– Relatively thin as the pressure is much lower.
– Thin as the pressure is much much lower so there is low risk of bursting. The thinness means the vessels are easily flattened which helps the flow of blood up to the heart.
– They also have valves.
What is the structure of the capillaries?
Capillaries form capillary beds, exchange surfaces which are many branched capillaries. These all have a narrow diameter test to slow blood flow. Red blood cells can only just fit through and are squashed against the rules and this maximises diffusion.
What are the three stages the cardiac cyclist split into?
Diastole atrial sytole and ventricular systole
What is the diastole stage of the cardiac cycle?
– The atria and ventricular muscles are relaxed.
– This is when blood will enter the atria via the vena cava and pulmonary vein.
– The blood flowing into the atria increases the pressure within the atria.
What is atrial systole?
– The atrium muscular wall contract increasing the pressure further. this causes the atrioventricular valves to open and blood flow into the ventricles.
– The ventricular muscular walls are relaxed.
What ventricular systole?
– After a short delay the ventricle muscular walls contract, increasing the pressure beyond that of the atria. This causes the atrial ventricular valves to close and the semi-lunar valves to open.
– The blood is pushed out of the ventricles into the arteries.
What is tissue fluid?
Fluid that contains water, glucose, amino acid, fatty acid ions and oxygen which bathes the tissue.
How is tissue fluid formed?
Capillary have small gaps in the walls so that liquid and small molecules can be forced out.
As blood enters the capillaries from arterioles, the smaller diameter results in a high hydrostatic pressure so water, glucose, amino acids, fatty acids, ions and oxygen are forced out. This is known as ultrafiltration.
What is lymph?
The rest of the tissue fluid is absorbed into the lymphatic system and eventually drains back into the bloodstream near the heart.
What is transpiration?
The loss of water vapour from the stomata by evaporation.
What are the four key factors that affect transpiration and explain?
Light – more light causes more smarter to open = larger surface area for evaporation
Temperature – more heat means more kinetic energy so faster moving molecules and therefore more evaporation.
Wind – positive correlation more wind will blow away humid air containing water vapour therefore maintaining the water potential gradient
Humidity – negative correlation more water vapour in the air will make the water potential more positive outside of the leaf therefore reduces the water potential gradient.
What is cohesion in terms of water moving up the xylem?
– Water is a dipolar molecule (negative oxygen and positive hydrogens).
– This enables hydrogen bonds to form between the hydrogen and oxygen of different water molecules.
– This creates cohesion between water molecules – they stick togethe. Therefore water travels up the xylem as a continuous water column.
What is adhesion in terms of water moving up plant roots?
Adhesion of water is when water sticks to other molecules. Water adhered to the Xylem walls.
- The narrow weather xylene the bigger the impact of capillary.
What is root pressure in terms of water travelling up a plant root?
As water moves into the roots by osmosis, it increases the volume of liquid inside the root and therefore the pressure inside the root increases. This is known as root pressure.
This increased in pressure in the roots forces water above it upwards (positive pressure).
How does water move up the xylem?
- Water vapour evaporates out of the stomata on the leaves. This loss in water volume creates a lower pressure.
- When this water loss is lost by transpiration more water is pulled up the xylem to replace it.
- Due to the hydrogen bonds between water molecules they are cohesive. This creates a column of water within the xylem.
- Water molecules also adhere to the walls of the xylem. This helps to pull the water column upwards.
- This column of water is pulled up the xylem it creates tension, pulling the xylem in to become narrower.
What does the phloem tissue contain?
Sieve tube elements - living cells contain no nucleus contain a few organelles.
Companion cells - provide ATP required for active transport of organic substances.
Explain the source to sink explanation
Sucrose lowers the water potential of the cell.
Water enters by osmosis.
Respiring cell is using up sucrose and therefore it has a more positive water potential.
Water leaves the sink cell by osmosis.
This increases the hydrostatic pressure in the source cell.
This decreases the hydrostatic pressure in the sink cell.
The source cell has a higher hydrostatic pressure than the sink cell, so the solution is forced towards the sink cell via the phloem.
