Why Is a large surface area to volume ratio important
It allows efficient gass exchange as the surface area available for diffusion is large, so diffusion will be faster
Why do larger organisms need specialised exchange surfaces
Because there surface area to volume ratio is small, simple diffusion across the body surface would be too slow to meet metabolic demands
Which features make an exchange surface efficient
. Large surface area to volume ratio
. Thin surface - short diffusion pathway
. Good blood supply - maintains concentration gradient
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Examples of specialised exchange surfaces in organisms
. Alveoli in lungs
. Gills in fish
. Root hairs in plants - absorption of water and ions
. Intestinal villi (absorption of nutrients)
Describe the structure and function of insect gass exchange
. Have a network of trachea with branch into smaller tracheols that penetrate into body tissue.
. Air enters through spiracles and diffuses directly into cells.
. Some insects use rhythmic abdominal movements to ventillate the tracheal system.
How is water loss minimised in gass exchange
. Spiracles can close to prevent evaporation
. The body surface has a water proof waxy cuticle
What is counter current flow in fish
. Blood flows through the Gills lamellae in the opposite direction to water.
. This maintains steep concentration gradient across the entire Gill, allowing maximum oxygen diffusion into the blood
Describe the structure of fish gills
Gills are made of gill arches with filaments covered in lamellae, which have capillaries for gass exchange
How does gas exchange occur in plants
Through stomata on the lower epidermis of leaves.
. CO² diffuses in for photosynthesis, and O² diffuses out.
. Air spaces in the spongy mysophyll facilitate diffusion
How do gaurd cells controll water loss in plants
Gaurd cells open and close stomata. In dry condtions, they close the pore to reduce water loss
What structural adaptation reduces water loss in xzerophytes
. Thick waxy cuticle to reduce evaporation
. Rolled leaves to trap moist air and reduce gradient
. Hairy leaves to trap water vapour
. Stomata in pits to reduce exposure to air
. Reduced number of stomata
. Small leaf surface area
Physiological adaptations of xerophytes
Stomata open at night to reduce water loss
Describe the role of digestive enzymes in carbohydrate digestion
. Amylase in saliva and pancreas hydrolyses starch to Maltose.
. Maltase, which is membrane bound in the ilium, hydrolyses maltose to glucose
. Sucrase and lactase hydrolyse Sucrose and lactose
Describe protien digestion
. Endopeptidases hydrolyse peptide bonds within proteins. . Exopeptidases hydrolyse external peptide bonds.
. Dipeptidases (membrane bound) hydrolyse dipeptides to amino acids
How are lipids digested and absorbed
. Bile salts emulify lipids into droplets, micelles, to increase surface area. . Lipase from the pancreas hydrolyses tryglicerides into monoglycerides and fatty acids.
. These diffuse into epithelial cells, recombine into tryglicerides, packaged into chylomicrons and enter lacteals (lymphatic vessels)
How is absorption in the ilium maximised
. Villi increase surface area
. Thin epithelium- short diffusion pathway
. Rich blood supply - maintain concentration gradient
. Presence of carrier protiens for active transport and cotransport
Describe the structure of heamaglobin
It’s a globular protien with a quaternary structure, consisting of 4 polypeptide chains each with a heam group that binds to an oxygen
What is loading and unloading of oxygen
Loading occurs in the lungs where pO² is high,unloading occurs in respiring tissue where pO² is low
What factors effect the oxygen dissociation
. pO² - higher pO² effects saturation
. pCO² - higher CO² shifts curve to the right
. PH, temp and 2,3 BGP also effect binding affinity
What is partial pressure
The pressure that a single gas ina mixture would exert if it occupied the whole volume by itself
What is affinity to oxygen
How easily heamaglobin binds to oxygen molecule
What are the Adaptations of organisms to different oxygen demands?
. Animals at high altitudes have haemaglobin with higher affinity for O²
. Active organisms have lower affinity as they have haemaglobin that releases O² more readily
What is the structure and role of the blood vessel artery
. Thick walls
. High pressure
. Small lumen
. Carries blood away from the heart
What is the structure and role of the blood vessel veins
. Thin walls
. Low pressure
. Valves to prevent back flow of blood
. Carries blood towards the heart
